Provide interface to random number generator

It needs to be possible to retrieve an arbitrary number of random
bytes, which is accomplished by this _cpri__GenerateRandom()
implementation.

Also, this patch rearranges the board initialization code to
initialize both interrupts and the TRNG.

CL-DEPEND=CL:306781
BRANCH=none
BUG=chrome-os-partner:43025
TEST=ran a couple of tests retrieving random numbers from TPM,
     observed randomly looking values generated (this is not a
     validation of the TRNG implementation).

Change-Id: I6314cdf5e6e96443b3fadb7f1502fc8477c41d0f
Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/306780
Reviewed-by: Bill Richardson <wfrichar@chromium.org>

3 files changed, 50 insertions, 8 deletions

diff --git a/board/cr50/board.c b/board/cr50/board.c
index 36b4fea164..8dee558cca 100644
--- a/board/cr50/board.c
+++ b/board/cr50/board.c
@@ -10,6 +10,7 @@
 #include "hooks.h"
 #include "registers.h"
 #include "task.h"
+#include "trng.h"
 #include "usb.h"
 #include "usb_hid.h"
 #include "util.h"
@@ -64,18 +65,25 @@ void button_event(enum gpio_signal signal)
 	gpio_set_level(signal - GPIO_SW_N + GPIO_LED_4, v);
 }
 
+static void init_interrutps(void)
+{
+	int i;
+	static const enum gpio_signal gpio_signals[] = {
+		GPIO_SW_N, GPIO_SW_S, GPIO_SW_W, GPIO_SW_E,
+		GPIO_SW_N_, GPIO_SW_S_, GPIO_SW_W_, GPIO_SW_E_
+	};
+
+	for (i = 0; i < ARRAY_SIZE(gpio_signals); i++)
+		gpio_enable_interrupt(gpio_signals[i]);
+}
+
 /* Initialize board. */
 static void board_init(void)
 {
-	gpio_enable_interrupt(GPIO_SW_N);
-	gpio_enable_interrupt(GPIO_SW_S);
-	gpio_enable_interrupt(GPIO_SW_W);
-	gpio_enable_interrupt(GPIO_SW_E);
-	gpio_enable_interrupt(GPIO_SW_N_);
-	gpio_enable_interrupt(GPIO_SW_S_);
-	gpio_enable_interrupt(GPIO_SW_W_);
-	gpio_enable_interrupt(GPIO_SW_E_);
+	init_interrutps();
+	init_trng();
 }
+
 DECLARE_HOOK(HOOK_INIT, board_init, HOOK_PRIO_DEFAULT);
 
 #if defined(CONFIG_USB)
diff --git a/board/cr50/build.mk b/board/cr50/build.mk
index 0b3f80c96d..61fc79e903 100644
--- a/board/cr50/build.mk
+++ b/board/cr50/build.mk
@@ -27,6 +27,7 @@ dirs-y += $(BDIR)/tpm2
 
 # Objects that we need to build
 board-y =  board.o
+board-y += tpm2/platform.o
 board-y += tpm2/NVMem.o
 
 # Build and link with an external library
diff --git a/board/cr50/tpm2/platform.c b/board/cr50/tpm2/platform.c
new file mode 100644
index 0000000000..afe5c86c74
--- /dev/null
+++ b/board/cr50/tpm2/platform.c
@@ -0,0 +1,33 @@
+/* Copyright 2015 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "Platform.h"
+#include "TPM_Types.h"
+
+#include "trng.h"
+
+UINT16 _cpri__GenerateRandom(INT32 randomSize,
+			     BYTE *buffer)
+{
+	int random_togo = 0;
+	int buffer_index = 0;
+	uint32_t random_value;
+
+	/*
+	 * Retrieve random numbers in 4 byte quantities and pack as many bytes
+	 * as needed into 'buffer'. If randomSize is not divisible by 4, the
+	 * remaining random bytes get dropped.
+	 */
+	while (buffer_index < randomSize) {
+		if (!random_togo) {
+			random_value = rand();
+			random_togo = sizeof(random_value);
+		}
+		buffer[buffer_index++] = random_value >>
+			((random_togo-- - 1) * 8);
+	}
+
+	return randomSize;
+}