Port std library to RTEMS

20 files changed, 485 insertions, 12 deletions

diff --git a/library/core/Cargo.toml b/library/core/Cargo.toml
index cace4582b48..94f343d0670 100644
--- a/library/core/Cargo.toml
+++ b/library/core/Cargo.toml
@@ -43,6 +43,8 @@ check-cfg = [
     'cfg(bootstrap)',
     'cfg(no_fp_fmt_parse)',
     'cfg(stdarch_intel_sde)',
+    # #[cfg(bootstrap)] rtems
+    'cfg(target_os, values("rtems"))',
     # core use #[path] imports to portable-simd `core_simd` crate
     # and to stdarch `core_arch` crate which messes-up with Cargo list
     # of declared features, we therefor expect any feature cfg
diff --git a/library/core/src/ffi/mod.rs b/library/core/src/ffi/mod.rs
index ec1f9052a15..dc107c5d22c 100644
--- a/library/core/src/ffi/mod.rs
+++ b/library/core/src/ffi/mod.rs
@@ -110,7 +110,7 @@ mod c_char_definition {
             all(target_os = "android", any(target_arch = "aarch64", target_arch = "arm")),
             all(target_os = "l4re", target_arch = "x86_64"),
             all(
-                any(target_os = "freebsd", target_os = "openbsd"),
+                any(target_os = "freebsd", target_os = "openbsd", target_os = "rtems"),
                 any(
                     target_arch = "aarch64",
                     target_arch = "arm",
diff --git a/library/panic_unwind/Cargo.toml b/library/panic_unwind/Cargo.toml
index f830808d196..6d1f9764efb 100644
--- a/library/panic_unwind/Cargo.toml
+++ b/library/panic_unwind/Cargo.toml
@@ -20,3 +20,10 @@ cfg-if = { version = "1.0", features = ['rustc-dep-of-std'] }
 
 [target.'cfg(not(all(windows, target_env = "msvc")))'.dependencies]
 libc = { version = "0.2", default-features = false }
+
+[lints.rust.unexpected_cfgs]
+level = "warn"
+check-cfg = [
+    # #[cfg(bootstrap)] rtems
+    'cfg(target_os, values("rtems"))',
+]
diff --git a/library/panic_unwind/src/lib.rs b/library/panic_unwind/src/lib.rs
index 2d174f4b1a4..4552fb68d26 100644
--- a/library/panic_unwind/src/lib.rs
+++ b/library/panic_unwind/src/lib.rs
@@ -48,7 +48,7 @@ cfg_if::cfg_if! {
         target_os = "psp",
         target_os = "xous",
         target_os = "solid_asp3",
-        all(target_family = "unix", not(target_os = "espidf")),
+        all(target_family = "unix", not(any(target_os = "espidf", target_os = "rtems"))),
         all(target_vendor = "fortanix", target_env = "sgx"),
         target_family = "wasm",
     ))] {
diff --git a/library/std/Cargo.toml b/library/std/Cargo.toml
index 82cfd603a21..e20fe9feff1 100644
--- a/library/std/Cargo.toml
+++ b/library/std/Cargo.toml
@@ -146,4 +146,6 @@ check-cfg = [
     # and to the `backtrace` crate which messes-up with Cargo list
     # of declared features, we therefor expect any feature cfg
     'cfg(feature, values(any()))',
+    # #[cfg(bootstrap)] rtems
+    'cfg(target_os, values("rtems"))',
 ]
diff --git a/library/std/build.rs b/library/std/build.rs
index 72254cafc85..ba1eece46f3 100644
--- a/library/std/build.rs
+++ b/library/std/build.rs
@@ -53,6 +53,7 @@ fn main() {
         || target_os == "uefi"
         || target_os == "teeos"
         || target_os == "zkvm"
+        || target_os == "rtems"
 
         // See src/bootstrap/src/core/build_steps/synthetic_targets.rs
         || env::var("RUSTC_BOOTSTRAP_SYNTHETIC_TARGET").is_ok()
diff --git a/library/std/src/os/mod.rs b/library/std/src/os/mod.rs
index 020a8b324f4..a2496baa63f 100644
--- a/library/std/src/os/mod.rs
+++ b/library/std/src/os/mod.rs
@@ -143,6 +143,8 @@ pub mod nto;
 pub mod openbsd;
 #[cfg(target_os = "redox")]
 pub mod redox;
+#[cfg(target_os = "rtems")]
+pub mod rtems;
 #[cfg(target_os = "solaris")]
 pub mod solaris;
 #[cfg(target_os = "solid_asp3")]
diff --git a/library/std/src/os/rtems/fs.rs b/library/std/src/os/rtems/fs.rs
new file mode 100644
index 00000000000..bec0d41e42d
--- /dev/null
+++ b/library/std/src/os/rtems/fs.rs
@@ -0,0 +1,374 @@
+#![stable(feature = "metadata_ext", since = "1.1.0")]
+
+use crate::fs::Metadata;
+use crate::sys_common::AsInner;
+
+/// OS-specific extensions to [`fs::Metadata`].
