linux-kernel - [PATCH v3 09/14] powerpc: prefer __section and __printf from compiler

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Date:   Wed, 28 Aug 2019 15:55:30 -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 09/14] powerpc: prefer __section and __printf 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/powerpc/boot/main.c         | 3 +--
 arch/powerpc/boot/ps3.c          | 6 ++----
 arch/powerpc/include/asm/cache.h | 2 +-
 arch/powerpc/kernel/btext.c      | 2 +-
 4 files changed, 5 insertions(+), 8 deletions(-)

diff --git a/arch/powerpc/boot/main.c b/arch/powerpc/boot/main.c
index 102cc546444d..3ccc84e06fc4 100644
--- a/arch/powerpc/boot/main.c
+++ b/arch/powerpc/boot/main.c
@@ -150,8 +150,7 @@ static struct addr_range prep_initrd(struct addr_range vmlinux, void *chosen,
  * edit the command line passed to vmlinux (by setting /chosen/bootargs).
  * The buffer is put in it's own section so that tools may locate it easier.
  */
-static char cmdline[BOOT_COMMAND_LINE_SIZE]
-	__attribute__((__section__("__builtin_cmdline")));
+static char cmdline[BOOT_COMMAND_LINE_SIZE] __section(__builtin_cmdline);
 
 static void prep_cmdline(void *chosen)
 {
diff --git a/arch/powerpc/boot/ps3.c b/arch/powerpc/boot/ps3.c
index c52552a681c5..70b2ed82d2de 100644
--- a/arch/powerpc/boot/ps3.c
+++ b/arch/powerpc/boot/ps3.c
@@ -24,8 +24,7 @@ extern int lv1_get_repository_node_value(u64 in_1, u64 in_2, u64 in_3,
 #ifdef DEBUG
 #define DBG(fmt...) printf(fmt)
 #else
-static inline int __attribute__ ((format (printf, 1, 2))) DBG(
-	const char *fmt, ...) {return 0;}
+static inline int __printf(1, 2) DBG(const char *fmt, ...) { return 0; }
 #endif
 
 BSS_STACK(4096);
@@ -35,8 +34,7 @@ BSS_STACK(4096);
  * The buffer is put in it's own section so that tools may locate it easier.
  */
 
-static char cmdline[BOOT_COMMAND_LINE_SIZE]
-	__attribute__((__section__("__builtin_cmdline")));
+static char cmdline[BOOT_COMMAND_LINE_SIZE] __section(__builtin_cmdline);
 
 static void prep_cmdline(void *chosen)
 {
diff --git a/arch/powerpc/include/asm/cache.h b/arch/powerpc/include/asm/cache.h
index 45e3137ccd71..9114495855eb 100644
--- a/arch/powerpc/include/asm/cache.h
+++ b/arch/powerpc/include/asm/cache.h
@@ -91,7 +91,7 @@ static inline u32 l1_cache_bytes(void)
 	isync
 
 #else
-#define __read_mostly __attribute__((__section__(".data..read_mostly")))
+#define __read_mostly __section(.data..read_mostly)
 
 #ifdef CONFIG_PPC_BOOK3S_32
 extern long _get_L2CR(void);
diff --git a/arch/powerpc/kernel/btext.c b/arch/powerpc/kernel/btext.c
index 6dfceaa820e4..f57712a55815 100644
--- a/arch/powerpc/kernel/btext.c
+++ b/arch/powerpc/kernel/btext.c
@@ -26,7 +26,7 @@
 static void scrollscreen(void);
 #endif
 
-#define __force_data __attribute__((__section__(".data")))
+#define __force_data __section(.data)
 
 static int g_loc_X __force_data;
 static int g_loc_Y __force_data;
-- 
2.23.0.187.g17f5b7556c-goog