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  *  Pentium III FXSR, SSE support
  13  *      Gareth Hughes <gareth@valinux.com>, May 2000
  14  */
  15
  16 /*
  17  * This is included by init/main.c to check for architecture-dependent bugs.
  18  *
  19  * Needs:
  20  *      void check_bugs(void);
  21  */
  22
  23 #include <linux/config.h>
  24 #include <asm/processor.h>
  25 #include <asm/i387.h>
  26 #include <asm/msr.h>
  27
  28 static int __init no_halt(char *s)
  29 {
  30         boot_cpu_data.hlt_works_ok = 0;
  31         return 1;
  32 }
  33
  34 __setup("no-hlt", no_halt);
  35
  36 static int __init mca_pentium(char *s)
  37 {
  38         mca_pentium_flag = 1;
  39         return 1;
  40 }
  41
  42 __setup("mca-pentium", mca_pentium);
  43
  44 static int __init no_387(char *s)
  45 {
  46         boot_cpu_data.hard_math = 0;
  47         write_cr0(0xE | read_cr0());
  48         return 1;
  49 }
  50
  51 __setup("no387", no_387);
  52
  53 static double __initdata x = 4195835.0;
  54 static double __initdata y = 3145727.0;
  55
  56 /*
  57  * This used to check for exceptions..
  58  * However, it turns out that to support that,
  59  * the XMM trap handlers basically had to
  60  * be buggy. So let's have a correct XMM trap
  61  * handler, and forget about printing out
  62  * some status at boot.
  63  *
  64  * We should really only care about bugs here
  65  * anyway. Not features.
  66  */
  67 static void __init check_fpu(void)
  68 {
  69         if (!boot_cpu_data.hard_math) {
  70 #ifndef CONFIG_MATH_EMULATION
  71                 printk(KERN_EMERG "No coprocessor found and no math emulation present.\n");
  72                 printk(KERN_EMERG "Giving up.\n");
  73                 for (;;) ;
  74 #endif
  75                 return;
  76         }
  77
  78 /* Enable FXSR and company _before_ testing for FP problems. */
  79 #if defined(CONFIG_X86_FXSR) || defined(CONFIG_X86_RUNTIME_FXSR)
  80         /*
  81          * Verify that the FXSAVE/FXRSTOR data will be 16-byte aligned.
  82          */
  83         if (offsetof(struct task_struct, thread.i387.fxsave) & 15)
  84                 panic("Kernel compiled for PII/PIII+ with FXSR, data not 16-byte aligned!");
  85
  86         if (cpu_has_fxsr) {
  87                 printk(KERN_INFO "Enabling fast FPU save and restore... ");
  88                 set_in_cr4(X86_CR4_OSFXSR);
  89                 printk("done.\n");
  90         }
  91 #endif
  92 #ifdef CONFIG_X86_XMM
  93         if (cpu_has_xmm) {
  94                 printk(KERN_INFO "Enabling unmasked SIMD FPU exception support... ");
  95                 set_in_cr4(X86_CR4_OSXMMEXCPT);
  96                 printk("done.\n");
  97         }
  98 #endif
  99
 100         /* Test for the divl bug.. */
 101         __asm__("fninit\n\t"
 102                 "fldl %1\n\t"
 103                 "fdivl %2\n\t"
 104                 "fmull %2\n\t"
 105                 "fldl %1\n\t"
 106                 "fsubp %%st,%%st(1)\n\t"
 107                 "fistpl %0\n\t"
 108                 "fwait\n\t"
 109                 "fninit"
 110                 : "=m" (*&boot_cpu_data.fdiv_bug)
 111                 : "m" (*&x), "m" (*&y));
 112         if (boot_cpu_data.fdiv_bug)
 113                 printk("Hmm, FPU with FDIV bug.\n");
 114 }
 115
 116 static void __init check_hlt(void)
 117 {
 118         printk(KERN_INFO "Checking 'hlt' instruction... ");
 119         if (!boot_cpu_data.hlt_works_ok) {
 120                 printk("disabled\n");
 121                 return;
 122         }
 123         __asm__ __volatile__("hlt ; hlt ; hlt ; hlt");
 124         printk("OK.\n");
 125 }
 126
 127 /*
 128  *      Most 386 processors have a bug where a POPAD can lock the
 129  *      machine even from user space.
