xref: /openbmc/linux/arch/um/kernel/skas/uaccess.c (revision 31af04cd)
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 
17 pte_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 
41 static 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 
59 static 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;
66 
67 	pte = maybe_map(addr, is_write);
68 	if (pte == NULL)
69 		return -1;
70 
71 	page = pte_page(*pte);
72 #ifdef CONFIG_64BIT
73 	pagefault_disable();
74 	addr = (unsigned long) page_address(page) +
75 		(addr & ~PAGE_MASK);
76 #else
77 	addr = (unsigned long) kmap_atomic(page) +
78 		(addr & ~PAGE_MASK);
79 #endif
80 	n = (*op)(addr, len, arg);
81 
82 #ifdef CONFIG_64BIT
83 	pagefault_enable();
84 #else
85 	kunmap_atomic((void *)addr);
86 #endif
87 
88 	return n;
89 }
90 
91 static long buffer_op(unsigned long addr, int len, int is_write,
92 		      int (*op)(unsigned long, int, void *), void *arg)
93 {
94 	long size, remain, n;
95 
96 	size = min(PAGE_ALIGN(addr) - addr, (unsigned long) len);
97 	remain = len;
98 
99 	n = do_op_one_page(addr, size, is_write, op, arg);
100 	if (n != 0) {
101 		remain = (n < 0 ? remain : 0);
102 		goto out;
103 	}
104 
105 	addr += size;
106 	remain -= size;
107 	if (remain == 0)
108 		goto out;
109 
110 	while (addr < ((addr + remain) & PAGE_MASK)) {
111 		n = do_op_one_page(addr, PAGE_SIZE, is_write, op, arg);
112 		if (n != 0) {
113 			remain = (n < 0 ? remain : 0);
114 			goto out;
115 		}
116 
117 		addr += PAGE_SIZE;
118 		remain -= PAGE_SIZE;
119 	}
120 	if (remain == 0)
121 		goto out;
122 
123 	n = do_op_one_page(addr, remain, is_write, op, arg);
124 	if (n != 0) {
125 		remain = (n < 0 ? remain : 0);
126 		goto out;
127 	}
128 
129 	return 0;
130  out:
131 	return remain;
132 }
133 
134 static int copy_chunk_from_user(unsigned long from, int len, void *arg)
135 {
136 	unsigned long *to_ptr = arg, to = *to_ptr;
137 
138 	memcpy((void *) to, (void *) from, len);
139 	*to_ptr += len;
140 	return 0;
141 }
142 
143 unsigned long raw_copy_from_user(void *to, const void __user *from, unsigned long n)
144 {
145 	if (uaccess_kernel()) {
146 		memcpy(to, (__force void*)from, n);
147 		return 0;
148 	}
149 
150 	return buffer_op((unsigned long) from, n, 0, copy_chunk_from_user, &to);
151 }
152 EXPORT_SYMBOL(raw_copy_from_user);
153 
154 static int copy_chunk_to_user(unsigned long to, int len, void *arg)
155 {
156 	unsigned long *from_ptr = arg, from = *from_ptr;
157 
158 	memcpy((void *) to, (void *) from, len);
159 	*from_ptr += len;
160 	return 0;
161 }
162 
163 unsigned long raw_copy_to_user(void __user *to, const void *from, unsigned long n)
164 {
165 	if (uaccess_kernel()) {
166 		memcpy((__force void *) to, from, n);
167 		return 0;
168 	}
169 
170 	return buffer_op((unsigned long) to, n, 1, copy_chunk_to_user, &from);
171 }
172 EXPORT_SYMBOL(raw_copy_to_user);
173 
174 static int strncpy_chunk_from_user(unsigned long from, int len, void *arg)
175 {
176 	char **to_ptr = arg, *to = *to_ptr;
177 	int n;
178 
179 	strncpy(to, (void *) from, len);
180 	n = strnlen(to, len);
181 	*to_ptr += n;
182 
183 	if (n < len)
184 	        return 1;
185 	return 0;
186 }
187 
188 long __strncpy_from_user(char *dst, const char __user *src, long count)
189 {
190 	long n;
191 	char *ptr = dst;
192 
193 	if (uaccess_kernel()) {
194 		strncpy(dst, (__force void *) src, count);
195 		return strnlen(dst, count);
196 	}
197 
198 	n = buffer_op((unsigned long) src, count, 0, strncpy_chunk_from_user,
199 		      &ptr);
200 	if (n != 0)
201 		return -EFAULT;
202 	return strnlen(dst, count);
203 }
204 EXPORT_SYMBOL(__strncpy_from_user);
205 
206 static int clear_chunk(unsigned long addr, int len, void *unused)
207 {
208 	memset((void *) addr, 0, len);
209 	return 0;
210 }
211 
212 unsigned long __clear_user(void __user *mem, unsigned long len)
213 {
214 	if (uaccess_kernel()) {
215 		memset((__force void*)mem, 0, len);
216 		return 0;
217 	}
218 
219 	return buffer_op((unsigned long) mem, len, 1, clear_chunk, NULL);
220 }
221 EXPORT_SYMBOL(__clear_user);
222 
223 static int strnlen_chunk(unsigned long str, int len, void *arg)
224 {
225 	int *len_ptr = arg, n;
226 
227 	n = strnlen((void *) str, len);
228 	*len_ptr += n;
229 
230 	if (n < len)
231 		return 1;
232 	return 0;
233 }
234 
235 long __strnlen_user(const void __user *str, long len)
236 {
237 	int count = 0, n;
238 
239 	if (uaccess_kernel())
240 		return strnlen((__force char*)str, len) + 1;
241 
242 	n = buffer_op((unsigned long) str, len, 0, strnlen_chunk, &count);
243 	if (n == 0)
244 		return count + 1;
245 	return 0;
246 }
247 EXPORT_SYMBOL(__strnlen_user);
248