aboutsummaryrefslogtreecommitdiffstats
path: root/arch/um/kernel/skas/uaccess.c
blob: 696634214dc65551557ab88535b40557fed4eb7c (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
/*
 * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
 * Licensed under the GPL
 */

#include <linux/err.h>
#include <linux/highmem.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <asm/current.h>
#include <asm/page.h>
#include <asm/pgtable.h>
#include "kern_util.h"
#include "os.h"

pte_t *virt_to_pte(struct mm_struct *mm, unsigned long addr)
{
	pgd_t *pgd;
	pud_t *pud;
	pmd_t *pmd;

	if (mm == NULL)
		return NULL;

	pgd = pgd_offset(mm, addr);
	if (!pgd_present(*pgd))
		return NULL;

	pud = pud_offset(pgd, addr);
	if (!pud_present(*pud))
		return NULL;

	pmd = pmd_offset(pud, addr);
	if (!pmd_present(*pmd))
		return NULL;

	return pte_offset_kernel(pmd, addr);
}

static pte_t *maybe_map(unsigned long virt, int is_write)
{
	pte_t *pte = virt_to_pte(current->mm, virt);
	int err, dummy_code;

	if ((pte == NULL) || !pte_present(*pte) ||
	    (is_write && !pte_write(*pte))) {
		err = handle_page_fault(virt, 0, is_write, 1, &dummy_code);
		if (err)
			return NULL;
		pte = virt_to_pte(current->mm, virt);
	}
	if (!pte_present(*pte))
		pte = NULL;

	return pte;
}

static int do_op_one_page(unsigned long addr, int len, int is_write,
		 int (*op)(unsigned long addr, int len, void *arg), void *arg)
{
	jmp_buf buf;
	struct page *page;
	pte_t *pte;
	int n, faulted;

	pte = maybe_map(addr, is_write);
	if (pte == NULL)
		return -1;

	page = pte_page(*pte);
	addr = (unsigned long) kmap_atomic(page, KM_UML_USERCOPY) +
		(addr & ~PAGE_MASK);

	current->thread.fault_catcher = &buf;

	faulted = UML_SETJMP(&buf);
	if (faulted == 0)
		n = (*op)(addr, len, arg);
	else
		n = -1;

	current->thread.fault_catcher = NULL;

	kunmap_atomic((void *)addr, KM_UML_USERCOPY);

	return n;
}

static int buffer_op(unsigned long addr, int len, int is_write,
		     int (*op)(unsigned long, int, void *), void *arg)
{
	int size, remain, n;

	size = min(PAGE_ALIGN(addr) - addr, (unsigned long) len);
	remain = len;

	n = do_op_one_page(addr, size, is_write, op, arg);
	if (n != 0) {
		remain = (n < 0 ? remain : 0);
		goto out;
	}

	addr += size;
	remain -= size;
	if (remain == 0)
		goto out;

	while (addr < ((addr + remain) & PAGE_MASK)) {
		n = do_op_one_page(addr, PAGE_SIZE, is_write, op, arg);
		if (n != 0) {
			remain = (n < 0 ? remain : 0);
			goto out;
		}

		addr += PAGE_SIZE;
		remain -= PAGE_SIZE;
	}
	if (remain == 0)
		goto out;

	n = do_op_one_page(addr, remain, is_write, op, arg);
	if (n != 0) {
		remain = (n < 0 ? remain : 0);
		goto out;
	}

	return 0;
 out:
	return remain;
}

static int copy_chunk_from_user(unsigned long from, int len, void *arg)
{
	unsigned long *to_ptr = arg, to = *to_ptr;

	memcpy((void *) to, (void *) from, len);
	*to_ptr += len;
	return 0;
}

int copy_from_user(void *to, const void __user *from, int n)
{
	if (segment_eq(get_fs(), KERNEL_DS)) {
		memcpy(to, (__force void*)from, n);
		return 0;
	}

	return access_ok(VERIFY_READ, from, n) ?
	       buffer_op((unsigned long) from, n, 0, copy_chunk_from_user, &to):
	       n;
}

static int copy_chunk_to_user(unsigned long to, int len, void *arg)
{
	unsigned long *from_ptr = arg, from = *from_ptr;

	memcpy((void *) to, (void *) from, len);
	*from_ptr += len;
	return 0;
}

int copy_to_user(void __user *to, const void *from, int n)
{
	if (segment_eq(get_fs(), KERNEL_DS)) {
		memcpy((__force void *) to, from, n);
		return 0;
	}

	return access_ok(VERIFY_WRITE, to, n) ?
	       buffer_op((unsigned long) to, n, 1, copy_chunk_to_user, &from) :
	       n;
}

static int strncpy_chunk_from_user(unsigned long from, int len, void *arg)
{
	char **to_ptr = arg, *to = *to_ptr;
	int n;

	strncpy(to, (void *) from, len);
	n = strnlen(to, len);
	*to_ptr += n;

	if (n < len)
	        return 1;
	return 0;
}

int strncpy_from_user(char *dst, const char __user *src, int count)
{
	int n;
	char *ptr = dst;

	if (segment_eq(get_fs(), KERNEL_DS)) {
		strncpy(dst, (__force void *) src, count);
		return strnlen(dst, count);
	}

	if (!access_ok(VERIFY_READ, src, 1))
		return -EFAULT;

	n = buffer_op((unsigned long) src, count, 0, strncpy_chunk_from_user,
		      &ptr);
	if (n != 0)
		return -EFAULT;
	return strnlen(dst, count);
}

static int clear_chunk(unsigned long addr, int len, void *unused)
{
	memset((void *) addr, 0, len);
	return 0;
}

int __clear_user(void __user *mem, int len)
{
	return buffer_op((unsigned long) mem, len, 1, clear_chunk, NULL);
}

int clear_user(void __user *mem, int len)
{
	if (segment_eq(get_fs(), KERNEL_DS)) {
		memset((__force void*)mem, 0, len);
		return 0;
	}

	return access_ok(VERIFY_WRITE, mem, len) ?
	       buffer_op((unsigned long) mem, len, 1, clear_chunk, NULL) : len;
}

static int strnlen_chunk(unsigned long str, int len, void *arg)
{
	int *len_ptr = arg, n;

	n = strnlen((void *) str, len);
	*len_ptr += n;

	if (n < len)
		return 1;
	return 0;
}

int strnlen_user(const void __user *str, int len)
{
	int count = 0, n;

	if (segment_eq(get_fs(), KERNEL_DS))
		return strnlen((__force char*)str, len) + 1;

	n = buffer_op((unsigned long) str, len, 0, strnlen_chunk, &count);
	if (n == 0)
		return count + 1;
	return -EFAULT;
}