Commit 5cd29b1f authored by Christophe Leroy's avatar Christophe Leroy Committed by Michael Ellerman
Browse files

powerpc/uaccess: Use asm goto for get_user when compiler supports it 



clang 11 and future GCC are supporting asm goto with outputs.

Use it to implement get_user in order to get better generated code.

Note that clang requires to set x in the default branch of
__get_user_size_goto() otherwise is compliant about x not being
initialised :puzzled:

Signed-off-by: default avatarChristophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/403745b5aaa1b315bb4e8e46c1ba949e77eecec0.1615398265.git.christophe.leroy@csgroup.eu
parent 035785ab

arch/powerpc/include/asm/uaccess.h

+55 −0
Original line number Diff line number Diff line
@@ -136,6 +136,59 @@ do { \ 
		: "=r" (err)			\

		: "b" (uaddr), "b" (kaddr), "i" (-EFAULT), "0" (err))



#ifdef CONFIG_CC_HAS_ASM_GOTO_OUTPUT



#define __get_user_asm_goto(x, addr, label, op)			\

	asm_volatile_goto(					\

		"1:	"op"%U1%X1 %0, %1	# get_user\n"	\

		EX_TABLE(1b, %l2)				\

		: "=r" (x)					\

		: "m"UPD_CONSTR (*addr)				\

		:						\

		: label)



#ifdef __powerpc64__

#define __get_user_asm2_goto(x, addr, label)			\

	__get_user_asm_goto(x, addr, label, "ld")

#else /* __powerpc64__ */

#define __get_user_asm2_goto(x, addr, label)			\

	asm_volatile_goto(					\

		"1:	lwz%X1 %0, %1\n"			\

		"2:	lwz%X1 %L0, %L1\n"			\

		EX_TABLE(1b, %l2)				\

		EX_TABLE(2b, %l2)				\

		: "=r" (x)					\

		: "m" (*addr)					\

		:						\

		: label)

#endif /* __powerpc64__ */



#define __get_user_size_goto(x, ptr, size, label)				\

do {										\

	BUILD_BUG_ON(size > sizeof(x));						\

	switch (size) {								\

	case 1: __get_user_asm_goto(x, (u8 __user *)ptr, label, "lbz"); break;	\

	case 2: __get_user_asm_goto(x, (u16 __user *)ptr, label, "lhz"); break;	\

	case 4: __get_user_asm_goto(x, (u32 __user *)ptr, label, "lwz"); break;	\

	case 8: __get_user_asm2_goto(x, (u64 __user *)ptr, label);  break;	\

	default: x = 0; BUILD_BUG();						\

	}									\

} while (0)



#define __get_user_size_allowed(x, ptr, size, retval)			\

do {									\

		__label__ __gus_failed;					\

									\

		__get_user_size_goto(x, ptr, size, __gus_failed);	\

		retval = 0;						\

		break;							\

__gus_failed:								\

		x = 0;							\

		retval = -EFAULT;					\

} while (0)



#else /* CONFIG_CC_HAS_ASM_GOTO_OUTPUT */



#define __get_user_asm(x, addr, err, op)		\

	__asm__ __volatile__(				\

		"1:	"op"%U2%X2 %1, %2	# get_user\n"	\
@@ -192,6 +245,8 @@ do { \ 
		goto label;					\

} while (0)



#endif /* CONFIG_CC_HAS_ASM_GOTO_OUTPUT */



/*

 * This is a type: either unsigned long, if the argument fits into

 * that type, or otherwise unsigned long long.