arch/s390/lib/uaccess_pt.c - linux - Git at Google

 /*
  *  User access functions based on page table walks for enhanced
  *  system layout without hardware support.
  *
  *    Copyright IBM Corp. 2006, 2012
  *    Author(s): Gerald Schaefer (gerald.schaefer@de.ibm.com)
  */

 #include <linux/errno.h>
 #include <linux/hardirq.h>
 #include <linux/mm.h>
 #include <linux/hugetlb.h>
 #include <asm/uaccess.h>
 #include <asm/futex.h>
 #include "uaccess.h"


 /*
  * Returns kernel address for user virtual address. If the returned address is
  * >= -4095 (IS_ERR_VALUE(x) returns true), a fault has occured and the address
  * contains the (negative) exception code.
  */
 static __always_inline unsigned long follow_table(struct mm_struct *mm,
 						  unsigned long addr, int write)
 {
 	pgd_t *pgd;
 	pud_t *pud;
 	pmd_t *pmd;
 	pte_t *ptep;

 	pgd = pgd_offset(mm, addr);
 	if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
 		return -0x3aUL;

 	pud = pud_offset(pgd, addr);
 	if (pud_none(*pud) || unlikely(pud_bad(*pud)))
 		return -0x3bUL;

 	pmd = pmd_offset(pud, addr);
 	if (pmd_none(*pmd))
 		return -0x10UL;
 	if (pmd_huge(*pmd)) {
 		if (write && (pmd_val(*pmd) & _SEGMENT_ENTRY_RO))
 			return -0x04UL;
 		return (pmd_val(*pmd) & HPAGE_MASK) + (addr & ~HPAGE_MASK);
 	}
 	if (unlikely(pmd_bad(*pmd)))
 		return -0x10UL;

 	ptep = pte_offset_map(pmd, addr);
 	if (!pte_present(*ptep))
 		return -0x11UL;
 	if (write && !pte_write(*ptep))
 		return -0x04UL;

 	return (pte_val(*ptep) & PAGE_MASK) + (addr & ~PAGE_MASK);
 }

 static __always_inline size_t __user_copy_pt(unsigned long uaddr, void *kptr,
 					     size_t n, int write_user)
 {
 	struct mm_struct *mm = current->mm;
 	unsigned long offset, done, size, kaddr;
 	void *from, *to;

 	done = 0;
 retry:
 	spin_lock(&mm->page_table_lock);
 	do {
 		kaddr = follow_table(mm, uaddr, write_user);
 		if (IS_ERR_VALUE(kaddr))
 			goto fault;

 		offset = uaddr & ~PAGE_MASK;
 		size = min(n - done, PAGE_SIZE - offset);
 		if (write_user) {
 			to = (void *) kaddr;
 			from = kptr + done;
 		} else {
 			from = (void *) kaddr;
 			to = kptr + done;
 		}
 		memcpy(to, from, size);
 		done += size;
 		uaddr += size;
 	} while (done < n);
 	spin_unlock(&mm->page_table_lock);
 	return n - done;
 fault:
 	spin_unlock(&mm->page_table_lock);
 	if (__handle_fault(uaddr, -kaddr, write_user))
 		return n - done;
 	goto retry;
 }

 /*
  * Do DAT for user address by page table walk, return kernel address.
  * This function needs to be called with current->mm->page_table_lock held.
  */
 static __always_inline unsigned long __dat_user_addr(unsigned long uaddr,
 						     int write)
 {
 	struct mm_struct *mm = current->mm;
 	unsigned long kaddr;
 	int rc;

 retry:
 	kaddr = follow_table(mm, uaddr, write);
 	if (IS_ERR_VALUE(kaddr))
 		goto fault;

 	return kaddr;
 fault:
 	spin_unlock(&mm->page_table_lock);
 	rc = __handle_fault(uaddr, -kaddr, write);
 	spin_lock(&mm->page_table_lock);
 	if (!rc)
 		goto retry;
 	return 0;
 }

