kprobes: kretprobe user entry-handler

Provide support to add an optional user defined callback to be run at
function entry of a kretprobe'd function.  Also modify the kprobe smoke
tests to include an entry-handler during the kretprobe sanity test.

Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com>
Cc: Prasanna S Panchamukhi <prasanna@in.ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Acked-by: Jim Keniston <jkenisto@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 8 insertions, 1 deletions

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index d0493eafea3e..7a86e6432338 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -699,6 +699,12 @@ static int __kprobes pre_handler_kretprobe(struct kprobe *p,
                                  struct kretprobe_instance, uflist);
                 ri->rp = rp;
                 ri->task = current;
+
+                if (rp->entry_handler && rp->entry_handler(ri, regs)) {
+                        spin_unlock_irqrestore(&kretprobe_lock, flags);
+                        return 0;
+                }
+
                 arch_prepare_kretprobe(ri, regs);
 
                 /* XXX(hch): why is there no hlist_move_head? */
@@ -745,7 +751,8 @@ int __kprobes register_kretprobe(struct kretprobe *rp)
         INIT_HLIST_HEAD(&rp->used_instances);
         INIT_HLIST_HEAD(&rp->free_instances);
         for (i = 0; i < rp->maxactive; i++) {
-                inst = kmalloc(sizeof(struct kretprobe_instance), GFP_KERNEL);
+                inst = kmalloc(sizeof(struct kretprobe_instance) +
+                               rp->data_size, GFP_KERNEL);
                 if (inst == NULL) {
                         free_rp_inst(rp);
                         return -ENOMEM;