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

Ingo Molnar
2009-02-11T10:58:05Z

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

> Ingo Molnar wrote:
> >>> 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?
>
> It seems that even with the same gcc versions, gcc built against libc
> w/o TLS support generates __stack_chk_guard, so if you mix the two
> flavors, the has-stack-protector check can be compiled on machines w/
> TLS while some other files end up being built on machines w/o TLS
> support thus circumventing the support check. Can you please see
> whether non-distcc build fails too?

That build succeeds:

rhea:~/tip> make -j30 bzImage ARCH=x86_64 CROSS_COMPILE='/opt/crosstool/gcc-4.2.3-glibc-2.3.6/x86_64-unknown-linux-gnu/bin/x86_64-unknown-linux-gnu-'
/home/mingo/tip/arch/x86/Makefile:82: stack protector enabled but no compiler support
CHK include/linux/version.h
[...]
BFD: arch/x86/boot/compressed/vmlinux.bin: warning: allocated section `.bss' not in segment
[...]
Root device is (8, 3)
Setup is 11996 bytes (padded to 12288 bytes).
System is 5690 kB
CRC be1b2e21
Kernel: arch/x86/boot/bzImage is ready (#3)

Some shell variable expansion bug? If CROSS_COMPILE is not a single word
we fail to detect the compiler borkage at arch/x86/Makefile line 82?

Ingo