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 #include <asm/alternative.h>
22 #include <asm/kernel-pgtable.h>
23 #include <asm/sysreg.h>
24
25 /*
26 * User space memory access functions
27 */
28 #include <linux/bitops.h>
29 #include <linux/kasan-checks.h>
30 #include <linux/string.h>
31
32 #include <asm/cpufeature.h>
33 #include <asm/ptrace.h>
34 #include <asm/memory.h>
35 #include <asm/compiler.h>
36 #include <asm/extable.h>
37
38 #define get_ds() (KERNEL_DS)
39 #define get_fs() (current_thread_info()->addr_limit)
40
set_fs(mm_segment_t fs)41 static inline void set_fs(mm_segment_t fs)
42 {
43 current_thread_info()->addr_limit = fs;
44
45 /*
46 * Prevent a mispredicted conditional call to set_fs from forwarding
47 * the wrong address limit to access_ok under speculation.
48 */
49 dsb(nsh);
50 isb();
51
52 /* On user-mode return, check fs is correct */
53 set_thread_flag(TIF_FSCHECK);
54
55 /*
56 * Enable/disable UAO so that copy_to_user() etc can access
57 * kernel memory with the unprivileged instructions.
58 */
59 if (IS_ENABLED(CONFIG_ARM64_UAO) && fs == KERNEL_DS)
60 asm(ALTERNATIVE("nop", SET_PSTATE_UAO(1), ARM64_HAS_UAO));
61 else
62 asm(ALTERNATIVE("nop", SET_PSTATE_UAO(0), ARM64_HAS_UAO,
63 CONFIG_ARM64_UAO));
64 }
65
66 #define segment_eq(a, b) ((a) == (b))
67
68 /*
69 * Test whether a block of memory is a valid user space address.
70 * Returns 1 if the range is valid, 0 otherwise.
71 *
72 * This is equivalent to the following test:
73 * (u65)addr + (u65)size <= (u65)current->addr_limit + 1
74 */
__range_ok(unsigned long addr,unsigned long size)75 static inline unsigned long __range_ok(unsigned long addr, unsigned long size)
76 {
77 unsigned long limit = current_thread_info()->addr_limit;
78
79 __chk_user_ptr(addr);
80 asm volatile(
81 // A + B <= C + 1 for all A,B,C, in four easy steps:
82 // 1: X = A + B; X' = X % 2^64
83 " adds %0, %0, %2\n"
84 // 2: Set C = 0 if X > 2^64, to guarantee X' > C in step 4
85 " csel %1, xzr, %1, hi\n"
86 // 3: Set X' = ~0 if X >= 2^64. For X == 2^64, this decrements X'
87 // to compensate for the carry flag being set in step 4. For
88 // X > 2^64, X' merely has to remain nonzero, which it does.
89 " csinv %0, %0, xzr, cc\n"
90 // 4: For X < 2^64, this gives us X' - C - 1 <= 0, where the -1
91 // comes from the carry in being clear. Otherwise, we are
92 // testing X' - C == 0, subject to the previous adjustments.
93 " sbcs xzr, %0, %1\n"
94 " cset %0, ls\n"
95 : "+r" (addr), "+r" (limit) : "Ir" (size) : "cc");
96
97 return addr;
98 }
99
100 /*
101 * When dealing with data aborts, watchpoints, or instruction traps we may end
102 * up with a tagged userland pointer. Clear the tag to get a sane pointer to
103 * pass on to access_ok(), for instance.
104 */
105 #define untagged_addr(addr) sign_extend64(addr, 55)
106
107 #define access_ok(type, addr, size) __range_ok((unsigned long)(addr), size)
108 #define user_addr_max get_fs
109
110 #define _ASM_EXTABLE(from, to) \
111 " .pushsection __ex_table, \"a\"\n" \
112 " .align 3\n" \
113 " .long (" #from " - .), (" #to " - .)\n" \
114 " .popsection\n"
115
116 /*
117 * User access enabling/disabling.
