linux-kernel - [PATCH v2] x86/lib: Do not use local symbols with SYM_CODE_START

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Message-Id: <20230525184244.2311-1-namit@vmware.com>
Date:   Thu, 25 May 2023 11:42:44 -0700
From:   Nadav Amit <nadav.amit@...il.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, Nadav Amit <namit@...are.com>
Subject: [PATCH v2] x86/lib: Do not use local symbols with SYM_CODE_START_LOCAL()

From: Nadav Amit <namit@...are.com>

When SYM_CODE_START_LOCAL() is used, the symbols are local but need to
be preserved in the object. However, using the ".L" label prefix does
not retain the symbol in the object.

It is beneficial to be able to map instruction pointers back to symbols,
for instance for profiling. Otherwise, there are code addresses that do
not map back to any symbol.  Consequently, the ".L" label prefix should
not be used when SYM_CODE_START_LOCAL() is used.

Few symbols, such as .Lbad_put_user_clac and currently have both the
SYM_CODE_START_LOCAL() invocation and the ".L" prefix.  This commit
removes the ".L" prefix from these symbols.

No functional change, other then emitting these symbols into the object,
is intended.

Signed-off-by: Nadav Amit <namit@...are.com>

---

v1 -> v2:
* Rebase on 6.4 (the affected symbols have changed)
---
 arch/x86/lib/getuser.S | 32 ++++++++++++++++----------------
 arch/x86/lib/putuser.S | 24 ++++++++++++------------
 2 files changed, 28 insertions(+), 28 deletions(-)

diff --git a/arch/x86/lib/getuser.S b/arch/x86/lib/getuser.S
index b64a2bd1a1ef..d98a80e0cdaf 100644
--- a/arch/x86/lib/getuser.S
+++ b/arch/x86/lib/getuser.S
@@ -143,43 +143,43 @@ SYM_FUNC_END(__get_user_nocheck_8)
 EXPORT_SYMBOL(__get_user_nocheck_8)
 
 
-SYM_CODE_START_LOCAL(.Lbad_get_user_clac)
+SYM_CODE_START_LOCAL(bad_get_user_clac)
 	ASM_CLAC
 .Lbad_get_user:
 	xor %edx,%edx
 	mov $(-EFAULT),%_ASM_AX
 	RET
-SYM_CODE_END(.Lbad_get_user_clac)
+SYM_CODE_END(bad_get_user_clac)
 
 #ifdef CONFIG_X86_32
-SYM_CODE_START_LOCAL(.Lbad_get_user_8_clac)
+SYM_CODE_START_LOCAL(bad_get_user_8_clac)
 	ASM_CLAC
 bad_get_user_8:
 	xor %edx,%edx
 	xor %ecx,%ecx
 	mov $(-EFAULT),%_ASM_AX
 	RET
-SYM_CODE_END(.Lbad_get_user_8_clac)
+SYM_CODE_END(bad_get_user_8_clac)
 #endif
 
 /* get_user */
-	_ASM_EXTABLE(1b, .Lbad_get_user_clac)
-	_ASM_EXTABLE(2b, .Lbad_get_user_clac)
-	_ASM_EXTABLE(3b, .Lbad_get_user_clac)
+	_ASM_EXTABLE(1b, bad_get_user_clac)
+	_ASM_EXTABLE(2b, bad_get_user_clac)
+	_ASM_EXTABLE(3b, bad_get_user_clac)
 #ifdef CONFIG_X86_64
-	_ASM_EXTABLE(4b, .Lbad_get_user_clac)
+	_ASM_EXTABLE(4b, bad_get_user_clac)
 #else
-	_ASM_EXTABLE(4b, .Lbad_get_user_8_clac)
-	_ASM_EXTABLE(5b, .Lbad_get_user_8_clac)
+	_ASM_EXTABLE(4b, bad_get_user_8_clac)
+	_ASM_EXTABLE(5b, bad_get_user_8_clac)
 #endif
 
 /* __get_user */
-	_ASM_EXTABLE(6b, .Lbad_get_user_clac)
-	_ASM_EXTABLE(7b, .Lbad_get_user_clac)
-	_ASM_EXTABLE(8b, .Lbad_get_user_clac)
+	_ASM_EXTABLE(6b, bad_get_user_clac)
+	_ASM_EXTABLE(7b, bad_get_user_clac)
+	_ASM_EXTABLE(8b, bad_get_user_clac)
 #ifdef CONFIG_X86_64
-	_ASM_EXTABLE(9b, .Lbad_get_user_clac)
+	_ASM_EXTABLE(9b, bad_get_user_clac)
 #else
-	_ASM_EXTABLE(9b, .Lbad_get_user_8_clac)
-	_ASM_EXTABLE(10b, .Lbad_get_user_8_clac)
+	_ASM_EXTABLE(9b, bad_get_user_8_clac)
+	_ASM_EXTABLE(10b, bad_get_user_8_clac)
 #endif
diff --git a/arch/x86/lib/putuser.S b/arch/x86/lib/putuser.S
index 3062d09a776d..f0c80e07229d 100644
--- a/arch/x86/lib/putuser.S
+++ b/arch/x86/lib/putuser.S
@@ -131,22 +131,22 @@ SYM_FUNC_START(__put_user_nocheck_8)
 SYM_FUNC_END(__put_user_nocheck_8)
 EXPORT_SYMBOL(__put_user_nocheck_8)
 
-SYM_CODE_START_LOCAL(.Lbad_put_user_clac)
+SYM_CODE_START_LOCAL(bad_put_user_clac)
 	ASM_CLAC
 .Lbad_put_user:
 	movl $-EFAULT,%ecx
 	RET
-SYM_CODE_END(.Lbad_put_user_clac)
+SYM_CODE_END(bad_put_user_clac)
 
-	_ASM_EXTABLE(1b, .Lbad_put_user_clac)
-	_ASM_EXTABLE(2b, .Lbad_put_user_clac)
-	_ASM_EXTABLE(3b, .Lbad_put_user_clac)
-	_ASM_EXTABLE(4b, .Lbad_put_user_clac)
-	_ASM_EXTABLE(5b, .Lbad_put_user_clac)
-	_ASM_EXTABLE(6b, .Lbad_put_user_clac)
-	_ASM_EXTABLE(7b, .Lbad_put_user_clac)
-	_ASM_EXTABLE(9b, .Lbad_put_user_clac)
+	_ASM_EXTABLE(1b, bad_put_user_clac)
+	_ASM_EXTABLE(2b, bad_put_user_clac)
+	_ASM_EXTABLE(3b, bad_put_user_clac)
+	_ASM_EXTABLE(4b, bad_put_user_clac)
+	_ASM_EXTABLE(5b, bad_put_user_clac)
+	_ASM_EXTABLE(6b, bad_put_user_clac)
+	_ASM_EXTABLE(7b, bad_put_user_clac)
+	_ASM_EXTABLE(9b, bad_put_user_clac)
 #ifdef CONFIG_X86_32
-	_ASM_EXTABLE(8b, .Lbad_put_user_clac)
-	_ASM_EXTABLE(10b, .Lbad_put_user_clac)
+	_ASM_EXTABLE(8b, bad_put_user_clac)
+	_ASM_EXTABLE(10b, bad_put_user_clac)
 #endif
-- 
2.25.1