summaryrefslogtreecommitdiff
path: root/arch/arm/lib/uaccess_with_memcpy.c
blob: c9450982a1558e4c5d687f6584e5e3b26f382643 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
// SPDX-License-Identifier: GPL-2.0-only
/*
 *  linux/arch/arm/lib/uaccess_with_memcpy.c
 *
 *  Written by: Lennert Buytenhek and Nicolas Pitre
 *  Copyright (C) 2009 Marvell Semiconductor
 */

#include <linux/kernel.h>
#include <linux/ctype.h>
#include <linux/uaccess.h>
#include <linux/rwsem.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/hardirq.h> /* for in_atomic() */
#include <linux/gfp.h>
#include <linux/highmem.h>
#include <linux/hugetlb.h>
#include <asm/current.h>
#include <asm/page.h>

static int
pin_page_for_write(const void __user *_addr, pte_t **ptep, spinlock_t **ptlp)
{
	unsigned long addr = (unsigned long)_addr;
	pgd_t *pgd;
	pmd_t *pmd;
	pte_t *pte;
	pud_t *pud;
	spinlock_t *ptl;

	pgd = pgd_offset(current->mm, addr);
	if (unlikely(pgd_none(*pgd) || pgd_bad(*pgd)))
		return 0;

	pud = pud_offset(pgd, addr);
	if (unlikely(pud_none(*pud) || pud_bad(*pud)))
		return 0;

	pmd = pmd_offset(pud, addr);
	if (unlikely(pmd_none(*pmd)))
		return 0;

	/*
	 * A pmd can be bad if it refers to a HugeTLB or THP page.
	 *
	 * Both THP and HugeTLB pages have the same pmd layout
	 * and should not be manipulated by the pte functions.
	 *
	 * Lock the page table for the destination and check
	 * to see that it's still huge and whether or not we will
	 * need to fault on write.
	 */
	if (unlikely(pmd_thp_or_huge(*pmd))) {
		ptl = &current->mm->page_table_lock;
		spin_lock(ptl);
		if (unlikely(!pmd_thp_or_huge(*pmd)
			|| pmd_hugewillfault(*pmd))) {
			spin_unlock(ptl);
			return 0;
		}

		*ptep = NULL;
		*ptlp = ptl;
		return 1;
	}

	if (unlikely(pmd_bad(*pmd)))
		return 0;

	pte = pte_offset_map_lock(current->mm, pmd, addr, &ptl);
	if (unlikely(!pte_present(*pte) || !pte_young(*pte) ||
	    !pte_write(*pte) || !pte_dirty(*pte))) {
		pte_unmap_unlock(pte, ptl);
		return 0;
	}

	*ptep = pte;
	*ptlp = ptl;

	return 1;
}

static unsigned long noinline
__copy_to_user_memcpy(void __user *to, const void *from, unsigned long n)
{
	unsigned long ua_flags;
	int atomic;

	if (uaccess_kernel()) {
		memcpy((void *)to, from, n);
		return 0;
	}

	/* the mmap semaphore is taken only if not in an atomic context */
	atomic = faulthandler_disabled();

	if (!atomic)
		down_read(&current->mm->mmap_sem);
	while (n) {
		pte_t *pte;
		spinlock_t *ptl;
		int tocopy;

		while (!pin_page_for_write(to, &pte, &ptl)) {
			if (!atomic)
				up_read(&current->mm->mmap_sem);
			if (__put_user(0, (char __user *)to))
				goto out;
			if (!atomic)
				down_read(&current->mm->mmap_sem);
		}

		tocopy = (~(unsigned long)to & ~PAGE_MASK) + 1;
		if (tocopy > n)
			tocopy = n;

		ua_flags = uaccess_save_and_enable();
		memcpy((void *)to, from, tocopy);
		uaccess_restore(ua_flags);
		to += tocopy;
		from += tocopy;
		n -= tocopy;

		if (pte)
			pte_unmap_unlock(pte, ptl);
		else
			spin_unlock(ptl);
	}
	if (!atomic)
		up_read(&current->mm->mmap_sem);

