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oslib-posix: add helpers for stack alloc and free

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the allocated stack will be adjusted to the minimum supported stack size
by the OS and rounded up to be a multiple of the system pagesize.
Additionally an architecture dependent guard page is added to the stack
to catch stack overflows.

Signed-off-by: Peter Lieven <pl@kamp.de>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Peter Lieven 2016-09-27 11:58:40 +02:00 • committed by Kevin Wolf
parent 74e1ae7c0b
commit 8737d9e0c4
2 changed files with 69 additions and 0 deletions
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42
util/oslib-posix.c
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@ -499,3 +499,45 @@ pid_t qemu_fork(Error **errp)
}
return pid;
}
void *qemu_alloc_stack(size_t *sz)
{
void *ptr, *guardpage;
size_t pagesz = getpagesize();
#ifdef _SC_THREAD_STACK_MIN
/* avoid stacks smaller than _SC_THREAD_STACK_MIN */
long min_stack_sz = sysconf(_SC_THREAD_STACK_MIN);
*sz = MAX(MAX(min_stack_sz, 0), *sz);
#endif
/* adjust stack size to a multiple of the page size */
*sz = ROUND_UP(*sz, pagesz);
/* allocate one extra page for the guard page */
*sz += pagesz;
ptr = mmap(NULL, *sz, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (ptr == MAP_FAILED) {
abort();
}
#if defined(HOST_IA64)
/* separate register stack */
guardpage = ptr + (((*sz - pagesz) / 2) & ~pagesz);
#elif defined(HOST_HPPA)
/* stack grows up */
guardpage = ptr + *sz - pagesz;
#else
/* stack grows down */
guardpage = ptr;
#endif
if (mprotect(guardpage, pagesz, PROT_NONE) != 0) {
abort();
}
return ptr;
}
void qemu_free_stack(void *stack, size_t sz)
{
munmap(stack, sz);
}