1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /*
3 * Based on arch/arm/include/asm/uaccess.h
4 *
5 * Copyright (C) 2012 ARM Ltd.
6 */
7 #ifndef __ASM_UACCESS_H
8 #define __ASM_UACCESS_H
9
10 #include <asm/alternative.h>
11 #include <asm/kernel-pgtable.h>
12 #include <asm/sysreg.h>
13
14 /*
15 * User space memory access functions
16 */
17 #include <linux/bitops.h>
18 #include <linux/kasan-checks.h>
19 #include <linux/string.h>
20
21 #include <asm/asm-extable.h>
22 #include <asm/cpufeature.h>
23 #include <asm/mmu.h>
24 #include <asm/mte.h>
25 #include <asm/ptrace.h>
26 #include <asm/memory.h>
27 #include <asm/extable.h>
28
29 static inline int __access_ok(const void __user *ptr, unsigned long size);
30
31 /*
32 * Test whether a block of memory is a valid user space address.
33 * Returns 1 if the range is valid, 0 otherwise.
34 *
35 * This is equivalent to the following test:
36 * (u65)addr + (u65)size <= (u65)TASK_SIZE_MAX
37 */
access_ok(const void __user * addr,unsigned long size)38 static inline int access_ok(const void __user *addr, unsigned long size)
39 {
40 /*
41 * Asynchronous I/O running in a kernel thread does not have the
42 * TIF_TAGGED_ADDR flag of the process owning the mm, so always untag
43 * the user address before checking.
44 */
45 if (IS_ENABLED(CONFIG_ARM64_TAGGED_ADDR_ABI) &&
46 (current->flags & PF_KTHREAD || test_thread_flag(TIF_TAGGED_ADDR)))
47 addr = untagged_addr(addr);
48
49 return likely(__access_ok(addr, size));
50 }
51 #define access_ok access_ok
52
53 #include <asm-generic/access_ok.h>
54
55 /*
56 * User access enabling/disabling.
57 */
58 #ifdef CONFIG_ARM64_SW_TTBR0_PAN
__uaccess_ttbr0_disable(void)59 static inline void __uaccess_ttbr0_disable(void)
60 {
61 unsigned long flags, ttbr;
62
63 local_irq_save(flags);
64 ttbr = read_sysreg(ttbr1_el1);
65 ttbr &= ~TTBR_ASID_MASK;
66 /* reserved_pg_dir placed before swapper_pg_dir */
67 write_sysreg(ttbr - RESERVED_SWAPPER_OFFSET, ttbr0_el1);
68 /* Set reserved ASID */
69 write_sysreg(ttbr, ttbr1_el1);
70 isb();
71 local_irq_restore(flags);
72 }
73
__uaccess_ttbr0_enable(void)74 static inline void __uaccess_ttbr0_enable(void)
75 {
76 unsigned long flags, ttbr0, ttbr1;
77
78 /*
79 * Disable interrupts to avoid preemption between reading the 'ttbr0'
80 * variable and the MSR. A context switch could trigger an ASID
81 * roll-over and an update of 'ttbr0'.
