Re: [PATCH v3 1/3] perf: use hweight64 instead of hweight_long

Arnaldo Carvalho de Melo
2019-04-10T13:10:48Z

Em Wed, Apr 10, 2019 at 10:08:41AM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Wed, Apr 10, 2019 at 04:16:43PM +0800, Mao Han escreveu:
> > On 32-bits platform with more than 32 registers, the 64 bits mask is
> > truncate to the lower 32 bits and the return value of hweight_long will
> > always smaller than 32. When kernel outputs more than 32 registers, but
> > the user perf program only counts 32, there will be a data mismatch
> > result to overflow check fail.
> >
> > CC: Peter Zijlstra <peterz@infradead.org>
> > CC: Ingo Molnar <mingo@redhat.com>
> > CC: Arnaldo Carvalho de Melo <acme@kernel.org>
> > CC: Alexander Shishkin <alexander.shishkin@linux.intel.com>
> > CC: Jiri Olsa <jolsa@redhat.com>
> > CC: Namhyung Kim <namhyung@kernel.org>
> >
> > Signed-off-by: Mao Han <han_mao@c-sky.com>
> > ---
> > tools/perf/util/evsel.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> > index 7835e05..73c78be 100644
> > --- a/tools/perf/util/evsel.c
> > +++ b/tools/perf/util/evsel.c
> > @@ -2322,7 +2322,7 @@ int perf_evsel__parse_sample(struct perf_evsel *evsel, union perf_event *event,
> > if (data->user_regs.abi) {
> > u64 mask = evsel->attr.sample_regs_user;
> >
> > - sz = hweight_long(mask) * sizeof(u64);
> > + sz = hweight64(mask) * sizeof(u64);
> > OVERFLOW_CHECK(array, sz, max_size);
> > data->user_regs.mask = mask;
> > data->user_regs.regs = (u64 *)array;
>
> Later on, in the same function, perf_evsel__parse_sample() we have:
>
> data->intr_regs.abi = PERF_SAMPLE_REGS_ABI_NONE;
> if (type & PERF_SAMPLE_REGS_INTR) {
> OVERFLOW_CHECK_u64(array);
> data->intr_regs.abi = *array;
> array++;
>
> if (data->intr_regs.abi != PERF_SAMPLE_REGS_ABI_NONE) {
> u64 mask = evsel->attr.sample_regs_intr;
>
> sz = hweight_long(mask) * sizeof(u64);
> OVERFLOW_CHECK(array, sz, max_size);
> data->intr_regs.mask = mask;
> data->intr_regs.regs = (u64 *)array;
> array = (void *)array + sz;
> }
> }
>
> You forgot to convert that one, doing it for you,

Also in perf_event__sample_event_size() we need to do the same thing,
right?

- Arnaldo