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From: Ada Couprie Diaz <ada.coupriediaz@arm.com>
To: Maciej Wieczor-Retman <maciej.wieczor-retman@intel.com>
Cc: nathan@kernel.org, arnd@arndb.de, broonie@kernel.org,
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	Ada Couprie Diaz <ada.coupriediaz@arm.com>
Subject: Re: [PATCH v4 02/18] kasan: sw_tags: Support tag widths less than 8 bits
Date: Wed, 13 Aug 2025 15:48:32 +0100	[thread overview]
Message-ID: <cae90aa0-9fa6-4066-bbc0-ba391f908fb2@arm.com> (raw)
In-Reply-To: <780347f3897ea97e90968de028c9dd02f466204e.1755004923.git.maciej.wieczor-retman@intel.com>

Hi,

On 12/08/2025 14:23, Maciej Wieczor-Retman wrote:
> From: Samuel Holland <samuel.holland@sifive.com>
>
> Allow architectures to override KASAN_TAG_KERNEL in asm/kasan.h. This
> is needed on RISC-V, which supports 57-bit virtual addresses and 7-bit
> pointer tags. For consistency, move the arm64 MTE definition of
> KASAN_TAG_MIN to asm/kasan.h, since it is also architecture-dependent;
> RISC-V's equivalent extension is expected to support 7-bit hardware
> memory tags.
>
> Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
> Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
> Signed-off-by: Maciej Wieczor-Retman <maciej.wieczor-retman@intel.com>
> ---
>   arch/arm64/include/asm/kasan.h   |  6 ++++--
>   arch/arm64/include/asm/uaccess.h |  1 +
>   include/linux/kasan-tags.h       | 13 ++++++++-----
>   3 files changed, 13 insertions(+), 7 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kasan.h b/arch/arm64/include/asm/kasan.h
> index e1b57c13f8a4..4ab419df8b93 100644
> --- a/arch/arm64/include/asm/kasan.h
> +++ b/arch/arm64/include/asm/kasan.h
> @@ -6,8 +6,10 @@
>   
>   #include <linux/linkage.h>
>   #include <asm/memory.h>
> -#include <asm/mte-kasan.h>
> -#include <asm/pgtable-types.h>
> +
> +#ifdef CONFIG_KASAN_HW_TAGS
> +#define KASAN_TAG_MIN			0xF0 /* minimum value for random tags */
> +#endif
Building CONFIG_KASAN_HW_TAGS with -Werror on arm64 fails here
due to a warning about KASAN_TAG_MIN being redefined.

On my side the error got triggered when compiling
arch/arm64/kernel/asm-offsets.c due to the ordering of some includes :
from <asm/processor.h>, <linux/kasan-tags.h> ends up being included
(by <asm/cpufeatures.h> including <asm/sysreg.h>) before <asm/kasan.h>.
(Build trace at the end for reference)

Adding `#undef KASAN_TAG_MIN` before redefining the arch version
allows building CONFIG_KASAN_HW_TAGS on arm64 without
further issues, but I don't know if this is most appropriate fix.Thanks, 
Ada ---

   CC      arch/arm64/kernel/asm-offsets.s
In file included from ./arch/arm64/include/asm/processor.h:42,
                  from ./include/asm-generic/qrwlock.h:18,
                  from ./arch/arm64/include/generated/asm/qrwlock.h:1,
                  from ./arch/arm64/include/asm/spinlock.h:9,
                  from ./include/linux/spinlock.h:95,
                  from ./include/linux/mmzone.h:8,
                  from ./include/linux/gfp.h:7,
                  from ./include/linux/slab.h:16,
                  from ./include/linux/resource_ext.h:11,
                  from ./include/linux/acpi.h:13,
                  from ./include/acpi/apei.h:9,
                  from ./include/acpi/ghes.h:5,
                  from ./include/linux/arm_sdei.h:8,
                  from ./arch/arm64/kernel/asm-offsets.c:10:
./arch/arm64/include/asm/kasan.h:11: error: "KASAN_TAG_MIN" redefined [-Werror]
    11 | #define KASAN_TAG_MIN                   0xF0 /* minimum value for random tags */
       |
In file included from ./arch/arm64/include/asm/sysreg.h:14,
                  from ./arch/arm64/include/asm/cputype.h:250,
                  from ./arch/arm64/include/asm/cache.h:43,
                  from ./include/vdso/cache.h:5,
                  from ./include/linux/cache.h:6,
                  from ./include/linux/slab.h:15:
./include/linux/kasan-tags.h:23: note: this is the location of the previous definition
    23 | #define KASAN_TAG_MIN           0x00 /* minimum value for random tags */
       |