 size_t copy_from_user_pt(size_t n, const void __user *from, void *to)
 {
 	size_t rc;

 	if (segment_eq(get_fs(), KERNEL_DS)) {
 		memcpy(to, (void __kernel __force *) from, n);
 		return 0;
 	}
 	rc = __user_copy_pt((unsigned long) from, to, n, 0);
 	if (unlikely(rc))
 		memset(to + n - rc, 0, rc);
 	return rc;
 }

 size_t copy_to_user_pt(size_t n, void __user *to, const void *from)
 {
 	if (segment_eq(get_fs(), KERNEL_DS)) {
 		memcpy((void __kernel __force *) to, from, n);
 		return 0;
 	}
 	return __user_copy_pt((unsigned long) to, (void *) from, n, 1);
 }

 static size_t clear_user_pt(size_t n, void __user *to)
 {
 	long done, size, ret;

 	if (segment_eq(get_fs(), KERNEL_DS)) {
 		memset((void __kernel __force *) to, 0, n);
 		return 0;
 	}
 	done = 0;
 	do {
 		if (n - done > PAGE_SIZE)
 			size = PAGE_SIZE;
 		else
 			size = n - done;
 		ret = __user_copy_pt((unsigned long) to + done,
 				      &empty_zero_page, size, 1);
 		done += size;
 		if (ret)
 			return ret + n - done;
 	} while (done < n);
 	return 0;
 }

 static size_t strnlen_user_pt(size_t count, const char __user *src)
 {
 	unsigned long uaddr = (unsigned long) src;
 	struct mm_struct *mm = current->mm;
 	unsigned long offset, done, len, kaddr;
 	size_t len_str;

 	if (segment_eq(get_fs(), KERNEL_DS))
 		return strnlen((const char __kernel __force *) src, count) + 1;
 	done = 0;
 retry:
 	spin_lock(&mm->page_table_lock);
 	do {
 		kaddr = follow_table(mm, uaddr, 0);
 		if (IS_ERR_VALUE(kaddr))
 			goto fault;

 		offset = uaddr & ~PAGE_MASK;
 		len = min(count - done, PAGE_SIZE - offset);
 		len_str = strnlen((char *) kaddr, len);
 		done += len_str;
 		uaddr += len_str;
 	} while ((len_str == len) && (done < count));
 	spin_unlock(&mm->page_table_lock);
 	return done + 1;
 fault:
 	spin_unlock(&mm->page_table_lock);
 	if (__handle_fault(uaddr, -kaddr, 0))
 		return 0;
 	goto retry;
 }

 static size_t strncpy_from_user_pt(size_t count, const char __user *src,
 				   char *dst)
 {
 	size_t n = strnlen_user_pt(count, src);

 	if (!n)
 		return -EFAULT;
 	if (n > count)
 		n = count;
 	if (segment_eq(get_fs(), KERNEL_DS)) {
 		memcpy(dst, (const char __kernel __force *) src, n);
 		if (dst[n-1] == '\0')
 			return n-1;
 		else
 			return n;
 	}
 	if (__user_copy_pt((unsigned long) src, dst, n, 0))
 		return -EFAULT;
 	if (dst[n-1] == '\0')
 		return n-1;
 	else
 		return n;
 }

 static size_t copy_in_user_pt(size_t n, void __user *to,
 			      const void __user *from)
 {
 	struct mm_struct *mm = current->mm;
 	unsigned long offset_max, uaddr, done, size, error_code;
 	unsigned long uaddr_from = (unsigned long) from;
 	unsigned long uaddr_to = (unsigned long) to;
 	unsigned long kaddr_to, kaddr_from;
 	int write_user;