+///
+/// [`fs::Metadata`]: crate::fs::Metadata
+#[stable(feature = "metadata_ext", since = "1.1.0")]
+pub trait MetadataExt {
+    /// Returns the device ID on which this file resides.
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// use std::fs;
+    /// use std::io;
+    /// use std::os::rtems::fs::MetadataExt;
+    ///
+    /// fn main() -> io::Result<()> {
+    ///     let meta = fs::metadata("some_file")?;
+    ///     println!("{}", meta.st_dev());
+    ///     Ok(())
+    /// }
+    /// ```
+    #[stable(feature = "metadata_ext2", since = "1.8.0")]
+    fn st_dev(&self) -> u64;
+
+    /// Returns the inode number.
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// use std::fs;
+    /// use std::io;
+    /// use std::os::rtems::fs::MetadataExt;
+    ///
+    /// fn main() -> io::Result<()> {
+    ///     let meta = fs::metadata("some_file")?;
+    ///     println!("{}", meta.st_ino());
+    ///     Ok(())
+    /// }
+    /// ```
+    #[stable(feature = "metadata_ext2", since = "1.8.0")]
+    fn st_ino(&self) -> u64;
+
+    /// Returns the file type and mode.
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// use std::fs;
+    /// use std::io;
+    /// use std::os::rtems::fs::MetadataExt;
+    ///
+    /// fn main() -> io::Result<()> {
+    ///     let meta = fs::metadata("some_file")?;
+    ///     println!("{}", meta.st_mode());
+    ///     Ok(())
+    /// }
+    /// ```
+    #[stable(feature = "metadata_ext2", since = "1.8.0")]
+    fn st_mode(&self) -> u32;
+
+    /// Returns the number of hard links to file.
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// use std::fs;
+    /// use std::io;
+    /// use std::os::rtems::fs::MetadataExt;
+    ///
+    /// fn main() -> io::Result<()> {
+    ///     let meta = fs::metadata("some_file")?;
+    ///     println!("{}", meta.st_nlink());
+    ///     Ok(())
+    /// }
+    /// ```
+    #[stable(feature = "metadata_ext2", since = "1.8.0")]
+    fn st_nlink(&self) -> u64;
+
+    /// Returns the user ID of the file owner.
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// use std::fs;
+    /// use std::io;
+    /// use std::os::rtems::fs::MetadataExt;
+    ///
+    /// fn main() -> io::Result<()> {
+    ///     let meta = fs::metadata("some_file")?;
+    ///     println!("{}", meta.st_uid());
+    ///     Ok(())
+    /// }
+    /// ```
+    #[stable(feature = "metadata_ext2", since = "1.8.0")]
+    fn st_uid(&self) -> u32;
+
+    /// Returns the group ID of the file owner.
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// use std::fs;
+    /// use std::io;
+    /// use std::os::rtems::fs::MetadataExt;
+    ///
+    /// fn main() -> io::Result<()> {
+    ///     let meta = fs::metadata("some_file")?;
+    ///     println!("{}", meta.st_gid());
+    ///     Ok(())
+    /// }
+    /// ```
+    #[stable(feature = "metadata_ext2", since = "1.8.0")]
+    fn st_gid(&self) -> u32;
+
+    /// Returns the device ID that this file represents. Only relevant for special file.
