Re: [PATCH 2/3] perf tools: Allow to enable/disable events via control file

Alexei Budankov
2020-12-07T17:03:31Z

Hi,

On 06.12.2020 20:05, Jiri Olsa wrote:
> Adding new control events to enable/disable specific event.
> The interface string for control file are:
>
> 'enable-<EVENT NAME>'
> 'disable-<EVENT NAME>'

<SNIP>

>
> when received the command, perf will scan the current evlist
> for <EVENT NAME> and if found it's enabled/disabled.

<SNIP>

> diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
> index 70aff26612a9..05723227bebf 100644
> --- a/tools/perf/util/evlist.c
> +++ b/tools/perf/util/evlist.c
> @@ -1915,7 +1915,13 @@ static int evlist__ctlfd_recv(struct evlist *evlist, enum evlist_ctl_cmd *cmd,
> bytes_read == data_size ? "" : c == '\n' ? "\\n" : "\\0");
>
> if (bytes_read > 0) {
> - if (!strncmp(cmd_data, EVLIST_CTL_CMD_ENABLE_TAG,
> + if (!strncmp(cmd_data, EVLIST_CTL_CMD_ENABLE_EVSEL_TAG,
> + (sizeof(EVLIST_CTL_CMD_ENABLE_EVSEL_TAG)-1))) {
> + *cmd = EVLIST_CTL_CMD_ENABLE_EVSEL;
> + } else if (!strncmp(cmd_data, EVLIST_CTL_CMD_DISABLE_EVSEL_TAG,
> + (sizeof(EVLIST_CTL_CMD_DISABLE_EVSEL_TAG)-1))) {
> + *cmd = EVLIST_CTL_CMD_DISABLE_EVSEL;
> + } else if (!strncmp(cmd_data, EVLIST_CTL_CMD_ENABLE_TAG,
> (sizeof(EVLIST_CTL_CMD_ENABLE_TAG)-1))) {
> *cmd = EVLIST_CTL_CMD_ENABLE;
> } else if (!strncmp(cmd_data, EVLIST_CTL_CMD_DISABLE_TAG,
> @@ -1952,6 +1958,8 @@ int evlist__ctlfd_process(struct evlist *evlist, enum evlist_ctl_cmd *cmd)
> char cmd_data[EVLIST_CTL_CMD_MAX_LEN];
> int ctlfd_pos = evlist->ctl_fd.pos;
> struct pollfd *entries = evlist->core.pollfd.entries;
> + struct evsel *evsel;
> + char *evsel_name;
>
> if (!evlist__ctlfd_initialized(evlist) || !entries[ctlfd_pos].revents)
> return 0;
> @@ -1967,6 +1975,26 @@ int evlist__ctlfd_process(struct evlist *evlist, enum evlist_ctl_cmd *cmd)
> case EVLIST_CTL_CMD_DISABLE:
> evlist__disable(evlist);
> break;
> + case EVLIST_CTL_CMD_ENABLE_EVSEL:
> + evsel_name = cmd_data + sizeof(EVLIST_CTL_CMD_ENABLE_EVSEL_TAG) - 1;

It makes sense to check that evsel_name still points
into cmd_data buffer after assigning to event name.

Regards,
Alexei