otp: convert to use weak default

There is no longer any point in having CFG_OTP_SUPPORT.

It's always supported either by the weak implementation
or any platform override.

Since there exists a platform 'sunxi' that does not have
CFG_GENERIC_BOOT and doesn't build generic_boot.c, this
is plaved in a new file 'otp_stubs.c'.  Since this is
just copied Linaro code at this point, keep Linaro
copyright message on the new file.

Signed-off-by: Andy Green <andy@warmcat.com>

core/arch/arm/kernel/otp_stubs.c

@@ -0,0 +1,52 @@
+/*
+ * Copyright (c) 2015, Linaro Limited
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ * this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ * this list of conditions and the following disclaimer in the documentation
+ * and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <inttypes.h>
+#include <kernel/tee_common_otp.h>
+
+/*
+ * Override these in your platform code to really fetch device-unique
+ * bits from e-fuses or whatever.
+ *
+ * The default implementation just sets it to a constant.
+ */
+
+__weak void tee_otp_get_hw_unique_key(struct tee_hw_unique_key *hwkey)
+{
+	memset(&hwkey->data[0], 0, sizeof(hwkey->data));
+}
+
+__weak int tee_otp_get_die_id(uint8_t *buffer, size_t len)
+{
+	static const char pattern[4] = { 'B', 'E', 'E', 'F' };
+	size_t i;
+
+	for (i = 0; i < len; i++)
+		buffer[i] = pattern[i % 4];
+
+	return 0;
+}

core/arch/arm/kernel/sub.mk

@@ -2,6 +2,7 @@ srcs-$(CFG_WITH_USER_TA) += user_ta.c
 srcs-y += static_ta.c
 srcs-y += elf_load.c
 srcs-y += tee_time.c
+srcs-y += otp_stubs.c
 
 srcs-$(CFG_SECURE_TIME_SOURCE_CNTPCT) += tee_time_arm_cntpct.c
 srcs-$(CFG_SECURE_TIME_SOURCE_REE) += tee_time_ree.c

core/include/kernel/tee_common_otp.h

@@ -36,29 +36,7 @@ struct tee_hw_unique_key {
 	uint8_t data[HW_UNIQUE_KEY_LENGTH];
 };
 
-#if defined(CFG_OTP_SUPPORT)
-
 void tee_otp_get_hw_unique_key(struct tee_hw_unique_key *hwkey);
 int tee_otp_get_die_id(uint8_t *buffer, size_t len);
 
-#else
-
-static inline void tee_otp_get_hw_unique_key(struct tee_hw_unique_key *hwkey)
-{
-	memset(&hwkey->data[0], 0, sizeof(hwkey->data));
-}
-
-static inline int tee_otp_get_die_id(uint8_t *buffer, size_t len)
-{
-	size_t i;
-
-	char pattern[4] = { 'B', 'E', 'E', 'F' };
-	for (i = 0; i < len; i++)
-		buffer[i] = pattern[i % 4];
-
-	return 0;
-}
-
-#endif /* !defined(CFG_OTP_SUPPORT) */
-
 #endif /* TEE_COMMON_OTP_H */

documentation/secure_storage.md

@@ -228,11 +228,8 @@ considered sensitive by the vendors and it is not freely available.
 In OP-TEE, there are apis for reading the keys generically from "One-Time
 Programmable" memory, or OTP.  But there are no existing platform implementations.
 
-To allow Secure Storage to operate securely on your platform, you must:
-
- - enable CFG_OTP_SUPPORT on your platform
-
- - In your platform code, define implementations for:
+To allow Secure Storage to operate securely on your platform, you must define
+implementations in your platform code for:
 
 ```
  void tee_otp_get_hw_unique_key(struct tee_hw_unique_key *hwkey);