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 if (!boot_cpu_data.hard_math) { 54 #ifndef CONFIG_MATH_EMULATION 55 printk(KERN_EMERG "No coprocessor found and no math emulation present.\n"); 56 printk(KERN_EMERG "Giving up.\n"); 57 for (;;) ; 58 #endif 59 return; 60 } 61 62 /* 63 * trap_init() enabled FXSR and company _before_ testing for FP 64 * problems here. 65 * 66 * Test for the divl bug.. 67 */ 68 __asm__("fninit\n\t" 69 "fldl %1\n\t" 70 "fdivl %2\n\t" 71 "fmull %2\n\t" 72 "fldl %1\n\t" 73 "fsubp %%st,%%st(1)\n\t" 74 "fistpl %0\n\t" 75 "fwait\n\t" 76 "fninit" 77 : "=m" (*&boot_cpu_data.fdiv_bug) 78 : "m" (*&x), "m" (*&y)); 79 if (boot_cpu_data.fdiv_bug) 80 printk("Hmm, FPU with FDIV bug.\n"); 81 } 82 83 static void __init check_hlt(void) 84 { 85 if (paravirt_enabled()) 86 return; 87 88 printk(KERN_INFO "Checking 'hlt' instruction... "); 89 if (!boot_cpu_data.hlt_works_ok) { 90 printk("disabled\n"); 91 return; 92 } 93 halt(); 94 halt(); 95 halt(); 96 halt(); 97 printk("OK.\n"); 98 } 99 100 /* 101 * Most 386 processors have a bug where a POPAD can lock the 102 * machine even from user space. 103 */ 104 105 static void __init check_popad(void) 106 { 107 #ifndef CONFIG_X86_POPAD_OK 108 int res, inp = (int) &res; 109 110 printk(KERN_INFO "Checking for popad bug... "); 111 __asm__ __volatile__( 112 "movl $12345678,%%eax; movl $0,%%edi; pusha; popa; movl (%%edx,%%edi),%%ecx " 113 : "=&a" (res) 114 : "d" (inp) 115 : "ecx", "edi"); 116 /* 117 * If this fails, it means that any user program may lock the 118 * CPU hard. Too bad. 119 */ 120 if (res != 12345678) 121 printk("Buggy.\n"); 122 else 123 printk("OK.\n"); 124 #endif 125 } 126 127 /* 128 * Check whether we are able to run this kernel safely on SMP. 129 * 130 * - In order to run on a i386, we need to be compiled for i386 131 * (for due to lack of "invlpg" and working WP on a i386) 132 * - In order to run on anything without a TSC, we need to be 133 * compiled for a i486. 134 */ 135 136 static void __init check_config(void) 137 { 138 /* 139 * We'd better not be a i386 if we're configured to use some 140 * i486+ only features! (WP works in supervisor mode and the 141 * new "invlpg" and "bswap" instructions) 142 */ 143 #if defined(CONFIG_X86_WP_WORKS_OK) || defined(CONFIG_X86_INVLPG) || \ 144 defined(CONFIG_X86_BSWAP) 145 if (boot_cpu_data.x86 == 3) 146 panic("Kernel requires i486+ for 'invlpg' and other features"); 147 #endif 148 } 149 150 151 void __init check_bugs(void) 152 { 153 identify_boot_cpu(); 154 #ifndef CONFIG_SMP 155 printk("CPU: "); 156 print_cpu_info(&boot_cpu_data); 157 #endif 158 check_config(); 159 check_fpu(); 160 check_hlt(); 161 check_popad(); 162 init_utsname()->machine[1] = 163 '0' + (boot_cpu_data.x86 > 6 ? 6 : boot_cpu_data.x86); 164 alternative_instructions(); 165 } 166