Message ID | 20171212163556.2543-1-marcandre.lureau@redhat.com |
---|---|
State | New |
Headers | show |
Series | dump-guest-memory.py: fix "You can't do that without a process to debug" | expand |
On 12/12/17 17:35, Marc-André Lureau wrote: > 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"? > 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? > > Signed-off-by: Marc-André Lureau <marcandre.lureau@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
----- 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.lureau@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 >
On 12/12/17 18:17, Marc-André Lureau wrote: > > > ----- 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; Awesome; thank you very much! (If "G_GNUC_UNUSED" is otherwise accepted practice in the QEMU tree; that is -- it does seem to be widely used.) ... please don't forget to update the commit message again (the variable will have block scope, static storage duration, and *no* linkage -- so it shouldn't be called "extern" like I originally suggested.) Cheers! Laszlo > >>> >>> Signed-off-by: Marc-André Lureau <marcandre.lureau@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 >>
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 = {
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 <marcandre.lureau@redhat.com> --- scripts/dump-guest-memory.py | 3 +-- hw/misc/vmcoreinfo.c | 4 ++++ 2 files changed, 5 insertions(+), 2 deletions(-)