xref: /openbmc/linux/arch/um/kernel/skas/uaccess.c (revision 8bb227ac)
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 <asm/futex.h>
15 #include <os.h>
16 
virt_to_pte(struct mm_struct * mm,unsigned long addr)17 pte_t *virt_to_pte(struct mm_struct *mm, unsigned long addr)
18 {
19 	pgd_t *pgd;
20 	p4d_t *p4d;
21 	pud_t *pud;
22 	pmd_t *pmd;
23 
24 	if (mm == NULL)
25 		return NULL;
26 
27 	pgd = pgd_offset(mm, addr);
28 	if (!pgd_present(*pgd))
29 		return NULL;
30 
31 	p4d = p4d_offset(pgd, addr);
32 	if (!p4d_present(*p4d))
33 		return NULL;
34 
35 	pud = pud_offset(p4d, addr);
36 	if (!pud_present(*pud))
37 		return NULL;
38 
39 	pmd = pmd_offset(pud, addr);
40 	if (!pmd_present(*pmd))
41 		return NULL;
42 
43 	return pte_offset_kernel(pmd, addr);
44 }
45 
maybe_map(unsigned long virt,int is_write)46 static pte_t *maybe_map(unsigned long virt, int is_write)
47 {
48 	pte_t *pte = virt_to_pte(current->mm, virt);
49 	int err, dummy_code;
50 
51 	if ((pte == NULL) || !pte_present(*pte) ||
52 	    (is_write && !pte_write(*pte))) {
53 		err = handle_page_fault(virt, 0, is_write, 1, &dummy_code);
54 		if (err)
55 			return NULL;
56 		pte = virt_to_pte(current->mm, virt);
57 	}
58 	if (!pte_present(*pte))
59 		pte = NULL;
60 
61 	return pte;
62 }
63 
do_op_one_page(unsigned long addr,int len,int is_write,int (* op)(unsigned long addr,int len,void * arg),void * arg)64 static int do_op_one_page(unsigned long addr, int len, int is_write,
65 		 int (*op)(unsigned long addr, int len, void *arg), void *arg)
66 {
67 	struct page *page;
68 	pte_t *pte;
69 	int n;
70 
71 	pte = maybe_map(addr, is_write);
72 	if (pte == NULL)
73 		return -1;
74 
75 	page = pte_page(*pte);
76 #ifdef CONFIG_64BIT
77 	pagefault_disable();
78 	addr = (unsigned long) page_address(page) +
79 		(addr & ~PAGE_MASK);
80 #else
81 	addr = (unsigned long) kmap_atomic(page) +
82 		(addr & ~PAGE_MASK);
83 #endif
84 	n = (*op)(addr, len, arg);
85 
86 #ifdef CONFIG_64BIT
87 	pagefault_enable();
88 #else
89 	kunmap_atomic((void *)addr);
90 #endif
91 
92 	return n;
93 }
94 
buffer_op(unsigned long addr,int len,int is_write,int (* op)(unsigned long,int,void *),void * arg)95 static long buffer_op(unsigned long addr, int len, int is_write,
96 		      int (*op)(unsigned long, int, void *), void *arg)
97 {
98 	long size, remain, n;
99 
100 	size = min(PAGE_ALIGN(addr) - addr, (unsigned long) len);
101 	remain = len;
102 
103 	n = do_op_one_page(addr, size, is_write, op, arg);
104 	if (n != 0) {
105 		remain = (n < 0 ? remain : 0);
106 		goto out;
107 	}
108 
109 	addr += size;
110 	remain -= size;
111 	if (remain == 0)
112 		goto out;
113 
114 	while (addr < ((addr + remain) & PAGE_MASK)) {
115 		n = do_op_one_page(addr, PAGE_SIZE, is_write, op, arg);
116 		if (n != 0) {
117 			remain = (n < 0 ? remain : 0);
118 			goto out;
119 		}
120 
121 		addr += PAGE_SIZE;
122 		remain -= PAGE_SIZE;
123 	}
124 	if (remain == 0)
125 		goto out;
126 
127 	n = do_op_one_page(addr, remain, is_write, op, arg);
128 	if (n != 0) {
129 		remain = (n < 0 ? remain : 0);
130 		goto out;
131 	}
132 
133 	return 0;
134  out:
135 	return remain;
136 }
137 
