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-rw-r--r--compiler/rustc_target/src/spec/aarch64_kmc_solid_asp3.rs19
-rw-r--r--compiler/rustc_target/src/spec/armv7a_kmc_solid_asp3_eabi.rs19
-rw-r--r--compiler/rustc_target/src/spec/armv7a_kmc_solid_asp3_eabihf.rs19
-rw-r--r--compiler/rustc_target/src/spec/mod.rs5
-rw-r--r--compiler/rustc_target/src/spec/solid_base.rs12
-rw-r--r--library/panic_abort/src/lib.rs1
-rw-r--r--library/panic_unwind/src/lib.rs1
-rw-r--r--library/std/build.rs1
-rw-r--r--library/std/src/os/mod.rs2
-rw-r--r--library/std/src/os/solid/ffi.rs41
-rw-r--r--library/std/src/os/solid/io.rs113
-rw-r--r--library/std/src/os/solid/mod.rs17
-rw-r--r--library/std/src/sys/itron/abi.rs155
-rw-r--r--library/std/src/sys/itron/condvar.rs294
-rw-r--r--library/std/src/sys/itron/error.rs159
-rw-r--r--library/std/src/sys/itron/mutex.rs183
-rw-r--r--library/std/src/sys/itron/spin.rs164
-rw-r--r--library/std/src/sys/itron/task.rs44
-rw-r--r--library/std/src/sys/itron/thread.rs352
-rw-r--r--library/std/src/sys/itron/time.rs123
-rw-r--r--library/std/src/sys/itron/time/tests.rs33
-rw-r--r--library/std/src/sys/mod.rs3
-rw-r--r--library/std/src/sys/solid/abi/fs.rs53
-rw-r--r--library/std/src/sys/solid/abi/mod.rs92
-rw-r--r--library/std/src/sys/solid/abi/sockets.rs274
-rw-r--r--library/std/src/sys/solid/alloc.rs32
-rw-r--r--library/std/src/sys/solid/env.rs9
-rw-r--r--library/std/src/sys/solid/error.rs55
-rw-r--r--library/std/src/sys/solid/fs.rs529
-rw-r--r--library/std/src/sys/solid/io.rs77
-rw-r--r--library/std/src/sys/solid/memchr.rs21
-rw-r--r--library/std/src/sys/solid/mod.rs96
-rw-r--r--library/std/src/sys/solid/net.rs469
-rw-r--r--library/std/src/sys/solid/os.rs200
-rw-r--r--library/std/src/sys/solid/path.rs19
-rw-r--r--library/std/src/sys/solid/rwlock.rs92
-rw-r--r--library/std/src/sys/solid/stdio.rs80
-rw-r--r--library/std/src/sys/solid/thread_local_dtor.rs50
-rw-r--r--library/std/src/sys/solid/thread_local_key.rs26
-rw-r--r--library/std/src/sys/solid/time.rs56
-rw-r--r--library/std/src/time.rs2
-rw-r--r--library/unwind/src/lib.rs1
-rw-r--r--src/doc/rustc/src/SUMMARY.md1
-rw-r--r--src/doc/rustc/src/platform-support.md3
-rw-r--r--src/doc/rustc/src/platform-support/kmc-solid.md65
45 files changed, 4062 insertions, 0 deletions
diff --git a/compiler/rustc_target/src/spec/aarch64_kmc_solid_asp3.rs b/compiler/rustc_target/src/spec/aarch64_kmc_solid_asp3.rs
new file mode 100644
index 00000000000..61e3be617e9
--- /dev/null
+++ b/compiler/rustc_target/src/spec/aarch64_kmc_solid_asp3.rs
@@ -0,0 +1,19 @@
+use super::{RelocModel, Target, TargetOptions};
+
+pub fn target() -> Target {
+    let base = super::solid_base::opts("asp3");
+    Target {
+        llvm_target: "aarch64-unknown-none".to_string(),
+        pointer_width: 64,
+        data_layout: "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128".to_string(),
+        arch: "aarch64".to_string(),
+        options: TargetOptions {
+            linker: Some("aarch64-kmc-elf-gcc".to_owned()),
+            features: "+neon,+fp-armv8".to_string(),
+            relocation_model: RelocModel::Static,
+            disable_redzone: true,
+            max_atomic_width: Some(128),
+            ..base
+        },
+    }
+}
diff --git a/compiler/rustc_target/src/spec/armv7a_kmc_solid_asp3_eabi.rs b/compiler/rustc_target/src/spec/armv7a_kmc_solid_asp3_eabi.rs
new file mode 100644
index 00000000000..344c48022b2
--- /dev/null
+++ b/compiler/rustc_target/src/spec/armv7a_kmc_solid_asp3_eabi.rs
@@ -0,0 +1,19 @@
+use super::{RelocModel, Target, TargetOptions};
+
+pub fn target() -> Target {
+    let base = super::solid_base::opts("asp3");
+    Target {
+        llvm_target: "armv7a-none-eabi".to_string(),
+        pointer_width: 32,
+        data_layout: "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64".to_string(),
+        arch: "arm".to_string(),
+        options: TargetOptions {
+            linker: Some("arm-kmc-eabi-gcc".to_owned()),
+            features: "+v7,+soft-float,+thumb2,-neon".to_string(),
+            relocation_model: RelocModel::Static,
+            disable_redzone: true,
+            max_atomic_width: Some(64),
+            ..base
+        },
+    }
+}
diff --git a/compiler/rustc_target/src/spec/armv7a_kmc_solid_asp3_eabihf.rs b/compiler/rustc_target/src/spec/armv7a_kmc_solid_asp3_eabihf.rs
new file mode 100644
index 00000000000..375502478fe
--- /dev/null
+++ b/compiler/rustc_target/src/spec/armv7a_kmc_solid_asp3_eabihf.rs
@@ -0,0 +1,19 @@
+use super::{RelocModel, Target, TargetOptions};
+
+pub fn target() -> Target {
+    let base = super::solid_base::opts("asp3");
+    Target {
+        llvm_target: "armv7a-none-eabihf".to_string(),
+        pointer_width: 32,
+        data_layout: "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64".to_string(),
+        arch: "arm".to_string(),
+        options: TargetOptions {
+            linker: Some("arm-kmc-eabi-gcc".to_owned()),
+            features: "+v7,+vfp3,-d32,+thumb2,-neon".to_string(),
+            relocation_model: RelocModel::Static,
+            disable_redzone: true,
+            max_atomic_width: Some(64),
+            ..base
+        },
+    }
+}
diff --git a/compiler/rustc_target/src/spec/mod.rs b/compiler/rustc_target/src/spec/mod.rs
index c947721d63d..d18e5823cb8 100644
--- a/compiler/rustc_target/src/spec/mod.rs
+++ b/compiler/rustc_target/src/spec/mod.rs
@@ -75,6 +75,7 @@ mod netbsd_base;
 mod openbsd_base;
 mod redox_base;
 mod solaris_base;
+mod solid_base;
 mod thumb_base;
 mod uefi_msvc_base;
 mod vxworks_base;
@@ -932,6 +933,10 @@ supported_targets! {
     ("powerpc-wrs-vxworks-spe", powerpc_wrs_vxworks_spe),
     ("powerpc64-wrs-vxworks", powerpc64_wrs_vxworks),
 
+    ("aarch64-kmc-solid_asp3", aarch64_kmc_solid_asp3),
+    ("armv7a-kmc-solid_asp3-eabi", armv7a_kmc_solid_asp3_eabi),
+    ("armv7a-kmc-solid_asp3-eabihf", armv7a_kmc_solid_asp3_eabihf),
+
     ("mipsel-sony-psp", mipsel_sony_psp),
     ("mipsel-unknown-none", mipsel_unknown_none),
     ("thumbv4t-none-eabi", thumbv4t_none_eabi),
diff --git a/compiler/rustc_target/src/spec/solid_base.rs b/compiler/rustc_target/src/spec/solid_base.rs
new file mode 100644
index 00000000000..c6a279d92e8
--- /dev/null
+++ b/compiler/rustc_target/src/spec/solid_base.rs
@@ -0,0 +1,12 @@
+use super::FramePointer;
+use crate::spec::TargetOptions;
+
+pub fn opts(kernel: &str) -> TargetOptions {
+    TargetOptions {
+        os: format!("solid_{}", kernel),
+        vendor: "kmc".to_string(),
+        frame_pointer: FramePointer::NonLeaf,
+        has_elf_tls: true,
+        ..Default::default()
+    }
+}
diff --git a/library/panic_abort/src/lib.rs b/library/panic_abort/src/lib.rs
index 4580f9a7758..ac75ce7f221 100644
--- a/library/panic_abort/src/lib.rs
+++ b/library/panic_abort/src/lib.rs
@@ -44,6 +44,7 @@ pub unsafe extern "C-unwind" fn __rust_start_panic(_payload: *mut &mut dyn BoxMe
                 libc::abort();
             }
         } else if #[cfg(any(target_os = "hermit",
+                            target_os = "solid_asp3",
                             all(target_vendor = "fortanix", target_env = "sgx")
         ))] {
             unsafe fn abort() -> ! {
diff --git a/library/panic_unwind/src/lib.rs b/library/panic_unwind/src/lib.rs
index ac7d8c18e3e..b5d0ca2572c 100644
--- a/library/panic_unwind/src/lib.rs
+++ b/library/panic_unwind/src/lib.rs
@@ -45,6 +45,7 @@ cfg_if::cfg_if! {
     } else if #[cfg(any(
         all(target_family = "windows", target_env = "gnu"),
         target_os = "psp",
+        target_os = "solid_asp3",
         all(target_family = "unix", not(target_os = "espidf")),
         all(target_vendor = "fortanix", target_env = "sgx"),
     ))] {
diff --git a/library/std/build.rs b/library/std/build.rs
index 726157c1f1a..cc7184d57f1 100644
--- a/library/std/build.rs
+++ b/library/std/build.rs
@@ -27,6 +27,7 @@ fn main() {
         || target.contains("wasm32")
         || target.contains("asmjs")
         || target.contains("espidf")
+        || target.contains("solid")
     {
         // These platforms don't have any special requirements.
     } else {
diff --git a/library/std/src/os/mod.rs b/library/std/src/os/mod.rs
index 069a5376a44..90c30313dbb 100644
--- a/library/std/src/os/mod.rs
+++ b/library/std/src/os/mod.rs
@@ -138,6 +138,8 @@ pub mod redox;
 #[cfg(target_os = "solaris")]
 pub mod solaris;
 
+#[cfg(target_os = "solid_asp3")]
+pub mod solid;
 #[cfg(target_os = "vxworks")]
 pub mod vxworks;
 
diff --git a/library/std/src/os/solid/ffi.rs b/library/std/src/os/solid/ffi.rs
new file mode 100644
index 00000000000..aaa2070a6ab
--- /dev/null
+++ b/library/std/src/os/solid/ffi.rs
@@ -0,0 +1,41 @@
+//! SOLID-specific extension to the primitives in the `std::ffi` module
+//!
+//! # Examples
+//!
+//! ```
+//! use std::ffi::OsString;
+//! use std::os::solid::ffi::OsStringExt;
+//!
+//! let bytes = b"foo".to_vec();
+//!
+//! // OsStringExt::from_vec
+//! let os_string = OsString::from_vec(bytes);
+//! assert_eq!(os_string.to_str(), Some("foo"));
+//!
+//! // OsStringExt::into_vec
+//! let bytes = os_string.into_vec();
+//! assert_eq!(bytes, b"foo");
+//! ```
+//!
+//! ```
+//! use std::ffi::OsStr;
+//! use std::os::solid::ffi::OsStrExt;
+//!
+//! let bytes = b"foo";
+//!
+//! // OsStrExt::from_bytes
+//! let os_str = OsStr::from_bytes(bytes);
+//! assert_eq!(os_str.to_str(), Some("foo"));
+//!
+//! // OsStrExt::as_bytes
+//! let bytes = os_str.as_bytes();
+//! assert_eq!(bytes, b"foo");
+//! ```
+
+#![stable(feature = "rust1", since = "1.0.0")]
+
+#[path = "../unix/ffi/os_str.rs"]
+mod os_str;
+
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use self::os_str::{OsStrExt, OsStringExt};
diff --git a/library/std/src/os/solid/io.rs b/library/std/src/os/solid/io.rs
new file mode 100644
index 00000000000..33cc5a015b5
--- /dev/null
+++ b/library/std/src/os/solid/io.rs
@@ -0,0 +1,113 @@
+//! SOLID-specific extensions to general I/O primitives
+
+#![deny(unsafe_op_in_unsafe_fn)]
+#![unstable(feature = "solid_ext", issue = "none")]
+
+use crate::net;
+use crate::sys;
+use crate::sys_common::{self, AsInner, FromInner, IntoInner};
+
+/// Raw file descriptors.
+pub type RawFd = i32;
+
+/// A trait to extract the raw SOLID Sockets file descriptor from an underlying
+/// object.
+pub trait AsRawFd {
+    /// Extracts the raw file descriptor.
+    ///
+    /// This method does **not** pass ownership of the raw file descriptor
+    /// to the caller. The descriptor is only guaranteed to be valid while
+    /// the original object has not yet been destroyed.
+    fn as_raw_fd(&self) -> RawFd;
+}
+
+/// A trait to express the ability to construct an object from a raw file
+/// descriptor.
+pub trait FromRawFd {
+    /// Constructs a new instance of `Self` from the given raw file
+    /// descriptor.
+    ///
+    /// This function **consumes ownership** of the specified file
+    /// descriptor. The returned object will take responsibility for closing
+    /// it when the object goes out of scope.
+    ///
+    /// This function is also unsafe as the primitives currently returned
+    /// have the contract that they are the sole owner of the file
+    /// descriptor they are wrapping. Usage of this function could
+    /// accidentally allow violating this contract which can cause memory
+    /// unsafety in code that relies on it being true.
+    unsafe fn from_raw_fd(fd: RawFd) -> Self;
+}
+
+/// A trait to express the ability to consume an object and acquire ownership of
+/// its raw file descriptor.
+pub trait IntoRawFd {
+    /// Consumes this object, returning the raw underlying file descriptor.
+    ///
+    /// This function **transfers ownership** of the underlying file descriptor
+    /// to the caller. Callers are then the unique owners of the file descriptor
+    /// and must close the descriptor once it's no longer needed.
+    fn into_raw_fd(self) -> RawFd;
+}
+
+#[stable(feature = "raw_fd_reflexive_traits", since = "1.48.0")]
+impl AsRawFd for RawFd {
+    #[inline]
+    fn as_raw_fd(&self) -> RawFd {
+        *self
+    }
+}
+#[stable(feature = "raw_fd_reflexive_traits", since = "1.48.0")]
+impl IntoRawFd for RawFd {
+    #[inline]
+    fn into_raw_fd(self) -> RawFd {
+        self
+    }
+}
+#[stable(feature = "raw_fd_reflexive_traits", since = "1.48.0")]
+impl FromRawFd for RawFd {
+    #[inline]
+    unsafe fn from_raw_fd(fd: RawFd) -> RawFd {
+        fd
+    }
+}
+
+macro_rules! impl_as_raw_fd {
+    ($($t:ident)*) => {$(
+        #[stable(feature = "rust1", since = "1.0.0")]
+        impl AsRawFd for net::$t {
+            #[inline]
+            fn as_raw_fd(&self) -> RawFd {
+                *self.as_inner().socket().as_inner()
+            }
+        }
+    )*};
+}
+impl_as_raw_fd! { TcpStream TcpListener UdpSocket }
+
+macro_rules! impl_from_raw_fd {
+    ($($t:ident)*) => {$(
+        #[stable(feature = "from_raw_os", since = "1.1.0")]
+        impl FromRawFd for net::$t {
+            #[inline]
+            unsafe fn from_raw_fd(fd: RawFd) -> net::$t {
+                let socket = sys::net::Socket::from_inner(fd);
+                net::$t::from_inner(sys_common::net::$t::from_inner(socket))
+            }
+        }
+    )*};
+}
+impl_from_raw_fd! { TcpStream TcpListener UdpSocket }
+
+macro_rules! impl_into_raw_fd {
+    ($($t:ident)*) => {$(
+        #[stable(feature = "into_raw_os", since = "1.4.0")]
+        impl IntoRawFd for net::$t {
+            #[inline]
+            fn into_raw_fd(self) -> RawFd {
+                self.into_inner().into_socket().into_inner()
+            }
+        }
+    )*};
+}
+impl_into_raw_fd! { TcpStream TcpListener UdpSocket }
diff --git a/library/std/src/os/solid/mod.rs b/library/std/src/os/solid/mod.rs
new file mode 100644
index 00000000000..4328ba7c340
--- /dev/null
+++ b/library/std/src/os/solid/mod.rs
@@ -0,0 +1,17 @@
+#![stable(feature = "rust1", since = "1.0.0")]
+
+pub mod ffi;
+pub mod io;
+
+/// A prelude for conveniently writing platform-specific code.
+///
+/// Includes all extension traits, and some important type definitions.
+#[stable(feature = "rust1", since = "1.0.0")]
+pub mod prelude {
+    #[doc(no_inline)]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub use super::ffi::{OsStrExt, OsStringExt};
+    #[doc(no_inline)]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub use super::io::{AsRawFd, FromRawFd, IntoRawFd, RawFd};
+}
diff --git a/library/std/src/sys/itron/abi.rs b/library/std/src/sys/itron/abi.rs
new file mode 100644
index 00000000000..f99ee4fa897
--- /dev/null
+++ b/library/std/src/sys/itron/abi.rs
@@ -0,0 +1,155 @@
+//! ABI for μITRON derivatives
+pub type int_t = crate::os::raw::c_int;
+pub type uint_t = crate::os::raw::c_uint;
+pub type bool_t = int_t;
+
+/// Kernel object ID
+pub type ID = int_t;
+
+/// The current task.
+pub const TSK_SELF: ID = 0;
+
+/// Relative time
+pub type RELTIM = u32;
+
+/// Timeout (a valid `RELTIM` value or `TMO_FEVR`)
+pub type TMO = u32;
+
+/// The infinite timeout value
+pub const TMO_FEVR: TMO = TMO::MAX;
+
+/// The maximum valid value of `RELTIM`
+pub const TMAX_RELTIM: RELTIM = 4_000_000_000;
+
+/// System time
+pub type SYSTIM = u64;
+
+/// Error code type
+pub type ER = int_t;
+
+/// Error code type, `ID` on success
+pub type ER_ID = int_t;
+
+/// Task or interrupt priority
+pub type PRI = int_t;
+
+/// The special value of `PRI` representing the current task's priority.
