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

[David Laight]

On Wed, 6 May 2026 16:09:16 +0200
Jens Remus <jremus@xxxxxxxxxxxxx> wrote:

> On 5/5/2026 2:17 PM, Jens Remus wrote:
> > From: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
> > 
> > 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?

Try compiling it :-)

-- David

> 
> > +	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