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

[H.J. Lu]

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 will add the GLIBC_ABI_GNU2_TLS version to
binaries which depend on GNU2 TLS run-time:

https://sourceware.org/bugzilla/show_bug.cgi?id=33130

so that programs and shared libraries compiled with -mtls-dialect=gnu2
will have the glibc GLIBC_ABI_GNU2_TLS version dependency added by the
new linker.  They will fail to load and run at run-time against libc.so
without the GLIBC_ABI_GNU2_TLS version, instead of may fail silently.

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 be64eb2ee4..372c3176d7 100644
--- a/sysdeps/x86_64/Makefile
+++ b/sysdeps/x86_64/Makefile
@@ -208,6 +208,15 @@ 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 {
-- 
2.50.0