118 */
119 #ifdef CONFIG_ARM64_SW_TTBR0_PAN
__uaccess_ttbr0_disable(void)120 static inline void __uaccess_ttbr0_disable(void)
121 {
122 unsigned long flags, ttbr;
123
124 local_irq_save(flags);
125 ttbr = read_sysreg(ttbr1_el1);
126 ttbr &= ~TTBR_ASID_MASK;
127 /* reserved_ttbr0 placed at the end of swapper_pg_dir */
128 write_sysreg(ttbr + SWAPPER_DIR_SIZE, ttbr0_el1);
129 isb();
130 /* Set reserved ASID */
131 write_sysreg(ttbr, ttbr1_el1);
132 isb();
133 local_irq_restore(flags);
134 }
135
__uaccess_ttbr0_enable(void)136 static inline void __uaccess_ttbr0_enable(void)
137 {
138 unsigned long flags, ttbr0, ttbr1;
139
140 /*
141 * Disable interrupts to avoid preemption between reading the 'ttbr0'
142 * variable and the MSR. A context switch could trigger an ASID
143 * roll-over and an update of 'ttbr0'.
144 */
145 local_irq_save(flags);
146 ttbr0 = READ_ONCE(current_thread_info()->ttbr0);
147
148 /* Restore active ASID */
149 ttbr1 = read_sysreg(ttbr1_el1);
150 ttbr1 &= ~TTBR_ASID_MASK; /* safety measure */
151 ttbr1 |= ttbr0 & TTBR_ASID_MASK;
152 write_sysreg(ttbr1, ttbr1_el1);
153 isb();
154
155 /* Restore user page table */
156 write_sysreg(ttbr0, ttbr0_el1);
157 isb();
158 local_irq_restore(flags);
159 }
160
uaccess_ttbr0_disable(void)161 static inline bool uaccess_ttbr0_disable(void)
162 {
163 if (!system_uses_ttbr0_pan())
164 return false;
165 __uaccess_ttbr0_disable();
166 return true;
167 }
168
uaccess_ttbr0_enable(void)169 static inline bool uaccess_ttbr0_enable(void)
170 {
171 if (!system_uses_ttbr0_pan())
172 return false;
173 __uaccess_ttbr0_enable();
174 return true;
175 }
176 #else
uaccess_ttbr0_disable(void)177 static inline bool uaccess_ttbr0_disable(void)
178 {
179 return false;
180 }
181
uaccess_ttbr0_enable(void)182 static inline bool uaccess_ttbr0_enable(void)
183 {
184 return false;
185 }
186 #endif
187
188 #define __uaccess_disable(alt) \
189 do { \
190 if (!uaccess_ttbr0_disable()) \
191 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), alt, \
192 CONFIG_ARM64_PAN)); \
193 } while (0)
194
195 #define __uaccess_enable(alt) \
196 do { \
197 if (!uaccess_ttbr0_enable()) \
198 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), alt, \
199 CONFIG_ARM64_PAN)); \
200 } while (0)
201
uaccess_disable(void)202 static inline void uaccess_disable(void)
203 {
204 __uaccess_disable(ARM64_HAS_PAN);
205 }
206
uaccess_enable(void)207 static inline void uaccess_enable(void)
208 {
209 __uaccess_enable(ARM64_HAS_PAN);
210 }
211
212 /*
213 * These functions are no-ops when UAO is present.
214 */
uaccess_disable_not_uao(void)215 static inline void uaccess_disable_not_uao(void)
216 {
217 __uaccess_disable(ARM64_ALT_PAN_NOT_UAO);
218 }
219
uaccess_enable_not_uao(void)220 static inline void uaccess_enable_not_uao(void)
221 {
222 __uaccess_enable(ARM64_ALT_PAN_NOT_UAO);
223 }
224
225 /*
226 * Sanitise a uaccess pointer such that it becomes NULL if above the
227 * current addr_limit.
