Merge pull request #67 from arighi/drgn-support

virtme-ng: generate drgn compatible memory dumps

README.md

@@ -298,6 +298,26 @@ Examples
    (virtme-ng is started in graphical mode)
 ```
 
+ - Generate a memory dump of a running instance and read 'jiffies' from the
+   memory dump using the drgn debugger:
+````
+   # Start the vng instance in debug mode
+   $ vng --debug
+
+   # In a separate shell session trigger the memory dump to /tmp/vmcore.img
+   $ vng --dump /tmp/vmcore.img
+
+   # Use drgn to read 'jiffies' from the memory dump:
+   $ echo "print(prog['jiffies'])" | drgn -q -s vmlinux -c /tmp/vmcore.img
+   drgn 0.0.23 (using Python 3.11.6, elfutils 0.189, with libkdumpfile)
+   For help, type help(drgn).
+   >>> import drgn
+   >>> from drgn import NULL, Object, cast, container_of, execscript, offsetof, reinterpret, sizeof
+   >>> from drgn.helpers.common import *
+   >>> from drgn.helpers.linux import *
+   >>> (volatile unsigned long)4294675464
+```
+
  - Run virtme-ng inside a docker container:
 ```
    $ docker run -it ubuntu:22.04 /bin/bash

virtme/commands/configkernel.py

@@ -154,6 +154,9 @@ def arg_fail(message):
     "CONFIG_UPROBES=y",
     "CONFIG_UPROBE_EVENTS=y",
     "CONFIG_DEBUG_FS=y",
+    "# Required to generate memory dumps for drgn",
+    "CONFIG_FW_CFG_SYSFS=y",
+    "CONFIG_FW_CFG_SYSFS_CMDLINE=y",
     "# Graphics support",
     "CONFIG_DRM=y",
     "CONFIG_DRM_VIRTIO_GPU=y",

virtme_ng/run.py

@@ -856,7 +856,9 @@ def _get_virtme_sound(self, args):
             self.virtme_param["sound"] = ""
 
     def _get_virtme_disable_microvm(self, args):
-        if args.disable_microvm:
+        # Automatically disable microvm in debug mode, since it seems to
+        # produce incomplete memory dumps.
+        if args.disable_microvm or args.debug:
             self.virtme_param["disable_microvm"] = "--disable-microvm"
         else:
             self.virtme_param["disable_microvm"] = ""
@@ -951,7 +953,10 @@ def _get_virtme_qemu_opts(self, args):
         if args.qemu_opts is not None:
             qemu_args += " ".join(args.qemu_opts)
         if args.debug:
-            qemu_args += "-s -qmp tcp:localhost:3636,server,nowait"
+            # Enable vmcoreinfo (required by drgn memory dumps)
+            qemu_args += "-device vmcoreinfo "
+            # Enable debug mode and QMP (to trigger memory dump via `vng --dump`)
+            qemu_args += "-s -qmp tcp:localhost:3636,server,nowait "
         if qemu_args != "":
             self.virtme_param["qemu_opts"] = "--qemu-opts " + qemu_args
         else:
@@ -1032,11 +1037,6 @@ def run(self, args):
 
     def dump(self, args):
         """Generate or analyze a crash memory dump."""
-        if not os.path.isfile("vmlinux"):
-            arg_fail(
-                "vmlinux not found, try to recompile the kernel with "
-                + "--build-host-vmlinux (if --build-host was used)"
-            )
         # Use QMP to generate a memory dump
         sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
         sock.connect(("localhost", 3636))
@@ -1055,7 +1055,7 @@ def dump(self, args):
         with tempfile.NamedTemporaryFile(delete=dump_file is None) as tmp:
             msg = (
                 '{"execute":"dump-guest-memory",'
-                '"arguments":{"paging":false,'
+                '"arguments":{"paging":true,'
                 '"protocol":"file:' + tmp.name + '"}}'
                 "\r"
             )