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References: <20230328095807.7014-1-songmuchun@bytedance.com> <20230328095807.7014-7-songmuchun@bytedance.com>
In-Reply-To: <20230328095807.7014-7-songmuchun@bytedance.com>
From:   Marco Elver <elver@google.com>
Date:   Tue, 28 Mar 2023 13:55:38 +0200
Message-ID: <CANpmjNPeQBcV7qnpXJOoLYjonsjPnOW-cerYm=_U3ptNZrXu0Q@mail.gmail.com>
Subject: Re: [PATCH 6/6] mm: kfence: replace ALIGN_DOWN(x, PAGE_SIZE) with PAGE_ALIGN_DOWN(x)
To:     Muchun Song <songmuchun@bytedance.com>
Cc:     glider@google.com, dvyukov@google.com, akpm@linux-foundation.org,
        jannh@google.com, sjpark@amazon.de, muchun.song@linux.dev,
        kasan-dev@googlegroups.com, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
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Precedence: bulk

On Tue, 28 Mar 2023 at 11:59, 'Muchun Song' via kasan-dev
<kasan-dev@googlegroups.com> wrote:
>
> Replace ALIGN_DOWN(x, PAGE_SIZE) with PAGE_ALIGN_DOWN(x) to simplify
> the code a bit.
>
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>

Reviewed-by: Marco Elver <elver@google.com>

> ---
>  mm/kfence/core.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/mm/kfence/core.c b/mm/kfence/core.c
> index f205b860f460..dbfb79a4d624 100644
> --- a/mm/kfence/core.c
> +++ b/mm/kfence/core.c
> @@ -230,17 +230,17 @@ static bool alloc_covered_contains(u32 alloc_stack_hash)
>
>  static inline void kfence_protect(unsigned long addr)
>  {
> -       kfence_protect_page(ALIGN_DOWN(addr, PAGE_SIZE), true);
> +       kfence_protect_page(PAGE_ALIGN_DOWN(addr), true);
>  }
>
>  static inline void kfence_unprotect(unsigned long addr)
>  {
> -       kfence_protect_page(ALIGN_DOWN(addr, PAGE_SIZE), false);
> +       kfence_protect_page(PAGE_ALIGN_DOWN(addr), false);
>  }
>
>  static inline unsigned long metadata_to_pageaddr(const struct kfence_metadata *meta)
>  {
> -       return ALIGN_DOWN(meta->addr, PAGE_SIZE);
> +       return PAGE_ALIGN_DOWN(meta->addr);
>  }
>
>  /*
> @@ -308,7 +308,7 @@ static inline bool check_canary_byte(u8 *addr)
>  /* __always_inline this to ensure we won't do an indirect call to fn. */
>  static __always_inline void for_each_canary(const struct kfence_metadata *meta, bool (*fn)(u8 *))
>  {
> -       const unsigned long pageaddr = ALIGN_DOWN(meta->addr, PAGE_SIZE);
> +       const unsigned long pageaddr = PAGE_ALIGN_DOWN(meta->addr);
>         unsigned long addr;
>
>         /*
> @@ -455,7 +455,7 @@ static void kfence_guarded_free(void *addr, struct kfence_metadata *meta, bool z
>         }
>
>         /* Detect racy use-after-free, or incorrect reallocation of this page by KFENCE. */
> -       kcsan_begin_scoped_access((void *)ALIGN_DOWN((unsigned long)addr, PAGE_SIZE), PAGE_SIZE,
> +       kcsan_begin_scoped_access((void *)PAGE_ALIGN_DOWN((unsigned long)addr), PAGE_SIZE,
>                                   KCSAN_ACCESS_SCOPED | KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ASSERT,
>                                   &assert_page_exclusive);
>
> @@ -464,7 +464,7 @@ static void kfence_guarded_free(void *addr, struct kfence_metadata *meta, bool z
>
>         /* Restore page protection if there was an OOB access. */
>         if (meta->unprotected_page) {
> -               memzero_explicit((void *)ALIGN_DOWN(meta->unprotected_page, PAGE_SIZE), PAGE_SIZE);
> +               memzero_explicit((void *)PAGE_ALIGN_DOWN(meta->unprotected_page), PAGE_SIZE);
>                 kfence_protect(meta->unprotected_page);
>                 meta->unprotected_page = 0;
>         }
> --
> 2.11.0
>
> --
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