228 */
229 #define uaccess_mask_ptr(ptr) (__typeof__(ptr))__uaccess_mask_ptr(ptr)
__uaccess_mask_ptr(const void __user * ptr)230 static inline void __user *__uaccess_mask_ptr(const void __user *ptr)
231 {
232 void __user *safe_ptr;
233
234 asm volatile(
235 " bics xzr, %1, %2\n"
236 " csel %0, %1, xzr, eq\n"
237 : "=&r" (safe_ptr)
238 : "r" (ptr), "r" (current_thread_info()->addr_limit)
239 : "cc");
240
241 csdb();
242 return safe_ptr;
243 }
244
245 /*
246 * The "__xxx" versions of the user access functions do not verify the address
247 * space - it must have been done previously with a separate "access_ok()"
248 * call.
249 *
250 * The "__xxx_error" versions set the third argument to -EFAULT if an error
251 * occurs, and leave it unchanged on success.
252 */
253 #define __get_user_asm(instr, alt_instr, reg, x, addr, err, feature) \
254 asm volatile( \
255 "1:"ALTERNATIVE(instr " " reg "1, [%2]\n", \
256 alt_instr " " reg "1, [%2]\n", feature) \
257 "2:\n" \
258 " .section .fixup, \"ax\"\n" \
259 " .align 2\n" \
260 "3: mov %w0, %3\n" \
261 " mov %1, #0\n" \
262 " b 2b\n" \
263 " .previous\n" \
264 _ASM_EXTABLE(1b, 3b) \
265 : "+r" (err), "=&r" (x) \
266 : "r" (addr), "i" (-EFAULT))
267
268 #define __get_user_err(x, ptr, err) \
269 do { \
270 unsigned long __gu_val; \
271 __chk_user_ptr(ptr); \
272 uaccess_enable_not_uao(); \
273 switch (sizeof(*(ptr))) { \
274 case 1: \
275 __get_user_asm("ldrb", "ldtrb", "%w", __gu_val, (ptr), \
276 (err), ARM64_HAS_UAO); \
277 break; \
278 case 2: \
279 __get_user_asm("ldrh", "ldtrh", "%w", __gu_val, (ptr), \
280 (err), ARM64_HAS_UAO); \
281 break; \
282 case 4: \
283 __get_user_asm("ldr", "ldtr", "%w", __gu_val, (ptr), \
284 (err), ARM64_HAS_UAO); \
285 break; \
286 case 8: \
287 __get_user_asm("ldr", "ldtr", "%x", __gu_val, (ptr), \
288 (err), ARM64_HAS_UAO); \
289 break; \
290 default: \
291 BUILD_BUG(); \
292 } \
293 uaccess_disable_not_uao(); \
294 (x) = (__force __typeof__(*(ptr)))__gu_val; \
295 } while (0)
296
297 #define __get_user_check(x, ptr, err) \
298 ({ \
299 __typeof__(*(ptr)) __user *__p = (ptr); \
300 might_fault(); \
301 if (access_ok(VERIFY_READ, __p, sizeof(*__p))) { \
302 __p = uaccess_mask_ptr(__p); \
303 __get_user_err((x), __p, (err)); \
304 } else { \
305 (x) = 0; (err) = -EFAULT; \
306 } \
307 })
308
309 #define __get_user_error(x, ptr, err) \
310 ({ \
311 __get_user_check((x), (ptr), (err)); \
312 (void)0; \
313 })
314
315 #define __get_user(x, ptr) \
316 ({ \
317 int __gu_err = 0; \
318 __get_user_check((x), (ptr), __gu_err); \
319 __gu_err; \
320 })
321
322 #define get_user __get_user
323
324 #define __put_user_asm(instr, alt_instr, reg, x, addr, err, feature) \
325 asm volatile( \
326 "1:"ALTERNATIVE(instr " " reg "1, [%2]\n", \
327 alt_instr " " reg "1, [%2]\n", feature) \
328 "2:\n" \
329 " .section .fixup,\"ax\"\n" \
330 " .align 2\n" \
331 "3: mov %w0, %3\n" \
332 " b 2b\n" \
333 " .previous\n" \
334 _ASM_EXTABLE(1b, 3b) \
335 : "+r" (err) \
336 : "r" (x), "r" (addr), "i" (-EFAULT))
337
338 #define __put_user_err(x, ptr, err) \
339 do { \
340 __typeof__(*(ptr)) __pu_val = (x); \
341 __chk_user_ptr(ptr); \
342 uaccess_enable_not_uao(); \
343 switch (sizeof(*(ptr))) { \
