linux-kernel - [PATCH v3 11/14] include/asm-generic: prefer __section from compiler

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Message-Id: <20190828225535.49592-12-ndesaulniers@google.com>
Date:   Wed, 28 Aug 2019 15:55:32 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     miguel.ojeda.sandonis@...il.com
Cc:     sedat.dilek@...il.com, will@...nel.org, jpoimboe@...hat.com,
        naveen.n.rao@...ux.vnet.ibm.com, davem@...emloft.net,
        paul.burton@...s.com, clang-built-linux@...glegroups.com,
        linux-kernel@...r.kernel.org,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: [PATCH v3 11/14] include/asm-generic: prefer __section from compiler_attributes.h

GCC unescapes escaped string section names while Clang does not. Because
__section uses the `#` stringification operator for the section name, it
doesn't need to be escaped.

Instead, we should:
1. Prefer __section(.section_name_no_quotes).
2. Only use __attribute__((__section__(".section"))) when creating the
section name via C preprocessor (see the definition of __define_initcall
in arch/um/include/shared/init.h).

This antipattern was found with:
$ grep -e __section\(\" -e __section__\(\" -r

See the discussions in:
Link: https://bugs.llvm.org/show_bug.cgi?id=42950
Link: https://marc.info/?l=linux-netdev&m=156412960619946&w=2
Link: https://github.com/ClangBuiltLinux/linux/issues/619
Acked-by: Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com>
Reported-by: Sedat Dilek <sedat.dilek@...il.com>
Suggested-by: Josh Poimboeuf <jpoimboe@...hat.com>
Tested-by: Sedat Dilek <sedat.dilek@...il.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>
---
 include/asm-generic/error-injection.h | 2 +-
 include/asm-generic/kprobes.h         | 5 ++---
 2 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/include/asm-generic/error-injection.h b/include/asm-generic/error-injection.h
index 95a159a4137f..a593a50b33e3 100644
--- a/include/asm-generic/error-injection.h
+++ b/include/asm-generic/error-injection.h
@@ -23,7 +23,7 @@ struct error_injection_entry {
  */
 #define ALLOW_ERROR_INJECTION(fname, _etype)				\
 static struct error_injection_entry __used				\
-	__attribute__((__section__("_error_injection_whitelist")))	\
+	__section(_error_injection_whitelist)				\
 	_eil_addr_##fname = {						\
 		.addr = (unsigned long)fname,				\
 		.etype = EI_ETYPE_##_etype,				\
diff --git a/include/asm-generic/kprobes.h b/include/asm-generic/kprobes.h
index 4a982089c95c..20d69719270f 100644
--- a/include/asm-generic/kprobes.h
+++ b/include/asm-generic/kprobes.h
@@ -9,12 +9,11 @@
  * by using this macro.
  */
 # define __NOKPROBE_SYMBOL(fname)				\
-static unsigned long __used					\
-	__attribute__((__section__("_kprobe_blacklist")))	\
+static unsigned long __used __section(_kprobe_blacklist)	\
 	_kbl_addr_##fname = (unsigned long)fname;
 # define NOKPROBE_SYMBOL(fname)	__NOKPROBE_SYMBOL(fname)
 /* Use this to forbid a kprobes attach on very low level functions */
-# define __kprobes	__attribute__((__section__(".kprobes.text")))
+# define __kprobes	__section(.kprobes.text)
 # define nokprobe_inline	__always_inline
 #else
 # define NOKPROBE_SYMBOL(fname)
-- 
2.23.0.187.g17f5b7556c-goog