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From: Aditya Srivastava <yashsri421@gmail.com>
To: linux-kernel@vger.kernel.org
Cc: yashsri421@gmail.com, lukas.bulwahn@gmail.com,
	dwaipayanray1@gmail.com, broonie@kernel.org, joe@perches.com,
	ndesaulniers@google.com, jpoimboe@redhat.com,
	linux-kernel-mentees@lists.linuxfoundation.org,
	clang-built-linux@googlegroups.com
Subject: [PATCH v2] checkpatch: add warning for avoiding .L prefix symbols in assembly files
Date: Sat, 23 Jan 2021 20:44:05 +0530	[thread overview]
Message-ID: <20210123151405.26267-1-yashsri421@gmail.com> (raw)
In-Reply-To: <bd560a8e-7949-933a-e4a9-508cb42c2570@gmail.com>

objtool requires that all code must be contained in an ELF symbol.
Symbol names that have a '.L' prefix do not emit symbol table entries, as
they have special meaning for the assembler.

'.L' prefixed symbols can be used within a code region, but should be
avoided for denoting a range of code via 'SYM_*_START/END' annotations.

Add a new check to emit a warning on finding the usage of '.L' symbols
for '.S' files in arch/x86/entry/* and arch/x86/lib/*, if it denotes
range of code via SYM_*_START/END annotation pair.

Suggested-by: Mark Brown <broonie@kernel.org>
Link: https://groups.google.com/g/clang-built-linux/c/-drkmLgu-cU/m/4staOlf-CgAJ
Signed-off-by: Aditya Srivastava <yashsri421@gmail.com>
---
* Applies perfectly on next-20210122

Changes in v2:
- Reduce the check to only SYM_*_START/END lines
- Reduce the check for only .S files in arch/x86/entry/* and arch/x86/lib/* as suggested by Josh and Nick
- Modify commit message

 scripts/checkpatch.pl | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 7030c4d6d126..e36cdf96dfe3 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -3590,6 +3590,13 @@ sub process {
 			}
 		}
 
+# check for .L prefix local symbols in .S files
+		if ($realfile =~ m@^arch/x86/(?:entry|lib)/.*\.S$@ &&
+		    $line =~ /^\+\s*SYM_[A-Z]+_(?:START|END)(?:_[A-Z_]+)?\s*\(\s*\.L/) {
+			WARN("AVOID_L_PREFIX",
+			     "Avoid using '.L' prefixed local symbol names for denoting a range of code via 'SYM_*_START/END' annotations; see Documentation/asm-annotations.rst\n" . $herecurr);
+		}
+
 # check we are in a valid source file C or perl if not then ignore this hunk
 		next if ($realfile !~ /\.(h|c|pl|dtsi|dts)$/);
 
-- 
2.17.1


WARNING: multiple messages have this Message-ID (diff)
From: Aditya Srivastava <yashsri421@gmail.com>
To: linux-kernel@vger.kernel.org
Cc: yashsri421@gmail.com, dwaipayanray1@gmail.com,
	ndesaulniers@google.com, clang-built-linux@googlegroups.com,
	broonie@kernel.org, jpoimboe@redhat.com, joe@perches.com,
	linux-kernel-mentees@lists.linuxfoundation.org
Subject: [Linux-kernel-mentees] [PATCH v2] checkpatch: add warning for avoiding .L prefix symbols in assembly files
Date: Sat, 23 Jan 2021 20:44:05 +0530	[thread overview]
Message-ID: <20210123151405.26267-1-yashsri421@gmail.com> (raw)
In-Reply-To: <bd560a8e-7949-933a-e4a9-508cb42c2570@gmail.com>

objtool requires that all code must be contained in an ELF symbol.
Symbol names that have a '.L' prefix do not emit symbol table entries, as
they have special meaning for the assembler.

'.L' prefixed symbols can be used within a code region, but should be
avoided for denoting a range of code via 'SYM_*_START/END' annotations.

Add a new check to emit a warning on finding the usage of '.L' symbols
for '.S' files in arch/x86/entry/* and arch/x86/lib/*, if it denotes
range of code via SYM_*_START/END annotation pair.

