Re: [patch 21/78] kasan: split out shadow.c from common.c

[Marco Elver <elver@google.com>]

On Fri, Dec 18, 2020 at 02:02PM -0800, Andrew Morton wrote:
> From: Andrey Konovalov <andreyknvl@google.com>
> Subject: kasan: split out shadow.c from common.c
> 
> This is a preparatory commit for the upcoming addition of a new hardware
> tag-based (MTE-based) KASAN mode.
> 
> The new mode won't be using shadow memory.  Move all shadow-related code
> to shadow.c, which is only enabled for software KASAN modes that use
> shadow memory.
> 
> No functional changes for software modes.
> 
> Link: https://lkml.kernel.org/r/17d95cfa7d5cf9c4fcd9bf415f2a8dea911668df.1606161801.git.andreyknvl@google.com
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
> Reviewed-by: Marco Elver <elver@google.com>
> Reviewed-by: Alexander Potapenko <glider@google.com>
> Tested-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
> Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
> Cc: Branislav Rankov <Branislav.Rankov@arm.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Dmitry Vyukov <dvyukov@google.com>
> Cc: Evgenii Stepanov <eugenis@google.com>
> Cc: Kevin Brodsky <kevin.brodsky@arm.com>
> Cc: Vasily Gorbik <gor@linux.ibm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> ---
> 
>  mm/kasan/Makefile |    6 
>  mm/kasan/common.c |  486 -----------------------------------------
>  mm/kasan/shadow.c |  518 ++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 523 insertions(+), 487 deletions(-)
> 
> --- a/mm/kasan/common.c~kasan-split-out-shadowc-from-commonc
> +++ a/mm/kasan/common.c
> @@ -1,6 +1,6 @@
>  // SPDX-License-Identifier: GPL-2.0
>  /*
> - * This file contains common generic and tag-based KASAN code.
> + * This file contains common KASAN code.
>   *
>   * Copyright (c) 2014 Samsung Electronics Co., Ltd.
>   * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
> @@ -13,7 +13,6 @@
>  #include <linux/init.h>
>  #include <linux/kasan.h>
>  #include <linux/kernel.h>
> -#include <linux/kmemleak.h>
>  #include <linux/linkage.h>
>  #include <linux/memblock.h>
>  #include <linux/memory.h>
> @@ -26,12 +25,8 @@
>  #include <linux/stacktrace.h>
>  #include <linux/string.h>
>  #include <linux/types.h>
> -#include <linux/vmalloc.h>
>  #include <linux/bug.h>
>  
> -#include <asm/cacheflush.h>
> -#include <asm/tlbflush.h>
> -
>  #include "kasan.h"
>  #include "../slab.h"
>  
[...]
> -/*
> - * Poisons the shadow memory for 'size' bytes starting from 'addr'.
> - * Memory addresses should be aligned to KASAN_GRANULE_SIZE.
> - */
> -void poison_range(const void *address, size_t size, u8 value)
> -{
> -	void *shadow_start, *shadow_end;
> -
> -	/*
> -	 * Perform shadow offset calculation based on untagged address, as
> -	 * some of the callers (e.g. kasan_poison_object_data) pass tagged
> -	 * addresses to this function.
> -	 */
> -	address = reset_tag(address);
> -

The moved lines do not mention kfence...
(The same commit in -next does.)

> -	shadow_start = kasan_mem_to_shadow(address);
> -	shadow_end = kasan_mem_to_shadow(address + size);
> -
> -	__memset(shadow_start, value, shadow_end - shadow_start);
> -}
[...]
> --- /dev/null
> +++ a/mm/kasan/shadow.c
> @@ -0,0 +1,518 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * This file contains KASAN runtime code that manages shadow memory for
> + * generic and software tag-based KASAN modes.
> + *
> + * Copyright (c) 2014 Samsung Electronics Co., Ltd.
> + * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
> + *
> + * Some code borrowed from https://github.com/xairy/kasan-prototype by
> + *        Andrey Konovalov <andreyknvl@gmail.com>
> + */
> +
> +#include <linux/init.h>
> +#include <linux/kasan.h>
> +#include <linux/kernel.h>
> +#include <linux/kfence.h>

This is the first time kfence is mentioned. Is this correct?

Is my assumption correct that the kasan changes and kfence changes are
to be swapped?

Thanks,
-- Marco