uprobes/perf: Teach trace_uprobe/perf code to use UPROBE_HANDLER_REMOVE

Change uprobe_trace_func() and uprobe_perf_func() to return "int". Change
uprobe_dispatcher() to return "trace_ret | perf_ret" although this is not
needed, currently TP_FLAG_TRACE/TP_FLAG_PROFILE are mutually exclusive.

The only functional change is that uprobe_perf_func() checks the filtering
too and returns UPROBE_HANDLER_REMOVE if nobody wants to trace current.

Testing:

	# perf probe -x /lib/libc.so.6 syscall

	# perf record -e probe_libc:syscall -i perl -e 'fork; syscall -1 for 1..10; wait'

	# 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				20

A child process doesn't have a counter, but still it hits this breakoint
"copied" by dup_mmap().

After the patch:

	# cat /sys/kernel/debug/tracing/uprobe_profile
		/lib/libc.so.6 syscall				11

The child process hits this int3 only once and does unapply_uprobe().

Signed-off-by: Oleg Nesterov <oleg@redhat.com>

diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index b7850f5..2399f14 100644 (file)
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -486,7 +486,7 @@ static const struct file_operations uprobe_profile_ops = {
 };
 
 /* uprobe handler */
-static void uprobe_trace_func(struct trace_uprobe *tu, struct pt_regs *regs)
+static int uprobe_trace_func(struct trace_uprobe *tu, struct pt_regs *regs)
 {
        struct uprobe_trace_entry_head *entry;
        struct ring_buffer_event *event;
@@ -504,7 +504,7 @@ static void uprobe_trace_func(struct trace_uprobe *tu, struct pt_regs *regs)
        event = trace_current_buffer_lock_reserve(&buffer, call->event.type,
                                                  size, irq_flags, pc);
        if (!event)
-               return;
+               return 0;
 
        entry = ring_buffer_event_data(event);
        entry->ip = instruction_pointer(task_pt_regs(current));
@@ -514,6 +514,8 @@ static void uprobe_trace_func(struct trace_uprobe *tu, struct pt_regs *regs)
 
        if (!filter_current_check_discard(buffer, call, entry, event))
                trace_buffer_unlock_commit(buffer, event, irq_flags, pc);
+
+       return 0;
 }
 
 /* Event entry printers */
@@ -721,7 +723,7 @@ static bool uprobe_perf_filter(struct uprobe_consumer *uc,
 }
 
 /* uprobe profile handler */
-static void uprobe_perf_func(struct trace_uprobe *tu, struct pt_regs *regs)
+static int uprobe_perf_func(struct trace_uprobe *tu, struct pt_regs *regs)
 {
        struct ftrace_event_call *call = &tu->call;
        struct uprobe_trace_entry_head *entry;
@@ -730,11 +732,14 @@ static void uprobe_perf_func(struct trace_uprobe *tu, struct pt_regs *regs)
        int size, __size, i;
        int rctx;
 
+       if (!uprobe_perf_filter(&tu->consumer, 0, current->mm))
+               return UPROBE_HANDLER_REMOVE;
+
        __size = sizeof(*entry) + tu->size;
        size = ALIGN(__size + sizeof(u32), sizeof(u64));
        size -= sizeof(u32);
        if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE, "profile buffer not large enough"))
-               return;
+               return 0;
 
        preempt_disable();
 
@@ -752,6 +757,7 @@ static void uprobe_perf_func(struct trace_uprobe *tu, struct pt_regs *regs)
 
  out:
        preempt_enable();
+       return 0;
 }
 #endif /* CONFIG_PERF_EVENTS */
 
@@ -792,18 +798,19 @@ int trace_uprobe_register(struct ftrace_event_call *event, enum trace_reg type,
 static int uprobe_dispatcher(struct uprobe_consumer *con, struct pt_regs *regs)
 {
        struct trace_uprobe *tu;
+       int ret = 0;
 
        tu = container_of(con, struct trace_uprobe, consumer);
        tu->nhit++;
 
        if (tu->flags & TP_FLAG_TRACE)
-               uprobe_trace_func(tu, regs);
+               ret |= uprobe_trace_func(tu, regs);
 
 #ifdef CONFIG_PERF_EVENTS
        if (tu->flags & TP_FLAG_PROFILE)
-               uprobe_perf_func(tu, regs);
+               ret |= uprobe_perf_func(tu, regs);
 #endif
-       return 0;
+       return ret;
 }
 
 static struct trace_event_functions uprobe_funcs = {