xref: /openbmc/linux/arch/um/kernel/skas/uaccess.c (revision 31e67366)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
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 <kern_util.h>
14 #include <os.h>
15 
16 pte_t *virt_to_pte(struct mm_struct *mm, unsigned long addr)
17 {
18 	pgd_t *pgd;
19 	p4d_t *p4d;
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 	p4d = p4d_offset(pgd, addr);
31 	if (!p4d_present(*p4d))
32 		return NULL;
33 
34 	pud = pud_offset(p4d, addr);
35 	if (!pud_present(*pud))
36 		return NULL;
37 
38 	pmd = pmd_offset(pud, addr);
39 	if (!pmd_present(*pmd))
40 		return NULL;
41 
42 	return pte_offset_kernel(pmd, addr);
43 }
44 
45 static pte_t *maybe_map(unsigned long virt, int is_write)
46 {
47 	pte_t *pte = virt_to_pte(current->mm, virt);
48 	int err, dummy_code;
49 
50 	if ((pte == NULL) || !pte_present(*pte) ||
51 	    (is_write && !pte_write(*pte))) {
52 		err = handle_page_fault(virt, 0, is_write, 1, &dummy_code);
53 		if (err)
54 			return NULL;
55 		pte = virt_to_pte(current->mm, virt);
56 	}
57 	if (!pte_present(*pte))
58 		pte = NULL;
59 
60 	return pte;
61 }
62 
63 static int do_op_one_page(unsigned long addr, int len, int is_write,
64 		 int (*op)(unsigned long addr, int len, void *arg), void *arg)
65 {
66 	struct page *page;
67 	pte_t *pte;
68 	int n;
69 
70 	pte = maybe_map(addr, is_write);
71 	if (pte == NULL)
72 		return -1;
73 
74 	page = pte_page(*pte);
75 #ifdef CONFIG_64BIT
76 	pagefault_disable();
77 	addr = (unsigned long) page_address(page) +
78 		(addr & ~PAGE_MASK);
79 #else
80 	addr = (unsigned long) kmap_atomic(page) +
81 		(addr & ~PAGE_MASK);
82 #endif
83 	n = (*op)(addr, len, arg);
84 
85 #ifdef CONFIG_64BIT
86 	pagefault_enable();
87 #else
88 	kunmap_atomic((void *)addr);
89 #endif
90 
91 	return n;
92 }
93 
94 static long buffer_op(unsigned long addr, int len, int is_write,
95 		      int (*op)(unsigned long, int, void *), void *arg)
96 {
97 	long size, remain, n;
98 
99 	size = min(PAGE_ALIGN(addr) - addr, (unsigned long) len);
100 	remain = len;
101 
102 	n = do_op_one_page(addr, size, is_write, op, arg);
103 	if (n != 0) {
104 		remain = (n < 0 ? remain : 0);
105 		goto out;
106 	}
107 
108 	addr += size;
109 	remain -= size;
110 	if (remain == 0)
111 		goto out;
112 
113 	while (addr < ((addr + remain) & PAGE_MASK)) {
114 		n = do_op_one_page(addr, PAGE_SIZE, is_write, op, arg);
115 		if (n != 0) {
116 			remain = (n < 0 ? remain : 0);
117 			goto out;
118 		}
119 
120 		addr += PAGE_SIZE;
121 		remain -= PAGE_SIZE;
122 	}
123 	if (remain == 0)
124 		goto out;
125 
126 	n = do_op_one_page(addr, remain, is_write, op, arg);
127 	if (n != 0) {
128 		remain = (n < 0 ? remain : 0);
129 		goto out;
130 	}
131 
132 	return 0;
133  out:
134 	return remain;
135 }
136 
137 static int copy_chunk_from_user(unsigned long from, int len, void *arg)
138 {
139 	unsigned long *to_ptr = arg, to = *to_ptr;
140 
141 	memcpy((void *) to, (void *) from, len);
142 	*to_ptr += len;
143 	return 0;
144 }
145 
146 unsigned long raw_copy_from_user(void *to, const void __user *from, unsigned long n)
147 {
148 	if (uaccess_kernel()) {
149 		memcpy(to, (__force void*)from, n);
150 		return 0;
151 	}
152 
153 	return buffer_op((unsigned long) from, n, 0, copy_chunk_from_user, &to);
154 }
155 EXPORT_SYMBOL(raw_copy_from_user);
156 
157 static int copy_chunk_to_user(unsigned long to, int len, void *arg)
158 {
159 	unsigned long *from_ptr = arg, from = *from_ptr;
160 
161 	memcpy((void *) to, (void *) from, len);
162 	*from_ptr += len;
163 	return 0;
164 }
165 
166 unsigned long raw_copy_to_user(void __user *to, const void *from, unsigned long n)
167 {
168 	if (uaccess_kernel()) {
169 		memcpy((__force void *) to, from, n);
170 		return 0;
171 	}
172 
173 	return buffer_op((unsigned long) to, n, 1, copy_chunk_to_user, &from);
174 }
175 EXPORT_SYMBOL(raw_copy_to_user);
176 
177 static 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 
191 long __strncpy_from_user(char *dst, const char __user *src, long count)
192 {
193 	long n;
194 	char *ptr = dst;
195 
196 	if (uaccess_kernel()) {
197 		strncpy(dst, (__force void *) src, count);
198 		return strnlen(dst, count);
199 	}
200 
201 	n = buffer_op((unsigned long) src, count, 0, strncpy_chunk_from_user,
202 		      &ptr);
203 	if (n != 0)
204 		return -EFAULT;
205 	return strnlen(dst, count);
206 }
207 EXPORT_SYMBOL(__strncpy_from_user);
208 
209 static int clear_chunk(unsigned long addr, int len, void *unused)
210 {
211 	memset((void *) addr, 0, len);
212 	return 0;
213 }
214 
215 unsigned long __clear_user(void __user *mem, unsigned long len)
216 {
217 	if (uaccess_kernel()) {
218 		memset((__force void*)mem, 0, len);
219 		return 0;
220 	}
221 
222 	return buffer_op((unsigned long) mem, len, 1, clear_chunk, NULL);
223 }
224 EXPORT_SYMBOL(__clear_user);
225 
226 static int strnlen_chunk(unsigned long str, int len, void *arg)
227 {
228 	int *len_ptr = arg, n;
229 
230 	n = strnlen((void *) str, len);
231 	*len_ptr += n;
232 
233 	if (n < len)
234 		return 1;
235 	return 0;
236 }
237 
238 long __strnlen_user(const void __user *str, long len)
239 {
240 	int count = 0, n;
241 
242 	if (uaccess_kernel())
243 		return strnlen((__force char*)str, len) + 1;
244 
245 	n = buffer_op((unsigned long) str, len, 0, strnlen_chunk, &count);
246 	if (n == 0)
247 		return count + 1;
248 	return 0;
249 }
250 EXPORT_SYMBOL(__strnlen_user);
251