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allocate 2 pages more than requested for guard pages #33

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Merged
merged 1 commit into from
May 9, 2020
Merged

allocate 2 pages more than requested for guard pages #33

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4 changes: 2 additions & 2 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -137,15 +137,15 @@ psm_stack_manipulation! {
fn _grow<F: FnOnce()>(stack_size: usize, callback: F) {
// Calculate a number of pages we want to allocate for the new stack.
// For maximum portability we want to produce a stack that is aligned to a page and has
// a size that’s a multiple of page size. Furthermore we want to allocate an extra page
// a size that’s a multiple of page size. Furthermore we want to allocate two extras pages
// for the stack guard. To achieve that we do our calculations in number of pages and
// convert to bytes last.
// FIXME: consider caching the page size.
let page_size = unsafe { libc::sysconf(libc::_SC_PAGE_SIZE) } as usize;
let requested_pages = stack_size
.checked_add(page_size - 1)
.expect("unreasonably large stack requested") / page_size;
let stack_pages = std::cmp::max(1, requested_pages) + 1;
let stack_pages = std::cmp::max(1, requested_pages) + 2;
let stack_bytes = stack_pages.checked_mul(page_size)
.expect("unreasonably large stack requesteed");

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