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// use std::fs;
+    /// use std::io;
+    /// use std::os::rtems::fs::MetadataExt;
+    ///
+    /// fn main() -> io::Result<()> {
+    ///     let meta = fs::metadata("some_file")?;
+    ///     println!("{}", meta.st_rdev());
+    ///     Ok(())
+    /// }
+    /// ```
+    #[stable(feature = "metadata_ext2", since = "1.8.0")]
+    fn st_rdev(&self) -> u64;
+
+    /// Returns the size of the file (if it is a regular file or a symbolic link) in bytes.
+    ///
+    /// The size of a symbolic link is the length of the pathname it contains,
+    /// without a terminating null byte.
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// use std::fs;
+    /// use std::io;
+    /// use std::os::rtems::fs::MetadataExt;
+    ///
+    /// fn main() -> io::Result<()> {
+    ///     let meta = fs::metadata("some_file")?;
+    ///     println!("{}", meta.st_size());
+    ///     Ok(())
+    /// }
+    /// ```
+    #[stable(feature = "metadata_ext2", since = "1.8.0")]
+    fn st_size(&self) -> u64;
+
+    /// Returns the last access time of the file, in seconds since Unix Epoch.
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// use std::fs;
+    /// use std::io;
+    /// use std::os::rtems::fs::MetadataExt;
+    ///
+    /// fn main() -> io::Result<()> {
+    ///     let meta = fs::metadata("some_file")?;
+    ///     println!("{}", meta.st_atime());
+    ///     Ok(())
+    /// }
+    /// ```
+    #[stable(feature = "metadata_ext2", since = "1.8.0")]
+    fn st_atime(&self) -> i64;
+
+    /// Returns the last access time of the file, in nanoseconds since [`st_atime`].
+    ///
+    /// [`st_atime`]: Self::st_atime
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// use std::fs;
+    /// use std::io;
+    /// use std::os::rtems::fs::MetadataExt;
+    ///
+    /// fn main() -> io::Result<()> {
+    ///     let meta = fs::metadata("some_file")?;
+    ///     println!("{}", meta.st_atime_nsec());
+    ///     Ok(())
+    /// }
+    /// ```
+    #[stable(feature = "metadata_ext2", since = "1.8.0")]
+    fn st_atime_nsec(&self) -> i64;
+
+    /// Returns the last modification time of the file, in seconds since Unix Epoch.
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// use std::fs;
+    /// use std::io;
+    /// use std::os::rtems::fs::MetadataExt;
+    ///
+    /// fn main() -> io::Result<()> {
+    ///     let meta = fs::metadata("some_file")?;
+    ///     println!("{}", meta.st_mtime());
+    ///     Ok(())
+    /// }
+    /// ```
+    #[stable(feature = "metadata_ext2", since = "1.8.0")]
+    fn st_mtime(&self) -> i64;
+
+    /// Returns the last modification time of the file, in nanoseconds since [`st_mtime`].
+    ///
+    /// [`st_mtime`]: Self::st_mtime
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// use std::fs;
+    /// use std::io;
+    /// use std::os::rtems::fs::MetadataExt;
+    ///
+    /// fn main() -> io::Result<()> {
+    ///     let meta = fs::metadata("some_file")?;
+    ///     println!("{}", meta.st_mtime_nsec());
+    ///     Ok(())
+    /// }
+    /// ```
+    #[stable(feature = "metadata_ext2", since = "1.8.0")]
+    fn st_mtime_nsec(&self) -> i64;
+
+    /// Returns the last status change time of the file, in seconds since Unix Epoch.
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// use std::fs;
+    /// use std::io;
+    /// use std::os::rtems::fs::MetadataExt;
+    ///
+    /// fn main() -> io::Result<()> {
+    ///     let meta = fs::metadata("some_file")?;
+    ///     println!("{}", meta.st_ctime());
+    ///     Ok(())
+    /// }
+    /// ```
+    #[stable(feature = "metadata_ext2", since = "1.8.0")]
+    fn st_ctime(&self) -> i64;
+
+    /// Returns the last status change time of the file, in nanoseconds since [`st_ctime`].
