ftrace: Replace FTRACE_FL_NOTRACE flag with a hash of ignored functions

To prepare for the accounting system that will allow multiple users of
the function tracer, having the FTRACE_FL_NOTRACE as a flag in the
dyn_trace record does not make sense.

All ftrace_ops will soon have a hash of functions they should trace
and not trace. By making a global hash of functions not to trace makes
this easier for the transition.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

2 files changed, 150 insertions, 27 deletions

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 32047449b309..fe0a90a09243 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -149,7 +149,6 @@ enum {
         FTRACE_FL_FREE          = (1 << 0),
         FTRACE_FL_FILTER        = (1 << 1),
         FTRACE_FL_ENABLED       = (1 << 2),
-        FTRACE_FL_NOTRACE       = (1 << 3),
 };
 
 struct dyn_ftrace {
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index d3406346ced6..04c002a491fb 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -57,6 +57,7 @@
 /* hash bits for specific function selection */
 #define FTRACE_HASH_BITS 7
 #define FTRACE_FUNC_HASHSIZE (1 << FTRACE_HASH_BITS)
+#define FTRACE_HASH_MAX_BITS 10
 
 /* ftrace_enabled is a method to turn ftrace on or off */
 int ftrace_enabled __read_mostly;
@@ -865,6 +866,22 @@ enum {
         FTRACE_START_FUNC_RET           = (1 << 3),
         FTRACE_STOP_FUNC_RET            = (1 << 4),
 };
+struct ftrace_func_entry {
+        struct hlist_node hlist;
+        unsigned long ip;
+};
+
+struct ftrace_hash {
+        unsigned long           size_bits;
+        struct hlist_head       *buckets;
+        unsigned long           count;
+};
+
+static struct hlist_head notrace_buckets[1 << FTRACE_HASH_MAX_BITS];
+static struct ftrace_hash notrace_hash = {
+        .size_bits = FTRACE_HASH_MAX_BITS,
+        .buckets = notrace_buckets,
+};
 
 static int ftrace_filtered;
 
@@ -889,6 +906,79 @@ static struct ftrace_page	*ftrace_pages;
 
 static struct dyn_ftrace *ftrace_free_records;
 
+static struct ftrace_func_entry *
+ftrace_lookup_ip(struct ftrace_hash *hash, unsigned long ip)
+{
+        unsigned long key;
+        struct ftrace_func_entry *entry;
+        struct hlist_head *hhd;
+        struct hlist_node *n;
+
+        if (!hash->count)
+                return NULL;
+
+        if (hash->size_bits > 0)
+                key = hash_long(ip, hash->size_bits);
+        else
+                key = 0;
+
+        hhd = &hash->buckets[key];
+
+        hlist_for_each_entry_rcu(entry, n, hhd, hlist) {
+                if (entry->ip == ip)
+                        return entry;
+        }
+        return NULL;
+}
+
+static int add_hash_entry(struct ftrace_hash *hash, unsigned long ip)
+{
+        struct ftrace_func_entry *entry;
+        struct hlist_head *hhd;
+        unsigned long key;
+
+        entry = kmalloc(sizeof(*entry), GFP_KERNEL);
+        if (!entry)
+                return -ENOMEM;
+
+        if (hash->size_bits)
+                key = hash_long(ip, hash->size_bits);
+        else
+                key = 0;
+
+        entry->ip = ip;
+        hhd = &hash->buckets[key];
+        hlist_add_head(&entry->hlist, hhd);
+        hash->count++;
+
+        return 0;
+}
+
+static void
+remove_hash_entry(struct ftrace_hash *hash,
+                  struct ftrace_func_entry *entry)
+{
+        hlist_del(&entry->hlist);
+        kfree(entry);
+        hash->count--;
+}
+
+static void ftrace_hash_clear(struct ftrace_hash *hash)
+{
+        struct hlist_head *hhd;
+        struct hlist_node *tp, *tn;
+        struct ftrace_func_entry *entry;
+        int size = 1 << hash->size_bits;
+        int i;
+
+        for (i = 0; i < size; i++) {
+                hhd = &hash->buckets[i];
+                hlist_for_each_entry_safe(entry, tp, tn, hhd, hlist)
+                        remove_hash_entry(hash, entry);
+        }
+        FTRACE_WARN_ON(hash->count);
+}
+
 /*
  * This is a double for. Do not use 'break' to break out of the loop,
  * you must use a goto.
@@ -1032,7 +1122,7 @@ __ftrace_replace_code(struct dyn_ftrace *rec, int enable)
          * If we want to enable it and filtering is on, enable it only if
          * it's filtered
          */
-        if (enable && !(rec->flags & FTRACE_FL_NOTRACE)) {
+        if (enable && !ftrace_lookup_ip(&notrace_hash, rec->ip)) {
                 if (!ftrace_filtered || (rec->flags & FTRACE_FL_FILTER))
                         flag = FTRACE_FL_ENABLED;
         }
@@ -1465,7 +1555,7 @@ t_next(struct seq_file *m, void *v, loff_t *pos)
                      !(rec->flags & FTRACE_FL_FILTER)) ||
 
