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/config.h>
  21 #include <linux/init.h>
  22 #include <asm/processor.h>
  23 #include <asm/i387.h>
  24 #include <asm/msr.h>
  25
  26 static int __init no_halt(char *s)
  27 {
  28         boot_cpu_data.hlt_works_ok = 0;
  29         return 1;
  30 }
  31
  32 __setup("no-hlt", no_halt);
  33
  34 static int __init mca_pentium(char *s)
  35 {
  36         mca_pentium_flag = 1;
  37         return 1;
  38 }
  39
  40 __setup("mca-pentium", mca_pentium);
  41
  42 static int __init no_387(char *s)
  43 {
  44         boot_cpu_data.hard_math = 0;
  45         write_cr0(0xE | read_cr0());
  46         return 1;
  47 }
  48
  49 __setup("no387", no_387);
  50
  51 static double __initdata x = 4195835.0;
  52 static double __initdata y = 3145727.0;
  53
  54 /*
  55  * This used to check for exceptions..
  56  * However, it turns out that to support that,
  57  * the XMM trap handlers basically had to
  58  * be buggy. So let's have a correct XMM trap
  59  * handler, and forget about printing out
  60  * some status at boot.
  61  *
  62  * We should really only care about bugs here
  63  * anyway. Not features.
  64  */
  65 static void __init check_fpu(void)
  66 {
  67         if (!boot_cpu_data.hard_math) {
  68 #ifndef CONFIG_MATH_EMULATION
  69                 printk(KERN_EMERG "No coprocessor found and no math emulation present.\n");
  70                 printk(KERN_EMERG "Giving up.\n");
  71                 for (;;) ;
  72 #endif
  73                 return;
  74         }
  75
  76 /* trap_init() enabled FXSR and company _before_ testing for FP problems here. */
  77         /* Test for the divl bug.. */
  78         __asm__("fninit\n\t"
  79                 "fldl %1\n\t"
  80                 "fdivl %2\n\t"
  81                 "fmull %2\n\t"
  82                 "fldl %1\n\t"
  83                 "fsubp %%st,%%st(1)\n\t"
  84                 "fistpl %0\n\t"
  85                 "fwait\n\t"
  86                 "fninit"
  87                 : "=m" (*&boot_cpu_data.fdiv_bug)
  88                 : "m" (*&x), "m" (*&y));
  89         if (boot_cpu_data.fdiv_bug)
  90                 printk("Hmm, FPU with FDIV bug.\n");
  91 }
  92
  93 static void __init check_hlt(void)
  94 {
  95         printk(KERN_INFO "Checking 'hlt' instruction... ");
  96         if (!boot_cpu_data.hlt_works_ok) {
  97                 printk("disabled\n");
  98                 return;
  99         }
 100         halt();
 101         halt();
 102         halt();
 103         halt();
 104         printk("OK.\n");
 105 }
 106
 107 /*
 108  *      Most 386 processors have a bug where a POPAD can lock the
 109  *      machine even from user space.
 110  */
 111
 112 static void __init check_popad(void)
 113 {
 114 #ifndef CONFIG_X86_POPAD_OK
 115         int res, inp = (int) &res;
 116
 117         printk(KERN_INFO "Checking for popad bug... ");
 118         __asm__ __volatile__(
 119           "movl $12345678,%%eax; movl $0,%%edi; pusha; popa; movl (%%edx,%%edi),%%ecx "
 120           : "=&a" (res)
 121           : "d" (inp)
 122           : "ecx", "edi" );
 123         /* If this fails, it means that any user program may lock the CPU hard. Too bad. */
 124         if (res != 12345678) printk( "Buggy.\n" );
 125                         else printk( "OK.\n" );
 126 #endif
 127 }
 128
 129 /*
 130  * Check whether we are able to run this kernel safely on SMP.
 131  *
 132  * - In order to run on a i386, we need to be compiled for i386
 133  *   (for due to lack of "invlpg" and working WP on a i386)
 134  * - In order to run on anything without a TSC, we need to be
 135  *   compiled for a i486.
 136  * - In order to support the local APIC on a buggy Pentium machine,
 137  *   we need to be compiled with CONFIG_X86_GOOD_APIC disabled,
 138  *   which happens implicitly if compiled for a Pentium or lower
 139  *   (unless an advanced selection of CPU features is used) as an
 140  *   otherwise config implies a properly working local APIC without
 141  *   the need to do extra reads from the APIC.
 142 */
 143
 144 static void __init check_config(void)
 145 {
 146 /*
 147  * We'd better not be a i386 if we're configured to use some
 148  * i486+ only features! (WP works in supervisor mode and the
 149  * new "invlpg" and "bswap" instructions)
 150  */
 151 #if defined(CONFIG_X86_WP_WORKS_OK) || defined(CONFIG_X86_INVLPG) || defined(CONFIG_X86_BSWAP)
 152         if (boot_cpu_data.x86 == 3)
 153                 panic("Kernel requires i486+ for 'invlpg' and other features");
 154 #endif
 155
 156 /*
 157  * If we configured ourselves for a TSC, we'd better have one!
 158  */
 159 #ifdef CONFIG_X86_TSC
 160         if (!cpu_has_tsc)
 161                 panic("Kernel compiled for Pentium+, requires TSC feature!");
 162 #endif
 163
 164 /*
 165  * If we were told we had a good local APIC, check for buggy Pentia,
 166  * i.e. all B steppings and the C2 stepping of P54C when using their
 167  * integrated APIC (see 11AP erratum in "Pentium Processor
 168  * Specification Update").
 169  */
 170 #if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_X86_GOOD_APIC)
 171         if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL
 172             && cpu_has_apic
 173             && boot_cpu_data.x86 == 5
 174             && boot_cpu_data.x86_model == 2
 175             && (boot_cpu_data.x86_mask < 6 || boot_cpu_data.x86_mask == 11))
 176                 panic("Kernel compiled for PMMX+, assumes a local APIC without the read-before-write bug!");
 177 #endif
 178 }
 179
 180 extern void alternative_instructions(void);
 181
 182 static void __init check_bugs(void)
 183 {
 184         identify_cpu(&boot_cpu_data);
 185 #ifndef CONFIG_SMP
 186         printk("CPU: ");
 187         print_cpu_info(&boot_cpu_data);
 188 #endif
 189         check_config();
 190         check_fpu();
 191         check_hlt();
 192         check_popad();
 193         system_utsname.machine[1] = '0' + (boot_cpu_data.x86 > 6 ? 6 : boot_cpu_data.x86);
 194         alternative_instructions();
 195 }