uaccess.h

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/* 
 * Authors:    Bjorn Wesen ([e-mail])
 *	       Hans-Peter Nilsson ([e-mail])
 *
 * $Log: uaccess.h,v $
 * Revision 1.8  2001/10/29 13:01:48  bjornw
 * Removed unused variable tmp2 in strnlen_user
 *
 * Revision 1.7  2001/10/02 12:44:52  hp
 * Add support for 64-bit put_user/get_user
 *
 * Revision 1.6  2001/10/01 14:51:17  bjornw
 * Added register prefixes and removed underscores
 *
 * Revision 1.5  2000/10/25 03:33:21  hp
 * - Provide implementation for everything else but get_user and put_user;
 *   copying inline to/from user for constant length 0..16, 20, 24, and
 *   clearing for 0..4, 8, 12, 16, 20, 24, strncpy_from_user and strnlen_user
 *   always inline.
 * - Constraints for destination addr in get_user cannot be memory, only reg.
 * - Correct labels for PC at expected fault points.
 * - Nits with assembly code.
 * - Don't use statement expressions without value; use "do {} while (0)".
 * - Return correct values from __generic_... functions.
 *
 * Revision 1.4  2000/09/12 16:28:25  bjornw
 * * Removed comments from the get/put user asm code
 * * Constrains for destination addr in put_user cannot be memory, only reg
 *
 * Revision 1.3  2000/09/12 14:30:20  bjornw
 * MAX_ADDR_USER does not exist anymore
 *
 * Revision 1.2  2000/07/13 15:52:48  bjornw
 * New user-access functions
 *
 * Revision 1.1.1.1  2000/07/10 16:32:31  bjornw
 * CRIS architecture, working draft
 *
 *
 *
 */

/* Asm:s have been tweaked (within the domain of correctness) to give
   satisfactory results for "gcc version 2.96 20000427 (experimental)".

   Check regularly...

   Register $r9 is chosen for temporaries, being a call-clobbered register
   first in line to be used (notably for local blocks), not colliding with
   parameter registers.  */

#ifndef _CRIS_UACCESS_H
#define _CRIS_UACCESS_H

#ifndef __ASSEMBLY__
#include <linux/sched.h>
#include <linux/errno.h>
#include <asm/processor.h>
#include <asm/page.h>

#define VERIFY_READ	0
#define VERIFY_WRITE	1

/*
 * The fs value determines whether argument validity checking should be
 * performed or not.  If get_fs() == USER_DS, checking is performed, with
 * get_fs() == KERNEL_DS, checking is bypassed.
 *
 * For historical reasons, these macros are grossly misnamed.
 */

#define MAKE_MM_SEG(s)	((mm_segment_t) { (s) })

/* addr_limit is the maximum accessible address for the task. we misuse
 * the KERNEL_DS and USER_DS values to both assign and compare the 
 * addr_limit values through the equally misnamed get/set_fs macros.
 * (see above)
 */

#define KERNEL_DS	MAKE_MM_SEG(0xFFFFFFFF)
#define USER_DS		MAKE_MM_SEG(TASK_SIZE)

#define get_ds()	(KERNEL_DS)
#define get_fs()	(current->addr_limit)
#define set_fs(x)	(current->addr_limit = (x))

#define segment_eq(a,b)	((a).seg == (b).seg)

#define __kernel_ok (segment_eq(get_fs(), KERNEL_DS))
#define __user_ok(addr,size) (((size) <= TASK_SIZE)&&((addr) <= TASK_SIZE-(size)))
#define __access_ok(addr,size) (__kernel_ok || __user_ok((addr),(size)))
#define access_ok(type,addr,size) __access_ok((unsigned long)(addr),(size))

extern inline int verify_area(int type, const void * addr, unsigned long size)
{
	return access_ok(type,addr,size) ? 0 : -EFAULT;
}


/*
 * The exception table consists of pairs of addresses: the first is the
 * address of an instruction that is allowed to fault, and the second is
 * the address at which the program should continue.  No registers are
 * modified, so it is entirely up to the continuation code to figure out
 * what to do.
 *
 * All the routines below use bits of fixup code that are out of line
 * with the main instruction path.  This means when everything is well,
 * we don't even have to jump over them.  Further, they do not intrude
 * on our cache or tlb entries.
 */

struct exception_table_entry
{
	unsigned long insn, fixup;
};

/* Returns 0 if exception not found and fixup otherwise.  */
extern unsigned long search_exception_table(unsigned long);


