scripts: add gdb support script

Add a script that enhances gdb to be aware of QEMU data structures.

This patch adds a single gdb command, 'qemu mtree'.  The command is
similar to the monitor's 'info mtree', except that it prints MemoryRegion
addresses, and except for working from a core dump as well as a live instance.

Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>

scripts/qemu-gdb.py

@@ -0,0 +1,89 @@
+#!/usr/bin/python
+
+# GDB debugging support
+#
+# Copyright 2012 Red Hat, Inc. and/or its affiliates
+#
+# Authors:
+#  Avi Kivity <avi@redhat.com>
+#
+# This work is licensed under the terms of the GNU GPL, version 2.  See
+# the COPYING file in the top-level directory.
+#
+# Contributions after 2012-01-13 are licensed under the terms of the
+# GNU GPL, version 2 or (at your option) any later version.
+
+
+import gdb
+
+def isnull(ptr):
+    return ptr == gdb.Value(0).cast(ptr.type)
+
+def int128(p):
+    return long(p['lo']) + (long(p['hi']) << 64)
+
+class QemuCommand(gdb.Command):
+    '''Prefix for QEMU debug support commands'''
+    def __init__(self):
+        gdb.Command.__init__(self, 'qemu', gdb.COMMAND_DATA,
+                             gdb.COMPLETE_NONE, True)
+
+class MtreeCommand(gdb.Command):
+    '''Display the memory tree hierarchy'''
+    def __init__(self):
+        gdb.Command.__init__(self, 'qemu mtree', gdb.COMMAND_DATA,
+                             gdb.COMPLETE_NONE)
+        self.queue = []
+    def invoke(self, arg, from_tty):
+        self.seen = set()
+        self.queue_root('address_space_memory')
+        self.queue_root('address_space_io')
+        self.process_queue()
+    def queue_root(self, varname):
+        ptr = gdb.parse_and_eval(varname)['root']
+        self.queue.append(ptr)
+    def process_queue(self):
+        while self.queue:
+            ptr = self.queue.pop(0)
+            if long(ptr) in self.seen:
+                continue
+            self.print_item(ptr)
+    def print_item(self, ptr, offset = gdb.Value(0), level = 0):
+        self.seen.add(long(ptr))
+        addr = ptr['addr']
+        addr += offset
+        size = int128(ptr['size'])
+        alias = ptr['alias']
+        klass = ''
+        if not isnull(alias):
+            klass = ' (alias)'
+        elif not isnull(ptr['ops']):
+            klass = ' (I/O)'
+        elif bool(ptr['ram']):
+            klass = ' (RAM)'
+        gdb.write('%s%016x-%016x %s%s (@ %s)\n'
+                  % ('  ' * level,
+                     long(addr),
+                     long(addr + (size - 1)),
+                     ptr['name'].string(),
+                     klass,
+                     ptr,
+                     ),
+                  gdb.STDOUT)
+        if not isnull(alias):
+            gdb.write('%s    alias: %s@%016x (@ %s)\n' %
+                      ('  ' * level,
+                       alias['name'].string(),
+                       ptr['alias_offset'],
+                       alias,
+                       ),
+                      gdb.STDOUT)
+            self.queue.append(alias)
+        subregion = ptr['subregions']['tqh_first']
+        level += 1
+        while not isnull(subregion):
+            self.print_item(subregion, addr, level)
+            subregion = subregion['subregions_link']['tqe_next']
+
+QemuCommand()
+MtreeCommand()