Add target method for converting thread handle to thread_info struct pointer

This patch adds a target method named `to_thread_handle_to_thread_info'.
It is intended to map a thread library specific thread handle (such as
pthread_t for the pthread library) to the corresponding GDB internal
thread_info struct (pointer).

An implementation is provided for Linux pthreads; see linux-thread-db.c.

gdb/ChangeLog:

	* target.h (struct target_ops): Add to_thread_handle_to_thread_info.
	(target_thread_handle_to_thread_info): Declare.
	* target.c (target_thread_handle_to_thread_info): New function.
	* target-delegates.c: Regenerate.
	* gdbthread.h (find_thread_by_handle): Declare.
	* thread.c (find_thread_by_handle): New function.
	* linux-thread-db.c (thread_db_thread_handle_to_thread_info): New
	function.
	(init_thread_db_ops): Register thread_db_thread_handle_to_thread_info.

gdb/ChangeLog

@@ -1,3 +1,15 @@
+2017-09-21  Kevin Buettner  <kevinb@redhat.com>
+
+	* target.h (struct target_ops): Add to_thread_handle_to_thread_info.
+	(target_thread_handle_to_thread_info): Declare.
+	* target.c (target_thread_handle_to_thread_info): New function.
+	* target-delegates.c: Regenerate.
+	* gdbthread.h (find_thread_by_handle): Declare.
+	* thread.c (find_thread_by_handle): New function.
+	* linux-thread-db.c (thread_db_thread_handle_to_thread_info): New
+	function.
+	(init_thread_db_ops): Register thread_db_thread_handle_to_thread_info.
+
 2017-09-21  Simon Marchi  <simon.marchi@ericsson.com>
 
 	* nat/linux-waitpid.c (linux_debug): Add ATTRIBUTE_PRINTF.

gdb/gdbthread.h

@@ -448,6 +448,10 @@ extern struct thread_info *find_thread_ptid (ptid_t ptid);
 /* Find thread by GDB global thread ID.  */
 struct thread_info *find_thread_global_id (int global_id);
 
+/* Find thread by thread library specific handle in inferior INF.  */
+struct thread_info *find_thread_by_handle (struct value *thread_handle,
+					   struct inferior *inf);
+
 /* Finds the first thread of the inferior given by PID.  If PID is -1,
    returns the first thread in the list.  */
 struct thread_info *first_thread_of_process (int pid);

gdb/linux-thread-db.c

@@ -1410,6 +1410,37 @@ thread_db_extra_thread_info (struct target_ops *self,
   return NULL;
 }
 
+/* Return pointer to the thread_info struct which corresponds to
+   THREAD_HANDLE (having length HANDLE_LEN).  */
+
+static struct thread_info *
+thread_db_thread_handle_to_thread_info (struct target_ops *ops,
+					const gdb_byte *thread_handle,
+					int handle_len,
+					struct inferior *inf)
+{
+  struct thread_info *tp;
+  thread_t handle_tid;
+
+  /* Thread handle sizes must match in order to proceed.  We don't use an
+     assert here because the resulting internal error will cause GDB to
+     exit.  This isn't necessarily an internal error due to the possibility
+     of garbage being passed as the thread handle via the python interface.  */
+  if (handle_len != sizeof (handle_tid))
+    error (_("Thread handle size mismatch: %d vs %zu (from libthread_db)"),
+	   handle_len, sizeof (handle_tid));
+
+  handle_tid = * (const thread_t *) thread_handle;
+
+  ALL_NON_EXITED_THREADS (tp)
+    {
+      if (tp->inf == inf && tp->priv != NULL && handle_tid == tp->priv->tid)
+        return tp;
+    }
+
+  return NULL;
+}
+
 /* Get the address of the thread local variable in load module LM which
    is stored at OFFSET within the thread local storage for thread PTID.  */
 
@@ -1691,6 +1722,7 @@ init_thread_db_ops (void)
     = thread_db_get_thread_local_address;
   thread_db_ops.to_extra_thread_info = thread_db_extra_thread_info;
   thread_db_ops.to_get_ada_task_ptid = thread_db_get_ada_task_ptid;
+  thread_db_ops.to_thread_handle_to_thread_info = thread_db_thread_handle_to_thread_info;
   thread_db_ops.to_magic = OPS_MAGIC;
 
   complete_target_initialization (&thread_db_ops);

gdb/target-delegates.c

@@ -1583,6 +1583,39 @@ debug_thread_name (struct target_ops *self, struct thread_info *arg1)
   return result;
 }
 
