extable.c

来自「Linux Kernel 2.6.9 for OMAP1710」· C语言 代码 · 共 81 行

/*
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * arch/sh64/mm/extable.c
 *
 * Copyright (C) 2003 Richard Curnow
 * Copyright (C) 2003, 2004  Paul Mundt
 *
 * Cloned from the 2.5 SH version..
 */
#include <linux/config.h>
#include <linux/rwsem.h>
#include <linux/module.h>
#include <asm/uaccess.h>

extern unsigned long copy_user_memcpy, copy_user_memcpy_end, __copy_user_fixup;

static const struct exception_table_entry __copy_user_fixup_ex = {
	.fixup = (unsigned long)&__copy_user_fixup,
};

/* Some functions that may trap due to a bad user-mode address have too many loads
   and stores in them to make it at all practical to label each one and put them all in
   the main exception table.

   In particular, the fast memcpy routine is like this.  It's fix-up is just to fall back
   to a slow byte-at-a-time copy, which is handled the conventional way.  So it's functionally
   OK to just handle any trap occurring in the fast memcpy with that fixup. */
static const struct exception_table_entry *check_exception_ranges(unsigned long addr)
{
	if ((addr >= (unsigned long)&copy_user_memcpy) &&
	    (addr <= (unsigned long)&copy_user_memcpy_end))
		return &__copy_user_fixup_ex;

	return NULL;
}

/* Simple binary search */
const struct exception_table_entry *
search_extable(const struct exception_table_entry *first,
		 const struct exception_table_entry *last,
		 unsigned long value)
{
	const struct exception_table_entry *mid;

	mid = check_exception_ranges(value);
	if (mid)
		return mid;

        while (first <= last) {
		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;
}

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

	fixup = search_exception_tables(regs->pc);
	if (fixup) {
		regs->pc = fixup->fixup;
		return 1;
	}

	return 0;
}