Commit 13af88f3 authored by Yabin Cui's avatar Yabin Cui Committed by Greg Kroah-Hartman
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coresight: tmc-etr: Fix updating buffer in not-snapshot mode. 



TMC etr always copies all available data to perf aux buffer, which
may exceed the available space in perf aux buffer. It isn't suitable
for not-snapshot mode, because:
1) It may overwrite previously written data.
2) It may make the perf_event_mmap_page->aux_head report having more
or less data than the reality.

So change to only copy the latest data fitting the available space in
perf aux buffer.

Signed-off-by: default avatarYabin Cui <yabinc@google.com>
Signed-off-by: default avatarMathieu Poirier <mathieu.poirier@linaro.org>
Link: https://lore.kernel.org/r/20190829202842.580-14-mathieu.poirier@linaro.org


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 89e89b05

drivers/hwtracing/coresight/coresight-tmc-etr.c

+11 −7
Original line number Diff line number Diff line
@@ -1414,9 +1414,10 @@ free_etr_perf_buffer: 
 * tmc_etr_sync_perf_buffer: Copy the actual trace data from the hardware

 * buffer to the perf ring buffer.

 */

static void tmc_etr_sync_perf_buffer(struct etr_perf_buffer *etr_perf)

static void tmc_etr_sync_perf_buffer(struct etr_perf_buffer *etr_perf,

				     unsigned long to_copy)

{

	long bytes, to_copy;

	long bytes;

	long pg_idx, pg_offset, src_offset;

	unsigned long head = etr_perf->head;

	char **dst_pages, *src_buf;
@@ -1426,8 +1427,7 @@ static void tmc_etr_sync_perf_buffer(struct etr_perf_buffer *etr_perf) 
	pg_idx = head >> PAGE_SHIFT;

	pg_offset = head & (PAGE_SIZE - 1);

	dst_pages = (char **)etr_perf->pages;

	src_offset = etr_buf->offset;

	to_copy = etr_buf->len;

	src_offset = etr_buf->offset + etr_buf->len - to_copy;



	while (to_copy > 0) {

		/*
@@ -1438,6 +1438,8 @@ static void tmc_etr_sync_perf_buffer(struct etr_perf_buffer *etr_perf) 
		 *  3) what is available in the destination page.

		 * in one iteration.

		 */

		if (src_offset >= etr_buf->size)

			src_offset -= etr_buf->size;

		bytes = tmc_etr_buf_get_data(etr_buf, src_offset, to_copy,

					     &src_buf);

		if (WARN_ON_ONCE(bytes <= 0))
@@ -1458,8 +1460,6 @@ static void tmc_etr_sync_perf_buffer(struct etr_perf_buffer *etr_perf) 


		/* Move source pointers */

		src_offset += bytes;

		if (src_offset >= etr_buf->size)

			src_offset -= etr_buf->size;

	}

}
@@ -1505,7 +1505,11 @@ tmc_update_etr_buffer(struct coresight_device *csdev, 
	spin_unlock_irqrestore(&drvdata->spinlock, flags);



	size = etr_buf->len;

	tmc_etr_sync_perf_buffer(etr_perf);

	if (!etr_perf->snapshot && size > handle->size) {

		size = handle->size;

		lost = true;

	}

	tmc_etr_sync_perf_buffer(etr_perf, size);



	/*

	 * In snapshot mode we simply increment the head by the number of byte

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