Skip mapping the shadow stack as a writable page and the redundant memory
zeroing.
Currently, the shadow stack is allocated using alloc_page(), then mapped as
a writable page, zeroed, and finally mapped as a shadow stack page. The
memory zeroing is redundant as alloc_page() already does that.
Signed-off-by: Chao Gao <chao.gao@xxxxxxxxx>
---
x86/cet.c | 9 +--------
1 file changed, 1 insertion(+), 8 deletions(-)
diff --git a/x86/cet.c b/x86/cet.c
index 51a54a50..214976f9 100644
--- a/x86/cet.c
+++ b/x86/cet.c
@@ -67,7 +67,6 @@ int main(int ac, char **av)
{
char *shstk_virt;
unsigned long shstk_phys;
- unsigned long *ptep;
pteval_t pte = 0;
bool rvc;
@@ -90,14 +89,8 @@ int main(int ac, char **av)
shstk_phys = (unsigned long)virt_to_phys(alloc_page());
/* Install the new page. */
- pte = shstk_phys | PT_PRESENT_MASK | PT_WRITABLE_MASK | PT_USER_MASK;
+ pte = shstk_phys | PT_PRESENT_MASK | PT_USER_MASK | PT_DIRTY_MASK;
install_pte(current_page_table(), 1, shstk_virt, pte, 0);
- memset(shstk_virt, 0x0, PAGE_SIZE);
-
- /* Mark it as shadow-stack page. */
- ptep = get_pte_level(current_page_table(), shstk_virt, 1);
- *ptep &= ~PT_WRITABLE_MASK;
- *ptep |= PT_DIRTY_MASK;
/* Flush the paging cache. */
invlpg((void *)shstk_virt);
--
2.47.1
