linux-kernel - Re: libelf-0.175 breaks objtool

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Date:   Tue, 7 Apr 2020 11:32:53 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: libelf-0.175 breaks objtool

On Tue, Apr 07, 2020 at 05:46:23PM +0200, Arnd Bergmann wrote:
> On Tue, Apr 7, 2020 at 12:31 AM Arnd Bergmann <arnd@...db.de> wrote:
> > On Tue, Apr 7, 2020 at 12:16 AM Josh Poimboeuf <jpoimboe@...hat.com> wrote:
> >
> > It's also odd that I only see the problem in two specific files:
> > arch/x86/realmode/rm/trampoline_64.o (in half of the randconfig builds)
> > and fs/xfs/xfs_trace.o  (in only one configuration so far).
> >
> > With this patch I can avoid the first one, which is unconditionally
> > built with -g (why?):
> >
> > --- a/arch/x86/realmode/rm/Makefile
> > +++ b/arch/x86/realmode/rm/Makefile
> > @@ -69,7 +69,7 @@ $(obj)/realmode.relocs: $(obj)/realmode.elf FORCE
> >  # ---------------------------------------------------------------------------
> >
> >  KBUILD_CFLAGS  := $(REALMODE_CFLAGS) -D_SETUP -D_WAKEUP \
> > -                  -I$(srctree)/arch/x86/boot
> > +                  -I$(srctree)/arch/x86/boot -gz=none
> >  KBUILD_AFLAGS  := $(KBUILD_CFLAGS) -D__ASSEMBLY__
> >  KBUILD_CFLAGS  += -fno-asynchronous-unwind-tables
> >  GCOV_PROFILE := n
> >
> > I'll look at the other one tomorrow.
> 
> I found where -g gets added in both cases, and adding -gz=none
> seems to address all randconfigs with CONFIG_DEBUG_INFO=n:
> 
> --- a/fs/xfs/Makefile
> +++ b/fs/xfs/Makefile
> @@ -7,7 +7,7 @@
>  ccflags-y += -I $(srctree)/$(src)              # needed for trace events
>  ccflags-y += -I $(srctree)/$(src)/libxfs
> 
> -ccflags-$(CONFIG_XFS_DEBUG) += -g
> +ccflags-$(CONFIG_XFS_DEBUG) += -g $(call cc-option,-gz=none)

Maybe they shouldn't have -g in the first place?

-- 
Josh