uprobes: Kill uprobe_consumer->filter()

uprobe_consumer->filter() is pointless in its current form, kill it.

We will add it back, but with the different signature/semantics. Perhaps
we will even re-introduce the callsite in handler_chain(), but not to
just skip uc->handler().
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

include/linux/uprobes.h

@@ -37,11 +37,6 @@ struct inode;
 
 struct uprobe_consumer {
 	int (*handler)(struct uprobe_consumer *self, struct pt_regs *regs);
-	/*
-	 * filter is optional; If a filter exists, handler is run
-	 * if and only if filter returns true.
-	 */
-	bool (*filter)(struct uprobe_consumer *self, struct task_struct *task);
 
 	struct uprobe_consumer *next;
 };

kernel/events/uprobes.c

@@ -477,10 +477,8 @@ static void handler_chain(struct uprobe *uprobe, struct pt_regs *regs)
 		return;
 
 	down_read(&uprobe->consumer_rwsem);
-	for (uc = uprobe->consumers; uc; uc = uc->next) {
-		if (!uc->filter || uc->filter(uc, current))
+	for (uc = uprobe->consumers; uc; uc = uc->next)
 		uc->handler(uc, regs);
-	}
 	up_read(&uprobe->consumer_rwsem);
 }
 

kernel/trace/trace_uprobe.c

@@ -550,7 +550,6 @@ static int probe_event_enable(struct trace_uprobe *tu, int flag)
 		return -EINTR;
 
 	utc->cons.handler = uprobe_dispatcher;
-	utc->cons.filter = NULL;
 	ret = uprobe_register(tu->inode, tu->offset, &utc->cons);
 	if (ret) {
 		kfree(utc);