linux-kernel - Re: [PATCH v2 12/14] x86: Minimal SLAB alignment

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Message-ID: <CA+fCnZdidM3Sj_ftw6pmtzw-tjy0LLD+2aqtzSewQTOUXMs2hw@mail.gmail.com>
Date: Thu, 20 Feb 2025 00:30:48 +0100
From: Andrey Konovalov <andreyknvl@...il.com>
To: Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>
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Subject: Re: [PATCH v2 12/14] x86: Minimal SLAB alignment

On Tue, Feb 18, 2025 at 9:20 AM Maciej Wieczor-Retman
<maciej.wieczor-retman@...el.com> wrote:
>
> Adjust x86 minimal SLAB alignment to match KASAN granularity size. In
> tag-based mode the size changes to 16 bytes so the value needs to be 4.

This 4 should be 16.

>
> Signed-off-by: Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>
> ---
>  arch/x86/include/asm/kasan.h | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/arch/x86/include/asm/kasan.h b/arch/x86/include/asm/kasan.h
> index 8829337a75fa..a75f0748a4b6 100644
> --- a/arch/x86/include/asm/kasan.h
> +++ b/arch/x86/include/asm/kasan.h
> @@ -36,6 +36,8 @@
>
>  #ifdef CONFIG_KASAN_SW_TAGS
>
> +#define ARCH_SLAB_MINALIGN (1ULL << KASAN_SHADOW_SCALE_SHIFT)

I believe ARCH_SLAB_MINALIGN needs to be defined in
include/asm/cache.h: at least other architectures have it there.


> +
>  #define __tag_shifted(tag)             FIELD_PREP(GENMASK_ULL(60, 57), tag)
>  #define __tag_reset(addr)              (sign_extend64((u64)(addr), 56))
>  #define __tag_get(addr)                        ((u8)FIELD_GET(GENMASK_ULL(60, 57), (u64)addr))
> --
> 2.47.1
>