[PATCH 1/2] arm64/mm: Move __check_safe_pte_update()

[Anshuman Khandual]

The page table entry print helpers and related macros which are defined in
<linux/pgtable.h> will not be accessible in platform <asm/pgtable.h> which
is basically caused by cycling dependency.

Move __check_safe_pte_update() inside arch/arm64/mm/mmu.c as a preparation
for subsequent usage of the afore mentioned generic MM helpers.

This does not cause any functional change.

Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
---
Should __check_safe_pte_update() be wrapped in #ifdef CONFIG_DEBUG_VM
along with dropping off current IS_ENABLED() test. That would ensure
the function never gets called when CONFIG_DEBUG_VM is disabled. That
will preserve current behaviour as the inline function gets dropped
when CONFIG_DEBUG_VM remains disabled.

 arch/arm64/include/asm/pgtable.h | 47 +-------------------------------
 arch/arm64/mm/mmu.c              | 45 ++++++++++++++++++++++++++++++
 2 files changed, 46 insertions(+), 46 deletions(-)

diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index e89ec5f4787b..61fbfab3e06e 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -387,52 +387,7 @@ static inline pte_t __ptep_get(pte_t *ptep)
 extern void __sync_icache_dcache(pte_t pteval);
 bool pgattr_change_is_safe(pteval_t old, pteval_t new);
 
-/*
- * PTE bits configuration in the presence of hardware Dirty Bit Management
- * (PTE_WRITE == PTE_DBM):
- *
- * Dirty  Writable | PTE_RDONLY  PTE_WRITE  PTE_DIRTY (sw)
- *   0      0      |   1           0          0
- *   0      1      |   1           1          0
- *   1      0      |   1           0          1
- *   1      1      |   0           1          x
- *
- * When hardware DBM is not present, the software PTE_DIRTY bit is updated via
- * the page fault mechanism. Checking the dirty status of a pte becomes:
- *
- *   PTE_DIRTY || (PTE_WRITE && !PTE_RDONLY)
- */
-
-static inline void __check_safe_pte_update(struct mm_struct *mm, pte_t *ptep,
-					   pte_t pte)
-{
-	pte_t old_pte;
-
-	if (!IS_ENABLED(CONFIG_DEBUG_VM))
-		return;
-
-	old_pte = __ptep_get(ptep);
-
-	if (!pte_valid(old_pte) || !pte_valid(pte))
-		return;
-	if (mm != current->active_mm && atomic_read(&mm->mm_users) <= 1)
-		return;
-
-	/*
-	 * Check for potential race with hardware updates of the pte
-	 * (__ptep_set_access_flags safely changes valid ptes without going
-	 * through an invalid entry).
-	 */
-	VM_WARN_ONCE(!pte_young(pte),
-		     "%s: racy access flag clearing: 0x%016llx -> 0x%016llx",
-		     __func__, pte_val(old_pte), pte_val(pte));
-	VM_WARN_ONCE(pte_write(old_pte) && !pte_dirty(pte),
-		     "%s: racy dirty state clearing: 0x%016llx -> 0x%016llx",
-		     __func__, pte_val(old_pte), pte_val(pte));
-	VM_WARN_ONCE(!pgattr_change_is_safe(pte_val(old_pte), pte_val(pte)),
-		     "%s: unsafe attribute change: 0x%016llx -> 0x%016llx",
-		     __func__, pte_val(old_pte), pte_val(pte));
-}
+void __check_safe_pte_update(struct mm_struct *mm, pte_t *ptep, pte_t pte);
 
 static inline void __sync_cache_and_tags(pte_t pte, unsigned int nr_pages)
 {
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 79d90226fd5d..e9c66d26bc0a 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -2392,4 +2392,49 @@ int arch_set_user_pkey_access(int pkey, unsigned long init_val)
 
 	return 0;
 }
+
+/*
+ * PTE bits configuration in the presence of hardware Dirty Bit Management
+ * (PTE_WRITE == PTE_DBM):
+ *
+ * Dirty  Writable | PTE_RDONLY  PTE_WRITE  PTE_DIRTY (sw)
+ *   0      0      |   1           0          0
+ *   0      1      |   1           1          0
+ *   1      0      |   1           0          1
+ *   1      1      |   0           1          x
+ *
+ * When hardware DBM is not present, the software PTE_DIRTY bit is updated via
+ * the page fault mechanism. Checking the dirty status of a pte becomes:
+ *
+ *   PTE_DIRTY || (PTE_WRITE && !PTE_RDONLY)
+ */
+void __check_safe_pte_update(struct mm_struct *mm, pte_t *ptep, pte_t pte)
+{
+	pte_t old_pte;
+
+	if (!IS_ENABLED(CONFIG_DEBUG_VM))
+		return;
+
+	old_pte = __ptep_get(ptep);
+
+	if (!pte_valid(old_pte) || !pte_valid(pte))
+		return;
+	if (mm != current->active_mm && atomic_read(&mm->mm_users) <= 1)
+		return;
+
+	/*
+	 * Check for potential race with hardware updates of the pte
+	 * (__ptep_set_access_flags safely changes valid ptes without going
+	 * through an invalid entry).
+	 */
+	VM_WARN_ONCE(!pte_young(pte),
+		     "%s: racy access flag clearing: 0x%016llx -> 0x%016llx",
+		     __func__, pte_val(old_pte), pte_val(pte));
+	VM_WARN_ONCE(pte_write(old_pte) && !pte_dirty(pte),
+		     "%s: racy dirty state clearing: 0x%016llx -> 0x%016llx",
+		     __func__, pte_val(old_pte), pte_val(pte));
+	VM_WARN_ONCE(!pgattr_change_is_safe(pte_val(old_pte), pte_val(pte)),
+		     "%s: unsafe attribute change: 0x%016llx -> 0x%016llx",
+		     __func__, pte_val(old_pte), pte_val(pte));
+}
 #endif
-- 
2.43.0