Re: [PATCH RFC v2 12/21] kasan: inline and rename kasan_unpoison_memory

[Dmitry Vyukov]

On Thu, Oct 22, 2020 at 3:19 PM Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote:
>
> Currently kasan_unpoison_memory() is used as both an external annotation
> and as internal memory poisoning helper. Rename external annotation to
> kasan_unpoison_data() and inline the internal helper for for hardware
> tag-based mode to avoid undeeded function calls.
>
> There's the external annotation kasan_unpoison_slab() that is currently
> defined as static inline and uses kasan_unpoison_memory(). With this
> change it's turned into a function call. Overall, this results in the
> same number of calls for hardware tag-based mode as
> kasan_unpoison_memory() is now inlined.

Can't we leave kasan_unpoison_slab as is? Or there are other reasons
to uninline it?
It seems that uninling it is orthogonal to the rest of this patch.

> Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
> Link: https://linux-review.googlesource.com/id/Ia7c8b659f79209935cbaab3913bf7f082cc43a0e
> ---
>  include/linux/kasan.h | 16 ++++++----------
>  kernel/fork.c         |  2 +-
>  mm/kasan/common.c     | 10 ++++++++++
>  mm/kasan/hw_tags.c    |  6 ------
>  mm/kasan/kasan.h      |  7 +++++++
>  mm/slab_common.c      |  2 +-
>  6 files changed, 25 insertions(+), 18 deletions(-)
>
> diff --git a/include/linux/kasan.h b/include/linux/kasan.h
> index 6377d7d3a951..2b9023224474 100644
> --- a/include/linux/kasan.h
> +++ b/include/linux/kasan.h
> @@ -66,14 +66,15 @@ static inline void kasan_disable_current(void) {}
>
>  #ifdef CONFIG_KASAN
>
> -void kasan_unpoison_memory(const void *address, size_t size);
> -
>  void kasan_alloc_pages(struct page *page, unsigned int order);
>  void kasan_free_pages(struct page *page, unsigned int order);
>
>  void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
>                         slab_flags_t *flags);
>
> +void kasan_unpoison_data(const void *address, size_t size);
> +void kasan_unpoison_slab(const void *ptr);
> +
>  void kasan_poison_slab(struct page *page);
>  void kasan_unpoison_object_data(struct kmem_cache *cache, void *object);
>  void kasan_poison_object_data(struct kmem_cache *cache, void *object);
> @@ -98,11 +99,6 @@ struct kasan_cache {
>         int free_meta_offset;
>  };
>
> -size_t __ksize(const void *);
> -static inline void kasan_unpoison_slab(const void *ptr)
> -{
> -       kasan_unpoison_memory(ptr, __ksize(ptr));
> -}
>  size_t kasan_metadata_size(struct kmem_cache *cache);
>
>  bool kasan_save_enable_multi_shot(void);
> @@ -110,8 +106,6 @@ void kasan_restore_multi_shot(bool enabled);
>
>  #else /* CONFIG_KASAN */
>
> -static inline void kasan_unpoison_memory(const void *address, size_t size) {}
> -
>  static inline void kasan_alloc_pages(struct page *page, unsigned int order) {}
>  static inline void kasan_free_pages(struct page *page, unsigned int order) {}
>
> @@ -119,6 +113,9 @@ static inline void kasan_cache_create(struct kmem_cache *cache,
>                                       unsigned int *size,
>                                       slab_flags_t *flags) {}
>
> +static inline void kasan_unpoison_data(const void *address, size_t size) { }
> +static inline void kasan_unpoison_slab(const void *ptr) { }
> +
>  static inline void kasan_poison_slab(struct page *page) {}
>  static inline void kasan_unpoison_object_data(struct kmem_cache *cache,
>                                         void *object) {}
