Commit | Line | Data |
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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> |
7816e210 | 20 | #include <linux/highmem.h> |
a3a9ea65 | 21 | #include <linux/hugetlb.h> |
4dd1837d | 22 | #include <linux/export.h> |
39ec58f3 LB |
23 | #include <asm/current.h> |
24 | #include <asm/page.h> | |
25 | ||
26 | static int | |
27 | pin_page_for_write(const void __user *_addr, pte_t **ptep, spinlock_t **ptlp) | |
28 | { | |
29 | unsigned long addr = (unsigned long)_addr; | |
30 | pgd_t *pgd; | |
31 | pmd_t *pmd; | |
32 | pte_t *pte; | |
516295e5 | 33 | pud_t *pud; |
39ec58f3 LB |
34 | spinlock_t *ptl; |
35 | ||
36 | pgd = pgd_offset(current->mm, addr); | |
37 | if (unlikely(pgd_none(*pgd) || pgd_bad(*pgd))) | |
38 | return 0; | |
39 | ||
516295e5 RK |
40 | pud = pud_offset(pgd, addr); |
41 | if (unlikely(pud_none(*pud) || pud_bad(*pud))) | |
42 | return 0; | |
43 | ||
44 | pmd = pmd_offset(pud, addr); | |
a3a9ea65 SC |
45 | if (unlikely(pmd_none(*pmd))) |
46 | return 0; | |
47 | ||
48 | /* | |
49 | * A pmd can be bad if it refers to a HugeTLB or THP page. | |
50 | * | |
51 | * Both THP and HugeTLB pages have the same pmd layout | |
52 | * and should not be manipulated by the pte functions. | |
53 | * | |
54 | * Lock the page table for the destination and check | |
55 | * to see that it's still huge and whether or not we will | |
0ebd7446 | 56 | * need to fault on write. |
a3a9ea65 SC |
57 | */ |
58 | if (unlikely(pmd_thp_or_huge(*pmd))) { | |
59 | ptl = ¤t->mm->page_table_lock; | |
60 | spin_lock(ptl); | |
61 | if (unlikely(!pmd_thp_or_huge(*pmd) | |
0ebd7446 | 62 | || pmd_hugewillfault(*pmd))) { |
a3a9ea65 SC |
63 | spin_unlock(ptl); |
64 | return 0; | |
65 | } | |
66 | ||
67 | *ptep = NULL; | |
68 | *ptlp = ptl; | |
69 | return 1; | |
70 | } | |
71 | ||
72 | if (unlikely(pmd_bad(*pmd))) | |
39ec58f3 LB |
73 | return 0; |
74 | ||
75 | pte = pte_offset_map_lock(current->mm, pmd, addr, &ptl); | |
76 | if (unlikely(!pte_present(*pte) || !pte_young(*pte) || | |
77 | !pte_write(*pte) || !pte_dirty(*pte))) { | |
78 | pte_unmap_unlock(pte, ptl); | |
79 | return 0; | |
80 | } | |
81 | ||
82 | *ptep = pte; | |
83 | *ptlp = ptl; | |
84 | ||
85 | return 1; | |
86 | } | |
87 | ||
cb9dc92c NP |
88 | static unsigned long noinline |
89 | __copy_to_user_memcpy(void __user *to, const void *from, unsigned long n) | |
39ec58f3 | 90 | { |
c014953d | 91 | unsigned long ua_flags; |
39ec58f3 LB |
92 | int atomic; |
93 | ||
39ec58f3 LB |
94 | if (unlikely(segment_eq(get_fs(), KERNEL_DS))) { |
95 | memcpy((void *)to, from, n); | |
96 | return 0; | |
97 | } | |
98 | ||
99 | /* the mmap semaphore is taken only if not in an atomic context */ | |
0f64b247 | 100 | atomic = faulthandler_disabled(); |
39ec58f3 LB |
101 | |
102 | if (!atomic) | |
103 | down_read(¤t->mm->mmap_sem); | |
104 | while (n) { | |
105 | pte_t *pte; | |
106 | spinlock_t *ptl; | |
107 | int tocopy; | |
108 | ||
