Rollup merge of #126192 - bjorn3:redox_patches, r=petrochenkov

Various Redox OS fixes and add i686 Redox OS target

All of these come from the fork used by Redox OS available at https://gitlab.redox-os.org/redox-os/rust/-/commits/redox-2024-05-11/?ref_type=heads.

cc `@jackpot51`

9 files changed, 96 insertions, 3 deletions

diff --git a/compiler/rustc_data_structures/src/flock.rs b/compiler/rustc_data_structures/src/flock.rs
index 008565e4c7b..e03962a54ec 100644
--- a/compiler/rustc_data_structures/src/flock.rs
+++ b/compiler/rustc_data_structures/src/flock.rs
@@ -9,6 +9,10 @@ cfg_match! {
         mod linux;
         use linux as imp;
     }
+    cfg(target_os = "redox") => {
+        mod linux;
+        use linux as imp;
+    }
     cfg(unix) => {
         mod unix;
         use unix as imp;
diff --git a/compiler/rustc_target/src/spec/base/redox.rs b/compiler/rustc_target/src/spec/base/redox.rs
index 468fe478549..9070791e9df 100644
--- a/compiler/rustc_target/src/spec/base/redox.rs
+++ b/compiler/rustc_target/src/spec/base/redox.rs
@@ -1,4 +1,4 @@
-use crate::spec::{cvs, RelroLevel, TargetOptions};
+use crate::spec::{cvs, Cc, LinkerFlavor, Lld, RelroLevel, TargetOptions};
 
 pub fn opts() -> TargetOptions {
     TargetOptions {
@@ -12,6 +12,8 @@ pub fn opts() -> TargetOptions {
         has_thread_local: true,
         crt_static_default: true,
         crt_static_respected: true,
+        crt_static_allows_dylibs: true,
+        late_link_args: TargetOptions::link_args(LinkerFlavor::Gnu(Cc::Yes, Lld::No), &["-lgcc"]),
         ..Default::default()
     }
 }
diff --git a/compiler/rustc_target/src/spec/mod.rs b/compiler/rustc_target/src/spec/mod.rs
index adea2caabbe..42860b1059e 100644
--- a/compiler/rustc_target/src/spec/mod.rs
+++ b/compiler/rustc_target/src/spec/mod.rs
@@ -1647,6 +1647,7 @@ supported_targets! {
     ("x86_64-unknown-l4re-uclibc", x86_64_unknown_l4re_uclibc),
 
     ("aarch64-unknown-redox", aarch64_unknown_redox),
+    ("i686-unknown-redox", i686_unknown_redox),
     ("x86_64-unknown-redox", x86_64_unknown_redox),
 
