root/lib/extable.c

DEFINITIONS

1. cmp_ex
2. sort_extable
3. search_extable

/*
 * Derived from arch/ppc/mm/extable.c and arch/i386/mm/extable.c.
 *
 * Copyright (C) 2004 Paul Mackerras, IBM Corp.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/sort.h>
#include <asm/uaccess.h>

#ifndef ARCH_HAS_SORT_EXTABLE
/*
 * The exception table needs to be sorted so that the binary
 * search that we use to find entries in it works properly.
 * This is used both for the kernel exception table and for
 * the exception tables of modules that get loaded.
 */
static int cmp_ex(const void *a, const void *b)
{
        const struct exception_table_entry *x = a, *y = b;

        /* avoid overflow */
        if (x->insn > y->insn)
                return 1;
        if (x->insn < y->insn)
                return -1;
        return 0;
}

void sort_extable(struct exception_table_entry *start,
                  struct exception_table_entry *finish)
{
        sort(start, finish - start, sizeof(struct exception_table_entry),
             cmp_ex, NULL);
}
#endif

#ifndef ARCH_HAS_SEARCH_EXTABLE
/*
 * Search one exception table for an entry corresponding to the
 * given instruction address, and return the address of the entry,
 * or NULL if none is found.
 * We use a binary search, and thus we assume that the table is
 * already sorted.
 */
const struct exception_table_entry *
search_extable(const struct exception_table_entry *first,
               const struct exception_table_entry *last,
               unsigned long value)
{
        while (first <= last) {
                const struct exception_table_entry *mid;

                mid = ((last - first) >> 1) + first;
                /*
                 * careful, the distance between value and insn
                 * can be larger than MAX_LONG:
                 */
                if (mid->insn < value)
                        first = mid + 1;
                else if (mid->insn > value)
                        last = mid - 1;
                else
                        return mid;
        }
        return NULL;
}
#endif