Add thread_handle_to_thread_info support for remote targets

This patch adds support to remote targets for converting a thread
handle to a thread_info struct pointer.

A thread handle is fetched via a "handle" attribute which has been
added to the qXfer:threads:read query packet.  An implementation is
provided in gdbserver for targets using the Linux kernel.

gdb/gdbserver/ChangeLog:

	* linux-low.h (struct lwp_info): Add new field, thread_handle.
	(thread_db_thread_handle): Declare.
	* linux-low.c (linux_target_ops): Initialize thread_handle.
	* server.c (handle_qxfer_threads_worker): Add support for
	"handle" attribute.
	* target.h (struct target_ops): Add new function pointer,
	thread_handle.
	(target_thread_handle): Define.
	* thread-db.c (find_one_thread, attach_thread): Set thread_handle
	field in lwp.
	(thread_db_thread_handle): New function.

gdb/ChangeLog:

	* remote.c (vector): Include.
	(struct private_thread_info): Add field, thread_handle.
	(free_private_thread_info): Deallocate storage associated with
	thread handle.
	(get_private_info_thread): Initialize `thread_handle' field.
	(struct thread_item): Add field, thread_handle.
	(clear_threads_listing_context): Deallocate storage associated
	with thread handle.
	(start_thread): Add support for "handle" attribute.
	(thread_attributes): Add "handle".
	(remote_get_threads_with_qthreadinfo): Initialize thread_handle
	field.
	(remote_update_thread_list): Update thread_handle.
	(remote_thread_handle_to_thread_info): New function.
	(init_remote_ops): Initialize to_thread_handle_to_thread_info.

6 files changed, 76 insertions, 0 deletions

diff --git a/gdb/gdbserver/ChangeLog b/gdb/gdbserver/ChangeLog
index b075eb3..75d97f0 100644
--- a/gdb/gdbserver/ChangeLog
+++ b/gdb/gdbserver/ChangeLog
@@ -1,5 +1,19 @@
 2017-09-21  Kevin Buettner  <kevinb@redhat.com>
 
+	* linux-low.h (struct lwp_info): Add new field, thread_handle.
+	(thread_db_thread_handle): Declare.
+	* linux-low.c (linux_target_ops): Initialize thread_handle.
+	* server.c (handle_qxfer_threads_worker): Add support for
+	"handle" attribute.
+	* target.h (struct target_ops): Add new function pointer,
+	thread_handle.
+	(target_thread_handle): Define.
+	* thread-db.c (find_one_thread, attach_thread): Set thread_handle
+	field in lwp.
+	(thread_db_thread_handle): New function.
+
+2017-09-21  Kevin Buettner  <kevinb@redhat.com>
+
 	* linux-low.c (handle_extended_wait): Call thread_db_notice_clone().
 	* linux-low.h (thread_db_notice_clone): Declare.
 	* thread-db.c (thread_db_notice_clone): New function.
diff --git a/gdb/gdbserver/linux-low.c b/gdb/gdbserver/linux-low.c
index a3f9ab9..c62dc19 100644
--- a/gdb/gdbserver/linux-low.c
+++ b/gdb/gdbserver/linux-low.c
@@ -7705,6 +7705,11 @@ static struct target_ops linux_target_ops = {
   linux_supports_software_single_step,
   linux_supports_catch_syscall,
   linux_get_ipa_tdesc_idx,
+#if USE_THREAD_DB
+  thread_db_thread_handle,
+#else
+  NULL,
+#endif
 };
 
 #ifdef HAVE_LINUX_REGSETS
diff --git a/gdb/gdbserver/linux-low.h b/gdb/gdbserver/linux-low.h
index be27c92..85bb8ca 100644
--- a/gdb/gdbserver/linux-low.h
+++ b/gdb/gdbserver/linux-low.h
@@ -374,6 +374,9 @@ struct lwp_info
   /* The thread handle, used for e.g. TLS access.  Only valid if
      THREAD_KNOWN is set.  */
   td_thrhandle_t th;
+
+  /* The pthread_t handle.  */
+  thread_t thread_handle;
 #endif
 
   /* Arch-specific additions.  */
@@ -416,4 +419,6 @@ int thread_db_look_up_one_symbol (const char *name, CORE_ADDR *addrp);
 
 void thread_db_notice_clone (struct process_info *proc, ptid_t lwp);
 