+pub const TPRI_SELF: PRI = 0;
+
+/// Object attributes
+pub type ATR = uint_t;
+
+/// Use the priority inheritance protocol
+#[cfg(target_os = "solid_asp3")]
+pub const TA_INHERIT: ATR = 0x02;
+
+/// Activate the task on creation
+pub const TA_ACT: ATR = 0x01;
+
+/// The maximum count of a semaphore
+pub const TMAX_MAXSEM: uint_t = uint_t::MAX;
+
+/// Callback parameter
+pub type EXINF = isize;
+
+/// Task entrypoint
+pub type TASK = Option<unsafe extern "C" fn(EXINF)>;
+
+// Error codes
+pub const E_OK: ER = 0;
+pub const E_SYS: ER = -5;
+pub const E_NOSPT: ER = -9;
+pub const E_RSFN: ER = -10;
+pub const E_RSATR: ER = -11;
+pub const E_PAR: ER = -17;
+pub const E_ID: ER = -18;
+pub const E_CTX: ER = -25;
+pub const E_MACV: ER = -26;
+pub const E_OACV: ER = -27;
+pub const E_ILUSE: ER = -28;
+pub const E_NOMEM: ER = -33;
+pub const E_NOID: ER = -34;
+pub const E_NORES: ER = -35;
+pub const E_OBJ: ER = -41;
+pub const E_NOEXS: ER = -42;
+pub const E_QOVR: ER = -43;
+pub const E_RLWAI: ER = -49;
+pub const E_TMOUT: ER = -50;
+pub const E_DLT: ER = -51;
+pub const E_CLS: ER = -52;
+pub const E_RASTER: ER = -53;
+pub const E_WBLK: ER = -57;
+pub const E_BOVR: ER = -58;
+pub const E_COMM: ER = -65;
+
+#[derive(Clone, Copy)]
+#[repr(C)]
+pub struct T_CSEM {
+    pub sematr: ATR,
+    pub isemcnt: uint_t,
+    pub maxsem: uint_t,
+}
+
+#[derive(Clone, Copy)]
+#[repr(C)]
+pub struct T_CMTX {
+    pub mtxatr: ATR,
+    pub ceilpri: PRI,
+}
+
+#[derive(Clone, Copy)]
+#[repr(C)]
+pub struct T_CTSK {
+    pub tskatr: ATR,
+    pub exinf: EXINF,
+    pub task: TASK,
+    pub itskpri: PRI,
+    pub stksz: usize,
+    pub stk: *mut u8,
+}
+
+extern "C" {
+    #[link_name = "__asp3_acre_tsk"]
+    pub fn acre_tsk(pk_ctsk: *const T_CTSK) -> ER_ID;
+    #[link_name = "__asp3_get_tid"]
+    pub fn get_tid(p_tskid: *mut ID) -> ER;
+    #[link_name = "__asp3_dly_tsk"]
+    pub fn dly_tsk(dlytim: RELTIM) -> ER;
+    #[link_name = "__asp3_ter_tsk"]
+    pub fn ter_tsk(tskid: ID) -> ER;
+    #[link_name = "__asp3_del_tsk"]
+    pub fn del_tsk(tskid: ID) -> ER;
+    #[link_name = "__asp3_get_pri"]
+    pub fn get_pri(tskid: ID, p_tskpri: *mut PRI) -> ER;
+    #[link_name = "__asp3_rot_rdq"]
+    pub fn rot_rdq(tskpri: PRI) -> ER;
+    #[link_name = "__asp3_slp_tsk"]
+    pub fn slp_tsk() -> ER;
+    #[link_name = "__asp3_tslp_tsk"]
+    pub fn tslp_tsk(tmout: TMO) -> ER;
+    #[link_name = "__asp3_wup_tsk"]
+    pub fn wup_tsk(tskid: ID) -> ER;
+    #[link_name = "__asp3_unl_cpu"]
+    pub fn unl_cpu() -> ER;
+    #[link_name = "__asp3_dis_dsp"]
+    pub fn dis_dsp() -> ER;
+    #[link_name = "__asp3_ena_dsp"]
+    pub fn ena_dsp() -> ER;
+    #[link_name = "__asp3_sns_dsp"]
+    pub fn sns_dsp() -> bool_t;
+    #[link_name = "__asp3_get_tim"]
+    pub fn get_tim(p_systim: *mut SYSTIM) -> ER;
+    #[link_name = "__asp3_acre_mtx"]
+    pub fn acre_mtx(pk_cmtx: *const T_CMTX) -> ER_ID;
+    #[link_name = "__asp3_del_mtx"]
+    pub fn del_mtx(tskid: ID) -> ER;
+    #[link_name = "__asp3_loc_mtx"]
+    pub fn loc_mtx(mtxid: ID) -> ER;
+    #[link_name = "__asp3_ploc_mtx"]
+    pub fn ploc_mtx(mtxid: ID) -> ER;
+    #[link_name = "__asp3_tloc_mtx"]
+    pub fn tloc_mtx(mtxid: ID, tmout: TMO) -> ER;
+    #[link_name = "__asp3_unl_mtx"]
+    pub fn unl_mtx(mtxid: ID) -> ER;
+    pub fn exd_tsk() -> ER;
+}
diff --git a/library/std/src/sys/itron/condvar.rs b/library/std/src/sys/itron/condvar.rs
new file mode 100644
index 00000000000..dac4b8abfc4
--- /dev/null
+++ b/library/std/src/sys/itron/condvar.rs
@@ -0,0 +1,294 @@
+//! POSIX conditional variable implementation based on user-space wait queues.
+use super::{abi, error::expect_success_aborting, spin::SpinMutex, task, time::with_tmos_strong};
+use crate::{mem::replace, ptr::NonNull, sys::mutex::Mutex, time::Duration};
+
+// The implementation is inspired by the queue-based implementation shown in
+// Andrew D. Birrell's paper "Implementing Condition Variables with Semaphores"
+
+pub struct Condvar {
+    waiters: SpinMutex<waiter_queue::WaiterQueue>,
+}
+
+unsafe impl Send for Condvar {}
+unsafe impl Sync for Condvar {}
+
+pub type MovableCondvar = Condvar;
+
+impl Condvar {
+    pub const fn new() -> Condvar {
+        Condvar { waiters: SpinMutex::new(waiter_queue::WaiterQueue::new()) }
+    }
+
+    pub unsafe fn init(&mut self) {}
+
+    pub unsafe fn notify_one(&self) {
+        self.waiters.with_locked(|waiters| {
+            if let Some(task) = waiters.pop_front() {
+                // Unpark the task
+                match unsafe { abi::wup_tsk(task) } {
+                    // The task already has a token.
+                    abi::E_QOVR => {}
+                    // Can't undo the effect; abort the program on failure
+                    er => {
+                        expect_success_aborting(er, &"wup_tsk");
+                    }
+                }
+            }
+        });
+    }
+
+    pub unsafe fn notify_all(&self) {
+        self.waiters.with_locked(|waiters| {
+            while let Some(task) = waiters.pop_front() {
+                // Unpark the task
+                match unsafe { abi::wup_tsk(task) } {
+                    // The task already has a token.
+                    abi::E_QOVR => {}
+                    // Can't undo the effect; abort the program on failure
+                    er => {
+                        expect_success_aborting(er, &"wup_tsk");
+                    }
+                }
+            }
+        });
+    }
+
+    pub unsafe fn wait(&self, mutex: &Mutex) {
+        // Construct `Waiter`.
+        let mut waiter = waiter_queue::Waiter::new();
+        let waiter = NonNull::from(&mut waiter);
+
+        self.waiters.with_locked(|waiters| unsafe {
+            waiters.insert(waiter);
+        });
+
+        unsafe { mutex.unlock() };
+
+        // Wait until `waiter` is removed from the queue
+        loop {
+            // Park the current task
+            expect_success_aborting(unsafe { abi::slp_tsk() }, &"slp_tsk");
+
+            if !self.waiters.with_locked(|waiters| unsafe { waiters.is_queued(waiter) }) {
+                break;
+            }
+        }
+
+        unsafe { mutex.lock() };
+    }
+
+    pub unsafe fn wait_timeout(&self, mutex: &Mutex, dur: Duration) -> bool {
+        // Construct and pin `Waiter`
+        let mut waiter = waiter_queue::Waiter::new();
+        let waiter = NonNull::from(&mut waiter);
+
+        self.waiters.with_locked(|waiters| unsafe {
+            waiters.insert(waiter);
+        });
+
+        unsafe { mutex.unlock() };
+
+        // Park the current task and do not wake up until the timeout elapses
+        // or the task gets woken up by `notify_*`
+        match with_tmos_strong(dur, |tmo| {
+            let er = unsafe { abi::tslp_tsk(tmo) };
+            if er == 0 {
+                // We were unparked. Are we really dequeued?
+                if self.waiters.with_locked(|waiters| unsafe { waiters.is_queued(waiter) }) {
+                    // No we are not. Continue waiting.
+                    return abi::E_TMOUT;
+                }
+            }
+            er
+        }) {
+            abi::E_TMOUT => {}
+            er => {
+                expect_success_aborting(er, &"tslp_tsk");
+            }
+        }
+
+        // Remove `waiter` from `self.waiters`. If `waiter` is still in
+        // `waiters`, it means we woke up because of a timeout. Otherwise,
+        // we woke up because of `notify_*`.
+        let success = self.waiters.with_locked(|waiters| unsafe { !waiters.remove(waiter) });
+
+        unsafe { mutex.lock() };
+        success
+    }
+
+    pub unsafe fn destroy(&self) {}
+}
+
+mod waiter_queue {
+    use super::*;
+
+    pub struct WaiterQueue {
+        head: Option<ListHead>,
+    }
+
+    #[derive(Copy, Clone)]
+    struct ListHead {
+        first: NonNull<Waiter>,
+        last: NonNull<Waiter>,
+    }
+
+    unsafe impl Send for ListHead {}
+    unsafe impl Sync for ListHead {}
+
+    pub struct Waiter {
+        // These fields are only accessed through `&[mut] WaiterQueue`.
+        /// The waiting task's ID. Will be zeroed when the task is woken up
+        /// and removed from a queue.
+        task: abi::ID,
+        priority: abi::PRI,
+        prev: Option<NonNull<Waiter>>,
+        next: Option<NonNull<Waiter>>,
+    }
+
+    unsafe impl Send for Waiter {}
+    unsafe impl Sync for Waiter {}
+
+    impl Waiter {
+        #[inline]
+        pub fn new() -> Self {
+            let task = task::current_task_id();
+            let priority = task::task_priority(abi::TSK_SELF);
+
+            // Zeroness of `Waiter::task` indicates whether the `Waiter` is
+            // linked to a queue or not. This invariant is important for
+            // the correctness.
+            debug_assert_ne!(task, 0);
+
+            Self { task, priority, prev: None, next: None }
+        }
+    }
+
+    impl WaiterQueue {
+        #[inline]
+        pub const fn new() -> Self {
+            Self { head: None }
+        }
+
+        /// # Safety
+        ///
+        ///  - The caller must own `*waiter_ptr`. The caller will lose the
+        ///    ownership until `*waiter_ptr` is removed from `self`.
+        ///
+        ///  - `*waiter_ptr` must be valid until it's removed from the queue.
+        ///
+        ///  - `*waiter_ptr` must not have been previously inserted to a `WaiterQueue`.
+        ///
+        pub unsafe fn insert(&mut self, mut waiter_ptr: NonNull<Waiter>) {
+            unsafe {
+                let waiter = waiter_ptr.as_mut();
+
+                debug_assert!(waiter.prev.is_none());
+                debug_assert!(waiter.next.is_none());
+
+                if let Some(head) = &mut self.head {
+                    // Find the insertion position and insert `waiter`
+                    let insert_after = {
+                        let mut cursor = head.last;
+                        loop {
+                            if waiter.priority <= cursor.as_ref().priority {
+                                // `cursor` and all previous waiters have the same or higher
+                                // priority than `current_task_priority`. Insert the new
+                                // waiter right after `cursor`.
+                                break Some(cursor);
+                            }
+                            cursor = if let Some(prev) = cursor.as_ref().prev {
+                                prev
+                            } else {
+                                break None;
+                            };
+                        }
+                    };
+
+                    if let Some(mut insert_after) = insert_after {
+                        // Insert `waiter` after `insert_after`
+                        let insert_before = insert_after.as_ref().prev;
+
+                        waiter.prev = Some(insert_after);
+                        insert_after.as_mut().next = Some(waiter_ptr);
+
+                        waiter.next = insert_before;
+                        if let Some(mut insert_before) = insert_before {
+                            insert_before.as_mut().prev = Some(waiter_ptr);
+                        }
+                    } else {
+                        // Insert `waiter` to the front
+                        waiter.next = Some(head.first);
+                        head.first.as_mut().prev = Some(waiter_ptr);
+                        head.first = waiter_ptr;
+                    }
+                } else {
+                    // `waiter` is the only element
+                    self.head = Some(ListHead { first: waiter_ptr, last: waiter_ptr });
+                }
+            }
+        }
+
+        /// Given a `Waiter` that was previously inserted to `self`, remove
+        /// it from `self` if it's still there.
+        #[inline]
+        pub unsafe fn remove(&mut self, mut waiter_ptr: NonNull<Waiter>) -> bool {
+            unsafe {
+                let waiter = waiter_ptr.as_mut();
+                if waiter.task != 0 {
+                    let head = self.head.as_mut().unwrap();
+
+                    match (waiter.prev, waiter.next) {
+                        (Some(mut prev), Some(mut next)) => {
+                            prev.as_mut().next = Some(next);
+                            next.as_mut().next = Some(prev);
+                        }
+                        (None, Some(mut next)) => {
+                            head.first = next;
+                            next.as_mut().next = None;
+                        }
+                        (Some(mut prev), None) => {
+                            prev.as_mut().next = None;
+                            head.last = prev;
+                        }
+                        (None, None) => {
+                            self.head = None;
+                        }
+                    }
+
+                    waiter.task = 0;
+
+                    true
+                } else {
+                    false
+                }
+            }
+        }
+
+        /// Given a `Waiter` that was previously inserted to `self`, return a
+        /// flag indicating whether it's still in `self`.
+        #[inline]
+        pub unsafe fn is_queued(&self, waiter: NonNull<Waiter>) -> bool {
+            unsafe { waiter.as_ref().task != 0 }
+        }
+
+        pub fn pop_front(&mut self) -> Option<abi::ID> {
+            unsafe {
+                let head = self.head.as_mut()?;
+                let waiter = head.first.as_mut();
+
+                // Get the ID
+                let id = replace(&mut waiter.task, 0);
+
+                // Unlink the waiter
+                if let Some(mut next) = waiter.next {
+                    head.first = next;
+                    next.as_mut().prev = None;
+                } else {
+                    self.head = None;
+                }
+
+                Some(id)
+            }
+        }
+    }
+}
diff --git a/library/std/src/sys/itron/error.rs b/library/std/src/sys/itron/error.rs
new file mode 100644
index 00000000000..830c60d329e
--- /dev/null
+++ b/library/std/src/sys/itron/error.rs
@@ -0,0 +1,159 @@
+use crate::{fmt, io::ErrorKind};
+
+use super::abi;
+
+/// Wraps a μITRON error code.
+#[derive(Debug, Copy, Clone)]
+pub struct ItronError {
+    er: abi::ER,
+}
+
+impl ItronError {
+    /// Construct `ItronError` from the specified error code. Returns `None` if the
+    /// error code does not represent a failure or warning.
+    #[inline]
+    pub fn new(er: abi::ER) -> Option<Self> {
+        if er < 0 { Some(Self { er }) } else { None }
+    }
+
+    /// Returns `Ok(er)` if `er` represents a success or `Err(_)` otherwise.
+    #[inline]
+    pub fn err_if_negative(er: abi::ER) -> Result<abi::ER, Self> {
+        if let Some(error) = Self::new(er) { Err(error) } else { Ok(er) }
+    }
+
+    /// Get the raw error code.
+    #[inline]
+    pub fn as_raw(&self) -> abi::ER {
+        self.er
+    }
+}
+
+impl fmt::Display for ItronError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        // Allow the platforms to extend `error_name`
+        if let Some(name) = crate::sys::error::error_name(self.er) {
+            write!(f, "{} ({})", name, self.er)
+        } else {
+            write!(f, "{}", self.er)
+        }
+    }
+}
+
+/// Describe the specified μITRON error code. Returns `None` if it's an
+/// undefined error code.
+pub fn error_name(er: abi::ER) -> Option<&'static str> {
+    match er {
+        // Success
+        er if er >= 0 => None,
+
+        // μITRON 4.0
+        abi::E_SYS => Some("system error"),
+        abi::E_NOSPT => Some("unsupported function"),
+        abi::E_RSFN => Some("reserved function code"),
+        abi::E_RSATR => Some("reserved attribute"),
+        abi::E_PAR => Some("parameter error"),
+        abi::E_ID => Some("invalid ID number"),
+        abi::E_CTX => Some("context error"),
+        abi::E_MACV => Some("memory access violation"),
+        abi::E_OACV => Some("object access violation"),
+        abi::E_ILUSE => Some("illegal service call use"),
+        abi::E_NOMEM => Some("insufficient memory"),
+        abi::E_NOID => Some("no ID number available"),
+        abi::E_OBJ => Some("object state error"),
+        abi::E_NOEXS => Some("non-existent object"),
+        abi::E_QOVR => Some("queue overflow"),
+        abi::E_RLWAI => Some("forced release from waiting"),
+        abi::E_TMOUT => Some("polling failure or timeout"),
+        abi::E_DLT => Some("waiting object deleted"),
+        abi::E_CLS => Some("waiting object state changed"),
+        abi::E_WBLK => Some("non-blocking code accepted"),
+        abi::E_BOVR => Some("buffer overflow"),
+
+        // The TOPPERS third generation kernels
+        abi::E_NORES => Some("insufficient system resources"),
+        abi::E_RASTER => Some("termination request raised"),
+        abi::E_COMM => Some("communication failure"),
+
+        _ => None,
+    }
+}
+
+pub fn decode_error_kind(er: abi::ER) -> ErrorKind {
+    match er {
+        // Success
+        er if er >= 0 => ErrorKind::Uncategorized,
+
+        // μITRON 4.0
+        // abi::E_SYS
+        abi::E_NOSPT => ErrorKind::Unsupported, // Some("unsupported function"),
+        abi::E_RSFN => ErrorKind::InvalidInput, // Some("reserved function code"),
+        abi::E_RSATR => ErrorKind::InvalidInput, // Some("reserved attribute"),
+        abi::E_PAR => ErrorKind::InvalidInput,  // Some("parameter error"),
+        abi::E_ID => ErrorKind::NotFound,       // Some("invalid ID number"),
+        // abi::E_CTX
+        abi::E_MACV => ErrorKind::PermissionDenied, // Some("memory access violation"),
+        abi::E_OACV => ErrorKind::PermissionDenied, // Some("object access violation"),
+        // abi::E_ILUSE
+        abi::E_NOMEM => ErrorKind::OutOfMemory, // Some("insufficient memory"),
+        abi::E_NOID => ErrorKind::OutOfMemory,  // Some("no ID number available"),
+        // abi::E_OBJ
+        abi::E_NOEXS => ErrorKind::NotFound, // Some("non-existent object"),
+        // abi::E_QOVR
+        abi::E_RLWAI => ErrorKind::Interrupted, // Some("forced release from waiting"),
+        abi::E_TMOUT => ErrorKind::TimedOut,    // Some("polling failure or timeout"),
+        // abi::E_DLT
+        // abi::E_CLS
+        // abi::E_WBLK
+        // abi::E_BOVR
+
+        // The TOPPERS third generation kernels
+        abi::E_NORES => ErrorKind::OutOfMemory, // Some("insufficient system resources"),
+        // abi::E_RASTER
+        // abi::E_COMM
+        _ => ErrorKind::Uncategorized,
+    }
+}
+
+/// Similar to `ItronError::err_if_negative(er).expect()` except that, while
+/// panicking, it prints the message to `panic_output` and aborts the program
+/// instead. This ensures the error message is not obscured by double
+/// panicking.
+///
+/// This is useful for diagnosing creation failures of synchronization
+/// primitives that are used by `std`'s internal mechanisms. Such failures
+/// are common when the system is mis-configured to provide a too-small pool for
+/// kernel objects.
+#[inline]
+pub fn expect_success(er: abi::ER, msg: &&str) -> abi::ER {
+    match ItronError::err_if_negative(er) {
+        Ok(x) => x,
+        Err(e) => fail(e, msg),
+    }
+}
+
+/// Similar to `ItronError::err_if_negative(er).expect()` but aborts instead.
+///
+/// Use this where panicking is not allowed or the effect of the failure
+/// would be persistent.
+#[inline]
+pub fn expect_success_aborting(er: abi::ER, msg: &&str) -> abi::ER {
+    match ItronError::err_if_negative(er) {
+        Ok(x) => x,
+        Err(e) => fail_aborting(e, msg),
+    }
+}
+
+#[cold]
+pub fn fail(e: impl fmt::Display, msg: &&str) -> ! {
+    if crate::thread::panicking() {
+        fail_aborting(e, msg)
+    } else {
+        panic!("{} failed: {}", *msg, e)
+    }
+}
+
+#[cold]
+pub fn fail_aborting(e: impl fmt::Display, msg: &&str) -> ! {
+    rtabort!("{} failed: {}", *msg, e)
+}
diff --git a/library/std/src/sys/itron/mutex.rs b/library/std/src/sys/itron/mutex.rs
new file mode 100644
index 00000000000..e01f595ac54
--- /dev/null
+++ b/library/std/src/sys/itron/mutex.rs
@@ -0,0 +1,183 @@
+//! Mutex implementation backed by μITRON mutexes. Assumes `acre_mtx` and
+//! `TA_INHERIT` are available.
+use super::{
+    abi,
+    error::{expect_success, expect_success_aborting, fail, ItronError},
+    spin::SpinIdOnceCell,
+};
+use crate::cell::UnsafeCell;
+
+pub struct Mutex {
+    /// The ID of the underlying mutex object
+    mtx: SpinIdOnceCell<()>,
+}
+
+pub type MovableMutex = Mutex;
+
+/// Create a mutex object. This function never panics.
+fn new_mtx() -> Result<abi::ID, ItronError> {
+    ItronError::err_if_negative(unsafe {
+        abi::acre_mtx(&abi::T_CMTX {
+            // Priority inheritance mutex
+            mtxatr: abi::TA_INHERIT,
+            // Unused
+            ceilpri: 0,
+        })
+    })
+}
+
+impl Mutex {
+    pub const fn new() -> Mutex {
+        Mutex { mtx: SpinIdOnceCell::new() }
+    }
+
+    pub unsafe fn init(&mut self) {
+        // Initialize `self.mtx` eagerly
+        let id = new_mtx().unwrap_or_else(|e| fail(e, &"acre_mtx"));
+        unsafe { self.mtx.set_unchecked((id, ())) };
+    }
+
+    /// Get the inner mutex's ID, which is lazily created.
