Re: [PATCH v6 03/30] objtool: Disassemble code with libopcodes instead of running objdump

[David Laight <david.laight.linux@gmail.com>]

On Wed, 26 Nov 2025 10:00:36 +0100
Alexandre Chartre <alexandre.chartre@oracle.com> wrote:

> On 11/25/25 19:16, Nathan Chancellor wrote:
> > Hi Alexandre,
> > 
> > On Fri, Nov 21, 2025 at 10:53:13AM +0100, Alexandre Chartre wrote:  
> >> objtool executes the objdump command to disassemble code. Use libopcodes
> >> instead to have more control about the disassembly scope and output.
> >> If libopcodes is not present then objtool is built without disassembly
> >> support.
> >>
> >> Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>  
> > ...  
> >> diff --git a/tools/objtool/include/objtool/arch.h b/tools/objtool/include/objtool/arch.h
> >> index d89f8b5ec14e3..18c0e69ee6170 100644
> >> --- a/tools/objtool/include/objtool/arch.h
> >> +++ b/tools/objtool/include/objtool/arch.h
> >> @@ -103,4 +103,13 @@ bool arch_absolute_reloc(struct elf *elf, struct reloc *reloc);
> >>   unsigned int arch_reloc_size(struct reloc *reloc);
> >>   unsigned long arch_jump_table_sym_offset(struct reloc *reloc, struct reloc *table);
> >>   
> >> +#ifdef DISAS
> >> +
> >> +#include <bfd.h>  
> > 
> > This include of bfd.h breaks the build for me:
> > 
> >    $ make -skj"$(nproc)" ARCH=x86_64 CROSS_COMPILE=x86_64-linux- clean defconfig bzImage
> >    In file included from tools/objtool/include/objtool/arch.h:108,
> >                     from check.c:14:
> >    /usr/include/bfd.h:35:2: error: #error config.h must be included before this header
> >       35 | #error config.h must be included before this header
> >          |  ^~~~~
> >    ...
> > 
> > where my bfd.h has:
> > 
> >    #ifndef __BFD_H_SEEN__
> >    #define __BFD_H_SEEN__
> > 
> >    /* PR 14072: Ensure that config.h is included first.  */
> >    #if !defined PACKAGE && !defined PACKAGE_VERSION
> >    #error config.h must be included before this header
> >    #endif  
> 
> This check is effectively present in the bfd.h file generated from the
> binutils source code. However it is not present in the bfd.h file provided
> by the binutils RPM. I think this explained why we haven't seen this issue
> so far.
> 
> For history, this was introduced in 2012 for bug 14072. Then there was
> complaints reported in bug 14243 and 15920. But it was decided not to
> remove this change, and the suggested fix was to define PACKAGE when
> including bfd.h.
> 
> https://sourceware.org/bugzilla/show_bug.cgi?id=14072
> https://sourceware.org/bugzilla/show_bug.cgi?id=14243
> https://sourceware.org/bugzilla/show_bug.cgi?id=15920
> 
> And Redhat has fixed the issue for the binutils RPM by removing this test:
> 
> https://sourceware.org/bugzilla/show_bug.cgi?id=14243
> 
> 
> > Something like this cures it for me but I am not sure if that is a
> > proper fix or not since I see config.h in my binutils build folder has
> > many other defines.
> > 
> > Cheers,
> > Nathan
> > 
> > diff --git a/tools/objtool/Makefile b/tools/objtool/Makefile
> > index df793ca6fc1a..96df4a73da23 100644
> > --- a/tools/objtool/Makefile
> > +++ b/tools/objtool/Makefile
> > @@ -87,7 +87,7 @@ BUILD_DISAS := n
> >   
> >   ifeq ($(feature-libbfd),1)
> >   	BUILD_DISAS := y
> > -	OBJTOOL_CFLAGS += -DDISAS
> > +	OBJTOOL_CFLAGS += -DDISAS -DPACKAGE="objtool-disas"
> >   	OBJTOOL_LDFLAGS += -lopcodes
> >   endif
> >     
> 
> This is the proper fix (as indicated in the binutils bugs), and this is
> what the other kernel tools using bfd.h (bpf and perf) do. I will create
> a patch with your suggestion.

ISTM that defining it just before including bfd.h is cleaner and more obvious.

	David

> 
> Thanks,
> 
> alex.
> 
>