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Message-ID: <CAK7LNARKPGTbYdM5LxWD=_H6erPwxwb7XjTBBse3w28Yeb08vg@mail.gmail.com>
Date: Thu, 7 Nov 2024 01:39:09 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: linux-kbuild@...r.kernel.org
Cc: Nicholas Piggin <npiggin@...il.com>, 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: Re: [PATCH 2/2] Rename .data.once to .data..once to fix resetting WARN*_ONCE
On Thu, Nov 7, 2024 at 1:15 AM Masahiro Yamada <masahiroy@...nel.org> wrote:
>
> 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
This is a copy-paste error.
s/.data.unlikely/.data.once/
> .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
>
--
Best Regards
Masahiro Yamada
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