Re: [patch V5 08/12] uaccess: Provide put/get_user_inline()

[Christophe Leroy <christophe.leroy@csgroup.eu>]

Le 27/10/2025 à 09:43, Thomas Gleixner a écrit :
> Provide conveniance wrappers around scoped user access similiar to
> put/get_user(), which reduce the usage sites to:
> 
>         if (!get_user_inline(val, ptr))
>         		return -EFAULT;
> 
> Should only be used if there is a demonstrable performance benefit.
> 
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>

> ---
> V5: Rename to inline
> V4: Rename to scoped
> ---
>   include/linux/uaccess.h |   50 ++++++++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 50 insertions(+)
> 
> --- a/include/linux/uaccess.h
> +++ b/include/linux/uaccess.h
> @@ -825,6 +825,56 @@ for (bool done = false; !done; done = tr
>   #define scoped_user_rw_access(uptr, elbl)				\
>   	scoped_user_rw_access_size(uptr, sizeof(*(uptr)), elbl)
>   
> +/**
> + * get_user_inline - Read user data inlined
> + * @val:	The variable to store the value read from user memory
> + * @usrc:	Pointer to the user space memory to read from
> + *
> + * Return: 0 if successful, -EFAULT when faulted
> + *
> + * Inlined variant of get_user(). Only use when there is a demonstrable
> + * performance reason.
> + */
> +#define get_user_inline(val, usrc)				\
> +({								\
> +	__label__ efault;					\
> +	typeof(usrc) _tmpsrc = usrc;				\
> +	int _ret = 0;						\
> +								\
> +	scoped_user_read_access(_tmpsrc, efault)		\
> +		unsafe_get_user(val, _tmpsrc, efault);		\
> +	if (0) {						\
> +	efault:							\
> +		_ret = -EFAULT;					\
> +	}							\
> +	_ret;							\
> +})
> +
> +/**
> + * put_user_inline - Write to user memory inlined
> + * @val:	The value to write
> + * @udst:	Pointer to the user space memory to write to
> + *
> + * Return: 0 if successful, -EFAULT when faulted
> + *
> + * Inlined variant of put_user(). Only use when there is a demonstrable
> + * performance reason.
> + */
> +#define put_user_inline(val, udst)				\
> +({								\
> +	__label__ efault;					\
> +	typeof(udst) _tmpdst = udst;				\
> +	int _ret = 0;						\
> +								\
> +	scoped_user_write_access(_tmpdst, efault)		\
> +		unsafe_put_user(val, _tmpdst, efault);		\
> +	if (0) {						\
> +	efault:							\
> +		_ret = -EFAULT;					\
> +	}							\
> +	_ret;							\
> +})
> +
>   #ifdef CONFIG_HARDENED_USERCOPY
>   void __noreturn usercopy_abort(const char *name, const char *detail,
>   			       bool to_user, unsigned long offset,
> 


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