 	if (segment_eq(get_fs(), KERNEL_DS)) {
 		memcpy((void __force *) to, (void __force *) from, n);
 		return 0;
 	}
 	done = 0;
 retry:
 	spin_lock(&mm->page_table_lock);
 	do {
 		write_user = 0;
 		uaddr = uaddr_from;
 		kaddr_from = follow_table(mm, uaddr_from, 0);
 		error_code = kaddr_from;
 		if (IS_ERR_VALUE(error_code))
 			goto fault;

 		write_user = 1;
 		uaddr = uaddr_to;
 		kaddr_to = follow_table(mm, uaddr_to, 1);
 		error_code = (unsigned long) kaddr_to;
 		if (IS_ERR_VALUE(error_code))
 			goto fault;

 		offset_max = max(uaddr_from & ~PAGE_MASK,
 				 uaddr_to & ~PAGE_MASK);
 		size = min(n - done, PAGE_SIZE - offset_max);

 		memcpy((void *) kaddr_to, (void *) kaddr_from, size);
 		done += size;
 		uaddr_from += size;
 		uaddr_to += size;
 	} while (done < n);
 	spin_unlock(&mm->page_table_lock);
 	return n - done;
 fault:
 	spin_unlock(&mm->page_table_lock);
 	if (__handle_fault(uaddr, -error_code, write_user))
 		return n - done;
 	goto retry;
 }

 #define __futex_atomic_op(insn, ret, oldval, newval, uaddr, oparg)	\
 	asm volatile("0: l   %1,0(%6)\n"				\
 		     "1: " insn						\
 		     "2: cs  %1,%2,0(%6)\n"				\
 		     "3: jl  1b\n"					\
 		     "   lhi %0,0\n"					\
 		     "4:\n"						\
 		     EX_TABLE(0b,4b) EX_TABLE(2b,4b) EX_TABLE(3b,4b)	\
 		     : "=d" (ret), "=&d" (oldval), "=&d" (newval),	\
 		       "=m" (*uaddr)					\
 		     : "0" (-EFAULT), "d" (oparg), "a" (uaddr),		\
 		       "m" (*uaddr) : "cc" );

 static int __futex_atomic_op_pt(int op, u32 __user *uaddr, int oparg, int *old)
 {
 	int oldval = 0, newval, ret;

 	switch (op) {
 	case FUTEX_OP_SET:
 		__futex_atomic_op("lr %2,%5\n",
 				  ret, oldval, newval, uaddr, oparg);
 		break;
 	case FUTEX_OP_ADD:
 		__futex_atomic_op("lr %2,%1\nar %2,%5\n",
 				  ret, oldval, newval, uaddr, oparg);
 		break;
 	case FUTEX_OP_OR:
 		__futex_atomic_op("lr %2,%1\nor %2,%5\n",
 				  ret, oldval, newval, uaddr, oparg);
 		break;
 	case FUTEX_OP_ANDN:
 		__futex_atomic_op("lr %2,%1\nnr %2,%5\n",
 				  ret, oldval, newval, uaddr, oparg);
 		break;
 	case FUTEX_OP_XOR:
 		__futex_atomic_op("lr %2,%1\nxr %2,%5\n",
 				  ret, oldval, newval, uaddr, oparg);
 		break;
 	default:
 		ret = -ENOSYS;
 	}
 	if (ret == 0)
 		*old = oldval;
 	return ret;
 }

 int futex_atomic_op_pt(int op, u32 __user *uaddr, int oparg, int *old)
 {
 	int ret;

 	if (segment_eq(get_fs(), KERNEL_DS))
 		return __futex_atomic_op_pt(op, uaddr, oparg, old);
 	spin_lock(&current->mm->page_table_lock);
 	uaddr = (u32 __force __user *)
 		__dat_user_addr((__force unsigned long) uaddr, 1);
 	if (!uaddr) {
 		spin_unlock(&current->mm->page_table_lock);
 		return -EFAULT;
 	}
 	get_page(virt_to_page(uaddr));
 	spin_unlock(&current->mm->page_table_lock);
 	ret = __futex_atomic_op_pt(op, uaddr, oparg, old);
 	put_page(virt_to_page(uaddr));
 	return ret;
 }

