lkml.org 
[lkml]   [2013]   [Feb]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[PATCH 5/7] 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@redhat.com>
---
kernel/trace/trace_uprobe.c | 46 ++++++++++++++++++++++++++++++++++++++++--
1 files changed, 43 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index f05ec32..5d5a261 100644
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -554,7 +554,12 @@ 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;

@@ -564,6 +569,7 @@ 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;
@@ -653,6 +659,22 @@ 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);
@@ -662,6 +684,8 @@ 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;
}

@@ -674,9 +698,25 @@ 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)
{
@@ -719,7 +759,7 @@ 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);
@@ -727,7 +767,7 @@ 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);
--
1.5.5.1


\
 
 \ /
  Last update: 2013-02-04 20:42    [W:0.568 / U:0.776 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site