[PATCH] S390: Support PLT and GOT references in check-localplt.

[Stefan Liebler]

On 08/17/2016 03:48 PM, Florian Weimer wrote:
> On 08/09/2016 04:22 PM, Stefan Liebler wrote:
>> On 08/09/2016 03:53 PM, Florian Weimer wrote:
>>> On 08/09/2016 03:34 PM, Stefan Liebler wrote:
>>>> After the commits __libc_memalign is only called in elf/dl-minimal.c in
>>>> malloc() function in ld.so and gcc -O2/-O3 leads to R_390_GLOB_DAT
>>>> instead of R_390_JMP_SLOT. __libc_memalign is called via
>>>> function-pointer loaded from GOT instead of calling via a plt-stub.
>>>
>>> Huh.  I wonder if this is intended.  Surely the malloc implementation in
>>> elf/dl-minimal.c should always call the __libc_memalign implementation
>>> in the same file?
>>>
>>> Thanks,
>>> Florian
>>>
>>
>> Please have a look at the other localplt.data files, e.g.
>> sysdeps/x86_64/localplt.data:
>> # The dynamic loader uses __libc_memalign internally to allocate aligned
>> # TLS storage. The other malloc family of functions are expected to allow
>> # user symbol interposition.
>> ld.so: __libc_memalign + RELA R_X86_64_GLOB_DAT
>>
>> All contains the __libc_memalign relocation.
>> On s390x it has also existed before but a plt-stub was used. If you now
>> use the compiler flag -fno-optimize-sibling-calls you'll get the
>> plt-stub as before. With this optimization the relocation is done via a
>> function pointer.
>
> Okay, but shouldn't be __libc_memalign in dl-minimal.c declared as
> attribute_hidden?
>
> Thanks,
> Florian
>
I don't know. Can you simply do this as __libc_memalign is also 
mentioned in elf/Versions file?
ld {
   GLIBC_2.0 {
     # Function from libc.so which must be shared with libc.
     __libc_memalign; calloc; free; malloc; realloc;

     _r_debug;
   }