linux-kernel - Re: [PATCH v3 2/9] vmlinux.lds.h: Add .symtab, .strtab, and .shstrtab to STABS

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Message-ID: <20200624153930.GA1337895@rani.riverdale.lan>
Date:   Wed, 24 Jun 2020 11:39:30 -0400
From:   Arvind Sankar <nivedita@...m.mit.edu>
To:     Kees Cook <keescook@...omium.org>
Cc:     Will Deacon <will@...nel.org>, Fangrui Song <maskray@...gle.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Mark Rutland <mark.rutland@....com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Peter Collingbourne <pcc@...gle.com>,
        James Morse <james.morse@....com>,
        Borislav Petkov <bp@...e.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Russell King <linux@...linux.org.uk>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Arvind Sankar <nivedita@...m.mit.edu>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        Arnd Bergmann <arnd@...db.de>, x86@...nel.org,
        clang-built-linux@...glegroups.com, linux-arch@...r.kernel.org,
        linux-efi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/9] vmlinux.lds.h: Add .symtab, .strtab, and
 .shstrtab to STABS_DEBUG

On Tue, Jun 23, 2020 at 06:49:33PM -0700, Kees Cook wrote:
> When linking vmlinux with LLD, the synthetic sections .symtab, .strtab,
> and .shstrtab are listed as orphaned. Add them to the STABS_DEBUG section
> so there will be no warnings when --orphan-handling=warn is used more
> widely. (They are added above comment as it is the more common

Nit 1: is "after .comment" better than "above comment"? It's above in the
sense of higher file offset, but it's below in readelf output.
Nit 2: These aren't actually debugging sections, no? Is it better to add
a new macro for it, and is there any plan to stop LLD from warning about
them?

> order[1].)
> 
> ld.lld: warning: <internal>:(.symtab) is being placed in '.symtab'
> ld.lld: warning: <internal>:(.shstrtab) is being placed in '.shstrtab'
> ld.lld: warning: <internal>:(.strtab) is being placed in '.strtab'
> 
> [1] https://lore.kernel.org/lkml/20200622224928.o2a7jkq33guxfci4@google.com/
> 
> Reported-by: Fangrui Song <maskray@...gle.com>
> Reviewed-by: Fangrui Song <maskray@...gle.com>
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
>  include/asm-generic/vmlinux.lds.h | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
> index 1248a206be8d..8e71757f485b 100644
> --- a/include/asm-generic/vmlinux.lds.h
> +++ b/include/asm-generic/vmlinux.lds.h
> @@ -792,7 +792,10 @@
>  		.stab.exclstr 0 : { *(.stab.exclstr) }			\
>  		.stab.index 0 : { *(.stab.index) }			\
>  		.stab.indexstr 0 : { *(.stab.indexstr) }		\
> -		.comment 0 : { *(.comment) }
> +		.comment 0 : { *(.comment) }				\
> +		.symtab 0 : { *(.symtab) }				\
> +		.strtab 0 : { *(.strtab) }				\
> +		.shstrtab 0 : { *(.shstrtab) }
>  
>  #ifdef CONFIG_GENERIC_BUG
>  #define BUG_TABLE							\
> -- 
> 2.25.1
>