uprobes: Introduce free_ret_instance()

We can simplify uprobe_free_utask() and handle_uretprobe_chain()
if we add a simple helper which does put_uprobe/kfree and
returns the ->next return_instance.

Tested-by: Pratyush Anand <panand@redhat.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: Anton Arapov <arapov@gmail.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20150721134006.GA4740@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index a9847b4..d8c702f 100644 (file)
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1378,6 +1378,14 @@ unsigned long uprobe_get_trap_addr(struct pt_regs *regs)
        return instruction_pointer(regs);
 }
 
+static struct return_instance *free_ret_instance(struct return_instance *ri)
+{
+       struct return_instance *next = ri->next;
+       put_uprobe(ri->uprobe);
+       kfree(ri);
+       return next;
+}
+
 /*
  * Called with no locks held.
  * Called in context of a exiting or a exec-ing thread.
@@ -1385,7 +1393,7 @@ unsigned long uprobe_get_trap_addr(struct pt_regs *regs)
 void uprobe_free_utask(struct task_struct *t)
 {
        struct uprobe_task *utask = t->utask;
-       struct return_instance *ri, *tmp;
+       struct return_instance *ri;
 
        if (!utask)
                return;
@@ -1394,13 +1402,8 @@ void uprobe_free_utask(struct task_struct *t)
                put_uprobe(utask->active_uprobe);
 
        ri = utask->return_instances;
-       while (ri) {
-               tmp = ri;
-               ri = ri->next;
-
-               put_uprobe(tmp->uprobe);
-               kfree(tmp);
-       }
+       while (ri)
+               ri = free_ret_instance(ri);
 
        xol_free_insn_slot(t);
        kfree(utask);
@@ -1770,7 +1773,7 @@ handle_uretprobe_chain(struct return_instance *ri, struct pt_regs *regs)
 static bool handle_trampoline(struct pt_regs *regs)
 {
        struct uprobe_task *utask;
-       struct return_instance *ri, *tmp;
+       struct return_instance *ri;
        bool chained;
 
        utask = current->utask;
@@ -1792,11 +1795,7 @@ static bool handle_trampoline(struct pt_regs *regs)
                handle_uretprobe_chain(ri, regs);
 
                chained = ri->chained;
-               put_uprobe(ri->uprobe);
-
-               tmp = ri;
-               ri = ri->next;
-               kfree(tmp);
+               ri = free_ret_instance(ri);
                utask->depth--;
 
                if (!chained)