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perf cs-etm: Avoid truncating AUX buffer sizes to int

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cs_etm__get_trace() returns an int, but it used to return etmq->buf_len
on success. That value comes from auxtrace_buffer::size, which is a
size_t. For a large AUX trace block, returning the byte count through an
int can overflow and make a valid buffer look like a negative error.

The callers do not need the actual byte count from cs_etm__get_trace().
The buffer length is already stored in the etmq->buf_len. The callers
only need to distinguish three states:

  < 0: error
  = 0: no more AUX buffers
  > 0: data is available

Make cs_etm__get_trace() return 0 for all non-error cases and use
etmq->buf_len to indicate whether a new buffer was found. Then make
cs_etm__get_data_block() return 1 whenever data is available, instead of
returning the buffer length.

Also refactor cs_etm__get_data_block() to make its return value
semantics clearer.

Reported-by: Suyash Mahar <smahar@meta.com>
Fixes: 8224531cf5 ("perf cs-etm: Modularize auxtrace_buffer fetch function")
Signed-off-by: Leo Yan <leo.yan@arm.com>
Reviewed-by: James Clark <james.clark@linaro.org>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
This commit is contained in:
Leo Yan
2026-07-22 22:42:25 -07:00
committed by Namhyung Kim
parent 64724095a3
commit ec99be8a31
1 changed files with 26 additions and 20 deletions
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tools/perf/util/cs-etm.c
+26 -20
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@@ -1467,8 +1467,7 @@ cs_etm__get_trace(struct cs_etm_queue *etmq)
etmq->buf_used = 0;
etmq->buf_len = aux_buffer->size;
etmq->buf = aux_buffer->data;
return etmq->buf_len;
return 0;
}
/*
@@ -2151,26 +2150,33 @@ static int cs_etm__get_data_block(struct cs_etm_queue *etmq)
{
int ret;
if (!etmq->buf_len) {
ret = cs_etm__get_trace(etmq);
if (ret <= 0)
return ret;
/*
* We cannot assume consecutive blocks in the data file
* are contiguous, reset the decoder to force re-sync.
*/
ret = cs_etm_decoder__reset(etmq->decoder);
if (ret)
return ret;
/* The current block is not finished */
if (etmq->buf_len)
return 1;
/*
* Since the decoder is reset, this causes a global trace
* discontinuity. Flush all thread stacks.
*/
cs_etm__flush_all_stack(etmq);
}
ret = cs_etm__get_trace(etmq);
if (ret < 0)
return ret;
return etmq->buf_len;
/* No more buffer to read */
if (!etmq->buf_len)
return 0;
/*
* We cannot assume consecutive blocks in the data file
* are contiguous, reset the decoder to force re-sync.
*/
ret = cs_etm_decoder__reset(etmq->decoder);
if (ret)
return ret;
/*
* Since the decoder is reset, this causes a global trace
* discontinuity. Flush all thread stacks.
*/
cs_etm__flush_all_stack(etmq);
return 1;
}
static bool cs_etm__is_svc_instr(struct cs_etm_queue *etmq,