+    ///
+    /// [`st_ctime`]: Self::st_ctime
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// use std::fs;
+    /// use std::io;
+    /// use std::os::rtems::fs::MetadataExt;
+    ///
+    /// fn main() -> io::Result<()> {
+    ///     let meta = fs::metadata("some_file")?;
+    ///     println!("{}", meta.st_ctime_nsec());
+    ///     Ok(())
+    /// }
+    /// ```
+    #[stable(feature = "metadata_ext2", since = "1.8.0")]
+    fn st_ctime_nsec(&self) -> i64;
+
+    /// Returns the "preferred" block size for efficient filesystem I/O.
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// use std::fs;
+    /// use std::io;
+    /// use std::os::rtems::fs::MetadataExt;
+    ///
+    /// fn main() -> io::Result<()> {
+    ///     let meta = fs::metadata("some_file")?;
+    ///     println!("{}", meta.st_blksize());
+    ///     Ok(())
+    /// }
+    /// ```
+    #[stable(feature = "metadata_ext2", since = "1.8.0")]
+    fn st_blksize(&self) -> u64;
+
+    /// Returns the number of blocks allocated to the file, 512-byte units.
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// use std::fs;
+    /// use std::io;
+    /// use std::os::rtems::fs::MetadataExt;
+    ///
+    /// fn main() -> io::Result<()> {
+    ///     let meta = fs::metadata("some_file")?;
+    ///     println!("{}", meta.st_blocks());
+    ///     Ok(())
+    /// }
+    /// ```
+    #[stable(feature = "metadata_ext2", since = "1.8.0")]
+    fn st_blocks(&self) -> u64;
+}
+
+#[stable(feature = "metadata_ext", since = "1.1.0")]
+impl MetadataExt for Metadata {
+    fn st_dev(&self) -> u64 {
+        self.as_inner().as_inner().st_dev as u64
+    }
+
+    fn st_ino(&self) -> u64 {
+        self.as_inner().as_inner().st_ino as u64
+    }
+
+    fn st_mode(&self) -> u32 {
+        self.as_inner().as_inner().st_mode as u32
+    }
+
+    fn st_nlink(&self) -> u64 {
+        self.as_inner().as_inner().st_nlink as u64
+    }
+
+    fn st_uid(&self) -> u32 {
+        self.as_inner().as_inner().st_uid as u32
+    }
+
+    fn st_gid(&self) -> u32 {
+        self.as_inner().as_inner().st_gid as u32
+    }
+
+    fn st_rdev(&self) -> u64 {
+        self.as_inner().as_inner().st_rdev as u64
+    }
+
+    fn st_size(&self) -> u64 {
+        self.as_inner().as_inner().st_size as u64
+    }
+
+    fn st_atime(&self) -> i64 {
+        self.as_inner().as_inner().st_atime as i64
+    }
+
+    fn st_atime_nsec(&self) -> i64 {
+        0
+    }
+
+    fn st_mtime(&self) -> i64 {
+        self.as_inner().as_inner().st_mtime as i64
+    }
+
+    fn st_mtime_nsec(&self) -> i64 {
+        0
+    }
+
+    fn st_ctime(&self) -> i64 {
+        self.as_inner().as_inner().st_ctime as i64
+    }
+
+    fn st_ctime_nsec(&self) -> i64 {
+        0
+    }
+
+    fn st_blksize(&self) -> u64 {
+        self.as_inner().as_inner().st_blksize as u64
+    }
+
+    fn st_blocks(&self) -> u64 {
+        self.as_inner().as_inner().st_blocks as u64
+    }
+}
diff --git a/library/std/src/os/rtems/mod.rs b/library/std/src/os/rtems/mod.rs
new file mode 100644
index 00000000000..7275bfd1765
--- /dev/null
+++ b/library/std/src/os/rtems/mod.rs
@@ -0,0 +1,4 @@
+#![stable(feature = "raw_ext", since = "1.1.0")]
+#![forbid(unsafe_op_in_unsafe_fn)]
+pub mod fs;
+pub(crate) mod raw;
diff --git a/library/std/src/os/rtems/raw.rs b/library/std/src/os/rtems/raw.rs