+    fn raw(&self) -> abi::ID {
+        match self.mtx.get_or_try_init(|| new_mtx().map(|id| (id, ()))) {
+            Ok((id, ())) => id,
+            Err(e) => fail(e, &"acre_mtx"),
+        }
+    }
+
+    pub unsafe fn lock(&self) {
+        let mtx = self.raw();
+        expect_success(unsafe { abi::loc_mtx(mtx) }, &"loc_mtx");
+    }
+
+    pub unsafe fn unlock(&self) {
+        let mtx = unsafe { self.mtx.get_unchecked().0 };
+        expect_success_aborting(unsafe { abi::unl_mtx(mtx) }, &"unl_mtx");
+    }
+
+    pub unsafe fn try_lock(&self) -> bool {
+        let mtx = self.raw();
+        match unsafe { abi::ploc_mtx(mtx) } {
+            abi::E_TMOUT => false,
+            er => {
+                expect_success(er, &"ploc_mtx");
+                true
+            }
+        }
+    }
+
+    pub unsafe fn destroy(&self) {
+        if let Some(mtx) = self.mtx.get().map(|x| x.0) {
+            expect_success_aborting(unsafe { abi::del_mtx(mtx) }, &"del_mtx");
+        }
+    }
+}
+
+pub(super) struct MutexGuard<'a>(&'a Mutex);
+
+impl<'a> MutexGuard<'a> {
+    #[inline]
+    pub(super) fn lock(x: &'a Mutex) -> Self {
+        unsafe { x.lock() };
+        Self(x)
+    }
+}
+
+impl Drop for MutexGuard<'_> {
+    #[inline]
+    fn drop(&mut self) {
+        unsafe { self.0.unlock() };
+    }
+}
+
+// All empty stubs because this platform does not yet support threads, so lock
+// acquisition always succeeds.
+pub struct ReentrantMutex {
+    /// The ID of the underlying mutex object
+    mtx: abi::ID,
+    /// The lock count.
+    count: UnsafeCell<usize>,
+}
+
+unsafe impl Send for ReentrantMutex {}
+unsafe impl Sync for ReentrantMutex {}
+
+impl ReentrantMutex {
+    pub const unsafe fn uninitialized() -> ReentrantMutex {
+        ReentrantMutex { mtx: 0, count: UnsafeCell::new(0) }
+    }
+
+    pub unsafe fn init(&mut self) {
+        self.mtx = expect_success(
+            unsafe {
+                abi::acre_mtx(&abi::T_CMTX {
+                    // Priority inheritance mutex
+                    mtxatr: abi::TA_INHERIT,
+                    // Unused
+                    ceilpri: 0,
+                })
+            },
+            &"acre_mtx",
+        );
+    }
+
+    pub unsafe fn lock(&self) {
+        match unsafe { abi::loc_mtx(self.mtx) } {
+            abi::E_OBJ => {
+                // Recursive lock
+                unsafe {
+                    let count = &mut *self.count.get();
+                    if let Some(new_count) = count.checked_add(1) {
+                        *count = new_count;
+                    } else {
+                        // counter overflow
+                        rtabort!("lock count overflow");
+                    }
+                }
+            }
+            er => {
+                expect_success(er, &"loc_mtx");
+            }
+        }
+    }
+
+    pub unsafe fn unlock(&self) {
+        unsafe {
+            let count = &mut *self.count.get();
+            if *count > 0 {
+                *count -= 1;
+                return;
+            }
+        }
+
+        expect_success_aborting(unsafe { abi::unl_mtx(self.mtx) }, &"unl_mtx");
+    }
+
+    pub unsafe fn try_lock(&self) -> bool {
+        let er = unsafe { abi::ploc_mtx(self.mtx) };
+        if er == abi::E_OBJ {
+            // Recursive lock
+            unsafe {
+                let count = &mut *self.count.get();
+                if let Some(new_count) = count.checked_add(1) {
+                    *count = new_count;
+                } else {
+                    // counter overflow
+                    rtabort!("lock count overflow");
+                }
+            }
+            true
+        } else if er == abi::E_TMOUT {
+            // Locked by another thread
+            false
+        } else {
+            expect_success(er, &"ploc_mtx");
+            // Top-level lock by the current thread
+            true
+        }
+    }
+
+    pub unsafe fn destroy(&self) {
+        expect_success_aborting(unsafe { abi::del_mtx(self.mtx) }, &"del_mtx");
+    }
+}
diff --git a/library/std/src/sys/itron/spin.rs b/library/std/src/sys/itron/spin.rs
new file mode 100644
index 00000000000..d0149d1f037
--- /dev/null
+++ b/library/std/src/sys/itron/spin.rs
@@ -0,0 +1,164 @@
+use super::abi;
+use crate::{
+    cell::UnsafeCell,
+    convert::TryFrom,
+    mem::MaybeUninit,
+    sync::atomic::{AtomicBool, AtomicUsize, Ordering},
+};
+
+/// A mutex implemented by `dis_dsp` (for intra-core synchronization) and a
+/// spinlock (for inter-core synchronization).
+pub struct SpinMutex<T = ()> {
+    locked: AtomicBool,
+    data: UnsafeCell<T>,
+}
+
+impl<T> SpinMutex<T> {
+    #[inline]
+    pub const fn new(x: T) -> Self {
+        Self { locked: AtomicBool::new(false), data: UnsafeCell::new(x) }
+    }
+
+    /// Acquire a lock.
+    #[inline]
+    pub fn with_locked<R>(&self, f: impl FnOnce(&mut T) -> R) -> R {
+        struct SpinMutexGuard<'a>(&'a AtomicBool);
+
+        impl Drop for SpinMutexGuard<'_> {
+            #[inline]
+            fn drop(&mut self) {
+                self.0.store(false, Ordering::Release);
+                unsafe { abi::ena_dsp() };
+            }
+        }
+
+        let _guard;
+        if unsafe { abi::sns_dsp() } == 0 {
+            let er = unsafe { abi::dis_dsp() };
+            debug_assert!(er >= 0);
+
+            // Wait until the current processor acquires a lock.
+            while self.locked.swap(true, Ordering::Acquire) {}
+
+            _guard = SpinMutexGuard(&self.locked);
+        }
+
+        f(unsafe { &mut *self.data.get() })
+    }
+}
+
+/// `OnceCell<(abi::ID, T)>` implemented by `dis_dsp` (for intra-core
+/// synchronization) and a spinlock (for inter-core synchronization).
+///
+/// It's assumed that `0` is not a valid ID, and all kernel
+/// object IDs fall into range `1..=usize::MAX`.
+pub struct SpinIdOnceCell<T = ()> {
+    id: AtomicUsize,
+    spin: SpinMutex<()>,
+    extra: UnsafeCell<MaybeUninit<T>>,
+}
+
+const ID_UNINIT: usize = 0;
+
+impl<T> SpinIdOnceCell<T> {
+    #[inline]
+    pub const fn new() -> Self {
+        Self {
+            id: AtomicUsize::new(ID_UNINIT),
+            extra: UnsafeCell::new(MaybeUninit::uninit()),
+            spin: SpinMutex::new(()),
+        }
+    }
+
+    #[inline]
+    pub fn get(&self) -> Option<(abi::ID, &T)> {
+        match self.id.load(Ordering::Acquire) {
+            ID_UNINIT => None,
+            id => Some((id as abi::ID, unsafe { (&*self.extra.get()).assume_init_ref() })),
+        }
+    }
+
+    #[inline]
+    pub fn get_mut(&mut self) -> Option<(abi::ID, &mut T)> {
+        match *self.id.get_mut() {
+            ID_UNINIT => None,
+            id => Some((id as abi::ID, unsafe { (&mut *self.extra.get()).assume_init_mut() })),
+        }
+    }
+
+    #[inline]
+    pub unsafe fn get_unchecked(&self) -> (abi::ID, &T) {
+        (self.id.load(Ordering::Acquire) as abi::ID, unsafe {
+            (&*self.extra.get()).assume_init_ref()
+        })
+    }
+
+    /// Assign the content without checking if it's already initialized or
+    /// being initialized.
+    pub unsafe fn set_unchecked(&self, (id, extra): (abi::ID, T)) {
+        debug_assert!(self.get().is_none());
+
+        // Assumption: A positive `abi::ID` fits in `usize`.
+        debug_assert!(id >= 0);
+        debug_assert!(usize::try_from(id).is_ok());
+        let id = id as usize;
+
+        unsafe { *self.extra.get() = MaybeUninit::new(extra) };
+        self.id.store(id, Ordering::Release);
+    }
+
+    /// Gets the contents of the cell, initializing it with `f` if
+    /// the cell was empty. If the cell was empty and `f` failed, an
+    /// error is returned.
+    ///
+    /// Warning: `f` must not perform a blocking operation, which
+    /// includes panicking.
+    #[inline]
+    pub fn get_or_try_init<F, E>(&self, f: F) -> Result<(abi::ID, &T), E>
+    where
+        F: FnOnce() -> Result<(abi::ID, T), E>,
+    {
+        // Fast path
+        if let Some(x) = self.get() {
+            return Ok(x);
+        }
+
+        self.initialize(f)?;
+
+        debug_assert!(self.get().is_some());
+
+        // Safety: The inner value has been initialized
+        Ok(unsafe { self.get_unchecked() })
+    }
+
+    fn initialize<F, E>(&self, f: F) -> Result<(), E>
+    where
+        F: FnOnce() -> Result<(abi::ID, T), E>,
+    {
+        self.spin.with_locked(|_| {
+            if self.id.load(Ordering::Relaxed) == ID_UNINIT {
+                let (initialized_id, initialized_extra) = f()?;
+
+                // Assumption: A positive `abi::ID` fits in `usize`.
+                debug_assert!(initialized_id >= 0);
+                debug_assert!(usize::try_from(initialized_id).is_ok());
+                let initialized_id = initialized_id as usize;
+
+                // Store the initialized contents. Use the release ordering to
+                // make sure the write is visible to the callers of `get`.
+                unsafe { *self.extra.get() = MaybeUninit::new(initialized_extra) };
+                self.id.store(initialized_id, Ordering::Release);
+            }
+            Ok(())
+        })
+    }
+}
+
+impl<T> Drop for SpinIdOnceCell<T> {
+    #[inline]
+    fn drop(&mut self) {
+        if self.get_mut().is_some() {
+            unsafe { (&mut *self.extra.get()).assume_init_drop() };
+        }
+    }
+}
diff --git a/library/std/src/sys/itron/task.rs b/library/std/src/sys/itron/task.rs
new file mode 100644
index 00000000000..94beb50a254
--- /dev/null
+++ b/library/std/src/sys/itron/task.rs
@@ -0,0 +1,44 @@
+use super::{
+    abi,
+    error::{fail, fail_aborting, ItronError},
+};
+
+use crate::mem::MaybeUninit;
+
+/// Get the ID of the task in Running state. Panics on failure.
+#[inline]
+pub fn current_task_id() -> abi::ID {
+    try_current_task_id().unwrap_or_else(|e| fail(e, &"get_tid"))
+}
+
+/// Get the ID of the task in Running state. Aborts on failure.
+#[inline]
+pub fn current_task_id_aborting() -> abi::ID {
+    try_current_task_id().unwrap_or_else(|e| fail_aborting(e, &"get_tid"))
+}
+
+/// Get the ID of the task in Running state.
+#[inline]
+pub fn try_current_task_id() -> Result<abi::ID, ItronError> {
+    unsafe {
+        let mut out = MaybeUninit::uninit();
+        ItronError::err_if_negative(abi::get_tid(out.as_mut_ptr()))?;
+        Ok(out.assume_init())
+    }
+}
+
+/// Get the specified task's priority. Panics on failure.
+#[inline]
+pub fn task_priority(task: abi::ID) -> abi::PRI {
+    try_task_priority(task).unwrap_or_else(|e| fail(e, &"get_pri"))
+}
+
+/// Get the specified task's priority.
+#[inline]
+pub fn try_task_priority(task: abi::ID) -> Result<abi::PRI, ItronError> {
+    unsafe {
+        let mut out = MaybeUninit::uninit();
+        ItronError::err_if_negative(abi::get_pri(task, out.as_mut_ptr()))?;
+        Ok(out.assume_init())
+    }
+}
diff --git a/library/std/src/sys/itron/thread.rs b/library/std/src/sys/itron/thread.rs
new file mode 100644
index 00000000000..4feb9c5a6d7
--- /dev/null
+++ b/library/std/src/sys/itron/thread.rs
@@ -0,0 +1,352 @@
+//! Thread implementation backed by μITRON tasks. Assumes `acre_tsk` and
+//! `exd_tsk` are available.
+use super::{
+    abi,
+    error::{expect_success, expect_success_aborting, ItronError},
+    task,
+    time::dur2reltims,
+};
+use crate::{
+    cell::UnsafeCell,
+    convert::TryFrom,
+    ffi::CStr,
+    hint, io,
+    mem::ManuallyDrop,
+    sync::atomic::{AtomicUsize, Ordering},
+    sys::thread_local_dtor::run_dtors,
+    time::Duration,
+};
+
+pub struct Thread {
+    inner: ManuallyDrop<Box<ThreadInner>>,
+
+    /// The ID of the underlying task.
+    task: abi::ID,
+}
+
+/// State data shared between a parent thread and child thread. It's dropped on
+/// a transition to one of the final states.
+struct ThreadInner {
+    /// This field is used on thread creation to pass a closure from
+    /// `Thread::new` to the created task.
+    start: UnsafeCell<ManuallyDrop<Box<dyn FnOnce()>>>,
+
+    /// A state machine. Each transition is annotated with `[...]` in the
+    /// source code.
+    ///
+    /// ```text
+    ///
+    ///    <P>: parent, <C>: child, (?): don't-care
+    ///
+    ///       DETACHED (-1)  -------------------->  EXITED (?)
+    ///                        <C>finish/exd_tsk
+    ///          ^
+    ///          |
+    ///          | <P>detach
+    ///          |
+    ///
+    ///       INIT (0)  ----------------------->  FINISHED (-1)
+    ///                        <C>finish
+    ///          |                                    |
+    ///          | <P>join/slp_tsk                    | <P>join/del_tsk
+    ///          |                                    | <P>detach/del_tsk
+    ///          v                                    v
+    ///
+    ///       JOINING                              JOINED (?)
+    ///     (parent_tid)
+    ///                                            ^
+    ///             \                             /
+    ///              \  <C>finish/wup_tsk        / <P>slp_tsk-complete/ter_tsk
+    ///               \                         /                      & del_tsk
+    ///                \                       /
+    ///                 '--> JOIN_FINALIZE ---'
+    ///                          (-1)
+    ///
+    lifecycle: AtomicUsize,
+}
+
+// Safety: The only `!Sync` field, `ThreadInner::start`, is only touched by
+//         the task represented by `ThreadInner`.
+unsafe impl Sync for ThreadInner {}
+
+const LIFECYCLE_INIT: usize = 0;
+const LIFECYCLE_FINISHED: usize = usize::MAX;
+const LIFECYCLE_DETACHED: usize = usize::MAX;
+const LIFECYCLE_JOIN_FINALIZE: usize = usize::MAX;
+const LIFECYCLE_DETACHED_OR_JOINED: usize = usize::MAX;
+const LIFECYCLE_EXITED_OR_FINISHED_OR_JOIN_FINALIZE: usize = usize::MAX;
+// there's no single value for `JOINING`
+
+pub const DEFAULT_MIN_STACK_SIZE: usize = 1024 * crate::mem::size_of::<usize>();
+
+impl Thread {
+    /// # Safety
+    ///
+    /// See `thread::Builder::spawn_unchecked` for safety requirements.
+    pub unsafe fn new(stack: usize, p: Box<dyn FnOnce()>) -> io::Result<Thread> {
+        // Inherit the current task's priority
+        let current_task = task::try_current_task_id().map_err(|e| e.as_io_error())?;
+        let priority = task::try_task_priority(current_task).map_err(|e| e.as_io_error())?;
+
+        let inner = Box::new(ThreadInner {
+            start: UnsafeCell::new(ManuallyDrop::new(p)),
+            lifecycle: AtomicUsize::new(LIFECYCLE_INIT),
+        });
+
+        unsafe extern "C" fn trampoline(exinf: isize) {
+            // Safety: `ThreadInner` is alive at this point
+            let inner = unsafe { &*(exinf as *const ThreadInner) };
+
+            // Safety: Since `trampoline` is called only once for each
+            //         `ThreadInner` and only `trampoline` touches `start`,
+            //         `start` contains contents and is safe to mutably borrow.
+            let p = unsafe { ManuallyDrop::take(&mut *inner.start.get()) };
+            p();
+
+            // Fix the current thread's state just in case, so that the
+            // destructors won't abort
+            // Safety: Not really unsafe
+            let _ = unsafe { abi::unl_cpu() };
+            let _ = unsafe { abi::ena_dsp() };
+
+            // Run TLS destructors now because they are not
+            // called automatically for terminated tasks.
+            unsafe { run_dtors() };
+
+            let old_lifecycle = inner
+                .lifecycle
+                .swap(LIFECYCLE_EXITED_OR_FINISHED_OR_JOIN_FINALIZE, Ordering::Release);
+
+            match old_lifecycle {
+                LIFECYCLE_DETACHED => {
+                    // [DETACHED → EXITED]
+                    // No one will ever join, so we'll ask the collector task to
+                    // delete the task.
+
+                    // In this case, `inner`'s ownership has been moved to us,
+                    // And we are responsible for dropping it. The acquire
+                    // ordering is not necessary because the parent thread made
+                    // no memory acccess needing synchronization since the call
+                    // to `acre_tsk`.
+                    // Safety: See above.
+                    let _ = unsafe { Box::from_raw(inner as *const _ as *mut ThreadInner) };
+
+                    // Safety: There are no pinned references to the stack
+                    unsafe { terminate_and_delete_current_task() };
+                }
+                LIFECYCLE_INIT => {
+                    // [INIT → FINISHED]
+                    // The parent hasn't decided whether to join or detach this
+                    // thread yet. Whichever option the parent chooses,
+                    // it'll have to delete this task.
+                    // Since the parent might drop `*inner` as soon as it sees
+                    // `FINISHED`, the release ordering must be used in the
+                    // above `swap` call.
+                }
+                parent_tid => {
+                    // Since the parent might drop `*inner` and terminate us as
+                    // soon as it sees `JOIN_FINALIZE`, the release ordering
+                    // must be used in the above `swap` call.
+
+                    // [JOINING → JOIN_FINALIZE]
+                    // Wake up the parent task.
+                    expect_success(
+                        unsafe {
+                            let mut er = abi::wup_tsk(parent_tid as _);
+                            if er == abi::E_QOVR {
+                                // `E_QOVR` indicates there's already
+                                // a parking token
+                                er = abi::E_OK;
+                            }
+                            er
+                        },
+                        &"wup_tsk",
+                    );
+                }
+            }
+        }
+
+        let inner_ptr = (&*inner) as *const ThreadInner;
+
+        let new_task = ItronError::err_if_negative(unsafe {
+            abi::acre_tsk(&abi::T_CTSK {
+                // Activate this task immediately
+                tskatr: abi::TA_ACT,
+                exinf: inner_ptr as abi::EXINF,
+                // The entry point
+                task: Some(trampoline),
+                itskpri: priority,
+                stksz: stack,
+                // Let the kernel allocate the stack,
+                stk: crate::ptr::null_mut(),
+            })
+        })
+        .map_err(|e| e.as_io_error())?;
+
+        Ok(Self { inner: ManuallyDrop::new(inner), task: new_task })
+    }
+
+    pub fn yield_now() {
+        expect_success(unsafe { abi::rot_rdq(abi::TPRI_SELF) }, &"rot_rdq");
+    }
+
+    pub fn set_name(_name: &CStr) {
+        // nope
+    }
+
+    pub fn sleep(dur: Duration) {
+        for timeout in dur2reltims(dur) {
+            expect_success(unsafe { abi::dly_tsk(timeout) }, &"dly_tsk");
+        }
+    }
+
+    pub fn join(mut self) {
+        let inner = &*self.inner;
+        // Get the current task ID. Panicking here would cause a resource leak,
+        // so just abort on failure.
+        let current_task = task::current_task_id_aborting();
+        debug_assert!(usize::try_from(current_task).is_ok());
+        debug_assert_ne!(current_task as usize, LIFECYCLE_INIT);
+        debug_assert_ne!(current_task as usize, LIFECYCLE_DETACHED);
+
+        let current_task = current_task as usize;
+
+        match inner.lifecycle.swap(current_task, Ordering::Acquire) {
+            LIFECYCLE_INIT => {
+                // [INIT → JOINING]
+                // The child task will transition the state to `JOIN_FINALIZE`
+                // and wake us up.