82 */
83 local_irq_save(flags);
84 ttbr0 = READ_ONCE(current_thread_info()->ttbr0);
85
86 /* Restore active ASID */
87 ttbr1 = read_sysreg(ttbr1_el1);
88 ttbr1 &= ~TTBR_ASID_MASK; /* safety measure */
89 ttbr1 |= ttbr0 & TTBR_ASID_MASK;
90 write_sysreg(ttbr1, ttbr1_el1);
91
92 /* Restore user page table */
93 write_sysreg(ttbr0, ttbr0_el1);
94 isb();
95 local_irq_restore(flags);
96 }
97
uaccess_ttbr0_disable(void)98 static inline bool uaccess_ttbr0_disable(void)
99 {
100 if (!system_uses_ttbr0_pan())
101 return false;
102 __uaccess_ttbr0_disable();
103 return true;
104 }
105
uaccess_ttbr0_enable(void)106 static inline bool uaccess_ttbr0_enable(void)
107 {
108 if (!system_uses_ttbr0_pan())
109 return false;
110 __uaccess_ttbr0_enable();
111 return true;
112 }
113 #else
uaccess_ttbr0_disable(void)114 static inline bool uaccess_ttbr0_disable(void)
115 {
116 return false;
117 }
118
uaccess_ttbr0_enable(void)119 static inline bool uaccess_ttbr0_enable(void)
120 {
121 return false;
122 }
123 #endif
124
__uaccess_disable_hw_pan(void)125 static inline void __uaccess_disable_hw_pan(void)
126 {
127 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_HAS_PAN,
128 CONFIG_ARM64_PAN));
129 }
130
__uaccess_enable_hw_pan(void)131 static inline void __uaccess_enable_hw_pan(void)
132 {
133 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_HAS_PAN,
134 CONFIG_ARM64_PAN));
135 }
136
uaccess_disable_privileged(void)137 static inline void uaccess_disable_privileged(void)
138 {
139 mte_disable_tco();
140
141 if (uaccess_ttbr0_disable())
142 return;
143
144 __uaccess_enable_hw_pan();
145 }
146
uaccess_enable_privileged(void)147 static inline void uaccess_enable_privileged(void)
148 {
149 mte_enable_tco();
150
151 if (uaccess_ttbr0_enable())
152 return;
153
154 __uaccess_disable_hw_pan();
155 }
156
157 /*
158 * Sanitize a uaccess pointer such that it cannot reach any kernel address.
159 *
160 * Clearing bit 55 ensures the pointer cannot address any portion of the TTBR1
161 * address range (i.e. any kernel address), and either the pointer falls within
162 * the TTBR0 address range or must cause a fault.
163 */
164 #define uaccess_mask_ptr(ptr) (__typeof__(ptr))__uaccess_mask_ptr(ptr)
__uaccess_mask_ptr(const void __user * ptr)165 static inline void __user *__uaccess_mask_ptr(const void __user *ptr)
166 {
167 void __user *safe_ptr;
168
169 asm volatile(
170 " bic %0, %1, %2\n"
171 : "=r" (safe_ptr)
172 : "r" (ptr),
173 "i" (BIT(55))
174 );
175
176 return safe_ptr;
177 }
178
179 /*
180 * The "__xxx" versions of the user access functions do not verify the address
181 * space - it must have been done previously with a separate "access_ok()"
182 * call.
183 *
184 * The "__xxx_error" versions set the third argument to -EFAULT if an error
185 * occurs, and leave it unchanged on success.
186 */
187 #ifdef CONFIG_CC_HAS_ASM_GOTO_OUTPUT
188 #define __get_mem_asm(load, reg, x, addr, label, type) \
189 asm_goto_output( \
190 "1: " load " " reg "0, [%1]\n" \
191 _ASM_EXTABLE_##type##ACCESS(1b, %l2) \
192 : "=r" (x) \
193 : "r" (addr) : : label)
194 #else
195 #define __get_mem_asm(load, reg, x, addr, label, type) do { \
196 int __gma_err = 0; \
197 asm volatile( \
198 "1: " load " " reg "1, [%2]\n" \
199 "2:\n" \
200 _ASM_EXTABLE_##type##ACCESS_ERR_ZERO(1b, 2b, %w0, %w1) \
201 : "+r" (__gma_err), "=r" (x) \
202 : "r" (addr)); \
203 if (__gma_err) goto label; } while (0)
204 #endif
205
206 #define __raw_get_mem(ldr, x, ptr, label, type) \
207 do { \
208 unsigned long __gu_val; \
209 switch (sizeof(*(ptr))) { \
210 case 1: \
211 __get_mem_asm(ldr "b", "%w", __gu_val, (ptr), label, type); \
212 break; \
213 case 2: \
214 __get_mem_asm(ldr "h", "%w", __gu_val, (ptr), label, type); \
215 break; \
216 case 4: \
217 __get_mem_asm(ldr, "%w", __gu_val, (ptr), label, type); \
218 break; \
219 case 8: \
220 __get_mem_asm(ldr, "%x", __gu_val, (ptr), label, type); \
221 break; \
222 default: \
223 BUILD_BUG(); \
224 } \
225 (x) = (__force __typeof__(*(ptr)))__gu_val; \
226 } while (0)
227
228 /*
229 * We must not call into the scheduler between uaccess_ttbr0_enable() and
230 * uaccess_ttbr0_disable(). As `x` and `ptr` could contain blocking functions,
231 * we must evaluate these outside of the critical section.