/*
 * These are the main single-value transfer routines.  They automatically
 * use the right size if we just have the right pointer type.
 *
 * This gets kind of ugly. We want to return _two_ values in "get_user()"
 * and yet we don't want to do any pointers, because that is too much
 * of a performance impact. Thus we have a few rather ugly macros here,
 * and hide all the uglyness from the user.
 *
 * The "__xxx" versions of the user access functions are versions that
 * do not verify the address space, that must have been done previously
 * with a separate "access_ok()" call (this is used when we do multiple
 * accesses to the same area of user memory).
 *
 * As we use the same address space for kernel and user data on
 * CRIS, we can just do these as direct assignments.  (Of course, the
 * exception handling means that it's no longer "just"...)
 */
#define get_user(x,ptr) \
  __get_user_check((x),(ptr),sizeof(*(ptr)))
#define put_user(x,ptr) \
  __put_user_check((__typeof__(*(ptr)))(x),(ptr),sizeof(*(ptr)))

#define __get_user(x,ptr) \
  __get_user_nocheck((x),(ptr),sizeof(*(ptr)))
#define __put_user(x,ptr) \
  __put_user_nocheck((__typeof__(*(ptr)))(x),(ptr),sizeof(*(ptr)))

/*
 * The "xxx_ret" versions return constant specified in third argument, if
 * something bad happens. These macros can be optimized for the
 * case of just returning from the function xxx_ret is used.
 */

#define put_user_ret(x,ptr,ret) \
	do { if (put_user(x,ptr)) return ret; } while (0)

#define get_user_ret(x,ptr,ret) \
	do { if (get_user(x,ptr)) return ret; } while (0)

#define __put_user_ret(x,ptr,ret) \
	do { if (__put_user(x,ptr)) return ret; } while (0)

#define __get_user_ret(x,ptr,ret) \
	do { if (__get_user(x,ptr)) return ret; } while (0)


extern long __put_user_bad(void);

#define __put_user_nocheck(x,ptr,size)			\
({							\
	long __pu_err;					\
	__put_user_size((x),(ptr),(size),__pu_err);	\
	__pu_err;					\
})

#define __put_user_check(x,ptr,size)				\
({								\
	long __pu_err = -EFAULT;				\
	__typeof__(*(ptr)) *__pu_addr = (ptr);			\
	if (access_ok(VERIFY_WRITE,__pu_addr,size))		\
		__put_user_size((x),__pu_addr,(size),__pu_err);	\
	__pu_err;						\
})

#define __put_user_size(x,ptr,size,retval)			\
do {								\
	retval = 0;						\
	switch (size) {						\
	  case 1: __put_user_asm(x,ptr,retval,"move.b"); break;	\
	  case 2: __put_user_asm(x,ptr,retval,"move.w"); break;	\
	  case 4: __put_user_asm(x,ptr,retval,"move.d"); break;	\
	  case 8: __put_user_asm_64(x,ptr,retval); break;	\
	  default: __put_user_bad();				\
	}							\
} while (0)

struct __large_struct { unsigned long buf[100]; };
#define __m(x) (*(struct __large_struct *)(x))

/*
 * We don't tell gcc that we are accessing memory, but this is OK
 * because we do not write to any memory gcc knows about, so there
 * are no aliasing issues.
 *
 * Note that PC at a fault is the address *after* the faulting
 * instruction.
 */
#define __put_user_asm(x, addr, err, op)			\
	__asm__ __volatile__(					\
		"	"op" %1,[%2]\n"				\
		"2:\n"						\
		"	.section .fixup,\"ax\"\n"		\
		"3:	move.d %3,%0\n"				\
		"	jump 2b\n"				\
		"	.previous\n"				\
		"	.section __ex_table,\"a\"\n"		\
		"	.dword 2b,3b\n"				\
		"	.previous\n"				\
		: "=r" (err)					\
		: "r" (x), "r" (addr), "g" (-EFAULT), "0" (err))

#define __put_user_asm_64(x, addr, err)				\
	__asm__ __volatile__(					\
		"	move.d %M1,[%2]\n"			\
		"2:	move.d %H1,[%2+4]\n"			\
		"4:\n"						\
		"	.section .fixup,\"ax\"\n"		\
		"3:	move.d %3,%0\n"				\
		"	jump 4b\n"				\
		"	.previous\n"				\
		"	.section __ex_table,\"a\"\n"		\
		"	.dword 2b,3b\n"				\
		"	.dword 4b,3b\n"				\
		"	.previous\n"				\
		: "=r" (err)					\
		: "r" (x), "r" (addr), "g" (-EFAULT), "0" (err))