 130  */
 131
 132 static void __init check_popad(void)
 133 {
 134 #ifndef CONFIG_X86_POPAD_OK
 135         int res, inp = (int) &res;
 136
 137         printk(KERN_INFO "Checking for popad bug... ");
 138         __asm__ __volatile__(
 139           "movl $12345678,%%eax; movl $0,%%edi; pusha; popa; movl (%%edx,%%edi),%%ecx "
 140           : "=&a" (res)
 141           : "d" (inp)
 142           : "ecx", "edi" );
 143         /* If this fails, it means that any user program may lock the CPU hard. Too bad. */
 144         if (res != 12345678) printk( "Buggy.\n" );
 145                         else printk( "OK.\n" );
 146 #endif
 147 }
 148
 149 /*
 150  * Check whether we are able to run this kernel safely on SMP.
 151  *
 152  * - In order to run on a i386, we need to be compiled for i386
 153  *   (for due to lack of "invlpg" and working WP on a i386)
 154  * - In order to run on anything without a TSC, we need to be
 155  *   compiled for a i486.
 156  * - In order to support the local APIC on a buggy Pentium machine,
 157  *   we need to be compiled with CONFIG_X86_GOOD_APIC disabled,
 158  *   which happens implicitly if compiled for a Pentium or lower
 159  *   (unless an advanced selection of CPU features is used) as an
 160  *   otherwise config implies a properly working local APIC without
 161  *   the need to do extra reads from the APIC.
 162 */
 163
 164 static void __init check_config(void)
 165 {
 166 /*
 167  * We'd better not be a i386 if we're configured to use some
 168  * i486+ only features! (WP works in supervisor mode and the
 169  * new "invlpg" and "bswap" instructions)
 170  */
 171 #if defined(CONFIG_X86_WP_WORKS_OK) || defined(CONFIG_X86_INVLPG) || defined(CONFIG_X86_BSWAP)
 172         if (boot_cpu_data.x86 == 3)
 173                 panic("Kernel requires i486+ for 'invlpg' and other features");
 174 #endif
 175
 176 /*
 177  * If we configured ourselves for a TSC, we'd better have one!
 178  */
 179 #ifdef CONFIG_X86_TSC
 180         if (!cpu_has_tsc)
 181                 panic("Kernel compiled for Pentium+, requires TSC feature!");
 182 #endif
 183
 184 /*
 185  * If we configured ourselves for PGE, we'd better have it.
 186  */
 187 #ifdef CONFIG_X86_PGE
 188         if (!cpu_has_pge)
 189                 panic("Kernel compiled for PPro+, requires PGE feature!");
 190 #endif
 191
 192 /*
 193  * If we were told we had a good local APIC, check for buggy Pentia,
 194  * i.e. all B steppings and the C2 stepping of P54C when using their
 195  * integrated APIC (see 11AP erratum in "Pentium Processor
 196  * Specification Update").
 197  */
 198 #if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_X86_GOOD_APIC)
 199         if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL
 200             && test_bit(X86_FEATURE_APIC, &boot_cpu_data.x86_capability)
 201             && boot_cpu_data.x86 == 5
 202             && boot_cpu_data.x86_model == 2
 203             && (boot_cpu_data.x86_mask < 6 || boot_cpu_data.x86_mask == 11))
 204                 panic("Kernel compiled for PMMX+, assumes a local APIC without the read-before-write bug!");
 205 #endif
 206
 207 /*
 208  * If we configured ourselves for FXSR, we'd better have it.
 209  */
 210 #ifdef CONFIG_X86_FXSR
 211         if (!cpu_has_fxsr)
 212                 panic("Kernel compiled for PII/PIII+, requires FXSR feature!");
 213 #endif
 214 }
 215
 216 static void __init check_bugs(void)
 217 {
 218         identify_cpu(&boot_cpu_data);
 219 #ifndef CONFIG_SMP
 220         printk("CPU: ");
 221         print_cpu_info(&boot_cpu_data);
 222 #endif
 223         check_config();
 224         check_fpu();
 225         check_hlt();
 226         check_popad();
 227         system_utsname.machine[1] = '0' + (boot_cpu_data.x86 > 6 ? 6 : boot_cpu_data.x86);
 228 }