+                loop {
+                    expect_success_aborting(unsafe { abi::slp_tsk() }, &"slp_tsk");
+                    // To synchronize with the child task's memory accesses to
+                    // `inner` up to the point of the assignment of
+                    // `JOIN_FINALIZE`, `Ordering::Acquire` must be used for the
+                    // `load`.
+                    if inner.lifecycle.load(Ordering::Acquire) == LIFECYCLE_JOIN_FINALIZE {
+                        break;
+                    }
+                }
+
+                // [JOIN_FINALIZE → JOINED]
+            }
+            LIFECYCLE_FINISHED => {
+                // [FINISHED → JOINED]
+                // To synchronize with the child task's memory accesses to
+                // `inner` up to the point of the assignment of `FINISHED`,
+                // `Ordering::Acquire` must be used for the above `swap` call`.
+            }
+            _ => unsafe { hint::unreachable_unchecked() },
+        }
+
+        // Terminate and delete the task
+        // Safety: `self.task` still represents a task we own (because this
+        //         method or `detach_inner` is called only once for each
+        //         `Thread`). The task indicated that it's safe to delete by
+        //         entering the `FINISHED` or `JOIN_FINALIZE` state.
+        unsafe { terminate_and_delete_task(self.task) };
+
+        // In either case, we are responsible for dropping `inner`.
+        // Safety: The contents of `self.inner` will not be accessed hereafter
+        let _inner = unsafe { ManuallyDrop::take(&mut self.inner) };
+
+        // Skip the destructor (because it would attempt to detach the thread)
+        crate::mem::forget(self);
+    }
+}
+
+impl Drop for Thread {
+    fn drop(&mut self) {
+        // Detach the thread.
+        match self.inner.lifecycle.swap(LIFECYCLE_DETACHED_OR_JOINED, Ordering::Acquire) {
+            LIFECYCLE_INIT => {
+                // [INIT → DETACHED]
+                // When the time comes, the child will figure out that no
+                // one will ever join it.
+                // The ownership of `self.inner` is moved to the child thread.
+                // However, the release ordering is not necessary because we
+                // made no memory acccess needing synchronization since the call
+                // to `acre_tsk`.
+            }
+            LIFECYCLE_FINISHED => {
+                // [FINISHED → JOINED]
+                // The task has already decided that we should delete the task.
+                // To synchronize with the child task's memory accesses to
+                // `inner` up to the point of the assignment of `FINISHED`,
+                // the acquire ordering is required for the above `swap` call.
+
+                // Terminate and delete the task
+                // Safety: `self.task` still represents a task we own (because
+                //         this method or `join_inner` is called only once for
+                //         each `Thread`). The task  indicated that it's safe to
+                //         delete by entering the `FINISHED` state.
+                unsafe { terminate_and_delete_task(self.task) };
+
+                // Wwe are responsible for dropping `inner`.
+                // Safety: The contents of `self.inner` will not be accessed
+                //         hereafter
+                unsafe { ManuallyDrop::drop(&mut self.inner) };
+            }
+            _ => unsafe { hint::unreachable_unchecked() },
+        }
+    }
+}
+
+pub mod guard {
+    pub type Guard = !;
+    pub unsafe fn current() -> Option<Guard> {
+        None
+    }
+    pub unsafe fn init() -> Option<Guard> {
+        None
+    }
+}
+
+/// Terminate and delete the specified task.
+///
+/// This function will abort if `deleted_task` refers to the calling task.
+///
+/// It is assumed that the specified task is solely managed by the caller -
+/// i.e., other threads must not "resuscitate" the specified task or delete it
+/// prematurely while this function is still in progress. It is allowed for the
+/// specified task to exit by its own.
+///
+/// # Safety
+///
+/// The task must be safe to terminate. This is in general not true
+/// because there might be pinned references to the task's stack.
+unsafe fn terminate_and_delete_task(deleted_task: abi::ID) {
+    // Terminate the task
+    // Safety: Upheld by the caller
+    match unsafe { abi::ter_tsk(deleted_task) } {
+        // Indicates the task is already dormant, ignore it
+        abi::E_OBJ => {}
+        er => {
+            expect_success_aborting(er, &"ter_tsk");
+        }
+    }
+
+    // Delete the task
+    // Safety: Upheld by the caller
+    expect_success_aborting(unsafe { abi::del_tsk(deleted_task) }, &"del_tsk");
+}
+
+/// Terminate and delete the calling task.
+///
+/// Atomicity is not required - i.e., it can be assumed that other threads won't
+/// `ter_tsk` the calling task while this function is still in progress. (This
+/// property makes it easy to implement this operation on μITRON-derived kernels
+/// that don't support `exd_tsk`.)
+///
+/// # Safety
+///
+/// The task must be safe to terminate. This is in general not true
+/// because there might be pinned references to the task's stack.
+unsafe fn terminate_and_delete_current_task() -> ! {
+    expect_success_aborting(unsafe { abi::exd_tsk() }, &"exd_tsk");
+    // Safety: `exd_tsk` never returns on success
+    unsafe { crate::hint::unreachable_unchecked() };
+}
+
+pub fn available_concurrency() -> io::Result<crate::num::NonZeroUsize> {
+    super::unsupported()
+}
diff --git a/library/std/src/sys/itron/time.rs b/library/std/src/sys/itron/time.rs
new file mode 100644
index 00000000000..6a992ad1d3c
--- /dev/null
+++ b/library/std/src/sys/itron/time.rs
@@ -0,0 +1,123 @@
+use super::{abi, error::expect_success};
+use crate::{convert::TryInto, mem::MaybeUninit, time::Duration};
+
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug, Hash)]
+pub struct Instant(abi::SYSTIM);
+
+impl Instant {
+    pub fn now() -> Instant {
+        // Safety: The provided pointer is valid
+        unsafe {
+            let mut out = MaybeUninit::uninit();
+            expect_success(abi::get_tim(out.as_mut_ptr()), &"get_tim");
+            Instant(out.assume_init())
+        }
+    }
+
+    pub const fn zero() -> Instant {
+        Instant(0)
+    }
+
+    pub fn actually_monotonic() -> bool {
+        // There are ways to change the system time
+        false
+    }
+
+    pub fn checked_sub_instant(&self, other: &Instant) -> Option<Duration> {
+        self.0.checked_sub(other.0).map(|ticks| {
+            // `SYSTIM` is measured in microseconds
+            Duration::from_micros(ticks)
+        })
+    }
+
+    pub fn checked_add_duration(&self, other: &Duration) -> Option<Instant> {
+        // `SYSTIM` is measured in microseconds
+        let ticks = other.as_micros();
+
+        Some(Instant(self.0.checked_add(ticks.try_into().ok()?)?))
+    }
+
+    pub fn checked_sub_duration(&self, other: &Duration) -> Option<Instant> {
+        // `SYSTIM` is measured in microseconds
+        let ticks = other.as_micros();
+
+        Some(Instant(self.0.checked_sub(ticks.try_into().ok()?)?))
+    }
+}
+
+/// Split `Duration` into zero or more `RELTIM`s.
+#[inline]
+pub fn dur2reltims(dur: Duration) -> impl Iterator<Item = abi::RELTIM> {
+    // `RELTIM` is microseconds
+    let mut ticks = dur.as_micros();
+
+    crate::iter::from_fn(move || {
+        if ticks == 0 {
+            None
+        } else if ticks <= abi::TMAX_RELTIM as u128 {
+            Some(crate::mem::replace(&mut ticks, 0) as abi::RELTIM)
+        } else {
+            ticks -= abi::TMAX_RELTIM as u128;
+            Some(abi::TMAX_RELTIM)
+        }
+    })
+}
+
+/// Split `Duration` into one or more `TMO`s.
+#[inline]
+fn dur2tmos(dur: Duration) -> impl Iterator<Item = abi::TMO> {
+    // `TMO` is microseconds
+    let mut ticks = dur.as_micros();
+    let mut end = false;
+
+    crate::iter::from_fn(move || {
+        if end {
+            None
+        } else if ticks <= abi::TMAX_RELTIM as u128 {
+            end = true;
+            Some(crate::mem::replace(&mut ticks, 0) as abi::TMO)
+        } else {
+            ticks -= abi::TMAX_RELTIM as u128;
+            Some(abi::TMAX_RELTIM)
+        }
+    })
+}
+
+/// Split `Duration` into one or more API calls with timeout.
+#[inline]
+pub fn with_tmos(dur: Duration, mut f: impl FnMut(abi::TMO) -> abi::ER) -> abi::ER {
+    let mut er = abi::E_TMOUT;
+    for tmo in dur2tmos(dur) {
+        er = f(tmo);
+        if er != abi::E_TMOUT {
+            break;
+        }
+    }
+    er
+}
+
+/// Split `Duration` into one or more API calls with timeout. This function can
+/// handle spurious wakeups.
+#[inline]
+pub fn with_tmos_strong(dur: Duration, mut f: impl FnMut(abi::TMO) -> abi::ER) -> abi::ER {
+    // `TMO` and `SYSTIM` are microseconds.
+    // Clamp at `SYSTIM::MAX` for performance reasons. This shouldn't cause
+    // a problem in practice. (`u64::MAX` μs ≈ 584942 years)
+    let ticks = dur.as_micros().min(abi::SYSTIM::MAX as u128) as abi::SYSTIM;
+
+    let start = Instant::now().0;
+    let mut elapsed = 0;
+    let mut er = abi::E_TMOUT;
+    while elapsed <= ticks {
+        er = f(elapsed.min(abi::TMAX_RELTIM as abi::SYSTIM) as abi::TMO);
+        if er != abi::E_TMOUT {
+            break;
+        }
+        elapsed = Instant::now().0.wrapping_sub(start);
+    }
+
+    er
+}
+
+#[cfg(test)]
+mod tests;
diff --git a/library/std/src/sys/itron/time/tests.rs b/library/std/src/sys/itron/time/tests.rs
new file mode 100644
index 00000000000..d14035d9da4
--- /dev/null
+++ b/library/std/src/sys/itron/time/tests.rs
@@ -0,0 +1,33 @@
+use super::*;
+
+fn reltim2dur(t: u64) -> Duration {
+    Duration::from_micros(t)
+}
+
+#[test]
+fn test_dur2reltims() {
+    assert_eq!(dur2reltims(reltim2dur(0)).collect::<Vec<_>>(), vec![]);
+    assert_eq!(dur2reltims(reltim2dur(42)).collect::<Vec<_>>(), vec![42]);
+    assert_eq!(
+        dur2reltims(reltim2dur(abi::TMAX_RELTIM as u64)).collect::<Vec<_>>(),
+        vec![abi::TMAX_RELTIM]
+    );
+    assert_eq!(
+        dur2reltims(reltim2dur(abi::TMAX_RELTIM as u64 + 10000)).collect::<Vec<_>>(),
+        vec![abi::TMAX_RELTIM, 10000]
+    );
+}
+
+#[test]
+fn test_dur2tmos() {
+    assert_eq!(dur2tmos(reltim2dur(0)).collect::<Vec<_>>(), vec![0]);
+    assert_eq!(dur2tmos(reltim2dur(42)).collect::<Vec<_>>(), vec![42]);
+    assert_eq!(
+        dur2tmos(reltim2dur(abi::TMAX_RELTIM as u64)).collect::<Vec<_>>(),
+        vec![abi::TMAX_RELTIM]
+    );
+    assert_eq!(
+        dur2tmos(reltim2dur(abi::TMAX_RELTIM as u64 + 10000)).collect::<Vec<_>>(),
+        vec![abi::TMAX_RELTIM, 10000]
+    );
+}
diff --git a/library/std/src/sys/mod.rs b/library/std/src/sys/mod.rs
index f813587b1b3..8b8be6ebc2f 100644
--- a/library/std/src/sys/mod.rs
+++ b/library/std/src/sys/mod.rs
@@ -31,6 +31,9 @@ cfg_if::cfg_if! {
     } else if #[cfg(windows)] {
         mod windows;
         pub use self::windows::*;
+    } else if #[cfg(target_os = "solid_asp3")] {
+        mod solid;
+        pub use self::solid::*;
     } else if #[cfg(target_os = "hermit")] {
         mod hermit;
         pub use self::hermit::*;
diff --git a/library/std/src/sys/solid/abi/fs.rs b/library/std/src/sys/solid/abi/fs.rs
new file mode 100644
index 00000000000..32800bd9a9d
--- /dev/null
+++ b/library/std/src/sys/solid/abi/fs.rs
@@ -0,0 +1,53 @@
+//! `solid_fs.h`
+use crate::os::raw::{c_char, c_int, c_uchar};
+pub use libc::{
+    blksize_t, dev_t, ino_t, off_t, stat, time_t, O_APPEND, O_CREAT, O_EXCL, O_RDONLY, O_RDWR,
+    O_TRUNC, O_WRONLY, SEEK_CUR, SEEK_END, SEEK_SET, S_IEXEC, S_IFBLK, S_IFCHR, S_IFDIR, S_IFIFO,
+    S_IFMT, S_IFREG, S_IREAD, S_IWRITE,
+};
+
+pub const O_ACCMODE: c_int = 0x3;
+
+pub const SOLID_MAX_PATH: usize = 256;
+
+#[repr(C)]
+#[derive(Copy, Clone)]
+pub struct dirent {
+    pub d_ino: ino_t,
+    pub d_type: c_uchar,
+    pub d_name: [c_char; 256usize],
+}
+
+pub const DT_UNKNOWN: c_uchar = 0;
+pub const DT_FIFO: c_uchar = 1;
+pub const DT_CHR: c_uchar = 2;
+pub const DT_DIR: c_uchar = 4;
+pub const DT_BLK: c_uchar = 6;
+pub const DT_REG: c_uchar = 8;
+pub const DT_LNK: c_uchar = 10;
+pub const DT_SOCK: c_uchar = 12;
+pub const DT_WHT: c_uchar = 14;
+
+pub type S_DIR = c_int;
+
+extern "C" {
+    pub fn SOLID_FS_Open(fd: *mut c_int, path: *const c_char, mode: c_int) -> c_int;
+    pub fn SOLID_FS_Close(fd: c_int) -> c_int;
+    pub fn SOLID_FS_Read(fd: c_int, buf: *mut u8, size: usize, result: *mut usize) -> c_int;
+    pub fn SOLID_FS_Write(fd: c_int, buf: *const u8, size: usize, result: *mut usize) -> c_int;
+    pub fn SOLID_FS_Lseek(fd: c_int, offset: off_t, whence: c_int) -> c_int;
+    pub fn SOLID_FS_Sync(fd: c_int) -> c_int;
+    pub fn SOLID_FS_Ftell(fd: c_int, result: *mut off_t) -> c_int;
+    pub fn SOLID_FS_Feof(fd: c_int, result: *mut c_int) -> c_int;
+    pub fn SOLID_FS_Fsize(fd: c_int, result: *mut usize) -> c_int;
+    pub fn SOLID_FS_Truncate(path: *const c_char, size: off_t) -> c_int;
+    pub fn SOLID_FS_OpenDir(path: *const c_char, pDir: *mut S_DIR) -> c_int;
+    pub fn SOLID_FS_CloseDir(dir: S_DIR) -> c_int;
+    pub fn SOLID_FS_ReadDir(dir: S_DIR, dirp: *mut dirent) -> c_int;
+    pub fn SOLID_FS_Stat(path: *const c_char, buf: *mut stat) -> c_int;
+    pub fn SOLID_FS_Unlink(path: *const c_char) -> c_int;
+    pub fn SOLID_FS_Rename(oldpath: *const c_char, newpath: *const c_char) -> c_int;
+    pub fn SOLID_FS_Chmod(path: *const c_char, mode: c_int) -> c_int;
+    pub fn SOLID_FS_Utime(path: *const c_char, time: time_t) -> c_int;
+    pub fn SOLID_FS_Mkdir(path: *const c_char) -> c_int;
+}
diff --git a/library/std/src/sys/solid/abi/mod.rs b/library/std/src/sys/solid/abi/mod.rs
new file mode 100644
index 00000000000..3526440fb85
--- /dev/null
+++ b/library/std/src/sys/solid/abi/mod.rs
@@ -0,0 +1,92 @@
+use crate::os::raw::c_int;
+
+mod fs;
+pub mod sockets;
+pub use self::fs::*;
+
+pub const SOLID_BP_PROGRAM_EXITED: usize = 15;
+pub const SOLID_BP_CSABORT: usize = 16;
+
+#[inline(always)]
+pub fn breakpoint_program_exited(tid: usize) {
+    unsafe {
+        match () {
+            #[cfg(target_arch = "arm")]
+            () => asm!("bkpt #{}", const SOLID_BP_PROGRAM_EXITED, in("r0") tid),
+            #[cfg(target_arch = "aarch64")]
+            () => asm!("hlt #{}", const SOLID_BP_PROGRAM_EXITED, in("x0") tid),
+        }
+    }
+}
+
+#[inline(always)]
+pub fn breakpoint_abort() {
+    unsafe {
+        match () {
+            #[cfg(target_arch = "arm")]
+            () => asm!("bkpt #{}", const SOLID_BP_CSABORT),
+            #[cfg(target_arch = "aarch64")]
+            () => asm!("hlt #{}", const SOLID_BP_CSABORT),
+        }
+    }
+}
+
+// `solid_types.h`
+pub use super::itron::abi::{ER, ER_ID, E_TMOUT, ID};
+
+pub const SOLID_ERR_NOTFOUND: ER = -1000;
+pub const SOLID_ERR_NOTSUPPORTED: ER = -1001;
+pub const SOLID_ERR_EBADF: ER = -1002;
+pub const SOLID_ERR_INVALIDCONTENT: ER = -1003;
+pub const SOLID_ERR_NOTUSED: ER = -1004;
+pub const SOLID_ERR_ALREADYUSED: ER = -1005;
+pub const SOLID_ERR_OUTOFBOUND: ER = -1006;
+pub const SOLID_ERR_BADSEQUENCE: ER = -1007;
+pub const SOLID_ERR_UNKNOWNDEVICE: ER = -1008;
+pub const SOLID_ERR_BUSY: ER = -1009;
+pub const SOLID_ERR_TIMEOUT: ER = -1010;
+pub const SOLID_ERR_INVALIDACCESS: ER = -1011;
+pub const SOLID_ERR_NOTREADY: ER = -1012;
+
+// `solid_rtc.h`
+#[repr(C)]
+#[derive(Debug, Copy, Clone)]
+pub struct SOLID_RTC_TIME {
+    pub tm_sec: c_int,
+    pub tm_min: c_int,
+    pub tm_hour: c_int,
+    pub tm_mday: c_int,
+    pub tm_mon: c_int,
+    pub tm_year: c_int,
+    pub tm_wday: c_int,
+}
+
+extern "C" {
+    pub fn SOLID_RTC_ReadTime(time: *mut SOLID_RTC_TIME) -> c_int;
+}
+
+// `solid_log.h`
+extern "C" {
+    pub fn SOLID_LOG_write(s: *const u8, l: usize);
+}
+
+// `solid_mem.h`
+extern "C" {
+    pub fn SOLID_TLS_AddDestructor(id: i32, dtor: unsafe extern "C" fn(*mut u8));
+}
+
+// `solid_rng.h`
+extern "C" {
+    pub fn SOLID_RNG_SampleRandomBytes(buffer: *mut u8, length: usize) -> c_int;
+}
+
+// `rwlock.h`
+extern "C" {
+    pub fn rwl_loc_rdl(id: ID) -> ER;
+    pub fn rwl_loc_wrl(id: ID) -> ER;
