1 /* 2 * Copyright (C) 1994 Linus Torvalds 3 * 4 * Cyrix stuff, June 1998 by: 5 * - Rafael R. Reilova (moved everything from head.S), 6 * <rreilova@ececs.uc.edu> 7 * - Channing Corn (tests & fixes), 8 * - Andrew D. Balsa (code cleanup). 9 */ 10 #include <linux/init.h> 11 #include <linux/utsname.h> 12 #include <asm/bugs.h> 13 #include <asm/processor.h> 14 #include <asm/processor-flags.h> 15 #include <asm/i387.h> 16 #include <asm/msr.h> 17 #include <asm/paravirt.h> 18 #include <asm/alternative.h> 19 20 static int __init no_halt(char *s) 21 { 22 boot_cpu_data.hlt_works_ok = 0; 23 return 1; 24 } 25 26 __setup("no-hlt", no_halt); 27 28 static int __init no_387(char *s) 29 { 30 boot_cpu_data.hard_math = 0; 31 write_cr0(X86_CR0_TS | X86_CR0_EM | X86_CR0_MP | read_cr0()); 32 return 1; 33 } 34 35 __setup("no387", no_387); 36 37 static double __initdata x = 4195835.0; 38 static double __initdata y = 3145727.0; 39 40 /* 41 * This used to check for exceptions.. 42 * However, it turns out that to support that, 43 * the XMM trap handlers basically had to 44 * be buggy. So let's have a correct XMM trap 45 * handler, and forget about printing out 46 * some status at boot. 47 * 48 * We should really only care about bugs here 49 * anyway. Not features. 50 */ 51 static void __init check_fpu(void) 52 { 53 s32 fdiv_bug; 54 55 if (!boot_cpu_data.hard_math) { 56 #ifndef CONFIG_MATH_EMULATION 57 printk(KERN_EMERG "No coprocessor found and no math emulation present.\n"); 58 printk(KERN_EMERG "Giving up.\n"); 59 for (;;) ; 60 #endif 61 return; 62 } 63 64 /* 65 * trap_init() enabled FXSR and company _before_ testing for FP 66 * problems here. 67 * 68 * Test for the divl bug.. 69 */ 70 __asm__("fninit\n\t" 71 "fldl %1\n\t" 72 "fdivl %2\n\t" 73 "fmull %2\n\t" 74 "fldl %1\n\t" 75 "fsubp %%st,%%st(1)\n\t" 76 "fistpl %0\n\t" 77 "fwait\n\t" 78 "fninit" 79 : "=m" (*&fdiv_bug) 80 : "m" (*&x), "m" (*&y)); 81 82 boot_cpu_data.fdiv_bug = fdiv_bug; 83 if (boot_cpu_data.fdiv_bug) 84 printk(KERN_WARNING "Hmm, FPU with FDIV bug.\n"); 85 } 86 87 static void __init check_hlt(void) 88 { 89 if (boot_cpu_data.x86 >= 5 || paravirt_enabled()) 90 return; 91 92 printk(KERN_INFO "Checking 'hlt' instruction... "); 93 if (!boot_cpu_data.hlt_works_ok) { 94 printk("disabled\n"); 95 return; 96 } 97 halt(); 98 halt(); 99 halt(); 100 halt(); 101 printk(KERN_CONT "OK.\n"); 102 } 103 104 /* 105 * Most 386 processors have a bug where a POPAD can lock the 106 * machine even from user space. 107 */ 108 109 static void __init check_popad(void) 110 { 111 #ifndef CONFIG_X86_POPAD_OK 112 int res, inp = (int) &res; 113 114 printk(KERN_INFO "Checking for popad bug... "); 115 __asm__ __volatile__( 116 "movl $12345678,%%eax; movl $0,%%edi; pusha; popa; movl (%%edx,%%edi),%%ecx " 117 : "=&a" (res) 118 : "d" (inp) 119 : "ecx", "edi"); 120 /* 121 * If this fails, it means that any user program may lock the 122 * CPU hard. Too bad. 123 */ 124 if (res != 12345678) 125 printk(KERN_CONT "Buggy.\n"); 126 else 127 printk(KERN_CONT "OK.\n"); 128 #endif 129 } 130 131 /* 132 * Check whether we are able to run this kernel safely on SMP. 133 * 134 * - In order to run on a i386, we need to be compiled for i386 135 * (for due to lack of "invlpg" and working WP on a i386) 136 * - In order to run on anything without a TSC, we need to be 137 * compiled for a i486. 138 */ 139 140 static void __init check_config(void) 141 { 142 /* 143 * We'd better not be a i386 if we're configured to use some 144 * i486+ only features! (WP works in supervisor mode and the 145 * new "invlpg" and "bswap" instructions) 146 */ 147 #if defined(CONFIG_X86_WP_WORKS_OK) || defined(CONFIG_X86_INVLPG) || \ 148 defined(CONFIG_X86_BSWAP) 149 if (boot_cpu_data.x86 == 3) 150 panic("Kernel requires i486+ for 'invlpg' and other features"); 151 #endif 152 } 153 154 155 void __init check_bugs(void) 156 { 157 identify_boot_cpu(); 158 #ifndef CONFIG_SMP 159 printk(KERN_INFO "CPU: "); 160 print_cpu_info(&boot_cpu_data); 161 #endif 162 check_config(); 163 check_fpu(); 164 check_hlt(); 165 check_popad(); 166 init_utsname()->machine[1] = 167 '0' + (boot_cpu_data.x86 > 6 ? 6 : boot_cpu_data.x86); 168 alternative_instructions(); 169 } 170