On 02/05/2019 10:44, David Gibson wrote:
> On Wed, May 01, 2019 at 03:35:21PM +1000, Suraj Jitindar Singh wrote:
>> Add a monitor command "dump-stack" to be used to dump the stack for the
>> current cpu.
>
> So, you can already get guest backtraces by using the gdbstub
Not in the field - this requires QEMU to run with -s which is not
usually the case.
But since we almost always deal with QEMUs run by libvirt and HMP/QMP is
always available, one could write a script doing QMP's
"human-monitor-command x/16g" or "virsh qemu-monitor-command --hmp
x/16g" to read the guest memory and MSR:LE and dump the stack with the
exception frame.
> functionality. I can see some benefit in allowing this more easily
> through hmp, but whether it's worth the code size, I'm less certain.
It still seems easier than running an external script talking to HMP/QMP
as you would not want to write such script in bash but rather in a
better language which might not be installed on the client machine (like
missing python3 on many RHEL :) ). Thanks,
>>
>> Signed-off-by: Suraj Jitindar Singh <sjitindarsi...@gmail.com>
>> ---
>> hmp-commands.hx | 13 +++++++++++++
>> hmp.h | 1 +
>> include/qom/cpu.h | 10 ++++++++++
>> monitor.c | 12 ++++++++++++
>> qom/cpu.c | 10 ++++++++++
>> 5 files changed, 46 insertions(+)
>>
>> diff --git a/hmp-commands.hx b/hmp-commands.hx
>> index 9b4035965c..965ccdea28 100644
>> --- a/hmp-commands.hx
>> +++ b/hmp-commands.hx
>> @@ -862,6 +862,19 @@ ETEXI
>> },
>>
>> STEXI
>> +@item dump-stack
>> +@findex dump-stack
>> +dump stack of the cpu
>> +ETEXI
>> + {
>> + .name = "dump-stack",
>> + .args_type = "",
>> + .params = "",
>> + .help = "dump stack",
>> + .cmd = hmp_dumpstack,
>> + },
>> +
>> +STEXI
>> @item pmemsave @var{addr} @var{size} @var{file}
>> @findex pmemsave
>> save to disk physical memory dump starting at @var{addr} of size @var{size}.
>> diff --git a/hmp.h b/hmp.h
>> index 43617f2646..e6edf1215c 100644
>> --- a/hmp.h
>> +++ b/hmp.h
>> @@ -51,6 +51,7 @@ void hmp_announce_self(Monitor *mon, const QDict *qdict);
>> void hmp_cpu(Monitor *mon, const QDict *qdict);
>> void hmp_memsave(Monitor *mon, const QDict *qdict);
>> void hmp_pmemsave(Monitor *mon, const QDict *qdict);
>> +void hmp_dumpstack(Monitor *mon, const QDict *qdict);
>> void hmp_ringbuf_write(Monitor *mon, const QDict *qdict);
>> void hmp_ringbuf_read(Monitor *mon, const QDict *qdict);
>> void hmp_cont(Monitor *mon, const QDict *qdict);
>> diff --git a/include/qom/cpu.h b/include/qom/cpu.h
>> index 08abcbd3fe..f2e83e9918 100644
>> --- a/include/qom/cpu.h
>> +++ b/include/qom/cpu.h
>> @@ -181,6 +181,7 @@ typedef struct CPUClass {
>> int (*memory_rw_debug)(CPUState *cpu, vaddr addr,
>> uint8_t *buf, int len, bool is_write);
>> void (*dump_state)(CPUState *cpu, FILE *, int flags);
>> + void (*dump_stack)(CPUState *cpu, FILE *f);
>> GuestPanicInformation* (*get_crash_info)(CPUState *cpu);
>> void (*dump_statistics)(CPUState *cpu, int flags);
>> int64_t (*get_arch_id)(CPUState *cpu);
>> @@ -568,6 +569,15 @@ enum CPUDumpFlags {
>> void cpu_dump_state(CPUState *cpu, FILE *f, int flags);
>>
>> /**
>> + * cpu_dump_stack:
>> + * @cpu: The CPU whose stack is to be dumped.
>> + * @f: If non-null, dump to this stream, else to current print sink.
>> + *
>> + * Dumps CPU stack.
>> + */
>> +void cpu_dump_stack(CPUState *cpu, FILE *f);
>> +
>> +/**
>> * cpu_dump_statistics:
>> * @cpu: The CPU whose state is to be dumped.
>> * @flags: Flags what to dump.
>> diff --git a/monitor.c b/monitor.c
>> index 9b5f10b475..dbec2e4376 100644
>> --- a/monitor.c
>> +++ b/monitor.c
>> @@ -1299,6 +1299,18 @@ static void hmp_info_registers(Monitor *mon, const
>> QDict *qdict)
>> }
>> }
>>
>> +void hmp_dumpstack(Monitor *mon, const QDict *qdict)
>> +{
>> + CPUState *cs = mon_get_cpu();
>> +
>> + if (!cs) {
>> + monitor_printf(mon, "No CPU available\n");
>> + return;
>> + }
>> +
>> + cpu_dump_stack(cs, NULL);
>> +}
>> +
>> #ifdef CONFIG_TCG
>> static void hmp_info_jit(Monitor *mon, const QDict *qdict)
>> {
>> diff --git a/qom/cpu.c b/qom/cpu.c
>> index 3c5493c96c..0dc10004f4 100644
>> --- a/qom/cpu.c
>> +++ b/qom/cpu.c
>> @@ -230,6 +230,16 @@ void cpu_dump_state(CPUState *cpu, FILE *f, int flags)
>> }
>> }
>>
>> +void cpu_dump_stack(CPUState *cpu, FILE *f)
>> +{
>> + CPUClass *cc = CPU_GET_CLASS(cpu);
>> +
>> + if (cc->dump_stack) {
>> + cpu_synchronize_state(cpu);
>> + cc->dump_stack(cpu, f);
>> + }
>> +}
>> +
>> void cpu_dump_statistics(CPUState *cpu, int flags)
>> {
>> CPUClass *cc = CPU_GET_CLASS(cpu);
>
--
Alexey