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>

1 files changed, 38 insertions, 18 deletions

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 7dd5a2bef9cd..cf59f4c54745 100644
--- 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;