linux-kernel - [PATCH] arm64/mm: Avoid direct referencing page table enties in map

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Message-Id: <20240725091052.314750-1-anshuman.khandual@arm.com>
Date: Thu, 25 Jul 2024 14:40:52 +0530
From: Anshuman Khandual <anshuman.khandual@....com>
To: linux-arm-kernel@...ts.infradead.org
Cc: Anshuman Khandual <anshuman.khandual@....com>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	Ryan Roberts <ryan.roberts@....com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH] arm64/mm: Avoid direct referencing page table enties in map_range()

Like else where in arm64 platform, use WRITE_ONCE() in map_range() while
creating page table entries. This avoids referencing page table entries
directly.

Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Will Deacon <will@...nel.org>
Cc: Ryan Roberts <ryan.roberts@....com>
Cc: linux-arm-kernel@...ts.infradead.org
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
---
 arch/arm64/kernel/pi/map_range.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kernel/pi/map_range.c b/arch/arm64/kernel/pi/map_range.c
index 5410b2cac590..b93b70cdfb62 100644
--- a/arch/arm64/kernel/pi/map_range.c
+++ b/arch/arm64/kernel/pi/map_range.c
@@ -56,8 +56,8 @@ void __init map_range(u64 *pte, u64 start, u64 end, u64 pa, pgprot_t prot,
 			 * table mapping if necessary and recurse.
 			 */
 			if (pte_none(*tbl)) {
-				*tbl = __pte(__phys_to_pte_val(*pte) |
-					     PMD_TYPE_TABLE | PMD_TABLE_UXN);
+				WRITE_ONCE(*tbl, __pte(__phys_to_pte_val(*pte) |
+					   PMD_TYPE_TABLE | PMD_TABLE_UXN));
 				*pte += PTRS_PER_PTE * sizeof(pte_t);
 			}
 			map_range(pte, start, next, pa, prot, level + 1,
@@ -79,7 +79,7 @@ void __init map_range(u64 *pte, u64 start, u64 end, u64 pa, pgprot_t prot,
 				protval &= ~PTE_CONT;
 
 			/* Put down a block or page mapping */
-			*tbl = __pte(__phys_to_pte_val(pa) | protval);
+			WRITE_ONCE(*tbl, __pte(__phys_to_pte_val(pa) | protval));
 		}
 		pa += next - start;
 		start = next;
-- 
2.30.2