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Subject[for-next][PATCH 08/12] tracing/probe: Add trace_event_file access APIs for trace_probe
From: Masami Hiramatsu <mhiramat@kernel.org>

Add trace_event_file access APIs for trace_probe data structure.
This simplifies enabling/disabling operations in uprobe and kprobe
events so that those don't touch deep inside the trace_probe.

This also removing a redundant synchronization when the
kprobe event is used from perf, since the perf itself uses
tracepoint_synchronize_unregister() after disabling (ftrace-
defined) event, thus we don't have to synchronize in that
path. Also we don't need to identify local trace_kprobe too
anymore.

Link: http://lkml.kernel.org/r/155931584587.28323.372301976283354629.stgit@devnote2

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
kernel/trace/trace_kprobe.c | 85 +++++++++++++------------------------
kernel/trace/trace_probe.c | 47 ++++++++++++++++++++
kernel/trace/trace_probe.h | 36 +++++++++-------
kernel/trace/trace_uprobe.c | 42 ++++++------------
4 files changed, 109 insertions(+), 101 deletions(-)

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 7f802ee27266..87a52094378c 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -290,34 +290,27 @@ static inline int __enable_trace_kprobe(struct trace_kprobe *tk)
static int
enable_trace_kprobe(struct trace_kprobe *tk, struct trace_event_file *file)
{
- struct event_file_link *link;
+ bool enabled = trace_probe_is_enabled(&tk->tp);
int ret = 0;

if (file) {
- link = kmalloc(sizeof(*link), GFP_KERNEL);
- if (!link) {
- ret = -ENOMEM;
- goto out;
- }
-
- link->file = file;
- list_add_tail_rcu(&link->list, &tk->tp.files);
+ ret = trace_probe_add_file(&tk->tp, file);
+ if (ret)
+ return ret;
+ } else
+ tk->tp.flags |= TP_FLAG_PROFILE;

- tk->tp.flags |= TP_FLAG_TRACE;
- ret = __enable_trace_kprobe(tk);
- if (ret) {
- list_del_rcu(&link->list);
- kfree(link);
- tk->tp.flags &= ~TP_FLAG_TRACE;
- }
+ if (enabled)
+ return 0;

- } else {
- tk->tp.flags |= TP_FLAG_PROFILE;
- ret = __enable_trace_kprobe(tk);
- if (ret)
+ ret = __enable_trace_kprobe(tk);
+ if (ret) {
+ if (file)
+ trace_probe_remove_file(&tk->tp, file);
+ else
tk->tp.flags &= ~TP_FLAG_PROFILE;
}
- out:
+
return ret;
}

@@ -328,54 +321,34 @@ enable_trace_kprobe(struct trace_kprobe *tk, struct trace_event_file *file)
static int
disable_trace_kprobe(struct trace_kprobe *tk, struct trace_event_file *file)
{
- struct event_file_link *link = NULL;
- int wait = 0;
+ struct trace_probe *tp = &tk->tp;
int ret = 0;

if (file) {
- link = find_event_file_link(&tk->tp, file);
- if (!link) {
- ret = -EINVAL;
- goto out;
- }
-
- list_del_rcu(&link->list);
- wait = 1;
- if (!list_empty(&tk->tp.files))
+ if (!trace_probe_get_file_link(tp, file))
+ return -ENOENT;
+ if (!trace_probe_has_single_file(tp))
goto out;
-
- tk->tp.flags &= ~TP_FLAG_TRACE;
+ tp->flags &= ~TP_FLAG_TRACE;
} else
- tk->tp.flags &= ~TP_FLAG_PROFILE;
+ tp->flags &= ~TP_FLAG_PROFILE;

- if (!trace_probe_is_enabled(&tk->tp) && trace_probe_is_registered(&tk->tp)) {
+ if (!trace_probe_is_enabled(tp) && trace_probe_is_registered(tp)) {
if (trace_kprobe_is_return(tk))
disable_kretprobe(&tk->rp);
else
disable_kprobe(&tk->rp.kp);
- wait = 1;
}

