在 2022/3/19 1:18, Catalin Marinas 写道:
On Fri, Mar 18, 2022 at 11:58:22AM +0800, Tong Tiangen wrote:
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);
+}
[...]
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.
PROT_NONE is just a permission but since we don't have independent read
and write bits in the pte, we implement it as an invalid pte (bit 0
cleared). The other content of the pte is fine, so pte_pfn() should
still work. PTC could as well check this, I don't think it hurts.
You have a point and the logic should be:
pte_present(pte) && (pte_user(pte) || pte_user_exec(pte))
+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.
My point is that the (pmd_val(pmd) & PTE_VALID) check is superfluous
since that's covered by pmd_leaf() already.
Oh，i got it，you're right and these will be fixed in v2.
Considering all your suggestions, The final logic should be:
+#define pte_user(pte) (!!(pte_val(pte) & PTE_USER))
+#define pmd_user(pmd) pte_user(pmd_pte(pmd))
+#define pmd_user_exec(pmd) pte_user_exec(pmd_pte(pmd))
+#define pud_user(pud) pte_user(pud_pte(pud))
+static inline bool pte_user_accessible_page(pte_t pte)
+{
+ return pte_present(pte) && (pte_user(pte)|| pte_user_exec(pte));
+}
+static inline bool pmd_user_accessible_page(pmd_t pmd)
+{
+ return pmd_present(pmd) && (pmd_user(pmd)|| pmd_user_exec(pmd));
+}
+static inline bool pud_user_accessible_page(pud_t pud)
+{
+ return pud_present(pud) && pud_user(pud);
+}
