From: Kees Cook <keescook@chromium.org>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
kbuild test robot <lkp@intel.com>,
Nathan Chancellor <natechancellor@gmail.com>,
Masahiro Yamada <yamada.masahiro@socionext.com>,
Matthias Maennich <maennich@google.com>,
Jessica Yu <jeyu@kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Will Deacon <will@kernel.org>,
linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com
Subject: Re: [PATCH] export.h: fix section name for CONFIG_TRIM_UNUSED_KSYMS for Clang
Date: Tue, 29 Sep 2020 16:44:25 -0700 [thread overview]
Message-ID: <202009291643.97AA3D46@keescook> (raw)
In-Reply-To: <20200929190701.398762-1-ndesaulniers@google.com>
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
next prev parent reply other threads:[~2020-09-29 23:44 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
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 [this message]
2020-09-30 16:26 ` Nathan Chancellor
2020-09-30 16:43 ` Sedat Dilek
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