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Linux Raw: Clarify x86_64 linux_raw syscall number. #687

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Merged
merged 1 commit into from
Jun 9, 2025
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Linux Raw: Clarify x86_64 linux_raw syscall number. #687

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15 changes: 11 additions & 4 deletions src/backends/linux_raw.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,7 @@ 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")] {
// TODO(MSRV-1.78): Also check `target_abi = "eabi"`.
// 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 @@ -32,6 +33,11 @@ unsafe fn getrandom_syscall(buf: *mut u8, buflen: usize, flags: u32) -> isize {
options(nostack, preserves_flags)
);
} else if #[cfg(target_arch = "aarch64")] {
// TODO(MSRV-1.78): Also check `any(target_abi = "", target_abi = "ilp32")` above.
// According the the ILP32 patch for the kernel that hasn't yet
// been merged into the mainline, "AARCH64/ILP32 ABI uses standard
// syscall table [...] with the exceptions listed below," where
// getrandom is not mentioned as an exception.
const __NR_getrandom: u32 = 278;
core::arch::asm!(
"svc 0",
Expand All @@ -42,6 +48,7 @@ unsafe fn getrandom_syscall(buf: *mut u8, buflen: usize, flags: u32) -> isize {
options(nostack, preserves_flags)
);
} else if #[cfg(target_arch = "loongarch64")] {
// TODO(MSRV-1.78): Also check `any(target_abi = "", target_abi = "ilp32")` above.
const __NR_getrandom: u32 = 278;
core::arch::asm!(
"syscall 0",
Expand Down Expand Up @@ -86,10 +93,10 @@ unsafe fn getrandom_syscall(buf: *mut u8, buflen: usize, flags: u32) -> isize {
options(nostack, preserves_flags)
);
} else if #[cfg(target_arch = "x86_64")] {
#[cfg(target_pointer_width = "64")]
const __NR_getrandom: u32 = 318;
#[cfg(target_pointer_width = "32")]
const __NR_getrandom: u32 = (1 << 30) + 318;
// TODO(MSRV-1.78): Add `any(target_abi = "", target_abi = "x32")` above.
const __X32_SYSCALL_BIT: u32 = 0x40000000;
const OFFSET: u32 = if cfg!(target_pointer_width = "32") { __X32_SYSCALL_BIT } else { 0 };
const __NR_getrandom: u32 = OFFSET + 318;

core::arch::asm!(
"syscall",
Expand Down