  reply	other threads:[~2025-08-13 14:48 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-08-12 13:23 [PATCH v4 00/18] kasan: x86: arm64: KASAN tag-based mode for x86 Maciej Wieczor-Retman
2025-08-12 13:23 ` [PATCH v4 01/18] kasan: sw_tags: Use arithmetic shift for shadow computation Maciej Wieczor-Retman
2025-08-12 13:23 ` [PATCH v4 02/18] kasan: sw_tags: Support tag widths less than 8 bits Maciej Wieczor-Retman
2025-08-13 14:48   ` Ada Couprie Diaz [this message]
2025-08-18  4:24     ` Maciej Wieczor-Retman
2025-08-12 13:23 ` [PATCH v4 03/18] kasan: Fix inline mode for x86 tag-based mode Maciej Wieczor-Retman
2025-08-12 13:23 ` [PATCH v4 04/18] x86: Add arch specific kasan functions Maciej Wieczor-Retman
2025-08-12 13:23 ` [PATCH v4 05/18] kasan: arm64: x86: Make special tags arch specific Maciej Wieczor-Retman
2025-08-12 13:23 ` [PATCH v4 06/18] x86: Reset tag for virtual to physical address conversions Maciej Wieczor-Retman
2025-08-14  7:15   ` Mike Rapoport
2025-08-18  5:29     ` Maciej Wieczor-Retman
2025-08-12 13:23 ` [PATCH v4 07/18] mm: x86: Untag addresses in EXECMEM_ROX related pointer arithmetic Maciej Wieczor-Retman
2025-08-14  7:26   ` Mike Rapoport
2025-08-18  5:47     ` Maciej Wieczor-Retman
2025-08-12 13:23 ` [PATCH v4 08/18] x86: Physical address comparisons in fill_p*d/pte Maciej Wieczor-Retman
2025-08-12 13:23 ` [PATCH v4 09/18] x86: KASAN raw shadow memory PTE init Maciej Wieczor-Retman
2025-08-12 13:23 ` [PATCH v4 10/18] x86: LAM compatible non-canonical definition Maciej Wieczor-Retman
2025-08-12 13:23 ` [PATCH v4 11/18] x86: LAM initialization Maciej Wieczor-Retman
2025-08-12 13:23 ` [PATCH v4 12/18] x86: Minimal SLAB alignment Maciej Wieczor-Retman
2025-08-12 13:23 ` [PATCH v4 13/18] kasan: arm64: x86: Handle int3 for inline KASAN reports Maciej Wieczor-Retman
2025-08-13 14:49   ` Ada Couprie Diaz
2025-08-18  5:57     ` Maciej Wieczor-Retman
2025-08-13 15:17   ` Peter Zijlstra
2025-08-18  6:26     ` Maciej Wieczor-Retman
2025-09-08 15:40       ` Peter Zijlstra
2025-09-09  8:47         ` Maciej Wieczor-Retman
2025-08-12 13:23 ` [PATCH v4 14/18] kasan: x86: Apply multishot to the inline report handler Maciej Wieczor-Retman
2025-08-12 13:23 ` [PATCH v4 15/18] kasan: x86: Logical bit shift for kasan_mem_to_shadow Maciej Wieczor-Retman
2025-08-12 13:23 ` [PATCH v4 16/18] mm: Unpoison pcpu chunks with base address tag Maciej Wieczor-Retman
2025-08-12 13:23 ` [PATCH v4 17/18] mm: Unpoison vms[area] addresses with a common tag Maciej Wieczor-Retman
2025-08-12 13:23 ` [PATCH v4 18/18] x86: Make software tag-based kasan available Maciej Wieczor-Retman
2025-08-13  8:16 ` [PATCH v4 00/18] kasan: x86: arm64: KASAN tag-based mode for x86 Kiryl Shutsemau
2025-08-13 10:39   ` Maciej Wieczor-Retman
2025-08-13 11:05     ` Kiryl Shutsemau
2025-08-13 11:44       ` Maciej Wieczor-Retman
2025-08-21 12:30 ` Ada Couprie Diaz
2025-08-22  7:36   ` Maciej Wieczor-Retman

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