powerpc/perf: Fix oops when grouping different pmu events

BugLink: http://bugs.launchpad.net/bugs/1746225
When user tries to group imc (In-Memory Collections) event with
normal event, (sometime) kernel crashes with following log:

    Faulting instruction address: 0x00000000
    [link register   ] c00000000010ce88 power_check_constraints+0x128/0x980
    ...
    c00000000010e238 power_pmu_event_init+0x268/0x6f0
    c0000000002dc60c perf_try_init_event+0xdc/0x1a0
    c0000000002dce88 perf_event_alloc+0x7b8/0xac0
    c0000000002e92e0 SyS_perf_event_open+0x530/0xda0
    c00000000000b004 system_call+0x38/0xe0

'event_base' field of 'struct hw_perf_event' is used as flags for
normal hw events and used as memory address for imc events. While
grouping these two types of events, collect_events() tries to
interpret imc 'event_base' as a flag, which causes a corruption
resulting in a crash.

Consider only those events which belongs to 'perf_hw_context' in
collect_events().

Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
Reviewed-By: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
(cherry picked from commit 5aa04b3eb6fca63d2e9827be656dcadc26d54e11)
Signed-off-by: Joseph Salisbury <joseph.salisbury@canonical.com>
Acked-by: Seth Forshee <seth.forshee@canonical.com>
Acked-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
index 6c2d4168daec9a426ff2d9d5fb622fe3338dc836..61140e0f158f291ad52377eadaebe3cca34bfa3c 100644 (file)
--- a/arch/powerpc/perf/core-book3s.c
+++ b/arch/powerpc/perf/core-book3s.c
@@ -1410,7 +1410,7 @@ static int collect_events(struct perf_event *group, int max_count,
        int n = 0;
        struct perf_event *event;
 
-       if (!is_software_event(group)) {
+       if (group->pmu->task_ctx_nr == perf_hw_context) {
                if (n >= max_count)
                        return -1;
                ctrs[n] = group;
@@ -1418,7 +1418,7 @@ static int collect_events(struct perf_event *group, int max_count,
                events[n++] = group->hw.config;
        }
        list_for_each_entry(event, &group->sibling_list, group_entry) {
-               if (!is_software_event(event) &&
+               if (event->pmu->task_ctx_nr == perf_hw_context &&
                    event->state != PERF_EVENT_STATE_OFF) {
                        if (n >= max_count)
                                return -1;