109 | while (!pin_page_for_write(to, &pte, &ptl)) { | |
110 | if (!atomic) | |
111 | up_read(¤t->mm->mmap_sem); | |
112 | if (__put_user(0, (char __user *)to)) | |
113 | goto out; | |
114 | if (!atomic) | |
115 | down_read(¤t->mm->mmap_sem); | |
116 | } | |
117 | ||
118 | tocopy = (~(unsigned long)to & ~PAGE_MASK) + 1; | |
119 | if (tocopy > n) | |
120 | tocopy = n; | |
121 | ||
c014953d | 122 | ua_flags = uaccess_save_and_enable(); |
39ec58f3 | 123 | memcpy((void *)to, from, tocopy); |
c014953d | 124 | uaccess_restore(ua_flags); |
39ec58f3 LB |
125 | to += tocopy; |
126 | from += tocopy; | |
127 | n -= tocopy; | |
128 | ||
a3a9ea65 SC |
129 | if (pte) |
130 | pte_unmap_unlock(pte, ptl); | |
131 | else | |
132 | spin_unlock(ptl); | |
39ec58f3 LB |
133 | } |
134 | if (!atomic) | |
135 | up_read(¤t->mm->mmap_sem); | |
136 | ||
137 | out: | |
138 | return n; | |
139 | } | |
140 | ||
cb9dc92c | 141 | unsigned long |
3fba7e23 | 142 | arm_copy_to_user(void __user *to, const void *from, unsigned long n) |
cb9dc92c NP |
143 | { |
144 | /* | |
145 | * This test is stubbed out of the main function above to keep | |
146 | * the overhead for small copies low by avoiding a large | |
147 | * register dump on the stack just to reload them right away. | |
148 | * With frame pointer disabled, tail call optimization kicks in | |
149 | * as well making this test almost invisible. | |
150 | */ | |
c014953d RK |
151 | if (n < 64) { |
152 | unsigned long ua_flags = uaccess_save_and_enable(); | |
153 | n = __copy_to_user_std(to, from, n); | |
154 | uaccess_restore(ua_flags); | |
155 | } else { | |
156 | n = __copy_to_user_memcpy(to, from, n); | |
157 | } | |
158 | return n; | |
cb9dc92c | 159 | } |
4dd1837d | 160 | EXPORT_SYMBOL(arm_copy_to_user); |
cb9dc92c NP |
161 | |
162 | static unsigned long noinline | |
163 | __clear_user_memset(void __user *addr, unsigned long n) | |
39ec58f3 | 164 | { |
c014953d RK |
165 | unsigned long ua_flags; |
166 | ||
39ec58f3 LB |
167 | if (unlikely(segment_eq(get_fs(), KERNEL_DS))) { |
168 | memset((void *)addr, 0, n); | |
169 | return 0; | |
170 | } | |
171 | ||
172 | down_read(¤t->mm->mmap_sem); | |
173 | while (n) { | |
174 | pte_t *pte; | |
175 | spinlock_t *ptl; | |
176 | int tocopy; | |
177 | ||
178 | while (!pin_page_for_write(addr, &pte, &ptl)) { | |
179 | up_read(¤t->mm->mmap_sem); | |
180 | if (__put_user(0, (char __user *)addr)) | |
181 | goto out; | |
182 | down_read(¤t->mm->mmap_sem); | |
183 | } | |
184 | ||
185 | tocopy = (~(unsigned long)addr & ~PAGE_MASK) + 1; | |
186 | if (tocopy > n) | |
187 | tocopy = n; | |
188 | ||
c014953d | 189 | ua_flags = uaccess_save_and_enable(); |
39ec58f3 | 190 | memset((void *)addr, 0, tocopy); |
c014953d | 191 | uaccess_restore(ua_flags); |
39ec58f3 LB |
192 | addr += tocopy; |
193 | n -= tocopy; | |
194 | ||
a3a9ea65 SC |
195 | if (pte) |
196 | pte_unmap_unlock(pte, ptl); | |
197 | else | |
198 | spin_unlock(ptl); | |
39ec58f3 LB |
199 | } |
200 | up_read(¤t->mm->mmap_sem); | |
