1 files changed, 110 insertions, 0 deletions
diff --git a/roms/skiboot/external/trace/trace.c b/roms/skiboot/external/trace/trace.c
new file mode 100644
index 000000000..97cec7d9d
--- /dev/null
+++ b/roms/skiboot/external/trace/trace.c
@@ -0,0 +1,110 @@
+// SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
+/*
+ * This example code shows how to read from the trace buffer.
+ *
+ * Copyright 2013-2019 IBM Corp.
+ */
+
+#include <external/trace/trace.h>
+#include "../ccan/endian/endian.h"
+#include "../ccan/short_types/short_types.h"
+#include "trace.h"
+#include <trace_types.h>
+#include <errno.h>
+
+#if defined(__powerpc__) || defined(__powerpc64__)
+#define rmb() lwsync()
+#else
+#define rmb()
+#endif
+
+bool trace_empty(const struct trace_reader *tr)
+{
+	const struct trace_repeat *rep;
+
+	if (tr->rpos == be64_to_cpu(tr->tb->end))
+		return true;
+
+	/*
+	 * If we have a single element only, and it's a repeat buffer
+	 * we've already seen every repeat for (yet which may be
+	 * incremented in future), we're also empty.
+	 */
+	rep = (void *)tr->tb->buf + tr->rpos % be64_to_cpu(tr->tb->buf_size);
+	if (be64_to_cpu(tr->tb->end) != tr->rpos + sizeof(*rep))
+		return false;
+
+	if (rep->type != TRACE_REPEAT)
+		return false;
+
+	if (be16_to_cpu(rep->num) != tr->last_repeat)
+		return false;
+
+	return true;
+}
+
+/* You can't read in parallel, so some locking required in caller. */
+bool trace_get(union trace *t, struct trace_reader *tr)
+{
+	u64 start, rpos;
+	size_t len;
+
+	len = sizeof(*t) < be32_to_cpu(tr->tb->max_size) ? sizeof(*t) :
+		be32_to_cpu(tr->tb->max_size);
+
+	if (trace_empty(tr))
+		return false;
+
+again:
+	/*
+	 * The actual buffer is slightly larger than tbsize, so this
+	 * memcpy is always valid.
+	 */
+	memcpy(t, tr->tb->buf + tr->rpos % be64_to_cpu(tr->tb->buf_size), len);
+
+	rmb(); /* read barrier, so we read tr->tb->start after copying record. */
+
+	start = be64_to_cpu(tr->tb->start);
+	rpos = tr->rpos;
+
+	/* Now, was that overwritten? */
+	if (rpos < start) {
+		/* Create overflow record. */
+		t->overflow.unused64 = 0;
+		t->overflow.type = TRACE_OVERFLOW;
+		t->overflow.len_div_8 = sizeof(t->overflow) / 8;
+		t->overflow.bytes_missed = cpu_to_be64(start - rpos);
+		tr->rpos = start;
+		return true;
+	}
+
+	/* Repeat entries need special handling */
+	if (t->hdr.type == TRACE_REPEAT) {
+		u32 num = be16_to_cpu(t->repeat.num);
+
+		/* In case we've read some already... */
+		t->repeat.num = cpu_to_be16(num - tr->last_repeat);
+
+		/* Record how many repeats we saw this time. */
+		tr->last_repeat = num;
+
+		/* Don't report an empty repeat buffer. */
+		if (t->repeat.num == 0) {
+			/*
+			 * This can't be the last buffer, otherwise
+			 * trace_empty would have returned true.
+			 */
+			assert(be64_to_cpu(tr->tb->end) >
+			       rpos + t->hdr.len_div_8 * 8);
+			/* Skip to next entry. */
+			tr->rpos = rpos + t->hdr.len_div_8 * 8;
+			tr->last_repeat = 0;
+			goto again;
+		}
+	} else {
+		tr->last_repeat = 0;
+		tr->rpos = rpos + t->hdr.len_div_8 * 8;
+	}
+
+	return true;
+}