Re: [RFC 03/13] objtool: Disassemble code with libopcodes instead of running objdump

[Alexandre Chartre]

On 6/11/25 14:23, Peter Zijlstra wrote:
> On Fri, Jun 06, 2025 at 05:34:30PM +0200, Alexandre Chartre wrote:
> > objtool executes the objdump command to disassemble code. Use libopcodes
> > instead to have more control about the disassembly scope and output.
> >
> > Signed-off-by: Alexandre Chartre <alexandre.chartre@xxxxxxxxxx>
> > ---
> >   tools/objtool/Makefile                  |   2 +-
> >   tools/objtool/arch/loongarch/decode.c   |   6 +
> >   tools/objtool/arch/powerpc/decode.c     |   6 +
> >   tools/objtool/arch/x86/decode.c         |   7 +
> >   tools/objtool/check.c                   |   4 +-
> >   tools/objtool/disas.c                   | 186 +++++++++++++++---------
> >   tools/objtool/include/objtool/arch.h    |   5 +
> >   tools/objtool/include/objtool/check.h   |   5 +
> >   tools/objtool/include/objtool/objtool.h |   4 +
> >   9 files changed, 154 insertions(+), 71 deletions(-)
> >
> > diff --git a/tools/objtool/Makefile b/tools/objtool/Makefile
> > index 8c20361dd100..00350fc7c662 100644
> > --- a/tools/objtool/Makefile
> > +++ b/tools/objtool/Makefile
> > @@ -34,7 +34,7 @@ INCLUDES := -I$(srctree)/tools/include \
> >   # is passed here to match a legacy behavior.
> >   WARNINGS := $(EXTRA_WARNINGS) -Wno-switch-default -Wno-switch-enum -Wno-packed -Wno-nested-externs
> >   OBJTOOL_CFLAGS := -Werror $(WARNINGS) $(KBUILD_HOSTCFLAGS) -g $(INCLUDES) $(LIBELF_FLAGS)
> > -OBJTOOL_LDFLAGS := $(LIBELF_LIBS) $(LIBSUBCMD) $(KBUILD_HOSTLDFLAGS)
> > +OBJTOOL_LDFLAGS := $(LIBELF_LIBS) $(LIBSUBCMD) $(KBUILD_HOSTLDFLAGS) -lopcodes
>
> Would it be possible to make this optional? Such that when people do not
> have libopcodes installed they can still build the kernel.
>
> Or is libopcodes a mandatory part of any binutils installation?

I guess that libopcodes is mandatory because it is used by as (and also objdump).
But I can check if it is effectively present anyway.

alex.