在 2022/3/18 3:00, Catalin Marinas 写道:
On Thu, Mar 17, 2022 at 02:12:02PM +0000, Tong Tiangen wrote:
@@ -628,6 +647,25 @@ static inline unsigned long pmd_page_vaddr(pmd_t pmd)
#define pud_leaf(pud) pud_sect(pud)
#define pud_valid(pud) pte_valid(pud_pte(pud))
+#ifdef CONFIG_PAGE_TABLE_CHECK
+static inline bool pte_user_accessible_page(pte_t pte)
+{
+ return (pte_val(pte) & PTE_VALID) && (pte_val(pte) & PTE_USER);
+}
There is another class of user mappings, execute-only, that have both
PTE_USER and PTE_UXN cleared. So this logic should be:
pte_valid(pte) && (pte_user(pte) || pte_user_exec(pte))
with pte_user() as:
#define pte_user(pte) (!!(pte_val(pte) & PTE_USER))
Good suggestion, the PTC(page table check) can cover UXN page and
pte_user(pte) helper is required.
Do we care about PROT_NONE mappings here? They have the valid bit
cleared but pte_present() is true.
PTC will not check this special type(PROT_NONE) of page.
+static inline bool pmd_user_accessible_page(pmd_t pmd)
+{
+ return pmd_leaf(pmd) && (pmd_val(pmd) & PTE_VALID) &&
+ (pmd_val(pmd) & PTE_USER);
+}
pmd_leaf() implies valid, so you can skip it if that's the aim.
PTC only checks whether the memory block corresponding to the pmd_leaf
type can access, for !pmd_leaf, PTC checks at the pte level. So i think
this is necessary.
Similar comment to the pte variant on execute-only and PROT_NONE
mappings
Same considerations as above.
Thanks.
Tong
