[PATCH 6/8] riscv: refactor __get_user and __put_user

[Palmer Dabbelt]

On Sun, 06 Sep 2020 22:58:23 PDT (-0700), Christoph Hellwig wrote:
> Add new __get_user_nocheck and __put_user_nocheck that switch on the size
> and call the actual inline assembly helpers, and move the uaccess enable
> / disable into the actual __get_user and __put_user.  This prepares for
> natively implementing __get_kernel_nofault and __put_kernel_nofault.
>
> Also don't bother with the deprecated register keyword for the error
> return.
>
> Signed-off-by: Christoph Hellwig <hch at lst.de>
> ---
>  arch/riscv/include/asm/uaccess.h | 94 ++++++++++++++++++--------------
>  1 file changed, 52 insertions(+), 42 deletions(-)
>
> diff --git a/arch/riscv/include/asm/uaccess.h b/arch/riscv/include/asm/uaccess.h
> index e8eedf22e90747..b67d1c616ec348 100644
> --- a/arch/riscv/include/asm/uaccess.h
> +++ b/arch/riscv/include/asm/uaccess.h
> @@ -107,7 +107,6 @@ static inline int __access_ok(unsigned long addr, unsigned long size)
>  do {								\
>  	uintptr_t __tmp;					\
>  	__typeof__(x) __x;					\
> -	__enable_user_access();					\
>  	__asm__ __volatile__ (					\
>  		"1:\n"						\
>  		"	" insn " %1, %3\n"			\
> @@ -125,7 +124,6 @@ do {								\
>  		"	.previous"				\
>  		: "+r" (err), "=&r" (__x), "=r" (__tmp)		\
>  		: "m" (*(ptr)), "i" (-EFAULT));			\
> -	__disable_user_access();				\
>  	(x) = __x;						\
>  } while (0)
>
> @@ -138,7 +136,6 @@ do {								\
>  	u32 __user *__ptr = (u32 __user *)(ptr);		\
>  	u32 __lo, __hi;						\
>  	uintptr_t __tmp;					\
> -	__enable_user_access();					\
>  	__asm__ __volatile__ (					\
>  		"1:\n"						\
>  		"	lw %1, %4\n"				\
> @@ -162,12 +159,30 @@ do {								\
>  			"=r" (__tmp)				\
>  		: "m" (__ptr[__LSW]), "m" (__ptr[__MSW]),	\
>  			"i" (-EFAULT));				\
> -	__disable_user_access();				\
>  	(x) = (__typeof__(x))((__typeof__((x)-(x)))(		\
>  		(((u64)__hi << 32) | __lo)));			\
>  } while (0)
>  #endif /* CONFIG_64BIT */
>
> +#define __get_user_nocheck(x, __gu_ptr, __gu_err)		\
> +do {								\
> +	switch (sizeof(*__gu_ptr)) {				\
> +	case 1:							\
> +		__get_user_asm("lb", (x), __gu_ptr, __gu_err);	\
> +		break;						\
> +	case 2:							\
> +		__get_user_asm("lh", (x), __gu_ptr, __gu_err);	\
> +		break;						\
> +	case 4:							\
> +		__get_user_asm("lw", (x), __gu_ptr, __gu_err);	\
> +		break;						\
> +	case 8:							\
> +		__get_user_8((x), __gu_ptr, __gu_err);	\
> +		break;						\
> +	default:						\
> +		BUILD_BUG();					\
> +	}							\
> +} while (0)
>
>  /**
>   * __get_user: - Get a simple variable from user space, with less checking.
> @@ -191,25 +206,15 @@ do {								\
>   */
>  #define __get_user(x, ptr)					\
>  ({								\
> -	register long __gu_err = 0;				\
>  	const __typeof__(*(ptr)) __user *__gu_ptr = (ptr);	\
> +	long __gu_err = 0;					\
> +								\
>  	__chk_user_ptr(__gu_ptr);				\
> -	switch (sizeof(*__gu_ptr)) {				\
> -	case 1:							\
> -		__get_user_asm("lb", (x), __gu_ptr, __gu_err);	\
> -		break;						\
> -	case 2:							\
