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(&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