Fix TLS access for -static -pthread

I have posted:
	TLS variables access for -static -lpthread executables
	https://sourceware.org/ml/libc-help/2014-03/msg00024.html
and the GDB patch below has been confirmed as OK for current glibcs.

Further work should be done for newer glibcs:
	Improve TLS variables glibc compatibility
	https://sourceware.org/bugzilla/show_bug.cgi?id=16954

Still the patch below implements the feature in a fully functional way backward
compatible with current glibcs, it depends on the following glibc source line:
	csu/libc-tls.c
	main_map->l_tls_modid = 1;

gdb/
2014-05-21  Jan Kratochvil  <jan.kratochvil@redhat.com>

	Fix TLS access for -static -pthread.
	* linux-thread-db.c (struct thread_db_info): Add td_thr_tlsbase_p.
	(try_thread_db_load_1): Initialize it.
	(thread_db_get_thread_local_address): Call it if LM is zero.
	* target.c (target_translate_tls_address): Remove LM_ADDR zero check.
	* target.h (struct target_ops) (to_get_thread_local_address): Add
	load_module_addr comment.

gdb/gdbserver/
2014-05-21  Jan Kratochvil  <jan.kratochvil@redhat.com>

	Fix TLS access for -static -pthread.
	* gdbserver/thread-db.c (struct thread_db): Add td_thr_tlsbase_p.
	(thread_db_get_tls_address): Call it if LOAD_MODULE is zero.
	(thread_db_load_search, try_thread_db_load_1): Initialize it.

gdb/testsuite/
2014-05-21  Jan Kratochvil  <jan.kratochvil@redhat.com>

	Fix TLS access for -static -pthread.
	* gdb.threads/staticthreads.c <HAVE_TLS> (tlsvar): New.
	<HAVE_TLS> (thread_function, main): Initialize it.
	* gdb.threads/staticthreads.exp: Try gdb_compile_pthreads for $have_tls.
	Add clean_restart.
	<$have_tls != "">: Check TLSVAR.

Message-ID: <20140410115204.GB16411@host2.jankratochvil.net>

1 files changed, 31 insertions, 7 deletions

diff --git a/gdb/gdbserver/thread-db.c b/gdb/gdbserver/thread-db.c
index ae0d191..3ea0cc3 100644
--- a/gdb/gdbserver/thread-db.c
+++ b/gdb/gdbserver/thread-db.c
@@ -88,6 +88,9 @@ struct thread_db
   td_err_e (*td_thr_tls_get_addr_p) (const td_thrhandle_t *th,
 				     psaddr_t map_address,
 				     size_t offset, psaddr_t *address);
+  td_err_e (*td_thr_tlsbase_p) (const td_thrhandle_t *th,
+				unsigned long int modid,
+				psaddr_t *base);
   const char ** (*td_symbol_list_p) (void);
 };
 
@@ -503,7 +506,10 @@ thread_db_get_tls_address (struct thread_info *thread, CORE_ADDR offset,
   if (thread_db == NULL || !thread_db->all_symbols_looked_up)
     return TD_ERR;
 
-  if (thread_db->td_thr_tls_get_addr_p == NULL)
+  /* If td_thr_tls_get_addr is missing rather do not expect td_thr_tlsbase
+     could work.  */
+  if (thread_db->td_thr_tls_get_addr_p == NULL
+      || (load_module == 0 && thread_db->td_thr_tlsbase_p == NULL))
     return -1;
 
   lwp = get_thread_lwp (thread);
@@ -514,12 +520,28 @@ thread_db_get_tls_address (struct thread_info *thread, CORE_ADDR offset,
 
   saved_inferior = current_inferior;
   current_inferior = thread;
-  /* Note the cast through uintptr_t: this interface only works if
-     a target address fits in a psaddr_t, which is a host pointer.
-     So a 32-bit debugger can not access 64-bit TLS through this.  */
-  err = thread_db->td_thr_tls_get_addr_p (&lwp->th,
-					  (psaddr_t) (uintptr_t) load_module,
-					  offset, &addr);
+
+  if (load_module != 0)
+    {
+      /* Note the cast through uintptr_t: this interface only works if
+	 a target address fits in a psaddr_t, which is a host pointer.
+	 So a 32-bit debugger can not access 64-bit TLS through this.  */
+      err = thread_db->td_thr_tls_get_addr_p (&lwp->th,
+					     (psaddr_t) (uintptr_t) load_module,
+					      offset, &addr);
+    }
+  else
+    {
+      /* This code path handles the case of -static -pthread executables:
+	 https://sourceware.org/ml/libc-help/2014-03/msg00024.html
+	 For older GNU libc r_debug.r_map is NULL.  For GNU libc after
+	 PR libc/16831 due to GDB PR threads/16954 LOAD_MODULE is also NULL.
+	 The constant number 1 depends on GNU __libc_setup_tls
+	 initialization of l_tls_modid to 1.  */
+      err = thread_db->td_thr_tlsbase_p (&lwp->th, 1, &addr);
+      addr = (char *) addr + offset;
+    }
+
   current_inferior = saved_inferior;
   if (err == TD_OK)
     {
@@ -571,6 +593,7 @@ thread_db_load_search (void)
   tdb->td_ta_set_event_p = &td_ta_set_event;
   tdb->td_ta_event_getmsg_p = &td_ta_event_getmsg;
   tdb->td_thr_tls_get_addr_p = &td_thr_tls_get_addr;
+  tdb->td_thr_tlsbase_p = &td_thr_tlsbase;
 
   return 1;
 }
@@ -639,6 +662,7 @@ try_thread_db_load_1 (void *handle)
   CHK (0, tdb->td_ta_set_event_p = dlsym (handle, "td_ta_set_event"));
   CHK (0, tdb->td_ta_event_getmsg_p = dlsym (handle, "td_ta_event_getmsg"));
   CHK (0, tdb->td_thr_tls_get_addr_p = dlsym (handle, "td_thr_tls_get_addr"));
+  CHK (0, tdb->td_thr_tlsbase_p = dlsym (handle, "td_thr_tlsbase"));
 
 #undef CHK