Re: [Qemu-devel] [PATCH v9 02/27] gdbstub: Implement deatch (D pkt) with new infra

[Alex Bennée]

Jon Doron <address@hidden> writes:

> Hi Alex, I implemented this change but i'm having second guesses on
> this, basically a NULL packet means the command is not supported (as
> far as i understand from the protocol documentation and implementation
> of GDB)
> That being said I think it's correct to send back a NULL packet if
> process_string_cmd fails for any reason, or you would prefer ill just
> omit it?
>
> Snippet of the change I did according to your review:
> -    if (cmd_parser &&
> -        process_string_cmd(s, NULL, line_buf, cmd_parser, 1)) {
> -        put_packet(s, "");
> +    if (!cmd_parser) {
> +        return RS_IDLE;
>      }
>
> +    process_string_cmd(s, NULL, line_buf, cmd_parser, 1);

OK I see your reasoning. So perhaps:

   if (cmd_parser) {
      /* helper will respond */
      process_string_cmd(s, NULL, line_buf, cmd_parser, 1)
   } else {
      /* unknown command, empty response */
      put_packet(s, "");
   }

   return RS_IDLE;
>
> -- Jon.
>
> On Tue, May 14, 2019 at 9:54 PM Alex Bennée <address@hidden> wrote:
>>
>>
>> Jon Doron <address@hidden> writes:
>>
>> > Signed-off-by: Jon Doron <address@hidden>
>> > ---
>> >  gdbstub.c | 90 ++++++++++++++++++++++++++++++-------------------------
>> >  1 file changed, 50 insertions(+), 40 deletions(-)
>> >
>> > diff --git a/gdbstub.c b/gdbstub.c
>> > index d5e0f3878a..621d689868 100644
>> > --- a/gdbstub.c
>> > +++ b/gdbstub.c
>> > @@ -1418,11 +1418,6 @@ static inline int startswith(const char *string, 
>> > const char *pattern)
>> >    return !strncmp(string, pattern, strlen(pattern));
>> >  }
>> >
>> > -static int process_string_cmd(
>> > -        GDBState *s, void *user_ctx, const char *data,
>> > -        const GdbCmdParseEntry *cmds, int num_cmds)
>> > -        __attribute__((unused));
>> > -
>> >  static int process_string_cmd(GDBState *s, void *user_ctx, const char 
>> > *data,
>> >                                const GdbCmdParseEntry *cmds, int num_cmds)
>> >  {
>> > @@ -1468,6 +1463,41 @@ static int process_string_cmd(GDBState *s, void 
>> > *user_ctx, const char *data,
>> >      return -1;
>> >  }
>> >
>> > +static void handle_detach(GdbCmdContext *gdb_ctx, void *user_ctx)
>> > +{
>> > +    GDBProcess *process;
>> > +    GDBState *s = gdb_ctx->s;
>> > +    uint32_t pid = 1;
>> > +
>> > +    if (s->multiprocess) {
>> > +        if (!gdb_ctx->num_params) {
>> > +            put_packet(s, "E22");
>> > +            return;
>> > +        }
>> > +
>> > +        pid = gdb_ctx->params[0].val_ul;
>> > +    }
>> > +
>> > +    process = gdb_get_process(s, pid);
>> > +    gdb_process_breakpoint_remove_all(s, process);
>> > +    process->attached = false;
>> > +
>> > +    if (pid == gdb_get_cpu_pid(s, s->c_cpu)) {
>> > +        s->c_cpu = gdb_first_attached_cpu(s);
>> > +    }
>> > +
>> > +    if (pid == gdb_get_cpu_pid(s, s->g_cpu)) {
>> > +        s->g_cpu = gdb_first_attached_cpu(s);
>> > +    }
>> > +
>> > +    if (!s->c_cpu) {
>> > +        /* No more process attached */
>> > +        gdb_syscall_mode = GDB_SYS_DISABLED;
>> > +        gdb_continue(s);
>> > +    }
>> > +    put_packet(s, "OK");
>> > +}
>> > +
>> >  static int gdb_handle_packet(GDBState *s, const char *line_buf)
>> >  {
>> >      CPUState *cpu;
>> > @@ -1482,6 +1512,7 @@ static int gdb_handle_packet(GDBState *s, const char 
>> > *line_buf)
>> >      uint8_t *registers;
>> >      target_ulong addr, len;
>> >      GDBThreadIdKind thread_kind;
>> > +    const GdbCmdParseEntry *cmd_parser = NULL;
>> >
>> >      trace_gdbstub_io_command(line_buf);
>> >
>> > @@ -1582,42 +1613,15 @@ static int gdb_handle_packet(GDBState *s, const 
>> > char *line_buf)
>> >          error_report("QEMU: Terminated via GDBstub");
>> >          exit(0);
>> >      case 'D':
>> > -        /* Detach packet */
>> > -        pid = 1;
>> > -
>> > -        if (s->multiprocess) {
>> > -            unsigned long lpid;
>> > -            if (*p != ';') {
>> > -                put_packet(s, "E22");
>> > -                break;
>> > -            }
>> > -
>> > -            if (qemu_strtoul(p + 1, &p, 16, &lpid)) {
>> > -                put_packet(s, "E22");
>> > -                break;
>> > -            }
>> > -
>> > -            pid = lpid;
>> > -        }
>> > -
>> > -        process = gdb_get_process(s, pid);
>> > -        gdb_process_breakpoint_remove_all(s, process);
>> > -        process->attached = false;
>> > -
>> > -        if (pid == gdb_get_cpu_pid(s, s->c_cpu)) {
>> > -            s->c_cpu = gdb_first_attached_cpu(s);
>> > -        }
>> > -
>> > -        if (pid == gdb_get_cpu_pid(s, s->g_cpu)) {
>> > -            s->g_cpu = gdb_first_attached_cpu(s);
>> > -        }
>> > -
>> > -        if (s->c_cpu == NULL) {
>> > -            /* No more process attached */
>> > -            gdb_syscall_mode = GDB_SYS_DISABLED;
>> > -            gdb_continue(s);
>> > +        {
>> > +            static const GdbCmdParseEntry detach_cmd_desc = {
>> > +                .handler = handle_detach,
>> > +                .cmd = "D",
>> > +                .cmd_startswith = 1,
>> > +                .schema = "?.l0"
>> > +            };
>> > +            cmd_parser = &detach_cmd_desc;
>> >          }
>> > -        put_packet(s, "OK");
>> >          break;
>> >      case 's':
>> >          if (*p != '\0') {
>> > @@ -1990,6 +1994,12 @@ static int gdb_handle_packet(GDBState *s, const 
>> > char *line_buf)
>> >          put_packet(s, buf);
>> >          break;
>> >      }
>> > +
>> > +    if (cmd_parser &&
>> > +        process_string_cmd(s, NULL, line_buf, cmd_parser, 1)) {
>> > +        put_packet(s, "");
>>
>> Why this null put_packet at the end? You've passed the handling of the
>> OK reply back to your handler so this seems superfluous.
>>
>> --
>> Alex Bennée


--
Alex Bennée