From: rasky <rasky@38d2e660-2303-0410-9eaa-f027e97ec537>
Date: Tue, 28 Sep 2010 18:35:35 +0000 (+0000)
Subject: SEC: Add LM3S backend for entropy pulling.
X-Git-Tag: 2.6.0~63
X-Git-Url: https://codewiz.org/gitweb?a=commitdiff_plain;h=239b0b70c59b7242e0ff604b7f8b87a37f83de56;p=bertos.git

SEC: Add LM3S backend for entropy pulling.


git-svn-id: https://src.develer.com/svnoss/bertos/trunk@4338 38d2e660-2303-0410-9eaa-f027e97ec537
---

diff --git a/bertos/sec/random_lm3s.c b/bertos/sec/random_lm3s.c
new file mode 100644
index 00000000..0adc96ce
--- /dev/null
+++ b/bertos/sec/random_lm3s.c
@@ -0,0 +1,89 @@
+/**
+ * \file
+ * <!--
+ * This file is part of BeRTOS.
+ *
+ * Bertos is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * 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.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ * As a special exception, you may use this file as part of a free software
+ * library without restriction.  Specifically, if other files instantiate
+ * templates or use macros or inline functions from this file, or you compile
+ * this file and link it with other files to produce an executable, this
+ * file does not by itself cause the resulting executable to be covered by
+ * the GNU General Public License.  This exception does not however
+ * invalidate any other reasons why the executable file might be covered by
+ * the GNU General Public License.
+ *
+ * Copyright 2010 Develer S.r.l. (http://www.develer.com/)
+ *
+ * -->
+ *
+ * \brief LM3 backend implementation entropy pulling.
+ * \author Giovanni Bajo <rasky@develer.com>
+ *
+ */
+
+#include "random_p.h"
+#include <io/cm3.h>
+#include <drv/clock_lm3s.h>
+
+/*
+ * Return the cpu core temperature in raw format
+ */
+INLINE uint16_t hw_readRawTemp(void)
+{
+    /* Trig the temperature sampling */
+    HWREG(ADC0_BASE + ADC_O_PSSI) |= ADC_PSSI_SS3;
+
+	while (!(HWREG(ADC0_BASE + ADC_O_SSFSTAT3) & ADC_SSFSTAT3_FULL));
+
+    return (uint16_t)HWREG(ADC0_BASE + ADC_O_SSFIFO3);
+}
+
+INLINE void hw_initIntTemp(void)
+{
+    SYSCTL_RCGC0_R |= SYSCTL_RCGC0_ADC0;
+
+	lm3s_busyWait(10);
+
+    /* Disable all sequence */
+    HWREG(ADC0_BASE + ADC_O_ACTSS) = 0;
+    /* Set trigger event to programmed (for all sequence) */
+    HWREG(ADC0_BASE + ADC_O_EMUX) = 0;
+    /* Enalbe read of temperature sensor */
+    HWREG(ADC0_BASE + ADC_O_SSCTL3) |= ADC_SSCTL3_TS0;
+    /* Enable sequence S03 (single sample on select channel) */
+    HWREG(ADC0_BASE + ADC_O_ACTSS) |= ADC_ACTSS_ASEN3;
+}
+
+
+void random_pull_entropy(uint8_t *entropy, size_t len)
+{
+	// We use the internal temperature sensor of LM3S as a source of entropy.
+	// The last bit of the acquisition is very variable and with a decent distribution
+	// to consider it "entropic". It does not really matter because it will
+	// go through a randomness extractor anyway.
+	hw_initIntTemp();
+	
+	for (size_t j=0; j<len; j++)
+	{
+		uint8_t accum = 0;
+		for (int b=0; b<8; ++b)
+			if (hw_readRawTemp() & 1)
+				accum |= 1<<b;
+		
+		*entropy++ = accum;
+	}
+}