     ("i386-apple-ios", i386_apple_ios),
diff --git a/compiler/rustc_target/src/spec/targets/i686_unknown_redox.rs b/compiler/rustc_target/src/spec/targets/i686_unknown_redox.rs
new file mode 100644
index 00000000000..83252fadb78
--- /dev/null
+++ b/compiler/rustc_target/src/spec/targets/i686_unknown_redox.rs
@@ -0,0 +1,27 @@
+use crate::spec::{base, Cc, LinkerFlavor, Lld, StackProbeType, Target};
+
+pub fn target() -> Target {
+    let mut base = base::redox::opts();
+    base.cpu = "pentiumpro".into();
+    base.plt_by_default = false;
+    base.max_atomic_width = Some(64);
+    base.add_pre_link_args(LinkerFlavor::Gnu(Cc::Yes, Lld::No), &["-m32"]);
+    // don't use probe-stack=inline-asm until rust#83139 and rust#84667 are resolved
+    base.stack_probes = StackProbeType::Call;
+
+    Target {
+        llvm_target: "i686-unknown-redox".into(),
+        metadata: crate::spec::TargetMetadata {
+            description: None,
+            tier: None,
+            host_tools: None,
+            std: None,
+        },
+        pointer_width: 32,
+        data_layout:
+            "e-m:e-p:32:32-p270:32:32-p271:32:32-p272:64:64-i128:128-f64:32:64-f80:32-n8:16:32-S128"
+                .into(),
+        arch: "x86".into(),
+        options: base,
+    }
+}
diff --git a/src/doc/rustc/src/SUMMARY.md b/src/doc/rustc/src/SUMMARY.md
index 201ace5ce3a..e76ebb8f8aa 100644
--- a/src/doc/rustc/src/SUMMARY.md
+++ b/src/doc/rustc/src/SUMMARY.md
@@ -71,6 +71,7 @@
     - [*-unknown-hermit](platform-support/hermit.md)
     - [\*-unknown-netbsd\*](platform-support/netbsd.md)
     - [*-unknown-openbsd](platform-support/openbsd.md)
+    - [*-unknown-redox](platform-support/redox.md)
     - [\*-unknown-uefi](platform-support/unknown-uefi.md)
     - [wasm32-wasip1](platform-support/wasm32-wasip1.md)
     - [wasm32-wasip1-threads](platform-support/wasm32-wasip1-threads.md)
diff --git a/src/doc/rustc/src/platform-support.md b/src/doc/rustc/src/platform-support.md
index e55bb3bd155..834e909c065 100644
--- a/src/doc/rustc/src/platform-support.md
+++ b/src/doc/rustc/src/platform-support.md
@@ -203,7 +203,7 @@ target | std | notes
 `x86_64-unknown-linux-gnux32` | ✓ | 64-bit Linux (x32 ABI) (kernel 4.15, glibc 2.27)
 [`x86_64-unknown-linux-ohos`](platform-support/openharmony.md) | ✓ | x86_64 OpenHarmony
 [`x86_64-unknown-none`](platform-support/x86_64-unknown-none.md) | * | Freestanding/bare-metal x86_64, softfloat
-`x86_64-unknown-redox` | ✓ | Redox OS
+[`x86_64-unknown-redox`](platform-support/redox.md) | ✓ | Redox OS
 [`x86_64-unknown-uefi`](platform-support/unknown-uefi.md) | ? | 64-bit UEFI
 
