| Lennert Buytenhek | 39ec58f | 2009-03-09 14:30:09 -0400 | [diff] [blame^] | 1 | /* |
| 2 | * linux/arch/arm/lib/uaccess_with_memcpy.c |
| 3 | * |
| 4 | * Written by: Lennert Buytenhek and Nicolas Pitre |
| 5 | * Copyright (C) 2009 Marvell Semiconductor |
| 6 | * |
| 7 | * This program is free software; you can redistribute it and/or modify |
| 8 | * it under the terms of the GNU General Public License version 2 as |
| 9 | * published by the Free Software Foundation. |
| 10 | */ |
| 11 | |
| 12 | #include <linux/kernel.h> |
| 13 | #include <linux/ctype.h> |
| 14 | #include <linux/uaccess.h> |
| 15 | #include <linux/rwsem.h> |
| 16 | #include <linux/mm.h> |
| 17 | #include <linux/sched.h> |
| 18 | #include <linux/hardirq.h> /* for in_atomic() */ |
| 19 | #include <asm/current.h> |
| 20 | #include <asm/page.h> |
| 21 | |
| 22 | static int |
| 23 | pin_page_for_write(const void __user *_addr, pte_t **ptep, spinlock_t **ptlp) |
| 24 | { |
| 25 | unsigned long addr = (unsigned long)_addr; |
| 26 | pgd_t *pgd; |
| 27 | pmd_t *pmd; |
| 28 | pte_t *pte; |
| 29 | spinlock_t *ptl; |
| 30 | |
| 31 | pgd = pgd_offset(current->mm, addr); |
| 32 | if (unlikely(pgd_none(*pgd) || pgd_bad(*pgd))) |
| 33 | return 0; |
| 34 | |
| 35 | pmd = pmd_offset(pgd, addr); |
| 36 | if (unlikely(pmd_none(*pmd) || pmd_bad(*pmd))) |
| 37 | return 0; |
| 38 | |
| 39 | pte = pte_offset_map_lock(current->mm, pmd, addr, &ptl); |
| 40 | if (unlikely(!pte_present(*pte) || !pte_young(*pte) || |
| 41 | !pte_write(*pte) || !pte_dirty(*pte))) { |
| 42 | pte_unmap_unlock(pte, ptl); |
| 43 | return 0; |
| 44 | } |
| 45 | |
| 46 | *ptep = pte; |
| 47 | *ptlp = ptl; |
| 48 | |
| 49 | return 1; |
| 50 | } |
| 51 | |
| 52 | unsigned long |
| 53 | __copy_to_user(void __user *to, const void *from, unsigned long n) |
| 54 | { |
| 55 | int atomic; |
| 56 | |
| 57 | if (n < 1024) |
| 58 | return __copy_to_user_std(to, from, n); |
| 59 | |
| 60 | if (unlikely(segment_eq(get_fs(), KERNEL_DS))) { |
| 61 | memcpy((void *)to, from, n); |
| 62 | return 0; |
| 63 | } |
| 64 | |
| 65 | /* the mmap semaphore is taken only if not in an atomic context */ |
| 66 | atomic = in_atomic(); |
| 67 | |
| 68 | if (!atomic) |
| 69 | down_read(¤t->mm->mmap_sem); |
| 70 | while (n) { |
| 71 | pte_t *pte; |
| 72 | spinlock_t *ptl; |
| 73 | int tocopy; |
| 74 | |
| 75 | while (!pin_page_for_write(to, &pte, &ptl)) { |
| 76 | if (!atomic) |
| 77 | up_read(¤t->mm->mmap_sem); |
| 78 | if (__put_user(0, (char __user *)to)) |
| 79 | goto out; |
| 80 | if (!atomic) |
| 81 | down_read(¤t->mm->mmap_sem); |
| 82 | } |
| 83 | |
| 84 | tocopy = (~(unsigned long)to & ~PAGE_MASK) + 1; |
| 85 | if (tocopy > n) |
| 86 | tocopy = n; |
| 87 | |
| 88 | memcpy((void *)to, from, tocopy); |
| 89 | to += tocopy; |
| 90 | from += tocopy; |
| 91 | n -= tocopy; |
| 92 | |
| 93 | pte_unmap_unlock(pte, ptl); |
| 94 | } |
| 95 | if (!atomic) |
| 96 | up_read(¤t->mm->mmap_sem); |
| 97 | |
| 98 | out: |
| 99 | return n; |
| 100 | } |
| 101 | |
| 102 | unsigned long __clear_user(void __user *addr, unsigned long n) |
| 103 | { |
| 104 | if (n < 256) |
| 105 | return __clear_user_std(addr, n); |
| 106 | |
| 107 | if (unlikely(segment_eq(get_fs(), KERNEL_DS))) { |
| 108 | memset((void *)addr, 0, n); |
| 109 | return 0; |
| 110 | } |
| 111 | |
| 112 | down_read(¤t->mm->mmap_sem); |
| 113 | while (n) { |
| 114 | pte_t *pte; |
| 115 | spinlock_t *ptl; |
| 116 | int tocopy; |
| 117 | |
| 118 | while (!pin_page_for_write(addr, &pte, &ptl)) { |
| 119 | up_read(¤t->mm->mmap_sem); |
| 120 | if (__put_user(0, (char __user *)addr)) |
| 121 | goto out; |
| 122 | down_read(¤t->mm->mmap_sem); |
| 123 | } |
| 124 | |
| 125 | tocopy = (~(unsigned long)addr & ~PAGE_MASK) + 1; |
| 126 | if (tocopy > n) |
| 127 | tocopy = n; |
| 128 | |
| 129 | memset((void *)addr, 0, tocopy); |
| 130 | addr += tocopy; |
| 131 | n -= tocopy; |
| 132 | |
| 133 | pte_unmap_unlock(pte, ptl); |
| 134 | } |
| 135 | up_read(¤t->mm->mmap_sem); |
| 136 | |
| 137 | out: |
| 138 | return n; |
| 139 | } |