linux-kernel - [PATCH v3 04/14] um: prefer __section from compiler

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Message-Id: <20190828225535.49592-5-ndesaulniers@google.com>
Date:   Wed, 28 Aug 2019 15:55:25 -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 04/14] um: 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
Reported-by: Sedat Dilek <sedat.dilek@...il.com>
Suggested-by: Josh Poimboeuf <jpoimboe@...hat.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>
---
 arch/um/kernel/um_arch.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/um/kernel/um_arch.c b/arch/um/kernel/um_arch.c
index a818ccef30ca..18e0287dd97e 100644
--- a/arch/um/kernel/um_arch.c
+++ b/arch/um/kernel/um_arch.c
@@ -52,9 +52,9 @@ struct cpuinfo_um boot_cpu_data = {
 	.ipi_pipe		= { -1, -1 }
 };
 
-union thread_union cpu0_irqstack
-	__attribute__((__section__(".data..init_irqstack"))) =
-		{ .thread_info = INIT_THREAD_INFO(init_task) };
+union thread_union cpu0_irqstack __section(.data..init_irqstack) = {
+	.thread_info = INIT_THREAD_INFO(init_task)
+};
 
 /* Changed in setup_arch, which is called in early boot */
 static char host_info[(__NEW_UTS_LEN + 1) * 5];
-- 
2.23.0.187.g17f5b7556c-goog