232 */
233 #define __raw_get_user(x, ptr, label) \
234 do { \
235 __typeof__(*(ptr)) __user *__rgu_ptr = (ptr); \
236 __typeof__(x) __rgu_val; \
237 __chk_user_ptr(ptr); \
238 do { \
239 __label__ __rgu_failed; \
240 uaccess_ttbr0_enable(); \
241 __raw_get_mem("ldtr", __rgu_val, __rgu_ptr, __rgu_failed, U); \
242 uaccess_ttbr0_disable(); \
243 (x) = __rgu_val; \
244 break; \
245 __rgu_failed: \
246 uaccess_ttbr0_disable(); \
247 goto label; \
248 } while (0); \
249 } while (0)
250
251 #define __get_user_error(x, ptr, err) \
252 do { \
253 __label__ __gu_failed; \
254 __typeof__(*(ptr)) __user *__p = (ptr); \
255 might_fault(); \
256 if (access_ok(__p, sizeof(*__p))) { \
257 __p = uaccess_mask_ptr(__p); \
258 __raw_get_user((x), __p, __gu_failed); \
259 } else { \
260 __gu_failed: \
261 (x) = (__force __typeof__(x))0; (err) = -EFAULT; \
262 } \
263 } while (0)
264
265 #define __get_user(x, ptr) \
266 ({ \
267 int __gu_err = 0; \
268 __get_user_error((x), (ptr), __gu_err); \
269 __gu_err; \
270 })
271
272 #define get_user __get_user
273
274 /*
275 * We must not call into the scheduler between __mte_enable_tco_async() and
276 * __mte_disable_tco_async(). As `dst` and `src` may contain blocking
277 * functions, we must evaluate these outside of the critical section.
278 */
279 #define __get_kernel_nofault(dst, src, type, err_label) \
280 do { \
281 __typeof__(dst) __gkn_dst = (dst); \
282 __typeof__(src) __gkn_src = (src); \
283 do { \
284 __label__ __gkn_label; \
285 \
286 __mte_enable_tco_async(); \
287 __raw_get_mem("ldr", *((type *)(__gkn_dst)), \
288 (__force type *)(__gkn_src), __gkn_label, K); \
289 __mte_disable_tco_async(); \
290 break; \
291 __gkn_label: \
292 __mte_disable_tco_async(); \
293 goto err_label; \
294 } while (0); \
295 } while (0)
296
297 #define __put_mem_asm(store, reg, x, addr, label, type) \
298 asm goto( \
299 "1: " store " " reg "0, [%1]\n" \
300 "2:\n" \
301 _ASM_EXTABLE_##type##ACCESS(1b, %l2) \
302 : : "rZ" (x), "r" (addr) : : label)
303
304 #define __raw_put_mem(str, x, ptr, label, type) \
305 do { \
306 __typeof__(*(ptr)) __pu_val = (x); \
307 switch (sizeof(*(ptr))) { \
308 case 1: \
309 __put_mem_asm(str "b", "%w", __pu_val, (ptr), label, type); \
310 break; \
311 case 2: \
312 __put_mem_asm(str "h", "%w", __pu_val, (ptr), label, type); \
313 break; \
314 case 4: \
315 __put_mem_asm(str, "%w", __pu_val, (ptr), label, type); \
316 break; \
317 case 8: \
318 __put_mem_asm(str, "%x", __pu_val, (ptr), label, type); \
319 break; \
320 default: \
321 BUILD_BUG(); \
322 } \
323 } while (0)
324
325 /*
326 * We must not call into the scheduler between uaccess_ttbr0_enable() and
327 * uaccess_ttbr0_disable(). As `x` and `ptr` could contain blocking functions,
328 * we must evaluate these outside of the critical section.
