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Filename : uaccess.h
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/*
 * User memory access support for Hexagon
 *
 * Copyright (c) 2010-2011, The Linux Foundation. All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 and
 * only version 2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 */

#ifndef _ASM_UACCESS_H
#define _ASM_UACCESS_H
/*
 * User space memory access functions
 */
#include <linux/sched.h>
#include <linux/mm.h>
#include <asm/segment.h>
#include <asm/sections.h>

/*
 * access_ok: - Checks if a user space pointer is valid
 * @type: Type of access: %VERIFY_READ or %VERIFY_WRITE.  Note that
 *        %VERIFY_WRITE is a superset of %VERIFY_READ - if it is safe
 *        to write to a block, it is always safe to read from it.
 * @addr: User space pointer to start of block to check
 * @size: Size of block to check
 *
 * Context: User context only. This function may sleep if pagefaults are
 *          enabled.
 *
 * Checks if a pointer to a block of memory in user space is valid.
 *
 * Returns true (nonzero) if the memory block *may* be valid, false (zero)
 * if it is definitely invalid.
 *
 * User address space in Hexagon, like x86, goes to 0xbfffffff, so the
 * simple MSB-based tests used by MIPS won't work.  Some further
 * optimization is probably possible here, but for now, keep it
 * reasonably simple and not *too* slow.  After all, we've got the
 * MMU for backup.
 */
#define VERIFY_READ     0
#define VERIFY_WRITE    1

#define __access_ok(addr, size) \
	((get_fs().seg == KERNEL_DS.seg) || \
	(((unsigned long)addr < get_fs().seg) && \
	  (unsigned long)size < (get_fs().seg - (unsigned long)addr)))

/*
 * When a kernel-mode page fault is taken, the faulting instruction
 * address is checked against a table of exception_table_entries.
 * Each entry is a tuple of the address of an instruction that may
 * be authorized to fault, and the address at which execution should
 * be resumed instead of the faulting instruction, so as to effect
 * a workaround.
 */

/*  Assembly somewhat optimized copy routines  */
unsigned long __copy_from_user_hexagon(void *to, const void __user *from,
				     unsigned long n);
unsigned long __copy_to_user_hexagon(void __user *to, const void *from,
				   unsigned long n);

#define __copy_from_user(to, from, n) __copy_from_user_hexagon(to, from, n)
#define __copy_to_user(to, from, n) __copy_to_user_hexagon(to, from, n)

/*
 * XXX todo: some additonal performance gain is possible by
 * implementing __copy_to/from_user_inatomic, which is much
 * like __copy_to/from_user, but performs slightly less checking.
 */

__kernel_size_t __clear_user_hexagon(void __user *dest, unsigned long count);
#define __clear_user(a, s) __clear_user_hexagon((a), (s))

#define __strncpy_from_user(dst, src, n) hexagon_strncpy_from_user(dst, src, n)

/*  get around the ifndef in asm-generic/uaccess.h  */
#define __strnlen_user __strnlen_user

extern long __strnlen_user(const char __user *src, long n);

static inline long hexagon_strncpy_from_user(char *dst, const char __user *src,
					     long n);

#include <asm-generic/uaccess.h>

/*  Todo:  an actual accelerated version of this.  */
static inline long hexagon_strncpy_from_user(char *dst, const char __user *src,
					     long n)
{
	long res = __strnlen_user(src, n);

	if (unlikely(!res))
		return -EFAULT;

	if (res > n) {
		copy_from_user(dst, src, n);
		return n;
	} else {
		copy_from_user(dst, src, res);
		return res-1;
	}
}

#endif