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