Some(stackaddr - page_size..stackaddr)

}

#[forbid(unsafe_op_in_unsafe_fn)]

unsafe fn install_main_guard_default(page_size: usize) -> Option<Range<usize>> {

// Reallocate the last page of the stack.

// This ensures SIGBUS will be raised on

// read/write permissions and only then mprotect() it to

// no permissions at all. See issue #50313.

let stackptr = stack_start_aligned(page_size)?;

let result = mmap64(

stackptr,

page_size,

PROT_READ | PROT_WRITE,

MAP_PRIVATE | MAP_ANON | MAP_FIXED,

-1,

0,

);

let result = unsafe {

mmap64(

stackptr,

page_size,

PROT_READ | PROT_WRITE,

MAP_PRIVATE | MAP_ANON | MAP_FIXED,

-1,

0,

)

};

if result != stackptr || result == MAP_FAILED {

panic!("failed to allocate a guard page: {}", io::Error::last_os_error());

}

let result = mprotect(stackptr, page_size, PROT_NONE);

let result = unsafe { mprotect(stackptr, page_size, PROT_NONE) };

if result != 0 {

panic!("failed to protect the guard page: {}", io::Error::last_os_error());

}