On Wednesday 11 January 2012 10:06:42 Richard Guenther wrote:
> 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.
I've been using this patch now. It's similar to the above url, but
conditional on TARGET_LIBC_PROVIDES_SSP to support older FreeBSD
versions.
Gerald volunteered to commit. Gerald, just trunk for now or older
branches too?
2011-01-20 Tijl Coosemans <t...@coosemans.org>
* gcc/config/freebsd-spec.h [TARGET_LIBC_PROVIDES_SSP] (LINK_SSP_SPEC):
Define.
--- gcc/config/freebsd-spec.h
+++ gcc/config/freebsd-spec.h
@@ -138,6 +138,10 @@ is built with the --enable-threads confi
#define LINK_EH_SPEC "%{!static:--eh-frame-hdr} "
#endif
+#ifdef TARGET_LIBC_PROVIDES_SSP
+#define LINK_SSP_SPEC
"%{fstack-protector|fstack-protector-all:-lssp_nonshared}"
+#endif
+
/* Use --as-needed -lgcc_s for eh support. */
#ifdef HAVE_LD_AS_NEEDED
#define USE_LD_AS_NEEDED 1
