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/asm.h> 9 #include <asm/kaslr.h> 10 #include <asm/msr.h> 11 #include <asm/archrandom.h> 12 #include <asm/e820/api.h> 13 #include <asm/io.h> 14 15 /* 16 * When built for the regular kernel, several functions need to be stubbed out 17 * or changed to their regular kernel equivalent. 18 */ 19 #ifndef KASLR_COMPRESSED_BOOT 20 #include <asm/cpufeature.h> 21 #include <asm/setup.h> 22 23 #define debug_putstr(v) early_printk("%s", v) 24 #define has_cpuflag(f) boot_cpu_has(f) 25 #define get_boot_seed() kaslr_offset() 26 #endif 27 28 #define I8254_PORT_CONTROL 0x43 29 #define I8254_PORT_COUNTER0 0x40 30 #define I8254_CMD_READBACK 0xC0 31 #define I8254_SELECT_COUNTER0 0x02 32 #define I8254_STATUS_NOTREADY 0x40 33 static inline u16 i8254(void) 34 { 35 u16 status, timer; 36 37 do { 38 outb(I8254_PORT_CONTROL, 39 I8254_CMD_READBACK | I8254_SELECT_COUNTER0); 40 status = inb(I8254_PORT_COUNTER0); 41 timer = inb(I8254_PORT_COUNTER0); 42 timer |= inb(I8254_PORT_COUNTER0) << 8; 43 } while (status & I8254_STATUS_NOTREADY); 44 45 return timer; 46 } 47 48 unsigned long kaslr_get_random_long(const char *purpose) 49 { 50 #ifdef CONFIG_X86_64 51 const unsigned long mix_const = 0x5d6008cbf3848dd3UL; 52 #else 53 const unsigned long mix_const = 0x3f39e593UL; 54 #endif 55 unsigned long raw, random = get_boot_seed(); 56 bool use_i8254 = true; 57 58 debug_putstr(purpose); 59 debug_putstr(" KASLR using"); 60 61 if (has_cpuflag(X86_FEATURE_RDRAND)) { 62 debug_putstr(" RDRAND"); 63 if (rdrand_long(&raw)) { 64 random ^= raw; 65 use_i8254 = false; 66 } 67 } 68 69 if (has_cpuflag(X86_FEATURE_TSC)) { 70 debug_putstr(" RDTSC"); 71 raw = rdtsc(); 72 73 random ^= raw; 74 use_i8254 = false; 75 } 76 77 if (use_i8254) { 78 debug_putstr(" i8254"); 79 random ^= i8254(); 80 } 81 82 /* Circular multiply for better bit diffusion */ 83 asm(_ASM_MUL "%3" 84 : "=a" (random), "=d" (raw) 85 : "a" (random), "rm" (mix_const)); 86 random += raw; 87 88 debug_putstr("...\n"); 89 90 return random; 91 } 92