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Re: [Qemu-devel] [PATCH v9 15/27] gdbstub: Implement file io (F pkt) wit


From: Alex Bennée
Subject: Re: [Qemu-devel] [PATCH v9 15/27] gdbstub: Implement file io (F pkt) with new infra
Date: Wed, 15 May 2019 17:54:35 +0100
User-agent: mu4e 1.3.1; emacs 26.1

Jon Doron <address@hidden> writes:

There is a bit more going on here than a simple conversion. I think we
need some additional commentary about the format of the data coming
back.


> Signed-off-by: Jon Doron <address@hidden>
> ---
>  gdbstub.c | 62 +++++++++++++++++++++++++++++++++++--------------------
>  1 file changed, 40 insertions(+), 22 deletions(-)
>
> diff --git a/gdbstub.c b/gdbstub.c
> index 3478ac778d..9fe130f30d 100644
> --- a/gdbstub.c
> +++ b/gdbstub.c
> @@ -1772,6 +1772,39 @@ static void handle_read_all_regs(GdbCmdContext 
> *gdb_ctx, void *user_ctx)
>      put_packet(gdb_ctx->s, gdb_ctx->str_buf);
>  }
>
> +static void handle_file_io(GdbCmdContext *gdb_ctx, void *user_ctx)
> +{
> +    int num_syscall_params;
> +    GdbCmdVariant syscall_params[3] = {};
> +
> +    if (!gdb_ctx->num_params) {
> +        return;
> +    }
> +
> +    if (cmd_parse_params(gdb_ctx->params[0].data, "L,L,o0", syscall_params,
> +                         &num_syscall_params)) {
> +        return;
> +    }

What's going on here? I thought the schema was meant to handle the
parsing of data. I see bellow we originally parse the command as a null
terminated string but we actually should handle:

  ‘Fretcode,errno,Ctrl-C flag;call-specific attachment’

I see the argument for dealing with the call-specific attachment here
but shouldn't the generic parsing code be able to split everything
apart?

> +
> +    if (!num_syscall_params) {
> +        return;
> +    }
> +
> +    if (gdb_ctx->s->current_syscall_cb) {
> +        gdb_ctx->s->current_syscall_cb(gdb_ctx->s->c_cpu,
> +                                       
> (target_ulong)syscall_params[0].val_ull,
> +                                       
> (target_ulong)syscall_params[1].val_ull);
> +        gdb_ctx->s->current_syscall_cb = NULL;
> +    }



> +
> +    if (syscall_params[2].opcode == (uint8_t)'C') {
> +        put_packet(gdb_ctx->s, "T02");
> +        return;
> +    }
> +
> +    gdb_continue(gdb_ctx->s);
> +}
> +
>  static int gdb_handle_packet(GDBState *s, const char *line_buf)
>  {
>      CPUState *cpu;
> @@ -1913,28 +1946,13 @@ static int gdb_handle_packet(GDBState *s, const char 
> *line_buf)
>          return RS_IDLE;
>      case 'F':
>          {
> -            target_ulong ret;
> -            target_ulong err;
> -
> -            ret = strtoull(p, (char **)&p, 16);
> -            if (*p == ',') {
> -                p++;
> -                err = strtoull(p, (char **)&p, 16);
> -            } else {
> -                err = 0;
> -            }
> -            if (*p == ',')
> -                p++;
> -            type = *p;
> -            if (s->current_syscall_cb) {
> -                s->current_syscall_cb(s->c_cpu, ret, err);
> -                s->current_syscall_cb = NULL;
> -            }
> -            if (type == 'C') {
> -                put_packet(s, "T02");
> -            } else {
> -                gdb_continue(s);
> -            }
> +            static const GdbCmdParseEntry file_io_cmd_desc = {
> +                .handler = handle_file_io,
> +                .cmd = "F",
> +                .cmd_startswith = 1,
> +                .schema = "s0"
> +            };
> +            cmd_parser = &file_io_cmd_desc;
>          }
>          break;
>      case 'g':


--
Alex Bennée



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