 static int __futex_atomic_cmpxchg_pt(u32 *uval, u32 __user *uaddr,
 				     u32 oldval, u32 newval)
 {
 	int ret;

 	asm volatile("0: cs   %1,%4,0(%5)\n"
 		     "1: la   %0,0\n"
 		     "2:\n"
 		     EX_TABLE(0b,2b) EX_TABLE(1b,2b)
 		     : "=d" (ret), "+d" (oldval), "=m" (*uaddr)
 		     : "0" (-EFAULT), "d" (newval), "a" (uaddr), "m" (*uaddr)
 		     : "cc", "memory" );
 	*uval = oldval;
 	return ret;
 }

 int futex_atomic_cmpxchg_pt(u32 *uval, u32 __user *uaddr,
 			    u32 oldval, u32 newval)
 {
 	int ret;

 	if (segment_eq(get_fs(), KERNEL_DS))
 		return __futex_atomic_cmpxchg_pt(uval, uaddr, oldval, newval);
 	spin_lock(&current->mm->page_table_lock);
 	uaddr = (u32 __force __user *)
 		__dat_user_addr((__force unsigned long) uaddr, 1);
 	if (!uaddr) {
 		spin_unlock(&current->mm->page_table_lock);
 		return -EFAULT;
 	}
 	get_page(virt_to_page(uaddr));
 	spin_unlock(&current->mm->page_table_lock);
 	ret = __futex_atomic_cmpxchg_pt(uval, uaddr, oldval, newval);
 	put_page(virt_to_page(uaddr));
 	return ret;
 }

 struct uaccess_ops uaccess_pt = {
 	.copy_from_user		= copy_from_user_pt,
 	.copy_from_user_small	= copy_from_user_pt,
 	.copy_to_user		= copy_to_user_pt,
 	.copy_to_user_small	= copy_to_user_pt,
 	.copy_in_user		= copy_in_user_pt,
 	.clear_user		= clear_user_pt,
 	.strnlen_user		= strnlen_user_pt,
 	.strncpy_from_user	= strncpy_from_user_pt,
 	.futex_atomic_op	= futex_atomic_op_pt,
 	.futex_atomic_cmpxchg	= futex_atomic_cmpxchg_pt,
 };
	/*
	* User access functions based on page table walks for enhanced
	* system layout without hardware support.
	*
	* Copyright IBM Corp. 2006, 2012
	* Author(s): Gerald Schaefer (gerald.schaefer@de.ibm.com)
	*/

	#include <linux/errno.h>
	#include <linux/hardirq.h>
	#include <linux/mm.h>
	#include <linux/hugetlb.h>
	#include <asm/uaccess.h>
	#include <asm/futex.h>
	#include "uaccess.h"


	/*
	* Returns kernel address for user virtual address. If the returned address is
	* >= -4095 (IS_ERR_VALUE(x) returns true), a fault has occured and the address
	* contains the (negative) exception code.
	*/
	static __always_inline unsigned long follow_table(struct mm_struct *mm,
	unsigned long addr, int write)
	{
	pgd_t *pgd;
	pud_t *pud;
	pmd_t *pmd;
	pte_t *ptep;

	pgd = pgd_offset(mm, addr);
	if (pgd_none(pgd) \|\| unlikely(pgd_bad(pgd)))
	return -0x3aUL;

	pud = pud_offset(pgd, addr);
	if (pud_none(pud) \|\| unlikely(pud_bad(pud)))
	return -0x3bUL;

	pmd = pmd_offset(pud, addr);
	if (pmd_none(*pmd))
	return -0x10UL;
	if (pmd_huge(*pmd)) {
	if (write && (pmd_val(*pmd) & _SEGMENT_ENTRY_RO))
	return -0x04UL;
	return (pmd_val(*pmd) & HPAGE_MASK) + (addr & ~HPAGE_MASK);
	}
	if (unlikely(pmd_bad(*pmd)))
	return -0x10UL;

