1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
|
/*
* 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 );
|
