Re: [Qemu-devel] [PATCH 1/2] Add GDB qAttached support

[Fabien Chouteau <chouteau@adacore.com>]

On 03/10/2013 09:06 AM, Jan Kiszka wrote:
>> @@ -2491,6 +2493,10 @@ static int gdb_handle_packet(GDBState *s, const char *line_buf)
>>              break;
>>          }
>>  #endif
>> +        if (strncmp(p, "Attached", 8) == 0) {
>> +            put_packet(s, gdb_attached ? "1" : "0");
>> +            break;
>> +        }
>
> This works as expected for system mode, but now inverts the behaviour
> for user mode - that's unexpected and not ok.
>

OK, I can change the default value for user mode.

>> diff --git a/qemu-options.hx b/qemu-options.hx
>> index 6f9334a..026d3eb 100644
>> --- a/qemu-options.hx
>> +++ b/qemu-options.hx
>> @@ -2988,6 +2988,13 @@ property must be set.  These objects are placed in the
>>  '/objects' path.
>>  ETEXI
>>
>> +DEF("gdb-not-attached", 0, QEMU_OPTION_gdb_not_attached,
>> +    "-gdb-not-attached\n"
>> +    "                Do not set Gdb remote server in attached mode.\n"
>> +    "                When exiting debugging session, Gdb will send a 'kill'\n"
>> +    "                command instead of a 'detach'.\n",
>> +    QEMU_ARCH_ALL)
>> +
>
> First of all, why do we need this configurable? In which use cases do
> you want attached mode for user emulation or kill mode for system
> emulation/virtualization?
>

It's more convenient for us, we expect QEMU to terminate at the end of
debugging session because we do not run big systems/kernels but short
test programs. It used to be the default behavior of QEMU, and our
test-suites, IDE, developers and users are expecting this.

> Then, if you can convince us that such a switch is useful, a new
> top-level command line option is still a no-go. We already have -gdb, so
> this would have to become an option to it.
>

Something like:

-gdb dev[,attached=on|off]        wait for gdb connection on 'dev'

This will not fit nicely in the current option because 'dev' is a
chardev descriptor. I will have to add 'attached' in the list of chardev
opts, which is not correct. Or do some nasty strings manipulation.

Maybe this:

-gdb-opts attached=on|off

We can extend it latter if more options are needed.

> In any case, I would suggest to add static attached mode first (enabled
> for system, disable for user), revert my patch and then, optionally,
> propose an attached mode control.
>

Mode control is not optional for me.

Regards,

-- 
Fabien Chouteau