- /*
- * if tk is not added to any list, it must be a local trace_kprobe
- * created with perf_event_open. We don't need to wait for these
- * trace_kprobes
- */
- if (list_empty(&tk->devent.list))
- wait = 0;
out:
- if (wait) {
+ if (file)
/*
- * Synchronize with kprobe_trace_func/kretprobe_trace_func
- * to ensure disabled (all running handlers are finished).
- * This is not only for kfree(), but also the caller,
- * trace_remove_event_call() supposes it for releasing
- * event_call related objects, which will be accessed in
- * the kprobe_trace_func/kretprobe_trace_func.
+ * Synchronization is done in below function. For perf event,
+ * file == NULL and perf_trace_event_unreg() calls
+ * tracepoint_synchronize_unregister() to ensure synchronize
+ * event. We don't need to care about it.
*/
- synchronize_rcu();
- kfree(link); /* Ignored if link == NULL */
- }
+ trace_probe_remove_file(tp, file);

return ret;
}
@@ -1044,7 +1017,7 @@ kprobe_trace_func(struct trace_kprobe *tk, struct pt_regs *regs)
{
struct event_file_link *link;

- list_for_each_entry_rcu(link, &tk->tp.files, list)
+ trace_probe_for_each_link_rcu(link, &tk->tp)
__kprobe_trace_func(tk, regs, link->file);
}
NOKPROBE_SYMBOL(kprobe_trace_func);
@@ -1094,7 +1067,7 @@ kretprobe_trace_func(struct trace_kprobe *tk, struct kretprobe_instance *ri,
{
struct event_file_link *link;

- list_for_each_entry_rcu(link, &tk->tp.files, list)
+ trace_probe_for_each_link_rcu(link, &tk->tp)
__kretprobe_trace_func(tk, ri, regs, link->file);
}
NOKPROBE_SYMBOL(kretprobe_trace_func);
diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
index 509a26024b4f..abb05608a09d 100644
--- a/kernel/trace/trace_probe.c
+++ b/kernel/trace/trace_probe.c
@@ -936,3 +936,50 @@ int trace_probe_register_event_call(struct trace_probe *tp)

return ret;
}
+
+int trace_probe_add_file(struct trace_probe *tp, struct trace_event_file *file)
+{
+ struct event_file_link *link;
+
+ link = kmalloc(sizeof(*link), GFP_KERNEL);
+ if (!link)
+ return -ENOMEM;
+
+ link->file = file;
+ INIT_LIST_HEAD(&link->list);
+ list_add_tail_rcu(&link->list, &tp->files);
+ tp->flags |= TP_FLAG_TRACE;
+ return 0;
+}
+
+struct event_file_link *trace_probe_get_file_link(struct trace_probe *tp,
+ struct trace_event_file *file)
+{
+ struct event_file_link *link;
+
+ trace_probe_for_each_link(link, tp) {
+ if (link->file == file)
+ return link;
+ }
+
+ return NULL;
+}
+
+int trace_probe_remove_file(struct trace_probe *tp,
+ struct trace_event_file *file)
+{
+ struct event_file_link *link;
+
+ link = trace_probe_get_file_link(tp, file);
+ if (!link)
+ return -ENOENT;
+
+ list_del_rcu(&link->list);
+ synchronize_rcu();
+ kfree(link);
+
+ if (list_empty(&tp->files))
+ tp->flags &= ~TP_FLAG_TRACE;
+
+ return 0;
+}
diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
index 01d7b222e004..ab02007e131d 100644
--- a/kernel/trace/trace_probe.h
+++ b/kernel/trace/trace_probe.h
@@ -248,16 +248,32 @@ static inline bool trace_probe_is_registered(struct trace_probe *tp)
return !!(tp->flags & TP_FLAG_REGISTERED);
}

-int trace_probe_init(struct trace_probe *tp, const char *event,
- const char *group);
-void trace_probe_cleanup(struct trace_probe *tp);
-int trace_probe_register_event_call(struct trace_probe *tp);
static inline int trace_probe_unregister_event_call(struct trace_probe *tp)
{
/* tp->event is unregistered in trace_remove_event_call() */
return trace_remove_event_call(&tp->call);
}

