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Rollup merge of #102854 - semarie:openbsd-immutablestack, r=m-ou-se

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openbsd: don't reallocate a guard page on the stack.

the kernel currently enforce that a stack is immutable. calling mmap(2) or  mprotect(2) to change it will result in EPERM, which generate a panic!().

so just do like for Linux, and trust the kernel to do the right thing.
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Dylan DPC 2022-10-13 18:19:19 +05:30 committed by GitHub
commit 376c81c94a
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10
library/std/src/sys/unix/thread.rs
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@ -766,6 +766,16 @@ pub mod guard {
const GUARD_PAGES: usize = 1;
let guard = guardaddr..guardaddr + GUARD_PAGES * page_size;
Some(guard)
} else if cfg!(target_os = "openbsd") {
// OpenBSD stack already includes a guard page, and stack is
// immutable.
//
// We'll just note where we expect rlimit to start
// faulting, so our handler can report "stack overflow", and
// trust that the kernel's own stack guard will work.
let stackptr = get_stack_start_aligned()?;
let stackaddr = stackptr.addr();
Some(stackaddr - page_size..stackaddr)
} else {
// Reallocate the last page of the stack.
// This ensures SIGBUS will be raised on