extable.c

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/*
 * Kernel exception handling table support.  Derived from arch/alpha/mm/extable.c.
 *
 * Copyright (C) 1998, 1999 Hewlett-Packard Co
 * Copyright (C) 1998, 1999 David Mosberger-Tang <[e-mail]>
 */

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

extern const struct exception_table_entry __start___ex_table[];
extern const struct exception_table_entry __stop___ex_table[];

static inline const struct exception_table_entry *
search_one_table (const struct exception_table_entry *first,
		  const struct exception_table_entry *last,
		  signed long value)
{
	/* Abort early if the search value is out of range.  */
	if (value != (signed int)value)
		return 0;

        while (first <= last) {
		const struct exception_table_entry *mid;
		long diff;
		/*
		 * We know that first and last are both kernel virtual
		 * pointers (region 7) so first+last will cause an
		 * overflow.  We fix that by calling __va() on the
		 * result, which will ensure that the top two bits get
		 * set again.
		 */
		mid = (void *) __va((((__u64) first + (__u64) last)/2/sizeof(*mid))*sizeof(*mid));
		diff = mid->addr - value;
                if (diff == 0)
                        return mid;
                else if (diff < 0)
                        first = mid+1;
                else
                        last = mid-1;
        }
        return 0;
}

register unsigned long gp __asm__("gp");

const struct exception_table_entry *
search_exception_table (unsigned long addr)
{
#ifndef CONFIG_MODULE
	/* There is only the kernel to search.  */
	return search_one_table(__start___ex_table, __stop___ex_table - 1, addr - gp);
#else
	struct exception_table_entry *ret;
	/* The kernel is the last "module" -- no need to treat it special. */
	struct module *mp;

	for (mp = module_list; mp ; mp = mp->next) {
		if (!mp->ex_table_start)
			continue;
		ret = search_one_table(mp->ex_table_start, mp->ex_table_end - 1, addr - mp->gp);
		if (ret)
			return ret;
	}
	return 0;
#endif
}