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

Jens Remus
2026-05-06T14:10:25Z

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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