include/asm-i386/bugs.h

   1 /*
   2  *  include/asm-i386/bugs.h
   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
  13 /*
  14  * This is included by init/main.c to check for architecture-dependent bugs.
  15  *
  16  * Needs:
  17  *      void check_bugs(void);
  18  */
  19
  20 #include <linux/init.h>
  21 #include <asm/processor.h>
  22 #include <asm/i387.h>
  23 #include <asm/msr.h>
  24
  25 static int __init no_halt(char *s)
  26 {
  27         boot_cpu_data.hlt_works_ok = 0;
  28         return 1;
  29 }
  30
  31 __setup("no-hlt", no_halt);
  32
  33 static int __init mca_pentium(char *s)
  34 {
  35         mca_pentium_flag = 1;
  36         return 1;
  37 }
  38
  39 __setup("mca-pentium", mca_pentium);
  40
  41 static int __init no_387(char *s)
  42 {
  43         boot_cpu_data.hard_math = 0;
  44         write_cr0(0xE | read_cr0());
  45         return 1;
  46 }
  47
  48 __setup("no387", no_387);
  49
  50 static double __initdata x = 4195835.0;
  51 static double __initdata y = 3145727.0;
  52
  53 /*
  54  * This used to check for exceptions..
  55  * However, it turns out that to support that,
  56  * the XMM trap handlers basically had to
  57  * be buggy. So let's have a correct XMM trap
  58  * handler, and forget about printing out
  59  * some status at boot.
  60  *
  61  * We should really only care about bugs here
  62  * anyway. Not features.
  63  */
  64 static void __init check_fpu(void)
  65 {
  66         if (!boot_cpu_data.hard_math) {
  67 #ifndef CONFIG_MATH_EMULATION
  68                 printk(KERN_EMERG "No coprocessor found and no math emulation present.\n");
  69                 printk(KERN_EMERG "Giving up.\n");
  70                 for (;;) ;
  71 #endif
  72                 return;
  73         }
  74
  75 /* trap_init() enabled FXSR and company _before_ testing for FP problems here. */
  76         /* Test for the divl bug.. */
  77         __asm__("fninit\n\t"
  78                 "fldl %1\n\t"
  79                 "fdivl %2\n\t"
  80                 "fmull %2\n\t"
  81                 "fldl %1\n\t"
  82                 "fsubp %%st,%%st(1)\n\t"
  83                 "fistpl %0\n\t"
  84                 "fwait\n\t"
  85                 "fninit"
  86                 : "=m" (*&boot_cpu_data.fdiv_bug)
  87                 : "m" (*&x), "m" (*&y));
  88         if (boot_cpu_data.fdiv_bug)
  89                 printk("Hmm, FPU with FDIV bug.\n");
  90 }
  91
  92 static void __init check_hlt(void)
  93 {
  94         printk(KERN_INFO "Checking 'hlt' instruction... ");
  95         if (!boot_cpu_data.hlt_works_ok) {
  96                 printk("disabled\n");
  97                 return;
  98         }
  99         halt();
 100         halt();
 101         halt();
 102         halt();
 103         printk("OK.\n");
 104 }
 105
 106 /*
 107  *      Most 386 processors have a bug where a POPAD can lock the
 108  *      machine even from user space.
 109  */
 110
 111 static void __init check_popad(void)
 112 {
 113 #ifndef CONFIG_X86_POPAD_OK
 114         int res, inp = (int) &res;
 115
 116         printk(KERN_INFO "Checking for popad bug... ");
 117         __asm__ __volatile__(
 118           "movl $12345678,%%eax; movl $0,%%edi; pusha; popa; movl (%%edx,%%edi),%%ecx "
 119           : "=&a" (res)
 120           : "d" (inp)
 121           : "ecx", "edi" );
 122         /* If this fails, it means that any user program may lock the CPU hard. Too bad. */
 123         if (res != 12345678) printk( "Buggy.\n" );
 124                         else printk( "OK.\n" );
 125 #endif
 126 }
 127
 128 /*
 129  * Check whether we are able to run this kernel safely on SMP.
 130  *
 131  * - In order to run on a i386, we need to be compiled for i386
 132  *   (for due to lack of "invlpg" and working WP on a i386)
 133  * - In order to run on anything without a TSC, we need to be
 134  *   compiled for a i486.
 135  * - In order to support the local APIC on a buggy Pentium machine,
 136  *   we need to be compiled with CONFIG_X86_GOOD_APIC disabled,
 137  *   which happens implicitly if compiled for a Pentium or lower
 138  *   (unless an advanced selection of CPU features is used) as an
 139  *   otherwise config implies a properly working local APIC without
 140  *   the need to do extra reads from the APIC.
 141 */
 142
 143 static void __init check_config(void)
 144 {
 145 /*
 146  * We'd better not be a i386 if we're configured to use some
 147  * i486+ only features! (WP works in supervisor mode and the
 148  * new "invlpg" and "bswap" instructions)
 149  */
 150 #if defined(CONFIG_X86_WP_WORKS_OK) || defined(CONFIG_X86_INVLPG) || defined(CONFIG_X86_BSWAP)
 151         if (boot_cpu_data.x86 == 3)
 152                 panic("Kernel requires i486+ for 'invlpg' and other features");
 153 #endif
 154
 155 /*
 156  * If we configured ourselves for a TSC, we'd better have one!
 157  */
 158 #ifdef CONFIG_X86_TSC
 159         if (!cpu_has_tsc)
 160                 panic("Kernel compiled for Pentium+, requires TSC feature!");
 161 #endif
 162
 163 /*
 164  * If we were told we had a good local APIC, check for buggy Pentia,
 165  * i.e. all B steppings and the C2 stepping of P54C when using their
 166  * integrated APIC (see 11AP erratum in "Pentium Processor
 167  * Specification Update").
 168  */
 169 #if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_X86_GOOD_APIC)
 170         if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL
 171             && cpu_has_apic
 172             && boot_cpu_data.x86 == 5
 173             && boot_cpu_data.x86_model == 2
 174             && (boot_cpu_data.x86_mask < 6 || boot_cpu_data.x86_mask == 11))
 175                 panic("Kernel compiled for PMMX+, assumes a local APIC without the read-before-write bug!");
 176 #endif
 177 }
 178
 179 extern void alternative_instructions(void);
 180
 181 static void __init check_bugs(void)
 182 {
 183         identify_cpu(&boot_cpu_data);
 184 #ifndef CONFIG_SMP
 185         printk("CPU: ");
 186         print_cpu_info(&boot_cpu_data);
 187 #endif
 188         check_config();
 189         check_fpu();
 190         check_hlt();
 191         check_popad();
 192         init_utsname()->machine[1] = '0' + (boot_cpu_data.x86 > 6 ? 6 : boot_cpu_data.x86);
 193         alternative_instructions();
 194 }