From: Kevin Brodsky <kevin.brodsky@arm•com>
To: Ard Biesheuvel <ardb+git@google•com>,
linux-arm-kernel@lists•infradead.org
Cc: linux-kernel@vger•kernel.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>, Mike Rapoport <rppt@kernel•org>,
David Hildenbrand <david@kernel•org>,
Andrew Morton <akpm@linux-foundation•org>,
Jann Horn <jannh@google•com>,
linux-mm@kvack•org, linux-hardening@vger•kernel.org,
linuxppc-dev@lists•ozlabs.org, linux-sh@vger•kernel.org
Subject: Re: [PATCH v7 10/15] arm64: mm: Don't abuse memblock NOMAP to check for overlaps
Date: Mon, 1 Jun 2026 12:43:12 +0200 [thread overview]
Message-ID: <c0eb50f2-b0da-4d5e-9a20-09c2391cd3f9@arm.com> (raw)
In-Reply-To: <20260529150150.1670604-27-ardb+git@google.com>
On 29/05/2026 17:02, Ard Biesheuvel wrote:
> From: Ard Biesheuvel <ardb@kernel•org>
>
> Now that the linear region mapping routines respect existing table
> mappings and contiguous block and page mappings, it is no longer needed
> to fiddle with the memblock tables to set and clear the NOMAP attribute
> in order to omit text and rodata when creating the linear map.
>
> Instead, map the kernel text and rodata alias first with the desired
> initial attributes and granularity, so that the loop iterating over the
> memblocks will not remap it in a manner that prevents it from being
> remapped with updated attributes later.
>
> Signed-off-by: Ard Biesheuvel <ardb@kernel•org>
Reviewed-by: Kevin Brodsky <kevin.brodsky@arm•com>
> ---
> arch/arm64/mm/mmu.c | 26 ++++++++------------
> 1 file changed, 10 insertions(+), 16 deletions(-)
>
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index 971996e46fd1..dcfca5667e5c 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -1164,12 +1164,17 @@ static void __init map_mem(void)
> flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
>
> /*
> - * Take care not to create a writable alias for the
> - * read-only text and rodata sections of the kernel image.
> - * So temporarily mark them as NOMAP to skip mappings in
> - * the following for-loop
> + * Map the linear alias of the [_text, __init_begin) interval first
> + * so that its write permissions can be removed later without the need
> + * to split any block mappings created by the loop below.
> + *
> + * Write permissions are needed for alternatives patching, and will be
> + * removed later by mark_linear_text_alias_ro() above. This makes the
> + * contents of the region accessible to subsystems such as hibernate,
> + * but protects it from inadvertent modification or execution.
> */
> - memblock_mark_nomap(kernel_start, kernel_end - kernel_start);
> + __map_memblock(kernel_start, kernel_end, pgprot_tagged(PAGE_KERNEL),
> + flags);
>
> /* map all the memory banks */
> for_each_mem_range(i, &start, &end) {
> @@ -1181,17 +1186,6 @@ static void __init map_mem(void)
> __map_memblock(start, end, pgprot_tagged(PAGE_KERNEL),
> flags);
> }
> -
> - /*
> - * Map the linear alias of the [_text, __init_begin) interval
> - * as non-executable now, and remove the write permission in
> - * mark_linear_text_alias_ro() below (which will be called after
> - * alternative patching has completed). This makes the contents
> - * of the region accessible to subsystems such as hibernate,
> - * but protects it from inadvertent modification or execution.
> - */
> - __map_memblock(kernel_start, kernel_end, PAGE_KERNEL, 0);
> - memblock_clear_nomap(kernel_start, kernel_end - kernel_start);
> }
>
> void mark_rodata_ro(void)
next prev parent reply other threads:[~2026-06-01 10:43 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-29 15:01 [PATCH v7 00/15] arm64: Unmap linear alias of kernel data/bss Ard Biesheuvel
2026-05-29 15:01 ` [PATCH v7 01/15] arm64: mm: Remove bogus stop condition from map_mem() loop Ard Biesheuvel
2026-05-29 15:01 ` [PATCH v7 02/15] arm64: mm: Drop redundant pgd_t* argument from map_mem() Ard Biesheuvel
2026-05-29 15:01 ` [PATCH v7 03/15] arm64: mm: Check for pud_/pmd_set_huge() failures on kernel mappings Ard Biesheuvel
2026-05-29 15:01 ` [PATCH v7 04/15] arm64: mm: Preserve existing table mappings when mapping DRAM Ard Biesheuvel
2026-05-29 15:01 ` [PATCH v7 05/15] arm64: mm: Preserve non-contiguous descriptors " Ard Biesheuvel
2026-05-29 15:01 ` [PATCH v7 06/15] arm64: mm: Permit contiguous descriptors to be manipulated Ard Biesheuvel
2026-05-29 15:01 ` [PATCH v7 07/15] arm64: kfence: Avoid NOMAP tricks when mapping the early pool Ard Biesheuvel
2026-06-01 10:42 ` Kevin Brodsky
2026-05-29 15:01 ` [PATCH v7 08/15] arm64: mm: Permit contiguous attribute for preliminary mappings Ard Biesheuvel
2026-05-29 15:02 ` [PATCH v7 09/15] arm64: Move fixmap and kasan page tables to end of kernel image Ard Biesheuvel
2026-05-29 15:02 ` [PATCH v7 10/15] arm64: mm: Don't abuse memblock NOMAP to check for overlaps Ard Biesheuvel
2026-06-01 10:43 ` Kevin Brodsky [this message]
2026-05-29 15:02 ` [PATCH v7 11/15] powerpc/code-patching: Avoid r/w mapping of the zero page Ard Biesheuvel
2026-06-03 18:03 ` Mukesh Kumar Chaurasiya
2026-06-04 7:43 ` Christophe Leroy (CS GROUP)
2026-05-29 15:02 ` [PATCH v7 12/15] sh: Drop cache flush of the zero page at boot Ard Biesheuvel
2026-05-30 16:19 ` Mike Rapoport
2026-06-01 8:11 ` Geert Uytterhoeven
2026-05-29 15:02 ` [PATCH v7 13/15] mm: Make empty_zero_page[] const Ard Biesheuvel
2026-05-29 15:02 ` [PATCH v7 14/15] arm64: mm: Map the kernel data/bss read-only in the linear map Ard Biesheuvel
2026-05-29 15:02 ` [PATCH v7 15/15] arm64: mm: Unmap kernel data/bss entirely from " Ard Biesheuvel
2026-06-01 10:43 ` Kevin Brodsky
2026-06-02 20:34 ` [PATCH v7 00/15] arm64: Unmap linear alias of kernel data/bss Will Deacon
2026-06-03 8:57 ` Ard Biesheuvel
2026-06-03 11:22 ` Will Deacon
2026-06-03 11:24 ` Ard Biesheuvel
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