[PATCH v7 04/15] arm64: mm: Preserve existing table mappings when mapping DRAM
From: Ard Biesheuvel <hidden>
Date: 2026-05-29 15:02:52
Also in:
linux-arm-kernel, linux-hardening, linux-mm, linux-sh, lkml
Subsystem:
arm64 port (aarch64 architecture), the rest · Maintainers:
Catalin Marinas, Will Deacon, Linus Torvalds
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. Reviewed-by: Ryan Roberts <ryan.roberts@arm.com> Signed-off-by: Ard Biesheuvel <ardb@kernel.org> --- 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 b2ba5b35c35f..5c827fa3cd38 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c@@ -256,7 +256,8 @@ 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)) { WARN_ON(!pmd_set_huge(pmdp, phys, prot)); /*
@@ -379,7 +380,8 @@ 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)) { WARN_ON(!pud_set_huge(pudp, phys, prot)); /*
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2.54.0.823.g6e5bcc1fc9-goog