	ptep = pte_offset_map(pmd, addr);
	if (!pte_present(*ptep))
	return -0x11UL;
	if (write && !pte_write(*ptep))
	return -0x04UL;

	return (pte_val(*ptep) & PAGE_MASK) + (addr & ~PAGE_MASK);
	}

	static __always_inline size_t __user_copy_pt(unsigned long uaddr, void *kptr,
	size_t n, int write_user)
	{
	struct mm_struct *mm = current->mm;
	unsigned long offset, done, size, kaddr;
	void from, to;

	done = 0;
	retry:
	spin_lock(&mm->page_table_lock);
	do {
	kaddr = follow_table(mm, uaddr, write_user);
	if (IS_ERR_VALUE(kaddr))
	goto fault;

	offset = uaddr & ~PAGE_MASK;
	size = min(n - done, PAGE_SIZE - offset);
	if (write_user) {
	to = (void *) kaddr;
	from = kptr + done;
	} else {
	from = (void *) kaddr;
	to = kptr + done;
	}
	memcpy(to, from, size);
	done += size;
	uaddr += size;
	} while (done < n);
	spin_unlock(&mm->page_table_lock);
	return n - done;
	fault:
	spin_unlock(&mm->page_table_lock);
	if (__handle_fault(uaddr, -kaddr, write_user))
	return n - done;
	goto retry;
	}

	/*
	* Do DAT for user address by page table walk, return kernel address.
	* This function needs to be called with current->mm->page_table_lock held.
	*/
	static __always_inline unsigned long __dat_user_addr(unsigned long uaddr,
	int write)
	{
	struct mm_struct *mm = current->mm;
	unsigned long kaddr;
	int rc;

	retry:
	kaddr = follow_table(mm, uaddr, write);
	if (IS_ERR_VALUE(kaddr))
	goto fault;

	return kaddr;
	fault:
	spin_unlock(&mm->page_table_lock);
	rc = __handle_fault(uaddr, -kaddr, write);
	spin_lock(&mm->page_table_lock);
	if (!rc)
	goto retry;
	return 0;
	}

	size_t copy_from_user_pt(size_t n, const void __user from, void to)
	{
	size_t rc;

	if (segment_eq(get_fs(), KERNEL_DS)) {
	memcpy(to, (void __kernel __force *) from, n);
	return 0;
	}
	rc = __user_copy_pt((unsigned long) from, to, n, 0);
	if (unlikely(rc))
	memset(to + n - rc, 0, rc);
	return rc;
	}

	size_t copy_to_user_pt(size_t n, void __user to, const void from)
	{
	if (segment_eq(get_fs(), KERNEL_DS)) {
	memcpy((void __kernel __force *) to, from, n);
	return 0;
	}
	return __user_copy_pt((unsigned long) to, (void *) from, n, 1);
	}

	static size_t clear_user_pt(size_t n, void __user *to)
	{
	long done, size, ret;

	if (segment_eq(get_fs(), KERNEL_DS)) {
	memset((void __kernel __force *) to, 0, n);
	return 0;
	}
	done = 0;
	do {
	if (n - done > PAGE_SIZE)
	size = PAGE_SIZE;
	else
	size = n - done;
	ret = __user_copy_pt((unsigned long) to + done,
	&empty_zero_page, size, 1);
	done += size;
	if (ret)
	return ret + n - done;
	} while (done < n);
	return 0;
	}

	static size_t strnlen_user_pt(size_t count, const char __user *src)
	{
	unsigned long uaddr = (unsigned long) src;
	struct mm_struct *mm = current->mm;
	unsigned long offset, done, len, kaddr;
	size_t len_str;

