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From: Fangrui Song <maskray@google.com>
To: Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	 linux-arm-kernel@lists.infradead.org
Cc: Jisheng Zhang <jszhang@kernel.org>,
	Ard Biesheuvel <ardb@kernel.org>,
	llvm@lists.linux.dev,  linux-kernel@vger.kernel.org,
	Fangrui Song <maskray@google.com>
Subject: [PATCH] arm64: jump_label: use constraint "S" instead of "i"
Date: Tue, 30 Jan 2024 22:53:22 -0800	[thread overview]
Message-ID: <20240131065322.1126831-1-maskray@google.com> (raw)

The constraint "i" seems to be copied from x86 (and with a redundant
modifier "c"). It works with -fno-PIE but not with -fPIE/-fPIC in GCC's
aarch64 port.

The constraint "S", which denotes a symbol reference (e.g. function,
global variable) or label reference, is more appropriate, and has been
available in GCC since 2012 and in Clang since 7.0.

Signed-off-by: Fangrui Song <maskray@google.com>
Link: https://maskray.me/blog/2024-01-30-raw-symbol-names-in-inline-assembly
---
 arch/arm64/include/asm/jump_label.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/include/asm/jump_label.h b/arch/arm64/include/asm/jump_label.h
index 48ddc0f45d22..31862b3bb33d 100644
--- a/arch/arm64/include/asm/jump_label.h
+++ b/arch/arm64/include/asm/jump_label.h
@@ -23,9 +23,9 @@ static __always_inline bool arch_static_branch(struct static_key * const key,
 		 "	.pushsection	__jump_table, \"aw\"	\n\t"
 		 "	.align		3			\n\t"
 		 "	.long		1b - ., %l[l_yes] - .	\n\t"
-		 "	.quad		%c0 - .			\n\t"
+		 "	.quad		%0 - .			\n\t"
 		 "	.popsection				\n\t"
-		 :  :  "i"(&((char *)key)[branch]) :  : l_yes);
+		 :  :  "S"(&((char *)key)[branch]) :  : l_yes);
 
 	return false;
 l_yes:
@@ -40,9 +40,9 @@ static __always_inline bool arch_static_branch_jump(struct static_key * const ke
 		 "	.pushsection	__jump_table, \"aw\"	\n\t"
 		 "	.align		3			\n\t"
 		 "	.long		1b - ., %l[l_yes] - .	\n\t"
-		 "	.quad		%c0 - .			\n\t"
+		 "	.quad		%0 - .			\n\t"
 		 "	.popsection				\n\t"
-		 :  :  "i"(&((char *)key)[branch]) :  : l_yes);
+		 :  :  "S"(&((char *)key)[branch]) :  : l_yes);
 
 	return false;
 l_yes:
-- 
2.43.0.429.g432eaa2c6b-goog


WARNING: multiple messages have this Message-ID (diff)
From: Fangrui Song <maskray@google.com>
To: Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	 linux-arm-kernel@lists.infradead.org
Cc: Jisheng Zhang <jszhang@kernel.org>,
	Ard Biesheuvel <ardb@kernel.org>,
	llvm@lists.linux.dev,  linux-kernel@vger.kernel.org,
	Fangrui Song <maskray@google.com>
Subject: [PATCH] arm64: jump_label: use constraint "S" instead of "i"
Date: Tue, 30 Jan 2024 22:53:22 -0800	[thread overview]
Message-ID: <20240131065322.1126831-1-maskray@google.com> (raw)

The constraint "i" seems to be copied from x86 (and with a redundant
modifier "c"). It works with -fno-PIE but not with -fPIE/-fPIC in GCC's
aarch64 port.

The constraint "S", which denotes a symbol reference (e.g. function,
global variable) or label reference, is more appropriate, and has been
available in GCC since 2012 and in Clang since 7.0.

Signed-off-by: Fangrui Song <maskray@google.com>
Link: https://maskray.me/blog/2024-01-30-raw-symbol-names-in-inline-assembly
---
 arch/arm64/include/asm/jump_label.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/include/asm/jump_label.h b/arch/arm64/include/asm/jump_label.h
index 48ddc0f45d22..31862b3bb33d 100644
--- a/arch/arm64/include/asm/jump_label.h
+++ b/arch/arm64/include/asm/jump_label.h
@@ -23,9 +23,9 @@ static __always_inline bool arch_static_branch(struct static_key * const key,
 		 "	.pushsection	__jump_table, \"aw\"	\n\t"
 		 "	.align		3			\n\t"
 		 "	.long		1b - ., %l[l_yes] - .	\n\t"
-		 "	.quad		%c0 - .			\n\t"
+		 "	.quad		%0 - .			\n\t"
 		 "	.popsection				\n\t"
-		 :  :  "i"(&((char *)key)[branch]) :  : l_yes);
+		 :  :  "S"(&((char *)key)[branch]) :  : l_yes);
 
 	return false;
 l_yes:
@@ -40,9 +40,9 @@ static __always_inline bool arch_static_branch_jump(struct static_key * const ke
 		 "	.pushsection	__jump_table, \"aw\"	\n\t"
 		 "	.align		3			\n\t"
 		 "	.long		1b - ., %l[l_yes] - .	\n\t"
-		 "	.quad		%c0 - .			\n\t"
+		 "	.quad		%0 - .			\n\t"
 		 "	.popsection				\n\t"
-		 :  :  "i"(&((char *)key)[branch]) :  : l_yes);
+		 :  :  "S"(&((char *)key)[branch]) :  : l_yes);
 
 	return false;
 l_yes:
-- 
2.43.0.429.g432eaa2c6b-goog


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http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

             reply	other threads:[~2024-01-31  6:53 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-01-31  6:53 Fangrui Song [this message]
2024-01-31  6:53 ` [PATCH] arm64: jump_label: use constraint "S" instead of "i" Fangrui Song
2024-01-31  7:16 ` Ard Biesheuvel
2024-01-31  7:16   ` Ard Biesheuvel
2024-01-31 13:01   ` Dave Martin
2024-01-31 13:01     ` Dave Martin
2024-02-01  4:55     ` Fangrui Song
2024-02-01  4:55       ` Fangrui Song
2024-02-01  8:08       ` Ard Biesheuvel
2024-02-01  8:08         ` Ard Biesheuvel
2024-02-01  9:11         ` Fangrui Song
2024-02-01  9:11           ` Fangrui Song
2024-02-01 11:49           ` Dave Martin
2024-02-01 11:49             ` Dave Martin
2024-02-01 16:07             ` Ard Biesheuvel
2024-02-01 16:07               ` Ard Biesheuvel
2024-02-01 17:29               ` Dave Martin
2024-02-01 17:29                 ` Dave Martin
2024-02-01 20:56                 ` Fangrui Song
2024-02-01 20:56                   ` Fangrui Song
2024-02-01 21:23                   ` Ard Biesheuvel
2024-02-01 21:23                     ` Ard Biesheuvel
2024-02-01 22:12                     ` Fangrui Song
2024-02-01 22:12                       ` Fangrui Song
2024-02-02 15:42                       ` Dave Martin
2024-02-02 15:42                         ` Dave Martin
2024-02-02 22:28                         ` Fangrui Song
2024-02-02 22:28                           ` Fangrui Song

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