linux-kernel - Re: [RFC 02/12] perf event action: Add parsing const expr support

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Message-ID: <Z0jROJ7JPTjmeZly@x1>
Date: Thu, 28 Nov 2024 17:23:20 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Yang Jihong <yangjihong@...edance.com>
Cc: peterz@...radead.org, mingo@...hat.com, namhyung@...nel.org,
	mark.rutland@....com, alexander.shishkin@...ux.intel.com,
	jolsa@...nel.org, irogers@...gle.com, adrian.hunter@...el.com,
	kan.liang@...ux.intel.com, james.clark@....com,
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC 02/12] perf event action: Add parsing const expr support

On Thu, Nov 28, 2024 at 09:35:43PM +0800, Yang Jihong wrote:
> Event action requires constant expression parsing support,
> which include constant integer and constant string.
> 
> Signed-off-by: Yang Jihong <yangjihong@...edance.com>
> ---
>  tools/perf/util/parse-action.c | 27 +++++++++++++++++++++++++++
>  tools/perf/util/parse-action.h |  5 +++++
>  2 files changed, 32 insertions(+)
> 
> diff --git a/tools/perf/util/parse-action.c b/tools/perf/util/parse-action.c
> index 01c8c7fdea59..391546bf3d73 100644
> --- a/tools/perf/util/parse-action.c
> +++ b/tools/perf/util/parse-action.c
> @@ -4,6 +4,9 @@
>   * Actions are the programs that run when the sampling event is triggered.
>   * The action is a list of expressions separated by semicolons (;).
>   * Each action is an expression, added to actions_head node as list_head node.
> + *
> + * Supported expressions:
> + *   - constant:

This seems incomplete, what should come after the :?

the patch description, at the beginning of this message has more details
than here.

>   */
>  
>  #include "util/debug.h"
> @@ -115,7 +118,31 @@ void event_actions__free(void)
>  	(void)event_actions__for_each_expr_safe(do_action_free, NULL, false);
>  }
>  
> +static struct evtact_expr_ops *expr_const_ops_list[EVTACT_EXPR_CONST_TYPE_MAX] = {
> +};
> +
> +static int expr_const_set_ops(struct evtact_expr *expr, u32 opcode)
> +{
> +	if (opcode >= EVTACT_EXPR_CONST_TYPE_MAX) {
> +		pr_err("expr_const opcode invalid: %u\n", opcode);
> +		return -EINVAL;
> +	}
> +
> +	if (expr_const_ops_list[opcode] == NULL) {
> +		pr_err("expr_const opcode not supported: %u\n", opcode);
> +		return -ENOTSUP;
> +	}

Since expr_const_ops_list[EVTACT_EXPR_TYPE_CONST] is NULL, this will
always fail?

> +
> +	expr->ops = expr_const_ops_list[opcode];
> +	return 0;
> +}
> +
> +static struct evtact_expr_class expr_const = {
> +	.set_ops = expr_const_set_ops,
> +};
> +
>  static struct evtact_expr_class *expr_class_list[EVTACT_EXPR_TYPE_MAX] = {
> +	[EVTACT_EXPR_TYPE_CONST]   = &expr_const,
>  };
>  
>  int parse_action_expr__set_class(enum evtact_expr_type type,
> diff --git a/tools/perf/util/parse-action.h b/tools/perf/util/parse-action.h
> index 71a0a166959e..47bd75264dee 100644
> --- a/tools/perf/util/parse-action.h
> +++ b/tools/perf/util/parse-action.h
> @@ -9,9 +9,14 @@
>  #include "evlist.h"
>  
>  enum evtact_expr_type {
> +	EVTACT_EXPR_TYPE_CONST,
>  	EVTACT_EXPR_TYPE_MAX,
>  };
>  
> +enum evtact_expr_const_type {
> +	EVTACT_EXPR_CONST_TYPE_MAX,
> +};
> +
>  struct evtact_expr;
>  struct evtact_expr_ops {
>  	int (*new)(struct evtact_expr *expr, void *data, int size);
> -- 
> 2.25.1