+    pub fn rwl_ploc_rdl(id: ID) -> ER;
+    pub fn rwl_ploc_wrl(id: ID) -> ER;
+    pub fn rwl_unl_rwl(id: ID) -> ER;
+    pub fn rwl_acre_rwl() -> ER_ID;
+    pub fn rwl_del_rwl(id: ID) -> ER;
+}
diff --git a/library/std/src/sys/solid/abi/sockets.rs b/library/std/src/sys/solid/abi/sockets.rs
new file mode 100644
index 00000000000..7c21d0dd25e
--- /dev/null
+++ b/library/std/src/sys/solid/abi/sockets.rs
@@ -0,0 +1,274 @@
+use crate::os::raw::{c_char, c_uint, c_void};
+pub use libc::{c_int, c_long, size_t, ssize_t, suseconds_t, time_t, timeval};
+
+pub const SOLID_NET_ERR_BASE: c_int = -2000;
+pub const EINPROGRESS: c_int = SOLID_NET_ERR_BASE - libc::EINPROGRESS;
+
+pub const AF_INET6: i32 = 10;
+pub const AF_INET: i32 = 2;
+pub const IPPROTO_IP: i32 = 0;
+pub const IPPROTO_IPV6: i32 = 41;
+pub const IPPROTO_TCP: i32 = 6;
+pub const IPV6_ADD_MEMBERSHIP: i32 = 12;
+pub const IPV6_DROP_MEMBERSHIP: i32 = 13;
+pub const IPV6_MULTICAST_LOOP: i32 = 19;
+pub const IPV6_V6ONLY: i32 = 27;
+pub const IP_TTL: i32 = 2;
+pub const IP_MULTICAST_TTL: i32 = 5;
+pub const IP_MULTICAST_LOOP: i32 = 7;
+pub const IP_ADD_MEMBERSHIP: i32 = 3;
+pub const IP_DROP_MEMBERSHIP: i32 = 4;
+pub const SHUT_RD: i32 = 0;
+pub const SHUT_RDWR: i32 = 2;
+pub const SHUT_WR: i32 = 1;
+pub const SOCK_DGRAM: i32 = 2;
+pub const SOCK_STREAM: i32 = 1;
+pub const SOL_SOCKET: i32 = 4095;
+pub const SO_BROADCAST: i32 = 32;
+pub const SO_ERROR: i32 = 4103;
+pub const SO_RCVTIMEO: i32 = 4102;
+pub const SO_REUSEADDR: i32 = 4;
+pub const SO_SNDTIMEO: i32 = 4101;
+pub const SO_LINGER: i32 = 128;
+pub const TCP_NODELAY: i32 = 1;
+pub const MSG_PEEK: c_int = 1;
+pub const FIONBIO: c_long = 0x8008667eu32 as c_long;
+pub const EAI_NONAME: i32 = -2200;
+pub const EAI_SERVICE: i32 = -2201;
+pub const EAI_FAIL: i32 = -2202;
+pub const EAI_MEMORY: i32 = -2203;
+pub const EAI_FAMILY: i32 = -2204;
+
+pub type sa_family_t = u8;
+pub type socklen_t = u32;
+pub type in_addr_t = u32;
+pub type in_port_t = u16;
+
+#[repr(C)]
+#[derive(Debug, Copy, Clone)]
+pub struct in_addr {
+    pub s_addr: in_addr_t,
+}
+
+#[repr(C)]
+#[derive(Debug, Copy, Clone)]
+pub struct in6_addr {
+    pub s6_addr: [u8; 16],
+}
+
+#[repr(C)]
+#[derive(Debug, Copy, Clone)]
+pub struct ip_mreq {
+    pub imr_multiaddr: in_addr,
+    pub imr_interface: in_addr,
+}
+
+#[repr(C)]
+#[derive(Debug, Copy, Clone)]
+pub struct ipv6_mreq {
+    pub ipv6mr_multiaddr: in6_addr,
+    pub ipv6mr_interface: c_uint,
+}
+
+#[repr(C)]
+#[derive(Debug, Copy, Clone)]
+pub struct msghdr {
+    pub msg_name: *mut c_void,
+    pub msg_namelen: socklen_t,
+    pub msg_iov: *mut iovec,
+    pub msg_iovlen: c_int,
+    pub msg_control: *mut c_void,
+    pub msg_controllen: socklen_t,
+    pub msg_flags: c_int,
+}
+
+#[repr(C)]
+#[derive(Debug, Copy, Clone)]
+pub struct sockaddr {
+    pub sa_len: u8,
+    pub sa_family: sa_family_t,
+    pub sa_data: [c_char; 14usize],
+}
+
+#[repr(C)]
+#[derive(Debug, Copy, Clone)]
+pub struct sockaddr_in {
+    pub sin_len: u8,
+    pub sin_family: sa_family_t,
+    pub sin_port: in_port_t,
+    pub sin_addr: in_addr,
+    pub sin_zero: [c_char; 8usize],
+}
+
+#[repr(C)]
+#[derive(Copy, Clone)]
+pub struct sockaddr_in6 {
+    pub sin6_len: u8,
+    pub sin6_family: sa_family_t,
+    pub sin6_port: in_port_t,
+    pub sin6_flowinfo: u32,
+    pub sin6_addr: in6_addr,
+    pub sin6_scope_id: u32,
+}
+
+#[repr(C)]
+#[derive(Debug, Copy, Clone)]
+pub struct sockaddr_storage {
+    pub s2_len: u8,
+    pub ss_family: sa_family_t,
+    pub s2_data1: [c_char; 2usize],
+    pub s2_data2: [u32; 3usize],
+}
+
+#[repr(C)]
+#[derive(Debug, Copy, Clone)]
+pub struct addrinfo {
+    pub ai_flags: c_int,
+    pub ai_family: c_int,
+    pub ai_socktype: c_int,
+    pub ai_protocol: c_int,
+    pub ai_addrlen: socklen_t,
+    pub ai_addr: *mut sockaddr,
+    pub ai_canonname: *mut c_char,
+    pub ai_next: *mut addrinfo,
+}
+
+#[repr(C)]
+#[derive(Debug, Copy, Clone)]
+pub struct linger {
+    pub l_onoff: c_int,
+    pub l_linger: c_int,
+}
+
+#[repr(C)]
+#[derive(Debug, Copy, Clone)]
+pub struct iovec {
+    pub iov_base: *mut c_void,
+    pub iov_len: usize,
+}
+
+/// This value can be chosen by an application
+pub const SOLID_NET_FD_SETSIZE: usize = 1;
+
+#[repr(C)]
+#[derive(Debug, Copy, Clone)]
+pub struct fd_set {
+    pub num_fds: usize,
+    pub fds: [c_int; SOLID_NET_FD_SETSIZE],
+}
+
+extern "C" {
+    #[link_name = "SOLID_NET_StrError"]
+    pub fn strerror(errnum: c_int) -> *const c_char;
+
+    pub fn SOLID_NET_GetLastError() -> c_int;
+
+    #[link_name = "SOLID_NET_Accept"]
+    pub fn accept(s: c_int, addr: *mut sockaddr, addrlen: *mut socklen_t) -> c_int;
+
+    #[link_name = "SOLID_NET_Bind"]
+    pub fn bind(s: c_int, name: *const sockaddr, namelen: socklen_t) -> c_int;
+
+    #[link_name = "SOLID_NET_Connect"]
+    pub fn connect(s: c_int, name: *const sockaddr, namelen: socklen_t) -> c_int;
+
+    #[link_name = "SOLID_NET_Close"]
+    pub fn close(s: c_int) -> c_int;
+
+    #[link_name = "SOLID_NET_GetPeerName"]
+    pub fn getpeername(s: c_int, name: *mut sockaddr, namelen: *mut socklen_t) -> c_int;
+
+    #[link_name = "SOLID_NET_GetSockName"]
+    pub fn getsockname(s: c_int, name: *mut sockaddr, namelen: *mut socklen_t) -> c_int;
+
+    #[link_name = "SOLID_NET_GetSockOpt"]
+    pub fn getsockopt(
+        s: c_int,
+        level: c_int,
+        optname: c_int,
+        optval: *mut c_void,
+        optlen: *mut socklen_t,
+    ) -> c_int;
+
+    #[link_name = "SOLID_NET_SetSockOpt"]
+    pub fn setsockopt(
+        s: c_int,
+        level: c_int,
+        optname: c_int,
+        optval: *const c_void,
+        optlen: socklen_t,
+    ) -> c_int;
+
+    #[link_name = "SOLID_NET_Ioctl"]
+    pub fn ioctl(s: c_int, cmd: c_long, argp: *mut c_void) -> c_int;
+
+    #[link_name = "SOLID_NET_Listen"]
+    pub fn listen(s: c_int, backlog: c_int) -> c_int;
+
+    #[link_name = "SOLID_NET_Recv"]
+    pub fn recv(s: c_int, mem: *mut c_void, len: size_t, flags: c_int) -> ssize_t;
+
+    #[link_name = "SOLID_NET_Read"]
+    pub fn read(s: c_int, mem: *mut c_void, len: size_t) -> ssize_t;
+
+    #[link_name = "SOLID_NET_Readv"]
+    pub fn readv(s: c_int, bufs: *const iovec, bufcnt: c_int) -> ssize_t;
+
+    #[link_name = "SOLID_NET_RecvFrom"]
+    pub fn recvfrom(
+        s: c_int,
+        mem: *mut c_void,
+        len: size_t,
+        flags: c_int,
+        from: *mut sockaddr,
+        fromlen: *mut socklen_t,
+    ) -> ssize_t;
+
+    #[link_name = "SOLID_NET_Send"]
+    pub fn send(s: c_int, mem: *const c_void, len: size_t, flags: c_int) -> ssize_t;
+
+    #[link_name = "SOLID_NET_SendMsg"]
+    pub fn sendmsg(s: c_int, message: *const msghdr, flags: c_int) -> ssize_t;
+
+    #[link_name = "SOLID_NET_SendTo"]
+    pub fn sendto(
+        s: c_int,
+        mem: *const c_void,
+        len: size_t,
+        flags: c_int,
+        to: *const sockaddr,
+        tolen: socklen_t,
+    ) -> ssize_t;
+
+    #[link_name = "SOLID_NET_Shutdown"]
+    pub fn shutdown(s: c_int, how: c_int) -> c_int;
+
+    #[link_name = "SOLID_NET_Socket"]
+    pub fn socket(domain: c_int, type_: c_int, protocol: c_int) -> c_int;
+
+    #[link_name = "SOLID_NET_Write"]
+    pub fn write(s: c_int, mem: *const c_void, len: size_t) -> ssize_t;
+
+    #[link_name = "SOLID_NET_Writev"]
+    pub fn writev(s: c_int, bufs: *const iovec, bufcnt: c_int) -> ssize_t;
+
+    #[link_name = "SOLID_NET_FreeAddrInfo"]
+    pub fn freeaddrinfo(ai: *mut addrinfo);
+
+    #[link_name = "SOLID_NET_GetAddrInfo"]
+    pub fn getaddrinfo(
+        nodename: *const c_char,
+        servname: *const c_char,
+        hints: *const addrinfo,
+        res: *mut *mut addrinfo,
+    ) -> c_int;
+
+    #[link_name = "SOLID_NET_Select"]
+    pub fn select(
+        maxfdp1: c_int,
+        readset: *mut fd_set,
+        writeset: *mut fd_set,
+        exceptset: *mut fd_set,
+        timeout: *mut timeval,
+    ) -> c_int;
+}
diff --git a/library/std/src/sys/solid/alloc.rs b/library/std/src/sys/solid/alloc.rs
new file mode 100644
index 00000000000..d013bd87610
--- /dev/null
+++ b/library/std/src/sys/solid/alloc.rs
@@ -0,0 +1,32 @@
+use crate::{
+    alloc::{GlobalAlloc, Layout, System},
+    sys::common::alloc::{realloc_fallback, MIN_ALIGN},
+};
+
+#[stable(feature = "alloc_system_type", since = "1.28.0")]
+unsafe impl GlobalAlloc for System {
+    #[inline]
+    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
+        if layout.align() <= MIN_ALIGN && layout.align() <= layout.size() {
+            unsafe { libc::malloc(layout.size()) as *mut u8 }
+        } else {
+            unsafe { libc::memalign(layout.align(), layout.size()) as *mut u8 }
+        }
+    }
+
+    #[inline]
+    unsafe fn dealloc(&self, ptr: *mut u8, _layout: Layout) {
+        unsafe { libc::free(ptr as *mut libc::c_void) }
+    }
+
+    #[inline]
+    unsafe fn realloc(&self, ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8 {
+        unsafe {
+            if layout.align() <= MIN_ALIGN && layout.align() <= new_size {
+                libc::realloc(ptr as *mut libc::c_void, new_size) as *mut u8
+            } else {
+                realloc_fallback(self, ptr, layout, new_size)
+            }
+        }
+    }
+}
diff --git a/library/std/src/sys/solid/env.rs b/library/std/src/sys/solid/env.rs
new file mode 100644
index 00000000000..6855c113b28
--- /dev/null
+++ b/library/std/src/sys/solid/env.rs
@@ -0,0 +1,9 @@
+pub mod os {
+    pub const FAMILY: &str = "itron";
+    pub const OS: &str = "solid";
+    pub const DLL_PREFIX: &str = "";
+    pub const DLL_SUFFIX: &str = ".so";
+    pub const DLL_EXTENSION: &str = "so";
+    pub const EXE_SUFFIX: &str = "";
+    pub const EXE_EXTENSION: &str = "";
+}
diff --git a/library/std/src/sys/solid/error.rs b/library/std/src/sys/solid/error.rs
new file mode 100644
index 00000000000..547b4f3a984
--- /dev/null
+++ b/library/std/src/sys/solid/error.rs
@@ -0,0 +1,55 @@
+use super::{abi, itron, net};
+use crate::io::ErrorKind;
+
+pub use self::itron::error::{expect_success, ItronError as SolidError};
+
+/// Describe the specified SOLID error code. Returns `None` if it's an
+/// undefined error code.
+///
+/// The SOLID error codes are a superset of μITRON error codes.
+pub fn error_name(er: abi::ER) -> Option<&'static str> {
+    match er {
+        // Success
+        er if er >= 0 => None,
+        er if er < abi::sockets::SOLID_NET_ERR_BASE => net::error_name(er),
+
+        abi::SOLID_ERR_NOTFOUND => Some("not found"),
+        abi::SOLID_ERR_NOTSUPPORTED => Some("not supported"),
+        abi::SOLID_ERR_EBADF => Some("bad flags"),
+        abi::SOLID_ERR_INVALIDCONTENT => Some("invalid content"),
+        abi::SOLID_ERR_NOTUSED => Some("not used"),
+        abi::SOLID_ERR_ALREADYUSED => Some("already used"),
+        abi::SOLID_ERR_OUTOFBOUND => Some("out of bounds"),
+        abi::SOLID_ERR_BADSEQUENCE => Some("bad sequence"),
+        abi::SOLID_ERR_UNKNOWNDEVICE => Some("unknown device"),
+        abi::SOLID_ERR_BUSY => Some("busy"),
+        abi::SOLID_ERR_TIMEOUT => Some("operation timed out"),
+        abi::SOLID_ERR_INVALIDACCESS => Some("invalid access"),
+        abi::SOLID_ERR_NOTREADY => Some("not ready"),
+
+        _ => itron::error::error_name(er),
+    }
+}
+
+pub fn decode_error_kind(er: abi::ER) -> ErrorKind {
+    match er {
+        // Success
+        er if er >= 0 => ErrorKind::Uncategorized,
+        er if er < abi::sockets::SOLID_NET_ERR_BASE => net::decode_error_kind(er),
+
+        abi::SOLID_ERR_NOTFOUND => ErrorKind::NotFound,
+        abi::SOLID_ERR_NOTSUPPORTED => ErrorKind::Unsupported,
+        abi::SOLID_ERR_EBADF => ErrorKind::InvalidInput,
+        abi::SOLID_ERR_INVALIDCONTENT => ErrorKind::InvalidData,
+        // abi::SOLID_ERR_NOTUSED
+        // abi::SOLID_ERR_ALREADYUSED
+        abi::SOLID_ERR_OUTOFBOUND => ErrorKind::InvalidInput,
+        // abi::SOLID_ERR_BADSEQUENCE
+        abi::SOLID_ERR_UNKNOWNDEVICE => ErrorKind::NotFound,
+        // abi::SOLID_ERR_BUSY
+        abi::SOLID_ERR_TIMEOUT => ErrorKind::TimedOut,
+        // abi::SOLID_ERR_INVALIDACCESS
+        // abi::SOLID_ERR_NOTREADY
+        _ => itron::error::decode_error_kind(er),
+    }
+}
diff --git a/library/std/src/sys/solid/fs.rs b/library/std/src/sys/solid/fs.rs
new file mode 100644
index 00000000000..abc60b56fbb
--- /dev/null
+++ b/library/std/src/sys/solid/fs.rs
@@ -0,0 +1,529 @@
+use super::{abi, error};
+use crate::{
+    ffi::{CStr, CString, OsStr, OsString},
+    fmt,
+    io::{self, IoSlice, IoSliceMut, SeekFrom},
+    mem::MaybeUninit,
+    os::raw::{c_int, c_short},
+    os::solid::ffi::OsStrExt,
+    path::{Path, PathBuf},
+    sync::Arc,
+    sys::time::SystemTime,
+    sys::unsupported,
+};
+
+pub use crate::sys_common::fs::try_exists;
+
+/// A file descriptor.
+#[derive(Clone, Copy)]
+#[rustc_layout_scalar_valid_range_start(0)]
+// libstd/os/raw/mod.rs assures me that every libstd-supported platform has a
+// 32-bit c_int. Below is -2, in two's complement, but that only works out
+// because c_int is 32 bits.
+#[rustc_layout_scalar_valid_range_end(0xFF_FF_FF_FE)]
+struct FileDesc {
+    fd: c_int,
+}
+
+impl FileDesc {
+    #[inline]
+    fn new(fd: c_int) -> FileDesc {
+        assert_ne!(fd, -1i32);
+        // Safety: we just asserted that the value is in the valid range and
+        // isn't `-1` (the only value bigger than `0xFF_FF_FF_FE` unsigned)
+        unsafe { FileDesc { fd } }
+    }
+
+    #[inline]
+    fn raw(&self) -> c_int {
+        self.fd
+    }
+}
+
+pub struct File {
+    fd: FileDesc,
+}
+
+#[derive(Clone)]
+pub struct FileAttr {
+    stat: abi::stat,
+}
+
+// all DirEntry's will have a reference to this struct
+struct InnerReadDir {
+    dirp: abi::S_DIR,
+    root: PathBuf,
+}
+
+pub struct ReadDir {
+    inner: Arc<InnerReadDir>,
+}
+
+pub struct DirEntry {
+    entry: abi::dirent,
+    inner: Arc<InnerReadDir>,
+}
+
+#[derive(Clone, Debug)]
+pub struct OpenOptions {
+    // generic
+    read: bool,
+    write: bool,
+    append: bool,
+    truncate: bool,
+    create: bool,
+    create_new: bool,
+    // system-specific
+    custom_flags: i32,
+}
+
+#[derive(Clone, PartialEq, Eq, Debug)]
+pub struct FilePermissions(c_short);
+
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
+pub struct FileType(c_short);
+
+#[derive(Debug)]
+pub struct DirBuilder {}
+
+impl FileAttr {
+    pub fn size(&self) -> u64 {
+        self.stat.st_size as u64
+    }
+
+    pub fn perm(&self) -> FilePermissions {
+        FilePermissions(self.stat.st_mode)
+    }
+
+    pub fn file_type(&self) -> FileType {
+        FileType(self.stat.st_mode)
+    }
+
+    pub fn modified(&self) -> io::Result<SystemTime> {
+        Ok(SystemTime::from_time_t(self.stat.st_mtime))
+    }
+
+    pub fn accessed(&self) -> io::Result<SystemTime> {
+        Ok(SystemTime::from_time_t(self.stat.st_atime))
+    }
+
+    pub fn created(&self) -> io::Result<SystemTime> {
+        Ok(SystemTime::from_time_t(self.stat.st_ctime))
+    }
+}
+
+impl FilePermissions {
+    pub fn readonly(&self) -> bool {
+        (self.0 & abi::S_IWRITE) == 0
+    }
+
+    pub fn set_readonly(&mut self, readonly: bool) {
+        if readonly {
+            self.0 &= !abi::S_IWRITE;
+        } else {
+            self.0 |= abi::S_IWRITE;
+        }
+    }
+}
+
+impl FileType {
+    pub fn is_dir(&self) -> bool {
+        self.is(abi::S_IFDIR)
+    }
+    pub fn is_file(&self) -> bool {
+        self.is(abi::S_IFREG)
+    }
+    pub fn is_symlink(&self) -> bool {
+        false
+    }
+
+    pub fn is(&self, mode: c_short) -> bool {
+        self.0 & abi::S_IFMT == mode
+    }
+}
+
+pub fn readdir(p: &Path) -> io::Result<ReadDir> {
+    unsafe {
+        let mut dir = MaybeUninit::uninit();
+        error::SolidError::err_if_negative(abi::SOLID_FS_OpenDir(
+            cstr(p)?.as_ptr(),
+            dir.as_mut_ptr(),
+        ))
+        .map_err(|e| e.as_io_error())?;
+        let inner = Arc::new(InnerReadDir { dirp: dir.assume_init(), root: p.to_owned() });
+        Ok(ReadDir { inner })
+    }
+}
+
+impl fmt::Debug for ReadDir {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        // This will only be called from std::fs::ReadDir, which will add a "ReadDir()" frame.