new file mode 100644
index 00000000000..113079cf4ab
--- /dev/null
+++ b/library/std/src/os/rtems/raw.rs
@@ -0,0 +1,33 @@
+//! rtems raw type definitions
+
+#![stable(feature = "raw_ext", since = "1.1.0")]
+#![deprecated(
+    since = "1.8.0",
+    note = "these type aliases are no longer supported by \
+            the standard library, the `libc` crate on \
+            crates.io should be used instead for the correct \
+            definitions"
+)]
+#![allow(deprecated)]
+
+#[stable(feature = "pthread_t", since = "1.8.0")]
+pub type pthread_t = libc::pthread_t;
+
+#[stable(feature = "raw_ext", since = "1.1.0")]
+pub type blkcnt_t = libc::blkcnt_t;
+
+#[stable(feature = "raw_ext", since = "1.1.0")]
+pub type blksize_t = libc::blksize_t;
+#[stable(feature = "raw_ext", since = "1.1.0")]
+pub type dev_t = libc::dev_t;
+#[stable(feature = "raw_ext", since = "1.1.0")]
+pub type ino_t = libc::ino_t;
+#[stable(feature = "raw_ext", since = "1.1.0")]
+pub type mode_t = libc::mode_t;
+#[stable(feature = "raw_ext", since = "1.1.0")]
+pub type nlink_t = libc::nlink_t;
+#[stable(feature = "raw_ext", since = "1.1.0")]
+pub type off_t = libc::off_t;
+
+#[stable(feature = "raw_ext", since = "1.1.0")]
+pub type time_t = libc::time_t;
diff --git a/library/std/src/os/unix/mod.rs b/library/std/src/os/unix/mod.rs
index c6581b9c4c8..7d2f0bd4efe 100644
--- a/library/std/src/os/unix/mod.rs
+++ b/library/std/src/os/unix/mod.rs
@@ -73,6 +73,8 @@ mod platform {
     pub use crate::os::openbsd::*;
     #[cfg(target_os = "redox")]
     pub use crate::os::redox::*;
+    #[cfg(target_os = "rtems")]
+    pub use crate::os::rtems::*;
     #[cfg(target_os = "solaris")]
     pub use crate::os::solaris::*;
     #[cfg(target_os = "vita")]
diff --git a/library/std/src/sys/pal/unix/args.rs b/library/std/src/sys/pal/unix/args.rs
index 9a37e1a0346..a943e3a581a 100644
--- a/library/std/src/sys/pal/unix/args.rs
+++ b/library/std/src/sys/pal/unix/args.rs
@@ -112,6 +112,7 @@ impl DoubleEndedIterator for Args {
     target_os = "aix",
     target_os = "nto",
     target_os = "hurd",
+    target_os = "rtems",
 ))]
 mod imp {
     use crate::ffi::c_char;
diff --git a/library/std/src/sys/pal/unix/env.rs b/library/std/src/sys/pal/unix/env.rs
index fb1f868644d..b2d399b8791 100644
--- a/library/std/src/sys/pal/unix/env.rs
+++ b/library/std/src/sys/pal/unix/env.rs
@@ -240,6 +240,17 @@ pub mod os {
     pub const EXE_EXTENSION: &str = "";
 }
 
+#[cfg(target_os = "rtems")]
+pub mod os {
+    pub const FAMILY: &str = "unix";
+    pub const OS: &str = "rtems";
+    pub const DLL_PREFIX: &str = "lib";
+    pub const DLL_SUFFIX: &str = ".so";
+    pub const DLL_EXTENSION: &str = "so";
+    pub const EXE_SUFFIX: &str = "";
+    pub const EXE_EXTENSION: &str = "";
+}
+
 #[cfg(target_os = "vxworks")]
 pub mod os {
     pub const FAMILY: &str = "unix";
diff --git a/library/std/src/sys/pal/unix/fs.rs b/library/std/src/sys/pal/unix/fs.rs
index 7fa147c9754..4ec577a0a01 100644
--- a/library/std/src/sys/pal/unix/fs.rs
+++ b/library/std/src/sys/pal/unix/fs.rs
@@ -478,6 +478,7 @@ impl FileAttr {
         target_os = "horizon",
         target_os = "vita",
         target_os = "hurd",
+        target_os = "rtems",
     )))]
     pub fn modified(&self) -> io::Result<SystemTime> {
