xref: /openbmc/linux/arch/arm64/include/asm/uaccess.h (revision 92a76f6d)
1 /*
2  * Based on arch/arm/include/asm/uaccess.h
3  *
4  * Copyright (C) 2012 ARM Ltd.
5  *
6  * This program is free software; you can redistribute it and/or modify
7  * it under the terms of the GNU General Public License version 2 as
8  * published by the Free Software Foundation.
9  *
10  * This program is distributed in the hope that it will be useful,
11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13  * GNU General Public License for more details.
14  *
15  * You should have received a copy of the GNU General Public License
16  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
17  */
18 #ifndef __ASM_UACCESS_H
19 #define __ASM_UACCESS_H
20 
21 /*
22  * User space memory access functions
23  */
24 #include <linux/string.h>
25 #include <linux/thread_info.h>
26 
27 #include <asm/alternative.h>
28 #include <asm/cpufeature.h>
29 #include <asm/ptrace.h>
30 #include <asm/sysreg.h>
31 #include <asm/errno.h>
32 #include <asm/memory.h>
33 #include <asm/compiler.h>
34 
35 #define VERIFY_READ 0
36 #define VERIFY_WRITE 1
37 
38 /*
39  * The exception table consists of pairs of relative offsets: the first
40  * is the relative offset to an instruction that is allowed to fault,
41  * and the second is the relative offset at which the program should
42  * continue. No registers are modified, so it is entirely up to the
43  * continuation code to figure out what to do.
44  *
45  * All the routines below use bits of fixup code that are out of line
46  * with the main instruction path.  This means when everything is well,
47  * we don't even have to jump over them.  Further, they do not intrude
48  * on our cache or tlb entries.
49  */
50 
51 struct exception_table_entry
52 {
53 	int insn, fixup;
54 };
55 
56 #define ARCH_HAS_RELATIVE_EXTABLE
57 
58 extern int fixup_exception(struct pt_regs *regs);
59 
60 #define KERNEL_DS	(-1UL)
61 #define get_ds()	(KERNEL_DS)
62 
63 #define USER_DS		TASK_SIZE_64
64 #define get_fs()	(current_thread_info()->addr_limit)
65 
66 static inline void set_fs(mm_segment_t fs)
67 {
68 	current_thread_info()->addr_limit = fs;
69 
70 	/*
71 	 * Enable/disable UAO so that copy_to_user() etc can access
72 	 * kernel memory with the unprivileged instructions.
73 	 */
74 	if (IS_ENABLED(CONFIG_ARM64_UAO) && fs == KERNEL_DS)
75 		asm(ALTERNATIVE("nop", SET_PSTATE_UAO(1), ARM64_HAS_UAO));
76 	else
77 		asm(ALTERNATIVE("nop", SET_PSTATE_UAO(0), ARM64_HAS_UAO,
78 				CONFIG_ARM64_UAO));
79 }
80 
81 #define segment_eq(a, b)	((a) == (b))
82 
83 /*
84  * Return 1 if addr < current->addr_limit, 0 otherwise.
85  */
86 #define __addr_ok(addr)							\
87 ({									\
88 	unsigned long flag;						\
89 	asm("cmp %1, %0; cset %0, lo"					\
90 		: "=&r" (flag)						\
91 		: "r" (addr), "0" (current_thread_info()->addr_limit)	\
92 		: "cc");						\
93 	flag;								\
94 })
95 
96 /*
97  * Test whether a block of memory is a valid user space address.
98  * Returns 1 if the range is valid, 0 otherwise.
99  *
100  * This is equivalent to the following test:
101  * (u65)addr + (u65)size <= current->addr_limit
102  *
103  * This needs 65-bit arithmetic.
104  */
105 #define __range_ok(addr, size)						\
106 ({									\
107 	unsigned long flag, roksum;					\
108 	__chk_user_ptr(addr);						\
109 	asm("adds %1, %1, %3; ccmp %1, %4, #2, cc; cset %0, ls"		\
110 		: "=&r" (flag), "=&r" (roksum)				\
111 		: "1" (addr), "Ir" (size),				\
112 		  "r" (current_thread_info()->addr_limit)		\
113 		: "cc");						\
114 	flag;								\
115 })
116 
117 #define access_ok(type, addr, size)	__range_ok(addr, size)
118 #define user_addr_max			get_fs
119 
120 #define _ASM_EXTABLE(from, to)						\
121 	"	.pushsection	__ex_table, \"a\"\n"			\
122 	"	.align		3\n"					\
123 	"	.long		(" #from " - .), (" #to " - .)\n"	\
124 	"	.popsection\n"
125 
126 /*
127  * The "__xxx" versions of the user access functions do not verify the address
128  * space - it must have been done previously with a separate "access_ok()"
129  * call.
