hurd: Only check for TLS initialization inside rtld or in static builds

When glibc is built as a shared library, TLS is always initialized by
the call of TLS_INIT_TP () macro made inside the dynamic loader, prior
to running the main program (see dl-call_tls_init_tp.h). We can take
advantage of this: we know for sure that __LIBC_NO_TLS () will evaluate
to 0 in all other cases, so let the compiler know that explicitly too.

Also, only define _hurd_tls_init () and TLS_INIT_TP () under the same
conditions (either !SHARED or inside rtld), to statically assert that
this is the case.

Other than a microoptimization, this also helps with avoiding awkward
sharing of the __libc_tls_initialized variable between ld.so and libc.so
that we would have to do otherwise -- we know for sure that no sharing
is required, simply because __libc_tls_initialized would always be set
to true inside libc.so.

Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Message-Id: <20230319151017.531737-25-bugaevc@gmail.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/sysdeps/mach/hurd/Makefile b/sysdeps/mach/hurd/Makefile
index 0e880755ca..8fb6baf09e 100644
--- a/sysdeps/mach/hurd/Makefile
+++ b/sysdeps/mach/hurd/Makefile
@@ -197,6 +197,10 @@ ifeq (hurd, $(subdir))
 sysdep_routines += cthreads
 endif
 
+ifeq (elf, $(subdir))
+sysdep-dl-routines += dl-tls-initialized
+endif
+
 ifeq (io, $(subdir))
 sysdep_routines += f_setlk close_nocancel close_nocancel_nostatus \
 		   fcntl_nocancel open_nocancel openat_nocancel read_nocancel \