#define __get_user_nocheck(x,ptr,size)				\
({								\
	long __gu_err, __gu_val;				\
	__get_user_size(__gu_val,(ptr),(size),__gu_err);	\
	(x) = (__typeof__(*(ptr)))__gu_val;			\
	__gu_err;						\
})

#define __get_user_check(x,ptr,size)					\
({									\
	long __gu_err = -EFAULT, __gu_val = 0;				\
	const __typeof__(*(ptr)) *__gu_addr = (ptr);			\
	if (access_ok(VERIFY_READ,__gu_addr,size))			\
		__get_user_size(__gu_val,__gu_addr,(size),__gu_err);	\
	(x) = (__typeof__(*(ptr)))__gu_val;				\
	__gu_err;							\
})

extern long __get_user_bad(void);

#define __get_user_size(x,ptr,size,retval)			\
do {								\
	retval = 0;						\
	switch (size) {						\
	  case 1: __get_user_asm(x,ptr,retval,"move.b"); break;	\
	  case 2: __get_user_asm(x,ptr,retval,"move.w"); break;	\
	  case 4: __get_user_asm(x,ptr,retval,"move.d"); break;	\
	  case 8: __get_user_asm_64(x,ptr,retval); break;	\
	  default: (x) = __get_user_bad();			\
	}							\
} while (0)

/* See comment before __put_user_asm.  */

#define __get_user_asm(x, addr, err, op)		\
	__asm__ __volatile__(				\
		"	"op" [%2],%1\n"			\
		"2:\n"					\
		"	.section .fixup,\"ax\"\n"	\
		"3:	move.d %3,%0\n"			\
		"	moveq 0,%1\n"			\
		"	jump 2b\n"			\
		"	.previous\n"			\
		"	.section __ex_table,\"a\"\n"	\
		"	.dword 2b,3b\n"			\
		"	.previous\n"			\
		: "=r" (err), "=r" (x)			\
		: "r" (addr), "g" (-EFAULT), "0" (err))

#define __get_user_asm_64(x, addr, err)			\
	__asm__ __volatile__(				\
		"	move.d [%2],%M1\n"		\
		"2:	move.d [%2+4],%H1\n"		\
		"4:\n"					\
		"	.section .fixup,\"ax\"\n"	\
		"3:	move.d %3,%0\n"			\
		"	moveq 0,%1\n"			\
		"	jump 4b\n"			\
		"	.previous\n"			\
		"	.section __ex_table,\"a\"\n"	\
		"	.dword 2b,3b\n"			\
		"	.dword 4b,3b\n"			\
		"	.previous\n"			\
		: "=r" (err), "=r" (x)			\
		: "r" (addr), "g" (-EFAULT), "0" (err))

/* More complex functions.  Most are inline, but some call functions that
   live in lib/usercopy.c  */

extern unsigned long __copy_user(void *to, const void *from, unsigned long n);
extern unsigned long __copy_user_zeroing(void *to, const void *from, unsigned long n);
extern unsigned long __do_clear_user(void *to, unsigned long n);

/*
 * Copy a null terminated string from userspace.
 *
 * Must return:
 * -EFAULT		for an exception
 * count		if we hit the buffer limit
 * bytes copied		if we hit a null byte
 * (without the null byte)
 */

static inline long         
__do_strncpy_from_user(char *dst, const char *src, long count)
{
	long res;

	if (count == 0)
		return 0;

	/*
	 * Currently, in 2.4.0-test9, most ports use a simple byte-copy loop.
	 *  So do we.
	 *
	 *  This code is deduced from:
	 *
	 *	char tmp2;
	 *	long tmp1, tmp3	
	 *	tmp1 = count;
	 *	while ((*dst++ = (tmp2 = *src++)) != 0
	 *	       && --tmp1)
	 *	  ;
	 *
	 *	res = count - tmp1;
	 *
	 *  with tweaks.
	 */

	__asm__ __volatile__ (
		"	move.d %3,%0\n"
		"	move.b [%2+],$r9\n"
		"1:	beq 2f\n"
		"	move.b $r9,[%1+]\n"

		"	subq 1,%0\n"
		"	bne 1b\n"
		"	move.b [%2+],$r9\n"

		"2:	sub.d %3,%0\n"
		"	neg.d %0,%0\n"
		"3:\n"
		"	.section .fixup,\"ax\"\n"
		"4:	move.d %7,%0\n"
		"	jump 3b\n"

		/* There's one address for a fault at the first move, and
		   two possible PC values for a fault at the second move,
		   being a delay-slot filler.  However, the branch-target
		   for the second move is the same as the first address.
		   Just so you don't get confused...  */
		"	.previous\n"
		"	.section __ex_table,\"a\"\n"
		"	.dword 1b,4b\n"