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

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Message-ID: <20180111193810.27aguyr6viurhijm@treble>
Date:   Thu, 11 Jan 2018 13:38:10 -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 Thu, Jan 11, 2018 at 07:52:00PM +0100, Markus wrote:
> On Thursday, 11 January 2018 19:20:57 CET Josh Poimboeuf wrote:
> > On Thu, Jan 11, 2018 at 07:11:03PM +0100, Markus wrote:
> > > On Thursday, 11 January 2018 05:25:51 CET Josh Poimboeuf wrote:
> > > > 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?
> > > 
> > > Tried to apply to 4.14.13 and 4.15-rc7. Neither applied cleanly.
> > > Manually editing just breaks the build with many "open: No such file or
> > > directory".
> > > 
> > > Dont know what went wrong. Can you maybe append patch as file?
> > 
> > Sure, patch is attached, based on 4.15-rc7.
> 
> Applies cleanly to 4.15-rc7. But still:
>   HOSTCC  scripts/asn1_compiler
>   HOSTCC  scripts/extract-cert
>   CC      init/main.o
> open: No such file or directory
> make[1]: *** [scripts/Makefile.build:317: init/main.o] Error 1
> make: *** [Makefile:1015: init] Error 2
> 
> 
> Reverting that patch makes it build again.

Weird.  Here's a version which should hopefully give a better error
message.

-- 
Josh

View attachment "objtool-gold-v2.patch" of type "text/plain" (1972 bytes)