Re: [PATCH 10/12] arm64: kasan: simplify and inline MTE functions

[Catalin Marinas]

On Mon, Feb 01, 2021 at 08:43:34PM +0100, Andrey Konovalov wrote:
> +/*
> + * Assign allocation tags for a region of memory based on the pointer tag.
> + * Note: The address must be non-NULL and MTE_GRANULE_SIZE aligned and
> + * size must be non-zero and MTE_GRANULE_SIZE aligned.
> + */

OK, so we rely on the caller to sanity-check the range. Fine by me but I
can see (un)poison_range() only doing this for the size. Do we guarantee
that the start address is aligned?

> +static __always_inline void mte_set_mem_tag_range(void *addr, size_t size, u8 tag)
> +{
> +	u64 curr, end;
> +
> +	if (!size)
> +		return;
> +
> +	curr = (u64)__tag_set(addr, tag);
> +	end = curr + size;
> +
> +	do {
> +		/*
> +		 * 'asm volatile' is required to prevent the compiler to move
> +		 * the statement outside of the loop.
> +		 */
> +		asm volatile(__MTE_PREAMBLE "stg %0, [%0]"
> +			     :
> +			     : "r" (curr)
> +			     : "memory");
> +
> +		curr += MTE_GRANULE_SIZE;
> +	} while (curr != end);
> +}
>  
>  void mte_enable_kernel_sync(void);
>  void mte_enable_kernel_async(void);
> @@ -47,10 +95,12 @@ static inline u8 mte_get_mem_tag(void *addr)
>  {
>  	return 0xFF;
>  }
> +
>  static inline u8 mte_get_random_tag(void)
>  {
>  	return 0xFF;
>  }
> +
>  static inline void *mte_set_mem_tag_range(void *addr, size_t size, u8 tag)

This function used to return a pointer and that's what the dummy static
inline does here. However, the new mte_set_mem_tag_range() doesn't
return anything. We should have consistency between the two (the new
static void definition is fine by me).

Otherwise the patch looks fine.

Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx>