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SubjectRe: [PATCH v2 34/40] tracing: Add 'last error' error facility for hist triggers
On Tue,  5 Sep 2017 16:57:46 -0500
Tom Zanussi <tom.zanussi@linux.intel.com> wrote:

> +static char *hist_err_str;
> +static char *last_hist_cmd;
> +
> +static int hist_err_alloc(void)
> +{
> + int ret = 0;
> +
> + last_hist_cmd = kzalloc(MAX_FILTER_STR_VAL, GFP_KERNEL);
> + if (!last_hist_cmd)
> + return -ENOMEM;
> +
> + hist_err_str = kzalloc(MAX_FILTER_STR_VAL, GFP_KERNEL);
> + if (!hist_err_str) {
> + kfree(last_hist_cmd);
> + ret = -ENOMEM;
> + }

This gets allocated during boot up. Why have it be allocated in the
first place? Just have it be strings:

static char hist_err_str[MAX_FILTER_STR_VAL];
static char last_hist_cmd[MAX_FILTER_STR_VAL];

You are not saving any space by doing it this way. In fact, you waste
it because now you need to add the pointers to the strings.

> +
> + return ret;
> +}
> +
> +static void last_cmd_set(char *str)
> +{
> + if (!last_hist_cmd || !str)
> + return;
> +
> + if (strlen(str) > MAX_FILTER_STR_VAL - 1)
> + return;

Instead of returning nothing, why not just truncate it?

> +
> + strcpy(last_hist_cmd, str);

strncpy(last_hist_cmd, str, MAX_FILTER_STR_VAL - 1);
last_hist_cmd[MAX_FILTER_STR_VAL - 1] = 0;

> +}
> +
> +static void hist_err(char *str, char *var)
> +{
> + int maxlen = MAX_FILTER_STR_VAL - 1;
> +
> + if (!hist_err_str || !str)
> + return;
> +
> + if (strlen(hist_err_str))
> + return;
> +
> + if (!var)
> + var = "";
> +
> + if (strlen(hist_err_str) + strlen(str) + strlen(var) > maxlen)
> + return;
> +
> + strcat(hist_err_str, str);
> + strcat(hist_err_str, var);
> +}
> +
> +static void hist_err_event(char *str, char *system, char *event, char *var)
> +{
> + char err[MAX_FILTER_STR_VAL];
> +
> + if (system && var)
> + sprintf(err, "%s.%s.%s", system, event, var);
> + else if (system)
> + sprintf(err, "%s.%s", system, event);
> + else
> + strcpy(err, var);

Use snprintf() and strncpy() for the above.

-- Steve

> +
> + hist_err(str, err);
> +}
> +
> +static void hist_err_clear(void)
> +{
> + if (!hist_err_str)
> + return;
> +
> + hist_err_str[0] = '\0';
> +}
> +
> +static bool have_hist_err(void)
> +{
> + if (hist_err_str && strlen(hist_err_str))
> + return true;
> +
> + return false;
> +}
> +

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