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Message-ID: <20141120081424.293a413a@vostro>
Date: Thu, 20 Nov 2014 08:14:24 +0200
From: Timo Teras <timo.teras@....fi>
To: Isaac Dunham <ibid.ag@...il.com>
Cc: musl@...ts.openwall.com
Subject: Re: webkitfltk segfaults in do_relocs
On Wed, 19 Nov 2014 14:43:40 -0800
Isaac Dunham <ibid.ag@...il.com> wrote:
> On Wed, Nov 19, 2014 at 03:56:35PM -0500, Rich Felker wrote:
> > Got it. The line number in your original report seems to be off by a
> > bit (it points to TLSDESC related cases) but I've found the
> > offending relocation(s):
> >
> > 0083deea 0000c402 R_386_PC32 00000000 exp
> > 0083df03 00010a02 R_386_PC32 00000000 log
> > 0083df1c 00030502 R_386_PC32 00000000 floor
> > 0083df35 00024502 R_386_PC32 00000000 ceil
> >
> > I have no idea why the linker is emitting these. It should have
> > resolved them at ld time to PLT entries in the main program's PLT,
> > but maybe since you're building as PIE (this is defautl on Alpine)
> > that doesn't happen (this would be a linker bug, IMO). If it were
> > going to do this (leave the relocations in the output), it should
> > mark the program as DT_TEXTREL (having textrels), but this is
> > probably suppressed for PIE because it's not supposed to happen.
See also the following link on how to figure out where textrels come
from:
http://wiki.gentoo.org/wiki/Hardened/HOWTO_locate_and_fix_textrels
> > My best guess as to what's triggering the problem is that there's
> > some nasty asm or other hacks that are not PIE-compatible somewhere
> > in the program. It's also possible that you're pulling in static
> > libraries (which would not be PIE-compatible) due to not having the
> > dynamic version of a needed library installed.
>
> All external libs are available in shared format, except perhaps -lgcc
> But the whole library is built in static form only, without -fPIC.
You need -fPIC for PIE-linking. Missing -fPIC is likely cause for this.
If there's some weird reason to not use -fPIC, you probably also need
to link the executable with -fno-PIE, but this means the main DSO will
not be included in address space layout randomization.
/Timo
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