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?
> 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
>>> 2011-01-10 Tijl Coosemans <t...@coosemans.org>
>>>
>>> * gcc.c [TARGET_LIBC_PROVIDES_SSP] (LINK_SSP_SPEC): Add
>>> -lssp_nonshared.
>>>
>>> --- gcc/gcc.c.orig
>>> +++ gcc/gcc.c
>>> @@ -602,7 +602,7 @@ proper position among the other output f
>>>
>>> #ifndef LINK_SSP_SPEC
>>> #ifdef TARGET_LIBC_PROVIDES_SSP
>>> -#define LINK_SSP_SPEC "%{fstack-protector:}"
>>> +#define LINK_SSP_SPEC
>>> "%{fstack-protector|fstack-protector-all:-lssp_nonshared}"
>>> #else
>>> #define LINK_SSP_SPEC
>>> "%{fstack-protector|fstack-protector-all:-lssp_nonshared -lssp}"
>>> #endif
