extable.c

#include <linux/module.h>
#include <linux/spinlock.h>
#include <asm/uaccess.h>


int fixup_exception(struct pt_regs *regs)
{
	const struct exception_table_entry *fixup;

#ifdef CONFIG_PNPBIOS
	if (unlikely(SEGMENT_IS_PNP_CODE(regs->cs))) {
		extern u32 pnp_bios_fault_eip, pnp_bios_fault_esp;
		extern u32 pnp_bios_is_utter_crap;
		pnp_bios_is_utter_crap = 1;
		printk(KERN_CRIT "PNPBIOS fault.. attempting recovery.\n");
		__asm__ volatile(
			"movl %0, %%esp\n\t"
			"jmp *%1\n\t"
			: : "g" (pnp_bios_fault_esp), "g" (pnp_bios_fault_eip));
		panic("do_trap: can't hit this");
	}
#endif

	fixup = search_exception_tables(regs->ip);
	if (fixup) {
		/* If fixup is less than 16, it means uaccess error */
		if (fixup->fixup < 16) {
			current_thread_info()->uaccess_err = -EFAULT;
			regs->ip += fixup->fixup;
			return 1;
		}
		regs->ip = fixup->fixup;
		return 1;
	}

	return 0;
}

#ifdef CONFIG_X86_64
/*
 * Need to defined our own search_extable on X86_64 to work around
 * a B stepping K8 bug.
 */
const struct exception_table_entry *
search_extable(const struct exception_table_entry *first,
	       const struct exception_table_entry *last,
	       unsigned long value)
{
	/* B stepping K8 bug */
	if ((value >> 32) == 0)
		value |= 0xffffffffUL << 32;

	while (first <= last) {
		const struct exception_table_entry *mid;
		long diff;

		mid = (last - first) / 2 + first;
		diff = mid->insn - value;
		if (diff == 0)
			return mid;
		else if (diff < 0)
			first = mid+1;
		else
			last = mid-1;
	}
	return NULL;
}
#endif