Re: [PATCHSET x86/master] add stack protector support for x86_32

Ingo Molnar
2009-02-10T14:20:47Z

* Tejun Heo <tj@kernel.org> wrote:

> Tejun Heo wrote:
> > Ingo Molnar wrote:
> >> * Ingo Molnar <mingo@elte.hu> wrote:
> >>
> >>> [...] I might not get around testing it today and pushing it out into tip:master,
> >>> but i pushed out the core/percpu bits, should you queue up further changes.
> >> ok, activated it for -tip testing, and there's a 64-bit build failure caused by
> >> it:
> >>
> >> arch/x86/kernel/head64.o: In function `x86_64_start_reservations':
> >> head64.c:(.init.text+0x26): undefined reference to `__stack_chk_guard'
> >> head64.c:(.init.text+0xc2): undefined reference to `__stack_chk_guard'
> >> arch/x86/kernel/head64.o: In function `x86_64_start_kernel':
> >> head64.c:(.init.text+0x104): undefined reference to `__stack_chk_guard'
> >> head64.c:(.init.text+0x1cd): undefined reference to `__stack_chk_guard'
> >> arch/x86/kernel/head.o: In function `reserve_ebda_region':
> >> head.c:(.init.text+0xb): undefined reference to `__stack_chk_guard'
> >> arch/x86/kernel/head.o:head.c:(.init.text+0x87): more undefined references to
> >> `__stack_chk_guard' follow
> >
> > Call to __stack_chk_guard is probably generated automatically.
> > Strangely, my gcc only generates calls to __stack_chk_fail.
> >
> > > gcc --version
> > gcc (SUSE Linux) 4.3.2 [gcc-4_3-branch revision 141291]
> > Copyright (C) 2008 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.
> > > nm build/vmlinux|grep __stack_chk_
> > 00000000f0fdf6cb A __crc___stack_chk_fail
> > ffffffff80d53e50 r __kcrctab___stack_chk_fail
> > ffffffff80d5ff81 r __kstrtab___stack_chk_fail
> > ffffffff80d3d140 r __ksymtab___stack_chk_fail
> > ffffffff80248619 T __stack_chk_fail
> >
> > I'll try other compilers but which version are you using? The
> > difference is that before the patchset, -fno-stack-protector was
> > always added whether stackprotector was enabled or not so this problem
> > wasn't visible (at the cost of bogus stackprotector of course). We'll
> > probably need to add __stack_chk_guard or disable if gcc generates
> > such symbol. I'll play with different gccs.
>
> Can't reproduce with gcc-4.1 or 4.2. Any chance you're using distcc
> w/ a build machine w/ glibc < 2.4? __stack_chk_guard is the symbol
> gcc fetches stack canary from if TLS is not supported, so somehow gcc
> thought that TLS wasn't available while building head64.

yeah - i also used distcc. Maybe the nostackp makefile magic gets confused
about that?

Ingo