Re: objtool segfault with ORC unwinder enabled

Markus
2018-01-04T18:25:24Z

On Thursday, 4 January 2018 18:32:03 CET Josh Poimboeuf wrote:
> On Thu, Jan 04, 2018 at 05:56:30PM +0100, Markus wrote:
> > On Thursday, 4 January 2018 16:46:13 CET Josh Poimboeuf wrote:
> > > I don't see anything unusual there. Are there any Gentoo patches
> > > against either the kernel or GCC which would strip unused symbols?
> >
> > The kernel is the vanilla kernel. (4.14.11 and also 4.15-rc6)
> > Its not a gentoo specific gcc patch. (Then every gentoo user would be
> > affected?)
> >
> > But I enabled ld.gold as default linker like 5 years ago. Never had a
> > problem with this.
> >
> > Is ld.gold supposed to fail here?
> >
> > I switched back to ld.bfd and it seems to work.
>
> Ah, that explains it. With CONFIG_MODVERSIONS, the linker does some
> work after gcc, but before objtool. Can you try this patch? (Note this
> isn't the final patch, as this breaks the CONFIG_MODVERSIONS=n case.)
>
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index cb8997ed0149..3cf3cc6077ea 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -270,7 +270,7 @@ endif
> # 'OBJECT_FILES_NON_STANDARD_foo.o := 'n': override directory skip for a
> file cmd_objtool = $(if $(patsubst y%,, \
> $(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$
(OBJECT_FILES_NON_STANDARD)n)
> , \ - $(__objtool_obj) $(objtool_args) "$(@)";)
> + $(__objtool_obj) $(objtool_args) "$(@D)/.tmp_$(@F)";)
> objtool_obj = $(if $(patsubst y%,, \
> $(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$
(OBJECT_FILES_NON_STANDARD)n)
> , \ $(__objtool_obj))
> @@ -286,16 +286,16 @@ objtool_dep = $(objtool_obj) \
> define rule_cc_o_c
> $(call echo-cmd,checksrc) $(cmd_checksrc) \
> $(call cmd_and_fixdep,cc_o_c) \
> + $(call echo-cmd,objtool) $(cmd_objtool) \
> $(cmd_modversions_c) \
> $(cmd_checkdoc) \
> - $(call echo-cmd,objtool) $(cmd_objtool) \
> $(call echo-cmd,record_mcount) $(cmd_record_mcount)
> endef
>
> define rule_as_o_S
> $(call cmd_and_fixdep,as_o_S) \
> - $(cmd_modversions_S) \
> - $(call echo-cmd,objtool) $(cmd_objtool)
> + $(call echo-cmd,objtool) $(cmd_objtool) \
> + $(cmd_modversions_S)
> endef
>
> # List module undefined symbols (or empty line if not enabled)

With that patch the kernel is building with ld.gold.

BR,
Markus