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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; | |
516295e5 | 30 | pud_t *pud; |
39ec58f3 LB |
31 | spinlock_t *ptl; |
32 | ||
33 | pgd = pgd_offset(current->mm, addr); | |
34 | if (unlikely(pgd_none(*pgd) || pgd_bad(*pgd))) | |
35 | return 0; | |
36 | ||
516295e5 RK |
37 | pud = pud_offset(pgd, addr); |
38 | if (unlikely(pud_none(*pud) || pud_bad(*pud))) | |
39 | return 0; | |
40 | ||
41 | pmd = pmd_offset(pud, addr); | |
39ec58f3 LB |
42 | if (unlikely(pmd_none(*pmd) || pmd_bad(*pmd))) |
43 | return 0; | |
44 | ||
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; | |
50 | } | |
51 | ||
52 | *ptep = pte; | |
53 | *ptlp = ptl; | |
54 | ||
55 | return 1; | |
56 | } | |
57 | ||
cb9dc92c NP |
58 | static unsigned long noinline |
59 | __copy_to_user_memcpy(void __user *to, const void *from, unsigned long n) | |
39ec58f3 LB |
60 | { |
61 | int atomic; | |
62 | ||
39ec58f3 LB |
63 | if (unlikely(segment_eq(get_fs(), KERNEL_DS))) { |
64 | memcpy((void *)to, from, n); | |
65 | return 0; | |
66 | } | |
67 | ||
68 | /* the mmap semaphore is taken only if not in an atomic context */ | |
69 | atomic = in_atomic(); | |
70 | ||
71 | if (!atomic) | |
72 | down_read(¤t->mm->mmap_sem); | |
73 | while (n) { | |
74 | pte_t *pte; | |
75 | spinlock_t *ptl; | |
76 | int tocopy; | |
77 | ||
78 | while (!pin_page_for_write(to, &pte, &ptl)) { | |
79 | if (!atomic) | |
80 | up_read(¤t->mm->mmap_sem); | |
81 | if (__put_user(0, (char __user *)to)) | |
82 | goto out; | |
83 | if (!atomic) | |
84 | down_read(¤t->mm->mmap_sem); | |
85 | } | |
86 | ||
87 | tocopy = (~(unsigned long)to & ~PAGE_MASK) + 1; | |
88 | if (tocopy > n) | |
89 | tocopy = n; | |
90 | ||
91 | memcpy((void *)to, from, tocopy); | |
92 | to += tocopy; | |
93 | from += tocopy; | |
94 | n -= tocopy; | |
95 | ||
96 | pte_unmap_unlock(pte, ptl); | |
97 | } | |
98 | if (!atomic) | |
99 | up_read(¤t->mm->mmap_sem); | |
100 | ||
101 | out: | |
102 | return n; | |
103 | } | |
104 | ||
cb9dc92c NP |
105 | unsigned long |
106 | __copy_to_user(void __user *to, const void *from, unsigned long n) | |
107 | { | |
108 | /* | |
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. | |
114 | */ | |
c626e3f5 | 115 | if (n < 64) |
cb9dc92c NP |
116 | return __copy_to_user_std(to, from, n); |
117 | return __copy_to_user_memcpy(to, from, n); | |
118 | } | |
119 | ||
120 | static unsigned long noinline | |
121 | __clear_user_memset(void __user *addr, unsigned long n) | |
39ec58f3 | 122 | { |
39ec58f3 LB |
123 | if (unlikely(segment_eq(get_fs(), KERNEL_DS))) { |
124 | memset((void *)addr, 0, n); | |
125 | return 0; | |
126 | } | |
127 | ||
128 | down_read(¤t->mm->mmap_sem); | |
129 | while (n) { | |
130 | pte_t *pte; | |
131 | spinlock_t *ptl; | |
132 | int tocopy; | |
133 | ||
134 | while (!pin_page_for_write(addr, &pte, &ptl)) { | |
135 | up_read(¤t->mm->mmap_sem); | |
136 | if (__put_user(0, (char __user *)addr)) | |
137 | goto out; | |
138 | down_read(¤t->mm->mmap_sem); | |
139 | } | |
140 | ||
141 | tocopy = (~(unsigned long)addr & ~PAGE_MASK) + 1; | |
142 | if (tocopy > n) | |
143 | tocopy = n; | |
144 | ||
145 | memset((void *)addr, 0, tocopy); | |
146 | addr += tocopy; | |
147 | n -= tocopy; | |
148 | ||
149 | pte_unmap_unlock(pte, ptl); | |
150 | } | |
151 | up_read(¤t->mm->mmap_sem); | |
152 | ||
153 | out: | |
154 | return n; | |
155 | } | |
cb9dc92c NP |
156 | |
157 | unsigned long __clear_user(void __user *addr, unsigned long n) | |
158 | { | |
159 | /* See rational for this in __copy_to_user() above. */ | |
c626e3f5 | 160 | if (n < 64) |
cb9dc92c NP |
161 | return __clear_user_std(addr, n); |
162 | return __clear_user_memset(addr, n); | |
163 | } | |
c626e3f5 NP |
164 | |
165 | #if 0 | |
166 | ||
167 | /* | |
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. | |
173 | * | |
174 | * Note that a fairly precise sched_clock() implementation is needed | |
175 | * for results to make some sense. | |
176 | */ | |
177 | ||
178 | #include <linux/vmalloc.h> | |
179 | ||
180 | static int __init test_size_treshold(void) | |
181 | { | |
182 | struct page *src_page, *dst_page; | |
183 | void *user_ptr, *kernel_ptr; | |
184 | unsigned long long t0, t1, t2; | |
185 | int size, ret; | |
186 | ||
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; | |
198 | ||
199 | /* warm up the src page dcache */ | |
200 | ret = __copy_to_user_memcpy(user_ptr, kernel_ptr, PAGE_SIZE); | |
201 | ||
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); | |
209 | } | |
210 | ||
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); | |
218 | } | |
219 | ||
220 | if (ret) | |
221 | ret = -EFAULT; | |
222 | ||
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; | |
230 | } | |
231 | ||
232 | subsys_initcall(test_size_treshold); | |
233 | ||
234 | #endif |