Re: [PATCH RFC bpf-next 1/8] kasan: expose generic kasan helpers

[Andrey Konovalov <andreyknvl@gmail.com>]

On Mon, Apr 13, 2026 at 8:29 PM Alexis Lothoré (eBPF Foundation)
<alexis.lothore@bootlin.com> wrote:
>
> In order to prepare KASAN helpers to be called from the eBPF subsystem
> (to add KASAN instrumentation at runtime when JITing eBPF programs),
> expose the __asan_{load,store}X functions in linux/kasan.h
>
> Signed-off-by: Alexis Lothoré (eBPF Foundation) <alexis.lothore@bootlin.com>
> ---
>  include/linux/kasan.h | 13 +++++++++++++
>  mm/kasan/kasan.h      | 10 ----------
>  2 files changed, 13 insertions(+), 10 deletions(-)
>
> diff --git a/include/linux/kasan.h b/include/linux/kasan.h
> index 338a1921a50a..6f580d4a39e4 100644
> --- a/include/linux/kasan.h
> +++ b/include/linux/kasan.h
> @@ -710,4 +710,17 @@ void kasan_non_canonical_hook(unsigned long addr);
>  static inline void kasan_non_canonical_hook(unsigned long addr) { }
>  #endif /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */
>
> +#ifdef CONFIG_KASAN_GENERIC
> +void __asan_load1(void *p);
> +void __asan_store1(void *p);
> +void __asan_load2(void *p);
> +void __asan_store2(void *p);
> +void __asan_load4(void *p);
> +void __asan_store4(void *p);
> +void __asan_load8(void *p);
> +void __asan_store8(void *p);
> +void __asan_load16(void *p);
> +void __asan_store16(void *p);
> +#endif /* CONFIG_KASAN_GENERIC */

This looks ugly, let's not do this unless it's really required.

You can just use kasan_check_read/write() instead - these are public
wrappers around the same shadow memory checking functions. And they
also work with the SW_TAGS mode, in case the BPF would want to use
that mode at some point. (For HW_TAGS, we only have kasan_check_byte()
that checks a single byte, but it can be extended in the future if
required to be used by BPF.)



> +
>  #endif /* LINUX_KASAN_H */
> diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
> index fc9169a54766..3bfce8eb3135 100644
> --- a/mm/kasan/kasan.h
> +++ b/mm/kasan/kasan.h
> @@ -594,16 +594,6 @@ void __asan_handle_no_return(void);
>  void __asan_alloca_poison(void *, ssize_t size);
>  void __asan_allocas_unpoison(void *stack_top, ssize_t stack_bottom);
>
> -void __asan_load1(void *);
> -void __asan_store1(void *);
> -void __asan_load2(void *);
> -void __asan_store2(void *);
> -void __asan_load4(void *);
> -void __asan_store4(void *);
> -void __asan_load8(void *);
> -void __asan_store8(void *);
> -void __asan_load16(void *);
> -void __asan_store16(void *);
>  void __asan_loadN(void *, ssize_t size);
>  void __asan_storeN(void *, ssize_t size);
>
>
> --
> 2.53.0
>