arch/mips/kernel/cpu-bugs64.c

   1 /*
   2  * Copyright (C) 2003  Maciej W. Rozycki
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License
   6  * as published by the Free Software Foundation; either version
   7  * 2 of the License, or (at your option) any later version.
   8  */
   9 #include <linux/init.h>
  10 #include <linux/kernel.h>
  11 #include <linux/ptrace.h>
  12 #include <linux/stddef.h>
  13
  14 #include <asm/bugs.h>
  15 #include <asm/cpu.h>
  16 #include <asm/fpu.h>
  17 #include <asm/mipsregs.h>
  18 #include <asm/system.h>
  19
  20 static inline void check_mult_sh(void)
  21 {
  22         unsigned long flags;
  23         int m1, m2;
  24         long p, s, v;
  25
  26         printk("Checking for the multiply/shift bug... ");
  27
  28         local_irq_save(flags);
  29         /*
  30          * The following code leads to a wrong result of dsll32 when
  31          * executed on R4000 rev. 2.2 or 3.0.
  32          *
  33          * See "MIPS R4000PC/SC Errata, Processor Revision 2.2 and
  34          * 3.0" by MIPS Technologies, Inc., errata #16 and #28 for
  35          * details.  I got no permission to duplicate them here,
  36          * sigh... --macro
  37          */
  38         asm volatile(
  39                 ".set   push\n\t"
  40                 ".set   noat\n\t"
  41                 ".set   noreorder\n\t"
  42                 ".set   nomacro\n\t"
  43                 "mult   %1, %2\n\t"
  44                 "dsll32 %0, %3, %4\n\t"
  45                 "mflo   $0\n\t"
  46                 ".set   pop"
  47                 : "=r" (v)
  48                 : "r" (5), "r" (8), "r" (5), "I" (0)
  49                 : "hi", "lo", "accum");
  50         local_irq_restore(flags);
  51
  52         if (v == 5L << 32) {
  53                 printk("no.\n");
  54                 return;
  55         }
  56
  57         printk("yes, workaround... ");
  58         local_irq_save(flags);
  59         /*
  60          * We want the multiply and the shift to be isolated from the
  61          * rest of the code to disable gcc optimizations.  Hence the
  62          * asm statements that execute nothing, but make gcc not know
  63          * what the values of m1, m2 and s are and what v and p are
  64          * used for.
  65          *
  66          * We have to use single integers for m1 and m2 and a double
  67          * one for p to be sure the mulsidi3 gcc's RTL multiplication
  68          * instruction has the workaround applied.  Older versions of
  69          * gcc have correct mulsi3, but other multiplication variants
  70          * lack the workaround.
  71          */
  72         asm volatile(
  73                 ""
  74                 : "=r" (m1), "=r" (m2), "=r" (s)
  75                 : "0" (5), "1" (8), "2" (5));
  76         p = m1 * m2;
  77         v = s << 32;
  78         asm volatile(
  79                 ""
  80                 : "=r" (v)
  81                 : "0" (v), "r" (p));
  82         local_irq_restore(flags);
  83
  84         if (v == 5L << 32) {
  85                 printk("yes.\n");
  86                 return;
  87         }
  88
  89         printk("no.\n");
  90         panic("Reliable operation impossible!\n"
  91 #ifndef CONFIG_CPU_R4000
  92               "Configure for R4000 to enable the workaround."
  93 #else
  94               "Please report to <linux-mips@linux-mips.org>."
  95 #endif
  96               );
  97 }
  98
  99 static volatile int daddi_ov __initdata = 0;
 100
 101 asmlinkage void __init do_daddi_ov(struct pt_regs *regs)
 102 {
 103         daddi_ov = 1;
 104         regs->cp0_epc += 4;
 105 }
 106
 107 static inline void check_daddi(void)
 108 {
 109         extern asmlinkage void handle_daddi_ov(void);
 110         unsigned long flags;
 111         void *handler;
 112         long v;
 113
 114         printk("Checking for the daddi bug... ");
 115
 116         local_irq_save(flags);
 117         handler = set_except_vector(12, handle_daddi_ov);
 118         /*
 119          * The following code fails to trigger an overflow exception
 120          * when executed on R4000 rev. 2.2 or 3.0.
 121          *
 122          * See "MIPS R4000PC/SC Errata, Processor Revision 2.2 and
 123          * 3.0" by MIPS Technologies, Inc., erratum #23 for details.
