Subject: Re: [RFC PATCH v1 7/9] x86: Add unsafe_copy_from_user()

From: Usama Arif <[email-masked]>
Date: Wed, 29 Apr 2026 03:25:19 -0700

On Mon, 27 Apr 2026 19:13:48 +0200 "Christophe Leroy (CS GROUP)" <[email-masked]> wrote:

> At the time being, x86 and arm64 are missing unsafe_copy_from_user().
> 
> Add it.
> 
> Signed-off-by: Christophe Leroy (CS GROUP) <[email-masked]>
> ---
>  arch/x86/include/asm/uaccess.h | 29 ++++++++++++++++++++++++-----
>  1 file changed, 24 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
> index 3a0dd3c2b233..10c458ffa399 100644
> --- a/arch/x86/include/asm/uaccess.h
> +++ b/arch/x86/include/asm/uaccess.h
> @@ -598,7 +598,7 @@ _label:									\
>   * We want the unsafe accessors to always be inlined and use
>   * the error labels - thus the macro games.
>   */
> -#define unsafe_copy_loop(dst, src, len, type, label)				\
> +#define unsafe_put_loop(dst, src, len, type, label)				\
>  	while (len >= sizeof(type)) {						\
>  		unsafe_put_user(*(type *)(src),(type __user *)(dst),label);	\
>  		dst += sizeof(type);						\
> @@ -611,10 +611,29 @@ do {									\
>  	char __user *__ucu_dst = (_dst);				\
>  	const char *__ucu_src = (_src);					\
>  	size_t __ucu_len = (_len);					\
> -	unsafe_copy_loop(__ucu_dst, __ucu_src, __ucu_len, u64, label);	\
> -	unsafe_copy_loop(__ucu_dst, __ucu_src, __ucu_len, u32, label);	\
> -	unsafe_copy_loop(__ucu_dst, __ucu_src, __ucu_len, u16, label);	\
> -	unsafe_copy_loop(__ucu_dst, __ucu_src, __ucu_len, u8, label);	\
> +	unsafe_put_loop(__ucu_dst, __ucu_src, __ucu_len, u64, label);	\
> +	unsafe_put_loop(__ucu_dst, __ucu_src, __ucu_len, u32, label);	\
> +	unsafe_put_loop(__ucu_dst, __ucu_src, __ucu_len, u16, label);	\
> +	unsafe_put_loop(__ucu_dst, __ucu_src, __ucu_len, u8, label);	\
> +} while (0)
> +
> +#define unsafe_get_loop(dst, src, len, type, label)				\
> +	while (len >= sizeof(type)) {						\
> +		unsafe_get_user(*(type __user *)(src),(type *)(dst),label);	\

Hi,

Just wanted to check if src and dst need to be swapped? Same for arm64 patch.

> +		dst += sizeof(type);						\
> +		src += sizeof(type);						\
> +		len -= sizeof(type);						\
> +	}
> +
> +#define unsafe_copy_from_user(_dst,_src,_len,label)			\
> +do {									\
> +	char *__ucu_dst = (_dst);					\
> +	const char __user *__ucu_src = (_src);				\
> +	size_t __ucu_len = (_len);					\
> +	unsafe_get_loop(__ucu_dst, __ucu_src, __ucu_len, u64, label);	\
> +	unsafe_get_loop(__ucu_dst, __ucu_src, __ucu_len, u32, label);	\
> +	unsafe_get_loop(__ucu_dst, __ucu_src, __ucu_len, u16, label);	\
> +	unsafe_get_loop(__ucu_dst, __ucu_src, __ucu_len, u8, label);	\
>  } while (0)
>  
>  #ifdef CONFIG_CC_HAS_ASM_GOTO_OUTPUT
> -- 
> 2.49.0
> 
>