> @@ -158,7 +155,6 @@ static inline bool kasan_slab_free(struct kmem_cache *s, void *object,
>         return false;
>  }
>
> -static inline void kasan_unpoison_slab(const void *ptr) { }
>  static inline size_t kasan_metadata_size(struct kmem_cache *cache) { return 0; }
>
>  #endif /* CONFIG_KASAN */
> diff --git a/kernel/fork.c b/kernel/fork.c
> index b41fecca59d7..858d78eee6ec 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -225,7 +225,7 @@ static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
>                         continue;
>
>                 /* Mark stack accessible for KASAN. */
> -               kasan_unpoison_memory(s->addr, THREAD_SIZE);
> +               kasan_unpoison_data(s->addr, THREAD_SIZE);
>
>                 /* Clear stale pointers from reused stack. */
>                 memset(s->addr, 0, THREAD_SIZE);
> diff --git a/mm/kasan/common.c b/mm/kasan/common.c
> index 9008fc6b0810..1a5e6c279a72 100644
> --- a/mm/kasan/common.c
> +++ b/mm/kasan/common.c
> @@ -184,6 +184,16 @@ struct kasan_free_meta *kasan_get_free_meta(struct kmem_cache *cache,
>         return (void *)reset_tag(object) + cache->kasan_info.free_meta_offset;
>  }
>
> +void kasan_unpoison_data(const void *address, size_t size)
> +{
> +       kasan_unpoison_memory(address, size);
> +}
> +
> +void kasan_unpoison_slab(const void *ptr)
> +{
> +       kasan_unpoison_memory(ptr, __ksize(ptr));
> +}
> +
>  void kasan_poison_slab(struct page *page)
>  {
>         unsigned long i;
> diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c
> index f03161f3da19..915142da6b57 100644
> --- a/mm/kasan/hw_tags.c
> +++ b/mm/kasan/hw_tags.c
> @@ -24,12 +24,6 @@ void __init kasan_init_tags(void)
>         pr_info("KernelAddressSanitizer initialized\n");
>  }
>
> -void kasan_unpoison_memory(const void *address, size_t size)
> -{
> -       set_mem_tag_range(reset_tag(address),
> -                         round_up(size, KASAN_GRANULE_SIZE), get_tag(address));
> -}
> -
>  void kasan_set_free_info(struct kmem_cache *cache,
>                                 void *object, u8 tag)
>  {
> diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
> index 8d84ae6f58f1..da08b2533d73 100644
> --- a/mm/kasan/kasan.h
> +++ b/mm/kasan/kasan.h
> @@ -280,6 +280,12 @@ static inline void kasan_poison_memory(const void *address, size_t size, u8 valu
>                           round_up(size, KASAN_GRANULE_SIZE), value);
>  }
>
> +static inline void kasan_unpoison_memory(const void *address, size_t size)
> +{
> +       set_mem_tag_range(reset_tag(address),
> +                         round_up(size, KASAN_GRANULE_SIZE), get_tag(address));
> +}
> +
>  static inline bool check_invalid_free(void *addr)
>  {
>         u8 ptr_tag = get_tag(addr);
> @@ -292,6 +298,7 @@ static inline bool check_invalid_free(void *addr)
>  #else /* CONFIG_KASAN_HW_TAGS */
>
>  void kasan_poison_memory(const void *address, size_t size, u8 value);
> +void kasan_unpoison_memory(const void *address, size_t size);
>  bool check_invalid_free(void *addr);
>
>  #endif /* CONFIG_KASAN_HW_TAGS */
> diff --git a/mm/slab_common.c b/mm/slab_common.c
> index 53d0f8bb57ea..f1b0c4a22f08 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -1176,7 +1176,7 @@ size_t ksize(const void *objp)
>          * We assume that ksize callers could use whole allocated area,
>          * so we need to unpoison this area.
>          */
> -       kasan_unpoison_memory(objp, size);
> +       kasan_unpoison_data(objp, size);
>         return size;
>  }
>  EXPORT_SYMBOL(ksize);
> --
> 2.29.0.rc1.297.gfa9743e501-goog
>