+static inline bool trace_probe_has_single_file(struct trace_probe *tp)
+{
+ return !!list_is_singular(&tp->files);
+}
+
+int trace_probe_init(struct trace_probe *tp, const char *event,
+ const char *group);
+void trace_probe_cleanup(struct trace_probe *tp);
+int trace_probe_register_event_call(struct trace_probe *tp);
+int trace_probe_add_file(struct trace_probe *tp, struct trace_event_file *file);
+int trace_probe_remove_file(struct trace_probe *tp,
+ struct trace_event_file *file);
+struct event_file_link *trace_probe_get_file_link(struct trace_probe *tp,
+ struct trace_event_file *file);
+
+#define trace_probe_for_each_link(pos, tp) \
+ list_for_each_entry(pos, &(tp)->files, list)
+#define trace_probe_for_each_link_rcu(pos, tp) \
+ list_for_each_entry_rcu(pos, &(tp)->files, list)
+
/* Check the name is good for event/group/fields */
static inline bool is_good_name(const char *name)
{
@@ -270,18 +286,6 @@ static inline bool is_good_name(const char *name)
return true;
}

-static inline struct event_file_link *
-find_event_file_link(struct trace_probe *tp, struct trace_event_file *file)
-{
- struct event_file_link *link;
-
- list_for_each_entry(link, &tp->files, list)
- if (link->file == file)
- return link;
-
- return NULL;
-}
-
#define TPARG_FL_RETURN BIT(0)
#define TPARG_FL_KERNEL BIT(1)
#define TPARG_FL_FENTRY BIT(2)
diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index c262494fa793..a9f8045b6695 100644
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -863,7 +863,7 @@ static int uprobe_trace_func(struct trace_uprobe *tu, struct pt_regs *regs,
return 0;

rcu_read_lock();
- list_for_each_entry_rcu(link, &tu->tp.files, list)
+ trace_probe_for_each_link_rcu(link, &tu->tp)
__uprobe_trace_func(tu, 0, regs, ucb, dsize, link->file);
rcu_read_unlock();

@@ -877,7 +877,7 @@ static void uretprobe_trace_func(struct trace_uprobe *tu, unsigned long func,
struct event_file_link *link;

rcu_read_lock();
- list_for_each_entry_rcu(link, &tu->tp.files, list)
+ trace_probe_for_each_link_rcu(link, &tu->tp)
__uprobe_trace_func(tu, func, regs, ucb, dsize, link->file);
rcu_read_unlock();
}
@@ -924,21 +924,15 @@ probe_event_enable(struct trace_uprobe *tu, struct trace_event_file *file,
filter_func_t filter)
{
bool enabled = trace_probe_is_enabled(&tu->tp);
- struct event_file_link *link = NULL;
int ret;

if (file) {
if (tu->tp.flags & TP_FLAG_PROFILE)
return -EINTR;

- link = kmalloc(sizeof(*link), GFP_KERNEL);
- if (!link)
- return -ENOMEM;
-
- link->file = file;
- list_add_tail_rcu(&link->list, &tu->tp.files);
-
- tu->tp.flags |= TP_FLAG_TRACE;
+ ret = trace_probe_add_file(&tu->tp, file);
+ if (ret < 0)
+ return ret;
} else {
if (tu->tp.flags & TP_FLAG_TRACE)
return -EINTR;
@@ -973,13 +967,11 @@ probe_event_enable(struct trace_uprobe *tu, struct trace_event_file *file,
uprobe_buffer_disable();

err_flags:
- if (file) {
- list_del(&link->list);
- kfree(link);
- tu->tp.flags &= ~TP_FLAG_TRACE;
- } else {
+ if (file)
+ trace_probe_remove_file(&tu->tp, file);
+ else
tu->tp.flags &= ~TP_FLAG_PROFILE;
- }
+
return ret;
}

@@ -990,26 +982,18 @@ probe_event_disable(struct trace_uprobe *tu, struct trace_event_file *file)
return;

if (file) {
- struct event_file_link *link;
-
- link = find_event_file_link(&tu->tp, file);
- if (!link)
+ if (trace_probe_remove_file(&tu->tp, file) < 0)
return;

- list_del_rcu(&link->list);
- /* synchronize with u{,ret}probe_trace_func */
- synchronize_rcu();
- kfree(link);
-
- if (!list_empty(&tu->tp.files))
+ if (trace_probe_is_enabled(&tu->tp))
return;
- }
+ } else
+ tu->tp.flags &= ~TP_FLAG_PROFILE;

WARN_ON(!uprobe_filter_is_empty(&tu->filter));

uprobe_unregister(tu->inode, tu->offset, &tu->consumer);
tu->inode = NULL;
- tu->tp.flags &= file ? ~TP_FLAG_TRACE : ~TP_FLAG_PROFILE;

uprobe_buffer_disable();
}
--
2.20.1

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