out:
	return n;
}

unsigned long
arm_copy_to_user(void __user *to, const void *from, unsigned long n)
{
	/*
	 * This test is stubbed out of the main function above to keep
	 * the overhead for small copies low by avoiding a large
	 * register dump on the stack just to reload them right away.
	 * With frame pointer disabled, tail call optimization kicks in
	 * as well making this test almost invisible.
	 */
	if (n < 64) {
		unsigned long ua_flags = uaccess_save_and_enable();
		n = __copy_to_user_std(to, from, n);
		uaccess_restore(ua_flags);
	} else {
		n = __copy_to_user_memcpy(uaccess_mask_range_ptr(to, n),
					  from, n);
	}
	return n;
}
	
static unsigned long noinline
__clear_user_memset(void __user *addr, unsigned long n)
{
	unsigned long ua_flags;

	if (uaccess_kernel()) {
		memset((void *)addr, 0, n);
		return 0;
	}

	down_read(&current->mm->mmap_sem);
	while (n) {
		pte_t *pte;
		spinlock_t *ptl;
		int tocopy;

		while (!pin_page_for_write(addr, &pte, &ptl)) {
			up_read(&current->mm->mmap_sem);
			if (__put_user(0, (char __user *)addr))
				goto out;
			down_read(&current->mm->mmap_sem);
		}

		tocopy = (~(unsigned long)addr & ~PAGE_MASK) + 1;
		if (tocopy > n)
			tocopy = n;

		ua_flags = uaccess_save_and_enable();
		memset((void *)addr, 0, tocopy);
		uaccess_restore(ua_flags);
		addr += tocopy;
		n -= tocopy;

		if (pte)
			pte_unmap_unlock(pte, ptl);
		else
			spin_unlock(ptl);
	}
	up_read(&current->mm->mmap_sem);

out:
	return n;
}

unsigned long arm_clear_user(void __user *addr, unsigned long n)
{
	/* See rational for this in __copy_to_user() above. */
	if (n < 64) {
		unsigned long ua_flags = uaccess_save_and_enable();
		n = __clear_user_std(addr, n);
		uaccess_restore(ua_flags);
	} else {
		n = __clear_user_memset(addr, n);
	}
	return n;
}

#if 0

/*
 * This code is disabled by default, but kept around in case the chosen
 * thresholds need to be revalidated.  Some overhead (small but still)
 * would be implied by a runtime determined variable threshold, and
 * so far the measurement on concerned targets didn't show a worthwhile
 * variation.
 *
 * Note that a fairly precise sched_clock() implementation is needed
 * for results to make some sense.
 */

#include <linux/vmalloc.h>

static int __init test_size_treshold(void)
{
	struct page *src_page, *dst_page;
	void *user_ptr, *kernel_ptr;
	unsigned long long t0, t1, t2;
	int size, ret;

	ret = -ENOMEM;
	src_page = alloc_page(GFP_KERNEL);
	if (!src_page)
		goto no_src;
	dst_page = alloc_page(GFP_KERNEL);
	if (!dst_page)
		goto no_dst;
	kernel_ptr = page_address(src_page);
	user_ptr = vmap(&dst_page, 1, VM_IOREMAP, __pgprot(__P010));
	if (!user_ptr)
		goto no_vmap;

	/* warm up the src page dcache */
	ret = __copy_to_user_memcpy(user_ptr, kernel_ptr, PAGE_SIZE);

	for (size = PAGE_SIZE; size >= 4; size /= 2) {
		t0 = sched_clock();
		ret |= __copy_to_user_memcpy(user_ptr, kernel_ptr, size);
		t1 = sched_clock();
		ret |= __copy_to_user_std(user_ptr, kernel_ptr, size);
		t2 = sched_clock();
		printk("copy_to_user: %d %llu %llu\n", size, t1 - t0, t2 - t1);
	}

	for (size = PAGE_SIZE; size >= 4; size /= 2) {
		t0 = sched_clock();
		ret |= __clear_user_memset(user_ptr, size);
		t1 = sched_clock();
		ret |= __clear_user_std(user_ptr, size);
		t2 = sched_clock();
		printk("clear_user: %d %llu %llu\n", size, t1 - t0, t2 - t1);
	}

	if (ret)
		ret = -EFAULT;

	vunmap(user_ptr);
no_vmap:
	put_page(dst_page);
no_dst:
	put_page(src_page);
no_src:
	return ret;
}

subsys_initcall(test_size_treshold);

#endif