                     ((iter->flags & FTRACE_ITER_NOTRACE) &&
-                     !(rec->flags & FTRACE_FL_NOTRACE))) {
+                     !ftrace_lookup_ip(&notrace_hash, rec->ip))) {
                         rec = NULL;
                         goto retry;
                 }
@@ -1609,14 +1699,15 @@ static void ftrace_filter_reset(int enable)
 {
         struct ftrace_page *pg;
         struct dyn_ftrace *rec;
-        unsigned long type = enable ? FTRACE_FL_FILTER : FTRACE_FL_NOTRACE;
 
         mutex_lock(&ftrace_lock);
-        if (enable)
+        if (enable) {
                 ftrace_filtered = 0;
-        do_for_each_ftrace_rec(pg, rec) {
-                rec->flags &= ~type;
-        } while_for_each_ftrace_rec();
+                do_for_each_ftrace_rec(pg, rec) {
+                        rec->flags &= ~FTRACE_FL_FILTER;
+                } while_for_each_ftrace_rec();
+        } else
+                ftrace_hash_clear(&notrace_hash);
         mutex_unlock(&ftrace_lock);
 }
 
@@ -1716,13 +1807,36 @@ static int ftrace_match(char *str, char *regex, int len, int type)
         return matched;
 }
 
-static void
-update_record(struct dyn_ftrace *rec, unsigned long flag, int not)
+static int
+update_record(struct dyn_ftrace *rec, int enable, int not)
 {
-        if (not)
-                rec->flags &= ~flag;
-        else
-                rec->flags |= flag;
+        struct ftrace_func_entry *entry;
+        struct ftrace_hash *hash = &notrace_hash;
+        int ret = 0;
+
+        if (enable) {
+                if (not)
+                        rec->flags &= ~FTRACE_FL_FILTER;
+                else
+                        rec->flags |= FTRACE_FL_FILTER;
+        } else {
+                if (not) {
+                        /* Do nothing if it doesn't exist */
+                        entry = ftrace_lookup_ip(hash, rec->ip);
+                        if (!entry)
+                                return 0;
+
+                        remove_hash_entry(hash, entry);
+                } else {
+                        /* Do nothing if it exists */
+                        entry = ftrace_lookup_ip(hash, rec->ip);
+                        if (entry)
+                                return 0;
+
+                        ret = add_hash_entry(hash, rec->ip);
+                }
+        }
+        return ret;
 }
 
 static int
@@ -1754,16 +1868,14 @@ static int match_records(char *buff, int len, char *mod, int enable, int not)
         struct dyn_ftrace *rec;
         int type = MATCH_FULL;
         char *search = buff;
-        unsigned long flag;
         int found = 0;
+        int ret;
 
         if (len) {
                 type = filter_parse_regex(buff, len, &search, &not);
                 search_len = strlen(search);
         }
 
-        flag = enable ? FTRACE_FL_FILTER : FTRACE_FL_NOTRACE;
-
         mutex_lock(&ftrace_lock);
 
         if (unlikely(ftrace_disabled))
@@ -1772,7 +1884,11 @@ static int match_records(char *buff, int len, char *mod, int enable, int not)
         do_for_each_ftrace_rec(pg, rec) {
 
                 if (ftrace_match_record(rec, mod, search, search_len, type)) {
-                        update_record(rec, flag, not);
+                        ret = update_record(rec, enable, not);
+                        if (ret < 0) {
+                                found = ret;
+                                goto out_unlock;
+                        }
                         found = 1;
                 }
                 /*
@@ -1821,6 +1937,7 @@ static int
 ftrace_mod_callback(char *func, char *cmd, char *param, int enable)
 {
         char *mod;
+        int ret = -EINVAL;
 
         /*
          * cmd == 'mod' because we only registered this func
@@ -1832,15 +1949,19 @@ ftrace_mod_callback(char *func, char *cmd, char *param, int enable)
 
         /* we must have a module name */
         if (!param)
-                return -EINVAL;
+                return ret;
 
         mod = strsep(&param, ":");
         if (!strlen(mod))
-                return -EINVAL;
+                return ret;
 
-        if (ftrace_match_module_records(func, mod, enable))
-                return 0;
-        return -EINVAL;
+        ret = ftrace_match_module_records(func, mod, enable);
+        if (!ret)
+                ret = -EINVAL;
+        if (ret < 0)
+                return ret;
+
+        return 0;
 }
 
 static struct ftrace_func_command ftrace_mod_cmd = {
@@ -2132,14 +2253,17 @@ static int ftrace_process_regex(char *buff, int len, int enable)
 {
         char *func, *command, *next = buff;
         struct ftrace_func_command *p;
-        int ret = -EINVAL;
+        int ret;
 
         func = strsep(&next, ":");
 
         if (!next) {
-                if (ftrace_match_records(func, len, enable))
-                        return 0;
-                return ret;
+                ret = ftrace_match_records(func, len, enable);
+                if (!ret)
+                        ret = -EINVAL;
+                if (ret < 0)
+                        return ret;
+                return 0;
         }
 
         /* command found */