Re: [PATCH v2 04/10] arm64: mm: Preserve existing table mappings when mapping DRAM
From: Ryan Roberts <ryan.roberts@arm.com>
Date: 2026-01-27 09:58:31
Also in:
linux-hardening, lkml
On 26/01/2026 09:26, Ard Biesheuvel wrote:
From: Ard Biesheuvel <ardb@kernel.org> Instead of blindly overwriting an existing table entry when mapping DRAM regions, take care not to replace a pre-existing table entry with a block entry. This permits the logic of mapping the kernel's linear alias to be simplified in a subsequent patch. Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
quoted hunk ↗ jump to hunk
--- arch/arm64/mm/mmu.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index 9d39de3cfe67..28cc3cda042c 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c@@ -262,7 +262,8 @@ static int init_pmd(pmd_t *pmdp, unsigned long addr, unsigned long end, /* try section mapping first */ if (((addr | next | phys) & ~PMD_MASK) == 0 && - (flags & NO_BLOCK_MAPPINGS) == 0) { + (flags & NO_BLOCK_MAPPINGS) == 0 && + !pmd_table(old_pmd)) { pmd_set_huge(pmdp, phys, prot); /*@@ -385,7 +386,8 @@ static int alloc_init_pud(p4d_t *p4dp, unsigned long addr, unsigned long end, */ if (pud_sect_supported() && ((addr | next | phys) & ~PUD_MASK) == 0 && - (flags & NO_BLOCK_MAPPINGS) == 0) { + (flags & NO_BLOCK_MAPPINGS) == 0 && + !pud_table(old_pud)) { pud_set_huge(pudp, phys, prot); /*