--- /dev/null
+/*
+ * Copyright (C) 2012 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program 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 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 Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+/** @file
+ *
+ * RTC-based entropy source
+ *
+ */
+
+#include <stdint.h>
+#include <string.h>
+#include <biosint.h>
+#include <pic8259.h>
+#include <rtc.h>
+#include <ipxe/entropy.h>
+
+/** RTC "interrupt triggered" flag */
+static uint8_t __text16 ( rtc_flag );
+#define rtc_flag __use_text16 ( rtc_flag )
+
+/** RTC interrupt handler */
+extern void rtc_isr ( void );
+
+/** Previous RTC interrupt handler */
+static struct segoff rtc_old_handler;
+
+/**
+ * Hook RTC interrupt handler
+ *
+ */
+static void rtc_hook_isr ( void ) {
+
+ /* RTC interrupt handler */
+ __asm__ __volatile__ (
+ TEXT16_CODE ( "\nrtc_isr:\n\t"
+ /* Preserve registers */
+ "pushw %%ax\n\t"
+ /* Set "interrupt triggered" flag */
+ "cs movb $0x01, %c0\n\t"
+ /* Read RTC status register C to
+ * acknowledge interrupt
+ */
+ "movb %3, %%al\n\t"
+ "outb %%al, %1\n\t"
+ "inb %2\n\t"
+ /* Send EOI */
+ "movb $0x20, %%al\n\t"
+ "outb %%al, $0xa0\n\t"
+ "outb %%al, $0x20\n\t"
+ /* Restore registers and return */
+ "popw %%ax\n\t"
+ "iret\n\t" )
+ :
+ : "p" ( __from_text16 ( &rtc_flag ) ),
+ "i" ( CMOS_ADDRESS ), "i" ( CMOS_DATA ),
+ "i" ( RTC_STATUS_C ) );
+
+ hook_bios_interrupt ( RTC_INT, ( unsigned int ) rtc_isr,
+ &rtc_old_handler );
+}
+
+/**
+ * Unhook RTC interrupt handler
+ *
+ */
+static void rtc_unhook_isr ( void ) {
+ int rc;
+
+ rc = unhook_bios_interrupt ( RTC_INT, ( unsigned int ) rtc_isr,
+ &rtc_old_handler );
+ assert ( rc == 0 ); /* Should always be able to unhook */
+}
+
+/**
+ * Enable RTC interrupts
+ *
+ */
+static void rtc_enable_int ( void ) {
+ uint8_t status_b;
+
+ /* Set Periodic Interrupt Enable bit in status register B */
+ outb ( ( RTC_STATUS_B | CMOS_DISABLE_NMI ), CMOS_ADDRESS );
+ status_b = inb ( CMOS_DATA );
+ outb ( ( RTC_STATUS_B | CMOS_DISABLE_NMI ), CMOS_ADDRESS );
+ outb ( ( status_b | RTC_STATUS_B_PIE ), CMOS_DATA );
+
+ /* Re-enable NMI and reset to default address */
+ outb ( CMOS_DEFAULT_ADDRESS, CMOS_ADDRESS );
+ inb ( CMOS_DATA ); /* Discard; may be needed on some platforms */
+}
+
+/**
+ * Disable RTC interrupts
+ *
+ */
+static void rtc_disable_int ( void ) {
+ uint8_t status_b;
+
+ /* Clear Periodic Interrupt Enable bit in status register B */
+ outb ( ( RTC_STATUS_B | CMOS_DISABLE_NMI ), CMOS_ADDRESS );
+ status_b = inb ( CMOS_DATA );
+ outb ( ( RTC_STATUS_B | CMOS_DISABLE_NMI ), CMOS_ADDRESS );
+ outb ( ( status_b & ~RTC_STATUS_B_PIE ), CMOS_DATA );
+
+ /* Re-enable NMI and reset to default address */
+ outb ( CMOS_DEFAULT_ADDRESS, CMOS_ADDRESS );
+ inb ( CMOS_DATA ); /* Discard; may be needed on some platforms */
+}
+
+/**
+ * Enable entropy gathering
+ *
+ * @ret rc Return status code
+ */
+static int rtc_entropy_enable ( void ) {
+
+ rtc_hook_isr();
+ enable_irq ( RTC_IRQ );
+ rtc_enable_int();
+
+ return 0;
+}
+
+/**
+ * Disable entropy gathering
+ *
+ */
+static void rtc_entropy_disable ( void ) {
+
+ rtc_disable_int();
+ disable_irq ( RTC_IRQ );
+ rtc_unhook_isr();
+}
+
+/**
+ * Measure a single RTC tick
+ *
+ * @ret delta Length of RTC tick (in TSC units)
+ */
+uint8_t rtc_sample ( void ) {
+ uint32_t before;
+ uint32_t after;
+ uint32_t temp;
+
+ __asm__ __volatile__ (
+ REAL_CODE ( /* Enable interrupts */
+ "sti\n\t"
+ /* Wait for RTC interrupt */
+ "cs movb %b2, %c4\n\t"
+ "\n1:\n\t"
+ "cs xchgb %b2, %c4\n\t" /* Serialize */
+ "testb %b2, %b2\n\t"
+ "jz 1b\n\t"
+ /* Read "before" TSC */
+ "rdtsc\n\t"
+ /* Store "before" TSC on stack */
+ "pushl %0\n\t"
+ /* Wait for another RTC interrupt */
+ "xorb %b2, %b2\n\t"
+ "cs movb %b2, %c4\n\t"
+ "\n1:\n\t"
+ "cs xchgb %b2, %c4\n\t" /* Serialize */
+ "testb %b2, %b2\n\t"
+ "jz 1b\n\t"
+ /* Read "after" TSC */
+ "rdtsc\n\t"
+ /* Retrieve "before" TSC on stack */
+ "popl %1\n\t"
+ /* Disable interrupts */
+ "cli\n\t"
+ )
+ : "=a" ( after ), "=d" ( before ), "=q" ( temp )
+ : "2" ( 0 ), "p" ( __from_text16 ( &rtc_flag ) ) );
+
+ return ( after - before );
+}
+
+PROVIDE_ENTROPY_INLINE ( rtc, min_entropy_per_sample );
+PROVIDE_ENTROPY ( rtc, entropy_enable, rtc_entropy_enable );
+PROVIDE_ENTROPY ( rtc, entropy_disable, rtc_entropy_disable );
+PROVIDE_ENTROPY_INLINE ( rtc, get_noise );
Code Review / kvmfornfv.git / blobdiff