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

[Usama Arif <usama.arif@xxxxxxxxx>]

On Mon, 27 Apr 2026 19:13:48 +0200 "Christophe Leroy (CS GROUP)" 
<chleroy@xxxxxxxxxx> wrote:

> At the time being, x86 and arm64 are missing unsafe_copy_from_user().
> 
> Add it.
> 
> Signed-off-by: Christophe Leroy (CS GROUP) <chleroy@xxxxxxxxxx>
> ---
>  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
> 
>