1 files changed, 38 insertions, 2 deletions

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index c772a3d4000d..02efde6c8798 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -2937,13 +2937,49 @@ void perf_event_do_pending(void)
         __perf_pending_run();
 }
 
+DEFINE_PER_CPU(struct perf_callchain_entry, perf_callchain_entry);
+
 /*
  * Callchain support -- arch specific
  */
 
-__weak struct perf_callchain_entry *perf_callchain(struct pt_regs *regs)
+__weak struct perf_callchain_entry *perf_callchain_buffer(void)
 {
-        return NULL;
+        return &__get_cpu_var(perf_callchain_entry);
+}
+
+__weak void perf_callchain_kernel(struct perf_callchain_entry *entry,
+                                  struct pt_regs *regs)
+{
+}
+
+__weak void perf_callchain_user(struct perf_callchain_entry *entry,
+                                struct pt_regs *regs)
+{
+}
+
+static struct perf_callchain_entry *perf_callchain(struct pt_regs *regs)
+{
+        struct perf_callchain_entry *entry;
+
+        entry = perf_callchain_buffer();
+        if (!entry)
+                return NULL;
+
+        entry->nr = 0;
+
+        if (!user_mode(regs)) {
+                perf_callchain_kernel(entry, regs);
+                if (current->mm)
+                        regs = task_pt_regs(current);
+                else
+                        regs = NULL;
+        }
+
+        if (regs)
+                perf_callchain_user(entry, regs);
+
+        return entry;
 }