linux-kernel - Re: BUG: GCC-4.4.x changes the function frame on some functions

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20091119200524.GF4967@nowhere>
Date:	Thu, 19 Nov 2009 21:05:26 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Kai Tietz <ktietz70@...glemail.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	David Daney <ddaney@...iumnetworks.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Haley <aph@...hat.com>,
	Richard Guenther <richard.guenther@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	feng.tang@...el.com, Peter Zijlstra <peterz@...radead.org>,
	jakub@...hat.com, gcc@....gnu.org
Subject: Re: BUG: GCC-4.4.x changes the function frame on some functions

On Thu, Nov 19, 2009 at 08:54:56PM +0100, Kai Tietz wrote:
> 2009/11/19 Frederic Weisbecker <fweisbec@...il.com>:
> > I would really like this. So that we can forget about other possible
> > further suprises due to sophisticated function prologues beeing before
> > the mcount call.
> >
> > And I guess that would fix it in every archs.
> 
> My 5 cent for this, too.
> 
> > That said, Linus had a good point about the fact there might other uses
> > of mcount even more tricky than what does the function graph tracer,
> > outside the kernel, and those may depend on the strict ABI assumption
> > that 4(ebp) is always the _real_ return address, and that through all
> > the previous stack call. This is even a concern that extrapolates the
> > single mcount case.
> >
> > So I wonder that actually the real problem is the lack of something that
> > could provide this guarantee. We may need a -real-ra-before-fp (yeah
> > I suck in naming).
> 
> There are, especially in windows world. We noticed that for example
> the Sun's JDK (which is compiled by VC) can be used in gcc compiled
> code only by -fno-omit-frame-pointer, as otherwise it fails badly
> reasoned by wrong ebp accesses.


Yeah but what we need is not only to ensure ebp is used as the frame
pointer but also that ebp + 4 is really the address that will be used
to return to the caller, and not a copy of the return value.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/