tracing: Remove size restriction on hist trigger cmd error logging

Currently, hist trigger command error strings are restricted to a
length of MAX_FILTER_STR_VAL (256), which is too short for some
commands already seen in the wild (with cmd strings longer than that
showing up truncated in err_log).

Remove the restriction so that no hist trigger command error string is
ever truncated.

Link: https://lkml.kernel.org/r/0f9d46407222eaf6632cd3b417bc50a11f401b71.1643399022.git.zanussi@kernel.org
Signed-off-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index ada87bfb5bb85da4430ff6cb6d3ed295a8a1a084..5e8970624bce727e263f9df79efb9cb8b6013080 100644 (file)
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -727,11 +727,16 @@ static struct track_data *track_data_alloc(unsigned int key_len,
        return data;
 }
 
-static char last_cmd[MAX_FILTER_STR_VAL];
+#define HIST_PREFIX "hist:"
+
+static char *last_cmd;
 static char last_cmd_loc[MAX_FILTER_STR_VAL];
 
 static int errpos(char *str)
 {
+       if (!str || !last_cmd)
+               return 0;
+
        return err_pos(last_cmd, str);
 }
 
@@ -739,12 +744,19 @@ static void last_cmd_set(struct trace_event_file *file, char *str)
 {
        const char *system = NULL, *name = NULL;
        struct trace_event_call *call;
+       int len = 0;
 
        if (!str)
                return;
 
-       strcpy(last_cmd, "hist:");
-       strncat(last_cmd, str, MAX_FILTER_STR_VAL - 1 - sizeof("hist:"));
+       len += sizeof(HIST_PREFIX) + strlen(str) + 1;
+       kfree(last_cmd);
+       last_cmd = kzalloc(len, GFP_KERNEL);
+       if (!last_cmd)
+               return;
+
+       strcpy(last_cmd, HIST_PREFIX);
+       strncat(last_cmd, str, len - sizeof(HIST_PREFIX));
 
        if (file) {
                call = file->event_call;
@@ -757,18 +769,22 @@ static void last_cmd_set(struct trace_event_file *file, char *str)
        }
 
        if (system)
-               snprintf(last_cmd_loc, MAX_FILTER_STR_VAL, "hist:%s:%s", system, name);
+               snprintf(last_cmd_loc, MAX_FILTER_STR_VAL, HIST_PREFIX "%s:%s", system, name);
 }
 
-static void hist_err(struct trace_array *tr, u8 err_type, u8 err_pos)
+static void hist_err(struct trace_array *tr, u8 err_type, u16 err_pos)
 {
+       if (!last_cmd)
+               return;
+
        tracing_log_err(tr, last_cmd_loc, last_cmd, err_text,
                        err_type, err_pos);
 }
 
 static void hist_err_clear(void)
 {
-       last_cmd[0] = '\0';
+       if (last_cmd)
+               last_cmd[0] = '\0';
        last_cmd_loc[0] = '\0';
 }
 
@@ -5610,7 +5626,7 @@ static int event_hist_trigger_print(struct seq_file *m,
        bool have_var = false;
        unsigned int i;
 
-       seq_puts(m, "hist:");
+       seq_puts(m, HIST_PREFIX);
 
        if (data->name)
                seq_printf(m, "%s:", data->name);