On Thu, 20 Mar 2025 at 15:48, Sami Tolvanen <samitolvanen@xxxxxxxxxx> wrote:
>
> Hi Ard,
>
> On Thu, Mar 20, 2025 at 12:07 AM Ard Biesheuvel <ardb+git@xxxxxxxxxx> wrote:
> >
> > From: Ard Biesheuvel <ardb@xxxxxxxxxx>
> >
> > 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@xxxxxxxxxx>
> > Reported-by: syzbot+06fd1a3613c50d36129e@xxxxxxxxxxxxxxxxxxxxxxxxx
> > Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
> > ---
> > 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);) ; }
>
> This works with gendwarfksyms since __GENKSYMS__ is defined after the
> EXPORT_SYMBOL() definition, but I'm now getting warnings with
> genksyms:
>
> AS arch/x86/lib/clear_page_64.o
> <stdin>:3:10: warning: "__GENKSYMS__" redefined
> <command-line>: note: this is the location of the previous definition
>
Oops.
Do you think the fix below should be sufficient?
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -314,7 +314,7 @@
else
cmd_gensymtypes_S = \
$(getasmexports) | \
- $(CPP) -D__GENKSYMS__ $(c_flags) -xc - | $(genksyms)
+ $(CPP) $(c_flags) -xc - | $(genksyms)
endif # CONFIG_GENDWARFKSYMS
quiet_cmd_cpp_s_S = CPP $(quiet_modtag) $@