	if (segment_eq(get_fs(), KERNEL_DS))
	return strnlen((const char __kernel __force *) src, count) + 1;
	done = 0;
	retry:
	spin_lock(&mm->page_table_lock);
	do {
	kaddr = follow_table(mm, uaddr, 0);
	if (IS_ERR_VALUE(kaddr))
	goto fault;

	offset = uaddr & ~PAGE_MASK;
	len = min(count - done, PAGE_SIZE - offset);
	len_str = strnlen((char *) kaddr, len);
	done += len_str;
	uaddr += len_str;
	} while ((len_str == len) && (done < count));
	spin_unlock(&mm->page_table_lock);
	return done + 1;
	fault:
	spin_unlock(&mm->page_table_lock);
	if (__handle_fault(uaddr, -kaddr, 0))
	return 0;
	goto retry;
	}

	static size_t strncpy_from_user_pt(size_t count, const char __user *src,
	char *dst)
	{
	size_t n = strnlen_user_pt(count, src);

	if (!n)
	return -EFAULT;
	if (n > count)
	n = count;
	if (segment_eq(get_fs(), KERNEL_DS)) {
	memcpy(dst, (const char __kernel __force *) src, n);
	if (dst[n-1] == '\0')
	return n-1;
	else
	return n;
	}
	if (__user_copy_pt((unsigned long) src, dst, n, 0))
	return -EFAULT;
	if (dst[n-1] == '\0')
	return n-1;
	else
	return n;
	}

	static size_t copy_in_user_pt(size_t n, void __user *to,
	const void __user *from)
	{
	struct mm_struct *mm = current->mm;
	unsigned long offset_max, uaddr, done, size, error_code;
	unsigned long uaddr_from = (unsigned long) from;
	unsigned long uaddr_to = (unsigned long) to;
	unsigned long kaddr_to, kaddr_from;
	int write_user;

	if (segment_eq(get_fs(), KERNEL_DS)) {
	memcpy((void __force ) to, (void __force ) from, n);
	return 0;
	}
	done = 0;
	retry:
	spin_lock(&mm->page_table_lock);
	do {
	write_user = 0;
	uaddr = uaddr_from;
	kaddr_from = follow_table(mm, uaddr_from, 0);
	error_code = kaddr_from;
	if (IS_ERR_VALUE(error_code))
	goto fault;

	write_user = 1;
	uaddr = uaddr_to;
	kaddr_to = follow_table(mm, uaddr_to, 1);
	error_code = (unsigned long) kaddr_to;
	if (IS_ERR_VALUE(error_code))
	goto fault;

	offset_max = max(uaddr_from & ~PAGE_MASK,
	uaddr_to & ~PAGE_MASK);
	size = min(n - done, PAGE_SIZE - offset_max);

	memcpy((void ) kaddr_to, (void ) kaddr_from, size);
	done += size;
	uaddr_from += size;
	uaddr_to += size;
	} while (done < n);
	spin_unlock(&mm->page_table_lock);
	return n - done;
	fault:
	spin_unlock(&mm->page_table_lock);
	if (__handle_fault(uaddr, -error_code, write_user))
	return n - done;
	goto retry;
	}

	#define __futex_atomic_op(insn, ret, oldval, newval, uaddr, oparg) \
	asm volatile("0: l %1,0(%6)\n" \
	"1: " insn \
	"2: cs %1,%2,0(%6)\n" \
	"3: jl 1b\n" \
	" lhi %0,0\n" \
	"4:\n" \
	EX_TABLE(0b,4b) EX_TABLE(2b,4b) EX_TABLE(3b,4b) \
	: "=d" (ret), "=&d" (oldval), "=&d" (newval), \
	"=m" (*uaddr) \
	: "0" (-EFAULT), "d" (oparg), "a" (uaddr), \
	"m" (*uaddr) : "cc" );

	static int __futex_atomic_op_pt(int op, u32 __user uaddr, int oparg, int old)
	{
	int oldval = 0, newval, ret;

