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Map the stack guard page with max protection on NetBSD #50331

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Merged
merged 2 commits into from
May 10, 2018
Merged

Map the stack guard page with max protection on NetBSD #50331

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7c2304d
Map the stack guard page with max protection on NetBSD
MartinHusemann Apr 30, 2018
244e24a
Add comments and unify guard page setup.
MartinHusemann May 2, 2018
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13 changes: 11 additions & 2 deletions src/libstd/sys/unix/thread.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -326,13 +326,22 @@ pub mod guard {
// Reallocate the last page of the stack.
// This ensures SIGBUS will be raised on
// stack overflow.
let result = mmap(stackaddr, PAGE_SIZE, PROT_NONE,
// Systems which enforce strict PAX MPROTECT do not allow
// to mprotect() a mapping with less restrictive permissions
// than the initial mmap() used, so we mmap() here with
// read/write permissions and only then mprotect() it to
// no permissions at all. See issue #50313.
let result = mmap(stackaddr, PAGE_SIZE, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANON | MAP_FIXED, -1, 0);

if result != stackaddr || result == MAP_FAILED {
panic!("failed to allocate a guard page");
}

let result = mprotect(stackaddr, PAGE_SIZE, PROT_NONE);
if result != 0 {
panic!("failed to protect the guard page");
}

let guardaddr = stackaddr as usize;
let offset = if cfg!(target_os = "freebsd") {
2
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