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39ec58f3 LB |
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() */ | |
5a0e3ad6 | 19 | #include <linux/gfp.h> |
39ec58f3 LB |
20 | #include <asm/current.h> |
21 | #include <asm/page.h> | |
22 | ||
23 | static int | |
24 | pin_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 | ||
cb9dc92c NP |
53 | static unsigned long noinline |
54 | __copy_to_user_memcpy(void __user *to, const void *from, unsigned long n) | |
39ec58f3 LB |
55 | { |
56 | int atomic; | |
57 | ||
39ec58f3 LB |
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 | ||
96 | out: | |
97 | return n; | |
98 | } | |
99 | ||
cb9dc92c NP |
100 | unsigned 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 | */ | |
c626e3f5 | 110 | if (n < 64) |
cb9dc92c NP |
111 | return __copy_to_user_std(to, from, n); |
112 | return __copy_to_user_memcpy(to, from, n); | |
113 | } | |
114 | ||
115 | static unsigned long noinline | |
116 | __clear_user_memset(void __user *addr, unsigned long n) | |
39ec58f3 | 117 | { |
39ec58f3 LB |
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 | ||
148 | out: | |
149 | return n; | |
150 | } | |
cb9dc92c NP |
151 | |
152 | unsigned long __clear_user(void __user *addr, unsigned long n) | |
153 | { | |
154 | /* See rational for this in __copy_to_user() above. */ | |
c626e3f5 | 155 | if (n < 64) |
cb9dc92c NP |
156 | return __clear_user_std(addr, n); |
157 | return __clear_user_memset(addr, n); | |
158 | } | |
c626e3f5 NP |
159 | |
160 | #if 0 | |
161 | ||
162 | /* | |
163 | * This code is disabled by default, but kept around in case the chosen | |
164 | * thresholds need to be revalidated. Some overhead (small but still) | |
165 | * would be implied by a runtime determined variable threshold, and | |
166 | * so far the measurement on concerned targets didn't show a worthwhile | |
167 | * variation. | |
168 | * | |
169 | * Note that a fairly precise sched_clock() implementation is needed | |
170 | * for results to make some sense. | |
171 | */ | |
172 | ||
173 | #include <linux/vmalloc.h> | |
174 | ||
175 | static int __init test_size_treshold(void) | |
176 | { | |
177 | struct page *src_page, *dst_page; | |
178 | void *user_ptr, *kernel_ptr; | |
179 | unsigned long long t0, t1, t2; | |
180 | int size, ret; | |
181 | ||
182 | ret = -ENOMEM; | |
183 | src_page = alloc_page(GFP_KERNEL); | |
184 | if (!src_page) | |
185 | goto no_src; | |
186 | dst_page = alloc_page(GFP_KERNEL); | |
187 | if (!dst_page) | |
188 | goto no_dst; | |
189 | kernel_ptr = page_address(src_page); | |
190 | user_ptr = vmap(&dst_page, 1, VM_IOREMAP, __pgprot(__P010)); | |
191 | if (!user_ptr) | |
192 | goto no_vmap; | |
193 | ||
194 | /* warm up the src page dcache */ | |
195 | ret = __copy_to_user_memcpy(user_ptr, kernel_ptr, PAGE_SIZE); | |
196 | ||
197 | for (size = PAGE_SIZE; size >= 4; size /= 2) { | |
198 | t0 = sched_clock(); | |
199 | ret |= __copy_to_user_memcpy(user_ptr, kernel_ptr, size); | |
200 | t1 = sched_clock(); | |
201 | ret |= __copy_to_user_std(user_ptr, kernel_ptr, size); | |
202 | t2 = sched_clock(); | |
203 | printk("copy_to_user: %d %llu %llu\n", size, t1 - t0, t2 - t1); | |
204 | } | |
205 | ||
206 | for (size = PAGE_SIZE; size >= 4; size /= 2) { | |
207 | t0 = sched_clock(); | |
208 | ret |= __clear_user_memset(user_ptr, size); | |
209 | t1 = sched_clock(); | |
210 | ret |= __clear_user_std(user_ptr, size); | |
211 | t2 = sched_clock(); | |
212 | printk("clear_user: %d %llu %llu\n", size, t1 - t0, t2 - t1); | |
213 | } | |
214 | ||
215 | if (ret) | |
216 | ret = -EFAULT; | |
217 | ||
218 | vunmap(user_ptr); | |
219 | no_vmap: | |
220 | put_page(dst_page); | |
221 | no_dst: | |
222 | put_page(src_page); | |
223 | no_src: | |
224 | return ret; | |
225 | } | |
226 | ||
227 | subsys_initcall(test_size_treshold); | |
228 | ||
229 | #endif |