130  *
131  * The "__xxx_error" versions set the third argument to -EFAULT if an error
132  * occurs, and leave it unchanged on success.
133  */
134 #define __get_user_asm(instr, alt_instr, reg, x, addr, err, feature)	\
135 	asm volatile(							\
136 	"1:"ALTERNATIVE(instr "     " reg "1, [%2]\n",			\
137 			alt_instr " " reg "1, [%2]\n", feature)		\
138 	"2:\n"								\
139 	"	.section .fixup, \"ax\"\n"				\
140 	"	.align	2\n"						\
141 	"3:	mov	%w0, %3\n"					\
142 	"	mov	%1, #0\n"					\
143 	"	b	2b\n"						\
144 	"	.previous\n"						\
145 	_ASM_EXTABLE(1b, 3b)						\
146 	: "+r" (err), "=&r" (x)						\
147 	: "r" (addr), "i" (-EFAULT))
148 
149 #define __get_user_err(x, ptr, err)					\
150 do {									\
151 	unsigned long __gu_val;						\
152 	__chk_user_ptr(ptr);						\
153 	asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_ALT_PAN_NOT_UAO,\
154 			CONFIG_ARM64_PAN));				\
155 	switch (sizeof(*(ptr))) {					\
156 	case 1:								\
157 		__get_user_asm("ldrb", "ldtrb", "%w", __gu_val, (ptr),  \
158 			       (err), ARM64_HAS_UAO);			\
159 		break;							\
160 	case 2:								\
161 		__get_user_asm("ldrh", "ldtrh", "%w", __gu_val, (ptr),  \
162 			       (err), ARM64_HAS_UAO);			\
163 		break;							\
164 	case 4:								\
165 		__get_user_asm("ldr", "ldtr", "%w", __gu_val, (ptr),	\
166 			       (err), ARM64_HAS_UAO);			\
167 		break;							\
168 	case 8:								\
169 		__get_user_asm("ldr", "ldtr", "%",  __gu_val, (ptr),	\
170 			       (err), ARM64_HAS_UAO);			\
171 		break;							\
172 	default:							\
173 		BUILD_BUG();						\
174 	}								\
175 	(x) = (__force __typeof__(*(ptr)))__gu_val;			\
176 	asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_ALT_PAN_NOT_UAO,\
177 			CONFIG_ARM64_PAN));				\
178 } while (0)
179 
180 #define __get_user(x, ptr)						\
181 ({									\
182 	int __gu_err = 0;						\
183 	__get_user_err((x), (ptr), __gu_err);				\
184 	__gu_err;							\
185 })
186 
187 #define __get_user_error(x, ptr, err)					\
188 ({									\
189 	__get_user_err((x), (ptr), (err));				\
190 	(void)0;							\
191 })
192 
193 #define __get_user_unaligned __get_user
194 
195 #define get_user(x, ptr)						\
196 ({									\
197 	__typeof__(*(ptr)) __user *__p = (ptr);				\
198 	might_fault();							\
199 	access_ok(VERIFY_READ, __p, sizeof(*__p)) ?			\
200 		__get_user((x), __p) :					\
201 		((x) = 0, -EFAULT);					\
202 })
203 
204 #define __put_user_asm(instr, alt_instr, reg, x, addr, err, feature)	\
205 	asm volatile(							\
206 	"1:"ALTERNATIVE(instr "     " reg "1, [%2]\n",			\
207 			alt_instr " " reg "1, [%2]\n", feature)		\
208 	"2:\n"								\
209 	"	.section .fixup,\"ax\"\n"				\
210 	"	.align	2\n"						\
211 	"3:	mov	%w0, %3\n"					\
212 	"	b	2b\n"						\
213 	"	.previous\n"						\
214 	_ASM_EXTABLE(1b, 3b)						\
215 	: "+r" (err)							\
216 	: "r" (x), "r" (addr), "i" (-EFAULT))
217 
218 #define __put_user_err(x, ptr, err)					\
219 do {									\
220 	__typeof__(*(ptr)) __pu_val = (x);				\
221 	__chk_user_ptr(ptr);						\
222 	asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_ALT_PAN_NOT_UAO,\
223 			CONFIG_ARM64_PAN));				\
224 	switch (sizeof(*(ptr))) {					\
