Re: [PATCH] [BZ #20309] X86-64: Properly align stack in _dl_tlsdesc_dynamic

[Szabolcs Nagy <szabolcs dot nagy at arm dot com>]

On 11/07/16 16:55, H.J. Lu wrote:
> On Wed, Jun 29, 2016 at 6:24 AM, H.J. Lu <hongjiu.lu@intel.com> wrote:
>> Since _dl_tlsdesc_dynamic is called via PLT, we need to add 8 bytes
>> for for push in the PLT entry to align the stack.
>>
>> Tested on i686 and x86-64.  OK for trunk?
> 
> If there is no objection by the end of today, I will check it tomorrow.
...
>> +AC_CACHE_CHECK([for -mtls-dialect=gnu2], libc_cv_mtls_dialect_gnu2,
>> +[dnl
>> +cat > conftest.c <<EOF
>> +__thread int i;
>> +void foo (void)
>> +{
>> +  i = 10;
>> +}
>> +EOF
>> +if AC_TRY_COMMAND([${CC-cc} $CFLAGS $CPPFLAGS -S -fPIC -mtls-dialect=gnu2
>> +                  conftest.c 1>&AS_MESSAGE_LOG_FD])
>> +then
>> +  libc_cv_mtls_dialect_gnu2=yes
>> +else
>> +  libc_cv_mtls_dialect_gnu2=no
>> +fi
>> +rm -f conftest*])
>> +AC_SUBST(libc_cv_mtls_dialect_gnu2)
>> +LIBC_CONFIG_VAR([have-mtls-dialect-gnu2], [$libc_cv_mtls_dialect_gnu2])
>> +

on aarch64 the flag is -mtls-dialect=desc
(it's the default dialect though)

>> --- a/elf/Makefile
>> +++ b/elf/Makefile
>> @@ -224,6 +224,13 @@ modules-names = testobj1 testobj2 testobj3 testobj4 testobj5 testobj6 \
>>                 tst-tlsalign-lib tst-nodelete-opened-lib tst-nodelete2mod \
>>                 tst-audit11mod1 tst-audit11mod2 tst-auditmod11 \
>>                 tst-audit12mod1 tst-audit12mod2 tst-audit12mod3 tst-auditmod12
>> +ifeq (yes,$(have-mtls-dialect-gnu2))
>> +tests += tst-gnu2-tls1
>> +modules-names += tst-gnu2-tls1mod
>> +$(objpfx)tst-gnu2-tls1: $(objpfx)tst-gnu2-tls1mod.so
>> +tst-gnu2-tls1mod.so-no-z-defs = yes
>> +CFLAGS-tst-gnu2-tls1mod.c += -mtls-dialect=gnu2
>> +endif

so this new test won't run on aarch64.

i don't object to the patch, but i think
testing with different tls-dialects may
eventually need a better approach.