	switch (op) {
	case FUTEX_OP_SET:
	__futex_atomic_op("lr %2,%5\n",
	ret, oldval, newval, uaddr, oparg);
	break;
	case FUTEX_OP_ADD:
	__futex_atomic_op("lr %2,%1\nar %2,%5\n",
	ret, oldval, newval, uaddr, oparg);
	break;
	case FUTEX_OP_OR:
	__futex_atomic_op("lr %2,%1\nor %2,%5\n",
	ret, oldval, newval, uaddr, oparg);
	break;
	case FUTEX_OP_ANDN:
	__futex_atomic_op("lr %2,%1\nnr %2,%5\n",
	ret, oldval, newval, uaddr, oparg);
	break;
	case FUTEX_OP_XOR:
	__futex_atomic_op("lr %2,%1\nxr %2,%5\n",
	ret, oldval, newval, uaddr, oparg);
	break;
	default:
	ret = -ENOSYS;
	}
	if (ret == 0)
	*old = oldval;
	return ret;
	}

	int futex_atomic_op_pt(int op, u32 __user uaddr, int oparg, int old)
	{
	int ret;

	if (segment_eq(get_fs(), KERNEL_DS))
	return __futex_atomic_op_pt(op, uaddr, oparg, old);
	spin_lock(&current->mm->page_table_lock);
	uaddr = (u32 __force __user *)
	__dat_user_addr((__force unsigned long) uaddr, 1);
	if (!uaddr) {
	spin_unlock(&current->mm->page_table_lock);
	return -EFAULT;
	}
	get_page(virt_to_page(uaddr));
	spin_unlock(&current->mm->page_table_lock);
	ret = __futex_atomic_op_pt(op, uaddr, oparg, old);
	put_page(virt_to_page(uaddr));
	return ret;
	}

	static int __futex_atomic_cmpxchg_pt(u32 uval, u32 __user uaddr,
	u32 oldval, u32 newval)
	{
	int ret;

	asm volatile("0: cs %1,%4,0(%5)\n"
	"1: la %0,0\n"
	"2:\n"
	EX_TABLE(0b,2b) EX_TABLE(1b,2b)
	: "=d" (ret), "+d" (oldval), "=m" (*uaddr)
	: "0" (-EFAULT), "d" (newval), "a" (uaddr), "m" (*uaddr)
	: "cc", "memory" );
	*uval = oldval;
	return ret;
	}

	int futex_atomic_cmpxchg_pt(u32 uval, u32 __user uaddr,
	u32 oldval, u32 newval)
	{
	int ret;

	if (segment_eq(get_fs(), KERNEL_DS))
	return __futex_atomic_cmpxchg_pt(uval, uaddr, oldval, newval);
	spin_lock(&current->mm->page_table_lock);
	uaddr = (u32 __force __user *)
	__dat_user_addr((__force unsigned long) uaddr, 1);
	if (!uaddr) {
	spin_unlock(&current->mm->page_table_lock);
	return -EFAULT;
	}
	get_page(virt_to_page(uaddr));
	spin_unlock(&current->mm->page_table_lock);
	ret = __futex_atomic_cmpxchg_pt(uval, uaddr, oldval, newval);
	put_page(virt_to_page(uaddr));
	return ret;
	}

	struct uaccess_ops uaccess_pt = {
	.copy_from_user = copy_from_user_pt,
	.copy_from_user_small = copy_from_user_pt,
	.copy_to_user = copy_to_user_pt,
	.copy_to_user_small = copy_to_user_pt,
	.copy_in_user = copy_in_user_pt,
	.clear_user = clear_user_pt,
	.strnlen_user = strnlen_user_pt,
	.strncpy_from_user = strncpy_from_user_pt,
	.futex_atomic_op = futex_atomic_op_pt,
	.futex_atomic_cmpxchg = futex_atomic_cmpxchg_pt,
	};