+        // Thus the result will be e g 'ReadDir("/home")'
+        fmt::Debug::fmt(&*self.inner.root, f)
+    }
+}
+
+impl Iterator for ReadDir {
+    type Item = io::Result<DirEntry>;
+
+    fn next(&mut self) -> Option<io::Result<DirEntry>> {
+        unsafe {
+            let mut out_dirent = MaybeUninit::uninit();
+            error::SolidError::err_if_negative(abi::SOLID_FS_ReadDir(
+                self.inner.dirp,
+                out_dirent.as_mut_ptr(),
+            ))
+            .ok()?;
+            Some(Ok(DirEntry { entry: out_dirent.assume_init(), inner: Arc::clone(&self.inner) }))
+        }
+    }
+}
+
+impl Drop for InnerReadDir {
+    fn drop(&mut self) {
+        unsafe { abi::SOLID_FS_CloseDir(self.dirp) };
+    }
+}
+
+impl DirEntry {
+    pub fn path(&self) -> PathBuf {
+        self.inner.root.join(OsStr::from_bytes(
+            unsafe { CStr::from_ptr(self.entry.d_name.as_ptr()) }.to_bytes(),
+        ))
+    }
+
+    pub fn file_name(&self) -> OsString {
+        OsStr::from_bytes(unsafe { CStr::from_ptr(self.entry.d_name.as_ptr()) }.to_bytes())
+            .to_os_string()
+    }
+
+    pub fn metadata(&self) -> io::Result<FileAttr> {
+        lstat(&self.path())
+    }
+
+    pub fn file_type(&self) -> io::Result<FileType> {
+        match self.entry.d_type {
+            abi::DT_CHR => Ok(FileType(abi::S_IFCHR)),
+            abi::DT_FIFO => Ok(FileType(abi::S_IFIFO)),
+            abi::DT_REG => Ok(FileType(abi::S_IFREG)),
+            abi::DT_DIR => Ok(FileType(abi::S_IFDIR)),
+            abi::DT_BLK => Ok(FileType(abi::S_IFBLK)),
+            _ => lstat(&self.path()).map(|m| m.file_type()),
+        }
+    }
+}
+
+impl OpenOptions {
+    pub fn new() -> OpenOptions {
+        OpenOptions {
+            // generic
+            read: false,
+            write: false,
+            append: false,
+            truncate: false,
+            create: false,
+            create_new: false,
+            // system-specific
+            custom_flags: 0,
+        }
+    }
+
+    pub fn read(&mut self, read: bool) {
+        self.read = read;
+    }
+    pub fn write(&mut self, write: bool) {
+        self.write = write;
+    }
+    pub fn append(&mut self, append: bool) {
+        self.append = append;
+    }
+    pub fn truncate(&mut self, truncate: bool) {
+        self.truncate = truncate;
+    }
+    pub fn create(&mut self, create: bool) {
+        self.create = create;
+    }
+    pub fn create_new(&mut self, create_new: bool) {
+        self.create_new = create_new;
+    }
+
+    pub fn custom_flags(&mut self, flags: i32) {
+        self.custom_flags = flags;
+    }
+    pub fn mode(&mut self, _mode: u32) {}
+
+    fn get_access_mode(&self) -> io::Result<c_int> {
+        match (self.read, self.write, self.append) {
+            (true, false, false) => Ok(abi::O_RDONLY),
+            (false, true, false) => Ok(abi::O_WRONLY),
+            (true, true, false) => Ok(abi::O_RDWR),
+            (false, _, true) => Ok(abi::O_WRONLY | abi::O_APPEND),
+            (true, _, true) => Ok(abi::O_RDWR | abi::O_APPEND),
+            (false, false, false) => Err(io::Error::from_raw_os_error(libc::EINVAL)),
+        }
+    }
+
+    fn get_creation_mode(&self) -> io::Result<c_int> {
+        match (self.write, self.append) {
+            (true, false) => {}
+            (false, false) => {
+                if self.truncate || self.create || self.create_new {
+                    return Err(io::Error::from_raw_os_error(libc::EINVAL));
+                }
+            }
+            (_, true) => {
+                if self.truncate && !self.create_new {
+                    return Err(io::Error::from_raw_os_error(libc::EINVAL));
+                }
+            }
+        }
+
+        Ok(match (self.create, self.truncate, self.create_new) {
+            (false, false, false) => 0,
+            (true, false, false) => abi::O_CREAT,
+            (false, true, false) => abi::O_TRUNC,
+            (true, true, false) => abi::O_CREAT | abi::O_TRUNC,
+            (_, _, true) => abi::O_CREAT | abi::O_EXCL,
+        })
+    }
+}
+
+fn cstr(path: &Path) -> io::Result<CString> {
+    Ok(CString::new(path.as_os_str().as_bytes())?)
+}
+
+impl File {
+    pub fn open(path: &Path, opts: &OpenOptions) -> io::Result<File> {
+        let flags = opts.get_access_mode()?
+            | opts.get_creation_mode()?
+            | (opts.custom_flags as c_int & !abi::O_ACCMODE);
+        unsafe {
+            let mut fd = MaybeUninit::uninit();
+            error::SolidError::err_if_negative(abi::SOLID_FS_Open(
+                fd.as_mut_ptr(),
+                cstr(path)?.as_ptr(),
+                flags,
+            ))
+            .map_err(|e| e.as_io_error())?;
+            Ok(File { fd: FileDesc::new(fd.assume_init()) })
+        }
+    }
+
+    pub fn file_attr(&self) -> io::Result<FileAttr> {
+        unsupported()
+    }
+
+    pub fn fsync(&self) -> io::Result<()> {
+        self.flush()
+    }
+
+    pub fn datasync(&self) -> io::Result<()> {
+        self.flush()
+    }
+
+    pub fn truncate(&self, _size: u64) -> io::Result<()> {
+        unsupported()
+    }
+
+    pub fn read(&self, buf: &mut [u8]) -> io::Result<usize> {
+        unsafe {
+            let mut out_num_bytes = MaybeUninit::uninit();
+            error::SolidError::err_if_negative(abi::SOLID_FS_Read(
+                self.fd.raw(),
+                buf.as_mut_ptr(),
+                buf.len(),
+                out_num_bytes.as_mut_ptr(),
+            ))
+            .map_err(|e| e.as_io_error())?;
+            Ok(out_num_bytes.assume_init())
+        }
+    }
+
+    pub fn read_vectored(&self, bufs: &mut [IoSliceMut<'_>]) -> io::Result<usize> {
+        crate::io::default_read_vectored(|buf| self.read(buf), bufs)
+    }
+
+    pub fn is_read_vectored(&self) -> bool {
+        false
+    }
+
+    pub fn write(&self, buf: &[u8]) -> io::Result<usize> {
+        unsafe {
+            let mut out_num_bytes = MaybeUninit::uninit();
+            error::SolidError::err_if_negative(abi::SOLID_FS_Write(
+                self.fd.raw(),
+                buf.as_ptr(),
+                buf.len(),
+                out_num_bytes.as_mut_ptr(),
+            ))
+            .map_err(|e| e.as_io_error())?;
+            Ok(out_num_bytes.assume_init())
+        }
+    }
+
+    pub fn write_vectored(&self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
+        crate::io::default_write_vectored(|buf| self.write(buf), bufs)
+    }
+
+    pub fn is_write_vectored(&self) -> bool {
+        false
+    }
+
+    pub fn flush(&self) -> io::Result<()> {
+        error::SolidError::err_if_negative(unsafe { abi::SOLID_FS_Sync(self.fd.raw()) })
+            .map_err(|e| e.as_io_error())?;
+        Ok(())
+    }
+
+    pub fn seek(&self, pos: SeekFrom) -> io::Result<u64> {
+        let (whence, pos) = match pos {
+            // Casting to `i64` is fine, too large values will end up as
+            // negative which will cause an error in `SOLID_FS_Lseek`.
+            SeekFrom::Start(off) => (abi::SEEK_SET, off as i64),
+            SeekFrom::End(off) => (abi::SEEK_END, off),
+            SeekFrom::Current(off) => (abi::SEEK_CUR, off),
+        };
+        error::SolidError::err_if_negative(unsafe {
+            abi::SOLID_FS_Lseek(self.fd.raw(), pos, whence)
+        })
+        .map_err(|e| e.as_io_error())?;
+
+        // Get the new offset
+        unsafe {
+            let mut out_offset = MaybeUninit::uninit();
+            error::SolidError::err_if_negative(abi::SOLID_FS_Ftell(
+                self.fd.raw(),
+                out_offset.as_mut_ptr(),
+            ))
+            .map_err(|e| e.as_io_error())?;
+            Ok(out_offset.assume_init() as u64)
+        }
+    }
+
+    pub fn duplicate(&self) -> io::Result<File> {
+        unsupported()
+    }
+
+    pub fn set_permissions(&self, _perm: FilePermissions) -> io::Result<()> {
+        unsupported()
+    }
+}
+
+impl Drop for File {
+    fn drop(&mut self) {
+        unsafe { abi::SOLID_FS_Close(self.fd.raw()) };
+    }
+}
+
+impl DirBuilder {
+    pub fn new() -> DirBuilder {
+        DirBuilder {}
+    }
+
+    pub fn mkdir(&self, p: &Path) -> io::Result<()> {
+        error::SolidError::err_if_negative(unsafe { abi::SOLID_FS_Mkdir(cstr(p)?.as_ptr()) })
+            .map_err(|e| e.as_io_error())?;
+        Ok(())
+    }
+}
+
+impl fmt::Debug for File {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("File").field("fd", &self.fd.raw()).finish()
+    }
+}
+
+pub fn unlink(p: &Path) -> io::Result<()> {
+    if stat(p)?.file_type().is_dir() {
+        Err(io::Error::new_const(io::ErrorKind::IsADirectory, &"is a directory"))
+    } else {
+        error::SolidError::err_if_negative(unsafe { abi::SOLID_FS_Unlink(cstr(p)?.as_ptr()) })
+            .map_err(|e| e.as_io_error())?;
+        Ok(())
+    }
+}
+
+pub fn rename(old: &Path, new: &Path) -> io::Result<()> {
+    error::SolidError::err_if_negative(unsafe {
+        abi::SOLID_FS_Rename(cstr(old)?.as_ptr(), cstr(new)?.as_ptr())
+    })
+    .map_err(|e| e.as_io_error())?;
+    Ok(())
+}
+
+pub fn set_perm(p: &Path, perm: FilePermissions) -> io::Result<()> {
+    error::SolidError::err_if_negative(unsafe {
+        abi::SOLID_FS_Chmod(cstr(p)?.as_ptr(), perm.0.into())
+    })
+    .map_err(|e| e.as_io_error())?;
+    Ok(())
+}
+
+pub fn rmdir(p: &Path) -> io::Result<()> {
+    if stat(p)?.file_type().is_dir() {
+        error::SolidError::err_if_negative(unsafe { abi::SOLID_FS_Unlink(cstr(p)?.as_ptr()) })
+            .map_err(|e| e.as_io_error())?;
+        Ok(())
+    } else {
+        Err(io::Error::new_const(io::ErrorKind::NotADirectory, &"not a directory"))
+    }
+}
+
+pub fn remove_dir_all(path: &Path) -> io::Result<()> {
+    for child in readdir(path)? {
+        let child = child?;
+        let child_type = child.file_type()?;
+        if child_type.is_dir() {
+            remove_dir_all(&child.path())?;
+        } else {
+            unlink(&child.path())?;
+        }
+    }
+    rmdir(path)
+}
+
+pub fn readlink(p: &Path) -> io::Result<PathBuf> {
+    // This target doesn't support symlinks
+    stat(p)?;
+    Err(io::Error::new_const(io::ErrorKind::InvalidInput, &"not a symbolic link"))
+}
+
+pub fn symlink(_original: &Path, _link: &Path) -> io::Result<()> {
+    // This target doesn't support symlinks
+    unsupported()
+}
+
+pub fn link(_src: &Path, _dst: &Path) -> io::Result<()> {
+    // This target doesn't support symlinks
+    unsupported()
+}
+
+pub fn stat(p: &Path) -> io::Result<FileAttr> {
+    // This target doesn't support symlinks
+    lstat(p)
+}
+
+pub fn lstat(p: &Path) -> io::Result<FileAttr> {
+    unsafe {
+        let mut out_stat = MaybeUninit::uninit();
+        error::SolidError::err_if_negative(abi::SOLID_FS_Stat(
+            cstr(p)?.as_ptr(),
+            out_stat.as_mut_ptr(),
+        ))
+        .map_err(|e| e.as_io_error())?;
+        Ok(FileAttr { stat: out_stat.assume_init() })
+    }
+}
+
+pub fn canonicalize(_p: &Path) -> io::Result<PathBuf> {
+    unsupported()
+}
+
+pub fn copy(from: &Path, to: &Path) -> io::Result<u64> {
+    use crate::fs::File;
+
+    let mut reader = File::open(from)?;
+    let mut writer = File::create(to)?;
+
+    io::copy(&mut reader, &mut writer)
+}
diff --git a/library/std/src/sys/solid/io.rs b/library/std/src/sys/solid/io.rs
new file mode 100644
index 00000000000..9eb17a10daa
--- /dev/null
+++ b/library/std/src/sys/solid/io.rs
@@ -0,0 +1,77 @@
+use crate::marker::PhantomData;
+use crate::slice;
+
+use super::abi::sockets::iovec;
+use libc::c_void;
+
+#[derive(Copy, Clone)]
+#[repr(transparent)]
+pub struct IoSlice<'a> {
+    vec: iovec,
+    _p: PhantomData<&'a [u8]>,
+}
+
+impl<'a> IoSlice<'a> {
+    #[inline]
+    pub fn new(buf: &'a [u8]) -> IoSlice<'a> {
+        IoSlice {
+            vec: iovec { iov_base: buf.as_ptr() as *mut u8 as *mut c_void, iov_len: buf.len() },
+            _p: PhantomData,
+        }
+    }
+
+    #[inline]
+    pub fn advance(&mut self, n: usize) {
+        if self.vec.iov_len < n {
+            panic!("advancing IoSlice beyond its length");
+        }
+
+        unsafe {
+            self.vec.iov_len -= n;
+            self.vec.iov_base = self.vec.iov_base.add(n);
+        }
+    }
+
+    #[inline]
+    pub fn as_slice(&self) -> &[u8] {
+        unsafe { slice::from_raw_parts(self.vec.iov_base as *mut u8, self.vec.iov_len) }
+    }
+}
+
+#[repr(transparent)]
+pub struct IoSliceMut<'a> {
+    vec: iovec,
+    _p: PhantomData<&'a mut [u8]>,
+}
+
+impl<'a> IoSliceMut<'a> {
+    #[inline]
+    pub fn new(buf: &'a mut [u8]) -> IoSliceMut<'a> {
+        IoSliceMut {
+            vec: iovec { iov_base: buf.as_mut_ptr() as *mut c_void, iov_len: buf.len() },
+            _p: PhantomData,
+        }
+    }
+
+    #[inline]
+    pub fn advance(&mut self, n: usize) {
+        if self.vec.iov_len < n {
+            panic!("advancing IoSliceMut beyond its length");
+        }
+
+        unsafe {
+            self.vec.iov_len -= n;
+            self.vec.iov_base = self.vec.iov_base.add(n);
+        }
+    }
+
+    #[inline]
+    pub fn as_slice(&self) -> &[u8] {
+        unsafe { slice::from_raw_parts(self.vec.iov_base as *mut u8, self.vec.iov_len) }
+    }
+
+    #[inline]
+    pub fn as_mut_slice(&mut self) -> &mut [u8] {
+        unsafe { slice::from_raw_parts_mut(self.vec.iov_base as *mut u8, self.vec.iov_len) }
+    }
+}
diff --git a/library/std/src/sys/solid/memchr.rs b/library/std/src/sys/solid/memchr.rs
new file mode 100644
index 00000000000..452b7a3de1b
--- /dev/null
+++ b/library/std/src/sys/solid/memchr.rs
@@ -0,0 +1,21 @@
+pub fn memchr(needle: u8, haystack: &[u8]) -> Option<usize> {
+    let p = unsafe {
+        libc::memchr(
+            haystack.as_ptr() as *const libc::c_void,
+            needle as libc::c_int,
+            haystack.len(),
+        )
+    };
+    if p.is_null() { None } else { Some(p as usize - (haystack.as_ptr() as usize)) }
+}
+
+pub fn memrchr(needle: u8, haystack: &[u8]) -> Option<usize> {
+    let p = unsafe {
+        libc::memrchr(
+            haystack.as_ptr() as *const libc::c_void,
+            needle as libc::c_int,
+            haystack.len(),
+        )
+    };
+    if p.is_null() { None } else { Some(p as usize - (haystack.as_ptr() as usize)) }
+}
diff --git a/library/std/src/sys/solid/mod.rs b/library/std/src/sys/solid/mod.rs
new file mode 100644
index 00000000000..211b8d7de31
--- /dev/null
+++ b/library/std/src/sys/solid/mod.rs
@@ -0,0 +1,96 @@
+#![allow(dead_code)]
+#![allow(missing_docs, nonstandard_style)]
+#![deny(unsafe_op_in_unsafe_fn)]
+
+mod abi;
+
+#[path = "../itron"]
+mod itron {
+    pub(super) mod abi;
+    pub mod condvar;
+    pub(super) mod error;
+    pub mod mutex;
+    pub(super) mod spin;
+    pub(super) mod task;
+    pub mod thread;
+    pub(super) mod time;
+    use super::unsupported;
+}
+
+pub mod alloc;
+#[path = "../unsupported/args.rs"]
+pub mod args;
+#[path = "../unix/cmath.rs"]
+pub mod cmath;
+pub mod env;
+// `error` is `pub(crate)` so that it can be accessed by `itron/error.rs` as
+// `crate::sys::error`
+pub(crate) mod error;
+pub mod fs;
+pub mod io;
+pub mod net;
+pub mod os;
+#[path = "../unix/os_str.rs"]
+pub mod os_str;
+pub mod path;
+#[path = "../unsupported/pipe.rs"]
+pub mod pipe;
+#[path = "../unsupported/process.rs"]
+pub mod process;
+pub mod rwlock;
+pub mod stdio;
+pub use self::itron::{condvar, mutex, thread};
+pub mod memchr;
+pub mod thread_local_dtor;
+pub mod thread_local_key;
+pub mod time;
+
+// SAFETY: must be called only once during runtime initialization.
+// NOTE: this is not guaranteed to run, for example when Rust code is called externally.
+pub unsafe fn init(_argc: isize, _argv: *const *const u8) {}
+
+// SAFETY: must be called only once during runtime cleanup.
+pub unsafe fn cleanup() {}
+
+pub fn unsupported<T>() -> crate::io::Result<T> {
+    Err(unsupported_err())
+}
+
+pub fn unsupported_err() -> crate::io::Error {
+    crate::io::Error::new_const(
+        crate::io::ErrorKind::Unsupported,
+        &"operation not supported on this platform",
+    )
+}
+
+pub fn decode_error_kind(code: i32) -> crate::io::ErrorKind {
+    error::decode_error_kind(code)
+}
+
+#[inline(always)]
+pub fn abort_internal() -> ! {
+    loop {
+        abi::breakpoint_abort();
+    }
+}
+
+// This function is needed by the panic runtime. The symbol is named in
+// pre-link args for the target specification, so keep that in sync.
+#[cfg(not(test))]
+#[no_mangle]
+// NB. used by both libunwind and libpanic_abort
+pub extern "C" fn __rust_abort() {
+    abort_internal();
+}
+
+pub fn hashmap_random_keys() -> (u64, u64) {
+    unsafe {
+        let mut out = crate::mem::MaybeUninit::<[u64; 2]>::uninit();
+        let result = abi::SOLID_RNG_SampleRandomBytes(out.as_mut_ptr() as *mut u8, 16);
+        assert_eq!(result, 0, "SOLID_RNG_SampleRandomBytes failed: {}", result);
+        let [x1, x2] = out.assume_init();
+        (x1, x2)
+    }
+}
+
+pub use libc::strlen;
diff --git a/library/std/src/sys/solid/net.rs b/library/std/src/sys/solid/net.rs
new file mode 100644
index 00000000000..63ba6341c79
--- /dev/null
+++ b/library/std/src/sys/solid/net.rs
@@ -0,0 +1,469 @@
+use super::abi;
+use crate::{
+    cmp,
+    ffi::CStr,
+    io::{self, ErrorKind, IoSlice, IoSliceMut},
+    mem,
+    net::{Shutdown, SocketAddr},
+    ptr, str,
+    sys_common::net::{getsockopt, setsockopt, sockaddr_to_addr},
+    sys_common::{AsInner, FromInner, IntoInner},
+    time::Duration,
+};
+
+use self::netc::{sockaddr, socklen_t, MSG_PEEK};
+use libc::{c_int, c_void, size_t};
+
+pub mod netc {
+    pub use super::super::abi::sockets::*;
+}
+
+pub type wrlen_t = size_t;
+
+const READ_LIMIT: usize = libc::ssize_t::MAX as usize;
+
+const fn max_iov() -> usize {
+    // Judging by the source code, it's unlimited, but specify a lower
+    // value just in case.
