ftrace/module: remove ftrace module notifier

Remove the ftrace module notifier in favor of directly calling
ftrace_module_enable() and ftrace_release_mod() in the module loader.
Hard-coding the function calls directly in the module loader removes
dependence on the module notifier call chain and provides better
visibility and control over what gets called when, which is important
to kernel utilities such as livepatch.

This fixes a notifier ordering issue in which the ftrace module notifier
(and hence ftrace_module_enable()) for coming modules was being called
after klp_module_notify(), which caused livepatch modules to initialize
incorrectly. This patch removes dependence on the module notifier call
chain in favor of hard coding the corresponding function calls in the
module loader. This ensures that ftrace and livepatch code get called in
the correct order on patch module load and unload.

Fixes: 5156dca34a3e ("ftrace: Fix the race between ftrace and insmod")
Signed-off-by: Jessica Yu <jeyu@redhat.com>
Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
Reviewed-by: Petr Mladek <pmladek@suse.cz>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 0639dcc9819523a002de1149da5629d24bce039b..76dc15e171ebb38ece575f2e78d957ce7660c215 100644 (file)
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -604,6 +604,7 @@ extern int ftrace_arch_read_dyn_info(char *buf, int size);
 
 extern int skip_trace(unsigned long ip);
 extern void ftrace_module_init(struct module *mod);
+extern void ftrace_module_enable(struct module *mod);
 extern void ftrace_release_mod(struct module *mod);
 
 extern void ftrace_disable_daemon(void);
@@ -613,8 +614,9 @@ static inline int skip_trace(unsigned long ip) { return 0; }
 static inline int ftrace_force_update(void) { return 0; }
 static inline void ftrace_disable_daemon(void) { }
 static inline void ftrace_enable_daemon(void) { }
-static inline void ftrace_release_mod(struct module *mod) {}
-static inline void ftrace_module_init(struct module *mod) {}
+static inline void ftrace_module_init(struct module *mod) { }
+static inline void ftrace_module_enable(struct module *mod) { }
+static inline void ftrace_release_mod(struct module *mod) { }
 static inline __init int register_ftrace_command(struct ftrace_func_command *cmd)
 {
        return -EINVAL;

diff --git a/kernel/module.c b/kernel/module.c
index 8358f4697c0c3aea77aba802833660d4082b7c13..b05d466cfa02765727d234c3cf81f93def4a889e 100644 (file)
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -981,6 +981,8 @@ SYSCALL_DEFINE2(delete_module, const char __user *, name_user,
                mod->exit();
        blocking_notifier_call_chain(&module_notify_list,
                                     MODULE_STATE_GOING, mod);
+       ftrace_release_mod(mod);
+
        async_synchronize_full();
 
        /* Store the name of the last unloaded module for diagnostic purposes */
@@ -3295,6 +3297,7 @@ fail:
        module_put(mod);
        blocking_notifier_call_chain(&module_notify_list,
                                     MODULE_STATE_GOING, mod);
+       ftrace_release_mod(mod);
        free_module(mod);
        wake_up_all(&module_wq);
        return ret;
@@ -3371,6 +3374,7 @@ static int complete_formation(struct module *mod, struct load_info *info)
        mod->state = MODULE_STATE_COMING;
        mutex_unlock(&module_mutex);
 
+       ftrace_module_enable(mod);
        blocking_notifier_call_chain(&module_notify_list,
                                     MODULE_STATE_COMING, mod);
        return 0;

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index eca592f977b260689dc48911f867375b20ad5c8b..57a6eea8469408e7aba78669107eb3a1740362e4 100644 (file)
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -4961,7 +4961,7 @@ void ftrace_release_mod(struct module *mod)
        mutex_unlock(&ftrace_lock);
 }
 
-static void ftrace_module_enable(struct module *mod)
+void ftrace_module_enable(struct module *mod)
 {
        struct dyn_ftrace *rec;
        struct ftrace_page *pg;
@@ -5038,38 +5038,8 @@ void ftrace_module_init(struct module *mod)
        ftrace_process_locs(mod, mod->ftrace_callsites,
                            mod->ftrace_callsites + mod->num_ftrace_callsites);
 }
-
-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_module_enable(mod);
-               break;
-       case MODULE_STATE_GOING:
-               ftrace_release_mod(mod);
-               break;
-       default:
-               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 = INT_MIN,    /* Run after anything that can remove kprobes */
-};
-
 void __init ftrace_init(void)
 {
        extern unsigned long __start_mcount_loc[];
@@ -5098,10 +5068,6 @@ 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 exit notifier\n");
-
        set_ftrace_early_filters();
 
        return;