         #[cfg(target_pointer_width = "32")]
@@ -490,7 +491,12 @@ impl FileAttr {
         SystemTime::new(self.stat.st_mtime as i64, self.stat.st_mtime_nsec as i64)
     }
 
-    #[cfg(any(target_os = "vxworks", target_os = "espidf", target_os = "vita"))]
+    #[cfg(any(
+        target_os = "vxworks",
+        target_os = "espidf",
+        target_os = "vita",
+        target_os = "rtems",
+    ))]
     pub fn modified(&self) -> io::Result<SystemTime> {
         SystemTime::new(self.stat.st_mtime as i64, 0)
     }
@@ -506,6 +512,7 @@ impl FileAttr {
         target_os = "horizon",
         target_os = "vita",
         target_os = "hurd",
+        target_os = "rtems",
     )))]
     pub fn accessed(&self) -> io::Result<SystemTime> {
         #[cfg(target_pointer_width = "32")]
@@ -518,7 +525,12 @@ impl FileAttr {
         SystemTime::new(self.stat.st_atime as i64, self.stat.st_atime_nsec as i64)
     }
 
-    #[cfg(any(target_os = "vxworks", target_os = "espidf", target_os = "vita"))]
+    #[cfg(any(
+        target_os = "vxworks",
+        target_os = "espidf",
+        target_os = "vita",
+        target_os = "rtems"
+    ))]
     pub fn accessed(&self) -> io::Result<SystemTime> {
         SystemTime::new(self.stat.st_atime as i64, 0)
     }
@@ -853,6 +865,7 @@ impl Drop for Dir {
             target_os = "fuchsia",
             target_os = "horizon",
             target_os = "vxworks",
+            target_os = "rtems",
         )))]
         {
             let fd = unsafe { libc::dirfd(self.0) };
@@ -970,6 +983,7 @@ impl DirEntry {
         target_os = "aix",
         target_os = "nto",
         target_os = "hurd",
+        target_os = "rtems",
         target_vendor = "apple",
     ))]
     pub fn ino(&self) -> u64 {
diff --git a/library/std/src/sys/pal/unix/mod.rs b/library/std/src/sys/pal/unix/mod.rs
index ba2f58f9c10..e8428eccb16 100644
--- a/library/std/src/sys/pal/unix/mod.rs
+++ b/library/std/src/sys/pal/unix/mod.rs
@@ -79,6 +79,7 @@ pub unsafe fn init(argc: isize, argv: *const *const u8, sigpipe: u8) {
             target_os = "l4re",
             target_os = "horizon",
             target_os = "vita",
+            target_os = "rtems",
             // The poll on Darwin doesn't set POLLNVAL for closed fds.
             target_vendor = "apple",
         )))]
diff --git a/library/std/src/sys/pal/unix/os.rs b/library/std/src/sys/pal/unix/os.rs
index a785b97ac8d..503f8915256 100644
--- a/library/std/src/sys/pal/unix/os.rs
+++ b/library/std/src/sys/pal/unix/os.rs
@@ -31,7 +31,7 @@ cfg_if::cfg_if! {
 }
 
 extern "C" {
-    #[cfg(not(any(target_os = "dragonfly", target_os = "vxworks")))]
+    #[cfg(not(any(target_os = "dragonfly", target_os = "vxworks", target_os = "rtems")))]
     #[cfg_attr(
         any(
             target_os = "linux",
@@ -61,13 +61,14 @@ extern "C" {
 }
 
 /// Returns the platform-specific value of errno
-#[cfg(not(any(target_os = "dragonfly", target_os = "vxworks")))]
+#[cfg(not(any(target_os = "dragonfly", target_os = "vxworks", target_os = "rtems")))]
 pub fn errno() -> i32 {
     unsafe { (*errno_location()) as i32 }
 }
 
 /// Sets the platform-specific value of errno
-#[cfg(all(not(target_os = "dragonfly"), not(target_os = "vxworks")))] // needed for readdir and syscall!
+// needed for readdir and syscall!
