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From: Jisheng Zhang <jszhang@kernel.org>
To: Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>
Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: [PATCH 2/4] riscv: uaccess: use input constraints for ptr of __put_user
Date: Tue, 25 Jun 2024 12:04:58 +0800	[thread overview]
Message-ID: <20240625040500.1788-3-jszhang@kernel.org> (raw)
In-Reply-To: <20240625040500.1788-1-jszhang@kernel.org>

I believe the output constraints "=m" is not necessary, because
the instruction itself is "write", we don't need the compiler
to "write" for us. So tell compiler we read from memory instead
of writing.

Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
---
 arch/riscv/include/asm/uaccess.h | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/arch/riscv/include/asm/uaccess.h b/arch/riscv/include/asm/uaccess.h
index 09d4ca37522c..84b084e388a7 100644
--- a/arch/riscv/include/asm/uaccess.h
+++ b/arch/riscv/include/asm/uaccess.h
@@ -186,11 +186,11 @@ do {								\
 	__typeof__(*(ptr)) __x = x;				\
 	__asm__ __volatile__ (					\
 		"1:\n"						\
-		"	" insn " %z2, %1\n"			\
+		"	" insn " %z1, %2\n"			\
 		"2:\n"						\
 		_ASM_EXTABLE_UACCESS_ERR(1b, 2b, %0)		\
-		: "+r" (err), "=m" (*(ptr))			\
-		: "rJ" (__x));					\
+		: "+r" (err)			\
+		: "rJ" (__x), "m"(*(ptr)));					\
 } while (0)
 
 #ifdef CONFIG_64BIT
@@ -203,16 +203,16 @@ do {								\
 	u64 __x = (__typeof__((x)-(x)))(x);			\
 	__asm__ __volatile__ (					\
 		"1:\n"						\
-		"	sw %z3, %1\n"				\
+		"	sw %z1, %3\n"				\
 		"2:\n"						\
-		"	sw %z4, %2\n"				\
+		"	sw %z2, %4\n"				\
 		"3:\n"						\
 		_ASM_EXTABLE_UACCESS_ERR(1b, 3b, %0)		\
 		_ASM_EXTABLE_UACCESS_ERR(2b, 3b, %0)		\
-		: "+r" (err),					\
-			"=m" (__ptr[__LSW]),			\
-			"=m" (__ptr[__MSW])			\
-		: "rJ" (__x), "rJ" (__x >> 32));		\
+		: "+r" (err)					\
+		: "rJ" (__x), "rJ" (__x >> 32),			\
+			"m" (__ptr[__LSW]),			\
+			"m" (__ptr[__MSW]));			\
 } while (0)
 #endif /* CONFIG_64BIT */
 
-- 
2.43.0


  parent reply	other threads:[~2024-06-25  4:19 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-06-25  4:04 [PATCH 0/4] riscv: uaccess: optimizations Jisheng Zhang
2024-06-25  4:04 ` [PATCH 1/4] riscv: implement user_access_begin and families Jisheng Zhang
2024-06-26 23:38   ` Cyril Bur
2024-06-25  4:04 ` Jisheng Zhang [this message]
2024-06-25  5:54   ` [PATCH 2/4] riscv: uaccess: use input constraints for ptr of __put_user Arnd Bergmann
2024-06-26 12:32     ` Jisheng Zhang
2024-06-26 12:49       ` Jisheng Zhang
2024-06-26 13:18         ` Jisheng Zhang
2024-06-26 13:35         ` Andreas Schwab
2024-06-26 13:54           ` Jisheng Zhang
2024-06-26 13:12   ` Andreas Schwab
2024-06-26 13:12     ` Jisheng Zhang
2024-06-26 14:25       ` Arnd Bergmann
2024-06-26 16:02         ` Jisheng Zhang
2024-06-27  6:46           ` Arnd Bergmann
2024-06-28 15:36         ` David Laight
2024-06-25  4:04 ` [PATCH 3/4] riscv: uaccess: use 'asm goto' for put_user() Jisheng Zhang
2024-07-05  2:22   ` kernel test robot
2024-07-06  0:02   ` kernel test robot
2024-06-25  4:05 ` [PATCH 4/4] riscv: uaccess: use 'asm goto output' for get_user Jisheng Zhang
2024-07-05  4:13   ` kernel test robot
2024-06-25  7:21 ` [PATCH 0/4] riscv: uaccess: optimizations Arnd Bergmann
2024-06-25 18:12   ` Linus Torvalds
2024-06-26 13:04     ` Jisheng Zhang
2024-06-30 16:59     ` Linus Torvalds
2024-07-05 11:25       ` Will Deacon
2024-07-05 17:58         ` Linus Torvalds
2024-07-08 13:52           ` Will Deacon
2024-07-08 15:30             ` Mark Rutland
2024-07-23 14:16               ` Will Deacon
2024-07-08 15:21           ` Mark Rutland
2024-07-24 22:57 ` Palmer Dabbelt

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