Re: [PATCH v2 3/9] gdbstub: Add support for target-specific stubs

[Alex Bennée]

Gustavo Romero <gustavo.romero@linaro.org> writes:

> Currently, it's not possible to have stubs specific to a given target,
> even though there are GDB features which are target-specific, like, for
> instance, memory tagging.
>
> This commit introduces gdb_extend_qsupported_features,
> gdb_extend_query_table, and gdb_extend_set_table functions as interfaces
> to extend the qSupported string, the query handler table, and the set
> handler table, allowing target-specific stub implementations.
>
> Signed-off-by: Gustavo Romero <gustavo.romero@linaro.org>
> ---
>  gdbstub/gdbstub.c          | 59 ++++++++++++++++++++++++++++++++++----
>  include/gdbstub/commands.h | 22 ++++++++++++++
>  2 files changed, 75 insertions(+), 6 deletions(-)
>
> diff --git a/gdbstub/gdbstub.c b/gdbstub/gdbstub.c
> index 9ff2f4177d..e69cc5131e 100644
> --- a/gdbstub/gdbstub.c
> +++ b/gdbstub/gdbstub.c
> @@ -1609,6 +1609,12 @@ static void handle_query_thread_extra(GArray *params, 
> void *user_ctx)
>      gdb_put_strbuf();
>  }
>  
> +static char *extended_qsupported_features;
> +void gdb_extend_qsupported_features(char *qsupported_features)
> +{

Maybe g_assert(!extended_qsupported_features)?

> +    extended_qsupported_features = qsupported_features;
> +}
> +
>  static void handle_query_supported(GArray *params, void *user_ctx)
>  {
>      CPUClass *cc;
> @@ -1648,6 +1654,11 @@ static void handle_query_supported(GArray *params, 
> void *user_ctx)
>      }
>  
>      g_string_append(gdbserver_state.str_buf, 
> ";vContSupported+;multiprocess+");
> +
> +    if (extended_qsupported_features) {
> +        g_string_append(gdbserver_state.str_buf, 
> extended_qsupported_features);
> +    }
> +
>      gdb_put_strbuf();
>  }
>  
> @@ -1729,6 +1740,14 @@ static const GdbCmdParseEntry 
> gdb_gen_query_set_common_table[] = {
>      },
>  };
>  
> +static GdbCmdParseEntry *extended_query_table;
> +static int extended_query_table_size;
> +void gdb_extend_query_table(GdbCmdParseEntry *table, int size)
> +{

g_assert(!extended_query_table)

> +    extended_query_table = table;
> +    extended_query_table_size = size;
> +}
> +
>  static const GdbCmdParseEntry gdb_gen_query_table[] = {
>      {
>          .handler = handle_query_curr_tid,
> @@ -1821,6 +1840,14 @@ static const GdbCmdParseEntry gdb_gen_query_table[] = {
>  #endif
>  };
>  
> +static GdbCmdParseEntry *extended_set_table;
> +static int extended_set_table_size;
> +void gdb_extend_set_table(GdbCmdParseEntry *table, int size)
> +{
> +    extended_set_table = table;
> +    extended_set_table_size = size;
> +}
> +
>  static const GdbCmdParseEntry gdb_gen_set_table[] = {
>      /* Order is important if has same prefix */
>      {
> @@ -1859,11 +1886,21 @@ static void handle_gen_query(GArray *params, void 
> *user_ctx)
>          return;
>      }
>  
> -    if (!process_string_cmd(gdb_get_cmd_param(params, 0)->data,
> -                            gdb_gen_query_table,
> -                            ARRAY_SIZE(gdb_gen_query_table))) {
> -        gdb_put_packet("");
> +    if (process_string_cmd(gdb_get_cmd_param(params, 0)->data,
> +                           gdb_gen_query_table,
> +                           ARRAY_SIZE(gdb_gen_query_table))) {
> +        return;
> +    }
> +
> +    if (extended_query_table &&
> +        process_string_cmd(gdb_get_cmd_param(params, 0)->data,
> +                           extended_query_table,
> +                           extended_query_table_size)) {
> +        return;
>      }
> +
> +    /* Can't handle query, return Empty response. */
> +    gdb_put_packet("");
>  }
>  
>  static void handle_gen_set(GArray *params, void *user_ctx)
> @@ -1878,11 +1915,21 @@ static void handle_gen_set(GArray *params, void 
> *user_ctx)
>          return;
>      }
>  
> -    if (!process_string_cmd(gdb_get_cmd_param(params, 0)->data,
> +    if (process_string_cmd(gdb_get_cmd_param(params, 0)->data,
>                             gdb_gen_set_table,
>                             ARRAY_SIZE(gdb_gen_set_table))) {
> -        gdb_put_packet("");
> +        return;
>      }
> +
> +    if (extended_set_table &&
> +        process_string_cmd(gdb_get_cmd_param(params, 0)->data,
> +                           extended_set_table,
> +                           extended_set_table_size)) {
> +        return;
> +    }
> +
> +    /* Can't handle set, return Empty response. */
> +    gdb_put_packet("");
>  }
>  
>  static void handle_target_halt(GArray *params, void *user_ctx)
> diff --git a/include/gdbstub/commands.h b/include/gdbstub/commands.h
> index dd45c38472..2204c3ddbe 100644
> --- a/include/gdbstub/commands.h
> +++ b/include/gdbstub/commands.h
> @@ -71,4 +71,26 @@ typedef struct GdbCmdParseEntry {
>   */
>  int gdb_put_packet(const char *buf);
>  
> +/**
> + * gdb_extend_query_table() - Extend query table.
> + * @table: The table with the additional query packet handlers.
> + * @size: The number of handlers to be added.
> + */
> +void gdb_extend_query_table(GdbCmdParseEntry *table, int size);
> +
> +/**
> + * gdb_extend_set_table() - Extend set table.
> + * @table: The table with the additional set packet handlers.
> + * @size: The number of handlers to be added.
> + */
> +void gdb_extend_set_table(GdbCmdParseEntry *table, int size);
> +
> +/**
> + * gdb_extend_qsupported_features() - Extend the qSupported features string.
> + * @qsupported_features: The additional qSupported feature(s) string. The 
> string
> + * should start with a semicolon and, if there are more than one feature, the
> + * features should be separate by a semiocolon.
> + */
> +void gdb_extend_qsupported_features(char *qsupported_features);
> +

We should make it clear these functions should only be called once
(although I guess in a heterogeneous future we might have to do something
more clever).

>  #endif /* GDBSTUB_COMMANDS_H */

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro