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 pr_emerg("No coprocessor found and no math emulation present\n"); 59 pr_emerg("Giving up\n"); 60 for (;;) ; 61 #endif 62 return; 63 } 64 65 kernel_fpu_begin(); 66 67 /* 68 * trap_init() enabled FXSR and company _before_ testing for FP 69 * problems here. 70 * 71 * Test for the divl bug.. 72 */ 73 __asm__("fninit\n\t" 74 "fldl %1\n\t" 75 "fdivl %2\n\t" 76 "fmull %2\n\t" 77 "fldl %1\n\t" 78 "fsubp %%st,%%st(1)\n\t" 79 "fistpl %0\n\t" 80 "fwait\n\t" 81 "fninit" 82 : "=m" (*&fdiv_bug) 83 : "m" (*&x), "m" (*&y)); 84 85 kernel_fpu_end(); 86 87 boot_cpu_data.fdiv_bug = fdiv_bug; 88 if (boot_cpu_data.fdiv_bug) 89 pr_warn("Hmm, FPU with FDIV bug\n"); 90 } 91 92 static void __init check_hlt(void) 93 { 94 if (boot_cpu_data.x86 >= 5 || paravirt_enabled()) 95 return; 96 97 pr_info("Checking 'hlt' instruction... "); 98 if (!boot_cpu_data.hlt_works_ok) { 99 pr_cont("disabled\n"); 100 return; 101 } 102 halt(); 103 halt(); 104 halt(); 105 halt(); 106 pr_cont("OK\n"); 107 } 108 109 /* 110 * Most 386 processors have a bug where a POPAD can lock the 111 * machine even from user space. 112 */ 113 114 static void __init check_popad(void) 115 { 116 #ifndef CONFIG_X86_POPAD_OK 117 int res, inp = (int) &res; 118 119 pr_info("Checking for popad bug... "); 120 __asm__ __volatile__( 121 "movl $12345678,%%eax; movl $0,%%edi; pusha; popa; movl (%%edx,%%edi),%%ecx " 122 : "=&a" (res) 123 : "d" (inp) 124 : "ecx", "edi"); 125 /* 126 * If this fails, it means that any user program may lock the 127 * CPU hard. Too bad. 128 */ 129 if (res != 12345678) 130 pr_cont("Buggy\n"); 131 else 132 pr_cont("OK\n"); 133 #endif 134 } 135 136 /* 137 * Check whether we are able to run this kernel safely on SMP. 138 * 139 * - In order to run on a i386, we need to be compiled for i386 140 * (for due to lack of "invlpg" and working WP on a i386) 141 * - In order to run on anything without a TSC, we need to be 142 * compiled for a i486. 143 */ 144 145 static void __init check_config(void) 146 { 147 /* 148 * We'd better not be a i386 if we're configured to use some 149 * i486+ only features! (WP works in supervisor mode and the 150 * new "invlpg" and "bswap" instructions) 151 */ 152 #if defined(CONFIG_X86_WP_WORKS_OK) || defined(CONFIG_X86_INVLPG) || \ 153 defined(CONFIG_X86_BSWAP) 154 if (boot_cpu_data.x86 == 3) 155 panic("Kernel requires i486+ for 'invlpg' and other features"); 156 #endif 157 } 158 159 160 void __init check_bugs(void) 161 { 162 identify_boot_cpu(); 163 #ifndef CONFIG_SMP 164 pr_info("CPU: "); 165 print_cpu_info(&boot_cpu_data); 166 #endif 167 check_config(); 168 check_fpu(); 169 check_hlt(); 170 check_popad(); 171 init_utsname()->machine[1] = 172 '0' + (boot_cpu_data.x86 > 6 ? 6 : boot_cpu_data.x86); 173 alternative_instructions(); 174 } 175