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linux-user: Put the stack guard page at the top.

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There are no supported stack-grows-up targets.  We were putting
the guard page at the highest address, i.e. the bottom of the stack.
Use the maximum of host and guest page size for the guard size.

Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Edgar E. Iglesias <edgar.iglesias@gmail.com>
This commit is contained in:
Richard Henderson 2010-07-27 10:25:35 -07:00 committed by Edgar E. Iglesias
parent 9058abdd18
commit 60dcbcb5b1
1 changed files with 17 additions and 14 deletions
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31
linux-user/elfload.c
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@ -1002,29 +1002,32 @@ static abi_ulong copy_elf_strings(int argc,char ** argv, void **page,
static abi_ulong setup_arg_pages(abi_ulong p, struct linux_binprm *bprm,
struct image_info *info)
{
abi_ulong stack_base, size, error;
abi_ulong stack_base, size, error, guard;
int i;
/* Create enough stack to hold everything. If we don't use
* it for args, we'll use it for something else...
*/
it for args, we'll use it for something else. */
size = guest_stack_size;
if (size < MAX_ARG_PAGES*TARGET_PAGE_SIZE)
if (size < MAX_ARG_PAGES*TARGET_PAGE_SIZE) {
size = MAX_ARG_PAGES*TARGET_PAGE_SIZE;
error = target_mmap(0,
size + qemu_host_page_size,
PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS,
-1, 0);
}
guard = TARGET_PAGE_SIZE;
if (guard < qemu_real_host_page_size) {
guard = qemu_real_host_page_size;
}
error = target_mmap(0, size + guard, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (error == -1) {
perror("stk mmap");
perror("mmap stack");
exit(-1);
}
/* we reserve one extra page at the top of the stack as guard */
target_mprotect(error + size, qemu_host_page_size, PROT_NONE);
info->stack_limit = error;
stack_base = error + size - MAX_ARG_PAGES*TARGET_PAGE_SIZE;
/* We reserve one extra page at the top of the stack as guard. */
target_mprotect(error, guard, PROT_NONE);
info->stack_limit = error + guard;
stack_base = info->stack_limit + size - MAX_ARG_PAGES*TARGET_PAGE_SIZE;
p += stack_base;
for (i = 0 ; i < MAX_ARG_PAGES ; i++) {