1 files changed, 101 insertions, 2 deletions

diff --git a/arch/ia64/kernel/kprobes.c b/arch/ia64/kernel/kprobes.c
index 5978823d5c63..c97e18e634ca 100644
--- a/arch/ia64/kernel/kprobes.c
+++ b/arch/ia64/kernel/kprobes.c
@@ -290,6 +290,94 @@ static inline void set_current_kprobe(struct kprobe *p)
         current_kprobe = p;
 }
 
+static void kretprobe_trampoline(void)
+{
+}
+
+/*
+ * At this point the target function has been tricked into
+ * returning into our trampoline.  Lookup the associated instance
+ * and then:
+ *    - call the handler function
+ *    - cleanup by marking the instance as unused
+ *    - long jump back to the original return address
+ */
+int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
+{
+        struct kretprobe_instance *ri = NULL;
+        struct hlist_head *head;
+        struct hlist_node *node, *tmp;
+        unsigned long orig_ret_address = 0;
+        unsigned long trampoline_address =
+                ((struct fnptr *)kretprobe_trampoline)->ip;
+
+        head = kretprobe_inst_table_head(current);
+
+        /*
+         * It is possible to have multiple instances associated with a given
+         * task either because an multiple functions in the call path
+         * have a return probe installed on them, and/or more then one return
+         * return probe was registered for a target function.
+         *
+         * We can handle this because:
+         *     - instances are always inserted at the head of the list
+         *     - when multiple return probes are registered for the same
+         *       function, the first instance's ret_addr will point to the
+         *       real return address, and all the rest will point to
+         *       kretprobe_trampoline
+         */
+        hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
+                if (ri->task != current)
+                        /* another task is sharing our hash bucket */
+                        continue;
+
+                if (ri->rp && ri->rp->handler)
+                        ri->rp->handler(ri, regs);
+
+                orig_ret_address = (unsigned long)ri->ret_addr;
+                recycle_rp_inst(ri);
+
+                if (orig_ret_address != trampoline_address)
+                        /*
+                         * This is the real return address. Any other
+                         * instances associated with this task are for
+                         * other calls deeper on the call stack
+                         */
+                        break;
+        }
+
+        BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address));
+        regs->cr_iip = orig_ret_address;
+
+        unlock_kprobes();
+        preempt_enable_no_resched();
+
+        /*
+         * By returning a non-zero value, we are telling
+         * kprobe_handler() that we have handled unlocking
+         * and re-enabling preemption.
+         */
+        return 1;
+}
+
+void arch_prepare_kretprobe(struct kretprobe *rp, struct pt_regs *regs)
+{
+        struct kretprobe_instance *ri;
+
+        if ((ri = get_free_rp_inst(rp)) != NULL) {
+                ri->rp = rp;
+                ri->task = current;
+                ri->ret_addr = (kprobe_opcode_t *)regs->b0;
+
+                /* Replace the return addr with trampoline addr */
+                regs->b0 = ((struct fnptr *)kretprobe_trampoline)->ip;
+
+                add_rp_inst(ri);
+        } else {
+                rp->nmissed++;
+        }
+}
+
 int arch_prepare_kprobe(struct kprobe *p)
 {
         unsigned long addr = (unsigned long) p->addr;
@@ -492,8 +580,8 @@ static int pre_kprobes_handler(struct die_args *args)
         if (p->pre_handler && p->pre_handler(p, regs))
                 /*
                  * Our pre-handler is specifically requesting that we just
-                 * do a return.  This is handling the case where the
-                 * pre-handler is really our special jprobe pre-handler.
+                 * do a return.  This is used for both the jprobe pre-handler
+                 * and the kretprobe trampoline
                  */
                 return 1;
 
@@ -599,3 +687,14 @@ int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
         *regs = jprobe_saved_regs;
         return 1;
 }
+
+static struct kprobe trampoline_p = {
+        .pre_handler = trampoline_probe_handler
+};
+
+int __init arch_init(void)
+{
+        trampoline_p.addr =
+                (kprobe_opcode_t *)((struct fnptr *)kretprobe_trampoline)->ip;
+        return register_kprobe(&trampoline_p);
+}