* Re: [PATCH] export.h: fix section name for CONFIG_TRIM_UNUSED_KSYMS for Clang
2020-09-29 19:07 [PATCH] export.h: fix section name for CONFIG_TRIM_UNUSED_KSYMS for Clang Nick Desaulniers
@ 2020-09-29 23:44 ` Kees Cook
2020-09-30 16:26 ` Nathan Chancellor
2020-09-30 16:43 ` Sedat Dilek
2 siblings, 0 replies; 4+ messages in thread
From: Kees Cook @ 2020-09-29 23:44 UTC (permalink / raw)
To: Nick Desaulniers
Cc: Andrew Morton, kbuild test robot, Nathan Chancellor,
Masahiro Yamada, Matthias Maennich, Jessica Yu,
Greg Kroah-Hartman, Will Deacon, linux-kernel, clang-built-linux
On Tue, Sep 29, 2020 at 12:07:00PM -0700, Nick Desaulniers wrote:
> When enabling CONFIG_TRIM_UNUSED_KSYMS, the linker will warn about the
> orphan sections:
> (".discard.ksym") is being placed in '".discard.ksym"'
> repeatedly when linking vmlinux. This is because the stringification
> operator, `#`, in the preprocessor escapes strings. GCC and Clang
> differ in how they treat section names that contain \".
>
> The portable solution is to not use a string literal with the
> preprocessor stringification operator.
>
> Link: https://bugs.llvm.org/show_bug.cgi?id=42950
> Link: https://github.com/ClangBuiltLinux/linux/issues/1166
> Fixes: commit bbda5ec671d3 ("kbuild: simplify dependency generation for CONFIG_TRIM_UNUSED_KSYMS")
> Reported-by: kbuild test robot <lkp@intel.com>
> Suggested-by: Kees Cook <keescook@chromium.org>
> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Do these other cases need fixing too?
arch/arm64/mm/mmu.c:u64 __section(".mmuoff.data.write") vabits_actual;
include/linux/srcutree.h: __section("___srcu_struct_ptrs") = &name
-Kees
> ---
> include/linux/export.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/export.h b/include/linux/export.h
> index fceb5e855717..8933ff6ad23a 100644
> --- a/include/linux/export.h
> +++ b/include/linux/export.h
> @@ -130,7 +130,7 @@ struct kernel_symbol {
> * discarded in the final link stage.
> */
> #define __ksym_marker(sym) \
> - static int __ksym_marker_##sym[0] __section(".discard.ksym") __used
> + static int __ksym_marker_##sym[0] __section(.discard.ksym) __used
>
> #define __EXPORT_SYMBOL(sym, sec, ns) \
> __ksym_marker(sym); \
> --
> 2.28.0.709.gb0816b6eb0-goog
>
--
Kees Cook
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] export.h: fix section name for CONFIG_TRIM_UNUSED_KSYMS for Clang
2020-09-29 19:07 [PATCH] export.h: fix section name for CONFIG_TRIM_UNUSED_KSYMS for Clang Nick Desaulniers
2020-09-29 23:44 ` Kees Cook
@ 2020-09-30 16:26 ` Nathan Chancellor
2020-09-30 16:43 ` Sedat Dilek
2 siblings, 0 replies; 4+ messages in thread
From: Nathan Chancellor @ 2020-09-30 16:26 UTC (permalink / raw)
To: Nick Desaulniers
Cc: Andrew Morton, kbuild test robot, Kees Cook, Masahiro Yamada,
Matthias Maennich, Jessica Yu, Greg Kroah-Hartman, Will Deacon,
linux-kernel, clang-built-linux
On Tue, Sep 29, 2020 at 12:07:00PM -0700, Nick Desaulniers wrote:
> When enabling CONFIG_TRIM_UNUSED_KSYMS, the linker will warn about the
> orphan sections:
> (".discard.ksym") is being placed in '".discard.ksym"'
> repeatedly when linking vmlinux. This is because the stringification
> operator, `#`, in the preprocessor escapes strings. GCC and Clang
> differ in how they treat section names that contain \".