+bool thread_db_thread_handle (ptid_t ptid, gdb_byte **handle, int *handle_len);
+
 extern int have_ptrace_getregset;
diff --git a/gdb/gdbserver/server.c b/gdb/gdbserver/server.c
index a5743b5..f3eee31 100644
--- a/gdb/gdbserver/server.c
+++ b/gdb/gdbserver/server.c
@@ -1648,6 +1648,9 @@ handle_qxfer_threads_worker (struct inferior_list_entry *inf, void *arg)
   int core = target_core_of_thread (ptid);
   char core_s[21];
   const char *name = target_thread_name (ptid);
+  int handle_len;
+  gdb_byte *handle;
+  bool handle_status = target_thread_handle (ptid, &handle, &handle_len);
 
   write_ptid (ptid_s, ptid);
 
@@ -1662,6 +1665,13 @@ handle_qxfer_threads_worker (struct inferior_list_entry *inf, void *arg)
   if (name != NULL)
     buffer_xml_printf (buffer, " name=\"%s\"", name);
 
+  if (handle_status)
+    {
+      char *handle_s = (char *) alloca (handle_len * 2 + 1);
+      bin2hex (handle, handle_s, handle_len);
+      buffer_xml_printf (buffer, " handle=\"%s\"", handle_s);
+    }
+
   buffer_xml_printf (buffer, "/>\n");
 }
 
diff --git a/gdb/gdbserver/target.h b/gdb/gdbserver/target.h
index 91cbde1..0a3d1db 100644
--- a/gdb/gdbserver/target.h
+++ b/gdb/gdbserver/target.h
@@ -475,6 +475,11 @@ struct target_ops
 
   /* Return tdesc index for IPA.  */
   int (*get_ipa_tdesc_idx) (void);
+
+  /* Thread ID to (numeric) thread handle: Return true on success and
+     false for failure.  Return pointer to thread handle via HANDLE
+     and the handle's length via HANDLE_LEN.  */
+  bool (*thread_handle) (ptid_t ptid, gdb_byte **handle, int *handle_len);
 };
 
 extern struct target_ops *the_target;
@@ -693,6 +698,11 @@ void done_accessing_memory (void);
   (the_target->thread_name ? (*the_target->thread_name) (ptid)  \
    : NULL)
 
+#define target_thread_handle(ptid, handle, handle_len) \
+   (the_target->thread_handle ? (*the_target->thread_handle) \
+                                  (ptid, handle, handle_len) \
+   : false)
+
 int read_inferior_memory (CORE_ADDR memaddr, unsigned char *myaddr, int len);
 
 int write_inferior_memory (CORE_ADDR memaddr, const unsigned char *myaddr,
diff --git a/gdb/gdbserver/thread-db.c b/gdb/gdbserver/thread-db.c
index 3d57f31..9156d89 100644
--- a/gdb/gdbserver/thread-db.c
+++ b/gdb/gdbserver/thread-db.c
@@ -200,6 +200,7 @@ find_one_thread (ptid_t ptid)
 
   lwp->thread_known = 1;
   lwp->th = th;
+  lwp->thread_handle = ti.ti_tid;
 
   return 1;
 }
@@ -231,6 +232,7 @@ attach_thread (const td_thrhandle_t *th_p, td_thrinfo_t *ti_p)
   gdb_assert (lwp != NULL);
   lwp->thread_known = 1;
   lwp->th = *th_p;
+  lwp->thread_handle = ti_p->ti_tid;
 
   return 1;
 }
@@ -439,6 +441,36 @@ thread_db_get_tls_address (struct thread_info *thread, CORE_ADDR offset,
     return err;
 }
 
+/* See linux-low.h.  */
+
+bool
+thread_db_thread_handle (ptid_t ptid, gdb_byte **handle, int *handle_len)
+{
+  struct thread_db *thread_db;
+  struct lwp_info *lwp;
+  struct thread_info *thread
+    = (struct thread_info *) find_inferior_id (&all_threads, ptid);
+
+  if (thread == NULL)
+    return false;
+
+  thread_db = get_thread_process (thread)->priv->thread_db;
+
+  if (thread_db == NULL)
+    return false;
+
+  lwp = get_thread_lwp (thread);
+
+  if (!lwp->thread_known && !find_one_thread (thread->entry.id))
+    return false;
+
+  gdb_assert (lwp->thread_known);
+
+  *handle = (gdb_byte *) &lwp->thread_handle;
+  *handle_len = sizeof (lwp->thread_handle);
+  return true;
+}
+
 #ifdef USE_LIBTHREAD_DB_DIRECTLY
 
 static int