copy_chunk_from_user(unsigned long from,int len,void * arg)138 static int copy_chunk_from_user(unsigned long from, int len, void *arg)
139 {
140 	unsigned long *to_ptr = arg, to = *to_ptr;
141 
142 	memcpy((void *) to, (void *) from, len);
143 	*to_ptr += len;
144 	return 0;
145 }
146 
raw_copy_from_user(void * to,const void __user * from,unsigned long n)147 unsigned long raw_copy_from_user(void *to, const void __user *from, unsigned long n)
148 {
149 	return buffer_op((unsigned long) from, n, 0, copy_chunk_from_user, &to);
150 }
151 EXPORT_SYMBOL(raw_copy_from_user);
152 
copy_chunk_to_user(unsigned long to,int len,void * arg)153 static int copy_chunk_to_user(unsigned long to, int len, void *arg)
154 {
155 	unsigned long *from_ptr = arg, from = *from_ptr;
156 
157 	memcpy((void *) to, (void *) from, len);
158 	*from_ptr += len;
159 	return 0;
160 }
161 
raw_copy_to_user(void __user * to,const void * from,unsigned long n)162 unsigned long raw_copy_to_user(void __user *to, const void *from, unsigned long n)
163 {
164 	return buffer_op((unsigned long) to, n, 1, copy_chunk_to_user, &from);
165 }
166 EXPORT_SYMBOL(raw_copy_to_user);
167 
strncpy_chunk_from_user(unsigned long from,int len,void * arg)168 static int strncpy_chunk_from_user(unsigned long from, int len, void *arg)
169 {
170 	char **to_ptr = arg, *to = *to_ptr;
171 	int n;
172 
173 	strncpy(to, (void *) from, len);
174 	n = strnlen(to, len);
175 	*to_ptr += n;
176 
177 	if (n < len)
178 	        return 1;
179 	return 0;
180 }
181 
strncpy_from_user(char * dst,const char __user * src,long count)182 long strncpy_from_user(char *dst, const char __user *src, long count)
183 {
184 	long n;
185 	char *ptr = dst;
186 
187 	if (!access_ok(src, 1))
188 		return -EFAULT;
189 	n = buffer_op((unsigned long) src, count, 0, strncpy_chunk_from_user,
190 		      &ptr);
191 	if (n != 0)
192 		return -EFAULT;
193 	return strnlen(dst, count);
194 }
195 EXPORT_SYMBOL(strncpy_from_user);
196 
clear_chunk(unsigned long addr,int len,void * unused)197 static int clear_chunk(unsigned long addr, int len, void *unused)
198 {
199 	memset((void *) addr, 0, len);
200 	return 0;
201 }
202 
__clear_user(void __user * mem,unsigned long len)203 unsigned long __clear_user(void __user *mem, unsigned long len)
204 {
205 	return buffer_op((unsigned long) mem, len, 1, clear_chunk, NULL);
206 }
207 EXPORT_SYMBOL(__clear_user);
208 
strnlen_chunk(unsigned long str,int len,void * arg)209 static int strnlen_chunk(unsigned long str, int len, void *arg)
210 {
211 	int *len_ptr = arg, n;
212 
213 	n = strnlen((void *) str, len);
214 	*len_ptr += n;
215 
216 	if (n < len)
217 		return 1;
218 	return 0;
219 }
220 
strnlen_user(const char __user * str,long len)221 long strnlen_user(const char __user *str, long len)
222 {
223 	int count = 0, n;
224 
225 	if (!access_ok(str, 1))
226 		return -EFAULT;
227 	n = buffer_op((unsigned long) str, len, 0, strnlen_chunk, &count);
228 	if (n == 0)
229 		return count + 1;
230 	return 0;
231 }
232 EXPORT_SYMBOL(strnlen_user);
233 
234 /**
235  * arch_futex_atomic_op_inuser() - Atomic arithmetic operation with constant
236  *			  argument and comparison of the previous
237  *			  futex value with another constant.
