From: Ard Biesheuvel <ardb+git@google.com>
To: linux-kernel@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org, will@kernel.org,
catalin.marinas@arm.com, mark.rutland@arm.com,
Ard Biesheuvel <ardb@kernel.org>,
Ryan Roberts <ryan.roberts@arm.com>,
Anshuman Khandual <anshuman.khandual@arm.com>,
Liz Prucka <lizprucka@google.com>,
Seth Jenkins <sethjenkins@google.com>,
Kees Cook <kees@kernel.org>,
linux-hardening@vger.kernel.org
Subject: [PATCH v3 02/13] arm64: mm: Preserve existing table mappings when mapping DRAM
Date: Fri, 20 Mar 2026 15:59:37 +0100 [thread overview]
Message-ID: <20260320145934.2349881-17-ardb+git@google.com> (raw)
In-Reply-To: <20260320145934.2349881-15-ardb+git@google.com>
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 795743913ce5..9927b55022d8 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);
/*
--
2.53.0.959.g497ff81fa9-goog
next prev parent reply other threads:[~2026-03-20 15:00 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-20 14:59 [PATCH v3 00/13] arm64: Unmap linear alias of kernel data/bss Ard Biesheuvel
2026-03-20 14:59 ` [PATCH v3 01/13] arm64: Move the zero page to rodata Ard Biesheuvel
2026-03-20 14:59 ` Ard Biesheuvel [this message]
2026-03-20 14:59 ` [PATCH v3 03/13] arm64: mm: Preserve non-contiguous descriptors when mapping DRAM Ard Biesheuvel
2026-03-20 14:59 ` [PATCH v3 04/13] arm64: mm: Remove bogus stop condition from map_mem() loop Ard Biesheuvel
2026-03-20 14:59 ` [PATCH v3 05/13] arm64: mm: Drop redundant pgd_t* argument from map_mem() Ard Biesheuvel
2026-03-20 14:59 ` [PATCH v3 06/13] arm64: mm: Permit contiguous descriptors to be rewritten Ard Biesheuvel
2026-03-20 14:59 ` [PATCH v3 07/13] arm64: mm: Use hierarchical XN mapping for the fixmap Ard Biesheuvel
2026-03-20 14:59 ` [PATCH v3 08/13] arm64: kfence: Avoid NOMAP tricks when mapping the early pool Ard Biesheuvel
2026-03-20 14:59 ` [PATCH v3 09/13] arm64: mm: Permit contiguous attribute for preliminary mappings Ard Biesheuvel
2026-03-20 14:59 ` [PATCH v3 10/13] arm64: Move fixmap page tables to end of kernel image Ard Biesheuvel
2026-03-20 14:59 ` [PATCH v3 11/13] arm64: mm: Don't abuse memblock NOMAP to check for overlaps Ard Biesheuvel
2026-03-20 14:59 ` [PATCH v3 12/13] arm64: mm: Map the kernel data/bss read-only in the linear map Ard Biesheuvel
2026-03-20 14:59 ` [PATCH v3 13/13] arm64: mm: Unmap kernel data/bss entirely from " Ard Biesheuvel
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20260320145934.2349881-17-ardb+git@google.com \
--to=ardb+git@google.com \
--cc=anshuman.khandual@arm.com \
--cc=ardb@kernel.org \
--cc=catalin.marinas@arm.com \
--cc=kees@kernel.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-hardening@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=lizprucka@google.com \
--cc=mark.rutland@arm.com \
--cc=ryan.roberts@arm.com \
--cc=sethjenkins@google.com \
--cc=will@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox