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Message-ID: <20241106161445.189399-2-masahiroy@kernel.org>
Date: Thu, 7 Nov 2024 01:14:41 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: linux-kbuild@...r.kernel.org
Cc: Nicholas Piggin <npiggin@...il.com>,
Masahiro Yamada <masahiroy@...nel.org>,
Andi Kleen <ak@...ux.intel.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Arnd Bergmann <arnd@...db.de>,
Bill Wendling <morbo@...gle.com>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Justin Stitt <justinstitt@...gle.com>,
Kees Cook <kees@...nel.org>,
Nathan Chancellor <nathan@...nel.org>,
Nick Desaulniers <ndesaulniers@...gle.com>,
Paolo Abeni <pabeni@...hat.com>,
Sami Tolvanen <samitolvanen@...gle.com>,
Simon Horman <horms@...nel.org>,
linux-arch@...r.kernel.org,
linux-kernel@...r.kernel.org,
linux-mm@...ck.org,
llvm@...ts.linux.dev,
netdev@...r.kernel.org
Subject: [PATCH 2/2] Rename .data.once to .data..once to fix resetting WARN*_ONCE
Commit b1fca27d384e ("kernel debug: support resetting WARN*_ONCE")
added support for clearing the state of once warnings. However,
it is not functional when CONFIG_LD_DEAD_CODE_DATA_ELIMINATION or
CONFIG_LTO_CLANG is enabled, because .data.unlikely matches the
.data.[0-9a-zA-Z_]* pattern in the DATA_MAIN macro.
Commit cb87481ee89d ("kbuild: linker script do not match C names unless
LD_DEAD_CODE_DATA_ELIMINATION is configured") was introduced to suppress
the issue for the default CONFIG_LD_DEAD_CODE_DATA_ELIMINATION=n case,
providing a minimal fix for stable backporting. We were aware this did
not address the issue for CONFIG_LD_DEAD_CODE_DATA_ELIMINATION=y. The
plan was to apply correct fixes and then revert cb87481ee89d. [1]
Seven years have passed since then, yet the #ifdef workaround remains in
place. Meanwhile, commit b1fca27d384e introduced the .data.once section,
and commit dc5723b02e52 ("kbuild: add support for Clang LTO") extended
the #ifdef.
Using a ".." separator in the section name fixes the issue for
CONFIG_LD_DEAD_CODE_DATA_ELIMINATION and CONFIG_LTO_CLANG.
[1]: https://lore.kernel.org/linux-kbuild/CAK7LNASck6BfdLnESxXUeECYL26yUDm0cwRZuM4gmaWUkxjL5g@mail.gmail.com/
Fixes: b1fca27d384e ("kernel debug: support resetting WARN*_ONCE")
Fixes: dc5723b02e52 ("kbuild: add support for Clang LTO")
Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
---
include/asm-generic/vmlinux.lds.h | 2 +-
include/linux/mmdebug.h | 6 +++---
include/linux/once.h | 4 ++--
include/linux/once_lite.h | 2 +-
include/net/net_debug.h | 2 +-
mm/internal.h | 2 +-
6 files changed, 9 insertions(+), 9 deletions(-)
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 3c9dc1fd094d..54504013c749 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -359,7 +359,7 @@ defined(CONFIG_AUTOFDO_CLANG) || defined(CONFIG_PROPELLER_CLANG)
*(.data..shared_aligned) /* percpu related */ \
*(.data..unlikely) \
__start_once = .; \
- *(.data.once) \
+ *(.data..once) \
__end_once = .; \
STRUCT_ALIGN(); \
*(__tracepoints) \
diff --git a/include/linux/mmdebug.h b/include/linux/mmdebug.h
index 39a7714605a7..d7cb1e5ecbda 100644
--- a/include/linux/mmdebug.h
+++ b/include/linux/mmdebug.h
@@ -46,7 +46,7 @@ void vma_iter_dump_tree(const struct vma_iterator *vmi);
} \
} while (0)
#define VM_WARN_ON_ONCE_PAGE(cond, page) ({ \
- static bool __section(".data.once") __warned; \
+ static bool __section(".data..once") __warned; \
int __ret_warn_once = !!(cond); \
\
if (unlikely(__ret_warn_once && !__warned)) { \
@@ -66,7 +66,7 @@ void vma_iter_dump_tree(const struct vma_iterator *vmi);
unlikely(__ret_warn); \
})
#define VM_WARN_ON_ONCE_FOLIO(cond, folio) ({ \
- static bool __section(".data.once") __warned; \
+ static bool __section(".data..once") __warned; \
int __ret_warn_once = !!(cond); \
\
if (unlikely(__ret_warn_once && !__warned)) { \
@@ -77,7 +77,7 @@ void vma_iter_dump_tree(const struct vma_iterator *vmi);
unlikely(__ret_warn_once); \
})
#define VM_WARN_ON_ONCE_MM(cond, mm) ({ \
- static bool __section(".data.once") __warned; \
+ static bool __section(".data..once") __warned; \
int __ret_warn_once = !!(cond); \
\
if (unlikely(__ret_warn_once && !__warned)) { \
diff --git a/include/linux/once.h b/include/linux/once.h
index bc714d414448..30346fcdc799 100644
--- a/include/linux/once.h
+++ b/include/linux/once.h
@@ -46,7 +46,7 @@ void __do_once_sleepable_done(bool *done, struct static_key_true *once_key,
#define DO_ONCE(func, ...) \
({ \
bool ___ret = false; \
- static bool __section(".data.once") ___done = false; \
+ static bool __section(".data..once") ___done = false; \
static DEFINE_STATIC_KEY_TRUE(___once_key); \
if (static_branch_unlikely(&___once_key)) { \
unsigned long ___flags; \
@@ -64,7 +64,7 @@ void __do_once_sleepable_done(bool *done, struct static_key_true *once_key,
#define DO_ONCE_SLEEPABLE(func, ...) \
({ \
bool ___ret = false; \
- static bool __section(".data.once") ___done = false; \
+ static bool __section(".data..once") ___done = false; \
static DEFINE_STATIC_KEY_TRUE(___once_key); \
if (static_branch_unlikely(&___once_key)) { \
___ret = __do_once_sleepable_start(&___done); \
diff --git a/include/linux/once_lite.h b/include/linux/once_lite.h
index b7bce4983638..27de7bc32a06 100644
--- a/include/linux/once_lite.h
+++ b/include/linux/once_lite.h
@@ -12,7 +12,7 @@
#define __ONCE_LITE_IF(condition) \
({ \
- static bool __section(".data.once") __already_done; \
+ static bool __section(".data..once") __already_done; \
bool __ret_cond = !!(condition); \
bool __ret_once = false; \
\
diff --git a/include/net/net_debug.h b/include/net/net_debug.h
index 1e74684cbbdb..4a79204c8d30 100644
--- a/include/net/net_debug.h
+++ b/include/net/net_debug.h
@@ -27,7 +27,7 @@ void netdev_info(const struct net_device *dev, const char *format, ...);
#define netdev_level_once(level, dev, fmt, ...) \
do { \
- static bool __section(".data.once") __print_once; \
+ static bool __section(".data..once") __print_once; \
\
if (!__print_once) { \
__print_once = true; \
diff --git a/mm/internal.h b/mm/internal.h
index 93083bbeeefa..a23f7b11b760 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -48,7 +48,7 @@ struct folio_batch;
* when we specify __GFP_NOWARN.
*/
#define WARN_ON_ONCE_GFP(cond, gfp) ({ \
- static bool __section(".data.once") __warned; \
+ static bool __section(".data..once") __warned; \
int __ret_warn_once = !!(cond); \
\
if (unlikely(!(gfp & __GFP_NOWARN) && __ret_warn_once && !__warned)) { \
--
2.43.0
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