Messages in this thread Patch in this message | | | Date | Fri, 11 Oct 2019 14:16:06 -0600 | From | Mathieu Poirier <> | Subject | Re: [PATCH v3 1/6] perf cs-etm: Fix unsigned variable comparison to zero |
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On Sat, Oct 05, 2019 at 05:16:09PM +0800, Leo Yan wrote: > If the u64 variable 'offset' is a negative integer, comparison it with > bigger than zero is always going to be true because it is unsigned. > Fix this by using s64 type for variable 'offset'. > > Signed-off-by: Leo Yan <leo.yan@linaro.org> > --- > tools/perf/util/cs-etm.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c > index 4ba0f871f086..4bc2d9709d4f 100644 > --- a/tools/perf/util/cs-etm.c > +++ b/tools/perf/util/cs-etm.c > @@ -940,7 +940,7 @@ u64 cs_etm__last_executed_instr(const struct cs_etm_packet *packet) > static inline u64 cs_etm__instr_addr(struct cs_etm_queue *etmq, > u64 trace_chan_id, > const struct cs_etm_packet *packet, > - u64 offset) > + s64 offset)
In Suzuki's reply there was two choices, 1) move the while(offset > 0) to while (offset) or change the type of @offset to an s64. Here we know offset can't be negative because of the tidq->period_instructions >= etm->instructions_sample_period
in function cs_etm__sample(). As such I think option #1 is the right way to deal with this rather than changing the type of the variable.
Mathieu
> { > if (packet->isa == CS_ETM_ISA_T32) { > u64 addr = packet->start_addr; > @@ -1372,7 +1372,7 @@ static int cs_etm__sample(struct cs_etm_queue *etmq, > * sample is reported as though instruction has just been > * executed, but PC has not advanced to next instruction) > */ > - u64 offset = (instrs_executed - instrs_over - 1); > + s64 offset = (instrs_executed - instrs_over - 1); > u64 addr = cs_etm__instr_addr(etmq, trace_chan_id, > tidq->packet, offset); > > -- > 2.17.1 >
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