[PATCH 0/2] arm64/mm: Standardize printing for pgtable entries

[PATCH 0/2] arm64/mm: Standardize printing for pgtable entries

[Anshuman Khandual]

Standardize printing for pgtable entries using recently introduced generic
helper ptval_bytes_to_hex_str() in core MM which automatically enables 128
bits entries when added later.

But first move __check_safe_pte_update() outside <asm/pgtable.h> to avoid
a cyclic dependency while accessing these afore mentioned core MM helpers
defined in <linux/pgtable.h>. This replaces the original page table entry
print standardisation proposal which was earlier part of the D128 series.

https://lore.kernel.org/linux-mm/20260729122452.3797443-11-anshuman.khandual@arm.com/

This series applies on v7.3-rc1 but after the following.

https://lore.kernel.org/linux-mm/20260831054331.625505-1-anshuman.khandual@arm.com/

Cc: David Hildenbrand (Arm) <david@kernel.org>
Cc: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-mm@kvack.org

Anshuman Khandual (2):
  arm64/mm: Move __check_safe_pte_update()
  arm64/mm: Standardize printing for pgtable entries

 arch/arm64/include/asm/pgtable.h | 47 +-----------------------------
 arch/arm64/mm/fault.c            | 20 +++++++++----
 arch/arm64/mm/mmu.c              | 49 ++++++++++++++++++++++++++++++++
 3 files changed, 65 insertions(+), 51 deletions(-)

-- 
2.43.0

[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@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
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

[PATCH 2/2] arm64/mm: Standardize printing for pgtable entries

[Anshuman Khandual]

Standardize printing for pgtable entries using recently introduced generic
helper ptval_bytes_to_hex_str() in core MM which automatically enables 128
bits entries when added later.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
 arch/arm64/mm/fault.c | 20 +++++++++++++++-----
 arch/arm64/mm/mmu.c   | 16 ++++++++++------
 2 files changed, 25 insertions(+), 11 deletions(-)

diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 0b52557652be..c75bab3c2f4b 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -130,6 +130,11 @@ static inline unsigned long mm_to_pgd_phys(struct mm_struct *mm)
  */
 static void show_pte(unsigned long addr)
 {
+	char pgd_str[PTVAL_STR_MAX];
+	char p4d_str[PTVAL_STR_MAX];
+	char pud_str[PTVAL_STR_MAX];
+	char pmd_str[PTVAL_STR_MAX];
+	char pte_str[PTVAL_STR_MAX];
 	struct mm_struct *mm;
 	pgd_t *pgdp;
 	pgd_t pgd;
@@ -156,7 +161,8 @@ static void show_pte(unsigned long addr)
 		 vabits_actual, mm_to_pgd_phys(mm));
 	pgdp = pgd_offset(mm, addr);
 	pgd = READ_ONCE(*pgdp);
-	pr_alert("[%016lx] pgd=%016llx", addr, pgd_val(pgd));
+	ptval_to_str(pgd_str, pgd_val(pgd));
+	pr_alert("[%016lx] pgd=%s", addr, pgd_str);
 
 	do {
 		p4d_t *p4dp, p4d;
@@ -169,19 +175,22 @@ static void show_pte(unsigned long addr)
 
 		p4dp = p4d_offset(pgdp, addr);
 		p4d = READ_ONCE(*p4dp);
-		pr_cont(", p4d=%016llx", p4d_val(p4d));
+		ptval_to_str(p4d_str, p4d_val(p4d));
+		pr_cont(", p4d=%s", p4d_str);
 		if (p4d_none(p4d) || p4d_bad(p4d))
 			break;
 
 		pudp = pud_offset(p4dp, addr);
 		pud = READ_ONCE(*pudp);
-		pr_cont(", pud=%016llx", pud_val(pud));
+		ptval_to_str(pud_str, pud_val(pud));
+		pr_cont(", pud=%s", pud_str);
 		if (pud_none(pud) || pud_bad(pud))
 			break;
 
 		pmdp = pmd_offset(pudp, addr);
 		pmd = READ_ONCE(*pmdp);
-		pr_cont(", pmd=%016llx", pmd_val(pmd));
+		ptval_to_str(pmd_str, pmd_val(pmd));
+		pr_cont(", pmd=%s", pmd_str);
 		if (pmd_none(pmd) || pmd_bad(pmd))
 			break;
 
@@ -190,7 +199,8 @@ static void show_pte(unsigned long addr)
 			break;
 
 		pte = __ptep_get(ptep);
-		pr_cont(", pte=%016llx", pte_val(pte));
+		ptval_to_str(pte_str, pte_val(pte));
+		pr_cont(", pte=%s", pte_str);
 		pte_unmap(ptep);
 	} while(0);
 
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index e9c66d26bc0a..b5de4095d650 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -2410,6 +2410,8 @@ int arch_set_user_pkey_access(int pkey, unsigned long init_val)
  */
 void __check_safe_pte_update(struct mm_struct *mm, pte_t *ptep, pte_t pte)
 {
+	char pte_str_old[PTVAL_STR_MAX];
+	char pte_str[PTVAL_STR_MAX];
 	pte_t old_pte;
 
 	if (!IS_ENABLED(CONFIG_DEBUG_VM))
@@ -2427,14 +2429,16 @@ void __check_safe_pte_update(struct mm_struct *mm, pte_t *ptep, pte_t pte)
 	 * (__ptep_set_access_flags safely changes valid ptes without going
 	 * through an invalid entry).
 	 */
+	ptval_to_str(pte_str, pte_val(pte));
+	ptval_to_str(pte_str_old, pte_val(old_pte));
 	VM_WARN_ONCE(!pte_young(pte),
-		     "%s: racy access flag clearing: 0x%016llx -> 0x%016llx",
-		     __func__, pte_val(old_pte), pte_val(pte));
+		     "%s: racy access flag clearing: %s -> %s",
+		     __func__, pte_str_old, pte_str);
 	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));
+		     "%s: racy dirty state clearing: %s -> %s",
+		     __func__, pte_str_old, pte_str);
 	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));
+		     "%s: unsafe attribute change: %s -> %s",
+		     __func__, pte_str_old, pte_str);
 }
 #endif
-- 
2.43.0