| 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 |