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