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   1 #include <linux/module.h>
   2 #include <linux/spinlock.h>
   3 #include <asm/uaccess.h>
   4
   5
   6 int fixup_exception(struct pt_regs *regs)
   7 {
   8         const struct exception_table_entry *fixup;
   9
  10 #ifdef CONFIG_PNPBIOS
  11         if (unlikely(SEGMENT_IS_PNP_CODE(regs->cs))) {
  12                 extern u32 pnp_bios_fault_eip, pnp_bios_fault_esp;
  13                 extern u32 pnp_bios_is_utter_crap;
  14                 pnp_bios_is_utter_crap = 1;
  15                 printk(KERN_CRIT "PNPBIOS fault.. attempting recovery.\n");
  16                 __asm__ volatile(
  17                         "movl %0, %%esp\n\t"
  18                         "jmp *%1\n\t"
  19                         : : "g" (pnp_bios_fault_esp), "g" (pnp_bios_fault_eip));
  20                 panic("do_trap: can't hit this");
  21         }
  22 #endif
  23
  24         fixup = search_exception_tables(regs->ip);
  25         if (fixup) {
  26                 /* If fixup is less than 16, it means uaccess error */
  27                 if (fixup->fixup < 16) {
  28                         current_thread_info()->uaccess_err = -EFAULT;
  29                         regs->ip += fixup->fixup;
  30                         return 1;
  31                 }
  32                 regs->ip = fixup->fixup;
  33                 return 1;
  34         }
  35
  36         return 0;
  37 }
  38
  39 #ifdef CONFIG_X86_64
  40 /*
  41  * Need to defined our own search_extable on X86_64 to work around
  42  * a B stepping K8 bug.
  43  */
  44 const struct exception_table_entry *
  45 search_extable(const struct exception_table_entry *first,
  46                const struct exception_table_entry *last,
  47                unsigned long value)
  48 {
  49         /* B stepping K8 bug */
  50         if ((value >> 32) == 0)
  51                 value |= 0xffffffffUL << 32;
  52
  53         while (first <= last) {
  54                 const struct exception_table_entry *mid;
  55                 long diff;
  56
  57                 mid = (last - first) / 2 + first;
  58                 diff = mid->insn - value;
  59                 if (diff == 0)
  60                         return mid;
  61                 else if (diff < 0)
  62                         first = mid+1;
  63                 else
  64                         last = mid-1;
  65         }
  66         return NULL;
  67 }
  68 #endif