[Qemu-devel] [PATCH] dump-guest-memory.py: fix "You can't do that without a process to debug"

[Marc-André Lureau]

If the script is run with a core (no running process), it produces an
error:

(gdb)  dump-guest-memory /tmp/vmcore X86_64
guest RAM blocks:
target_start     target_end       host_addr        message count
---------------- ---------------- ---------------- ------- -----
0000000000000000 00000000000a0000 00007f7935800000 added       1
00000000000a0000 00000000000b0000 00007f7934200000 added       2
00000000000c0000 00000000000ca000 00007f79358c0000 added       3
00000000000ca000 00000000000cd000 00007f79358ca000 joined      3
00000000000cd000 00000000000e8000 00007f79358cd000 joined      3
00000000000e8000 00000000000f0000 00007f79358e8000 joined      3
00000000000f0000 0000000000100000 00007f79358f0000 joined      3
0000000000100000 0000000080000000 00007f7935900000 joined      3
00000000fd000000 00000000fe000000 00007f7934200000 added       4
00000000fffc0000 0000000100000000 00007f7935600000 added       5
Python Exception <class 'gdb.error'> You can't do that without a process to 
debug.:
Error occurred in Python command: You can't do that without a process
to debug.

Replace the function call with a variable. I tried to use static
function variables, as suggested by Laszlo in earlier reviews, but the
compiler always took the chance to optimize them away.

Signed-off-by: Marc-André Lureau <address@hidden>
---
 scripts/dump-guest-memory.py | 3 +--
 hw/misc/vmcoreinfo.c         | 4 ++++
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/scripts/dump-guest-memory.py b/scripts/dump-guest-memory.py
index 1af26c1a45..9dec796762 100644
--- a/scripts/dump-guest-memory.py
+++ b/scripts/dump-guest-memory.py
@@ -546,8 +546,7 @@ shape and this command should mostly work."""
         return None
 
     def add_vmcoreinfo(self):
-        vmci = '(VMCoreInfoState *)' + \
-               'object_resolve_path_type("", "vmcoreinfo", 0)'
+        vmci = 'vmcoreinfo_state'
         if not gdb.parse_and_eval("%s" % vmci) \
            or not gdb.parse_and_eval("(%s)->has_vmcoreinfo" % vmci):
             return
diff --git a/hw/misc/vmcoreinfo.c b/hw/misc/vmcoreinfo.c
index 31db57ab44..d429a4f7d6 100644
--- a/hw/misc/vmcoreinfo.c
+++ b/hw/misc/vmcoreinfo.c
@@ -31,6 +31,9 @@ static void vmcoreinfo_reset(void *dev)
     s->vmcoreinfo.host_format = cpu_to_le16(VMCOREINFO_FORMAT_ELF);
 }
 
+/* this variable is exported for gdb script dump-guest-memory.py */
+VMCoreInfoState *vmcoreinfo_state;
+
 static void vmcoreinfo_realize(DeviceState *dev, Error **errp)
 {
     VMCoreInfoState *s = VMCOREINFO(dev);
@@ -56,6 +59,7 @@ static void vmcoreinfo_realize(DeviceState *dev, Error **errp)
                              &s->vmcoreinfo, sizeof(s->vmcoreinfo), false);
 
     qemu_register_reset(vmcoreinfo_reset, dev);
+    vmcoreinfo_state = s;
 }
 
 static const VMStateDescription vmstate_vmcoreinfo = {
-- 
2.15.1.355.g36791d7216