1 files changed, 108 insertions, 0 deletions
diff --git a/drivers/firmware/google/vpd_decode.c b/drivers/firmware/google/vpd_decode.c
new file mode 100644
index 000000000..6c7ab2ba8
--- /dev/null
+++ b/drivers/firmware/google/vpd_decode.c
@@ -0,0 +1,108 @@
+/*
+ * vpd_decode.c
+ *
+ * Google VPD decoding routines.
+ *
+ * Copyright 2017 Google Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License v2.0 as published by
+ * the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/export.h>
+
+#include "vpd_decode.h"
+
+static int vpd_decode_len(const u32 max_len, const u8 *in,
+			  u32 *length, u32 *decoded_len)
+{
+	u8 more;
+	int i = 0;
+
+	if (!length || !decoded_len)
+		return VPD_FAIL;
+
+	*length = 0;
+	do {
+		if (i >= max_len)
+			return VPD_FAIL;
+
+		more = in[i] & 0x80;
+		*length <<= 7;
+		*length |= in[i] & 0x7f;
+		++i;
+	} while (more);
+
+	*decoded_len = i;
+	return VPD_OK;
+}
+
+static int vpd_decode_entry(const u32 max_len, const u8 *input_buf,
+			    u32 *_consumed, const u8 **entry, u32 *entry_len)
+{
+	u32 decoded_len;
+	u32 consumed = *_consumed;
+
+	if (vpd_decode_len(max_len - consumed, &input_buf[consumed],
+			   entry_len, &decoded_len) != VPD_OK)
+		return VPD_FAIL;
+	if (max_len - consumed < decoded_len)
+		return VPD_FAIL;
+
+	consumed += decoded_len;
+	*entry = input_buf + consumed;
+
+	/* entry_len is untrusted data and must be checked again. */
+	if (max_len - consumed < *entry_len)
+		return VPD_FAIL;
+
+	consumed += *entry_len;
+	*_consumed = consumed;
+	return VPD_OK;
+}
+
+int vpd_decode_string(const u32 max_len, const u8 *input_buf, u32 *consumed,
+		      vpd_decode_callback callback, void *callback_arg)
+{
+	int type;
+	u32 key_len;
+	u32 value_len;
+	const u8 *key;
+	const u8 *value;
+
+	/* type */
+	if (*consumed >= max_len)
+		return VPD_FAIL;
+
+	type = input_buf[*consumed];
+
+	switch (type) {
+	case VPD_TYPE_INFO:
+	case VPD_TYPE_STRING:
+		(*consumed)++;
+
+		if (vpd_decode_entry(max_len, input_buf, consumed, &key,
+				     &key_len) != VPD_OK)
+			return VPD_FAIL;
+
+		if (vpd_decode_entry(max_len, input_buf, consumed, &value,
+				     &value_len) != VPD_OK)
+			return VPD_FAIL;
+
+		if (type == VPD_TYPE_STRING)
+			return callback(key, key_len, value, value_len,
+					callback_arg);
+		break;
+
+	default:
+		return VPD_FAIL;
+	}
+
+	return VPD_OK;
+}