Re: [Qemu-arm] [Qemu-devel] [PATCH v2 10/15] gdbstub: add support for extended mode packet

[Luc Michel]

On 10/1/18 6:39 PM, Philippe Mathieu-Daudé wrote:
> Hi Luc,
> 
> On 01/10/2018 13:56, Luc Michel wrote:
>> Add support for the '!' extended mode packet. This is required for the
>> multiprocess extension.
>>
>> Signed-off-by: Luc Michel <address@hidden>
>> ---
>>  gdbstub.c | 3 +++
>>  1 file changed, 3 insertions(+)
>>
>> diff --git a/gdbstub.c b/gdbstub.c
>> index 299783b3b8..d372972dd3 100644
>> --- a/gdbstub.c
>> +++ b/gdbstub.c
>> @@ -1280,10 +1280,13 @@ static int gdb_handle_packet(GDBState *s, const char 
>> *line_buf)
>>      trace_gdbstub_io_command(line_buf);
>>  
>>      p = line_buf;
>>      ch = *p++;
>>      switch(ch) {
>> +    case '!':
>> +        put_packet(s, "OK");
> 
> Don't we want to also support the 'R' packet?
Hi Philippe,

Thank you for all you reviews!

I'm not sure about this one:
  - do you think calling qemu_system_reset() is the right thing to do?
  - what should we do in user mode? Is there a way to restart the
emulated binary?
  - Looking at the GDB sources, GDB seems to send an 'R' packet on the
"run" command. It starts by a "vKill;pid" packet, then a "vRun". If
"vRun" is not supported by the remote, it falls back to "R". So it seems
that if we want to support "run", we must also implement "vKill;pid",
which probably doesn't make much sense for QEMU. One possible
implementation that would probably work for system mode would be to:
      - do nothing on 'vKill;pid' packet
      - do not implement the 'vRun' packet
      - call qemu_system_reset() on 'R' packet
But it does not align well with the current 'k' packet behaviour, which
simply do an exit(0). Do you have an opinion on this?

Thanks.

Luc.

> 
>> +        break;
>>      case '?':
>>          /* TODO: Make this return the correct value for user-mode.  */
>>          snprintf(buf, sizeof(buf), "T%02xthread:%s;", GDB_SIGNAL_TRAP,
>>                   gdb_fmt_thread_id(s, s->c_cpu, thread_id, 
>> sizeof(thread_id)));
>>          put_packet(s, buf);
>>