linux-kernel - [PATCH] gendwarfksyms: define __GENKSYMS_

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Message-ID: <20250320070746.101552-2-ardb+git@google.com>
Date: Thu, 20 Mar 2025 08:07:47 +0100
From: Ard Biesheuvel <ardb+git@...gle.com>
To: linux-kbuild@...r.kernel.org
Cc: brgerst@...il.com, x86@...nel.org, masahiroy@...nel.org, nathan@...nel.org, 
	linux-kernel@...r.kernel.org, nogikh@...gle.com, 
	Ard Biesheuvel <ardb@...nel.org>, Sami Tolvanen <samitolvanen@...gle.com>, 
	syzbot+06fd1a3613c50d36129e@...kaller.appspotmail.com
Subject: [PATCH] gendwarfksyms: define __GENKSYMS__ when processing asm-protoypes.h

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>
---
 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