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

Arnaldo Carvalho de Melo
2019-04-10T13:28:45Z

Em Wed, Apr 10, 2019 at 10:10:42AM -0300, Arnaldo Carvalho de Melo escreveu:
> 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?

and perf_event__synthesize_sample()

Done, resulting patch is at the end of this messages, and matches the
kernel, that uses only hweight64().

I've also added Fixes tags to the patches that used hweight_long() in
various places, to help with the stable trees backporting process,
please consider doing it next time.

- Arnaldo

commit 21e6dfe04861c2c1b529f2759850bc62a80ca050
Author: Mao Han <han_mao@c-sky.com>
Date: Wed Apr 10 16:16:43 2019 +0800

perf evsel: Use hweight64() instead of hweight_long(attr.sample_regs_user)

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.

Signed-off-by: Mao Han <han_mao@c-sky.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Fixes: 6a21c0b5c2ab ("perf tools: Add core support for sampling intr machine state regs")
Fixes: d03f2170546d ("perf tools: Expand perf_event__synthesize_sample()")
Fixes: 0f6a30150ca2 ("perf tools: Support user regs and stack in sample parsing")
Link: http://lkml.kernel.org/r/29ad7947dc8fd1ff0abd2093a72cc27a2446be9f.1554883878.git.han_mao@c-sky.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 66d066f18b5b..966360844fff 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -2368,7 +2368,7 @@ 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;
@@ -2424,7 +2424,7 @@ int perf_evsel__parse_sample(struct perf_evsel *evsel, union perf_event *event,
if (data->intr_regs.abi != PERF_SAMPLE_REGS_ABI_NONE) {
u64 mask = evsel->attr.sample_regs_intr;

- sz = hweight_long(mask) * sizeof(u64);
+ sz = hweight64(mask) * sizeof(u64);
OVERFLOW_CHECK(array, sz, max_size);
data->intr_regs.mask = mask;
data->intr_regs.regs = (u64 *)array;
@@ -2552,7 +2552,7 @@ size_t perf_event__sample_event_size(const struct perf_sample *sample, u64 type,
if (type & PERF_SAMPLE_REGS_USER) {
if (sample->user_regs.abi) {
result += sizeof(u64);
- sz = hweight_long(sample->user_regs.mask) * sizeof(u64);
+ sz = hweight64(sample->user_regs.mask) * sizeof(u64);
result += sz;
} else {
result += sizeof(u64);
@@ -2580,7 +2580,7 @@ size_t perf_event__sample_event_size(const struct perf_sample *sample, u64 type,
if (type & PERF_SAMPLE_REGS_INTR) {
if (sample->intr_regs.abi) {
result += sizeof(u64);
- sz = hweight_long(sample->intr_regs.mask) * sizeof(u64);
+ sz = hweight64(sample->intr_regs.mask) * sizeof(u64);
result += sz;
} else {
result += sizeof(u64);
@@ -2710,7 +2710,7 @@ int perf_event__synthesize_sample(union perf_event *event, u64 type,
if (type & PERF_SAMPLE_REGS_USER) {
if (sample->user_regs.abi) {
*array++ = sample->user_regs.abi;
- sz = hweight_long(sample->user_regs.mask) * sizeof(u64);
+ sz = hweight64(sample->user_regs.mask) * sizeof(u64);
memcpy(array, sample->user_regs.regs, sz);
array = (void *)array + sz;
} else {
@@ -2746,7 +2746,7 @@ int perf_event__synthesize_sample(union perf_event *event, u64 type,
if (type & PERF_SAMPLE_REGS_INTR) {
if (sample->intr_regs.abi) {
*array++ = sample->intr_regs.abi;
- sz = hweight_long(sample->intr_regs.mask) * sizeof(u64);
+ sz = hweight64(sample->intr_regs.mask) * sizeof(u64);
memcpy(array, sample->intr_regs.regs, sz);
array = (void *)array + sz;
} else {