2 * linux/arch/arm/lib/uaccess_with_memcpy.c
4 * Written by: Lennert Buytenhek and Nicolas Pitre
5 * Copyright (C) 2009 Marvell Semiconductor
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.
12 #include <linux/kernel.h>
13 #include <linux/ctype.h>
14 #include <linux/uaccess.h>
15 #include <linux/rwsem.h>
17 #include <linux/sched.h>
18 #include <linux/hardirq.h> /* for in_atomic() */
19 #include <linux/gfp.h>
20 #include <linux/highmem.h>
21 #include <asm/current.h>
25 pin_page_for_write(const void __user *_addr, pte_t **ptep, spinlock_t **ptlp)
27 unsigned long addr = (unsigned long)_addr;
34 pgd = pgd_offset(current->mm, addr);
35 if (unlikely(pgd_none(*pgd) || pgd_bad(*pgd)))
38 pud = pud_offset(pgd, addr);
39 if (unlikely(pud_none(*pud) || pud_bad(*pud)))
42 pmd = pmd_offset(pud, addr);
43 if (unlikely(pmd_none(*pmd) || pmd_bad(*pmd)))
46 pte = pte_offset_map_lock(current->mm, pmd, addr, &ptl);
47 if (unlikely(!pte_present(*pte) || !pte_young(*pte) ||
48 !pte_write(*pte) || !pte_dirty(*pte))) {
49 pte_unmap_unlock(pte, ptl);
59 static unsigned long noinline
60 __copy_to_user_memcpy(void __user *to, const void *from, unsigned long n)
64 if (unlikely(segment_eq(get_fs(), KERNEL_DS))) {
65 memcpy((void *)to, from, n);
69 /* the mmap semaphore is taken only if not in an atomic context */
73 down_read(¤t->mm->mmap_sem);
79 while (!pin_page_for_write(to, &pte, &ptl)) {
81 up_read(¤t->mm->mmap_sem);
82 if (__put_user(0, (char __user *)to))
85 down_read(¤t->mm->mmap_sem);
88 tocopy = (~(unsigned long)to & ~PAGE_MASK) + 1;
92 memcpy((void *)to, from, tocopy);
97 pte_unmap_unlock(pte, ptl);
100 up_read(¤t->mm->mmap_sem);
107 __copy_to_user(void __user *to, const void *from, unsigned long n)
110 * This test is stubbed out of the main function above to keep
111 * the overhead for small copies low by avoiding a large
112 * register dump on the stack just to reload them right away.
113 * With frame pointer disabled, tail call optimization kicks in
114 * as well making this test almost invisible.
117 return __copy_to_user_std(to, from, n);
118 return __copy_to_user_memcpy(to, from, n);
121 static unsigned long noinline
122 __clear_user_memset(void __user *addr, unsigned long n)
124 if (unlikely(segment_eq(get_fs(), KERNEL_DS))) {
125 memset((void *)addr, 0, n);
129 down_read(¤t->mm->mmap_sem);
135 while (!pin_page_for_write(addr, &pte, &ptl)) {
136 up_read(¤t->mm->mmap_sem);
137 if (__put_user(0, (char __user *)addr))
139 down_read(¤t->mm->mmap_sem);
142 tocopy = (~(unsigned long)addr & ~PAGE_MASK) + 1;
146 memset((void *)addr, 0, tocopy);
150 pte_unmap_unlock(pte, ptl);
152 up_read(¤t->mm->mmap_sem);
158 unsigned long __clear_user(void __user *addr, unsigned long n)
160 /* See rational for this in __copy_to_user() above. */
162 return __clear_user_std(addr, n);
163 return __clear_user_memset(addr, n);
169 * This code is disabled by default, but kept around in case the chosen
170 * thresholds need to be revalidated. Some overhead (small but still)
171 * would be implied by a runtime determined variable threshold, and
172 * so far the measurement on concerned targets didn't show a worthwhile
175 * Note that a fairly precise sched_clock() implementation is needed
176 * for results to make some sense.
179 #include <linux/vmalloc.h>
181 static int __init test_size_treshold(void)
183 struct page *src_page, *dst_page;
184 void *user_ptr, *kernel_ptr;
185 unsigned long long t0, t1, t2;
189 src_page = alloc_page(GFP_KERNEL);
192 dst_page = alloc_page(GFP_KERNEL);
195 kernel_ptr = page_address(src_page);
196 user_ptr = vmap(&dst_page, 1, VM_IOREMAP, __pgprot(__P010));
200 /* warm up the src page dcache */
201 ret = __copy_to_user_memcpy(user_ptr, kernel_ptr, PAGE_SIZE);
203 for (size = PAGE_SIZE; size >= 4; size /= 2) {
205 ret |= __copy_to_user_memcpy(user_ptr, kernel_ptr, size);
207 ret |= __copy_to_user_std(user_ptr, kernel_ptr, size);
209 printk("copy_to_user: %d %llu %llu\n", size, t1 - t0, t2 - t1);
212 for (size = PAGE_SIZE; size >= 4; size /= 2) {
214 ret |= __clear_user_memset(user_ptr, size);
216 ret |= __clear_user_std(user_ptr, size);
218 printk("clear_user: %d %llu %llu\n", size, t1 - t0, t2 - t1);
233 subsys_initcall(test_size_treshold);