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 WARN_ONCE(1, "\"no-hlt\" is deprecated, please use \"idle=poll\"\n"); 23 boot_cpu_data.hlt_works_ok = 0; 24 return 1; 25 } 26 27 __setup("no-hlt", no_halt); 28 29 static int __init no_387(char *s) 30 { 31 boot_cpu_data.hard_math = 0; 32 write_cr0(X86_CR0_TS | X86_CR0_EM | X86_CR0_MP | read_cr0()); 33 return 1; 34 } 35 36 __setup("no387", no_387); 37 38 static double __initdata x = 4195835.0; 39 static double __initdata y = 3145727.0; 40 41 /* 42 * This used to check for exceptions.. 43 * However, it turns out that to support that, 44 * the XMM trap handlers basically had to 45 * be buggy. So let's have a correct XMM trap 46 * handler, and forget about printing out 47 * some status at boot. 48 * 49 * We should really only care about bugs here 50 * anyway. Not features. 51 */ 52 static void __init check_fpu(void) 53 { 54 s32 fdiv_bug; 55 56 if (!boot_cpu_data.hard_math) { 57 #ifndef CONFIG_MATH_EMULATION 58 printk(KERN_EMERG "No coprocessor found and no math emulation present.\n"); 59 printk(KERN_EMERG "Giving up.\n"); 60 for (;;) ; 61 #endif 62 return; 63 } 64 65 /* 66 * trap_init() enabled FXSR and company _before_ testing for FP 67 * problems here. 68 * 69 * Test for the divl bug.. 70 */ 71 __asm__("fninit\n\t" 72 "fldl %1\n\t" 73 "fdivl %2\n\t" 74 "fmull %2\n\t" 75 "fldl %1\n\t" 76 "fsubp %%st,%%st(1)\n\t" 77 "fistpl %0\n\t" 78 "fwait\n\t" 79 "fninit" 80 : "=m" (*&fdiv_bug) 81 : "m" (*&x), "m" (*&y)); 82 83 boot_cpu_data.fdiv_bug = fdiv_bug; 84 if (boot_cpu_data.fdiv_bug) 85 printk(KERN_WARNING "Hmm, FPU with FDIV bug.\n"); 86 } 87 88 static void __init check_hlt(void) 89 { 90 if (boot_cpu_data.x86 >= 5 || paravirt_enabled()) 91 return; 92 93 printk(KERN_INFO "Checking 'hlt' instruction... "); 94 if (!boot_cpu_data.hlt_works_ok) { 95 printk("disabled\n"); 96 return; 97 } 98 halt(); 99 halt(); 100 halt(); 101 halt(); 102 printk(KERN_CONT "OK.\n"); 103 } 104 105 /* 106 * Most 386 processors have a bug where a POPAD can lock the 107 * machine even from user space. 108 */ 109 110 static void __init check_popad(void) 111 { 112 #ifndef CONFIG_X86_POPAD_OK 113 int res, inp = (int) &res; 114 115 printk(KERN_INFO "Checking for popad bug... "); 116 __asm__ __volatile__( 117 "movl $12345678,%%eax; movl $0,%%edi; pusha; popa; movl (%%edx,%%edi),%%ecx " 118 : "=&a" (res) 119 : "d" (inp) 120 : "ecx", "edi"); 121 /* 122 * If this fails, it means that any user program may lock the 123 * CPU hard. Too bad. 124 */ 125 if (res != 12345678) 126 printk(KERN_CONT "Buggy.\n"); 127 else 128 printk(KERN_CONT "OK.\n"); 129 #endif 130 } 131 132 /* 133 * Check whether we are able to run this kernel safely on SMP. 134 * 135 * - In order to run on a i386, we need to be compiled for i386 136 * (for due to lack of "invlpg" and working WP on a i386) 137 * - In order to run on anything without a TSC, we need to be 138 * compiled for a i486. 139 */ 140 141 static void __init check_config(void) 142 { 143 /* 144 * We'd better not be a i386 if we're configured to use some 145 * i486+ only features! (WP works in supervisor mode and the 146 * new "invlpg" and "bswap" instructions) 147 */ 148 #if defined(CONFIG_X86_WP_WORKS_OK) || defined(CONFIG_X86_INVLPG) || \ 149 defined(CONFIG_X86_BSWAP) 150 if (boot_cpu_data.x86 == 3) 151 panic("Kernel requires i486+ for 'invlpg' and other features"); 152 #endif 153 } 154 155 156 void __init check_bugs(void) 157 { 158 identify_boot_cpu(); 159 #ifndef CONFIG_SMP 160 printk(KERN_INFO "CPU: "); 161 print_cpu_info(&boot_cpu_data); 162 #endif 163 check_config(); 164 check_fpu(); 165 check_hlt(); 166 check_popad(); 167 init_utsname()->machine[1] = 168 '0' + (boot_cpu_data.x86 > 6 ? 6 : boot_cpu_data.x86); 169 alternative_instructions(); 170 } 171