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

[Sam James]

"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.

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 {