On Thursday 30 November 2017 02:03 PM, Ravi Bangoria wrote:
> 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().
Reviewed-By: Madhavan Srinivasan <[email protected]>
>
> Signed-off-by: Ravi Bangoria <[email protected]>
> ---
> arch/powerpc/perf/core-book3s.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
> index 9e3da16..1538129 100644
> --- a/arch/powerpc/perf/core-book3s.c
> +++ b/arch/powerpc/perf/core-book3s.c
> @@ -1415,7 +1415,7 @@ 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;
> @@ -1423,7 +1423,7 @@ 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;