Display names of remote threads

This patch adds support for thread names in the remote protocol, and
updates gdb/gdbserver to use it.  The information is added to the XML
description sent in response to the qXfer:threads:read packet.

gdb/ChangeLog:

	* linux-nat.c (linux_nat_thread_name): Replace implementation by call
	to linux_proc_tid_get_name.
	* nat/linux-procfs.c (linux_proc_tid_get_name): New function,
	implementation inspired by linux_nat_thread_name.
	* nat/linux-procfs.h (linux_proc_tid_get_name): New declaration.
	* remote.c (struct private_thread_info) <name>: New field.
	(free_private_thread_info): Free name field.
	(remote_thread_name): New function.
	(thread_item_t) <name>: New field.
	(clear_threads_listing_context): Free name field.
	(start_thread): Get name xml attribute.
	(thread_attributes): Add "name" attribute.
	(remote_update_thread_list): Copy name field.
	(init_remote_ops): Assign remote_thread_name callback.
	* target.h (target_thread_name): Update comment.
	* NEWS: Mention remote thread name support.

gdb/gdbserver/ChangeLog:

	* linux-low.c (linux_target_ops): Use linux_proc_tid_get_name.
	* server.c (handle_qxfer_threads_worker): Refactor to include thread
	name in reply.
	* target.h (struct target_ops) <thread_name>: New field.
	(target_thread_name): New macro.

gdb/doc/ChangeLog:

	* gdb.texinfo (Thread List Format): Mention thread names.

2 files changed, 49 insertions, 0 deletions

diff --git a/gdb/nat/linux-procfs.c b/gdb/nat/linux-procfs.c
index 24bcb01..78cbb03 100644
--- a/gdb/nat/linux-procfs.c
+++ b/gdb/nat/linux-procfs.c
@@ -187,6 +187,48 @@ linux_proc_pid_is_zombie (pid_t pid)
 
 /* See linux-procfs.h.  */
 
+const char *
+linux_proc_tid_get_name (ptid_t ptid)
+{
+#define TASK_COMM_LEN 16  /* As defined in the kernel's sched.h.  */
+
+  static char comm_buf[TASK_COMM_LEN];
+  char comm_path[100];
+  FILE *comm_file;
+  const char *comm_val;
+  pid_t pid = ptid_get_pid (ptid);
+  pid_t tid = ptid_lwp_p (ptid) ? ptid_get_lwp (ptid) : ptid_get_pid (ptid);
+
+  xsnprintf (comm_path, sizeof (comm_path),
+	     "/proc/%ld/task/%ld/comm", (long) pid, (long) tid);
+
+  comm_file = gdb_fopen_cloexec (comm_path, "r");
+  if (comm_file == NULL)
+    return NULL;
+
+  comm_val = fgets (comm_buf, sizeof (comm_buf), comm_file);
+  fclose (comm_file);
+
+  if (comm_val != NULL)
+    {
+      int i;
+
+      /* Make sure there is no newline at the end.  */
+      for (i = 0; i < sizeof (comm_buf); i++)
+	{
+	  if (comm_buf[i] == '\n')
+	    {
+	      comm_buf[i] = '\0';
+	      break;
+	    }
+	}
+    }
+
+  return comm_val;
+}
+
+/* See linux-procfs.h.  */
+
 void
 linux_proc_attach_tgid_threads (pid_t pid,
 				linux_proc_attach_lwp_func attach_lwp)
diff --git a/gdb/nat/linux-procfs.h b/gdb/nat/linux-procfs.h
index f9cad39..f28c1ba 100644
--- a/gdb/nat/linux-procfs.h
+++ b/gdb/nat/linux-procfs.h
@@ -54,6 +54,13 @@ extern int linux_proc_pid_is_zombie_nowarn (pid_t pid);
 
 extern int linux_proc_pid_is_gone (pid_t pid);
 
+/* Return a string giving the thread's name or NULL if the
+   information is unavailable.  The returned value points to a statically
+   allocated buffer.  The value therefore becomes invalid at the next
+   linux_proc_tid_get_name call.  */
+
+extern const char *linux_proc_tid_get_name (ptid_t ptid);
+
 /* Callback function for linux_proc_attach_tgid_threads.  If the PTID
    thread is not yet known, try to attach to it and return true,
    otherwise return false.  */