linux-kernel - Re: objtool segfault with ORC unwinder enabled

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Date:   Wed, 10 Jan 2018 22:25:51 -0600
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Markus <M4rkusXXL@....de>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: objtool segfault with ORC unwinder enabled

On Wed, Jan 10, 2018 at 10:13:00PM -0600, Josh Poimboeuf wrote:
> On Wed, Jan 10, 2018 at 06:14:56PM +0100, Markus wrote:
> > On Thursday, 4 January 2018 19:25:12 CET Markus wrote:
> > > 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.)
> > 
> > Any more final patch I should test?
> 
> Sorry, this fell off my radar.  I'll try to get a final patch soon.
> (But feel free to keep bugging me if I don't!)

Ok, this should be the final patch (no description yet though).  Want to
test it?

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index cb8997ed0149..6f0c0c409e67 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -265,12 +265,18 @@ else
 objtool_args += $(call cc-ifversion, -lt, 0405, --no-unreachable)
 endif
 
+ifdef CONFIG_MODVERSIONS
+objtool_o := $(@D)/.tmp_$(@F)
+else
+objtool_o := $(@)
+endif
+
 # 'OBJECT_FILES_NON_STANDARD := y': skip objtool checking for a directory
 # 'OBJECT_FILES_NON_STANDARD_foo.o := 'y': skip objtool checking for a file
 # '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) $(objtool_args) "$(objtool_o)";)
 objtool_obj = $(if $(patsubst y%,, \
 	$(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n), \
 	$(__objtool_obj))
@@ -286,16 +292,16 @@ 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)