Commit 31ba3348 authored by Oleg Nesterov's avatar Oleg Nesterov

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: default avatarOleg Nesterov <oleg@redhat.com>
parent 736288ba
......@@ -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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