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Auto merge of #88952 - skrap:add-armv7-uclibc, r=nagisa
Add new tier-3 target: armv7-unknown-linux-uclibceabihf This change adds a new tier-3 target: armv7-unknown-linux-uclibceabihf This target is primarily used in embedded linux devices where system resources are slim and glibc is deemed too heavyweight. Cross compilation C toolchains are available [here](https://toolchains.bootlin.com/) or via [buildroot](https://buildroot.org). The change is based largely on a previous PR #79380 with a few minor modifications. The author of that PR was unable to push the PR forward, and graciously allowed me to take it over. Per the [target tier 3 policy](https://github.com/rust-lang/rfcs/blob/master/text/2803-target-tier-policy.md), I volunteer to be the "target maintainer". This is my first PR to Rust itself, so I apologize if I've missed things!
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‎compiler/rustc_codegen_llvm/src/callee.rs

+1-1
Original file line numberDiff line numberDiff line change
@@ -175,7 +175,7 @@ pub fn get_fn(cx: &CodegenCx<'ll, 'tcx>, instance: Instance<'tcx>) -> &'ll Value
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// should use dllimport for functions.
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if cx.use_dll_storage_attrs
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&& tcx.is_dllimport_foreign_item(instance_def_id)
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&& tcx.sess.target.env != "gnu"
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&& !matches!(tcx.sess.target.env.as_ref(), "gnu" | "uclibc")
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{
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llvm::LLVMSetDLLStorageClass(llfn, llvm::DLLStorageClass::DllImport);
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}

‎compiler/rustc_middle/src/ty/layout.rs

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@@ -3012,7 +3012,7 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
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};
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let target = &self.tcx.sess.target;
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let target_env_gnu_like = matches!(&target.env[..], "gnu" | "musl");
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let target_env_gnu_like = matches!(&target.env[..], "gnu" | "musl" | "uclibc");
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let win_x64_gnu = target.os == "windows" && target.arch == "x86_64" && target.env == "gnu";
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let linux_s390x_gnu_like =
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target.os == "linux" && target.arch == "s390x" && target_env_gnu_like;
@@ -3110,7 +3110,7 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
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if arg.layout.is_zst() {
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// For some forsaken reason, x86_64-pc-windows-gnu
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// doesn't ignore zero-sized struct arguments.
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// The same is true for {s390x,sparc64,powerpc}-unknown-linux-{gnu,musl}.
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// The same is true for {s390x,sparc64,powerpc}-unknown-linux-{gnu,musl,uclibc}.
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if is_return
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|| rust_abi
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|| (!win_x64_gnu

‎compiler/rustc_target/src/spec/armv7_unknown_linux_uclibceabihf.rs

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@@ -0,0 +1,24 @@
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use crate::spec::{Target, TargetOptions};
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// This target is for uclibc Linux on ARMv7 without NEON or
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// thumb-mode. See the thumbv7neon variant for enabling both.
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pub fn target() -> Target {
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let base = super::linux_uclibc_base::opts();
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Target {
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llvm_target: "armv7-unknown-linux-gnueabihf".to_string(),
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pointer_width: 32,
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data_layout: "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64".to_string(),
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arch: "arm".to_string(),
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options: TargetOptions {
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// Info about features at https://wiki.debian.org/ArmHardFloatPort
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features: "+v7,+vfp3,-d32,+thumb2,-neon".to_string(),
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cpu: "generic".to_string(),
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max_atomic_width: Some(64),
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mcount: "_mcount".to_string(),
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abi: "eabihf".to_string(),
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..base
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},
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}
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}

‎compiler/rustc_target/src/spec/mod.rs

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@@ -952,6 +952,8 @@ supported_targets! {
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("bpfel-unknown-none", bpfel_unknown_none),
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("armv6k-nintendo-3ds", armv6k_nintendo_3ds),
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("armv7-unknown-linux-uclibceabihf", armv7_unknown_linux_uclibceabihf),
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}
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/// Warnings encountered when parsing the target `json`.

‎library/std/src/sys/unix/mod.rs

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@@ -307,6 +307,9 @@ cfg_if::cfg_if! {
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#[link(name = "zircon")]
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#[link(name = "fdio")]
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extern "C" {}
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} else if #[cfg(all(target_os = "linux", target_env = "uclibc"))] {
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#[link(name = "dl")]
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extern "C" {}
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}
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}
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‎library/std/src/sys/unix/thread.rs

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@@ -594,7 +594,8 @@ pub mod guard {
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Some(stackaddr - guardsize..stackaddr)
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} else if cfg!(all(target_os = "linux", target_env = "musl")) {
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Some(stackaddr - guardsize..stackaddr)
597-
} else if cfg!(all(target_os = "linux", target_env = "gnu")) {
597+
} else if cfg!(all(target_os = "linux", any(target_env = "gnu", target_env = "uclibc")))
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{
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// glibc used to include the guard area within the stack, as noted in the BUGS
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// section of `man pthread_attr_getguardsize`. This has been corrected starting
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// with glibc 2.27, and in some distro backports, so the guard is now placed at the

