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Merged
rust-bors merged 1 commit into from
Mar 23, 2026
+13 −0
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Skip stack_start_aligned for immediate-abort #153936

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13 changes: 13 additions & 0 deletions library/std/src/sys/pal/unix/stack_overflow.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -429,6 +429,11 @@ mod imp {

#[forbid(unsafe_op_in_unsafe_fn)]
unsafe fn install_main_guard_linux(page_size: usize) -> Option<Range<usize>> {
// See the corresponding conditional in init().
// Avoid stack_start_aligned, which makes slow syscalls to read /proc/self/maps
if cfg!(panic = "immediate-abort") {
return None;
}
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@bjorn3 bjorn3 Mar 16, 2026

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This should also be done for other targets where the OS already provides guard pages for the stack, right?

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@danielzgtg danielzgtg Mar 16, 2026

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Added to install_main_guard_bsds

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@joboet joboet Mar 20, 2026

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The FreeBSD code can also be skipped.

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@danielzgtg danielzgtg Mar 20, 2026

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Added to install_main_guard_freebsd

// Linux doesn't allocate the whole stack right away, and
// the kernel has its own stack-guard mechanism to fault
// when growing too close to an existing mapping. If we map
Expand Down Expand Up @@ -456,6 +461,10 @@ mod imp {
#[forbid(unsafe_op_in_unsafe_fn)]
#[cfg(target_os = "freebsd")]
unsafe fn install_main_guard_freebsd(page_size: usize) -> Option<Range<usize>> {
// See the corresponding conditional in install_main_guard_linux().
if cfg!(panic = "immediate-abort") {
return None;
}
// FreeBSD's stack autogrows, and optionally includes a guard page
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@Mark-Simulacrum Mark-Simulacrum Mar 22, 2026

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@asomers do you have context on what this "optionally" here is referring to? Not really related to this PR but since we intend to guarantee stack guards, I'm wondering if we should be branching on something and defining our own if FreeBSD didn't?

// at the bottom. If we try to remap the bottom of the stack
// ourselves, FreeBSD's guard page moves upwards. So we'll just use
Expand Down Expand Up @@ -489,6 +498,10 @@ mod imp {

#[forbid(unsafe_op_in_unsafe_fn)]
unsafe fn install_main_guard_bsds(page_size: usize) -> Option<Range<usize>> {
// See the corresponding conditional in install_main_guard_linux().
if cfg!(panic = "immediate-abort") {
return None;
}
// OpenBSD stack already includes a guard page, and stack is
// immutable.
// NetBSD stack includes the guard page.
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