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Subject[PATCH 4/7] uprobes/perf: Teach trace_uprobe/perf code to track the active perf_event's
Introduce "struct trace_uprobe_filter" which records the "active"
perf_event's attached to ftrace_event_call. For the start we simply
use list_head, we can optimize this later if needed. For example, we
do not really need to record an event with ->parent != NULL, we can
rely on parent->child_list. And we can certainly do some optimizations
for the case when 2 events have the same ->tp_target or tp_target->mm.

Change trace_uprobe_register() to process TRACE_REG_PERF_OPEN/CLOSE
and add/del this perf_event to the list.

We can probably avoid any locking, but lets start with the "obvioulsy
correct" trace_uprobe_filter->rwlock which protects everything.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
kernel/trace/trace_uprobe.c | 55 +++++++++++++++++++++++++++++++++++++++++++
1 files changed, 55 insertions(+), 0 deletions(-)

diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index 0a9a8de..f05ec32 100644
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -28,6 +28,12 @@

#define UPROBE_EVENT_SYSTEM "uprobes"

+struct trace_uprobe_filter {
+ rwlock_t rwlock;
+ int nr_systemwide;
+ struct list_head perf_events;
+};
+
/*
* uprobe event core functions
*/
@@ -35,6 +41,7 @@ struct trace_uprobe {
struct list_head list;
struct ftrace_event_class class;
struct ftrace_event_call call;
+ struct trace_uprobe_filter filter;
struct uprobe_consumer consumer;
struct inode *inode;
char *filename;
@@ -58,6 +65,18 @@ static LIST_HEAD(uprobe_list);

static int uprobe_dispatcher(struct uprobe_consumer *con, struct pt_regs *regs);

+static inline void init_trace_uprobe_filter(struct trace_uprobe_filter *filter)
+{
+ rwlock_init(&filter->rwlock);
+ filter->nr_systemwide = 0;
+ INIT_LIST_HEAD(&filter->perf_events);
+}
+
+static inline bool uprobe_filter_is_empty(struct trace_uprobe_filter *filter)
+{
+ return !filter->nr_systemwide && list_empty(&filter->perf_events);
+}
+
/*
* Allocate new trace_uprobe and initialize it (including uprobes).
*/
@@ -87,6 +106,7 @@ alloc_trace_uprobe(const char *group, const char *event, int nargs)

INIT_LIST_HEAD(&tu->list);
tu->consumer.handler = uprobe_dispatcher;
+ init_trace_uprobe_filter(&tu->filter);
return tu;

error:
@@ -541,6 +561,8 @@ static int probe_event_enable(struct trace_uprobe *tu, int flag)
if (is_trace_uprobe_enabled(tu))
return -EINTR;

+ WARN_ON(!uprobe_filter_is_empty(&tu->filter));
+
tu->flags |= flag;
ret = uprobe_register(tu->inode, tu->offset, &tu->consumer);
if (ret)
@@ -554,6 +576,8 @@ static void probe_event_disable(struct trace_uprobe *tu, int flag)
if (!is_trace_uprobe_enabled(tu))
return;

+ WARN_ON(!uprobe_filter_is_empty(&tu->filter));
+
uprobe_unregister(tu->inode, tu->offset, &tu->consumer);
tu->flags &= ~flag;
}
@@ -629,6 +653,30 @@ static int set_print_fmt(struct trace_uprobe *tu)
}

#ifdef CONFIG_PERF_EVENTS
+static int uprobe_perf_open(struct trace_uprobe *tu, struct perf_event *event)
+{
+ write_lock(&tu->filter.rwlock);
+ if (event->hw.tp_target)
+ list_add(&event->hw.tp_list, &tu->filter.perf_events);
+ else
+ tu->filter.nr_systemwide++;
+ write_unlock(&tu->filter.rwlock);
+
+ return 0;
+}
+
+static int uprobe_perf_close(struct trace_uprobe *tu, struct perf_event *event)
+{
+ write_lock(&tu->filter.rwlock);
+ if (event->hw.tp_target)
+ list_del(&event->hw.tp_list);
+ else
+ tu->filter.nr_systemwide--;
+ write_unlock(&tu->filter.rwlock);
+
+ return 0;
+}
+
/* uprobe profile handler */
static void uprobe_perf_func(struct trace_uprobe *tu, struct pt_regs *regs)
{
@@ -684,6 +732,13 @@ int trace_uprobe_register(struct ftrace_event_call *event, enum trace_reg type,
case TRACE_REG_PERF_UNREGISTER:
probe_event_disable(tu, TP_FLAG_PROFILE);
return 0;
+
+ case TRACE_REG_PERF_OPEN:
+ return uprobe_perf_open(tu, data);
+
+ case TRACE_REG_PERF_CLOSE:
+ return uprobe_perf_close(tu, data);
+
#endif
default:
return 0;
--
1.5.5.1


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