uprobes: _register() should always do register_for_each_vma(true)

To support the filtering uprobe_register() should do
register_for_each_vma(true) every time the new consumer comes,
we need to install the previously nacked breakpoints.

Note:
	- uprobes_mutex[] should die, what it actually protects is
	  alloc_uprobe().

	- UPROBE_RUN_HANDLER should die too, obviously it can't work
	  unless uprobe has a single consumer. The consumer should
	  serialize with _register/_unregister itself. Or this flag
	  should live in uprobe_consumer->state.

	- Perhaps we can do some optimizations later. For example, if
	  filter_chain() never returns false uprobe can record this
	  fact and avoid the unnecessary register_for_each_vma().

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 9401990..d1d1394 100644 (file)
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -482,16 +482,12 @@ static void handler_chain(struct uprobe *uprobe, struct pt_regs *regs)
        up_read(&uprobe->consumer_rwsem);
 }
 
-/* Returns the previous consumer */
-static struct uprobe_consumer *
-consumer_add(struct uprobe *uprobe, struct uprobe_consumer *uc)
+static void consumer_add(struct uprobe *uprobe, struct uprobe_consumer *uc)
 {
        down_write(&uprobe->consumer_rwsem);
        uc->next = uprobe->consumers;
        uprobe->consumers = uc;
        up_write(&uprobe->consumer_rwsem);
-
-       return uc->next;
 }
 
 /*
@@ -820,9 +816,15 @@ static int register_for_each_vma(struct uprobe *uprobe, bool is_register)
        return err;
 }
 
-static int __uprobe_register(struct uprobe *uprobe)
+static int __uprobe_register(struct uprobe *uprobe, struct uprobe_consumer *uc)
 {
-       return register_for_each_vma(uprobe, true);
+       int err;
+
+       consumer_add(uprobe, uc);
+       err = register_for_each_vma(uprobe, true);
+       if (!err) /* TODO: pointless unless the first consumer */
+               set_bit(UPROBE_RUN_HANDLER, &uprobe->flags);
+       return err;
 }
 
 static void __uprobe_unregister(struct uprobe *uprobe, struct uprobe_consumer *uc)
@@ -867,21 +869,14 @@ int uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer *
        if (offset > i_size_read(inode))
                return -EINVAL;
 
-       ret = 0;
+       ret = -ENOMEM;
        mutex_lock(uprobes_hash(inode));
        uprobe = alloc_uprobe(inode, offset);
-
-       if (!uprobe) {
-               ret = -ENOMEM;
-       } else if (!consumer_add(uprobe, uc)) {
-               ret = __uprobe_register(uprobe);
-               if (ret) {
+       if (uprobe) {
+               ret = __uprobe_register(uprobe, uc);
+               if (ret)
                        __uprobe_unregister(uprobe, uc);
-               } else {
-                       set_bit(UPROBE_RUN_HANDLER, &uprobe->flags);
-               }
        }
-
        mutex_unlock(uprobes_hash(inode));
        if (uprobe)
                put_uprobe(uprobe);