 124          * I got no permission to duplicate it here, sigh... --macro
 125          */
 126         asm volatile(
 127                 ".set   push\n\t"
 128                 ".set   noat\n\t"
 129                 ".set   noreorder\n\t"
 130                 ".set   nomacro\n\t"
 131 #ifdef HAVE_AS_SET_DADDI
 132                 ".set   daddi\n\t"
 133 #endif
 134                 "daddi  %0, %1, %2\n\t"
 135                 ".set   pop"
 136                 : "=r" (v)
 137                 : "r" (0x7fffffffffffedcd), "I" (0x1234));
 138         set_except_vector(12, handler);
 139         local_irq_restore(flags);
 140
 141         if (daddi_ov) {
 142                 printk("no.\n");
 143                 return;
 144         }
 145
 146         printk("yes, workaround... ");
 147
 148         local_irq_save(flags);
 149         handler = set_except_vector(12, handle_daddi_ov);
 150         asm volatile(
 151                 "daddi  %0, %1, %2"
 152                 : "=r" (v)
 153                 : "r" (0x7fffffffffffedcd), "I" (0x1234));
 154         set_except_vector(12, handler);
 155         local_irq_restore(flags);
 156
 157         if (daddi_ov) {
 158                 printk("yes.\n");
 159                 return;
 160         }
 161
 162         printk("no.\n");
 163         panic("Reliable operation impossible!\n"
 164 #if !defined(CONFIG_CPU_R4000) && !defined(CONFIG_CPU_R4400)
 165               "Configure for R4000 or R4400 to enable the workaround."
 166 #else
 167               "Please report to <linux-mips@linux-mips.org>."
 168 #endif
 169               );
 170 }
 171
 172 static inline void check_daddiu(void)
 173 {
 174         long v, w;
 175
 176         printk("Checking for the daddiu bug... ");
 177
 178         /*
 179          * The following code leads to a wrong result of daddiu when
 180          * executed on R4400 rev. 1.0.
 181          *
 182          * See "MIPS R4400PC/SC Errata, Processor Revision 1.0" by
 183          * MIPS Technologies, Inc., erratum #7 for details.
 184          *
 185          * According to "MIPS R4000PC/SC Errata, Processor Revision
 186          * 2.2 and 3.0" by MIPS Technologies, Inc., erratum #41 this
 187          * problem affects R4000 rev. 2.2 and 3.0, too.  Testing
 188          * failed to trigger it so far.
 189          *
 190          * I got no permission to duplicate the errata here, sigh...
 191          * --macro
 192          */
 193         asm volatile(
 194                 ".set   push\n\t"
 195                 ".set   noat\n\t"
 196                 ".set   noreorder\n\t"
 197                 ".set   nomacro\n\t"
 198 #ifdef HAVE_AS_SET_DADDI
 199                 ".set   daddi\n\t"
 200 #endif
 201                 "daddiu %0, %2, %3\n\t"
 202                 "addiu  %1, $0, %3\n\t"
 203                 "daddu  %1, %2\n\t"
 204                 ".set   pop"
 205                 : "=&r" (v), "=&r" (w)
 206                 : "r" (0x7fffffffffffedcd), "I" (0x1234));
 207
 208         if (v == w) {
 209                 printk("no.\n");
 210                 return;
 211         }
 212
 213         printk("yes, workaround... ");
 214
 215         asm volatile(
 216                 "daddiu %0, %2, %3\n\t"
 217                 "addiu  %1, $0, %3\n\t"
 218                 "daddu  %1, %2"
 219                 : "=&r" (v), "=&r" (w)
 220                 : "r" (0x7fffffffffffedcd), "I" (0x1234));
 221
 222         if (v == w) {
 223                 printk("yes.\n");
 224                 return;
 225         }
 226
 227         printk("no.\n");
 228         panic("Reliable operation impossible!\n"
 229 #if !defined(CONFIG_CPU_R4000) && !defined(CONFIG_CPU_R4400)
 230               "Configure for R4000 or R4400 to enable the workaround."
 231 #else
 232               "Please report to <linux-mips@linux-mips.org>."
 233 #endif
 234               );
 235 }
 236
 237 void __init check_bugs64(void)
 238 {
 239         check_mult_sh();
 240         check_daddi();
 241         check_daddiu();
 242 }