+    1024
+}
+
+/// A file descriptor.
+#[rustc_layout_scalar_valid_range_start(0)]
+// libstd/os/raw/mod.rs assures me that every libstd-supported platform has a
+// 32-bit c_int. Below is -2, in two's complement, but that only works out
+// because c_int is 32 bits.
+#[rustc_layout_scalar_valid_range_end(0xFF_FF_FF_FE)]
+struct FileDesc {
+    fd: c_int,
+}
+
+impl FileDesc {
+    #[inline]
+    fn new(fd: c_int) -> FileDesc {
+        assert_ne!(fd, -1i32);
+        // Safety: we just asserted that the value is in the valid range and
+        // isn't `-1` (the only value bigger than `0xFF_FF_FF_FE` unsigned)
+        unsafe { FileDesc { fd } }
+    }
+
+    #[inline]
+    fn raw(&self) -> c_int {
+        self.fd
+    }
+
+    /// Extracts the actual file descriptor without closing it.
+    #[inline]
+    fn into_raw(self) -> c_int {
+        let fd = self.fd;
+        mem::forget(self);
+        fd
+    }
+
+    fn read(&self, buf: &mut [u8]) -> io::Result<usize> {
+        let ret = cvt(unsafe {
+            netc::read(self.fd, buf.as_mut_ptr() as *mut c_void, cmp::min(buf.len(), READ_LIMIT))
+        })?;
+        Ok(ret as usize)
+    }
+
+    fn read_vectored(&self, bufs: &mut [IoSliceMut<'_>]) -> io::Result<usize> {
+        let ret = cvt(unsafe {
+            netc::readv(
+                self.fd,
+                bufs.as_ptr() as *const netc::iovec,
+                cmp::min(bufs.len(), max_iov()) as c_int,
+            )
+        })?;
+        Ok(ret as usize)
+    }
+
+    #[inline]
+    fn is_read_vectored(&self) -> bool {
+        true
+    }
+
+    fn write(&self, buf: &[u8]) -> io::Result<usize> {
+        let ret = cvt(unsafe {
+            netc::write(self.fd, buf.as_ptr() as *const c_void, cmp::min(buf.len(), READ_LIMIT))
+        })?;
+        Ok(ret as usize)
+    }
+
+    fn write_vectored(&self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
+        let ret = cvt(unsafe {
+            netc::writev(
+                self.fd,
+                bufs.as_ptr() as *const netc::iovec,
+                cmp::min(bufs.len(), max_iov()) as c_int,
+            )
+        })?;
+        Ok(ret as usize)
+    }
+
+    #[inline]
+    fn is_write_vectored(&self) -> bool {
+        true
+    }
+
+    fn duplicate(&self) -> io::Result<FileDesc> {
+        super::unsupported()
+    }
+}
+
+impl AsInner<c_int> for FileDesc {
+    fn as_inner(&self) -> &c_int {
+        &self.fd
+    }
+}
+
+impl Drop for FileDesc {
+    fn drop(&mut self) {
+        unsafe { netc::close(self.fd) };
+    }
+}
+
+#[doc(hidden)]
+pub trait IsMinusOne {
+    fn is_minus_one(&self) -> bool;
+}
+
+macro_rules! impl_is_minus_one {
+    ($($t:ident)*) => ($(impl IsMinusOne for $t {
+        fn is_minus_one(&self) -> bool {
+            *self == -1
+        }
+    })*)
+}
+
+impl_is_minus_one! { i8 i16 i32 i64 isize }
+
+pub fn cvt<T: IsMinusOne>(t: T) -> io::Result<T> {
+    if t.is_minus_one() { Err(last_error()) } else { Ok(t) }
+}
+
+/// A variant of `cvt` for `getaddrinfo` which return 0 for a success.
+pub fn cvt_gai(err: c_int) -> io::Result<()> {
+    if err == 0 {
+        Ok(())
+    } else {
+        let msg: &dyn crate::fmt::Display = match err {
+            netc::EAI_NONAME => &"name or service not known",
+            netc::EAI_SERVICE => &"service not supported",
+            netc::EAI_FAIL => &"non-recoverable failure in name resolution",
+            netc::EAI_MEMORY => &"memory allocation failure",
+            netc::EAI_FAMILY => &"family not supported",
+            _ => &err,
+        };
+        Err(io::Error::new(
+            io::ErrorKind::Uncategorized,
+            &format!("failed to lookup address information: {}", msg)[..],
+        ))
+    }
+}
+
+/// Just to provide the same interface as sys/unix/net.rs
+pub fn cvt_r<T, F>(mut f: F) -> io::Result<T>
+where
+    T: IsMinusOne,
+    F: FnMut() -> T,
+{
+    cvt(f())
+}
+
+/// Returns the last error from the network subsystem.
+fn last_error() -> io::Error {
+    io::Error::from_raw_os_error(unsafe { netc::SOLID_NET_GetLastError() })
+}
+
+pub(super) fn error_name(er: abi::ER) -> Option<&'static str> {
+    unsafe { CStr::from_ptr(netc::strerror(er)) }.to_str().ok()
+}
+
+pub(super) fn decode_error_kind(er: abi::ER) -> ErrorKind {
+    let errno = netc::SOLID_NET_ERR_BASE - er;
+    match errno as libc::c_int {
+        libc::ECONNREFUSED => ErrorKind::ConnectionRefused,
+        libc::ECONNRESET => ErrorKind::ConnectionReset,
+        libc::EPERM | libc::EACCES => ErrorKind::PermissionDenied,
+        libc::EPIPE => ErrorKind::BrokenPipe,
+        libc::ENOTCONN => ErrorKind::NotConnected,
+        libc::ECONNABORTED => ErrorKind::ConnectionAborted,
+        libc::EADDRNOTAVAIL => ErrorKind::AddrNotAvailable,
+        libc::EADDRINUSE => ErrorKind::AddrInUse,
+        libc::ENOENT => ErrorKind::NotFound,
+        libc::EINTR => ErrorKind::Interrupted,
+        libc::EINVAL => ErrorKind::InvalidInput,
+        libc::ETIMEDOUT => ErrorKind::TimedOut,
+        libc::EEXIST => ErrorKind::AlreadyExists,
+        libc::ENOSYS => ErrorKind::Unsupported,
+        libc::ENOMEM => ErrorKind::OutOfMemory,
+        libc::EAGAIN => ErrorKind::WouldBlock,
+
+        _ => ErrorKind::Uncategorized,
+    }
+}
+
+pub fn init() {}
+
+pub struct Socket(FileDesc);
+
+impl Socket {
+    pub fn new(addr: &SocketAddr, ty: c_int) -> io::Result<Socket> {
+        let fam = match *addr {
+            SocketAddr::V4(..) => netc::AF_INET,
+            SocketAddr::V6(..) => netc::AF_INET6,
+        };
+        Socket::new_raw(fam, ty)
+    }
+
+    pub fn new_raw(fam: c_int, ty: c_int) -> io::Result<Socket> {
+        unsafe {
+            let fd = cvt(netc::socket(fam, ty, 0))?;
+            let fd = FileDesc::new(fd);
+            let socket = Socket(fd);
+
+            Ok(socket)
+        }
+    }
+
+    pub fn connect_timeout(&self, addr: &SocketAddr, timeout: Duration) -> io::Result<()> {
+        self.set_nonblocking(true)?;
+        let r = unsafe {
+            let (addrp, len) = addr.into_inner();
+            cvt(netc::connect(self.0.raw(), addrp, len))
+        };
+        self.set_nonblocking(false)?;
+
+        match r {
+            Ok(_) => return Ok(()),
+            // there's no ErrorKind for EINPROGRESS
+            Err(ref e) if e.raw_os_error() == Some(netc::EINPROGRESS) => {}
+            Err(e) => return Err(e),
+        }
+
+        if timeout.as_secs() == 0 && timeout.subsec_nanos() == 0 {
+            return Err(io::Error::new_const(
+                io::ErrorKind::InvalidInput,
+                &"cannot set a 0 duration timeout",
+            ));
+        }
+
+        let mut timeout =
+            netc::timeval { tv_sec: timeout.as_secs() as _, tv_usec: timeout.subsec_micros() as _ };
+        if timeout.tv_sec == 0 && timeout.tv_usec == 0 {
+            timeout.tv_usec = 1;
+        }
+
+        let fds = netc::fd_set { num_fds: 1, fds: [self.0.raw()] };
+
+        let mut writefds = fds;
+        let mut errorfds = fds;
+
+        let n = unsafe {
+            cvt(netc::select(
+                self.0.raw() + 1,
+                ptr::null_mut(),
+                &mut writefds,
+                &mut errorfds,
+                &mut timeout,
+            ))?
+        };
+
+        match n {
+            0 => Err(io::Error::new_const(io::ErrorKind::TimedOut, &"connection timed out")),
+            _ => {
+                let can_write = writefds.num_fds != 0;
+                if !can_write {
+                    if let Some(e) = self.take_error()? {
+                        return Err(e);
+                    }
+                }
+                Ok(())
+            }
+        }
+    }
+
+    pub fn accept(&self, storage: *mut sockaddr, len: *mut socklen_t) -> io::Result<Socket> {
+        let fd = cvt_r(|| unsafe { netc::accept(self.0.raw(), storage, len) })?;
+        let fd = FileDesc::new(fd);
+        Ok(Socket(fd))
+    }
+
+    pub fn duplicate(&self) -> io::Result<Socket> {
+        self.0.duplicate().map(Socket)
+    }
+
+    fn recv_with_flags(&self, buf: &mut [u8], flags: c_int) -> io::Result<usize> {
+        let ret = cvt(unsafe {
+            netc::recv(self.0.raw(), buf.as_mut_ptr() as *mut c_void, buf.len(), flags)
+        })?;
+        Ok(ret as usize)
+    }
+
+    pub fn read(&self, buf: &mut [u8]) -> io::Result<usize> {
+        self.recv_with_flags(buf, 0)
+    }
+
+    pub fn peek(&self, buf: &mut [u8]) -> io::Result<usize> {
+        self.recv_with_flags(buf, MSG_PEEK)
+    }
+
+    pub fn read_vectored(&self, bufs: &mut [IoSliceMut<'_>]) -> io::Result<usize> {
+        self.0.read_vectored(bufs)
+    }
+
+    #[inline]
+    pub fn is_read_vectored(&self) -> bool {
+        self.0.is_read_vectored()
+    }
+
+    fn recv_from_with_flags(
+        &self,
+        buf: &mut [u8],
+        flags: c_int,
+    ) -> io::Result<(usize, SocketAddr)> {
+        let mut storage: netc::sockaddr_storage = unsafe { mem::zeroed() };
+        let mut addrlen = mem::size_of_val(&storage) as netc::socklen_t;
+
+        let n = cvt(unsafe {
+            netc::recvfrom(
+                self.0.raw(),
+                buf.as_mut_ptr() as *mut c_void,
+                buf.len(),
+                flags,
+                &mut storage as *mut _ as *mut _,
+                &mut addrlen,
+            )
+        })?;
+        Ok((n as usize, sockaddr_to_addr(&storage, addrlen as usize)?))
+    }
+
+    pub fn recv_from(&self, buf: &mut [u8]) -> io::Result<(usize, SocketAddr)> {
+        self.recv_from_with_flags(buf, 0)
+    }
+
+    pub fn peek_from(&self, buf: &mut [u8]) -> io::Result<(usize, SocketAddr)> {
+        self.recv_from_with_flags(buf, MSG_PEEK)
+    }
+
+    pub fn write(&self, buf: &[u8]) -> io::Result<usize> {
+        self.0.write(buf)
+    }
+
+    pub fn write_vectored(&self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
+        self.0.write_vectored(bufs)
+    }
+
+    #[inline]
+    pub fn is_write_vectored(&self) -> bool {
+        self.0.is_write_vectored()
+    }
+
+    pub fn set_timeout(&self, dur: Option<Duration>, kind: c_int) -> io::Result<()> {
+        let timeout = match dur {
+            Some(dur) => {
+                if dur.as_secs() == 0 && dur.subsec_nanos() == 0 {
+                    return Err(io::Error::new_const(
+                        io::ErrorKind::InvalidInput,
+                        &"cannot set a 0 duration timeout",
+                    ));
+                }
+
+                let secs = if dur.as_secs() > netc::c_long::MAX as u64 {
+                    netc::c_long::MAX
+                } else {
+                    dur.as_secs() as netc::c_long
+                };
+                let mut timeout = netc::timeval { tv_sec: secs, tv_usec: dur.subsec_micros() as _ };
+                if timeout.tv_sec == 0 && timeout.tv_usec == 0 {
+                    timeout.tv_usec = 1;
+                }
+                timeout
+            }
+            None => netc::timeval { tv_sec: 0, tv_usec: 0 },
+        };
+        setsockopt(self, netc::SOL_SOCKET, kind, timeout)
+    }
+
+    pub fn timeout(&self, kind: c_int) -> io::Result<Option<Duration>> {
+        let raw: netc::timeval = getsockopt(self, netc::SOL_SOCKET, kind)?;
+        if raw.tv_sec == 0 && raw.tv_usec == 0 {
+            Ok(None)
+        } else {
+            let sec = raw.tv_sec as u64;
+            let nsec = (raw.tv_usec as u32) * 1000;
+            Ok(Some(Duration::new(sec, nsec)))
+        }
+    }
+
+    pub fn shutdown(&self, how: Shutdown) -> io::Result<()> {
+        let how = match how {
+            Shutdown::Write => netc::SHUT_WR,
+            Shutdown::Read => netc::SHUT_RD,
+            Shutdown::Both => netc::SHUT_RDWR,
+        };
+        cvt(unsafe { netc::shutdown(self.0.raw(), how) })?;
+        Ok(())
+    }
+
+    pub fn set_linger(&self, linger: Option<Duration>) -> io::Result<()> {
+        let linger = netc::linger {
+            l_onoff: linger.is_some() as netc::c_int,
+            l_linger: linger.unwrap_or_default().as_secs() as netc::c_int,
+        };
+
+        setsockopt(self, netc::SOL_SOCKET, netc::SO_LINGER, linger)
+    }
+
+    pub fn linger(&self) -> io::Result<Option<Duration>> {
+        let val: netc::linger = getsockopt(self, netc::SOL_SOCKET, netc::SO_LINGER)?;
+
+        Ok((val.l_onoff != 0).then(|| Duration::from_secs(val.l_linger as u64)))
+    }
+
+    pub fn set_nodelay(&self, nodelay: bool) -> io::Result<()> {
+        setsockopt(self, netc::IPPROTO_TCP, netc::TCP_NODELAY, nodelay as c_int)
+    }
+
+    pub fn nodelay(&self) -> io::Result<bool> {
+        let raw: c_int = getsockopt(self, netc::IPPROTO_TCP, netc::TCP_NODELAY)?;
+        Ok(raw != 0)
+    }
+
+    pub fn set_nonblocking(&self, nonblocking: bool) -> io::Result<()> {
+        let mut nonblocking = nonblocking as c_int;
+        cvt(unsafe {
+            netc::ioctl(*self.as_inner(), netc::FIONBIO, (&mut nonblocking) as *mut c_int as _)
+        })
+        .map(drop)
+    }
+
+    pub fn take_error(&self) -> io::Result<Option<io::Error>> {
+        let raw: c_int = getsockopt(self, netc::SOL_SOCKET, netc::SO_ERROR)?;
+        if raw == 0 { Ok(None) } else { Ok(Some(io::Error::from_raw_os_error(raw as i32))) }
+    }
+
+    // This method is used by sys_common code to abstract over targets.
+    pub fn as_raw(&self) -> c_int {
+        *self.as_inner()
+    }
+}
+
+impl AsInner<c_int> for Socket {
+    fn as_inner(&self) -> &c_int {
+        self.0.as_inner()
+    }
+}
+
+impl FromInner<c_int> for Socket {
+    fn from_inner(fd: c_int) -> Socket {
+        Socket(FileDesc::new(fd))
+    }
+}
+
+impl IntoInner<c_int> for Socket {
+    fn into_inner(self) -> c_int {
+        self.0.into_raw()
+    }
+}
diff --git a/library/std/src/sys/solid/os.rs b/library/std/src/sys/solid/os.rs
new file mode 100644
index 00000000000..82542d81e67
--- /dev/null
+++ b/library/std/src/sys/solid/os.rs
@@ -0,0 +1,200 @@
+use super::unsupported;
+use crate::error::Error as StdError;
+use crate::ffi::{CStr, CString, OsStr, OsString};
+use crate::fmt;
+use crate::io;
+use crate::os::{
+    raw::{c_char, c_int},
+    solid::ffi::{OsStrExt, OsStringExt},
+};
+use crate::path::{self, PathBuf};
+use crate::sys_common::rwlock::StaticRWLock;
+use crate::vec;
+
+use super::{abi, error, itron, memchr};
+
+// `solid` directly maps `errno`s to μITRON error codes.
+impl itron::error::ItronError {
+    #[inline]
+    pub(crate) fn as_io_error(self) -> crate::io::Error {
+        crate::io::Error::from_raw_os_error(self.as_raw())
+    }
+}
+
+pub fn errno() -> i32 {
+    0
+}
+
+pub fn error_string(errno: i32) -> String {
+    if let Some(name) = error::error_name(errno) { name.to_owned() } else { format!("{}", errno) }
+}
+
+pub fn getcwd() -> io::Result<PathBuf> {
+    unsupported()
+}
+
+pub fn chdir(_: &path::Path) -> io::Result<()> {
+    unsupported()
+}
+
+pub struct SplitPaths<'a>(&'a !);
+
+pub fn split_paths(_unparsed: &OsStr) -> SplitPaths<'_> {
+    panic!("unsupported")
+}
+
+impl<'a> Iterator for SplitPaths<'a> {
+    type Item = PathBuf;
+    fn next(&mut self) -> Option<PathBuf> {
+        *self.0
+    }
+}
+
+#[derive(Debug)]
+pub struct JoinPathsError;
+
+pub fn join_paths<I, T>(_paths: I) -> Result<OsString, JoinPathsError>
+where
+    I: Iterator<Item = T>,
+    T: AsRef<OsStr>,
+{
+    Err(JoinPathsError)
+}
+
+impl fmt::Display for JoinPathsError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        "not supported on this platform yet".fmt(f)
+    }
+}
+
+impl StdError for JoinPathsError {
+    #[allow(deprecated)]
+    fn description(&self) -> &str {
+        "not supported on this platform yet"
+    }
+}
+
+pub fn current_exe() -> io::Result<PathBuf> {
+    unsupported()
+}
+
+static ENV_LOCK: StaticRWLock = StaticRWLock::new();
+
+pub struct Env {
+    iter: vec::IntoIter<(OsString, OsString)>,
+}
+
+impl !Send for Env {}
+impl !Sync for Env {}
+
+impl Iterator for Env {
+    type Item = (OsString, OsString);
+    fn next(&mut self) -> Option<(OsString, OsString)> {
+        self.iter.next()
+    }
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.iter.size_hint()
+    }
+}
+
+/// Returns a vector of (variable, value) byte-vector pairs for all the
+/// environment variables of the current process.
+pub fn env() -> Env {
+    extern "C" {
+        static mut environ: *const *const c_char;
+    }
+
+    unsafe {
+        let _guard = ENV_LOCK.read();
+        let mut result = Vec::new();
+        if !environ.is_null() {
+            while !(*environ).is_null() {
+                if let Some(key_value) = parse(CStr::from_ptr(*environ).to_bytes()) {
+                    result.push(key_value);
+                }
+                environ = environ.add(1);
+            }
+        }
+        return Env { iter: result.into_iter() };
+    }
+
+    fn parse(input: &[u8]) -> Option<(OsString, OsString)> {
+        // Strategy (copied from glibc): Variable name and value are separated
+        // by an ASCII equals sign '='. Since a variable name must not be
+        // empty, allow variable names starting with an equals sign. Skip all
+        // malformed lines.
