From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753373AbdJHVdV (ORCPT ); Sun, 8 Oct 2017 17:33:21 -0400 Received: from mail-pf0-f180.google.com ([209.85.192.180]:50680 "EHLO mail-pf0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751365AbdJHVdT (ORCPT ); Sun, 8 Oct 2017 17:33:19 -0400 X-Google-Smtp-Source: AOwi7QBsPxI2g7u7Qr5pqfS3q9MSb6ljVXFumwiSwjXj1GwrtMbuXV8lAQNLHJ7XD9ENiBy0MbmYHQ== From: Joel Fernandes To: linux-kernel@vger.kernel.org, Steven Rostedt Cc: Joel Fernandes , Jessica Yu Subject: [PATCH RFC] ftrace: Clear hashes of saved init functions Date: Sun, 8 Oct 2017 14:33:04 -0700 Message-Id: <20171008213304.155783-1-joelaf@google.com> X-Mailer: git-send-email 2.14.2.920.gcf0c67979c-goog Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Filters are supposed to be saved for init functions, however module init memory is freed after module init which also frees the ftrace dyn records. However, the filters are still left as is, this patch uses the mod_map infrastructure added by Steven to clear the hashes of the saved init functions when the module is unloaded. This fixes the following sequence of commands for a module: ================================================ void bar(void) { printk(KERN_INFO "bar!\n"); } void foo(void) { printk(KERN_INFO "foo!\n"); bar(); } static int __init hello_init(void) { printk(KERN_INFO "Hello world!\n"); foo(); return 0; } static void __exit hello_cleanup(void) { printk(KERN_INFO "Cleaning up module.\n"); } module_init(hello_init); module_exit(hello_cleanup); ================================================ Commands: echo '*:mod:test' > /d/tracing/set_ftrace_filter echo function > /d/tracing/current_tracer modprobe test rmmod test sleep 1 modprobe test cat /d/tracing/set_ftrace_filter Behavior without patch: Init function is still in the filter Expected behavior: Shouldn't have any of the filters set Cc: Jessica Yu Cc: Steven Rostedt Signed-off-by: Joel Fernandes --- kernel/trace/ftrace.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 48 insertions(+) diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 9e99bd55732e..e3f8372fb053 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -5711,6 +5711,42 @@ static int referenced_filters(struct dyn_ftrace *rec) return cnt; } +static void +clear_mod_func_from_hash(struct ftrace_mod_func *func, struct ftrace_hash *hash) +{ + struct ftrace_func_entry *entry; + + if (ftrace_hash_empty(hash)) + return; + + entry = __ftrace_lookup_ip(hash, func->ip); + + /* + * Do not allow this rec to match again. + * Yeah, it may waste some memory, but will be removed + * if/when the hash is modified again. + */ + if (entry) + entry->ip = 0; +} + +static void +clear_mod_func_from_hashes(struct ftrace_mod_func *func) +{ + struct trace_array *tr; + + mutex_lock(&trace_types_lock); + list_for_each_entry(tr, &ftrace_trace_arrays, list) { + if (!tr->ops || !tr->ops->func_hash) + continue; + mutex_lock(&tr->ops->func_hash->regex_lock); + clear_mod_func_from_hash(func, tr->ops->func_hash->filter_hash); + clear_mod_func_from_hash(func, tr->ops->func_hash->notrace_hash); + mutex_unlock(&tr->ops->func_hash->regex_lock); + } + mutex_unlock(&trace_types_lock); +} + static void clear_mod_from_hash(struct ftrace_page *pg, struct ftrace_hash *hash) { @@ -5771,12 +5807,24 @@ void ftrace_release_mod(struct module *mod) { struct ftrace_mod_map *mod_map; struct ftrace_mod_map *n; + struct ftrace_mod_func *mod_func; struct dyn_ftrace *rec; struct ftrace_page **last_pg; struct ftrace_page *tmp_page = NULL; struct ftrace_page *pg; int order; + /* mod_map is freed via call_rcu_sched() */ + preempt_disable(); + list_for_each_entry_rcu(mod_map, &ftrace_mod_maps, list) { + if (mod_map->mod != mod) + continue; + list_for_each_entry_rcu(mod_func, &mod_map->funcs, list) { + clear_mod_func_from_hashes(mod_func); + } + } + preempt_enable(); + mutex_lock(&ftrace_lock); if (ftrace_disabled) -- 2.14.2.920.gcf0c67979c-goog