perf_counter: provide generic callchain bits

Provide the generic callchain support bits. If hw_event->callchain is
set the arch specific perf_callchain() function is called upon to
provide a perf_callchain_entry structure filled with the current
callchain.

If it does so, it is added to the overflow output event.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Paul Mackerras <paulus@samba.org>
Orig-LKML-Reference: <20090330171024.254266860@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 27 insertions, 0 deletions

diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index d93e9ddf7848..860cdc26bd7a 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -1654,6 +1654,17 @@ void perf_counter_do_pending(void)
 }
 
 /*
+ * Callchain support -- arch specific
+ */
+
+struct perf_callchain_entry *
+__attribute__((weak))
+perf_callchain(struct pt_regs *regs)
+{
+        return NULL;
+}
+
+/*
  * Output
  */
 
@@ -1764,6 +1775,8 @@ static void perf_output_simple(struct perf_counter *counter,
         struct {
                 u32 pid, tid;
         } tid_entry;
+        struct perf_callchain_entry *callchain = NULL;
+        int callchain_size = 0;
 
         header.type = PERF_EVENT_OVERFLOW;
         header.size = sizeof(header);
@@ -1781,6 +1794,17 @@ static void perf_output_simple(struct perf_counter *counter,
                 header.size += sizeof(tid_entry);
         }
 
+        if (counter->hw_event.callchain) {
+                callchain = perf_callchain(regs);
+
+                if (callchain) {
+                        callchain_size = (1 + callchain->nr) * sizeof(u64);
+
+                        header.type |= __PERF_EVENT_CALLCHAIN;
+                        header.size += callchain_size;
+                }
+        }
+
         ret = perf_output_begin(&handle, counter, header.size, nmi);
         if (ret)
                 return;
@@ -1791,6 +1815,9 @@ static void perf_output_simple(struct perf_counter *counter,
         if (counter->hw_event.include_tid)
                 perf_output_put(&handle, tid_entry);
 
+        if (callchain)
+                perf_output_copy(&handle, callchain, callchain_size);
+
         perf_output_end(&handle);
 }