Re: [PATCH v10 05/15] perf evlist: implement control command handling functions

Namhyung Kim
2020-07-13T03:21:14Z

On Wed, Jul 8, 2020 at 4:50 PM Alexey Budankov
<alexey.budankov@linux.intel.com> wrote:
>
>
> Implement functions of initialization, finalization and processing
> of control command messages coming from control file descriptors.
> Allocate control file descriptor as descriptor at struct pollfd
> object of evsel_list for atomic poll() operation.
>
> Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
> ---
[SNIP]
> +static int evlist__ctlfd_recv(struct evlist *evlist, enum evlist_ctl_cmd *cmd,
> + char *cmd_data, size_t data_size)
> +{
> + int err;
> + char c;
> + size_t bytes_read = 0;
> +
> + memset(cmd_data, 0, data_size--);

I overlooked the '--' at the end and thought there might be
buffer overflow.. Care to add a comment?

> +
> + do {
> + err = read(evlist->ctl_fd.fd, &c, 1);

Maybe I missed earlier discussion, but do we really want
this 1 byte read in a loop?

Thanks
Namhyung

> + if (err > 0) {
> + if (c == '\n' || c == '\0')
> + break;
> + cmd_data[bytes_read++] = c;
> + if (bytes_read == data_size)
> + break;
> + } else {
> + if (err == -1)
> + pr_err("Failed to read from ctlfd %d: %m\n", evlist->ctl_fd.fd);
> + break;
> + }
> + } while (1);
> +
> + pr_debug("Message from ctl_fd: \"%s%s\"\n", cmd_data,
> + bytes_read == data_size ? "" : c == '\n' ? "\\n" : "\\0");
> +
> + if (err > 0) {
> + 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,
> + (sizeof(EVLIST_CTL_CMD_DISABLE_TAG)-1))) {
> + *cmd = EVLIST_CTL_CMD_DISABLE;
> + }
> + }
> +
> + return err;
> +}