>
> The portable solution is to not use a string literal with the
> preprocessor stringification operator.
>
> Link: https://bugs.llvm.org/show_bug.cgi?id=42950
> Link: https://github.com/ClangBuiltLinux/linux/issues/1166
> Fixes: commit bbda5ec671d3 ("kbuild: simplify dependency generation for CONFIG_TRIM_UNUSED_KSYMS")
> Reported-by: kbuild test robot <lkp@intel.com>
> Suggested-by: Kees Cook <keescook@chromium.org>
> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
> ---
> include/linux/export.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/export.h b/include/linux/export.h
> index fceb5e855717..8933ff6ad23a 100644
> --- a/include/linux/export.h
> +++ b/include/linux/export.h
> @@ -130,7 +130,7 @@ struct kernel_symbol {
> * discarded in the final link stage.
> */
> #define __ksym_marker(sym) \
> - static int __ksym_marker_##sym[0] __section(".discard.ksym") __used
> + static int __ksym_marker_##sym[0] __section(.discard.ksym) __used
>
> #define __EXPORT_SYMBOL(sym, sec, ns) \
> __ksym_marker(sym); \
> --
> 2.28.0.709.gb0816b6eb0-goog
>
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] export.h: fix section name for CONFIG_TRIM_UNUSED_KSYMS for Clang
2020-09-29 19:07 [PATCH] export.h: fix section name for CONFIG_TRIM_UNUSED_KSYMS for Clang Nick Desaulniers
2020-09-29 23:44 ` Kees Cook
2020-09-30 16:26 ` Nathan Chancellor
@ 2020-09-30 16:43 ` Sedat Dilek
2 siblings, 0 replies; 4+ messages in thread
From: Sedat Dilek @ 2020-09-30 16:43 UTC (permalink / raw)
To: Nick Desaulniers
Cc: Andrew Morton, kbuild test robot, Kees Cook, Nathan Chancellor,
Masahiro Yamada, Matthias Maennich, Jessica Yu,
Greg Kroah-Hartman, Will Deacon, linux-kernel,
Clang-Built-Linux ML
On Tue, Sep 29, 2020 at 9:07 PM 'Nick Desaulniers' via Clang Built
Linux <clang-built-linux@googlegroups.com> wrote:
>
> When enabling CONFIG_TRIM_UNUSED_KSYMS, the linker will warn about the
> orphan sections:
> (".discard.ksym") is being placed in '".discard.ksym"'
> repeatedly when linking vmlinux. This is because the stringification
> operator, `#`, in the preprocessor escapes strings. GCC and Clang
> differ in how they treat section names that contain \".
>
> The portable solution is to not use a string literal with the
> preprocessor stringification operator.
>
> Link: https://bugs.llvm.org/show_bug.cgi?id=42950
> Link: https://github.com/ClangBuiltLinux/linux/issues/1166
> Fixes: commit bbda5ec671d3 ("kbuild: simplify dependency generation for CONFIG_TRIM_UNUSED_KSYMS")
> Reported-by: kbuild test robot <lkp@intel.com>
> Suggested-by: Kees Cook <keescook@chromium.org>
> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
"The return of escaped section names" - soon in your cinema?
Thanks Nick for catching this.
Reviewed-by: Sedat Dilek <sedat.dilek@gmail.com>
- Sedat -
> ---
> include/linux/export.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/export.h b/include/linux/export.h
> index fceb5e855717..8933ff6ad23a 100644
> --- a/include/linux/export.h
> +++ b/include/linux/export.h
> @@ -130,7 +130,7 @@ struct kernel_symbol {
> * discarded in the final link stage.
> */
> #define __ksym_marker(sym) \
> - static int __ksym_marker_##sym[0] __section(".discard.ksym") __used
> + static int __ksym_marker_##sym[0] __section(.discard.ksym) __used
>
> #define __EXPORT_SYMBOL(sym, sec, ns) \
> __ksym_marker(sym); \
> --
> 2.28.0.709.gb0816b6eb0-goog
>
> --
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^ permalink raw reply [flat|nested] 4+ messages in thread