aboutsummaryrefslogtreecommitdiff
path: root/kernel/trace
diff options
context:
space:
mode:
authorSteven Rostedt <srostedt@redhat.com>2009-04-15 13:24:06 -0400
committerIngo Molnar <mingo@elte.hu>2009-04-17 16:59:15 +0200
commit93eb677d74a4f7d3edfb678c94f6c0544d9fbad2 (patch)
tree8bbc46895be623a78316230362e94969dbb02135 /kernel/trace
parentf3948f8857ef5de239f28a61dddb1554a0ae4c2c (diff)
ftrace: use module notifier for function tracer
The hooks in the module code for the function tracer must be called before any of that module code runs. The function tracer hooks modify the module (replacing calls to mcount to nops). If the code is executed while the change occurs, then the CPU can take a GPF. To handle the above with a bit of paranoia, I originally implemented the hooks as calls directly from the module code. After examining the notifier calls, it looks as though the start up notify is called before any of the module's code is executed. This makes the use of the notify safe with ftrace. Only the startup notify is required to be "safe". The shutdown simply removes the entries from the ftrace function list, and does not modify any code. This change has another benefit. It removes a issue with a reverse dependency in the mutexes of ftrace_lock and module_mutex. [ Impact: fix lock dependency bug, cleanup ] Cc: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'kernel/trace')
-rw-r--r--kernel/trace/ftrace.c90
1 files changed, 64 insertions, 26 deletions
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index a2348898858..5b606f45b6c 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -916,30 +916,6 @@ static void ftrace_free_rec(struct dyn_ftrace *rec)
rec->flags |= FTRACE_FL_FREE;
}
-void ftrace_release(void *start, unsigned long size)
-{
- struct dyn_ftrace *rec;
- struct ftrace_page *pg;
- unsigned long s = (unsigned long)start;
- unsigned long e = s + size;
-
- if (ftrace_disabled || !start)
- return;
-
- mutex_lock(&ftrace_lock);
- do_for_each_ftrace_rec(pg, rec) {
- if ((rec->ip >= s) && (rec->ip < e)) {
- /*
- * rec->ip is changed in ftrace_free_rec()
- * It should not between s and e if record was freed.
- */
- FTRACE_WARN_ON(rec->flags & FTRACE_FL_FREE);
- ftrace_free_rec(rec);
- }
- } while_for_each_ftrace_rec();
- mutex_unlock(&ftrace_lock);
-}
-
static struct dyn_ftrace *ftrace_alloc_dyn_node(unsigned long ip)
{
struct dyn_ftrace *rec;
@@ -2752,14 +2728,72 @@ static int ftrace_convert_nops(struct module *mod,
return 0;
}
-void ftrace_init_module(struct module *mod,
- unsigned long *start, unsigned long *end)
+#ifdef CONFIG_MODULES
+void ftrace_release(void *start, void *end)
+{
+ struct dyn_ftrace *rec;
+ struct ftrace_page *pg;
+ unsigned long s = (unsigned long)start;
+ unsigned long e = (unsigned long)end;
+
+ if (ftrace_disabled || !start || start == end)
+ return;
+
+ mutex_lock(&ftrace_lock);
+ do_for_each_ftrace_rec(pg, rec) {
+ if ((rec->ip >= s) && (rec->ip < e)) {
+ /*
+ * rec->ip is changed in ftrace_free_rec()
+ * It should not between s and e if record was freed.
+ */
+ FTRACE_WARN_ON(rec->flags & FTRACE_FL_FREE);
+ ftrace_free_rec(rec);
+ }
+ } while_for_each_ftrace_rec();
+ mutex_unlock(&ftrace_lock);
+}
+
+static void ftrace_init_module(struct module *mod,
+ unsigned long *start, unsigned long *end)
{
if (ftrace_disabled || start == end)
return;
ftrace_convert_nops(mod, start, end);
}
+static int ftrace_module_notify(struct notifier_block *self,
+ unsigned long val, void *data)
+{
+ struct module *mod = data;
+
+ switch (val) {
+ case MODULE_STATE_COMING:
+ ftrace_init_module(mod, mod->ftrace_callsites,
+ mod->ftrace_callsites +
+ mod->num_ftrace_callsites);
+ break;
+ case MODULE_STATE_GOING:
+ ftrace_release(mod->ftrace_callsites,
+ mod->ftrace_callsites +
+ mod->num_ftrace_callsites);
+ break;
+ }
+
+ return 0;
+}
+#else
+static int ftrace_module_notify(struct notifier_block *self,
+ unsigned long val, void *data)
+{
+ return 0;
+}
+#endif /* CONFIG_MODULES */
+
+struct notifier_block ftrace_module_nb = {
+ .notifier_call = ftrace_module_notify,
+ .priority = 0,
+};
+
extern unsigned long __start_mcount_loc[];
extern unsigned long __stop_mcount_loc[];
@@ -2791,6 +2825,10 @@ void __init ftrace_init(void)
__start_mcount_loc,
__stop_mcount_loc);
+ ret = register_module_notifier(&ftrace_module_nb);
+ if (!ret)
+ pr_warning("Failed to register trace ftrace module notifier\n");
+
return;
failed:
ftrace_disabled = 1;