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/*
* linux/arch/arm/lib/uaccess_with_memcpy.c
*
* Written by: Lennert Buytenhek and Nicolas Pitre
* Copyright (C) 2009 Marvell Semiconductor
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/kernel.h>
#include <linux/ctype.h>
#include <linux/uaccess.h>
#include <linux/rwsem.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/hardirq.h> /* for in_atomic() */
#include <asm/current.h>
#include <asm/page.h>
static int
pin_page_for_write(const void __user *_addr, pte_t **ptep, spinlock_t **ptlp)
{
unsigned long addr = (unsigned long)_addr;
pgd_t *pgd;
pmd_t *pmd;
pte_t *pte;
spinlock_t *ptl;
pgd = pgd_offset(current->mm, addr);
if (unlikely(pgd_none(*pgd) || pgd_bad(*pgd)))
return 0;
pmd = pmd_offset(pgd, addr);
if (unlikely(pmd_none(*pmd) || pmd_bad(*pmd)))
return 0;
pte = pte_offset_map_lock(current->mm, pmd, addr, &ptl);
if (unlikely(!pte_present(*pte) || !pte_young(*pte) ||
!pte_write(*pte) || !pte_dirty(*pte))) {
pte_unmap_unlock(pte, ptl);
return 0;
}
*ptep = pte;
*ptlp = ptl;
return 1;
}
unsigned long
__copy_to_user(void __user *to, const void *from, unsigned long n)
{
int atomic;
if (n < 1024)
return __copy_to_user_std(to, from, n);
if (unlikely(segment_eq(get_fs(), KERNEL_DS))) {
memcpy((void *)to, from, n);
return 0;
}
/* the mmap semaphore is taken only if not in an atomic context */
atomic = in_atomic();
if (!atomic)
down_read(¤t->mm->mmap_sem);
while (n) {
pte_t *pte;
spinlock_t *ptl;
int tocopy;
while (!pin_page_for_write(to, &pte, &ptl)) {
if (!atomic)
up_read(¤t->mm->mmap_sem);
if (__put_user(0, (char __user *)to))
goto out;
if (!atomic)
down_read(¤t->mm->mmap_sem);
}
tocopy = (~(unsigned long)to & ~PAGE_MASK) + 1;
if (tocopy > n)
tocopy = n;
memcpy((void *)to, from, tocopy);
to += tocopy;
from += tocopy;
n -= tocopy;
pte_unmap_unlock(pte, ptl);
}
if (!atomic)
up_read(¤t->mm->mmap_sem);
out:
return n;
}
unsigned long __clear_user(void __user *addr, unsigned long n)
{
if (n < 256)
return __clear_user_std(addr, n);
if (unlikely(segment_eq(get_fs(), KERNEL_DS))) {
memset((void *)addr, 0, n);
return 0;
}
down_read(¤t->mm->mmap_sem);
while (n) {
pte_t *pte;
spinlock_t *ptl;
int tocopy;
while (!pin_page_for_write(addr, &pte, &ptl)) {
up_read(¤t->mm->mmap_sem);
if (__put_user(0, (char __user *)addr))
goto out;
down_read(¤t->mm->mmap_sem);
}
tocopy = (~(unsigned long)addr & ~PAGE_MASK) + 1;
if (tocopy > n)
tocopy = n;
memset((void *)addr, 0, tocopy);
addr += tocopy;
n -= tocopy;
pte_unmap_unlock(pte, ptl);
}
up_read(¤t->mm->mmap_sem);
out:
return n;
}
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