forked from luck/tmp_suning_uos_patched
tracing/kprobes: Kill probe_enable_lock
enable_trace_probe() and disable_trace_probe() should not worry about
serialization, the caller (perf_trace_init or __ftrace_set_clr_event)
holds event_mutex.
They are also called by kprobe_trace_self_tests_init(), but this __init
function can't race with itself or trace_events.c
And note that this code depended on event_mutex even before 41a7dd420c
which introduced probe_enable_lock. In fact it assumes that the caller
kprobe_register() can never race with itself. Otherwise, say, tp->flags
manipulations are racy.
Link: http://lkml.kernel.org/r/20130620173809.GA13158@redhat.com
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
parent
288e984e62
commit
3fe3d6193e
@ -183,16 +183,15 @@ static struct trace_probe *find_trace_probe(const char *event,
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return NULL;
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return NULL;
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}
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}
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/*
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* This and enable_trace_probe/disable_trace_probe rely on event_mutex
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* held by the caller, __ftrace_set_clr_event().
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*/
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static int trace_probe_nr_files(struct trace_probe *tp)
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static int trace_probe_nr_files(struct trace_probe *tp)
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{
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{
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struct ftrace_event_file **file;
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struct ftrace_event_file **file = rcu_dereference_raw(tp->files);
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int ret = 0;
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int ret = 0;
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/*
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* Since all tp->files updater is protected by probe_enable_lock,
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* we don't need to lock an rcu_read_lock.
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*/
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file = rcu_dereference_raw(tp->files);
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if (file)
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if (file)
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while (*(file++))
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while (*(file++))
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ret++;
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ret++;
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@ -200,8 +199,6 @@ static int trace_probe_nr_files(struct trace_probe *tp)
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return ret;
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return ret;
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}
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}
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static DEFINE_MUTEX(probe_enable_lock);
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/*
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/*
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* Enable trace_probe
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* Enable trace_probe
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* if the file is NULL, enable "perf" handler, or enable "trace" handler.
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* if the file is NULL, enable "perf" handler, or enable "trace" handler.
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@ -211,8 +208,6 @@ enable_trace_probe(struct trace_probe *tp, struct ftrace_event_file *file)
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{
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{
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int ret = 0;
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int ret = 0;
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mutex_lock(&probe_enable_lock);
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if (file) {
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if (file) {
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struct ftrace_event_file **new, **old;
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struct ftrace_event_file **new, **old;
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int n = trace_probe_nr_files(tp);
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int n = trace_probe_nr_files(tp);
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@ -223,7 +218,7 @@ enable_trace_probe(struct trace_probe *tp, struct ftrace_event_file *file)
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GFP_KERNEL);
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GFP_KERNEL);
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if (!new) {
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if (!new) {
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ret = -ENOMEM;
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ret = -ENOMEM;
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goto out_unlock;
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goto out;
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}
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}
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memcpy(new, old, n * sizeof(struct ftrace_event_file *));
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memcpy(new, old, n * sizeof(struct ftrace_event_file *));
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new[n] = file;
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new[n] = file;
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@ -246,10 +241,7 @@ enable_trace_probe(struct trace_probe *tp, struct ftrace_event_file *file)
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else
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else
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ret = enable_kprobe(&tp->rp.kp);
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ret = enable_kprobe(&tp->rp.kp);
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}
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}
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out:
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out_unlock:
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mutex_unlock(&probe_enable_lock);
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return ret;
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return ret;
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}
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}
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@ -282,8 +274,6 @@ disable_trace_probe(struct trace_probe *tp, struct ftrace_event_file *file)
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{
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{
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int ret = 0;
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int ret = 0;
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mutex_lock(&probe_enable_lock);
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if (file) {
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if (file) {
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struct ftrace_event_file **new, **old;
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struct ftrace_event_file **new, **old;
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int n = trace_probe_nr_files(tp);
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int n = trace_probe_nr_files(tp);
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@ -292,7 +282,7 @@ disable_trace_probe(struct trace_probe *tp, struct ftrace_event_file *file)
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old = rcu_dereference_raw(tp->files);
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old = rcu_dereference_raw(tp->files);
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if (n == 0 || trace_probe_file_index(tp, file) < 0) {
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if (n == 0 || trace_probe_file_index(tp, file) < 0) {
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ret = -EINVAL;
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ret = -EINVAL;
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goto out_unlock;
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goto out;
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}
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}
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if (n == 1) { /* Remove the last file */
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if (n == 1) { /* Remove the last file */
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@ -303,7 +293,7 @@ disable_trace_probe(struct trace_probe *tp, struct ftrace_event_file *file)
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GFP_KERNEL);
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GFP_KERNEL);
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if (!new) {
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if (!new) {
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ret = -ENOMEM;
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ret = -ENOMEM;
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goto out_unlock;
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goto out;
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}
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}
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/* This copy & check loop copies the NULL stopper too */
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/* This copy & check loop copies the NULL stopper too */
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@ -326,10 +316,7 @@ disable_trace_probe(struct trace_probe *tp, struct ftrace_event_file *file)
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else
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else
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disable_kprobe(&tp->rp.kp);
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disable_kprobe(&tp->rp.kp);
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}
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}
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out:
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out_unlock:
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mutex_unlock(&probe_enable_lock);
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return ret;
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return ret;
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}
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}
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@ -1214,6 +1201,12 @@ kretprobe_perf_func(struct trace_probe *tp, struct kretprobe_instance *ri,
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}
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}
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#endif /* CONFIG_PERF_EVENTS */
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#endif /* CONFIG_PERF_EVENTS */
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/*
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* called by perf_trace_init() or __ftrace_set_clr_event() under event_mutex.
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*
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* kprobe_trace_self_tests_init() does enable_trace_probe/disable_trace_probe
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* lockless, but we can't race with this __init function.
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*/
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static __kprobes
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static __kprobes
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int kprobe_register(struct ftrace_event_call *event,
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int kprobe_register(struct ftrace_event_call *event,
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enum trace_reg type, void *data)
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enum trace_reg type, void *data)
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@ -1379,6 +1372,10 @@ find_trace_probe_file(struct trace_probe *tp, struct trace_array *tr)
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return NULL;
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return NULL;
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}
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}
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/*
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* Nobody but us can call enable_trace_probe/disable_trace_probe at this
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* stage, we can do this lockless.
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*/
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static __init int kprobe_trace_self_tests_init(void)
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static __init int kprobe_trace_self_tests_init(void)
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{
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{
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int ret, warn = 0;
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int ret, warn = 0;
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