[1/2] Add GDB qAttached support

With this patch QEMU handles qAttached request from gdb. When QEMU
replies 1, GDB sends a "detach" command at the end of a debugging
session otherwise GDB sends "kill".

The default value for qAttached is 1 on system emulation and 0 on user
emulation.

We introduce a new command line option. It's a generic option to
customize the gdb server:

-gdb-opts [attached=on|off]

The only parameter for now is "attached".

This patch implements the requirement described in Jan Kiszka's patch:
"gdbstub: Do not kill target in system emulation mode". The patch can
therefore be reverted.

Signed-off-by: Fabien Chouteau <chouteau@adacore.com>
---
 gdbstub.c              |   38 +++++++++++++++++++++++++++++++++++++-
 include/exec/gdbstub.h |    2 ++
 qemu-options.hx        |   17 +++++++++++++++++
 vl.c                   |    3 +++
 4 files changed, 59 insertions(+), 1 deletion(-)

On 2013-03-12 15:31, Fabien Chouteau wrote:
> With this patch QEMU handles qAttached request from gdb. When QEMU
> replies 1, GDB sends a "detach" command at the end of a debugging
> session otherwise GDB sends "kill".
> 
> The default value for qAttached is 1 on system emulation and 0 on user
> emulation.
> 
> We introduce a new command line option. It's a generic option to
> customize the gdb server:

Again, please factor this out into a separate patch so that qAttached
can be merged independently (and we stop warning the gdb users
incorrectly about killing the target on quit).

> 
> -gdb-opts [attached=on|off]

This will still trigger additional discussions as it's still a new
top-level command line switch.

I think it is possible to merge chardev-unrelated options into the
parameter that -gdb takes and filter them out before handing the rest
over to the chardev layer.

Jan

> 
> The only parameter for now is "attached".
> 
> This patch implements the requirement described in Jan Kiszka's patch:
> "gdbstub: Do not kill target in system emulation mode". The patch can
> therefore be reverted.
> 
> Signed-off-by: Fabien Chouteau <chouteau@adacore.com>
> ---
>  gdbstub.c              |   38 +++++++++++++++++++++++++++++++++++++-
>  include/exec/gdbstub.h |    2 ++
>  qemu-options.hx        |   17 +++++++++++++++++
>  vl.c                   |    3 +++
>  4 files changed, 59 insertions(+), 1 deletion(-)
> 
> diff --git a/gdbstub.c b/gdbstub.c
> index e414ad9..de95849 100644
> --- a/gdbstub.c
> +++ b/gdbstub.c
> @@ -32,7 +32,6 @@
>  #include "monitor/monitor.h"
>  #include "char/char.h"
>  #include "sysemu/sysemu.h"
> -#include "exec/gdbstub.h"
>  #endif
>  
>  #define MAX_PACKET_LENGTH 4096
> @@ -41,6 +40,13 @@
>  #include "qemu/sockets.h"
>  #include "sysemu/kvm.h"
>  #include "qemu/bitops.h"
> +#include "exec/gdbstub.h"
> +
> +#ifdef CONFIG_USER_ONLY
> +static bool gdb_attached; /* false */
> +#else
> +static bool gdb_attached = true;
> +#endif
>  
>  #ifndef TARGET_CPU_MEMORY_RW_DEBUG
>  static inline int target_memory_rw_debug(CPUArchState *env, target_ulong addr,
> @@ -2491,6 +2497,10 @@ 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;
> +        }
>          /* Unrecognised 'q' command.  */
>          goto unknown_command;
>  
> @@ -3055,3 +3065,29 @@ int gdbserver_start(const char *device)
>      return 0;
>  }
>  #endif
> +
> +static QemuOptsList qemu_gdb_opts = {
> +    .name = "gdb",
> +    .head = QTAILQ_HEAD_INITIALIZER(qemu_gdb_opts.head),
> +    .desc = {
> +        {
> +            .name = "attached",
> +            .type = QEMU_OPT_BOOL,
> +        },
> +        { /* end of list */ }
> +    },
> +};
> +
> +void gdb_set_opts(const char *opts_str)
> +{
> +    QemuOpts *opts;
> +
> +    opts = qemu_opts_parse(&qemu_gdb_opts, opts_str, 0);
> +    if (!opts) {
> +        exit(1);
> +    }
> +
> +    gdb_attached = qemu_opt_get_bool(opts, "attached", gdb_attached);
> +
> +    qemu_opts_del(opts);
> +}
> diff --git a/include/exec/gdbstub.h b/include/exec/gdbstub.h
> index ba20afa..86fc18b 100644
> --- a/include/exec/gdbstub.h
> +++ b/include/exec/gdbstub.h
> @@ -50,4 +50,6 @@ int gdbserver_start(const char *port);
>  /* in gdbstub-xml.c, generated by scripts/feature_to_c.sh */
>  extern const char *const xml_builtin[][2];
>  
> +void gdb_set_opts(const char *opts_str);
> +
>  #endif
> diff --git a/qemu-options.hx b/qemu-options.hx
> index cd76f2a..49a480f 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -2505,6 +2505,23 @@ within gdb and establish the connection via a pipe:
>  @end example
>  ETEXI
>  
> +DEF("gdb-opts", HAS_ARG, QEMU_OPTION_gdb_opts, \
> +    "-gdb-opts attached=on|off\n"\
> +    "                options for the gdb remote server\n", QEMU_ARCH_ALL)
> +STEXI
> +@item -gdb-opts @var{dev}
> +@findex -gdb-opts
> +Set options for the gdb remote server:
> +@table @option
> +@item attached=on|off:
> +
> +When 'on' (default), gdb sends a 'detach' command at the end of debugging
> +session, otherwise gdb sends a 'kill' command.
> +
> +@end table
> +
> +ETEXI
> +
>  DEF("s", 0, QEMU_OPTION_s, \
>      "-s              shorthand for -gdb tcp::" DEFAULT_GDBSTUB_PORT "\n",
>      QEMU_ARCH_ALL)
> diff --git a/vl.c b/vl.c
> index 154f7ba..cce96b6 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -3251,6 +3251,9 @@ int main(int argc, char **argv, char **envp)
>              case QEMU_OPTION_gdb:
>                  add_device_config(DEV_GDB, optarg);
>                  break;
> +            case QEMU_OPTION_gdb_opts:
> +                gdb_set_opts(optarg);
> +                break;
>              case QEMU_OPTION_L:
>                  data_dir = optarg;
>                  break;
>