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

Arnaldo Carvalho de Melo
2024-11-28T20:23:24Z

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@bytedance.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