arch/x86/mm/extable.c

   1 #include <linux/module.h>
   2 #include <asm/uaccess.h>
   3
   4 typedef bool (*ex_handler_t)(const struct exception_table_entry *,
   5                             struct pt_regs *, int);
   6
   7 static inline unsigned long
   8 ex_fixup_addr(const struct exception_table_entry *x)
   9 {
  10         return (unsigned long)&x->fixup + x->fixup;
  11 }
  12 static inline ex_handler_t
  13 ex_fixup_handler(const struct exception_table_entry *x)
  14 {
  15         return (ex_handler_t)((unsigned long)&x->handler + x->handler);
  16 }
  17
  18 bool ex_handler_default(const struct exception_table_entry *fixup,
  19                        struct pt_regs *regs, int trapnr)
  20 {
  21         regs->ip = ex_fixup_addr(fixup);
  22         return true;
  23 }
  24 EXPORT_SYMBOL(ex_handler_default);
  25
  26 bool ex_handler_fault(const struct exception_table_entry *fixup,
  27                      struct pt_regs *regs, int trapnr)
  28 {
  29         regs->ip = ex_fixup_addr(fixup);
  30         regs->ax = trapnr;
  31         return true;
  32 }
  33 EXPORT_SYMBOL_GPL(ex_handler_fault);
  34
  35 bool ex_handler_ext(const struct exception_table_entry *fixup,
  36                    struct pt_regs *regs, int trapnr)
  37 {
  38         /* Special hack for uaccess_err */
  39         current_thread_info()->uaccess_err = 1;
  40         regs->ip = ex_fixup_addr(fixup);
  41         return true;
  42 }
  43 EXPORT_SYMBOL(ex_handler_ext);
  44
  45 bool ex_has_fault_handler(unsigned long ip)
  46 {
  47         const struct exception_table_entry *e;
  48         ex_handler_t handler;
  49
  50         e = search_exception_tables(ip);
  51         if (!e)
  52                 return false;
  53         handler = ex_fixup_handler(e);
  54
  55         return handler == ex_handler_fault;
  56 }
  57
  58 int fixup_exception(struct pt_regs *regs, int trapnr)
  59 {
  60         const struct exception_table_entry *e;
  61         ex_handler_t handler;
  62
  63 #ifdef CONFIG_PNPBIOS
  64         if (unlikely(SEGMENT_IS_PNP_CODE(regs->cs))) {
  65                 extern u32 pnp_bios_fault_eip, pnp_bios_fault_esp;
  66                 extern u32 pnp_bios_is_utter_crap;
  67                 pnp_bios_is_utter_crap = 1;
  68                 printk(KERN_CRIT "PNPBIOS fault.. attempting recovery.\n");
  69                 __asm__ volatile(
  70                         "movl %0, %%esp\n\t"
  71                         "jmp *%1\n\t"
  72                         : : "g" (pnp_bios_fault_esp), "g" (pnp_bios_fault_eip));
  73                 panic("do_trap: can't hit this");
  74         }
  75 #endif
  76
  77         e = search_exception_tables(regs->ip);
  78         if (!e)
  79                 return 0;
  80
  81         handler = ex_fixup_handler(e);
  82         return handler(e, regs, trapnr);
  83 }
  84
  85 /* Restricted version used during very early boot */
  86 int __init early_fixup_exception(unsigned long *ip)
  87 {
  88         const struct exception_table_entry *e;
  89         unsigned long new_ip;
  90         ex_handler_t handler;
  91
  92         e = search_exception_tables(*ip);
  93         if (!e)
  94                 return 0;
  95
  96         new_ip  = ex_fixup_addr(e);
  97         handler = ex_fixup_handler(e);
  98
  99         /* special handling not supported during early boot */
 100         if (handler != ex_handler_default)
 101                 return 0;
 102
 103         *ip = new_ip;
 104         return 1;
 105 }