diff options
Diffstat (limited to 'qemu/roms/ipxe/src/arch/i386/interface/pcbios/rtc_entropy.c')
| -rw-r--r-- | qemu/roms/ipxe/src/arch/i386/interface/pcbios/rtc_entropy.c | 199 |
1 files changed, 199 insertions, 0 deletions
diff --git a/qemu/roms/ipxe/src/arch/i386/interface/pcbios/rtc_entropy.c b/qemu/roms/ipxe/src/arch/i386/interface/pcbios/rtc_entropy.c new file mode 100644 index 000000000..fad421c2a --- /dev/null +++ b/qemu/roms/ipxe/src/arch/i386/interface/pcbios/rtc_entropy.c @@ -0,0 +1,199 @@ +/* + * 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 ); |