344 case 1: \
345 __put_user_asm("strb", "sttrb", "%w", __pu_val, (ptr), \
346 (err), ARM64_HAS_UAO); \
347 break; \
348 case 2: \
349 __put_user_asm("strh", "sttrh", "%w", __pu_val, (ptr), \
350 (err), ARM64_HAS_UAO); \
351 break; \
352 case 4: \
353 __put_user_asm("str", "sttr", "%w", __pu_val, (ptr), \
354 (err), ARM64_HAS_UAO); \
355 break; \
356 case 8: \
357 __put_user_asm("str", "sttr", "%x", __pu_val, (ptr), \
358 (err), ARM64_HAS_UAO); \
359 break; \
360 default: \
361 BUILD_BUG(); \
362 } \
363 uaccess_disable_not_uao(); \
364 } while (0)
365
366 #define __put_user_check(x, ptr, err) \
367 ({ \
368 __typeof__(*(ptr)) __user *__p = (ptr); \
369 might_fault(); \
370 if (access_ok(VERIFY_WRITE, __p, sizeof(*__p))) { \
371 __p = uaccess_mask_ptr(__p); \
372 __put_user_err((x), __p, (err)); \
373 } else { \
374 (err) = -EFAULT; \
375 } \
376 })
377
378 #define __put_user_error(x, ptr, err) \
379 ({ \
380 __put_user_check((x), (ptr), (err)); \
381 (void)0; \
382 })
383
384 #define __put_user(x, ptr) \
385 ({ \
386 int __pu_err = 0; \
387 __put_user_check((x), (ptr), __pu_err); \
388 __pu_err; \
389 })
390
391 #define put_user __put_user
392
393 extern unsigned long __must_check __arch_copy_from_user(void *to, const void __user *from, unsigned long n);
394 #define raw_copy_from_user(to, from, n) \
395 ({ \
396 __arch_copy_from_user((to), __uaccess_mask_ptr(from), (n)); \
397 })
398
399 extern unsigned long __must_check __arch_copy_to_user(void __user *to, const void *from, unsigned long n);
400 #define raw_copy_to_user(to, from, n) \
401 ({ \
402 __arch_copy_to_user(__uaccess_mask_ptr(to), (from), (n)); \
403 })
404
405 extern unsigned long __must_check __arch_copy_in_user(void __user *to, const void __user *from, unsigned long n);
406 #define raw_copy_in_user(to, from, n) \
407 ({ \
408 __arch_copy_in_user(__uaccess_mask_ptr(to), \
409 __uaccess_mask_ptr(from), (n)); \
410 })
411
412 #define INLINE_COPY_TO_USER
413 #define INLINE_COPY_FROM_USER
414
415 extern unsigned long __must_check __arch_clear_user(void __user *to, unsigned long n);
__clear_user(void __user * to,unsigned long n)416 static inline unsigned long __must_check __clear_user(void __user *to, unsigned long n)
417 {
418 if (access_ok(VERIFY_WRITE, to, n))
419 n = __arch_clear_user(__uaccess_mask_ptr(to), n);
420 return n;
421 }
422 #define clear_user __clear_user
423
424 extern long strncpy_from_user(char *dest, const char __user *src, long count);
425
426 extern __must_check long strnlen_user(const char __user *str, long n);
427
428 #ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
429 struct page;
430 void memcpy_page_flushcache(char *to, struct page *page, size_t offset, size_t len);
431 extern unsigned long __must_check __copy_user_flushcache(void *to, const void __user *from, unsigned long n);
432
__copy_from_user_flushcache(void * dst,const void __user * src,unsigned size)433 static inline int __copy_from_user_flushcache(void *dst, const void __user *src, unsigned size)
434 {
435 kasan_check_write(dst, size);
436 return __copy_user_flushcache(dst, __uaccess_mask_ptr(src), size);
437 }
438 #endif
439
440 #endif /* __ASM_UACCESS_H */
441