Merge branch 'next' of git://selinuxproject.org/~jmorris/linux-security
[linux-btrfs-devel.git] / arch / arm / lib / uaccess_with_memcpy.c
blob8b9b13649f8170304245466a9409ce5e5ae2018b
1 /*
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>
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>
23 static int
24 pin_page_for_write(const void __user *_addr, pte_t **ptep, spinlock_t **ptlp)
26 unsigned long addr = (unsigned long)_addr;
27 pgd_t *pgd;
28 pmd_t *pmd;
29 pte_t *pte;
30 pud_t *pud;
31 spinlock_t *ptl;
33 pgd = pgd_offset(current->mm, addr);
34 if (unlikely(pgd_none(*pgd) || pgd_bad(*pgd)))
35 return 0;
37 pud = pud_offset(pgd, addr);
38 if (unlikely(pud_none(*pud) || pud_bad(*pud)))
39 return 0;
41 pmd = pmd_offset(pud, addr);
42 if (unlikely(pmd_none(*pmd) || pmd_bad(*pmd)))
43 return 0;
45 pte = pte_offset_map_lock(current->mm, pmd, addr, &ptl);
46 if (unlikely(!pte_present(*pte) || !pte_young(*pte) ||
47 !pte_write(*pte) || !pte_dirty(*pte))) {
48 pte_unmap_unlock(pte, ptl);
49 return 0;
52 *ptep = pte;
53 *ptlp = ptl;
55 return 1;
58 static unsigned long noinline
59 __copy_to_user_memcpy(void __user *to, const void *from, unsigned long n)
61 int atomic;
63 if (unlikely(segment_eq(get_fs(), KERNEL_DS))) {
64 memcpy((void *)to, from, n);
65 return 0;
68 /* the mmap semaphore is taken only if not in an atomic context */
69 atomic = in_atomic();
71 if (!atomic)
72 down_read(&current->mm->mmap_sem);
73 while (n) {
74 pte_t *pte;
75 spinlock_t *ptl;
76 int tocopy;
78 while (!pin_page_for_write(to, &pte, &ptl)) {
79 if (!atomic)
80 up_read(&current->mm->mmap_sem);
81 if (__put_user(0, (char __user *)to))
82 goto out;
83 if (!atomic)
84 down_read(&current->mm->mmap_sem);
87 tocopy = (~(unsigned long)to & ~PAGE_MASK) + 1;
88 if (tocopy > n)
89 tocopy = n;
91 memcpy((void *)to, from, tocopy);
92 to += tocopy;
93 from += tocopy;
94 n -= tocopy;
96 pte_unmap_unlock(pte, ptl);
98 if (!atomic)
99 up_read(&current->mm->mmap_sem);
101 out:
102 return n;
105 unsigned long
106 __copy_to_user(void __user *to, const void *from, unsigned long n)
109 * This test is stubbed out of the main function above to keep
110 * the overhead for small copies low by avoiding a large
111 * register dump on the stack just to reload them right away.
112 * With frame pointer disabled, tail call optimization kicks in
113 * as well making this test almost invisible.
115 if (n < 64)
116 return __copy_to_user_std(to, from, n);
117 return __copy_to_user_memcpy(to, from, n);
120 static unsigned long noinline
121 __clear_user_memset(void __user *addr, unsigned long n)
123 if (unlikely(segment_eq(get_fs(), KERNEL_DS))) {
124 memset((void *)addr, 0, n);
125 return 0;
128 down_read(&current->mm->mmap_sem);
129 while (n) {
130 pte_t *pte;
131 spinlock_t *ptl;
132 int tocopy;
134 while (!pin_page_for_write(addr, &pte, &ptl)) {
135 up_read(&current->mm->mmap_sem);
136 if (__put_user(0, (char __user *)addr))
137 goto out;
138 down_read(&current->mm->mmap_sem);
141 tocopy = (~(unsigned long)addr & ~PAGE_MASK) + 1;
142 if (tocopy > n)
143 tocopy = n;
145 memset((void *)addr, 0, tocopy);
146 addr += tocopy;
147 n -= tocopy;
149 pte_unmap_unlock(pte, ptl);
151 up_read(&current->mm->mmap_sem);
153 out:
154 return n;
157 unsigned long __clear_user(void __user *addr, unsigned long n)
159 /* See rational for this in __copy_to_user() above. */
160 if (n < 64)
161 return __clear_user_std(addr, n);
162 return __clear_user_memset(addr, n);
165 #if 0
168 * This code is disabled by default, but kept around in case the chosen
169 * thresholds need to be revalidated. Some overhead (small but still)
170 * would be implied by a runtime determined variable threshold, and
171 * so far the measurement on concerned targets didn't show a worthwhile
172 * variation.
174 * Note that a fairly precise sched_clock() implementation is needed
175 * for results to make some sense.
178 #include <linux/vmalloc.h>
180 static int __init test_size_treshold(void)
182 struct page *src_page, *dst_page;
183 void *user_ptr, *kernel_ptr;
184 unsigned long long t0, t1, t2;
185 int size, ret;
187 ret = -ENOMEM;
188 src_page = alloc_page(GFP_KERNEL);
189 if (!src_page)
190 goto no_src;
191 dst_page = alloc_page(GFP_KERNEL);
192 if (!dst_page)
193 goto no_dst;
194 kernel_ptr = page_address(src_page);
195 user_ptr = vmap(&dst_page, 1, VM_IOREMAP, __pgprot(__P010));
196 if (!user_ptr)
197 goto no_vmap;
199 /* warm up the src page dcache */
200 ret = __copy_to_user_memcpy(user_ptr, kernel_ptr, PAGE_SIZE);
202 for (size = PAGE_SIZE; size >= 4; size /= 2) {
203 t0 = sched_clock();
204 ret |= __copy_to_user_memcpy(user_ptr, kernel_ptr, size);
205 t1 = sched_clock();
206 ret |= __copy_to_user_std(user_ptr, kernel_ptr, size);
207 t2 = sched_clock();
208 printk("copy_to_user: %d %llu %llu\n", size, t1 - t0, t2 - t1);
211 for (size = PAGE_SIZE; size >= 4; size /= 2) {
212 t0 = sched_clock();
213 ret |= __clear_user_memset(user_ptr, size);
214 t1 = sched_clock();
215 ret |= __clear_user_std(user_ptr, size);
216 t2 = sched_clock();
217 printk("clear_user: %d %llu %llu\n", size, t1 - t0, t2 - t1);
220 if (ret)
221 ret = -EFAULT;
223 vunmap(user_ptr);
224 no_vmap:
225 put_page(dst_page);
226 no_dst:
227 put_page(src_page);
228 no_src:
229 return ret;
232 subsys_initcall(test_size_treshold);
234 #endif