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 <linux/gfp.h> 20#include <asm/current.h> 21#include <asm/page.h> 22 23static int 24pin_page_for_write(const void __user *_addr, pte_t **ptep, spinlock_t **ptlp) 25{ 26 unsigned long addr = (unsigned long)_addr; 27 pgd_t *pgd; 28 pmd_t *pmd; 29 pte_t *pte; 30 spinlock_t *ptl; 31 32 pgd = pgd_offset(current->mm, addr); 33 if (unlikely(pgd_none(*pgd) || pgd_bad(*pgd))) 34 return 0; 35 36 pmd = pmd_offset(pgd, addr); 37 if (unlikely(pmd_none(*pmd) || pmd_bad(*pmd))) 38 return 0; 39 40 pte = pte_offset_map_lock(current->mm, pmd, addr, &ptl); 41 if (unlikely(!pte_present(*pte) || !pte_young(*pte) || 42 !pte_write(*pte) || !pte_dirty(*pte))) { 43 pte_unmap_unlock(pte, ptl); 44 return 0; 45 } 46 47 *ptep = pte; 48 *ptlp = ptl; 49 50 return 1; 51} 52 53static unsigned long noinline 54__copy_to_user_memcpy(void __user *to, const void *from, unsigned long n) 55{ 56 int atomic; 57 58 if (unlikely(segment_eq(get_fs(), KERNEL_DS))) { 59 memcpy((void *)to, from, n); 60 return 0; 61 } 62 63 /* the mmap semaphore is taken only if not in an atomic context */ 64 atomic = in_atomic(); 65 66 if (!atomic) 67 down_read(¤t->mm->mmap_sem); 68 while (n) { 69 pte_t *pte; 70 spinlock_t *ptl; 71 int tocopy; 72 73 while (!pin_page_for_write(to, &pte, &ptl)) { 74 if (!atomic) 75 up_read(¤t->mm->mmap_sem); 76 if (__put_user(0, (char __user *)to)) 77 goto out; 78 if (!atomic) 79 down_read(¤t->mm->mmap_sem); 80 } 81 82 tocopy = (~(unsigned long)to & ~PAGE_MASK) + 1; 83 if (tocopy > n) 84 tocopy = n; 85 86 memcpy((void *)to, from, tocopy); 87 to += tocopy; 88 from += tocopy; 89 n -= tocopy; 90 91 pte_unmap_unlock(pte, ptl); 92 } 93 if (!atomic) 94 up_read(¤t->mm->mmap_sem); 95 96out: 97 return n; 98} 99 100unsigned long 101__copy_to_user(void __user *to, const void *from, unsigned long n) 102{ 103 /* 104 * This test is stubbed out of the main function above to keep 105 * the overhead for small copies low by avoiding a large 106 * register dump on the stack just to reload them right away. 107 * With frame pointer disabled, tail call optimization kicks in 108 * as well making this test almost invisible. 109 */ 110 if (n < 64) 111 return __copy_to_user_std(to, from, n); 112 return __copy_to_user_memcpy(to, from, n); 113} 114 115static unsigned long noinline 116__clear_user_memset(void __user *addr, unsigned long n) 117{ 118 if (unlikely(segment_eq(get_fs(), KERNEL_DS))) { 119 memset((void *)addr, 0, n); 120 return 0; 121 } 122 123 down_read(¤t->mm->mmap_sem); 124 while (n) { 125 pte_t *pte; 126 spinlock_t *ptl; 127 int tocopy; 128 129 while (!pin_page_for_write(addr, &pte, &ptl)) { 130 up_read(¤t->mm->mmap_sem); 131 if (__put_user(0, (char __user *)addr)) 132 goto out; 133 down_read(¤t->mm->mmap_sem); 134 } 135 136 tocopy = (~(unsigned long)addr & ~PAGE_MASK) + 1; 137 if (tocopy > n) 138 tocopy = n; 139 140 memset((void *)addr, 0, tocopy); 141 addr += tocopy; 142 n -= tocopy; 143 144 pte_unmap_unlock(pte, ptl); 145 } 146 up_read(¤t->mm->mmap_sem); 147 148out: 149 return n; 150} 151 152unsigned long __clear_user(void __user *addr, unsigned long n) 153{ 154 /* See rational for this in __copy_to_user() above. */ 155 if (n < 64) 156 return __clear_user_std(addr, n); 157 return __clear_user_memset(addr, n); 158} 159