‎library/unwind/src/lib.rs

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@@ -63,7 +63,7 @@ cfg_if::cfg_if! {
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// don't want to duplicate it here.
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#[cfg(all(
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target_os = "linux",
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target_env = "gnu",
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any(target_env = "gnu", target_env = "uclibc"),
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not(feature = "llvm-libunwind"),
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not(feature = "system-llvm-libunwind")
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))]
@@ -72,7 +72,7 @@ extern "C" {}
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#[cfg(all(
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target_os = "linux",
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target_env = "gnu",
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any(target_env = "gnu", target_env = "uclibc"),
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not(feature = "llvm-libunwind"),
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feature = "system-llvm-libunwind"
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))]

‎src/doc/rustc/src/platform-support.md

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@@ -220,6 +220,7 @@ target | std | host | notes
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`armv6-unknown-netbsd-eabihf` | ? | |
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`armv6k-nintendo-3ds` | * | | ARMv6K Nintendo 3DS, Horizon (Requires devkitARM toolchain)
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`armv7-apple-ios` | ✓ | | ARMv7 iOS, Cortex-a8
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`armv7-unknown-linux-uclibceabihf` | ✓ | ? | ARMv7 Linux uClibc
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`armv7-unknown-freebsd` | ✓ | ✓ | ARMv7 FreeBSD
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`armv7-unknown-netbsd-eabihf` | ✓ | ✓ |
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`armv7-wrs-vxworks-eabihf` | ? | |

‎src/doc/rustc/src/platform-support/armv7-unknown-linux-uclibceabihf.md

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@@ -0,0 +1,66 @@
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# armv7-unknown-linux-uclibceabihf
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**Tier: 3**
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This tier supports the ARMv7 processor running a Linux kernel and uClibc-ng standard library. It provides full support for rust and the rust standard library.
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## Designated Developers
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* [@skrap](https://github.com/skrap)
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## Requirements
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This target is cross compiled, and requires a cross toolchain. You can find suitable pre-built toolchains at [bootlin](https://toolchains.bootlin.com/) or build one yourself via [buildroot](https://buildroot.org).
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## Building
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### Get a C toolchain
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Compiling rust for this target has been tested on `x86_64` linux hosts. Other host types have not been tested, but may work, if you can find a suitable cross compilation toolchain for them.
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If you don't already have a suitable toolchain, download one [here](https://toolchains.bootlin.com/downloads/releases/toolchains/armv7-eabihf/tarballs/armv7-eabihf--uclibc--bleeding-edge-2020.08-1.tar.bz2), and unpack it into a directory.
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### Configure rust
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The target can be built by enabling it for a `rustc` build, by placing the following in `config.toml`:
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27+
```toml
28+
[build]
29+
target = ["armv7-unknown-linux-uclibceabihf"]
30+
stage = 2
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[target.armv7-unknown-linux-uclibceabihf]
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# ADJUST THIS PATH TO POINT AT YOUR TOOLCHAIN
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cc = "/TOOLCHAIN_PATH/bin/arm-buildroot-linux-uclibcgnueabihf-gcc"
35+
```
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### Build
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```sh
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# in rust dir
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./x.py build --stage 2
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```
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## Building and Running Rust Programs
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To test cross-compiled binaries on a `x86_64` system, you can use the `qemu-arm` [userspace emulation](https://qemu-project.gitlab.io/qemu/user/main.html) program. This avoids having a full emulated ARM system by doing dynamic binary translation and dynamic system call translation. It lets you run ARM programs directly on your `x86_64` kernel. It's very convenient!
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To use:
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* Install `qemu-arm` according to your distro.
51+
* Link your built toolchain via:
52+
* `rustup toolchain link stage2 ${RUST}/build/x86_64-unknown-linux-gnu/stage2`
53+
* Create a test program
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```sh
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cargo new hello_world
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cd hello_world
58+
```
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* Build and run
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```sh
63+
CARGO_TARGET_ARMV7_UNKNOWN_LINUX_UCLIBCEABIHF_RUNNER="qemu-arm -L ${TOOLCHAIN}/arm-buildroot-linux-uclibcgnueabihf/sysroot/" \
64+
CARGO_TARGET_ARMV7_UNKNOWN_LINUX_UCLIBCEABIHF_LINKER=${TOOLCHAIN}/bin/arm-buildroot-linux-uclibcgnueabihf-gcc \
65+
cargo +stage2 run --target armv7-unknown-linux-uclibceabihf
66+
```

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