On Tue, Nov 10, 2020 at 11:11 PM Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote:
>
> Define KASAN_GRANULE_PAGE as (KASAN_GRANULE_SIZE << PAGE_SHIFT), which is
> the same as (KASAN_GRANULE_SIZE * PAGE_SIZE), and use it across KASAN code
> to simplify it.
What's the physical sense behind KASAN_GRANULE_PAGE? Is it something
more than just a product of two constants?
The name suggests it might be something page-sized, but in reality it is not.
>
> Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@xxxxxxx>
> Reviewed-by: Marco Elver <elver@xxxxxxxxxx>
> ---
> Change-Id: I0b627b24187d06c8b9bb2f1d04d94b3d06945e73
> ---
> mm/kasan/init.c | 10 ++++------
> mm/kasan/kasan.h | 1 +
> mm/kasan/shadow.c | 16 +++++++---------
> 3 files changed, 12 insertions(+), 15 deletions(-)
>
> diff --git a/mm/kasan/init.c b/mm/kasan/init.c
> index 1a71eaa8c5f9..26b2663b3a42 100644
> --- a/mm/kasan/init.c
> +++ b/mm/kasan/init.c
> @@ -441,9 +441,8 @@ void kasan_remove_zero_shadow(void *start, unsigned long size)
> addr = (unsigned long)kasan_mem_to_shadow(start);
> end = addr + (size >> KASAN_SHADOW_SCALE_SHIFT);
>
> - if (WARN_ON((unsigned long)start %
> - (KASAN_GRANULE_SIZE * PAGE_SIZE)) ||
> - WARN_ON(size % (KASAN_GRANULE_SIZE * PAGE_SIZE)))
> + if (WARN_ON((unsigned long)start % KASAN_GRANULE_PAGE) ||
> + WARN_ON(size % KASAN_GRANULE_PAGE))
> return;
>
> for (; addr < end; addr = next) {
> @@ -476,9 +475,8 @@ int kasan_add_zero_shadow(void *start, unsigned long size)
> shadow_start = kasan_mem_to_shadow(start);
> shadow_end = shadow_start + (size >> KASAN_SHADOW_SCALE_SHIFT);
>
> - if (WARN_ON((unsigned long)start %
> - (KASAN_GRANULE_SIZE * PAGE_SIZE)) ||
> - WARN_ON(size % (KASAN_GRANULE_SIZE * PAGE_SIZE)))
> + if (WARN_ON((unsigned long)start % KASAN_GRANULE_PAGE) ||
> + WARN_ON(size % KASAN_GRANULE_PAGE))
> return -EINVAL;
>
> ret = kasan_populate_early_shadow(shadow_start, shadow_end);
> diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
> index c31e2c739301..1865bb92d47a 100644
> --- a/mm/kasan/kasan.h
> +++ b/mm/kasan/kasan.h
> @@ -7,6 +7,7 @@
>
> #define KASAN_GRANULE_SIZE (1UL << KASAN_SHADOW_SCALE_SHIFT)
> #define KASAN_GRANULE_MASK (KASAN_GRANULE_SIZE - 1)
> +#define KASAN_GRANULE_PAGE (KASAN_GRANULE_SIZE << PAGE_SHIFT)
>
> #define KASAN_TAG_KERNEL 0xFF /* native kernel pointers tag */
> #define KASAN_TAG_INVALID 0xFE /* inaccessible memory tag */
> diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c
> index ca0cc4c31454..1fadd4930d54 100644
> --- a/mm/kasan/shadow.c
> +++ b/mm/kasan/shadow.c
> @@ -161,7 +161,7 @@ static int __meminit kasan_mem_notifier(struct notifier_block *nb,
> shadow_end = shadow_start + shadow_size;
>
> if (WARN_ON(mem_data->nr_pages % KASAN_GRANULE_SIZE) ||
> - WARN_ON(start_kaddr % (KASAN_GRANULE_SIZE << PAGE_SHIFT)))
> + WARN_ON(start_kaddr % KASAN_GRANULE_PAGE))
> return NOTIFY_BAD;
>
> switch (action) {
> @@ -432,22 +432,20 @@ void kasan_release_vmalloc(unsigned long start, unsigned long end,
> unsigned long region_start, region_end;
> unsigned long size;
>
> - region_start = ALIGN(start, PAGE_SIZE * KASAN_GRANULE_SIZE);
> - region_end = ALIGN_DOWN(end, PAGE_SIZE * KASAN_GRANULE_SIZE);
> + region_start = ALIGN(start, KASAN_GRANULE_PAGE);
> + region_end = ALIGN_DOWN(end, KASAN_GRANULE_PAGE);
>
> - free_region_start = ALIGN(free_region_start,
> - PAGE_SIZE * KASAN_GRANULE_SIZE);
> + free_region_start = ALIGN(free_region_start, KASAN_GRANULE_PAGE);
>
> if (start != region_start &&
> free_region_start < region_start)
> - region_start -= PAGE_SIZE * KASAN_GRANULE_SIZE;
> + region_start -= KASAN_GRANULE_PAGE;
>
> - free_region_end = ALIGN_DOWN(free_region_end,
> - PAGE_SIZE * KASAN_GRANULE_SIZE);
> + free_region_end = ALIGN_DOWN(free_region_end, KASAN_GRANULE_PAGE);
>
> if (end != region_end &&
> free_region_end > region_end)
> - region_end += PAGE_SIZE * KASAN_GRANULE_SIZE;
> + region_end += KASAN_GRANULE_PAGE;
>
> shadow_start = kasan_mem_to_shadow((void *)region_start);
> shadow_end = kasan_mem_to_shadow((void *)region_end);
> --
> 2.29.2.222.g5d2a92d10f8-goog
>
--
Alexander Potapenko
Software Engineer
Google Germany GmbH
Erika-Mann-Straße, 33
80636 München
Geschäftsführer: Paul Manicle, Halimah DeLaine Prado
Registergericht und -nummer: Hamburg, HRB 86891
Sitz der Gesellschaft: Hamburg
