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- /*
- * 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.
- *
- * You can also choose to distribute this program under the terms of
- * the Unmodified Binary Distribution Licence (as given in the file
- * COPYING.UBDL), provided that you have satisfied its requirements.
- */
-
- FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
-
- /** @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 );
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