> -		__get_user_asm("lh", (x), __gu_ptr, __gu_err);	\
> -		break;						\
> -	case 4:							\
> -		__get_user_asm("lw", (x), __gu_ptr, __gu_err);	\
> -		break;						\
> -	case 8:							\
> -		__get_user_8((x), __gu_ptr, __gu_err);	\
> -		break;						\
> -	default:						\
> -		BUILD_BUG();					\
> -	}							\
> +								\
> +	__enable_user_access();					\
> +	__get_user_nocheck(x, __gu_ptr, __gu_err);		\
> +	__disable_user_access();				\
> +								\
>  	__gu_err;						\
>  })
>
> @@ -243,7 +248,6 @@ do {								\
>  do {								\
>  	uintptr_t __tmp;					\
>  	__typeof__(*(ptr)) __x = x;				\
> -	__enable_user_access();					\
>  	__asm__ __volatile__ (					\
>  		"1:\n"						\
>  		"	" insn " %z3, %2\n"			\
> @@ -260,7 +264,6 @@ do {								\
>  		"	.previous"				\
>  		: "+r" (err), "=r" (__tmp), "=m" (*(ptr))	\
>  		: "rJ" (__x), "i" (-EFAULT));			\
> -	__disable_user_access();				\
>  } while (0)
>
>  #ifdef CONFIG_64BIT
> @@ -272,7 +275,6 @@ do {								\
>  	u32 __user *__ptr = (u32 __user *)(ptr);		\
>  	u64 __x = (__typeof__((x)-(x)))(x);			\
>  	uintptr_t __tmp;					\
> -	__enable_user_access();					\
>  	__asm__ __volatile__ (					\
>  		"1:\n"						\
>  		"	sw %z4, %2\n"				\
> @@ -294,10 +296,28 @@ do {								\
>  			"=m" (__ptr[__LSW]),			\
>  			"=m" (__ptr[__MSW])			\
>  		: "rJ" (__x), "rJ" (__x >> 32), "i" (-EFAULT));	\
> -	__disable_user_access();				\
>  } while (0)
>  #endif /* CONFIG_64BIT */
>
> +#define __put_user_nocheck(x, __gu_ptr, __pu_err)					\
> +do {								\
> +	switch (sizeof(*__gu_ptr)) {				\
> +	case 1:							\
> +		__put_user_asm("sb", (x), __gu_ptr, __pu_err);	\
> +		break;						\
> +	case 2:							\
> +		__put_user_asm("sh", (x), __gu_ptr, __pu_err);	\
> +		break;						\
> +	case 4:							\
> +		__put_user_asm("sw", (x), __gu_ptr, __pu_err);	\
> +		break;						\
> +	case 8:							\
> +		__put_user_8((x), __gu_ptr, __pu_err);	\
> +		break;						\
> +	default:						\
> +		BUILD_BUG();					\
> +	}							\
> +} while (0)
>
>  /**
>   * __put_user: - Write a simple value into user space, with less checking.
> @@ -320,25 +340,15 @@ do {								\
>   */
>  #define __put_user(x, ptr)					\
>  ({								\
> -	register long __pu_err = 0;				\
>  	__typeof__(*(ptr)) __user *__gu_ptr = (ptr);		\
> +	long __pu_err = 0;					\
> +								\
>  	__chk_user_ptr(__gu_ptr);				\
> -	switch (sizeof(*__gu_ptr)) {				\
> -	case 1:							\
> -		__put_user_asm("sb", (x), __gu_ptr, __pu_err);	\
> -		break;						\
> -	case 2:							\
> -		__put_user_asm("sh", (x), __gu_ptr, __pu_err);	\
> -		break;						\
> -	case 4:							\
> -		__put_user_asm("sw", (x), __gu_ptr, __pu_err);	\
> -		break;						\
> -	case 8:							\
> -		__put_user_8((x), __gu_ptr, __pu_err);	\
> -		break;						\
> -	default:						\
> -		BUILD_BUG();					\
> -	}							\
> +								\
> +	__enable_user_access();					\
> +	__put_user_nocheck(x, __gu_ptr, __pu_err);		\
> +	__disable_user_access();				\
> +								\
>  	__pu_err;						\
>  })

Reviewed-by: Palmer Dabbelt <palmerdabbelt at google.com>
Acked-by: Palmer Dabbelt <palmerdabbelt at google.com>