329 */
330 #define __raw_put_user(x, ptr, label) \
331 do { \
332 __label__ __rpu_failed; \
333 __typeof__(*(ptr)) __user *__rpu_ptr = (ptr); \
334 __typeof__(*(ptr)) __rpu_val = (x); \
335 __chk_user_ptr(__rpu_ptr); \
336 \
337 do { \
338 uaccess_ttbr0_enable(); \
339 __raw_put_mem("sttr", __rpu_val, __rpu_ptr, __rpu_failed, U); \
340 uaccess_ttbr0_disable(); \
341 break; \
342 __rpu_failed: \
343 uaccess_ttbr0_disable(); \
344 goto label; \
345 } while (0); \
346 } while (0)
347
348 #define __put_user_error(x, ptr, err) \
349 do { \
350 __label__ __pu_failed; \
351 __typeof__(*(ptr)) __user *__p = (ptr); \
352 might_fault(); \
353 if (access_ok(__p, sizeof(*__p))) { \
354 __p = uaccess_mask_ptr(__p); \
355 __raw_put_user((x), __p, __pu_failed); \
356 } else { \
357 __pu_failed: \
358 (err) = -EFAULT; \
359 } \
360 } while (0)
361
362 #define __put_user(x, ptr) \
363 ({ \
364 int __pu_err = 0; \
365 __put_user_error((x), (ptr), __pu_err); \
366 __pu_err; \
367 })
368
369 #define put_user __put_user
370
371 /*
372 * We must not call into the scheduler between __mte_enable_tco_async() and
373 * __mte_disable_tco_async(). As `dst` and `src` may contain blocking
374 * functions, we must evaluate these outside of the critical section.
375 */
376 #define __put_kernel_nofault(dst, src, type, err_label) \
377 do { \
378 __typeof__(dst) __pkn_dst = (dst); \
379 __typeof__(src) __pkn_src = (src); \
380 \
381 do { \
382 __label__ __pkn_err; \
383 __mte_enable_tco_async(); \
384 __raw_put_mem("str", *((type *)(__pkn_src)), \
385 (__force type *)(__pkn_dst), __pkn_err, K); \
386 __mte_disable_tco_async(); \
387 break; \
388 __pkn_err: \
389 __mte_disable_tco_async(); \
390 goto err_label; \
391 } while (0); \
392 } while(0)
393
394 extern unsigned long __must_check __arch_copy_from_user(void *to, const void __user *from, unsigned long n);
395 #define raw_copy_from_user(to, from, n) \
396 ({ \
397 unsigned long __acfu_ret; \
398 uaccess_ttbr0_enable(); \
399 __acfu_ret = __arch_copy_from_user((to), \
400 __uaccess_mask_ptr(from), (n)); \
401 uaccess_ttbr0_disable(); \
402 __acfu_ret; \
403 })
404
405 extern unsigned long __must_check __arch_copy_to_user(void __user *to, const void *from, unsigned long n);
406 #define raw_copy_to_user(to, from, n) \
407 ({ \
408 unsigned long __actu_ret; \
409 uaccess_ttbr0_enable(); \
410 __actu_ret = __arch_copy_to_user(__uaccess_mask_ptr(to), \
411 (from), (n)); \
412 uaccess_ttbr0_disable(); \
413 __actu_ret; \
414 })
415
user_access_begin(const void __user * ptr,size_t len)416 static __must_check __always_inline bool user_access_begin(const void __user *ptr, size_t len)
417 {
418 if (unlikely(!access_ok(ptr,len)))
419 return 0;
420 uaccess_ttbr0_enable();
421 return 1;
422 }
423 #define user_access_begin(a,b) user_access_begin(a,b)
424 #define user_access_end() uaccess_ttbr0_disable()
425 #define unsafe_put_user(x, ptr, label) \
426 __raw_put_mem("sttr", x, uaccess_mask_ptr(ptr), label, U)
427 #define unsafe_get_user(x, ptr, label) \
428 __raw_get_mem("ldtr", x, uaccess_mask_ptr(ptr), label, U)
429
430 /*
431 * KCSAN uses these to save and restore ttbr state.
