Re: [PATCH v3 1/6] perf cs-etm: Fix unsigned variable comparison to zero
From: Mathieu Poirier <mathieu.poirier@linaro.org>
Date: 2019-10-11 20:16:11
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On Sat, Oct 05, 2019 at 05:16:09PM +0800, Leo Yan wrote:
quoted hunk ↗ jump to hunk
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 <redacted> --- 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
quoted hunk ↗ jump to hunk
{ 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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