Commit-ID: 31ba334836c0ac0039084859f14a5b96858493dc
Gitweb: http://git.kernel.org/tip/31ba334836c0ac0039084859f14a5b96858493dc
Author: Oleg Nesterov <oleg@xxxxxxxxxx>
AuthorDate: Mon, 4 Feb 2013 17:11:58 +0100
Committer: Oleg Nesterov <oleg@xxxxxxxxxx>
CommitDate: Fri, 8 Feb 2013 18:28:07 +0100
uprobes/perf: Teach trace_uprobe/perf code to pre-filter
Finally implement uprobe_perf_filter() which checks ->nr_systemwide or
->perf_events to figure out whether we need to insert the breakpoint.
uprobe_perf_open/close are changed to do uprobe_apply(true/false) when
the new perf event comes or goes away.
Note that currently this is very suboptimal:
- uprobe_register() called by TRACE_REG_PERF_REGISTER becomes a
heavy nop, consumer->filter() always returns F at this stage.
As it was already discussed we need uprobe_register_only() to
avoid the costly register_for_each_vma() when possible.
- uprobe_apply() is oftenly overkill. Unless "nr_systemwide != 0"
changes we need uprobe_apply_mm(), unapply_uprobe() is almost
what we need.
- uprobe_apply() can be simply avoided sometimes, see the next
changes.
Testing:
# perf probe -x /lib/libc.so.6 syscall
# perl -e 'syscall -1 while 1' &
[1] 530
# perf record -e probe_libc:syscall perl -e 'syscall -1 for 1..10; sleep 1'
# perf report --show-total-period
100.00% 10 perl libc-2.8.so [.] syscall
Before this patch:
# cat /sys/kernel/debug/tracing/uprobe_profile
/lib/libc.so.6 syscall 79291
A huge ->nrhit == 79291 reflects the fact that the background process
530 constantly hits this breakpoint too, even if doesn't contribute to
the output.
After the patch:
# cat /sys/kernel/debug/tracing/uprobe_profile
/lib/libc.so.6 syscall 10
This shows that only the target process was punished by int3.
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
---
kernel/trace/trace_uprobe.c | 46 ++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 43 insertions(+), 3 deletions(-)
diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index 2a74a93..b7850f5 100644
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -557,7 +557,12 @@ static inline bool is_trace_uprobe_enabled(struct trace_uprobe *tu)
return tu->flags & (TP_FLAG_TRACE | TP_FLAG_PROFILE);
}
-static int probe_event_enable(struct trace_uprobe *tu, int flag)
+typedef bool (*filter_func_t)(struct uprobe_consumer *self,
+ enum uprobe_filter_ctx ctx,
+ struct mm_struct *mm);
+
+static int
+probe_event_enable(struct trace_uprobe *tu, int flag, filter_func_t filter)
{
int ret = 0;
@@ -567,6 +572,7 @@ static int probe_event_enable(struct trace_uprobe *tu, int flag)
WARN_ON(!uprobe_filter_is_empty(&tu->filter));
tu->flags |= flag;
+ tu->consumer.filter = filter;
ret = uprobe_register(tu->inode, tu->offset, &tu->consumer);
if (ret)
tu->flags &= ~flag;
@@ -656,6 +662,22 @@ static int set_print_fmt(struct trace_uprobe *tu)
}
#ifdef CONFIG_PERF_EVENTS
+static bool
+__uprobe_perf_filter(struct trace_uprobe_filter *filter, struct mm_struct *mm)
+{
+ struct perf_event *event;
+
+ if (filter->nr_systemwide)
+ return true;
+
+ list_for_each_entry(event, &filter->perf_events, hw.tp_list) {
+ if (event->hw.tp_target->mm == mm)
+ return true;
+ }
+
+ return false;
+}
+
static int uprobe_perf_open(struct trace_uprobe *tu, struct perf_event *event)
{
write_lock(&tu->filter.rwlock);
@@ -665,6 +687,8 @@ static int uprobe_perf_open(struct trace_uprobe *tu, struct perf_event *event)
tu->filter.nr_systemwide++;
write_unlock(&tu->filter.rwlock);
+ uprobe_apply(tu->inode, tu->offset, &tu->consumer, true);
+
return 0;
}
@@ -677,9 +701,25 @@ static int uprobe_perf_close(struct trace_uprobe *tu, struct perf_event *event)
tu->filter.nr_systemwide--;
write_unlock(&tu->filter.rwlock);
+ uprobe_apply(tu->inode, tu->offset, &tu->consumer, false);
+
return 0;
}
+static bool uprobe_perf_filter(struct uprobe_consumer *uc,
+ enum uprobe_filter_ctx ctx, struct mm_struct *mm)
+{
+ struct trace_uprobe *tu;
+ int ret;
+
+ tu = container_of(uc, struct trace_uprobe, consumer);
+ read_lock(&tu->filter.rwlock);
+ ret = __uprobe_perf_filter(&tu->filter, mm);
+ read_unlock(&tu->filter.rwlock);
+
+ return ret;
+}
+
/* uprobe profile handler */
static void uprobe_perf_func(struct trace_uprobe *tu, struct pt_regs *regs)
{
@@ -722,7 +762,7 @@ int trace_uprobe_register(struct ftrace_event_call *event, enum trace_reg type,
switch (type) {
case TRACE_REG_REGISTER:
- return probe_event_enable(tu, TP_FLAG_TRACE);
+ return probe_event_enable(tu, TP_FLAG_TRACE, NULL);
case TRACE_REG_UNREGISTER:
probe_event_disable(tu, TP_FLAG_TRACE);
@@ -730,7 +770,7 @@ int trace_uprobe_register(struct ftrace_event_call *event, enum trace_reg type,
#ifdef CONFIG_PERF_EVENTS
case TRACE_REG_PERF_REGISTER:
- return probe_event_enable(tu, TP_FLAG_PROFILE);
+ return probe_event_enable(tu, TP_FLAG_PROFILE, uprobe_perf_filter);
case TRACE_REG_PERF_UNREGISTER:
probe_event_disable(tu, TP_FLAG_PROFILE);
--
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