Re: [PATCH v14 04/19] x86/uaccess: Add unsafe_copy_from_user() implementation

[Jens Remus <jremus@linux.ibm.com>]

On 5/5/2026 2:17 PM, Jens Remus wrote:
> From: Josh Poimboeuf <jpoimboe@kernel.org>
> 
> Add an x86 implementation of unsafe_copy_from_user() similar to the
> existing unsafe_copy_to_user().

> diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h

> -#define unsafe_copy_to_user(_dst,_src,_len,label)			\
> -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);	\
> +#define unsafe_copy_to_user(_dst, _src, _len, label)				\
> +do {										\
> +	void __user *__dst = (_dst);						\
> +	const void *__src = (_src);						\
> +	size_t __len = (_len);							\
> +	unsafe_copy_to_user_loop(__dst, __src, __len, u64, label);		\
> +	unsafe_copy_to_user_loop(__dst, __src, __len, u32, label);		\
> +	unsafe_copy_to_user_loop(__dst, __src, __len, u16, label);		\
> +	unsafe_copy_to_user_loop(__dst, __src, __len, u8,  label);		\
> +} while (0)
> +
> +#define unsafe_copy_from_user_loop(dst, src, len, type, label)			\
> +	while (len >= sizeof(type)) {						\
> +		unsafe_get_user(*(type *)(dst), (type __user *)(src), label);	\
> +		dst += sizeof(type);						\
> +		src += sizeof(type);						\
> +		len -= sizeof(type);						\
> +	}
> +
> +#define unsafe_copy_from_user(_dst, _src, _len, label)				\
> +do {										\
> +	void *__dst = (_dst);							\
> +	void __user *__src = (_src);						\

	const void __user *__src = (_src);					\

This was suggested by Sashiko AI review.  Any objections?

> +	size_t __len = (_len);							\
> +	unsafe_copy_from_user_loop(__dst, __src, __len, u64, label);		\
> +	unsafe_copy_from_user_loop(__dst, __src, __len, u32, label);		\
> +	unsafe_copy_from_user_loop(__dst, __src, __len, u16, label);		\
> +	unsafe_copy_from_user_loop(__dst, __src, __len, u8,  label);		\
>  } while (0)
>  
>  #ifdef CONFIG_CC_HAS_ASM_GOTO_OUTPUT

Thanks and regards,
Jens
-- 
Jens Remus
Linux on Z Development (D3303)
jremus@de.ibm.com / jremus@linux.ibm.com

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