On Tue, Jan 26, 2021 at 10:33:18AM -0500, Liang, Kan wrote:
>
>
> On 1/26/2021 9:42 AM, Peter Zijlstra wrote:
> > On Tue, Jan 19, 2021 at 12:38:20PM -0800, kan.li...@linux.intel.com wrote:
> >
> > > @@ -900,6 +901,13 @@ enum perf_event_type {
> > > * char data[size]; } && PERF_SAMPLE_AUX
> > > * { u64 data_page_size;} &&
> > > PERF_SAMPLE_DATA_PAGE_SIZE
> > > * { u64 code_page_size;} &&
> > > PERF_SAMPLE_CODE_PAGE_SIZE
> > > + * { union {
> > > + * u64 weight_ext;
> > > + * struct {
> > > + * u64 instr_latency:16,
> > > + * reserved:48;
> > > + * };
> > > + * } && PERF_SAMPLE_WEIGHT_EXT
> > > * };
> > > */
> > > PERF_RECORD_SAMPLE = 9,
> > > @@ -1248,4 +1256,12 @@ struct perf_branch_entry {
> > > reserved:40;
> > > };
> > > +union perf_weight_ext {
> > > + __u64 val;
> > > + struct {
> > > + __u64 instr_latency:16,
> > > + reserved:48;
> > > + };
> > > +};
> > > +
> > > #endif /* _UAPI_LINUX_PERF_EVENT_H */
> > > diff --git a/kernel/events/core.c b/kernel/events/core.c
> > > index 55d1879..9363d12 100644
> > > --- a/kernel/events/core.c
> > > +++ b/kernel/events/core.c
> > > @@ -1903,6 +1903,9 @@ static void __perf_event_header_size(struct
> > > perf_event *event, u64 sample_type)
> > > if (sample_type & PERF_SAMPLE_CODE_PAGE_SIZE)
> > > size += sizeof(data->code_page_size);
> > > + if (sample_type & PERF_SAMPLE_WEIGHT_EXT)
> > > + size += sizeof(data->weight_ext);
> > > +
> > > event->header_size = size;
> > > }
> > > @@ -6952,6 +6955,9 @@ void perf_output_sample(struct perf_output_handle
> > > *handle,
> > > perf_aux_sample_output(event, handle, data);
> > > }
> > > + if (sample_type & PERF_SAMPLE_WEIGHT_EXT)
> > > + perf_output_put(handle, data->weight_ext);
> > > +
> > > if (!event->attr.watermark) {
> > > int wakeup_events = event->attr.wakeup_events;
> >
> > This patch is broken and will expose uninitialized kernel stack.
> >
>
> Could we initialize the 'weight_ext' in perf_sample_data_init()?
No. Also see my other mail for why I hate this thing.
