Message ID | 20230314153700.787701-4-mark.rutland@arm.com (mailing list archive) |
---|---|
State | New, archived |
Headers | show |
Series | arm64: asm improvements | expand |
diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h index 5c7b2f9d5913..4ee5aa7bd5a2 100644 --- a/arch/arm64/include/asm/uaccess.h +++ b/arch/arm64/include/asm/uaccess.h @@ -327,7 +327,7 @@ do { \ "2:\n" \ _ASM_EXTABLE_##type##ACCESS_ERR(1b, 2b, %w0) \ : "+r" (err) \ - : "r" (x), "r" (addr)) + : "rZ" (x), "r" (addr)) #define __raw_put_mem(str, x, ptr, err, type) \ do { \
Currently the asm constraints for __put_mem_asm() require that the value is placed in a "real" GPR (i.e. one other than [XW]ZR or SP). This means that for cases such as: __put_user(0, addr) ... the compiler has to move '0' into "real" GPR, e.g. mov xN, #0 sttr xN, [<addr>] This is unfortunate, as using the zero register would require fewer instructions and save a "real" GPR for other usage, allowing the compiler to generate: sttr xzr, [<addr>] Modify the asm constaints for __put_mem_asm() to permit the use of the zero register for the value. There should be no functional change as a result of this patch. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Robin Murphy <robin.murphy@arm.com> Cc: Will Deacon <will@kernel.org> --- arch/arm64/include/asm/uaccess.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)