Re: [Qemu-devel] [PATCH 5/5] HMP: Introduce console command

[Luiz Capitulino <lcapitulino@redhat.com>]

On Wed, 24 Oct 2012 15:17:21 +0800
Lei Li <lilei@linux.vnet.ibm.com> wrote:

> On 10/23/2012 02:59 AM, Luiz Capitulino wrote:
> > On Mon, 22 Oct 2012 00:48:01 +0800
> > Lei Li <lilei@linux.vnet.ibm.com> wrote:
> >
> >> Signed-off-by: Lei Li <lilei@linux.vnet.ibm.com>
> >> ---
> >>   hmp-commands.hx |   23 +++++++++++++++++++++++
> >>   hmp.c           |   53 +++++++++++++++++++++++++++++++++++++++++++++++++++++
> >>   hmp.h           |    1 +
> >>   monitor.c       |   15 +++++++++++++++
> >>   monitor.h       |    3 +++
> >>   5 files changed, 95 insertions(+), 0 deletions(-)
> >>
> >> diff --git a/hmp-commands.hx b/hmp-commands.hx
> >> index 5f91428..f862a53 100644
> >> --- a/hmp-commands.hx
> >> +++ b/hmp-commands.hx
> >> @@ -868,7 +868,30 @@ char device and return @var{size} of the data.
> >>   that specifies behavior when the queue is full/empty. By default is
> >>   'drop'. Note that the 'block' option is not supported now.
> >>           -b for 'block' option. None for 'drop' option.
> >> +ETEXI
> >> +
> >> +    {
> >> +        .name       = "console",
> >> +        .args_type  = "chardev:s",
> >> +        .params     = "chardev",
> >> +        .help       = "Connect to the serial console from within the"
> >> +                      "monitor, allow to write data to memchardev"
> >> +                      "'chardev'. Exit from the console and return back"
> >> +                      "to monitor by typing 'ctrl-]'",
> >> +        .mhandler.cmd = hmp_console,
> >> +    },
> >>   
> >> +STEXI
> >> +@item console @var{device}
> >> +@findex console
> >> +
> >> +Connect to the serial console from within the monitor, allow to write data
> >> +to memchardev @var{chardev}. Exit from the console and return back to
> >> +monitor by typing 'ctrl-]'.
> >> +@example
> >> +(qemu) console foo
> >> +foo: data string...
> >> +@end example
> >>   ETEXI
> >>   
> >>       {
> >> diff --git a/hmp.c b/hmp.c
> >> index fa858c4..bc245f4 100644
> >> --- a/hmp.c
> >> +++ b/hmp.c
> >> @@ -1245,3 +1245,56 @@ void hmp_screen_dump(Monitor *mon, const QDict *qdict)
> >>       qmp_screendump(filename, &err);
> >>       hmp_handle_error(mon, &err);
> >>   }
> >> +
> >> +enum escape_char
> >> +{
> >> +    ESCAPE_CHAR_CTRL_GS = 0x1d  /* ctrl-] used for escape */
> >> +};
> >> +
> >> +static void hmp_read_console(Monitor *mon, const char *data,
> >> +                             void *opaque)
> >> +{
> >> +    CharDriverState *chr = opaque;
> >> +    uint32_t size = strlen(data);
> >> +    enum DataFormat format = DATA_FORMAT_UTF8;
> >> +    enum CongestionControl control = CONGESTION_CONTROL_DROP;
> >> +    enum escape_char console_escape = ESCAPE_CHAR_CTRL_GS;
> >> +
> >> +    Error *err = NULL;
> >> +
> >> +    if (*data == console_escape) {
> >> +        monitor_resume(mon);
> >> +        return;
> >> +    }
> >> +
> >> +    qmp_memchar_write(chr->label, size, data, 0, format,
> >> +                      0, control, &err);
> >> +    if (err) {
> >> +        monitor_printf(mon, "%s\n", error_get_pretty(err));
> >> +        error_free(err);
> >> +        return;
> >> +    }
> > Shouldn't you also read from the device?
> 
> The use-case for this console command is just allow the user to
> write data to each memchar device as in a signal terminal. Then
> type escape sequences to take you back to the monitor. So I don't
> think it is also need to read from the device in this command.
> 
> BTW, we can read from the device by hmp_memchar_read. :)

And how is the console command better than the hmp_memchar_write one?

