@@ -32,6 +32,8 @@ struct cs_etm_recording {
struct auxtrace_record itr;
struct perf_pmu *cs_etm_pmu;
struct perf_evlist *evlist;
+ int wrapped_cnt;
+ bool *wrapped;
bool snapshot_mode;
size_t snapshot_size;
};
@@ -495,16 +497,131 @@ static int cs_etm_info_fill(struct auxtrace_record *itr,
return 0;
}
-static int cs_etm_find_snapshot(struct auxtrace_record *itr __maybe_unused,
+static int cs_etm_alloc_wrapped_array(struct cs_etm_recording *ptr, int idx)
+{
+ bool *wrapped;
+ int cnt = ptr->wrapped_cnt;
+
+ /* Make @ptr->wrapped as big as @idx */
+ while (cnt <= idx)
+ cnt++;
+
+ /*
+ * Free'ed in cs_etm_recording_free(). Using realloc() to avoid
+ * cross compilation problems where the host's system supports
+ * reallocarray() but not the target.
+ */
+ wrapped = realloc(ptr->wrapped, cnt * sizeof(bool));
+ if (!wrapped)
+ return -ENOMEM;
+
+ wrapped[cnt - 1] = false;
+ ptr->wrapped_cnt = cnt;
+ ptr->wrapped = wrapped;
+
+ return 0;
+}
+
+static bool cs_etm_buffer_has_wrapped(unsigned char *buffer,
+ size_t buffer_size, u64 head)
+{
+ u64 i, watermark;
+ u64 *buf = (u64 *)buffer;
+ size_t buf_size = buffer_size;
+
+ /*
+ * We want to look the very last 512 byte (chosen arbitrarily) in
+ * the ring buffer.
+ */
+ watermark = buf_size - 512;
+
+ /*
+ * @head is continuously increasing - if its value is equal or greater
+ * than the size of the ring buffer, it has wrapped around.
+ */
+ if (head >= buffer_size)
+ return true;
+
+ /*
+ * The value of @head is somewhere within the size of the ring buffer.
+ * This can be that there hasn't been enough data to fill the ring
+ * buffer yet or the trace time was so long that @head has numerically
+ * wrapped around. To find we need to check if we have data at the very
+ * end of the ring buffer. We can reliably do this because mmap'ed
+ * pages are zeroed out and there is a fresh mapping with every new
+ * session.
+ */
+
+ /* @head is less than 512 byte from the end of the ring buffer */
+ if (head > watermark)
+ watermark = head;
+
+ /*
+ * Speed things up by using 64 bit transactions (see "u64 *buf" above)
+ */
+ watermark >>= 3;
+ buf_size >>= 3;
+
+ /*
+ * If we find trace data at the end of the ring buffer, @head has
+ * been there and has numerically wrapped around at least once.
+ */
+ for (i = watermark; i < buf_size; i++)
+ if (buf[i])
+ return true;
+
+ return false;
+}
+
+static int cs_etm_find_snapshot(struct auxtrace_record *itr,
int idx, struct auxtrace_mmap *mm,
- unsigned char *data __maybe_unused,
+ unsigned char *data,
u64 *head, u64 *old)
{
+ int err;
+ bool wrapped;
+ struct cs_etm_recording *ptr =
+ container_of(itr, struct cs_etm_recording, itr);
+
+ /*
+ * Allocate memory to keep track of wrapping if this is the first
+ * time we deal with this *mm.
+ */
+ if (idx >= ptr->wrapped_cnt) {
+ err = cs_etm_alloc_wrapped_array(ptr, idx);
+ if (err)
+ return err;
+ }
+
+ /*
+ * Check to see if *head has wrapped around. If it hasn't only the
+ * amount of data between *head and *old is snapshot'ed to avoid
+ * bloating the perf.data file with zeros. But as soon as *head has
+ * wrapped around the entire size of the AUX ring buffer it taken.
+ */
+ wrapped = ptr->wrapped[idx];
+ if (!wrapped && cs_etm_buffer_has_wrapped(data, mm->len, *head)) {
+ wrapped = true;
+ ptr->wrapped[idx] = true;
+ }
+
pr_debug3("%s: mmap index %d old head %zu new head %zu size %zu\n",
__func__, idx, (size_t)*old, (size_t)*head, mm->len);
- *old = *head;
- *head += mm->len;
+ /* No wrap has occurred, we can just use *head and *old. */
+ if (!wrapped)
+ return 0;
+
+ /*
+ * *head has wrapped around - adjust *head and *old to pickup the
+ * entire content of the AUX buffer.
+ */
+ if (*head >= mm->len) {
+ *old = *head - mm->len;
+ } else {
+ *head += mm->len;
+ *old = *head - mm->len;
+ }
return 0;
}
@@ -545,6 +662,8 @@ static void cs_etm_recording_free(struct auxtrace_record *itr)
{
struct cs_etm_recording *ptr =
container_of(itr, struct cs_etm_recording, itr);
+
+ zfree(&ptr->wrapped);
free(ptr);
}