432 * We do not support KCSAN with ARM64_SW_TTBR0_PAN, so
433 * they are no-ops.
434 */
user_access_save(void)435 static inline unsigned long user_access_save(void) { return 0; }
user_access_restore(unsigned long enabled)436 static inline void user_access_restore(unsigned long enabled) { }
437
438 /*
439 * We want the unsafe accessors to always be inlined and use
440 * the error labels - thus the macro games.
441 */
442 #define unsafe_copy_loop(dst, src, len, type, label) \
443 while (len >= sizeof(type)) { \
444 unsafe_put_user(*(type *)(src),(type __user *)(dst),label); \
445 dst += sizeof(type); \
446 src += sizeof(type); \
447 len -= sizeof(type); \
448 }
449
450 #define unsafe_copy_to_user(_dst,_src,_len,label) \
451 do { \
452 char __user *__ucu_dst = (_dst); \
453 const char *__ucu_src = (_src); \
454 size_t __ucu_len = (_len); \
455 unsafe_copy_loop(__ucu_dst, __ucu_src, __ucu_len, u64, label); \
456 unsafe_copy_loop(__ucu_dst, __ucu_src, __ucu_len, u32, label); \
457 unsafe_copy_loop(__ucu_dst, __ucu_src, __ucu_len, u16, label); \
458 unsafe_copy_loop(__ucu_dst, __ucu_src, __ucu_len, u8, label); \
459 } while (0)
460
461 #define INLINE_COPY_TO_USER
462 #define INLINE_COPY_FROM_USER
463
464 extern unsigned long __must_check __arch_clear_user(void __user *to, unsigned long n);
__clear_user(void __user * to,unsigned long n)465 static inline unsigned long __must_check __clear_user(void __user *to, unsigned long n)
466 {
467 if (access_ok(to, n)) {
468 uaccess_ttbr0_enable();
469 n = __arch_clear_user(__uaccess_mask_ptr(to), n);
470 uaccess_ttbr0_disable();
471 }
472 return n;
473 }
474 #define clear_user __clear_user
475
476 extern long strncpy_from_user(char *dest, const char __user *src, long count);
477
478 extern __must_check long strnlen_user(const char __user *str, long n);
479
480 #ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
481 extern unsigned long __must_check __copy_user_flushcache(void *to, const void __user *from, unsigned long n);
482
__copy_from_user_flushcache(void * dst,const void __user * src,unsigned size)483 static inline int __copy_from_user_flushcache(void *dst, const void __user *src, unsigned size)
484 {
485 kasan_check_write(dst, size);
486 return __copy_user_flushcache(dst, __uaccess_mask_ptr(src), size);
487 }
488 #endif
489
490 #ifdef CONFIG_ARCH_HAS_SUBPAGE_FAULTS
491
492 /*
493 * Return 0 on success, the number of bytes not probed otherwise.
494 */
probe_subpage_writeable(const char __user * uaddr,size_t size)495 static inline size_t probe_subpage_writeable(const char __user *uaddr,
496 size_t size)
497 {
498 if (!system_supports_mte())
499 return 0;
500 return mte_probe_user_range(uaddr, size);
501 }
502
503 #endif /* CONFIG_ARCH_HAS_SUBPAGE_FAULTS */
504
505 #endif /* __ASM_UACCESS_H */
506