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>

diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index edf5bfb7ff5158972d20e0d527edb5374e6857a8..43083afffe0fb24f0984bf043bcaa261e1282f9c 100644 (file)
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -140,8 +140,9 @@ struct perf_counter_hw_event {
                                include_tid    :  1, /* include the tid       */
                                mmap           :  1, /* include mmap data     */
                                munmap         :  1, /* include munmap data   */
+                               callchain      :  1, /* add callchain data    */
 
-                               __reserved_1   : 52;
+                               __reserved_1   : 51;
 
        __u32                   extra_config_len;
        __u32                   __reserved_4;
@@ -219,6 +220,7 @@ enum perf_event_type {
        PERF_EVENT_OVERFLOW     = 1UL << 31,
        __PERF_EVENT_IP         = 1UL << 30,
        __PERF_EVENT_TID        = 1UL << 29,
+       __PERF_EVENT_CALLCHAIN  = 1UL << 28,
 };
 
 #ifdef __KERNEL__
@@ -504,6 +506,15 @@ extern void perf_counter_mmap(unsigned long addr, unsigned long len,
 extern void perf_counter_munmap(unsigned long addr, unsigned long len,
                                unsigned long pgoff, struct file *file);
 
+#define MAX_STACK_DEPTH                255
+
+struct perf_callchain_entry {
+       u64     nr;
+       u64     ip[MAX_STACK_DEPTH];
+};
+
+extern struct perf_callchain_entry *perf_callchain(struct pt_regs *regs);
+
 #else
 static inline void
 perf_counter_task_sched_in(struct task_struct *task, int cpu)          { }

diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index d93e9ddf78484c3f00f6628ce81fe15f1e10417c..860cdc26bd7a864eb7705589efd3e05629780a65 100644 (file)
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -1653,6 +1653,17 @@ void perf_counter_do_pending(void)
        __perf_pending_run();
 }
 
+/*
+ * 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);
 }