scripts/gdb: add get_gdbserver_type helper

This helper probes the type of the gdb server.  Supported are QEMU and
KGDB so far.  Knowledge about the gdb server is required e.g.  to
retrieve the current CPU or current task.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Ben Widawsky <ben@bwidawsk.net>
Cc: Borislav Petkov <bp@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/gdb/linux/utils.py

@@ -119,3 +119,38 @@ def is_target_arch(arch):
         if target_arch is None:
             target_arch = gdb.execute("show architecture", to_string=True)
         return arch in target_arch
+
+
+GDBSERVER_QEMU = 0
+GDBSERVER_KGDB = 1
+gdbserver_type = None
+
+
+def get_gdbserver_type():
+    def exit_handler(event):
+        global gdbserver_type
+        gdbserver_type = None
+        gdb.events.exited.disconnect(exit_handler)
+
+    def probe_qemu():
+        try:
+            return gdb.execute("monitor info version", to_string=True) != ""
+        except:
+            return False
+
+    def probe_kgdb():
+        try:
+            thread_info = gdb.execute("info thread 2", to_string=True)
+            return "shadowCPU0" in thread_info
+        except:
+            return False
+
+    global gdbserver_type
+    if gdbserver_type is None:
+        if probe_qemu():
+            gdbserver_type = GDBSERVER_QEMU
+        elif probe_kgdb():
+            gdbserver_type = GDBSERVER_KGDB
+        if not gdbserver_type is None and hasattr(gdb, 'events'):
+            gdb.events.exited.connect(exit_handler)
+    return gdbserver_type