----- Original Message ----- > On 12/12/17 17:35, Marc-André Lureau wrote:Hi > > 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. > > Can you state, "replace the object_resolve_path_type() function call > with an extern variable"?
ok > > > 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. > > Did you qualify them "volatile" too? > > E.g., in the vmcoreinfo_realize() function: > > static VMCoreInfoState * volatile vmcoreinfo_state; > ... > vmcoreinfo_state = s; > > (Note: it's the pointer itself that has to be volatile, not the > pointed-to object.) > > If you did try this, but GCC optimized it away, then that's a GCC bug. > In that case I guess I can't object to the present approach any longer. > Can you please confirm? > It seems to work, but you get a gcc warning: hw/misc/vmcoreinfo.c:38:39: warning: variable ‘vmcoreinfo_state’ set but not used [-Wunused-but-set-variable] I'll declare it like that and send v2: static VMCoreInfoState * volatile vmcoreinfo_state G_GNUC_UNUSED; > > > > Signed-off-by: Marc-André Lureau <marcandre.lur...@redhat.com> > > --- > > 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 = { > > > > Thanks! > Laszlo >