238  *
239  * @encoded_op:	encoded operation to execute
240  * @uaddr:	pointer to user space address
241  *
242  * Return:
243  * 0 - On success
244  * -EFAULT - User access resulted in a page fault
245  * -EAGAIN - Atomic operation was unable to complete due to contention
246  * -ENOSYS - Operation not supported
247  */
248 
arch_futex_atomic_op_inuser(int op,u32 oparg,int * oval,u32 __user * uaddr)249 int arch_futex_atomic_op_inuser(int op, u32 oparg, int *oval, u32 __user *uaddr)
250 {
251 	int oldval, ret;
252 	struct page *page;
253 	unsigned long addr = (unsigned long) uaddr;
254 	pte_t *pte;
255 
256 	ret = -EFAULT;
257 	if (!access_ok(uaddr, sizeof(*uaddr)))
258 		return -EFAULT;
259 	preempt_disable();
260 	pte = maybe_map(addr, 1);
261 	if (pte == NULL)
262 		goto out_inuser;
263 
264 	page = pte_page(*pte);
265 #ifdef CONFIG_64BIT
266 	pagefault_disable();
267 	addr = (unsigned long) page_address(page) +
268 			(((unsigned long) addr) & ~PAGE_MASK);
269 #else
270 	addr = (unsigned long) kmap_atomic(page) +
271 		((unsigned long) addr & ~PAGE_MASK);
272 #endif
273 	uaddr = (u32 *) addr;
274 	oldval = *uaddr;
275 
276 	ret = 0;
277 
278 	switch (op) {
279 	case FUTEX_OP_SET:
280 		*uaddr = oparg;
281 		break;
282 	case FUTEX_OP_ADD:
283 		*uaddr += oparg;
284 		break;
285 	case FUTEX_OP_OR:
286 		*uaddr |= oparg;
287 		break;
288 	case FUTEX_OP_ANDN:
289 		*uaddr &= ~oparg;
290 		break;
291 	case FUTEX_OP_XOR:
292 		*uaddr ^= oparg;
293 		break;
294 	default:
295 		ret = -ENOSYS;
296 	}
297 #ifdef CONFIG_64BIT
298 	pagefault_enable();
299 #else
300 	kunmap_atomic((void *)addr);
301 #endif
302 
303 out_inuser:
304 	preempt_enable();
305 
306 	if (ret == 0)
307 		*oval = oldval;
308 
309 	return ret;
310 }
311 EXPORT_SYMBOL(arch_futex_atomic_op_inuser);
312 
313 /**
314  * futex_atomic_cmpxchg_inatomic() - Compare and exchange the content of the
315  *				uaddr with newval if the current value is
316  *				oldval.
317  * @uval:	pointer to store content of @uaddr
318  * @uaddr:	pointer to user space address
319  * @oldval:	old value
320  * @newval:	new value to store to @uaddr
321  *
322  * Return:
323  * 0 - On success
324  * -EFAULT - User access resulted in a page fault
325  * -EAGAIN - Atomic operation was unable to complete due to contention
326  */
327 
futex_atomic_cmpxchg_inatomic(u32 * uval,u32 __user * uaddr,u32 oldval,u32 newval)328 int futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
329 			      u32 oldval, u32 newval)
330 {
331 	struct page *page;
332 	pte_t *pte;
333 	int ret = -EFAULT;
334 
335 	if (!access_ok(uaddr, sizeof(*uaddr)))
336 		return -EFAULT;
337 
338 	preempt_disable();
339 	pte = maybe_map((unsigned long) uaddr, 1);
340 	if (pte == NULL)
341 		goto out_inatomic;
342 
343 	page = pte_page(*pte);
344 #ifdef CONFIG_64BIT
345 	pagefault_disable();
346 	uaddr = page_address(page) + (((unsigned long) uaddr) & ~PAGE_MASK);
347 #else
348 	uaddr = kmap_atomic(page) + ((unsigned long) uaddr & ~PAGE_MASK);
349 #endif
350 
351 	*uval = *uaddr;
352 
353 	ret = cmpxchg(uaddr, oldval, newval);
354 
355 #ifdef CONFIG_64BIT
356 	pagefault_enable();
357 #else
358 	kunmap_atomic(uaddr);
359 #endif
360 	ret = 0;
361 
362 out_inatomic:
363 	preempt_enable();
364 	return ret;
365 }
366 EXPORT_SYMBOL(futex_atomic_cmpxchg_inatomic);
367