linux-kernel - [PATCH v2] arm64: mm: Drop redundant check in pmd_trans

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250508085251.204282-1-gshan@redhat.com>
Date: Thu,  8 May 2025 18:52:51 +1000
From: Gavin Shan <gshan@...hat.com>
To: linux-arm-kernel@...ts.infradead.org
Cc: linux-kernel@...r.kernel.org,
	catalin.marinas@....com,
	will@...nel.org,
	anshuman.khandual@....com,
	ryan.roberts@....com,
	dev.jain@....com,
	gshan@...hat.com,
	peterx@...hat.com,
	joey.gouly@....com,
	yangyicong@...ilicon.com,
	shan.gavin@...il.com
Subject: [PATCH v2] arm64: mm: Drop redundant check in pmd_trans_huge()

pmd_val(pmd) is redundant because a positive pmd_present(pmd) ensures
a positive pmd_val(pmd) according to their definitions like below.

  #define pmd_val(x)       ((x).pmd)
  #define pmd_present(pmd) pte_present(pmd_pte(pmd))
  #define pte_present(pte) (pte_valid(pte) || pte_present_invalid(pte))
  #define pte_valid(pte)   (!!(pte_val(pte) & PTE_VALID))
  #define pte_present_invalid(pte) \
          ((pte_val(pte) & (PTE_VALID | PTE_PRESENT_INVALID)) == PTE_PRESENT_INVALID)

pte_present() can't be positive unless either of the flag PTE_VALID or
PTE_PRESENT_INVALID is set. In this case, pmd_val(pmd) should be positive
either.

So lets drop the redundant check pmd_val(pmd) and no functional changes
intended.

Signed-off-by: Gavin Shan <gshan@...hat.com>
Reviewed-by: Dev Jain <dev.jain@....com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@....com>
---
v1: https://lore.kernel.org/linux-arm-kernel/4e5941f8-7e61-4a63-a669-bee1601093a6@arm.com/T/#u
v2: Improved commit log per Anshuman
---
 arch/arm64/include/asm/pgtable.h | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index d3b538be1500..2599b9b8666f 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -739,8 +739,7 @@ static inline int pmd_trans_huge(pmd_t pmd)
 	 * If pmd is present-invalid, pmd_table() won't detect it
 	 * as a table, so force the valid bit for the comparison.
 	 */
-	return pmd_val(pmd) && pmd_present(pmd) &&
-	       !pmd_table(__pmd(pmd_val(pmd) | PTE_VALID));
+	return pmd_present(pmd) && !pmd_table(__pmd(pmd_val(pmd) | PTE_VALID));
 }
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 
-- 
2.49.0