Re: [RFC PATCH v5 2/3] tools lib traceevent: Add function to get dynamic arrays length

["Wangnan (F)" <wangnan0@huawei.com>]

On 2015/7/14 9:59, He Kuang wrote:
> To print a trace event with a dynamic array, __print_array(array, len,
> element_size) requires the number of items in the array, which can be
> got by the helper function __get_dynamic_array_len(), currently it is
> not an available function in the function list in process_function().
>
> Add new arg type PRINT_DYNAMIC_ARRAY_LEN which returns the array
> length embedded in the __data_loc_##item field to eval_num_arg().
>
> Signed-off-by: He Kuang <hekuang@huawei.com>
> ---
>   tools/lib/traceevent/event-parse.c                 | 52 ++++++++++++++++++++++
>   tools/lib/traceevent/event-parse.h                 |  1 +
>   .../util/scripting-engines/trace-event-python.c    |  1 +
>   3 files changed, 54 insertions(+)
>
> diff --git a/tools/lib/traceevent/event-parse.c b/tools/lib/traceevent/event-parse.c
> index cc25f05..55fc3b6c 100644
> --- a/tools/lib/traceevent/event-parse.c
> +++ b/tools/lib/traceevent/event-parse.c
> @@ -783,6 +783,7 @@ static void free_arg(struct print_arg *arg)
>   		free(arg->bitmask.bitmask);
>   		break;
>   	case PRINT_DYNAMIC_ARRAY:
> +	case PRINT_DYNAMIC_ARRAY_LEN:
>   		free(arg->dynarray.index);
>   		break;
>   	case PRINT_OP:
> @@ -2655,6 +2656,42 @@ process_dynamic_array(struct event_format *event, struct print_arg *arg, char **
>   }
>   
>   static enum event_type
> +process_dynamic_array_len(struct event_format *event, struct print_arg *arg,
> +			  char **tok)
> +{
> +	struct format_field *field;
> +	enum event_type type;
> +	char *token;
> +
> +	if (read_expect_type(EVENT_ITEM, &token) < 0)
> +		goto out_free;
> +
> +	arg->type = PRINT_DYNAMIC_ARRAY_LEN;
> +
> +	/* Find the field */
> +	field = pevent_find_field(event, token);
> +	if (!field)
> +		goto out_free;
> +
> +	arg->dynarray.field = field;
> +	arg->dynarray.index = 0;
> +
> +	if (read_expected(EVENT_DELIM, ")") < 0)
> +		goto out_err;
> +
> +	type = read_token(&token);
> +	*tok = token;
> +
> +	return type;
> +
> + out_free:
> +	free_token(token);
> + out_err:
> +	*tok = NULL;
> +	return EVENT_ERROR;
> +}
> +
> +static enum event_type
>   process_paren(struct event_format *event, struct print_arg *arg, char **tok)
>   {
>   	struct print_arg *item_arg;
> @@ -2901,6 +2938,10 @@ process_function(struct event_format *event, struct print_arg *arg,
>   		free_token(token);
>   		return process_dynamic_array(event, arg, tok);
>   	}
> +	if (strcmp(token, "__get_dynamic_array_len") == 0) {
> +		free_token(token);
> +		return process_dynamic_array_len(event, arg, tok);
> +	}
>   
>   	func = find_func_handler(event->pevent, token);
>   	if (func) {
> @@ -3581,6 +3622,17 @@ eval_num_arg(void *data, int size, struct event_format *event, struct print_arg
>   			goto out_warning_op;
>   		}
>   		break;
> +	case PRINT_DYNAMIC_ARRAY_LEN:
> +		offset = pevent_read_number(pevent,
> +					    data + arg->dynarray.field->offset,
> +					    arg->dynarray.field->size);
> +		/*
> +		 * The actual length of the dynamic array is stored
> +		 * in the top half of the field, and the offset
> +		 * is in the bottom half of the 32 bit field.
> +		 */
> +		val = (unsigned long long)(offset >> 16);
> +		break;
>   	case PRINT_DYNAMIC_ARRAY:
>   		/* Without [], we pass the address to the dynamic data */
>   		offset = pevent_read_number(pevent,
> diff --git a/tools/lib/traceevent/event-parse.h b/tools/lib/traceevent/event-parse.h
> index 063b197..94543aa 100644
> --- a/tools/lib/traceevent/event-parse.h
> +++ b/tools/lib/traceevent/event-parse.h
> @@ -294,6 +294,7 @@ enum print_arg_type {
>   	PRINT_OP,
>   	PRINT_FUNC,
>   	PRINT_BITMASK,
> +	PRINT_DYNAMIC_ARRAY_LEN,
>   };
>   
>   struct print_arg {
> diff --git a/tools/perf/util/scripting-engines/trace-event-python.c b/tools/perf/util/scripting-engines/trace-event-python.c
> index ace2484..d309341 100644
> --- a/tools/perf/util/scripting-engines/trace-event-python.c
> +++ b/tools/perf/util/scripting-engines/trace-event-python.c
> @@ -253,6 +253,7 @@ static void define_event_symbols(struct event_format *event,
>   	case PRINT_DYNAMIC_ARRAY:
>   	case PRINT_FUNC:
>   	case PRINT_BITMASK:
> +	case PRINT_DYNAMIC_ARRAY_LEN:

Here is a small problem in this patch that, it only updates 
trace-event-python.c, leaves
trace-event-perf.c unchanged. If CONFIG_LIBPERL is on, a compiling error 
will raise.

I fixed this in my own git repository.

Steven, could you please cherry-pick this one instead?

https://github.com/WangNan0/linux/commit/951d78339e8c7819e9a1a9faeaf15e2c0b1aaa10

Note that the author field of it is still He Kuang.

Thank you.

>   		/* we should warn... */
>   		return;
>   	}