Illegal instruction mcr on ARM926EJ-S

[oold]

Verification

• I searched for recent similar issues at https://github.com/rust-lang/rustup/issues?q=is%3Aissue+is%3Aopen%2Cclosed and found no duplicates.
• I am on the latest version of Rustup according to https://github.com/rust-lang/rustup/tags and am still able to reproduce my issue.

Problem

Binaries compiled for ARM926EJ-S fail with SIGILL.

GDB output:

Program received signal SIGILL, Illegal instruction.
0xb6e514c4 in ?? ()
(gdb) display/i $pc
1: x/i $pc
=> 0xb6e514c4:  mcr     15, 0, r0, cr7, cr10, {5}

Steps

1. Build binary with

set RUSTFLAGS=-C target-cpu=arm926ej-s -C linker=arm-unknown-linux-gnueabi-gcc
cargo build --bin cf-debug-helper-server --release --target=arm-unknown-linux-gnueabi

2. Run binary on target system.
3. Illegal instruction

Possible Solution(s)

No response

Notes

No response

Rustup version

rustup 1.28.1 (f9edccde0 2025-03-05)
info: This is the version for the rustup toolchain manager, not the rustc compiler.
info: The currently active `rustc` version is `rustc 1.85.0 (4d91de4e4 2025-02-17)`

Installed toolchains

Default host: x86_64-pc-windows-msvc
rustup home:  C:\Users\oli011\.rustup

installed toolchains
--------------------
stable-x86_64-pc-windows-msvc (active, default)

active toolchain
----------------
name: stable-x86_64-pc-windows-msvc
active because: it's the default toolchain
installed targets:
  arm-unknown-linux-gnueabi
  x86_64-pc-windows-msvc

OS version

Build: Windows 11 26100.3476
Target: Linux 3.10.108

[oold]

Backtrace with symbols:

Program received signal SIGILL, Illegal instruction.
core::sync::atomic::atomic_store<isize> (dst=0xb6f49514 <std::sys::pal::unix::args::imp::ARGC>,
    val=1, order=core::sync::atomic::Ordering::Relaxed)
    at C:\Users\oli011\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\core\src\sync/atomic.rs:3716
3716            match order {
(gdb) bt
#0  core::sync::atomic::atomic_store<isize> (
    dst=0xb6f49514 <std::sys::pal::unix::args::imp::ARGC>, val=1,
    order=core::sync::atomic::Ordering::Relaxed)
    at C:\Users\oli011\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\core\src\sync/atomic.rs:3716
rust-lang/rustup#1  0xb6d0d040 in core::sync::atomic::AtomicIsize::store (
    self=0xb6f49514 <std::sys::pal::unix::args::imp::ARGC>, val=1,
    order=core::sync::atomic::Ordering::Relaxed)
    at C:\Users\oli011\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\core\src\sync/atomic.rs:2728
rust-lang/rustup#2  0xb6d82edc in std::sys::pal::unix::args::imp::really_init (argc=1, argv=0xbea69de4)
    at src\sys\pal\unix/args.rs:136
rust-lang/rustup#3  0xb6d82f24 in std::sys::pal::unix::args::imp::ARGV_INIT_ARRAY::init_wrapper (argc=1,
    argv=0xbea69de4, _envp=0xbea69dec) at src\sys\pal\unix/args.rs:163
rust-lang/rustup#4  0xb658e9d8 in __libc_start_main () from target:/lib/libc.so.6
rust-lang/rustup#5  0xb67b3bd0 in _start () at ../sysdeps/arm/start.S:105
Backtrace stopped: previous frame identical to this frame (corrupt stack?)

[rami3l]

@rustbot transfer rust-lang/rust

[rami3l]

(Transferring since it looks like it's about rustup's use of Rust instead of rustup itself. Please correct me if this is not the case.)

[taiki-e]

IIRC ARM926EJ-S is Armv5TE, so I think you have to use armv5te-unknown-linux-gnueabi (Armv5TE) instead of arm-unknown-linux-gnueabi (Armv6).

[oold]

Using armv5te-unknown-linux-gnueabi also results in an illegal mcr instruction being emitted.

[taiki-e]

Hmm, maybe just changing the target is not enough, because if the linked library is armv6, the final binary will be too.

Could you tell us the result of the arm-unknown-linux-gnueabi-readelf --arch-specific /path/to/binary?

[oold]

Oh, sorry. That was a user error. I've uploaded the wrong binary. It works with armv5te-unknown-linux-gnueabi.