+static struct thread_info *
+delegate_thread_handle_to_thread_info (struct target_ops *self, const gdb_byte *arg1, int arg2, struct inferior *arg3)
+{
+  self = self->beneath;
+  return self->to_thread_handle_to_thread_info (self, arg1, arg2, arg3);
+}
+
+static struct thread_info *
+tdefault_thread_handle_to_thread_info (struct target_ops *self, const gdb_byte *arg1, int arg2, struct inferior *arg3)
+{
+  return NULL;
+}
+
+static struct thread_info *
+debug_thread_handle_to_thread_info (struct target_ops *self, const gdb_byte *arg1, int arg2, struct inferior *arg3)
+{
+  struct thread_info * result;
+  fprintf_unfiltered (gdb_stdlog, "-> %s->to_thread_handle_to_thread_info (...)\n", debug_target.to_shortname);
+  result = debug_target.to_thread_handle_to_thread_info (&debug_target, arg1, arg2, arg3);
+  fprintf_unfiltered (gdb_stdlog, "<- %s->to_thread_handle_to_thread_info (", debug_target.to_shortname);
+  target_debug_print_struct_target_ops_p (&debug_target);
+  fputs_unfiltered (", ", gdb_stdlog);
+  target_debug_print_const_gdb_byte_p (arg1);
+  fputs_unfiltered (", ", gdb_stdlog);
+  target_debug_print_int (arg2);
+  fputs_unfiltered (", ", gdb_stdlog);
+  target_debug_print_struct_inferior_p (arg3);
+  fputs_unfiltered (") = ", gdb_stdlog);
+  target_debug_print_struct_thread_info_p (result);
+  fputs_unfiltered ("\n", gdb_stdlog);
+  return result;
+}
+
 static void
 delegate_stop (struct target_ops *self, ptid_t arg1)
 {
@@ -4267,6 +4300,8 @@ install_delegators (struct target_ops *ops)
     ops->to_extra_thread_info = delegate_extra_thread_info;
   if (ops->to_thread_name == NULL)
     ops->to_thread_name = delegate_thread_name;
+  if (ops->to_thread_handle_to_thread_info == NULL)
+    ops->to_thread_handle_to_thread_info = delegate_thread_handle_to_thread_info;
   if (ops->to_stop == NULL)
     ops->to_stop = delegate_stop;
   if (ops->to_interrupt == NULL)
@@ -4522,6 +4557,7 @@ install_dummy_methods (struct target_ops *ops)
   ops->to_pid_to_str = default_pid_to_str;
   ops->to_extra_thread_info = tdefault_extra_thread_info;
   ops->to_thread_name = tdefault_thread_name;
+  ops->to_thread_handle_to_thread_info = tdefault_thread_handle_to_thread_info;
   ops->to_stop = tdefault_stop;
   ops->to_interrupt = tdefault_interrupt;
   ops->to_pass_ctrlc = default_target_pass_ctrlc;
@@ -4681,6 +4717,7 @@ init_debug_target (struct target_ops *ops)
   ops->to_pid_to_str = debug_pid_to_str;
   ops->to_extra_thread_info = debug_extra_thread_info;
   ops->to_thread_name = debug_thread_name;
+  ops->to_thread_handle_to_thread_info = debug_thread_handle_to_thread_info;
   ops->to_stop = debug_stop;
   ops->to_interrupt = debug_interrupt;
   ops->to_pass_ctrlc = debug_pass_ctrlc;

gdb/target.c

@@ -2244,6 +2244,15 @@ target_thread_name (struct thread_info *info)
   return current_target.to_thread_name (&current_target, info);
 }
 
+struct thread_info *
+target_thread_handle_to_thread_info (const gdb_byte *thread_handle,
+				     int handle_len,
+				     struct inferior *inf)
+{
+  return current_target.to_thread_handle_to_thread_info
+           (&current_target, thread_handle, handle_len, inf);
+}
+
 void
 target_resume (ptid_t ptid, int step, enum gdb_signal signal)
 {

gdb/target.h

@@ -644,6 +644,11 @@ struct target_ops
       TARGET_DEFAULT_RETURN (NULL);
     const char *(*to_thread_name) (struct target_ops *, struct thread_info *)
       TARGET_DEFAULT_RETURN (NULL);
+    struct thread_info *(*to_thread_handle_to_thread_info) (struct target_ops *,
+                                                            const gdb_byte *,
+							    int,
+							    struct inferior *inf)
+      TARGET_DEFAULT_RETURN (NULL);
     void (*to_stop) (struct target_ops *, ptid_t)
       TARGET_DEFAULT_IGNORE ();
     void (*to_interrupt) (struct target_ops *, ptid_t)
@@ -1828,6 +1833,12 @@ extern const char *normal_pid_to_str (ptid_t ptid);
 
 extern const char *target_thread_name (struct thread_info *);
 
+/* Given a pointer to a thread library specific thread handle and
+   its length, return a pointer to the corresponding thread_info struct.  */
+
+extern struct thread_info *target_thread_handle_to_thread_info
+  (const gdb_byte *thread_handle, int handle_len, struct inferior *inf);
+
 /* Attempts to find the pathname of the executable file
    that was run to create a specified process.
 

gdb/thread.c

@@ -519,6 +519,7 @@ find_thread_id (struct inferior *inf, int thr_num)
 }
 
 /* Find a thread_info by matching PTID.  */
+
 struct thread_info *
 find_thread_ptid (ptid_t ptid)
 {
@@ -531,6 +532,17 @@ find_thread_ptid (ptid_t ptid)
   return NULL;
 }
 
+/* See gdbthread.h.  */
+
+struct thread_info *
+find_thread_by_handle (struct value *thread_handle, struct inferior *inf)
+{
+  return target_thread_handle_to_thread_info
+	   (value_contents_all (thread_handle),
+	    TYPE_LENGTH (value_type (thread_handle)),
+	    inf);
+}
+
 /*
  * Thread iterator function.
  *