Openwall GNU/*/Linux - a small security-enhanced Linux distro for servers
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Date: Tue, 24 Apr 2012 18:10:40 -0400
From: Rich Felker <>
Subject: Re: New gcc wrapper to try

On Tue, Apr 24, 2012 at 05:41:27PM -0400, Rich Felker wrote:
> On Wed, Apr 25, 2012 at 01:28:40AM +0400, Solar Designer wrote:
> > Rich, Isaac -
> > 
> > On Tue, Apr 24, 2012 at 12:28:28PM -0700, Isaac Dunham wrote:
> > > On Mon, 23 Apr 2012 05:19:05 -0400 Rich Felker <> wrote:
> > > > Somebody has enabled stack protector. Either your distro (what distro
> > > > are you using) has hacked gcc in a way different from what musl-gcc
> > > > expects, or wireless-tools' makefile is adding -fstack-protector...
> > > 
> > > There's no -fstack-protector, so it's Ubuntu's fault.
> > 
> > Several distros do it these days (and Owl will start doing it soon as
> > well), so it's becoming standard and needs to be supported.
> > Technically, -fno-stack-protector in the musl-gcc wrapper would probably
> > make things appear to work, but it's not necessarily a good thing to do
> > since it might violate reasonable expectations of the user.  I think
> > it'd be better for musl to start providing the necessary symbols.
> The problem is that the default gcc build incorporates glibc ABI
> knowledge (layout of the thread structure) and the assumption that the
> thread pointer has been initialized into any binary built with stack
> protector. Just adding symbols will not fix anything.
> If gcc's stack protector support is built without TLS support so that
> it uses a global variable for the canary, instead of a thread-local
> variable, then we could support it with no work at all. Unfortunately
> I don't believe there's any way to override the type of canary access
> gcc does via command line options; you have to rebuild gcc. Thus, for
> the time being (until/unless we do TLS and mimic glibc's structure
> layout), disabling stack protector is the only option for the wrapper
> to use. For our own native gcc builds, we can already support it if I
> just add the symbol it needs.

......but since you requested it, I'm working on trying to make it
work anyway. We'll see how it goes. Preliminary support was just


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