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 01/13] arm64: Move the zero page to rodata
Date: Fri, 20 Mar 2026 15:59:36 +0100 [thread overview]
Message-ID: <20260320145934.2349881-16-ardb+git@google.com> (raw)
In-Reply-To: <20260320145934.2349881-15-ardb+git@google.com>
From: Ard Biesheuvel <ardb@kernel.org>
The zero page should contain only zero bytes, and so mapping it
read-write is unnecessary. Combine it with reserved_pg_dir, which lives
in the read-only region of the kernel, and already serves a similar
purpose.
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
arch/arm64/kernel/vmlinux.lds.S | 1 +
arch/arm64/mm/mmu.c | 3 +--
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
index 2964aad0362e..2d021a576e50 100644
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -229,6 +229,7 @@ SECTIONS
#endif
reserved_pg_dir = .;
+ empty_zero_page = .;
. += PAGE_SIZE;
swapper_pg_dir = .;
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index a6a00accf4f9..795743913ce5 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -66,9 +66,8 @@ long __section(".mmuoff.data.write") __early_cpu_boot_status;
/*
* Empty_zero_page is a special page that is used for zero-initialized data
- * and COW.
+ * and COW. Defined in the linker script.
*/
-unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)] __page_aligned_bss;
EXPORT_SYMBOL(empty_zero_page);
static DEFINE_SPINLOCK(swapper_pgdir_lock);
--
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 ` Ard Biesheuvel [this message]
2026-03-20 14:59 ` [PATCH v3 02/13] arm64: mm: Preserve existing table mappings when mapping DRAM Ard Biesheuvel
2026-03-20 14:59 ` [PATCH v3 03/13] arm64: mm: Preserve non-contiguous descriptors " 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
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