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).
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?
Richard.
> Richard.
>
>> 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
