1/* 2 * arch/i386/cpu/bugs.c 3 * 4 * Copyright (C) 1994 Linus Torvalds 5 * 6 * Cyrix stuff, June 1998 by: 7 * - Rafael R. Reilova (moved everything from head.S), 8 * <rreilova@ececs.uc.edu> 9 * - Channing Corn (tests & fixes), 10 * - Andrew D. Balsa (code cleanup). 11 */ 12#include <linux/init.h> 13#include <linux/utsname.h> 14#include <asm/processor.h> 15#include <asm/i387.h> 16#include <asm/msr.h> 17#include <asm/paravirt.h> 18#include <asm/alternative.h> 19 20static 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 28static int __init mca_pentium(char *s) 29{ 30 mca_pentium_flag = 1; 31 return 1; 32} 33 34__setup("mca-pentium", mca_pentium); 35 36static int __init no_387(char *s) 37{ 38 boot_cpu_data.hard_math = 0; 39 write_cr0(0xE | read_cr0()); 40 return 1; 41} 42 43__setup("no387", no_387); 44 45static double __initdata x = 4195835.0; 46static double __initdata y = 3145727.0; 47 48/* 49 * This used to check for exceptions.. 50 * However, it turns out that to support that, 51 * the XMM trap handlers basically had to 52 * be buggy. So let's have a correct XMM trap 53 * handler, and forget about printing out 54 * some status at boot. 55 * 56 * We should really only care about bugs here 57 * anyway. Not features. 58 */ 59static void __init check_fpu(void) 60{ 61 if (!boot_cpu_data.hard_math) { 62#ifndef CONFIG_MATH_EMULATION 63 printk(KERN_EMERG "No coprocessor found and no math emulation present.\n"); 64 printk(KERN_EMERG "Giving up.\n"); 65 for (;;) ; 66#endif 67 return; 68 } 69 70/* trap_init() enabled FXSR and company _before_ testing for FP problems here. */ 71 /* Test for the divl bug.. */ 72 __asm__("fninit\n\t" 73 "fldl %1\n\t" 74 "fdivl %2\n\t" 75 "fmull %2\n\t" 76 "fldl %1\n\t" 77 "fsubp %%st,%%st(1)\n\t" 78 "fistpl %0\n\t" 79 "fwait\n\t" 80 "fninit" 81 : "=m" (*&boot_cpu_data.fdiv_bug) 82 : "m" (*&x), "m" (*&y)); 83 if (boot_cpu_data.fdiv_bug) 84 printk("Hmm, FPU with FDIV bug.\n"); 85} 86 87static void __init check_hlt(void) 88{ 89 if (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("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 109static 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 /* If this fails, it means that any user program may lock the CPU hard. Too bad. */ 121 if (res != 12345678) printk( "Buggy.\n" ); 122 else printk( "OK.\n" ); 123#endif 124} 125 126/* 127 * Check whether we are able to run this kernel safely on SMP. 128 * 129 * - In order to run on a i386, we need to be compiled for i386 130 * (for due to lack of "invlpg" and working WP on a i386) 131 * - In order to run on anything without a TSC, we need to be 132 * compiled for a i486. 133 * - In order to support the local APIC on a buggy Pentium machine, 134 * we need to be compiled with CONFIG_X86_GOOD_APIC disabled, 135 * which happens implicitly if compiled for a Pentium or lower 136 * (unless an advanced selection of CPU features is used) as an 137 * otherwise config implies a properly working local APIC without 138 * the need to do extra reads from the APIC. 139*/ 140 141static 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 * If we configured ourselves for a TSC, we'd better have one! 156 */ 157#ifdef CONFIG_X86_TSC 158 if (!cpu_has_tsc && !tsc_disable) 159 panic("Kernel compiled for Pentium+, requires TSC feature!"); 160#endif 161 162/* 163 * If we were told we had a good local APIC, check for buggy Pentia, 164 * i.e. all B steppings and the C2 stepping of P54C when using their 165 * integrated APIC (see 11AP erratum in "Pentium Processor 166 * Specification Update"). 167 */ 168#if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_X86_GOOD_APIC) 169 if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL 170 && cpu_has_apic 171 && boot_cpu_data.x86 == 5 172 && boot_cpu_data.x86_model == 2 173 && (boot_cpu_data.x86_mask < 6 || boot_cpu_data.x86_mask == 11)) 174 panic("Kernel compiled for PMMX+, assumes a local APIC without the read-before-write bug!"); 175#endif 176} 177 178 179void __init check_bugs(void) 180{ 181 identify_boot_cpu(); 182#ifndef CONFIG_SMP 183 printk("CPU: "); 184 print_cpu_info(&boot_cpu_data); 185#endif 186 check_config(); 187 check_fpu(); 188 check_hlt(); 189 check_popad(); 190 init_utsname()->machine[1] = '0' + (boot_cpu_data.x86 > 6 ? 6 : boot_cpu_data.x86); 191 alternative_instructions(); 192} 193