201 | ||
202 | out: | |
203 | return n; | |
204 | } | |
cb9dc92c | 205 | |
3fba7e23 | 206 | unsigned long arm_clear_user(void __user *addr, unsigned long n) |
cb9dc92c NP |
207 | { |
208 | /* See rational for this in __copy_to_user() above. */ | |
c014953d RK |
209 | if (n < 64) { |
210 | unsigned long ua_flags = uaccess_save_and_enable(); | |
211 | n = __clear_user_std(addr, n); | |
212 | uaccess_restore(ua_flags); | |
213 | } else { | |
214 | n = __clear_user_memset(addr, n); | |
215 | } | |
216 | return n; | |
cb9dc92c | 217 | } |
4dd1837d | 218 | EXPORT_SYMBOL(arm_clear_user); |
c626e3f5 NP |
219 | |
220 | #if 0 | |
221 | ||
222 | /* | |
223 | * This code is disabled by default, but kept around in case the chosen | |
224 | * thresholds need to be revalidated. Some overhead (small but still) | |
225 | * would be implied by a runtime determined variable threshold, and | |
226 | * so far the measurement on concerned targets didn't show a worthwhile | |
227 | * variation. | |
228 | * | |
229 | * Note that a fairly precise sched_clock() implementation is needed | |
230 | * for results to make some sense. | |
231 | */ | |
232 | ||
233 | #include <linux/vmalloc.h> | |
234 | ||
235 | static int __init test_size_treshold(void) | |
236 | { | |
237 | struct page *src_page, *dst_page; | |
238 | void *user_ptr, *kernel_ptr; | |
239 | unsigned long long t0, t1, t2; | |
240 | int size, ret; | |
241 | ||
242 | ret = -ENOMEM; | |
243 | src_page = alloc_page(GFP_KERNEL); | |
244 | if (!src_page) | |
245 | goto no_src; | |
246 | dst_page = alloc_page(GFP_KERNEL); | |
247 | if (!dst_page) | |
248 | goto no_dst; | |
249 | kernel_ptr = page_address(src_page); | |
250 | user_ptr = vmap(&dst_page, 1, VM_IOREMAP, __pgprot(__P010)); | |
251 | if (!user_ptr) | |
252 | goto no_vmap; | |
253 | ||
254 | /* warm up the src page dcache */ | |
255 | ret = __copy_to_user_memcpy(user_ptr, kernel_ptr, PAGE_SIZE); | |
256 | ||
257 | for (size = PAGE_SIZE; size >= 4; size /= 2) { | |
258 | t0 = sched_clock(); | |
259 | ret |= __copy_to_user_memcpy(user_ptr, kernel_ptr, size); | |
260 | t1 = sched_clock(); | |
261 | ret |= __copy_to_user_std(user_ptr, kernel_ptr, size); | |
262 | t2 = sched_clock(); | |
263 | printk("copy_to_user: %d %llu %llu\n", size, t1 - t0, t2 - t1); | |
264 | } | |
265 | ||
266 | for (size = PAGE_SIZE; size >= 4; size /= 2) { | |
267 | t0 = sched_clock(); | |
268 | ret |= __clear_user_memset(user_ptr, size); | |
269 | t1 = sched_clock(); | |
270 | ret |= __clear_user_std(user_ptr, size); | |
271 | t2 = sched_clock(); | |
272 | printk("clear_user: %d %llu %llu\n", size, t1 - t0, t2 - t1); | |
273 | } | |
274 | ||
275 | if (ret) | |
276 | ret = -EFAULT; | |
277 | ||
278 | vunmap(user_ptr); | |
279 | no_vmap: | |
280 | put_page(dst_page); | |
281 | no_dst: | |
282 | put_page(src_page); | |
283 | no_src: | |
284 | return ret; | |
285 | } | |
286 | ||
287 | subsys_initcall(test_size_treshold); | |
288 | ||
289 | #endif |