Re: [PATCH v9 22/44] kasan: rename SHADOW layout macros to META

[Alexander Potapenko <glider@google.com>]

On Tue, Nov 10, 2020 at 11:12 PM Andrey Konovalov <andreyknvl@google.com> wrote:
>
> This is a preparatory commit for the upcoming addition of a new hardware
> tag-based (MTE-based) KASAN mode.
>
> Hardware tag-based KASAN won't be using shadow memory, but will reuse
> these macros. Rename "SHADOW" to implementation-neutral "META".
>
> No functional changes.
>
> 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>

> ---
> Change-Id: Id2d836bf43b401bce1221cc06e745185f17b1cc
> ---
>  mm/kasan/report.c | 30 +++++++++++++++---------------
>  1 file changed, 15 insertions(+), 15 deletions(-)
>
> diff --git a/mm/kasan/report.c b/mm/kasan/report.c
> index 594bad2a3a5e..8c588588c88f 100644
> --- a/mm/kasan/report.c
> +++ b/mm/kasan/report.c
> @@ -33,11 +33,11 @@
>  #include "kasan.h"
>  #include "../slab.h"
>
> -/* Shadow layout customization. */
> -#define SHADOW_BYTES_PER_BLOCK 1
> -#define SHADOW_BLOCKS_PER_ROW 16
> -#define SHADOW_BYTES_PER_ROW (SHADOW_BLOCKS_PER_ROW * SHADOW_BYTES_PER_BLOCK)
> -#define SHADOW_ROWS_AROUND_ADDR 2
> +/* Metadata layout customization. */
> +#define META_BYTES_PER_BLOCK 1
> +#define META_BLOCKS_PER_ROW 16
> +#define META_BYTES_PER_ROW (META_BLOCKS_PER_ROW * META_BYTES_PER_BLOCK)
> +#define META_ROWS_AROUND_ADDR 2
>
>  static unsigned long kasan_flags;
>
> @@ -240,7 +240,7 @@ static void print_address_description(void *addr, u8 tag)
>
>  static bool row_is_guilty(const void *row, const void *guilty)
>  {
> -       return (row <= guilty) && (guilty < row + SHADOW_BYTES_PER_ROW);
> +       return (row <= guilty) && (guilty < row + META_BYTES_PER_ROW);
>  }
>
>  static int shadow_pointer_offset(const void *row, const void *shadow)
> @@ -249,7 +249,7 @@ static int shadow_pointer_offset(const void *row, const void *shadow)
>          *    3 + (BITS_PER_LONG/8)*2 chars.
>          */
>         return 3 + (BITS_PER_LONG/8)*2 + (shadow - row)*2 +
> -               (shadow - row) / SHADOW_BYTES_PER_BLOCK + 1;
> +               (shadow - row) / META_BYTES_PER_BLOCK + 1;
>  }
>
>  static void print_memory_metadata(const void *addr)
> @@ -259,15 +259,15 @@ static void print_memory_metadata(const void *addr)
>         const void *shadow_row;
>
>         shadow_row = (void *)round_down((unsigned long)shadow,
> -                                       SHADOW_BYTES_PER_ROW)
> -               - SHADOW_ROWS_AROUND_ADDR * SHADOW_BYTES_PER_ROW;
> +                                       META_BYTES_PER_ROW)
> +               - META_ROWS_AROUND_ADDR * META_BYTES_PER_ROW;
>
>         pr_err("Memory state around the buggy address:\n");
>
> -       for (i = -SHADOW_ROWS_AROUND_ADDR; i <= SHADOW_ROWS_AROUND_ADDR; i++) {
> +       for (i = -META_ROWS_AROUND_ADDR; i <= META_ROWS_AROUND_ADDR; i++) {
>                 const void *kaddr = kasan_shadow_to_mem(shadow_row);
>                 char buffer[4 + (BITS_PER_LONG/8)*2];
> -               char shadow_buf[SHADOW_BYTES_PER_ROW];
> +               char shadow_buf[META_BYTES_PER_ROW];
>
>                 snprintf(buffer, sizeof(buffer),
>                         (i == 0) ? ">%px: " : " %px: ", kaddr);
> @@ -276,17 +276,17 @@ static void print_memory_metadata(const void *addr)
>                  * function, because generic functions may try to
>                  * access kasan mapping for the passed address.
>                  */
> -               memcpy(shadow_buf, shadow_row, SHADOW_BYTES_PER_ROW);
> +               memcpy(shadow_buf, shadow_row, META_BYTES_PER_ROW);
>                 print_hex_dump(KERN_ERR, buffer,
> -                       DUMP_PREFIX_NONE, SHADOW_BYTES_PER_ROW, 1,
> -                       shadow_buf, SHADOW_BYTES_PER_ROW, 0);
> +                       DUMP_PREFIX_NONE, META_BYTES_PER_ROW, 1,
> +                       shadow_buf, META_BYTES_PER_ROW, 0);
>
>                 if (row_is_guilty(shadow_row, shadow))
>                         pr_err("%*c\n",
>                                 shadow_pointer_offset(shadow_row, shadow),
>                                 '^');
>
> -               shadow_row += SHADOW_BYTES_PER_ROW;
> +               shadow_row += META_BYTES_PER_ROW;
>         }
>  }
>
> --
> 2.29.2.222.g5d2a92d10f8-goog
>


-- 
Alexander Potapenko
Software Engineer

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