Bug 106222 – Support for >gcc-4* ssp in glibc/uclibc

• Product: Gentoo Linux
• Status: RESOLVED FIXED

[Description Kevin F. Quinn (RETIRED) 2005-09-16 15:45:51 UTC]

GCC-4.x will have a new re-implemenation of the stack protector, provided
upstream at least from GCC-4.1 (for backport to gcc-4.0 see bug #100689).  New
support for this will be required in libc; this bug is to record significant
decisions/progress in support for glibc/uclibc and perhaps klibc.

SSP support for the new implementation is provided by different symbols;
although the support can be very similar, the new symbol names provide the
ability to differentiate as necessary.

Jakub Jelinek's changes for Redhat:
http://sourceware.org/ml/libc-hacker/2005-06/msg00011.html
some of which we may or may not want to modify/replace in glibc.

Issues that come to mind that are under discussion so far include:
1) Use of syscall instead of libc calls in the guard setup and
   overflow handler, on linux kernels
2) Choice of random devices for the guard and implications from various
   kernel versions, especially w.r.t. having sufficient entropy
   and sufficient randomness, and also for workability in chroots.
3) Support on non-linux kernels

[Comment 1 Christophe Saout 2005-09-19 06:42:19 UTC]

In case you didn't notice it, but I've been advertising this for the last two
months.

I've got a hardened gcc 4.0 toolchain running on x86, ppc and amd64 without any
problems.

I extracted the small changes between the gcc vanilla and RedHat's tree so that
the SSP patch from the Fedora SRPM can be applied on top (and the other
backported stuff too).

And then the stuff in glibc and some modifications to toolchain.eclass so that
it knows about gcc 4.x ssp.

I also opened a bug about this some time ago:
https://bugs.gentoo.org/show_bug.cgi?id=100689

[Comment 2 Kevin F. Quinn (RETIRED) 2005-09-19 11:42:11 UTC]

Christophe, we're not ignoring you (far from it); your work on gcc-4.0 is
appreciated.  You'll see the first thing I wrote was a reference to your bug for
gcc itself.  This bug is specifically to track Gentoo modifications to the new
ssp support as it integrates into the various _libc_ implementations.

For the record here, glibc-2.3.5 branch update 20050722 contains the RedHat
implementation of the SSP support into glibc, as of that date.  See above for
some items where we may wish to diverge.

[Comment 3 Christophe Saout 2005-09-19 14:22:22 UTC]

Oh, sorry then. I didn't know how I managed to overlook that one.

I'm pretty open to what you implement in glibc as long as you don't get ABI
incompatible. I like that TLS is used for the stack guard when available, it's
faster on some architectures than looking up the GOT pointer first and you can
have a per-thread stack guard.

[Comment 4 Mark Loeser (RETIRED) 2006-03-13 19:36:58 UTC]

Well, lets bring this one back to life :)  How far along is any of this?  Or is gcc-4.1 still not ready for hardened?

[Comment 5 Kevin F. Quinn (RETIRED) 2006-03-13 23:19:01 UTC]

Well, ssp support for gcc-4.1 is in glibc-2.4.  However currently glibc-2.4 doesn't build with the hardened gcc - symptoms for me are the same as those reported on bug #94325; I'm still working on that.  Also the move of __guard from libc.so to ld.so is going to cause some trouble.

Also, whether it's worth back-porting to glibc-2.3.x I'm not sure.  Probably not.

[Comment 6 Simon Strandman 2006-03-14 00:47:54 UTC]

What kind of build problems are there? I've been using a hardened gcc 4.0 for about 4 months with glibc 2.3.90/2.4 and never had any problems with that. The gcc and glibc ebuilds in my overlay are initially based on Christophe's work.

 [1] i686-pc-linux-gnu-4.0.2-20051117 *
 [2] i686-pc-linux-gnu-4.0.2-20051117-hardenednopie
 [3] i686-pc-linux-gnu-4.0.2-20051117-hardenednopiessp
 [4] i686-pc-linux-gnu-4.0.2-20051117-hardenednossp
 [5] i686-pc-linux-gnu-4.0.2-20051117-vanilla
 [6] i686-pc-linux-gnu-4.1.0

GNU C Library development release version 2.4, by Roland McGrath et al.
Copyright (C) 2006 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE.
Compiled by GNU CC version 4.0.2-20051117 (Gentoo Hardened 4.0.2.20051117-r2, ssp-4.0-internal, pie-8.7.8).
Compiled on a Linux 2.6.11 system on 2006-03-11.

[Comment 7 Simon Strandman 2006-03-14 01:03:23 UTC]

Created attachment 82079 [details, diff]
Patch

Hm. It might be this patch that fixes it.

[Comment 8 SpanKY 2006-03-16 20:36:54 UTC]

> Well, ssp support for gcc-4.1 is in glibc-2.4.  However currently glibc-2.4
> doesn't build with the hardened gcc - symptoms for me are the same as those
> reported on bug #94325; I'm still working on that.  Also the move of __guard
> from libc.so to ld.so is going to cause some trouble.

glibc-2.4-r1 should rectify this situation

[Comment 9 Julian Sasse 2006-03-17 10:08:51 UTC]

> glibc-2.4-r1 should rectify this situation

glibc-2.4-r1 still fails to compile with hardened -- exact same errors as glibc-2.4 (multiple definition of `_itoa') as in bug #94325
(at least this is the case on AMD64)

[Comment 10 SpanKY 2006-03-17 10:26:34 UTC]

> > glibc-2.4-r1 should rectify this situation
> 
> glibc-2.4-r1 still fails to compile with hardened

you're confusing things ... i said the __guard situation is fixed, i never said anything about being able to compile it with -fssp

[Comment 11 Kevin F. Quinn (RETIRED) 2006-06-11 07:15:38 UTC]

Since glibc-2.4 now supports both the 3.x ssp and 4.x ssp, this can be closed, I think.