1/*
2 * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
3 * Licensed under the GPL
4 */
5
6#include <linux/err.h>
7#include <linux/highmem.h>
8#include <linux/mm.h>
9#include <linux/module.h>
10#include <linux/sched.h>
11#include <asm/current.h>
12#include <asm/page.h>
13#include <asm/pgtable.h>
14#include <kern_util.h>
15#include <os.h>
16
17pte_t *virt_to_pte(struct mm_struct *mm, unsigned long addr)
18{
19	pgd_t *pgd;
20	pud_t *pud;
21	pmd_t *pmd;
22
23	if (mm == NULL)
24		return NULL;
25
26	pgd = pgd_offset(mm, addr);
27	if (!pgd_present(*pgd))
28		return NULL;
29
30	pud = pud_offset(pgd, addr);
31	if (!pud_present(*pud))
32		return NULL;
33
34	pmd = pmd_offset(pud, addr);
35	if (!pmd_present(*pmd))
36		return NULL;
37
38	return pte_offset_kernel(pmd, addr);
39}
40
41static pte_t *maybe_map(unsigned long virt, int is_write)
42{
43	pte_t *pte = virt_to_pte(current->mm, virt);
44	int err, dummy_code;
45
46	if ((pte == NULL) || !pte_present(*pte) ||
47	    (is_write && !pte_write(*pte))) {
48		err = handle_page_fault(virt, 0, is_write, 1, &dummy_code);
49		if (err)
50			return NULL;
51		pte = virt_to_pte(current->mm, virt);
52	}
53	if (!pte_present(*pte))
54		pte = NULL;
55
56	return pte;
57}
58
59static int do_op_one_page(unsigned long addr, int len, int is_write,
60		 int (*op)(unsigned long addr, int len, void *arg), void *arg)
61{
62	jmp_buf buf;
63	struct page *page;
64	pte_t *pte;
65	int n, faulted;
66
67	pte = maybe_map(addr, is_write);
68	if (pte == NULL)
69		return -1;
70
71	page = pte_page(*pte);
72	addr = (unsigned long) kmap_atomic(page) +
73		(addr & ~PAGE_MASK);
74
75	current->thread.fault_catcher = &buf;
76
77	faulted = UML_SETJMP(&buf);
78	if (faulted == 0)
79		n = (*op)(addr, len, arg);
80	else
81		n = -1;
82
83	current->thread.fault_catcher = NULL;
84
85	kunmap_atomic((void *)addr);
86
87	return n;
88}
89
90static int buffer_op(unsigned long addr, int len, int is_write,
91		     int (*op)(unsigned long, int, void *), void *arg)
92{
93	int size, remain, n;
94
95	size = min(PAGE_ALIGN(addr) - addr, (unsigned long) len);
96	remain = len;
97
98	n = do_op_one_page(addr, size, is_write, op, arg);
99	if (n != 0) {
100		remain = (n < 0 ? remain : 0);
101		goto out;
102	}
103
104	addr += size;
105	remain -= size;
106	if (remain == 0)
107		goto out;
108
109	while (addr < ((addr + remain) & PAGE_MASK)) {
110		n = do_op_one_page(addr, PAGE_SIZE, is_write, op, arg);
111		if (n != 0) {
112			remain = (n < 0 ? remain : 0);
113			goto out;
114		}
115
116		addr += PAGE_SIZE;
117		remain -= PAGE_SIZE;
118	}
119	if (remain == 0)
120		goto out;
121
122	n = do_op_one_page(addr, remain, is_write, op, arg);
123	if (n != 0) {
124		remain = (n < 0 ? remain : 0);
125		goto out;
126	}
127
128	return 0;
129 out:
130	return remain;
131}
132
133static int copy_chunk_from_user(unsigned long from, int len, void *arg)
134{
135	unsigned long *to_ptr = arg, to = *to_ptr;
136
137	memcpy((void *) to, (void *) from, len);
138	*to_ptr += len;
139	return 0;
140}
141
142int copy_from_user(void *to, const void __user *from, int n)
143{
144	if (segment_eq(get_fs(), KERNEL_DS)) {
145		memcpy(to, (__force void*)from, n);
146		return 0;
147	}
148
149	return access_ok(VERIFY_READ, from, n) ?
150	       buffer_op((unsigned long) from, n, 0, copy_chunk_from_user, &to):
151	       n;
152}
153EXPORT_SYMBOL(copy_from_user);
154
155static int copy_chunk_to_user(unsigned long to, int len, void *arg)
156{
157	unsigned long *from_ptr = arg, from = *from_ptr;
158
159	memcpy((void *) to, (void *) from, len);
160	*from_ptr += len;
161	return 0;
162}
163
164int copy_to_user(void __user *to, const void *from, int n)
165{
166	if (segment_eq(get_fs(), KERNEL_DS)) {
167		memcpy((__force void *) to, from, n);
168		return 0;
169	}
170
171	return access_ok(VERIFY_WRITE, to, n) ?
172	       buffer_op((unsigned long) to, n, 1, copy_chunk_to_user, &from) :
173	       n;
174}
175EXPORT_SYMBOL(copy_to_user);
176
177static int strncpy_chunk_from_user(unsigned long from, int len, void *arg)
178{
179	char **to_ptr = arg, *to = *to_ptr;
180	int n;
181
182	strncpy(to, (void *) from, len);
183	n = strnlen(to, len);
184	*to_ptr += n;
185
186	if (n < len)
187	        return 1;
188	return 0;
189}
190
191int strncpy_from_user(char *dst, const char __user *src, int count)
192{
193	int n;
194	char *ptr = dst;
195
196	if (segment_eq(get_fs(), KERNEL_DS)) {
197		strncpy(dst, (__force void *) src, count);
198		return strnlen(dst, count);
199	}
200
201	if (!access_ok(VERIFY_READ, src, 1))
202		return -EFAULT;
203
204	n = buffer_op((unsigned long) src, count, 0, strncpy_chunk_from_user,
205		      &ptr);
206	if (n != 0)
207		return -EFAULT;
208	return strnlen(dst, count);
209}
210EXPORT_SYMBOL(strncpy_from_user);
211
212static int clear_chunk(unsigned long addr, int len, void *unused)
213{
214	memset((void *) addr, 0, len);
215	return 0;
216}
217
218int __clear_user(void __user *mem, int len)
219{
220	return buffer_op((unsigned long) mem, len, 1, clear_chunk, NULL);
221}
222
223int clear_user(void __user *mem, int len)
224{
225	if (segment_eq(get_fs(), KERNEL_DS)) {
226		memset((__force void*)mem, 0, len);
227		return 0;
228	}
229
230	return access_ok(VERIFY_WRITE, mem, len) ?
231	       buffer_op((unsigned long) mem, len, 1, clear_chunk, NULL) : len;
232}
233EXPORT_SYMBOL(clear_user);
234
235static int strnlen_chunk(unsigned long str, int len, void *arg)
236{
237	int *len_ptr = arg, n;
238
239	n = strnlen((void *) str, len);
240	*len_ptr += n;
241
242	if (n < len)
243		return 1;
244	return 0;
245}
246
247int strnlen_user(const void __user *str, int len)
248{
249	int count = 0, n;
250
251	if (segment_eq(get_fs(), KERNEL_DS))
252		return strnlen((__force char*)str, len) + 1;
253
254	n = buffer_op((unsigned long) str, len, 0, strnlen_chunk, &count);
255	if (n == 0)
256		return count + 1;
257	return 0;
258}
259EXPORT_SYMBOL(strnlen_user);
260