+#[cfg(all(not(target_os = "dragonfly"), not(target_os = "vxworks"), not(target_os = "rtems")))]
 #[allow(dead_code)] // but not all target cfgs actually end up using it
 pub fn set_errno(e: i32) {
     unsafe { *errno_location() = e as c_int }
@@ -78,6 +79,16 @@ pub fn errno() -> i32 {
     unsafe { libc::errnoGet() }
 }
 
+#[cfg(target_os = "rtems")]
+pub fn errno() -> i32 {
+    extern "C" {
+        #[thread_local]
+        static _tls_errno: c_int;
+    }
+
+    unsafe { _tls_errno as i32 }
+}
+
 #[cfg(target_os = "dragonfly")]
 pub fn errno() -> i32 {
     extern "C" {
@@ -472,7 +483,7 @@ pub fn current_exe() -> io::Result<PathBuf> {
     }
 }
 
-#[cfg(target_os = "redox")]
+#[cfg(any(target_os = "redox", target_os = "rtems"))]
 pub fn current_exe() -> io::Result<PathBuf> {
     crate::fs::read_to_string("sys:exe").map(PathBuf::from)
 }
diff --git a/library/std/src/sys/pal/unix/process/process_unix.rs b/library/std/src/sys/pal/unix/process/process_unix.rs
index 9d091f033e0..4bb22f36709 100644
--- a/library/std/src/sys/pal/unix/process/process_unix.rs
+++ b/library/std/src/sys/pal/unix/process/process_unix.rs
@@ -1089,13 +1089,13 @@ fn signal_string(signal: i32) -> &'static str {
         libc::SIGURG => " (SIGURG)",
         #[cfg(not(target_os = "l4re"))]
         libc::SIGXCPU => " (SIGXCPU)",
-        #[cfg(not(target_os = "l4re"))]
+        #[cfg(not(any(target_os = "l4re", target_os = "rtems")))]
         libc::SIGXFSZ => " (SIGXFSZ)",
-        #[cfg(not(target_os = "l4re"))]
+        #[cfg(not(any(target_os = "l4re", target_os = "rtems")))]
         libc::SIGVTALRM => " (SIGVTALRM)",
         #[cfg(not(target_os = "l4re"))]
         libc::SIGPROF => " (SIGPROF)",
-        #[cfg(not(target_os = "l4re"))]
+        #[cfg(not(any(target_os = "l4re", target_os = "rtems")))]
         libc::SIGWINCH => " (SIGWINCH)",
         #[cfg(not(any(target_os = "haiku", target_os = "l4re")))]
         libc::SIGIO => " (SIGIO)",
diff --git a/library/std/src/sys/personality/mod.rs b/library/std/src/sys/personality/mod.rs
index 1a6ea1dafcb..68085d026c4 100644
--- a/library/std/src/sys/personality/mod.rs
+++ b/library/std/src/sys/personality/mod.rs
@@ -31,7 +31,7 @@ cfg_if::cfg_if! {
         target_os = "psp",
         target_os = "xous",
         target_os = "solid_asp3",
-        all(target_family = "unix", not(target_os = "espidf"), not(target_os = "l4re")),
+        all(target_family = "unix", not(target_os = "espidf"), not(target_os = "l4re"), not(target_os = "rtems")),
         all(target_vendor = "fortanix", target_env = "sgx"),
     ))] {
         mod gcc;
diff --git a/library/unwind/Cargo.toml b/library/unwind/Cargo.toml
index bbd1db8dfa5..590de31a678 100644
--- a/library/unwind/Cargo.toml
+++ b/library/unwind/Cargo.toml
@@ -34,3 +34,10 @@ llvm-libunwind = []
 # If crt-static is enabled, static link to `libunwind.a` provided by system
 # If crt-static is disabled, dynamic link to `libunwind.so` provided by system
 system-llvm-libunwind = []
+
+[lints.rust.unexpected_cfgs]
+level = "warn"
+check-cfg = [
+    # #[cfg(bootstrap)] rtems
+    'cfg(target_os, values("rtems"))',
+]
diff --git a/library/unwind/src/lib.rs b/library/unwind/src/lib.rs
index 250af912e07..26ed00bfbd5 100644
--- a/library/unwind/src/lib.rs
+++ b/library/unwind/src/lib.rs
@@ -22,6 +22,7 @@ cfg_if::cfg_if! {
         target_os = "l4re",
         target_os = "none",
         target_os = "espidf",
+        target_os = "rtems",
     ))] {
         // These "unix" family members do not have unwinder.
     } else if #[cfg(any(