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linux_raw: inline __NR_getrandom into ARM assembly #688

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Merged
merged 2 commits into from
Jun 9, 2025
Merged

linux_raw: inline __NR_getrandom into ARM assembly #688

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linux_raw: inline `__NR_getrandom` into ARM assembly
newpavlov Jun 9, 2025
a855695
Update changelog
newpavlov Jun 9, 2025
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4 changes: 4 additions & 0 deletions CHANGELOG.md
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Expand Up @@ -6,10 +6,14 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0

## [0.3.4] - UNRELEASED

### Changed
- Relax MSRV for the `linux_raw` opt-in backend on ARM targets [#688]

### Added
- `unsupported` opt-in backend [#667]

[#667]: https://github.com/rust-random/getrandom/pull/667
[#688]: https://github.com/rust-random/getrandom/pull/688

## [0.3.3] - 2025-05-09

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5 changes: 2 additions & 3 deletions src/backends/linux_raw.rs
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Expand Up @@ -13,7 +13,6 @@ unsafe fn getrandom_syscall(buf: *mut u8, buflen: usize, flags: u32) -> isize {
// Based on `rustix` and `linux-raw-sys` code.
cfg_if! {
if #[cfg(target_arch = "arm")] {
const __NR_getrandom: u32 = 384;
// In thumb-mode, r7 is the frame pointer and is not permitted to be used in
// an inline asm operand, so we have to use a different register and copy it
// into r7 inside the inline asm.
Expand All @@ -22,10 +21,10 @@ unsafe fn getrandom_syscall(buf: *mut u8, buflen: usize, flags: u32) -> isize {
// bother with it.
core::arch::asm!(
"mov {tmp}, r7",
"mov r7, {nr}",
// TODO(MSRV-1.82): replace with `nr = const __NR_getrandom,`
"mov r7, #384",
"svc 0",
"mov r7, {tmp}",
nr = const __NR_getrandom,
tmp = out(reg) _,
inlateout("r0") buf => r0,
in("r1") buflen,
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