linux-kernel - Re: [PATCH] gendwarfksyms: define __GENKSYMS_

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Message-ID: <CAMj1kXEqNALtjhHyj=4AY=C-mFpj_uCv1BuS5X=xdxarJ5Ekgw@mail.gmail.com>
Date: Thu, 20 Mar 2025 09:22:47 +0100
From: Ard Biesheuvel <ardb@...nel.org>
To: Ard Biesheuvel <ardb+git@...gle.com>
Cc: linux-kbuild@...r.kernel.org, brgerst@...il.com, x86@...nel.org, 
	masahiroy@...nel.org, nathan@...nel.org, linux-kernel@...r.kernel.org, 
	nogikh@...gle.com, Sami Tolvanen <samitolvanen@...gle.com>, 
	syzbot+06fd1a3613c50d36129e@...kaller.appspotmail.com
Subject: Re: [PATCH] gendwarfksyms: define __GENKSYMS__ when processing asm-protoypes.h

On Thu, 20 Mar 2025 at 08:08, Ard Biesheuvel <ardb+git@...gle.com> wrote:
>
> From: Ard Biesheuvel <ardb@...nel.org>
>
> Ensure that __GENKSYMS__ is #define'd when passing asm/asm-prototypes.h
> through the compiler to capture the exported symbols. This ensures that
> exported symbols such as __ref_stack_chk_guard on x86, which is declared
> conditionally, is visible to the tool.
>
> Otherwise, an error such as the below may be raised, breaking the build
> when CONFIG_GENDWARFKSYMS=y
>
>   <stdin>:4:15: error: use of undeclared identifier '__ref_stack_chk_guard'
>
> Cc: Sami Tolvanen <samitolvanen@...gle.com>
> Reported-by: syzbot+06fd1a3613c50d36129e@...kaller.appspotmail.com
> Signed-off-by: Ard Biesheuvel <ardb@...nel.org>

Tested-by: syzbot+06fd1a3613c50d36129e@...kaller.appspotmail.com

https://syzkaller.appspot.com/bug?extid=06fd1a3613c50d36129e

> ---
>  scripts/Makefile.build | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index 993708d11874..7855cdc4e763 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -305,6 +305,7 @@ $(obj)/%.rs: $(obj)/%.rs.S FORCE
>  getasmexports =                                                                \
>     { echo "\#include <linux/kernel.h>" ;                               \
>       echo "\#include <linux/string.h>" ;                               \
> +     echo "\#define  __GENKSYMS__" ;                                   \
>       echo "\#include <asm/asm-prototypes.h>" ;                         \
>       $(call getexportsymbols,EXPORT_SYMBOL(\1);) ; }
>
> --
> 2.49.0.rc1.451.g8f38331e32-goog
>