tracing/function-graph-tracer: make set_graph_function file support ftrace regex

Impact: trace only functions matching a pattern

The set_graph_function file let one to trace only one or several
chosen functions and follow all their code flow.

Currently, only a constant function name is allowed so this patch
allows the ftrace_regex functions:

- matches all functions that end with "name":
  echo *name > set_graph_function

- matches all functions that begin with "name":
  echo name* > set_graph_function

- matches all functions that contains "name":
  echo *name* > set_graph_function

Example:

echo mutex* > set_graph_function

 0)               |  mutex_lock_nested() {
 0)   0.563 us    |    __might_sleep();
 0)   2.072 us    |  }
 0)               |  mutex_unlock() {
 0)   1.036 us    |    __mutex_unlock_slowpath();
 0)   2.433 us    |  }
 0)               |  mutex_unlock() {
 0)   0.691 us    |    __mutex_unlock_slowpath();
 0)   1.787 us    |  }
 0)               |  mutex_lock_interruptible_nested() {
 0)   0.548 us    |    __might_sleep();
 0)   1.945 us    |  }

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 7dd5a2bef9cd1120fcc980cc00adcd80b601c9d0..cf59f4c547452cd46b230abc756140257e0ce26a 100644 (file)
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1895,6 +1895,10 @@ static void *g_start(struct seq_file *m, loff_t *pos)
 
        mutex_lock(&graph_lock);
 
+       /* Nothing, tell g_show to print all functions are enabled */
+       if (!ftrace_graph_count && !*pos)
+               return (void *)1;
+
        p = g_next(m, p, pos);
 
        return p;
@@ -1913,6 +1917,11 @@ static int g_show(struct seq_file *m, void *v)
        if (!ptr)
                return 0;
 
+       if (ptr == (unsigned long *)1) {
+               seq_printf(m, "#### all functions enabled ####\n");
+               return 0;
+       }
+
        kallsyms_lookup(*ptr, NULL, NULL, NULL, str);
 
        seq_printf(m, "%s\n", str);
@@ -1966,38 +1975,51 @@ ftrace_graph_read(struct file *file, char __user *ubuf,
 }
 
 static int
-ftrace_set_func(unsigned long *array, int idx, char *buffer)
+ftrace_set_func(unsigned long *array, int *idx, char *buffer)
 {
-       char str[KSYM_SYMBOL_LEN];
        struct dyn_ftrace *rec;
        struct ftrace_page *pg;
+       int search_len;
        int found = 0;
-       int j;
+       int type, not;
+       char *search;
+       bool exists;
+       int i;
 
        if (ftrace_disabled)
                return -ENODEV;
 
+       /* decode regex */
+       type = ftrace_setup_glob(buffer, strlen(buffer), &search, &not);
+       if (not)
+               return -EINVAL;
+
+       search_len = strlen(search);
+
        mutex_lock(&ftrace_lock);
        do_for_each_ftrace_rec(pg, rec) {
 
+               if (*idx >= FTRACE_GRAPH_MAX_FUNCS)
+                       break;
+
                if (rec->flags & (FTRACE_FL_FAILED | FTRACE_FL_FREE))
                        continue;
 
-               kallsyms_lookup(rec->ip, NULL, NULL, NULL, str);
-               if (strcmp(str, buffer) == 0) {
-                       /* Return 1 if we add it to the array */
-                       found = 1;
-                       for (j = 0; j < idx; j++)
-                               if (array[j] == rec->ip) {
-                                       found = 0;
+               if (ftrace_match_record(rec, search, search_len, type)) {
+                       /* ensure it is not already in the array */
+                       exists = false;
+                       for (i = 0; i < *idx; i++)
+                               if (array[i] == rec->ip) {
+                                       exists = true;
                                        break;
                                }
-                       if (found)
-                               array[idx] = rec->ip;
-                       goto out;
+                       if (!exists) {
+                               array[(*idx)++] = rec->ip;
+                               found = 1;
+                       }
                }
        } while_for_each_ftrace_rec();
- out:
+
        mutex_unlock(&ftrace_lock);
 
        return found ? 0 : -EINVAL;
@@ -2066,13 +2088,11 @@ ftrace_graph_write(struct file *file, const char __user *ubuf,
        }
        buffer[index] = 0;
 
-       /* we allow only one at a time */
-       ret = ftrace_set_func(array, ftrace_graph_count, buffer);
+       /* we allow only one expression at a time */
+       ret = ftrace_set_func(array, &ftrace_graph_count, buffer);
        if (ret)
                goto out;
 
-       ftrace_graph_count++;
-
        file->f_pos += read;
 
        ret = read;