225 	case 1:								\
226 		__put_user_asm("strb", "sttrb", "%w", __pu_val, (ptr),	\
227 			       (err), ARM64_HAS_UAO);			\
228 		break;							\
229 	case 2:								\
230 		__put_user_asm("strh", "sttrh", "%w", __pu_val, (ptr),	\
231 			       (err), ARM64_HAS_UAO);			\
232 		break;							\
233 	case 4:								\
234 		__put_user_asm("str", "sttr", "%w", __pu_val, (ptr),	\
235 			       (err), ARM64_HAS_UAO);			\
236 		break;							\
237 	case 8:								\
238 		__put_user_asm("str", "sttr", "%", __pu_val, (ptr),	\
239 			       (err), ARM64_HAS_UAO);			\
240 		break;							\
241 	default:							\
242 		BUILD_BUG();						\
243 	}								\
244 	asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_ALT_PAN_NOT_UAO,\
245 			CONFIG_ARM64_PAN));				\
246 } while (0)
247 
248 #define __put_user(x, ptr)						\
249 ({									\
250 	int __pu_err = 0;						\
251 	__put_user_err((x), (ptr), __pu_err);				\
252 	__pu_err;							\
253 })
254 
255 #define __put_user_error(x, ptr, err)					\
256 ({									\
257 	__put_user_err((x), (ptr), (err));				\
258 	(void)0;							\
259 })
260 
261 #define __put_user_unaligned __put_user
262 
263 #define put_user(x, ptr)						\
264 ({									\
265 	__typeof__(*(ptr)) __user *__p = (ptr);				\
266 	might_fault();							\
267 	access_ok(VERIFY_WRITE, __p, sizeof(*__p)) ?			\
268 		__put_user((x), __p) :					\
269 		-EFAULT;						\
270 })
271 
272 extern unsigned long __must_check __copy_from_user(void *to, const void __user *from, unsigned long n);
273 extern unsigned long __must_check __copy_to_user(void __user *to, const void *from, unsigned long n);
274 extern unsigned long __must_check __copy_in_user(void __user *to, const void __user *from, unsigned long n);
275 extern unsigned long __must_check __clear_user(void __user *addr, unsigned long n);
276 
277 static inline unsigned long __must_check copy_from_user(void *to, const void __user *from, unsigned long n)
278 {
279 	if (access_ok(VERIFY_READ, from, n))
280 		n = __copy_from_user(to, from, n);
281 	else /* security hole - plug it */
282 		memset(to, 0, n);
283 	return n;
284 }
285 
286 static inline unsigned long __must_check copy_to_user(void __user *to, const void *from, unsigned long n)
287 {
288 	if (access_ok(VERIFY_WRITE, to, n))
289 		n = __copy_to_user(to, from, n);
290 	return n;
291 }
292 
293 static inline unsigned long __must_check copy_in_user(void __user *to, const void __user *from, unsigned long n)
294 {
295 	if (access_ok(VERIFY_READ, from, n) && access_ok(VERIFY_WRITE, to, n))
296 		n = __copy_in_user(to, from, n);
297 	return n;
298 }
299 
300 #define __copy_to_user_inatomic __copy_to_user
301 #define __copy_from_user_inatomic __copy_from_user
302 
303 static inline unsigned long __must_check clear_user(void __user *to, unsigned long n)
304 {
305 	if (access_ok(VERIFY_WRITE, to, n))
306 		n = __clear_user(to, n);
307 	return n;
308 }
309 
310 extern long strncpy_from_user(char *dest, const char __user *src, long count);
311 
312 extern __must_check long strlen_user(const char __user *str);
313 extern __must_check long strnlen_user(const char __user *str, long n);
314 
315 #endif /* __ASM_UACCESS_H */
316