arch/x86/mm/extable.c

   1 #include <linux/module.h>
   2 #include <asm/uaccess.h>
   3 #include <asm/traps.h>
   4
   5 typedef bool (*ex_handler_t)(const struct exception_table_entry *,
   6                             struct pt_regs *, int);
   7
   8 static inline unsigned long
   9 ex_fixup_addr(const struct exception_table_entry *x)
  10 {
  11         return (unsigned long)&x->fixup + x->fixup;
  12 }
  13 static inline ex_handler_t
  14 ex_fixup_handler(const struct exception_table_entry *x)
  15 {
  16         return (ex_handler_t)((unsigned long)&x->handler + x->handler);
  17 }
  18
  19 bool ex_handler_default(const struct exception_table_entry *fixup,
  20                        struct pt_regs *regs, int trapnr)
  21 {
  22         regs->ip = ex_fixup_addr(fixup);
  23         return true;
  24 }
  25 EXPORT_SYMBOL(ex_handler_default);
  26
  27 bool ex_handler_fault(const struct exception_table_entry *fixup,
  28                      struct pt_regs *regs, int trapnr)
  29 {
  30         regs->ip = ex_fixup_addr(fixup);
  31         regs->ax = trapnr;
  32         return true;
  33 }
  34 EXPORT_SYMBOL_GPL(ex_handler_fault);
  35
  36 bool ex_handler_ext(const struct exception_table_entry *fixup,
  37                    struct pt_regs *regs, int trapnr)
  38 {
  39         /* Special hack for uaccess_err */
  40         current_thread_info()->uaccess_err = 1;
  41         regs->ip = ex_fixup_addr(fixup);
  42         return true;
  43 }
  44 EXPORT_SYMBOL(ex_handler_ext);
  45
  46 bool ex_has_fault_handler(unsigned long ip)
  47 {
  48         const struct exception_table_entry *e;
  49         ex_handler_t handler;
  50
  51         e = search_exception_tables(ip);
  52         if (!e)
  53                 return false;
  54         handler = ex_fixup_handler(e);
  55
  56         return handler == ex_handler_fault;
  57 }
  58
  59 int fixup_exception(struct pt_regs *regs, int trapnr)
  60 {
  61         const struct exception_table_entry *e;
  62         ex_handler_t handler;
  63
  64 #ifdef CONFIG_PNPBIOS
  65         if (unlikely(SEGMENT_IS_PNP_CODE(regs->cs))) {
  66                 extern u32 pnp_bios_fault_eip, pnp_bios_fault_esp;
  67                 extern u32 pnp_bios_is_utter_crap;
  68                 pnp_bios_is_utter_crap = 1;
  69                 printk(KERN_CRIT "PNPBIOS fault.. attempting recovery.\n");
  70                 __asm__ volatile(
  71                         "movl %0, %%esp\n\t"
  72                         "jmp *%1\n\t"
  73                         : : "g" (pnp_bios_fault_esp), "g" (pnp_bios_fault_eip));
  74                 panic("do_trap: can't hit this");
  75         }
  76 #endif
  77
  78         e = search_exception_tables(regs->ip);
  79         if (!e)
  80                 return 0;
  81
  82         handler = ex_fixup_handler(e);
  83         return handler(e, regs, trapnr);
  84 }
  85
  86 extern unsigned int early_recursion_flag;
  87
  88 /* Restricted version used during very early boot */
  89 void __init early_fixup_exception(struct pt_regs *regs, int trapnr)
  90 {
  91         const struct exception_table_entry *e;
  92         unsigned long new_ip;
  93         ex_handler_t handler;
  94
  95         /* Ignore early NMIs. */
  96         if (trapnr == X86_TRAP_NMI)
  97                 return;
  98
  99         if (early_recursion_flag > 2)
 100                 goto halt_loop;
 101
 102         if (regs->cs != __KERNEL_CS)
 103                 goto fail;
 104
 105         e = search_exception_tables(regs->ip);
 106         if (!e)
 107                 goto fail;
 108
 109         new_ip  = ex_fixup_addr(e);
 110         handler = ex_fixup_handler(e);
 111
 112         /* special handling not supported during early boot */
 113         if (handler != ex_handler_default)
 114                 goto fail;
 115
 116         regs->ip = new_ip;
 117         return;
 118
 119 fail:
 120         early_printk("PANIC: early exception 0x%02x IP %lx:%lx error %lx cr2 0x%lx\n",
 121                      (unsigned)trapnr, (unsigned long)regs->cs, regs->ip,
 122                      regs->orig_ax, read_cr2());
 123
 124         show_regs(regs);
 125
 126 halt_loop:
 127         while (true)
 128                 halt();
 129 }