[PATCH v1 3/3] powerpc/code-patching: Optimise patch_memcpy() to 4 byte chunks

[Christophe Leroy]

Le 15/03/2024 à 03:57, Benjamin Gray a écrit :
> As we are patching instructions, we can assume the length is a multiple
> of 4 and the destination address is aligned.
> 
> Atomicity of patching a prefixed instruction is not a concern, as the
> original implementation doesn't provide it anyway.

This patch looks unnecessary.

copy_to_kernel_nofault() is what you want to use instead.

> 
> Signed-off-by: Benjamin Gray <bgray at linux.ibm.com>
> ---
>   arch/powerpc/lib/code-patching.c | 8 ++++----
>   1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
> index c6633759b509..ed450a32918c 100644
> --- a/arch/powerpc/lib/code-patching.c
> +++ b/arch/powerpc/lib/code-patching.c
> @@ -394,10 +394,10 @@ static int patch_memset32(u32 *addr, u32 val, size_t count)
>   	return -EPERM;
>   }
>   
> -static int patch_memcpy(void *dst, void *src, size_t len)
> +static int patch_memcpy32(u32 *dst, u32 *src, size_t count)
>   {
> -	for (void *end = src + len; src < end; dst++, src++)
> -		__put_kernel_nofault(dst, src, u8, failed);
> +	for (u32 *end = src + count; src < end; dst++, src++)
> +		__put_kernel_nofault(dst, src, u32, failed);
>   
>   	return 0;
>   
> @@ -424,7 +424,7 @@ static int __patch_instructions(u32 *patch_addr, u32 *code, size_t len, bool rep
>   			err = patch_memset32(patch_addr, val, len / 4);
>   		}
>   	} else {
> -		err = patch_memcpy(patch_addr, code, len);
> +		err = patch_memcpy32(patch_addr, code, len / 4);
>   	}
>   
>   	smp_wmb();	/* smp write barrier */