On Tue, Jan 10, 2012 at 8:50 PM, Tijl Coosemans <t...@freebsd.org> wrote:
> On Tuesday 10 January 2012 15:40:15 Richard Guenther wrote:
>> On Tue, Jan 10, 2012 at 3:38 PM, Richard Guenther
>> <richard.guent...@gmail.com> wrote:
>>> On Tue, Jan 10, 2012 at 3:14 PM, Tijl Coosemans <t...@coosemans.org> wrote:
>>>> On targets where libc implements stack protector functions (GNU libc,
>>>> FreeBSD libc), and where gcc (as an optimisation) generates calls to
>>>> a locally defined __stack_chk_fail_local instead of directly calling
>>>> the global function __stack_chk_fail (e.g. -fpic code on i386), one
>>>> must explicitly specify -lssp_nonshared or "-lc -lc_nonshared" on the
>>>> command line to statically link in __stack_chk_fail_local.
>>>>
>>>> It would be more convenient if the compiler kept the details of this
>>>> target specific optimisation hidden by passing -lssp_nonshared to the
>>>> linker internally.
>>>>
>>>> Here's a simple test case that shows the problem on i386-freebsd, but
>>>> works just fine on e.g. x86_64 targets:
>>>>
>>>> % cat test.c
>>>> int
>>>> main( void ) {
>>>> return( 0 );
>>>> }
>>>> % gcc46 -o test test.c -fstack-protector-all -fPIE
>>>> /var/tmp//ccjYQxKu.o: In function `main':
>>>> test.c:(.text+0x37): undefined reference to `__stack_chk_fail_local'
>>>> /usr/local/bin/ld: test: hidden symbol `__stack_chk_fail_local' isn't
>>>> defined
>>>> /usr/local/bin/ld: final link failed: Bad value
>>>> collect2: ld returned 1 exit status
>>>>
>>>>
>>>> I don't have commit access, so please commit when approved.
>>>
>>> Works fine for me on i?86-linux without -lssp_nonshared (which I do not
>>> have, so linking would fail).
>
> So my patch would actually break Linux?
Yes.
>> Probably because libc.so is a linker script:
>>
>> /* GNU ld script
>> Use the shared library, but some functions are only in
>> the static library, so try that secondarily. */
>> OUTPUT_FORMAT(elf64-x86-64)
>> GROUP ( /lib64/libc.so.6 /usr/lib64/libc_nonshared.a AS_NEEDED (
>> /lib64/ld-linux-x86-64.so.2 ) )
>>
>> and /usr/lib64/libc_nonshared.a provides the symbol. Why not fix it that
>> way on *BSD?
>
> I'll discuss it with some FreeBSD developers. Currently FreeBSD doesn't
> use linker scripts anywhere. Would a FreeBSD specific version of the
> patch be acceptable? For instance, the version of GCC shipped with
> FreeBSD has been patched like this:
> http://svnweb.freebsd.org/base/head/contrib/gcc/config/freebsd-spec.h?r1=195697&r2=195696
That looks better to me.
Richard.