 [^x86_32-floats-x87]: Floating-point support on `i586` targets is non-compliant: the `x87` registers and instructions used for these targets do not provide IEEE-754-compliant behavior, in particular when it comes to rounding and NaN payload bits. See [issue #114479][x86-32-float-issue].
@@ -258,7 +258,7 @@ target | std | host | notes
 `aarch64-unknown-linux-gnu_ilp32` | ✓ | ✓ | ARM64 Linux (ILP32 ABI)
 [`aarch64-unknown-netbsd`](platform-support/netbsd.md) | ✓ | ✓ | ARM64 NetBSD
 [`aarch64-unknown-openbsd`](platform-support/openbsd.md) | ✓ | ✓ | ARM64 OpenBSD
-`aarch64-unknown-redox` | ? |  | ARM64 Redox OS
+[`aarch64-unknown-redox`](platform-support/redox.md) | ✓ |  | ARM64 Redox OS
 `aarch64-uwp-windows-msvc` | ✓ |  |
 `aarch64-wrs-vxworks` | ? |  |
 `aarch64_be-unknown-linux-gnu_ilp32` | ✓ | ✓ | ARM64 Linux (big-endian, ILP32 ABI)
@@ -300,6 +300,7 @@ target | std | host | notes
 [`i686-unknown-hurd-gnu`](platform-support/hurd.md) | ✓ | ✓ | 32-bit GNU/Hurd [^x86_32-floats-return-ABI]
 [`i686-unknown-netbsd`](platform-support/netbsd.md) | ✓ | ✓ | NetBSD/i386 with SSE2 [^x86_32-floats-return-ABI]
 [`i686-unknown-openbsd`](platform-support/openbsd.md) | ✓ | ✓ | 32-bit OpenBSD [^x86_32-floats-return-ABI]
+[`i686-unknown-redox`](platform-support/redox.md) | ✓ |  | i686 Redox OS
 `i686-uwp-windows-gnu` | ✓ |  | [^x86_32-floats-return-ABI]
 `i686-uwp-windows-msvc` | ✓ |  | [^x86_32-floats-return-ABI]
 [`i686-win7-windows-msvc`](platform-support/win7-windows-msvc.md) | ✓ |   | 32-bit Windows 7 support [^x86_32-floats-return-ABI]
diff --git a/src/doc/rustc/src/platform-support/redox.md b/src/doc/rustc/src/platform-support/redox.md
new file mode 100644
index 00000000000..1b3321956ef
--- /dev/null
+++ b/src/doc/rustc/src/platform-support/redox.md
@@ -0,0 +1,53 @@
+# `*-unknown-redox`
+
+**Tier: 2/3**
+
+Targets for the [Redox OS](https://redox-os.org/) operating
+system.
+
+Target triplets available so far:
+
+- `x86_64-unknown-redox` (tier 2)
+- `aarch64-unknown-redox` (tier 3)
+- `i686-unknown-redox` (tier 3)
+
+## Target maintainers
+
+- Jeremy Soller ([@jackpot51](https://github.com/jackpot51))
+
+## Requirements
+
+These targets are natively compiled and can be cross-compiled. Std is fully supported.
+
+The targets are only expected to work with the latest version of Redox OS as the ABI is not yet stable.
+
+`extern "C"` uses the official calling convention of the respective architectures.
+
+Redox OS binaries use ELF as file format.
+
+## Building the target
+
+You can build Rust with support for the targets by adding it to the `target` list in `config.toml`. In addition a copy of [relibc] needs to be present in the linker search path.
+
+```toml
+[build]
+build-stage = 1
+target = [
+    "<HOST_TARGET>",
+    "x86_64-unknown-redox",
+    "aarch64-unknown-redox",
+    "i686-unknown-redox",
+]
+```
+
+[relibc]: https://gitlab.redox-os.org/redox-os/relibc
+
+## Building Rust programs and testing
+
+Rust does not yet ship pre-compiled artifacts for Redox OS except for x86_64-unknown-redox.
+
+The easiest way to build and test programs for Redox OS is using [redoxer](https://gitlab.redox-os.org/redox-os/redoxer) which sets up the required compiler toolchain for building as well as runs programs inside a Redox OS VM using QEMU.
+
+## Cross-compilation toolchains and C code
+
+The target supports C code. Pre-compiled C toolchains can be found at <https://static.redox-os.org/toolchain/>.
diff --git a/src/tools/build-manifest/src/main.rs b/src/tools/build-manifest/src/main.rs
index b4d47cba7c5..a709aab7ce2 100644
--- a/src/tools/build-manifest/src/main.rs
+++ b/src/tools/build-manifest/src/main.rs
@@ -103,6 +103,7 @@ static TARGETS: &[&str] = &[
     "i686-unknown-freebsd",
     "i686-unknown-linux-gnu",
     "i686-unknown-linux-musl",
+    "i686-unknown-redox",
     "i686-unknown-uefi",
     "loongarch64-unknown-linux-gnu",
     "loongarch64-unknown-none",
diff --git a/tests/assembly/targets/targets-elf.rs b/tests/assembly/targets/targets-elf.rs
index 4c54fe639e3..b069e667bf5 100644
--- a/tests/assembly/targets/targets-elf.rs
+++ b/tests/assembly/targets/targets-elf.rs
@@ -228,6 +228,9 @@
 //@ revisions: i686_unknown_openbsd
 //@ [i686_unknown_openbsd] compile-flags: --target i686-unknown-openbsd
 //@ [i686_unknown_openbsd] needs-llvm-components: x86
+//@ revisions: i686_unknown_redox
+//@ [i686_unknown_redox] compile-flags: --target i686-unknown-redox
+//@ [i686_unknown_redox] needs-llvm-components: x86
 //@ revisions: i686_wrs_vxworks
 //@ [i686_wrs_vxworks] compile-flags: --target i686-wrs-vxworks
 //@ [i686_wrs_vxworks] needs-llvm-components: x86