1 | // SPDX-License-Identifier: GPL-2.0 |
---|---|
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 | */ |
9 | #include <asm/asm.h> |
10 | #include <asm/kaslr.h> |
11 | #include <asm/msr.h> |
12 | #include <asm/archrandom.h> |
13 | #include <asm/e820/api.h> |
14 | #include <asm/shared/io.h> |
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 | |
24 | #define debug_putstr(v) early_printk("%s", v) |
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 { |
39 | outb(I8254_CMD_READBACK | I8254_SELECT_COUNTER0, |
40 | I8254_PORT_CONTROL); |
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 | |
59 | if (purpose) { |
60 | debug_putstr(purpose); |
61 | debug_putstr(" KASLR using"); |
62 | } |
63 | |
64 | if (has_cpuflag(X86_FEATURE_RDRAND)) { |
65 | if (purpose) |
66 | debug_putstr(" RDRAND"); |
67 | if (rdrand_long(v: &raw)) { |
68 | random ^= raw; |
69 | use_i8254 = false; |
70 | } |
71 | } |
72 | |
73 | if (has_cpuflag(X86_FEATURE_TSC)) { |
74 | if (purpose) |
75 | debug_putstr(" RDTSC"); |
76 | raw = rdtsc(); |
77 | |
78 | random ^= raw; |
79 | use_i8254 = false; |
80 | } |
81 | |
82 | if (use_i8254) { |
83 | if (purpose) |
84 | debug_putstr(" i8254"); |
85 | random ^= i8254(); |
86 | } |
87 | |
88 | /* Circular multiply for better bit diffusion */ |
89 | asm(_ASM_MUL "%3" |
90 | : "=a"(random), "=d"(raw) |
91 | : "a"(random), "rm"(mix_const)); |
92 | random += raw; |
93 | |
94 | if (purpose) |
95 | debug_putstr("...\n"); |
96 | |
97 | return random; |
98 | } |
99 |