Re: [PATCH v21 08/26] x86/mm: Introduce _PAGE_COW

Borislav Petkov
2021-03-04T00:29:35Z

On Tue, Mar 02, 2021 at 03:46:31PM -0800, Yu, Yu-cheng wrote:
> There is a problem of doing that: pmd_write() is defined after this
> function. Maybe we can declare it first, or leave this as-is?

Or a third option: you lift those two functions in a prepatch and then
in this patch use them directly.

Combined diff ontop:

---
diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 1a6c0784af0a..b7e4d031ce22 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -209,6 +209,18 @@ static inline int pte_write(pte_t pte)
return (pte_flags(pte) & _PAGE_RW) || pte_shstk(pte);
}

+#define pmd_write pmd_write
+static inline int pmd_write(pmd_t pmd)
+{
+ return (pmd_flags(pmd) & _PAGE_RW) || pmd_shstk(pmd);
+}
+
+#define pud_write pud_write
+static inline int pud_write(pud_t pud)
+{
+ return pud_flags(pud) & _PAGE_RW;
+}
+
static inline int pte_huge(pte_t pte)
{
return pte_flags(pte) & _PAGE_PSE;
@@ -540,7 +552,7 @@ static inline pmd_t pmd_mkdirty(pmd_t pmd)
pmdval_t dirty = _PAGE_DIRTY;

/* Avoid creating (HW)Dirty=1, Write=0 PMDs */
- if (cpu_feature_enabled(X86_FEATURE_SHSTK) && !(pmd_flags(pmd) & _PAGE_RW))
+ if (cpu_feature_enabled(X86_FEATURE_SHSTK) && !pmd_write(pmd))
dirty = _PAGE_COW;

return pmd_set_flags(pmd, dirty | _PAGE_SOFT_DIRTY);
@@ -636,7 +648,7 @@ static inline pud_t pud_mkdirty(pud_t pud)
pudval_t dirty = _PAGE_DIRTY;

/* Avoid creating (HW)Dirty=1, Write=0 PUDs */
- if (cpu_feature_enabled(X86_FEATURE_SHSTK) && !(pud_flags(pud) & _PAGE_RW))
+ if (cpu_feature_enabled(X86_FEATURE_SHSTK) && !pud_write(pud))
dirty = _PAGE_COW;

return pud_set_flags(pud, dirty | _PAGE_SOFT_DIRTY);
@@ -1273,12 +1285,6 @@ extern int pmdp_clear_flush_young(struct vm_area_struct *vma,
unsigned long address, pmd_t *pmdp);

-#define pmd_write pmd_write
-static inline int pmd_write(pmd_t pmd)
-{
- return (pmd_flags(pmd) & _PAGE_RW) || pmd_shstk(pmd);
-}
-
#define __HAVE_ARCH_PMDP_HUGE_GET_AND_CLEAR
static inline pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm, unsigned long addr,
pmd_t *pmdp)
@@ -1300,12 +1306,6 @@ static inline void pmdp_set_wrprotect(struct mm_struct *mm,
clear_bit(_PAGE_BIT_RW, (unsigned long *)pmdp);
}

-#define pud_write pud_write
-static inline int pud_write(pud_t pud)
-{
- return pud_flags(pud) & _PAGE_RW;
-}
-
#ifndef pmdp_establish
#define pmdp_establish pmdp_establish
static inline pmd_t pmdp_establish(struct vm_area_struct *vma,

--
Regards/Gruss,
Boris.