Suggested-by: Mark Brown <broonie@kernel.org>
Link: https://groups.google.com/g/clang-built-linux/c/-drkmLgu-cU/m/4staOlf-CgAJ
Signed-off-by: Aditya Srivastava <yashsri421@gmail.com>
---
* Applies perfectly on next-20210122

Changes in v2:
- Reduce the check to only SYM_*_START/END lines
- Reduce the check for only .S files in arch/x86/entry/* and arch/x86/lib/* as suggested by Josh and Nick
- Modify commit message

 scripts/checkpatch.pl | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 7030c4d6d126..e36cdf96dfe3 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -3590,6 +3590,13 @@ sub process {
 			}
 		}
 
+# check for .L prefix local symbols in .S files
+		if ($realfile =~ m@^arch/x86/(?:entry|lib)/.*\.S$@ &&
+		    $line =~ /^\+\s*SYM_[A-Z]+_(?:START|END)(?:_[A-Z_]+)?\s*\(\s*\.L/) {
+			WARN("AVOID_L_PREFIX",
+			     "Avoid using '.L' prefixed local symbol names for denoting a range of code via 'SYM_*_START/END' annotations; see Documentation/asm-annotations.rst\n" . $herecurr);
+		}
+
 # check we are in a valid source file C or perl if not then ignore this hunk
 		next if ($realfile !~ /\.(h|c|pl|dtsi|dts)$/);
 
-- 
2.17.1

_______________________________________________
Linux-kernel-mentees mailing list
Linux-kernel-mentees@lists.linuxfoundation.org
https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees

  parent reply	other threads:[~2021-01-23 15:15 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-20  7:25 [PATCH] checkpatch: add warning for avoiding .L prefix symbols in assembly files Aditya Srivastava
2021-01-20  7:25 ` [Linux-kernel-mentees] " Aditya Srivastava
2021-01-20  9:21 ` Joe Perches
2021-01-20  9:21   ` [Linux-kernel-mentees] " Joe Perches
2021-01-20 12:53   ` Aditya
2021-01-20 12:53     ` [Linux-kernel-mentees] " Aditya
2021-01-20 18:43     ` Joe Perches
2021-01-20 18:43       ` [Linux-kernel-mentees] " Joe Perches
2021-01-20 18:57       ` Nick Desaulniers
2021-01-20 18:57         ` [Linux-kernel-mentees] " Nick Desaulniers via Linux-kernel-mentees
2021-01-20 22:59         ` Josh Poimboeuf
2021-01-20 22:59           ` [Linux-kernel-mentees] " Josh Poimboeuf
2021-01-22 13:18       ` Aditya
2021-01-22 13:18         ` [Linux-kernel-mentees] " Aditya
2021-01-22 19:10         ` Joe Perches
2021-01-22 19:10           ` [Linux-kernel-mentees] " Joe Perches
2021-01-22 20:13           ` Aditya
2021-01-22 20:13             ` [Linux-kernel-mentees] " Aditya
2021-01-22 20:36             ` Fāng-ruì Sòng
2021-01-22 20:36               ` [Linux-kernel-mentees] " Fāng-ruì Sòng via Linux-kernel-mentees
2021-01-23 15:14             ` Aditya Srivastava [this message]
2021-01-23 15:14               ` [Linux-kernel-mentees] [PATCH v2] " Aditya Srivastava
2021-01-23 17:21               ` Joe Perches
2021-01-23 17:21                 ` [Linux-kernel-mentees] " Joe Perches
2021-01-23 18:23                 ` Aditya
2021-01-23 18:23                   ` [Linux-kernel-mentees] " Aditya
2021-01-23 19:04                   ` [PATCH v3] " Aditya Srivastava
2021-01-23 19:04                     ` [Linux-kernel-mentees] " Aditya Srivastava
2021-01-23 21:01                     ` Joe Perches
2021-01-23 21:01                       ` [Linux-kernel-mentees] " Joe Perches
2021-01-25 18:15                       ` Nick Desaulniers
2021-01-25 18:15                         ` [Linux-kernel-mentees] " Nick Desaulniers via Linux-kernel-mentees

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