+        if input.is_empty() {
+            return None;
+        }
+        let pos = memchr::memchr(b'=', &input[1..]).map(|p| p + 1);
+        pos.map(|p| {
+            (
+                OsStringExt::from_vec(input[..p].to_vec()),
+                OsStringExt::from_vec(input[p + 1..].to_vec()),
+            )
+        })
+    }
+}
+
+pub fn getenv(k: &OsStr) -> Option<OsString> {
+    // environment variables with a nul byte can't be set, so their value is
+    // always None as well
+    let k = CString::new(k.as_bytes()).ok()?;
+    unsafe {
+        let _guard = ENV_LOCK.read();
+        let s = libc::getenv(k.as_ptr()) as *const libc::c_char;
+        if s.is_null() {
+            None
+        } else {
+            Some(OsStringExt::from_vec(CStr::from_ptr(s).to_bytes().to_vec()))
+        }
+    }
+}
+
+pub fn setenv(k: &OsStr, v: &OsStr) -> io::Result<()> {
+    let k = CString::new(k.as_bytes())?;
+    let v = CString::new(v.as_bytes())?;
+
+    unsafe {
+        let _guard = ENV_LOCK.write();
+        cvt_env(libc::setenv(k.as_ptr(), v.as_ptr(), 1)).map(drop)
+    }
+}
+
+pub fn unsetenv(n: &OsStr) -> io::Result<()> {
+    let nbuf = CString::new(n.as_bytes())?;
+
+    unsafe {
+        let _guard = ENV_LOCK.write();
+        cvt_env(libc::unsetenv(nbuf.as_ptr())).map(drop)
+    }
+}
+
+/// In kmclib, `setenv` and `unsetenv` don't always set `errno`, so this
+/// function just returns a generic error.
+fn cvt_env(t: c_int) -> io::Result<c_int> {
+    if t == -1 {
+        Err(io::Error::new_const(io::ErrorKind::Uncategorized, &"failure"))
+    } else {
+        Ok(t)
+    }
+}
+
+pub fn temp_dir() -> PathBuf {
+    panic!("no standard temporary directory on this platform")
+}
+
+pub fn home_dir() -> Option<PathBuf> {
+    None
+}
+
+pub fn exit(_code: i32) -> ! {
+    let tid = itron::task::try_current_task_id().unwrap_or(0);
+    loop {
+        abi::breakpoint_program_exited(tid as usize);
+    }
+}
+
+pub fn getpid() -> u32 {
+    panic!("no pids on this platform")
+}
diff --git a/library/std/src/sys/solid/path.rs b/library/std/src/sys/solid/path.rs
new file mode 100644
index 00000000000..4a14332d499
--- /dev/null
+++ b/library/std/src/sys/solid/path.rs
@@ -0,0 +1,19 @@
+use crate::ffi::OsStr;
+use crate::path::Prefix;
+
+#[inline]
+pub fn is_sep_byte(b: u8) -> bool {
+    b == b'\\'
+}
+
+#[inline]
+pub fn is_verbatim_sep(b: u8) -> bool {
+    b == b'\\'
+}
+
+pub fn parse_prefix(_: &OsStr) -> Option<Prefix<'_>> {
+    None
+}
+
+pub const MAIN_SEP_STR: &str = "\\";
+pub const MAIN_SEP: char = '\\';
diff --git a/library/std/src/sys/solid/rwlock.rs b/library/std/src/sys/solid/rwlock.rs
new file mode 100644
index 00000000000..4e39ac2a930
--- /dev/null
+++ b/library/std/src/sys/solid/rwlock.rs
@@ -0,0 +1,92 @@
+//! A readers-writer lock implementation backed by the SOLID kernel extension.
+use super::{
+    abi,
+    itron::{
+        error::{expect_success, expect_success_aborting, fail, ItronError},
+        spin::SpinIdOnceCell,
+    },
+};
+
+pub struct RWLock {
+    /// The ID of the underlying mutex object
+    rwl: SpinIdOnceCell<()>,
+}
+
+pub type MovableRWLock = RWLock;
+
+// Safety: `num_readers` is protected by `mtx_num_readers`
+unsafe impl Send for RWLock {}
+unsafe impl Sync for RWLock {}
+
+fn new_rwl() -> Result<abi::ID, ItronError> {
+    ItronError::err_if_negative(unsafe { abi::rwl_acre_rwl() })
+}
+
+impl RWLock {
+    pub const fn new() -> RWLock {
+        RWLock { rwl: SpinIdOnceCell::new() }
+    }
+
+    /// Get the inner mutex's ID, which is lazily created.
+    fn raw(&self) -> abi::ID {
+        match self.rwl.get_or_try_init(|| new_rwl().map(|id| (id, ()))) {
+            Ok((id, ())) => id,
+            Err(e) => fail(e, &"rwl_acre_rwl"),
+        }
+    }
+
+    #[inline]
+    pub unsafe fn read(&self) {
+        let rwl = self.raw();
+        expect_success(unsafe { abi::rwl_loc_rdl(rwl) }, &"rwl_loc_rdl");
+    }
+
+    #[inline]
+    pub unsafe fn try_read(&self) -> bool {
+        let rwl = self.raw();
+        match unsafe { abi::rwl_ploc_rdl(rwl) } {
+            abi::E_TMOUT => false,
+            er => {
+                expect_success(er, &"rwl_ploc_rdl");
+                true
+            }
+        }
+    }
+
+    #[inline]
+    pub unsafe fn write(&self) {
+        let rwl = self.raw();
+        expect_success(unsafe { abi::rwl_loc_wrl(rwl) }, &"rwl_loc_wrl");
+    }
+
+    #[inline]
+    pub unsafe fn try_write(&self) -> bool {
+        let rwl = self.raw();
+        match unsafe { abi::rwl_ploc_wrl(rwl) } {
+            abi::E_TMOUT => false,
+            er => {
+                expect_success(er, &"rwl_ploc_wrl");
+                true
+            }
+        }
+    }
+
+    #[inline]
+    pub unsafe fn read_unlock(&self) {
+        let rwl = self.raw();
+        expect_success_aborting(unsafe { abi::rwl_unl_rwl(rwl) }, &"rwl_unl_rwl");
+    }
+
+    #[inline]
+    pub unsafe fn write_unlock(&self) {
+        let rwl = self.raw();
+        expect_success_aborting(unsafe { abi::rwl_unl_rwl(rwl) }, &"rwl_unl_rwl");
+    }
+
+    #[inline]
+    pub unsafe fn destroy(&self) {
+        if let Some(rwl) = self.rwl.get().map(|x| x.0) {
+            expect_success_aborting(unsafe { abi::rwl_del_rwl(rwl) }, &"rwl_del_rwl");
+        }
+    }
+}
diff --git a/library/std/src/sys/solid/stdio.rs b/library/std/src/sys/solid/stdio.rs
new file mode 100644
index 00000000000..50f0176967b
--- /dev/null
+++ b/library/std/src/sys/solid/stdio.rs
@@ -0,0 +1,80 @@
+use super::abi;
+use crate::io;
+
+pub struct Stdin;
+pub struct Stdout;
+pub struct Stderr;
+struct PanicOutput;
+
+impl Stdin {
+    pub const fn new() -> Stdin {
+        Stdin
+    }
+}
+
+impl io::Read for Stdin {
+    fn read(&mut self, _buf: &mut [u8]) -> io::Result<usize> {
+        Ok(0)
+    }
+}
+
+impl Stdout {
+    pub const fn new() -> Stdout {
+        Stdout
+    }
+}
+
+impl io::Write for Stdout {
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        unsafe { abi::SOLID_LOG_write(buf.as_ptr(), buf.len()) };
+        Ok(buf.len())
+    }
+
+    fn flush(&mut self) -> io::Result<()> {
+        Ok(())
+    }
+}
+
+impl Stderr {
+    pub const fn new() -> Stderr {
+        Stderr
+    }
+}
+
+impl io::Write for Stderr {
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        unsafe { abi::SOLID_LOG_write(buf.as_ptr(), buf.len()) };
+        Ok(buf.len())
+    }
+
+    fn flush(&mut self) -> io::Result<()> {
+        Ok(())
+    }
+}
+
+impl PanicOutput {
+    pub const fn new() -> PanicOutput {
+        PanicOutput
+    }
+}
+
+impl io::Write for PanicOutput {
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        unsafe { abi::SOLID_LOG_write(buf.as_ptr(), buf.len()) };
+        Ok(buf.len())
+    }
+
+    fn flush(&mut self) -> io::Result<()> {
+        Ok(())
+    }
+}
+
+pub const STDIN_BUF_SIZE: usize = 0;
+
+pub fn is_ebadf(_err: &io::Error) -> bool {
+    true
+}
+
+pub fn panic_output() -> Option<impl io::Write> {
+    Some(PanicOutput::new())
+}
diff --git a/library/std/src/sys/solid/thread_local_dtor.rs b/library/std/src/sys/solid/thread_local_dtor.rs
new file mode 100644
index 00000000000..97356457057
--- /dev/null
+++ b/library/std/src/sys/solid/thread_local_dtor.rs
@@ -0,0 +1,50 @@
+#![cfg(target_thread_local)]
+#![unstable(feature = "thread_local_internals", issue = "none")]
+
+// Simplify dtor registration by using a list of destructors.
+
+use super::{abi, itron::task};
+use crate::cell::Cell;
+use crate::ptr;
+
+#[thread_local]
+static DTORS: Cell<*mut List> = Cell::new(ptr::null_mut());
+
+type List = Vec<(*mut u8, unsafe extern "C" fn(*mut u8))>;
+
+pub unsafe fn register_dtor(t: *mut u8, dtor: unsafe extern "C" fn(*mut u8)) {
+    if DTORS.get().is_null() {
+        let tid = task::current_task_id_aborting();
+        let v: Box<List> = box Vec::new();
+        DTORS.set(Box::into_raw(v));
+
+        // Register `tls_dtor` to make sure the TLS destructors are called
+        // for tasks created by other means than `std::thread`
+        unsafe { abi::SOLID_TLS_AddDestructor(tid as i32, tls_dtor) };
+    }
+
+    let list: &mut List = unsafe { &mut *DTORS.get() };
+    list.push((t, dtor));
+}
+
+pub unsafe fn run_dtors() {
+    let ptr = DTORS.get();
+    if !ptr.is_null() {
+        // Swap the destructor list, call all registered destructors,
+        // and repeat this until the list becomes permanently empty.
+        while let Some(list) = Some(crate::mem::replace(unsafe { &mut *ptr }, Vec::new()))
+            .filter(|list| !list.is_empty())
+        {
+            for (ptr, dtor) in list.into_iter() {
+                unsafe { dtor(ptr) };
+            }
+        }
+
+        // Drop the destructor list
+        unsafe { Box::from_raw(DTORS.replace(ptr::null_mut())) };
+    }
+}
+
+unsafe extern "C" fn tls_dtor(_unused: *mut u8) {
+    unsafe { run_dtors() };
+}
diff --git a/library/std/src/sys/solid/thread_local_key.rs b/library/std/src/sys/solid/thread_local_key.rs
new file mode 100644
index 00000000000..b17521f701d
--- /dev/null
+++ b/library/std/src/sys/solid/thread_local_key.rs
@@ -0,0 +1,26 @@
+pub type Key = usize;
+
+#[inline]
+pub unsafe fn create(_dtor: Option<unsafe extern "C" fn(*mut u8)>) -> Key {
+    panic!("should not be used on the solid target");
+}
+
+#[inline]
+pub unsafe fn set(_key: Key, _value: *mut u8) {
+    panic!("should not be used on the solid target");
+}
+
+#[inline]
+pub unsafe fn get(_key: Key) -> *mut u8 {
+    panic!("should not be used on the solid target");
+}
+
+#[inline]
+pub unsafe fn destroy(_key: Key) {
+    panic!("should not be used on the solid target");
+}
+
+#[inline]
+pub fn requires_synchronized_create() -> bool {
+    panic!("should not be used on the solid target");
+}
diff --git a/library/std/src/sys/solid/time.rs b/library/std/src/sys/solid/time.rs
new file mode 100644
index 00000000000..c67a736a903
--- /dev/null
+++ b/library/std/src/sys/solid/time.rs
@@ -0,0 +1,56 @@
+use super::{abi, error::expect_success};
+use crate::{convert::TryInto, mem::MaybeUninit, time::Duration};
+
+pub use super::itron::time::Instant;
+
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug, Hash)]
+pub struct SystemTime(abi::time_t);
+
+pub const UNIX_EPOCH: SystemTime = SystemTime(0);
+
+impl SystemTime {
+    pub fn now() -> SystemTime {
+        let rtc = unsafe {
+            let mut out = MaybeUninit::zeroed();
+            expect_success(abi::SOLID_RTC_ReadTime(out.as_mut_ptr()), &"SOLID_RTC_ReadTime");
+            out.assume_init()
+        };
+        let t = unsafe {
+            libc::mktime(&mut libc::tm {
+                tm_sec: rtc.tm_sec,
+                tm_min: rtc.tm_min,
+                tm_hour: rtc.tm_hour,
+                tm_mday: rtc.tm_mday,
+                tm_mon: rtc.tm_mon,
+                tm_year: rtc.tm_year,
+                tm_wday: rtc.tm_wday,
+                tm_yday: 0,
+                tm_isdst: 0,
+                tm_gmtoff: 0,
+                tm_zone: crate::ptr::null_mut(),
+            })
+        };
+        assert_ne!(t, -1, "mktime failed");
+        SystemTime(t)
+    }
+
+    pub(super) fn from_time_t(t: abi::time_t) -> Self {
+        Self(t)
+    }
+
+    pub fn sub_time(&self, other: &SystemTime) -> Result<Duration, Duration> {
+        if self.0 >= other.0 {
+            Ok(Duration::from_secs((self.0 as u64).wrapping_sub(other.0 as u64)))
+        } else {
+            Err(Duration::from_secs((other.0 as u64).wrapping_sub(self.0 as u64)))
+        }
+    }
+
+    pub fn checked_add_duration(&self, other: &Duration) -> Option<SystemTime> {
+        Some(SystemTime(self.0.checked_add(other.as_secs().try_into().ok()?)?))
+    }
+
+    pub fn checked_sub_duration(&self, other: &Duration) -> Option<SystemTime> {
+        Some(SystemTime(self.0.checked_sub(other.as_secs().try_into().ok()?)?))
+    }
+}
diff --git a/library/std/src/time.rs b/library/std/src/time.rs
index bf3eb5b30c7..358efd662f5 100644
--- a/library/std/src/time.rs
+++ b/library/std/src/time.rs
@@ -108,6 +108,7 @@ pub use core::time::FromSecsError;
 /// | UNIX      | [clock_gettime (Monotonic Clock)]                                    |
 /// | Darwin    | [mach_absolute_time]                                                 |
 /// | VXWorks   | [clock_gettime (Monotonic Clock)]                                    |
+/// | SOLID     | `get_tim`                                                            |
 /// | WASI      | [__wasi_clock_time_get (Monotonic Clock)]                            |
 /// | Windows   | [QueryPerformanceCounter]                                            |
 ///
@@ -184,6 +185,7 @@ pub struct Instant(time::Instant);
 /// | UNIX      | [clock_gettime (Realtime Clock)]                                     |
 /// | Darwin    | [gettimeofday]                                                       |
 /// | VXWorks   | [clock_gettime (Realtime Clock)]                                     |
+/// | SOLID     | `SOLID_RTC_ReadTime`                                                 |
 /// | WASI      | [__wasi_clock_time_get (Realtime Clock)]                             |
 /// | Windows   | [GetSystemTimePreciseAsFileTime] / [GetSystemTimeAsFileTime]         |
 ///
diff --git a/library/unwind/src/lib.rs b/library/unwind/src/lib.rs
index 06384b15926..25be9e7cc6c 100644
--- a/library/unwind/src/lib.rs
+++ b/library/unwind/src/lib.rs
@@ -23,6 +23,7 @@ cfg_if::cfg_if! {
         unix,
         windows,
         target_os = "psp",
+        target_os = "solid_asp3",
         all(target_vendor = "fortanix", target_env = "sgx"),
     ))] {
         mod libunwind;
diff --git a/src/doc/rustc/src/SUMMARY.md b/src/doc/rustc/src/SUMMARY.md
index bc1873b6836..8c418351837 100644
--- a/src/doc/rustc/src/SUMMARY.md
+++ b/src/doc/rustc/src/SUMMARY.md
@@ -14,6 +14,7 @@
 - [Tests](tests/index.md)
 - [Platform Support](platform-support.md)
     - [aarch64-apple-ios-sim](platform-support/aarch64-apple-ios-sim.md)
+    - [\*-kmc-solid_\*](platform-support/kmc-solid.md)
 - [Target Tier Policy](target-tier-policy.md)
 - [Targets](targets/index.md)
     - [Built-in Targets](targets/built-in.md)
diff --git a/src/doc/rustc/src/platform-support.md b/src/doc/rustc/src/platform-support.md
index 0f106292e96..e871b08c5b1 100644
--- a/src/doc/rustc/src/platform-support.md
+++ b/src/doc/rustc/src/platform-support.md
@@ -202,6 +202,7 @@ target | std | host | notes
 -------|:---:|:----:|-------
 `aarch64-apple-ios-macabi` | ? |  | Apple Catalyst on ARM64
 `aarch64-apple-tvos` | * |  | ARM64 tvOS
+[`aarch64-kmc-solid_asp3`](platform-support/kmc-solid.md) | ✓ |  | ARM64 SOLID with TOPPERS/ASP3
 `aarch64-unknown-freebsd` | ✓ | ✓ | ARM64 FreeBSD
 `aarch64-unknown-hermit` | ? |  |
 `aarch64-unknown-uefi` | * |  | ARM64 UEFI
@@ -222,6 +223,8 @@ target | std | host | notes
 `armv7-unknown-freebsd` | ✓ | ✓ | ARMv7 FreeBSD
 `armv7-unknown-netbsd-eabihf` | ✓ | ✓ |
 `armv7-wrs-vxworks-eabihf` | ? |  |
+[`armv7a-kmc-solid_asp3-eabi`](platform-support/kmc-solid.md) | ✓ |  | ARM SOLID with TOPPERS/ASP3
+[`armv7a-kmc-solid_asp3-eabihf`](platform-support/kmc-solid.md) | ✓ |  | ARM SOLID with TOPPERS/ASP3, hardfloat
 `armv7a-none-eabihf` | * | | ARM Cortex-A, hardfloat
 `armv7s-apple-ios` | ✓ |  |
 `avr-unknown-gnu-atmega328` | * |  | AVR. Requires `-Z build-std=core`
diff --git a/src/doc/rustc/src/platform-support/kmc-solid.md b/src/doc/rustc/src/platform-support/kmc-solid.md
new file mode 100644
index 00000000000..bbcd0f711c6
--- /dev/null
+++ b/src/doc/rustc/src/platform-support/kmc-solid.md
@@ -0,0 +1,65 @@
+# \*-kmc-solid_\*
+
+**Tier: 3**
+
+[SOLID] embedded development platform by Kyoto Microcomputer Co., Ltd.
+
+[SOLID]: https://www.kmckk.co.jp/eng/SOLID/
+
+The target names follow this format: `$ARCH-kmc-solid_$KERNEL-$ABI`, where `$ARCH` specifies the target processor architecture, `$KERNEL` the base kernel, and `$ABI` the target ABI (optional). The following targets are currently defined:
+
+|          Target name           | `target_arch` | `target_vendor` | `target_os`  |
+|--------------------------------|---------------|-----------------|--------------|
+| `aarch64-kmc-solid_asp3`       | `aarch64`     | `kmc`           | `solid_asp3` |
+| `armv7a-kmc-solid_asp3-eabi`   | `arm`         | `kmc`           | `solid_asp3` |
+| `armv7a-kmc-solid_asp3-eabihf` | `arm`         | `kmc`           | `solid_asp3` |
+
+## Designated Developers
+
+- [@kawadakk](https://github.com/kawadakk)
+
+## Requirements
+
+This target is cross-compiled.
+A platform-provided C compiler toolchain is required, though it can be substituted by [GNU Arm Embedded Toolchain](https://developer.arm.com/tools-and-software/open-source-software/developer-tools/gnu-toolchain/gnu-rm) for the purpose of building Rust and functional binaries.
+
+## Building
+
+The target can be built by enabling it for a `rustc` build.
+
+```toml
+[build]
+target = ["aarch64-kmc-solid_asp3"]
+```
+
+Make sure `aarch64-kmc-elf-gcc` is included in `$PATH`. Alternatively, you can use GNU Arm Embedded Toolchain by adding the following to `config.toml`:
+
+```toml
+[target.aarch64-kmc-solid_asp3]
+cc = "arm-none-eabi-gcc"
+```
+
+## Cross-compilation
+
+This target can be cross-compiled from any hosts.
+
+## Testing
+
+Currently there is no support to run the rustc test suite for this target.
+
+## Building Rust programs
+
+Building executables is not supported yet.
+
+If `rustc` has support for that target and the library artifacts are available, then Rust static libraries can be built for that target:
+
+```shell
+$ rustc --target aarch64-kmc-solid_asp3 your-code.rs --crate-type staticlib
+$ ls libyour_code.a
+```
+
+On Rust Nightly it's possible to build without the target artifacts available:
+
+```text
+cargo build -Z build-std --target aarch64-kmc-solid_asp3
+```