Could you please give examples?

> >> +
> >> +    monitor_read_command(mon, 1);
> >> +}
> >> +
> >> +void hmp_console(Monitor *mon, const QDict *qdict)
> >> +{
> >> +    const char *device = qdict_get_str(qdict, "chardev");
> >> +    CharDriverState *chr;
> >> +    Error *err = NULL;
> >> +
> >> +    chr = qemu_chr_find(device);
> >> +
> >> +    if (!chr) {
> >> +        error_set(&err, QERR_DEVICE_NOT_FOUND, device);
> >> +        goto out;
> >> +    }
> > No need to do this here as the QMP command will do it too.
> >
> I think we should do this check here, otherwise would
> cause core dump when 'console' to a chardev that does not
> exist. Wepass parameterchr->label by qmp_memchar_write()
> in the handler hmp_read_console.

Do you need the chr object? Why don't you just pass 'device' to
monitor_read_console()?

> 
> >> +
> >> +    if (monitor_read_console(mon, device, hmp_read_console, chr) < 0) {
> >> +        monitor_printf(mon, "Connect to console %s failed\n", device);
> >> +    }
> >> +
> >> +out:
> >> +    hmp_handle_error(mon, &err);
> >> +}
> >> diff --git a/hmp.h b/hmp.h
> >> index a5a0cfe..5b54a79 100644
> >> --- a/hmp.h
> >> +++ b/hmp.h
> >> @@ -77,5 +77,6 @@ void hmp_getfd(Monitor *mon, const QDict *qdict);
> >>   void hmp_closefd(Monitor *mon, const QDict *qdict);
> >>   void hmp_send_key(Monitor *mon, const QDict *qdict);
> >>   void hmp_screen_dump(Monitor *mon, const QDict *qdict);
> >> +void hmp_console(Monitor *mon, const QDict *qdict);
> >>   
> >>   #endif
> >> diff --git a/monitor.c b/monitor.c
> >> index 131b325..453c084 100644
> >> --- a/monitor.c
> >> +++ b/monitor.c
> >> @@ -256,6 +256,21 @@ int monitor_read_password(Monitor *mon, ReadLineFunc *readline_func,
> >>       }
> >>   }
> >>   
> >> +int monitor_read_console(Monitor *mon, const char *device,
> >> +                         ReadLineFunc *readline_func, void *opaque)
> >> +{
> >> +    char prompt[60];
> >> +
> >> +    if (!mon->rs) {
> >> +        return -1;
> >> +    }
> >> +
> >> +    snprintf(prompt, sizeof(prompt), "%s: ", device);
> >> +    readline_start(mon->rs, prompt, 0, readline_func, opaque);
> >> +
> >> +    return 0;
> >> +}
> >> +
> >>   void monitor_flush(Monitor *mon)
> >>   {
> >>       if (mon && mon->outbuf_index != 0 && !mon->mux_out) {
> >> diff --git a/monitor.h b/monitor.h
> >> index b6e7d95..735bd1b 100644
> >> --- a/monitor.h
> >> +++ b/monitor.h
> >> @@ -86,6 +86,9 @@ ReadLineState *monitor_get_rs(Monitor *mon);
> >>   int monitor_read_password(Monitor *mon, ReadLineFunc *readline_func,
> >>                             void *opaque);
> >>   
> >> +int monitor_read_console(Monitor *mon, const char *device,
> >> +                         ReadLineFunc *readline_func, void *opaque);
> >> +
> >>   int qmp_qom_set(Monitor *mon, const QDict *qdict, QObject **ret);
> >>   
> >>   int qmp_qom_get(Monitor *mon, const QDict *qdict, QObject **ret);
> >
> 
>