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b2441318 | 1 | // SPDX-License-Identifier: GPL-2.0 |
d899a7d1 TG |
2 | /* |
3 | * Entropy functions used on early boot for KASLR base and memory | |
4 | * randomization. The base randomization is done in the compressed | |
5 | * kernel and memory randomization is done early when the regular | |
6 | * kernel starts. This file is included in the compressed kernel and | |
7 | * normally linked in the regular. | |
8 | */ | |
121843eb | 9 | #include <asm/asm.h> |
d899a7d1 TG |
10 | #include <asm/kaslr.h> |
11 | #include <asm/msr.h> | |
12 | #include <asm/archrandom.h> | |
66441bd3 | 13 | #include <asm/e820/api.h> |
adb5680b | 14 | #include <asm/shared/io.h> |
d899a7d1 TG |
15 | |
16 | /* | |
17 | * When built for the regular kernel, several functions need to be stubbed out | |
18 | * or changed to their regular kernel equivalent. | |
19 | */ | |
20 | #ifndef KASLR_COMPRESSED_BOOT | |
21 | #include <asm/cpufeature.h> | |
22 | #include <asm/setup.h> | |
23 | ||
62d16b5a | 24 | #define debug_putstr(v) early_printk("%s", v) |
d899a7d1 TG |
25 | #define has_cpuflag(f) boot_cpu_has(f) |
26 | #define get_boot_seed() kaslr_offset() | |
27 | #endif | |
28 | ||
29 | #define I8254_PORT_CONTROL 0x43 | |
30 | #define I8254_PORT_COUNTER0 0x40 | |
31 | #define I8254_CMD_READBACK 0xC0 | |
32 | #define I8254_SELECT_COUNTER0 0x02 | |
33 | #define I8254_STATUS_NOTREADY 0x40 | |
34 | static inline u16 i8254(void) | |
35 | { | |
36 | u16 status, timer; | |
37 | ||
38 | do { | |
7e6fc2f5 DD |
39 | outb(I8254_CMD_READBACK | I8254_SELECT_COUNTER0, |
40 | I8254_PORT_CONTROL); | |
d899a7d1 TG |
41 | status = inb(I8254_PORT_COUNTER0); |
42 | timer = inb(I8254_PORT_COUNTER0); | |
43 | timer |= inb(I8254_PORT_COUNTER0) << 8; | |
44 | } while (status & I8254_STATUS_NOTREADY); | |
45 | ||
46 | return timer; | |
47 | } | |
48 | ||
49 | unsigned long kaslr_get_random_long(const char *purpose) | |
50 | { | |
51 | #ifdef CONFIG_X86_64 | |
52 | const unsigned long mix_const = 0x5d6008cbf3848dd3UL; | |
53 | #else | |
54 | const unsigned long mix_const = 0x3f39e593UL; | |
55 | #endif | |
56 | unsigned long raw, random = get_boot_seed(); | |
57 | bool use_i8254 = true; | |
58 | ||
0d054d4e KC |
59 | if (purpose) { |
60 | debug_putstr(purpose); | |
61 | debug_putstr(" KASLR using"); | |
62 | } | |
d899a7d1 TG |
63 | |
64 | if (has_cpuflag(X86_FEATURE_RDRAND)) { | |
0d054d4e KC |
65 | if (purpose) |
66 | debug_putstr(" RDRAND"); | |
d899a7d1 TG |
67 | if (rdrand_long(&raw)) { |
68 | random ^= raw; | |
69 | use_i8254 = false; | |
70 | } | |
71 | } | |
72 | ||
73 | if (has_cpuflag(X86_FEATURE_TSC)) { | |
0d054d4e KC |
74 | if (purpose) |
75 | debug_putstr(" RDTSC"); | |
d899a7d1 TG |
76 | raw = rdtsc(); |
77 | ||
78 | random ^= raw; | |
79 | use_i8254 = false; | |
80 | } | |
81 | ||
82 | if (use_i8254) { | |
0d054d4e KC |
83 | if (purpose) |
84 | debug_putstr(" i8254"); | |
d899a7d1 TG |
85 | random ^= i8254(); |
86 | } | |
87 | ||
88 | /* Circular multiply for better bit diffusion */ | |
121843eb | 89 | asm(_ASM_MUL "%3" |
d899a7d1 TG |
90 | : "=a" (random), "=d" (raw) |
91 | : "a" (random), "rm" (mix_const)); | |
92 | random += raw; | |
93 | ||
0d054d4e KC |
94 | if (purpose) |
95 | debug_putstr("...\n"); | |
d899a7d1 TG |
96 | |
97 | return random; | |
98 | } |