linux-kernel - [PATCH] export.h: fix section name for CONFIG_TRIM_UNUSED

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Message-Id: <20200929190701.398762-1-ndesaulniers@google.com>
Date:   Tue, 29 Sep 2020 12:07:00 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Nick Desaulniers <ndesaulniers@...gle.com>,
        kbuild test robot <lkp@...el.com>,
        Kees Cook <keescook@...omium.org>,
        Nathan Chancellor <natechancellor@...il.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Matthias Maennich <maennich@...gle.com>,
        Jessica Yu <jeyu@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Will Deacon <will@...nel.org>, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com
Subject: [PATCH] export.h: fix section name for CONFIG_TRIM_UNUSED_KSYMS for Clang

When enabling CONFIG_TRIM_UNUSED_KSYMS, the linker will warn about the
orphan sections:
(".discard.ksym") is being placed in '".discard.ksym"'
repeatedly when linking vmlinux. This is because the stringification
operator, `#`, in the preprocessor escapes strings.  GCC and Clang
differ in how they treat section names that contain \".

The portable solution is to not use a string literal with the
preprocessor stringification operator.

Link: https://bugs.llvm.org/show_bug.cgi?id=42950
Link: https://github.com/ClangBuiltLinux/linux/issues/1166
Fixes: commit bbda5ec671d3 ("kbuild: simplify dependency generation for CONFIG_TRIM_UNUSED_KSYMS")
Reported-by: kbuild test robot <lkp@...el.com>
Suggested-by: Kees Cook <keescook@...omium.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>
---
 include/linux/export.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/export.h b/include/linux/export.h
index fceb5e855717..8933ff6ad23a 100644
--- a/include/linux/export.h
+++ b/include/linux/export.h
@@ -130,7 +130,7 @@ struct kernel_symbol {
  * discarded in the final link stage.
  */
 #define __ksym_marker(sym)	\
-	static int __ksym_marker_##sym[0] __section(".discard.ksym") __used
+	static int __ksym_marker_##sym[0] __section(.discard.ksym) __used
 
 #define __EXPORT_SYMBOL(sym, sec, ns)					\
 	__ksym_marker(sym);						\
-- 
2.28.0.709.gb0816b6eb0-goog