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