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

[Jon Doron]

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);

-- 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