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* 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>
* 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);
* If the exception table is sorted, any referring to the module init
* will be at the beginning or the end.
void trim_init_extable(struct module *m)
/*trim the beginning*/
while (m->num_exentries && within_module_init(m->extable[0].insn, m)) {
/*trim the end*/
while (m->num_exentries &&
within_module_init(m->extable[m->num_exentries-1].insn, m))
#endif /* CONFIG_MODULES */
* 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;
return mid;
return NULL;
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