hurd: Fix pthread_self() without libpthread

5476f8cd2e ("htl: move pthread_self info libc.") moved the htl
pthread_self() function from libpthread to libc, replacing the previous libc
stub that just returns 0. And 53da64d1cf ("htl: Initialize ___pthread_self
early") added initialization code which is needed before being able to
call pthread_self. It is currently in libpthread, and thus never called
before programs can call pthread_self from libc, which then segfaults
when accessing _pthread_self()->thread.

This moves the initialization to libc itself, as initialized variables, so
pthread_self can always be called fine.

htl/Versions

@@ -38,6 +38,7 @@ libc {
     __pthread_cleanup_stack;
     __pthread_total;
     ___pthread_self;
+    __pthread_init_thread;
   }
 }
 

sysdeps/mach/hurd/htl/pt-pthread_self.c

@@ -17,6 +17,13 @@
    <https://www.gnu.org/licenses/>.  */
 
 #include <pt-sysdep.h>
+#include <pt-internal.h>
 
-__thread struct __pthread *___pthread_self;
+/* Initial thread structure used before libpthread is initialized, so various
+ * functions can already work at least basically.  */
+struct __pthread __pthread_init_thread = {
+	.thread = 1,
+};
+
+__thread struct __pthread *___pthread_self = &__pthread_init_thread;
 libc_hidden_tls_def (___pthread_self)

sysdeps/mach/hurd/htl/pt-sysdep.c

@@ -26,10 +26,6 @@
 #include <pt-internal.h>
 #include <pthreadP.h>
 
-/* Initial thread structure used temporarily during initialization, so various
- * functions can already work at least basically.  */
-static struct __pthread init_thread;
-
 static void
 reset_pthread_total (void)
 {
@@ -51,10 +47,6 @@ _init_routine (void *stack)
     /* Already initialized */
     return;
 
-  /* Initialize early thread structure.  */
-  init_thread.thread = 1;
-  ___pthread_self = &init_thread;
-
   /* Initialize the library.  */
   ___pthread_init ();
 
@@ -116,9 +108,9 @@ _init_routine (void *stack)
 #endif
 
   /* Copy over the thread-specific state */
-  assert (!init_thread.thread_specifics);
+  assert (!__pthread_init_thread.thread_specifics);
   memcpy (&thread->static_thread_specifics,
-          &init_thread.static_thread_specifics,
+          &__pthread_init_thread.static_thread_specifics,
           sizeof (thread->static_thread_specifics));
 
   ___pthread_self = thread;

sysdeps/mach/hurd/htl/pt-sysdep.h

@@ -34,6 +34,8 @@
 
 extern __thread struct __pthread *___pthread_self;
 libc_hidden_tls_proto (___pthread_self)
+extern struct __pthread ___pthread_init_thread;
+libc_hidden_proto (___pthread_init_thread)
 
 #ifdef DEBUG
 #define _pthread_self()                                            \