[PATCH v2] x86-64: Add GLIBC_ABI_GNU2_TLS version [BZ #33129]

[Sam James]

Sam James <sam@gentoo.org> writes:

> "H.J. Lu" <hjl.tools@gmail.com> writes:
>
>> Programs and shared libraries compiled with -mtls-dialect=gnu2 may fail
>> silently at run-time against glibc without the GNU2 TLS run-time fix
>> for:
>>
>> https://sourceware.org/bugzilla/show_bug.cgi?id=31372
>>
>> Add GLIBC_ABI_GNU2_TLS version to indicate that glibc has the working
>> GNU2 TLS run-time.  Linker can add the GLIBC_ABI_GNU2_TLS version to
>> binaries which depend on the working GNU2 TLS run-time:
>>
>> https://sourceware.org/bugzilla/show_bug.cgi?id=33130
>>
>> so that such programs and shared libraries will fail to load and run at
>> run-time against libc.so without the GLIBC_ABI_GNU2_TLS version, instead
>> of fail silently at random.
>>
>> This fixes BZ #33129.
>
> LGTM. I was holding off because I wanted to give Florian et. al a chance
> to object if they don't like the approach, but I see no problem with it.

BTW, I hope we can make some progress on default-enabling in GCC
16. Any approach works for us, just we need consensus from those who
handle older glibcs more often.

>
> Reviewed-by: Sam James <sam@gentoo.org>
>
>>
>> Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
>> ---
>>  sysdeps/x86_64/Makefile | 9 +++++++++
>>  sysdeps/x86_64/Versions | 5 +++++
>>  2 files changed, 14 insertions(+)
>>
>> diff --git a/sysdeps/x86_64/Makefile b/sysdeps/x86_64/Makefile
>> index c3e1065c81..3ab8c1ed0f 100644
>> --- a/sysdeps/x86_64/Makefile
>> +++ b/sysdeps/x86_64/Makefile
>> @@ -212,6 +212,15 @@ LDFLAGS-tst-plt-rewrite2 = -Wl,-z,now
>>  LDFLAGS-tst-plt-rewritemod2.so = -Wl,-z,now,-z,undefs
>>  tst-plt-rewrite2-ENV = GLIBC_TUNABLES=glibc.cpu.plt_rewrite=2
>>  $(objpfx)tst-plt-rewrite2: $(objpfx)tst-plt-rewritemod2.so
>> +
>> +tests-special += $(objpfx)check-gnu2-tls.out
>> +
>> +$(objpfx)check-gnu2-tls.out: $(common-objpfx)libc.so
>> +	LC_ALL=C $(READELF) -V -W $< \
>> +		| sed -ne '/.gnu.version_d/, /.gnu.version_r/ p' \
>> +		| grep GLIBC_ABI_GNU2_TLS > $@; \
>> +	$(evaluate-test)
>> +generated += check-gnu2-tls.out
>>  endif
>>  
>>  test-internal-extras += tst-gnu2-tls2mod1
>> diff --git a/sysdeps/x86_64/Versions b/sysdeps/x86_64/Versions
>> index e94758b236..a63c11bcb2 100644
>> --- a/sysdeps/x86_64/Versions
>> +++ b/sysdeps/x86_64/Versions
>> @@ -5,6 +5,11 @@ libc {
>>    GLIBC_2.13 {
>>      __fentry__;
>>    }
>> +  GLIBC_ABI_GNU2_TLS {
>> +    # This symbol is used only for empty version map and will be removed
>> +    # by scripts/versions.awk.
>> +    __placeholder_only_for_empty_version_map;
>> +  }
>>  }
>>  libm {
>>    GLIBC_2.1 {