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/cpufeature.h>
22 #include <asm/ptrace.h>
23 #include <asm/memory.h>
24 #include <asm/extable.h>
25
26 #define get_fs() (current_thread_info()->addr_limit)
27
28 static inline void set_fs(mm_segment_t fs)
29 {
30 current_thread_info()->addr_limit = fs;
31
32 /*
33 * Prevent a mispredicted conditional call to set_fs from forwarding
34 * the wrong address limit to access_ok under speculation.
35 */
36 spec_bar();
37
38 /* On user-mode return, check fs is correct */
39 set_thread_flag(TIF_FSCHECK);
40
41 /*
42 * Enable/disable UAO so that copy_to_user() etc can access
43 * kernel memory with the unprivileged instructions.
44 */
45 if (IS_ENABLED(CONFIG_ARM64_UAO) && fs == KERNEL_DS)
46 asm(ALTERNATIVE("nop", SET_PSTATE_UAO(1), ARM64_HAS_UAO));
47 else
48 asm(ALTERNATIVE("nop", SET_PSTATE_UAO(0), ARM64_HAS_UAO,
49 CONFIG_ARM64_UAO));
50 }
51
52 #define segment_eq(a, b) ((a) == (b))
53
54 /*
55 * Test whether a block of memory is a valid user space address.
56 * Returns 1 if the range is valid, 0 otherwise.
57 *
58 * This is equivalent to the following test:
59 * (u65)addr + (u65)size <= (u65)current->addr_limit + 1
60 */
61 static inline unsigned long __range_ok(const void __user *addr, unsigned long size)
62 {
63 unsigned long ret, limit = current_thread_info()->addr_limit;
64
65 /*
66 * Asynchronous I/O running in a kernel thread does not have the
67 * TIF_TAGGED_ADDR flag of the process owning the mm, so always untag
68 * the user address before checking.
69 */
70 if (IS_ENABLED(CONFIG_ARM64_TAGGED_ADDR_ABI) &&
71 (current->flags & PF_KTHREAD || test_thread_flag(TIF_TAGGED_ADDR)))
72 addr = untagged_addr(addr);
73
74 __chk_user_ptr(addr);
75 asm volatile(
76 // A + B <= C + 1 for all A,B,C, in four easy steps:
77 // 1: X = A + B; X' = X % 2^64
78 " adds %0, %3, %2\n"
79 // 2: Set C = 0 if X > 2^64, to guarantee X' > C in step 4
80 " csel %1, xzr, %1, hi\n"
81 // 3: Set X' = ~0 if X >= 2^64. For X == 2^64, this decrements X'
82 // to compensate for the carry flag being set in step 4. For
83 // X > 2^64, X' merely has to remain nonzero, which it does.
84 " csinv %0, %0, xzr, cc\n"
85 // 4: For X < 2^64, this gives us X' - C - 1 <= 0, where the -1
86 // comes from the carry in being clear. Otherwise, we are
87 // testing X' - C == 0, subject to the previous adjustments.
88 " sbcs xzr, %0, %1\n"
89 " cset %0, ls\n"
90 : "=&r" (ret), "+r" (limit) : "Ir" (size), "0" (addr) : "cc");
91
92 return ret;
93 }
94
95 #define access_ok(addr, size) __range_ok(addr, size)
96 #define user_addr_max get_fs
97
98 #define _ASM_EXTABLE(from, to) \
99 " .pushsection __ex_table, \"a\"\n" \
100 " .align 3\n" \
101 " .long (" #from " - .), (" #to " - .)\n" \
102 " .popsection\n"
103
104 /*
105 * User access enabling/disabling.
106 */
107 #ifdef CONFIG_ARM64_SW_TTBR0_PAN
108 static inline void __uaccess_ttbr0_disable(void)
109 {
110 unsigned long flags, ttbr;
111
112 local_irq_save(flags);
113 ttbr = read_sysreg(ttbr1_el1);
114 ttbr &= ~TTBR_ASID_MASK;
115 /* reserved_ttbr0 placed before swapper_pg_dir */
116 write_sysreg(ttbr - RESERVED_TTBR0_SIZE, ttbr0_el1);
117 isb();
118 /* Set reserved ASID */
119 write_sysreg(ttbr, ttbr1_el1);
120 isb();
121 local_irq_restore(flags);
122 }
123
124 static inline void __uaccess_ttbr0_enable(void)
125 {
126 unsigned long flags, ttbr0, ttbr1;
127
128 /*
129 * Disable interrupts to avoid preemption between reading the 'ttbr0'
130 * variable and the MSR. A context switch could trigger an ASID
131 * roll-over and an update of 'ttbr0'.
132 */
133 local_irq_save(flags);
134 ttbr0 = READ_ONCE(current_thread_info()->ttbr0);
135
136 /* Restore active ASID */
137 ttbr1 = read_sysreg(ttbr1_el1);
138 ttbr1 &= ~TTBR_ASID_MASK; /* safety measure */
139 ttbr1 |= ttbr0 & TTBR_ASID_MASK;
140 write_sysreg(ttbr1, ttbr1_el1);
141 isb();
142
143 /* Restore user page table */
144 write_sysreg(ttbr0, ttbr0_el1);
145 isb();
146 local_irq_restore(flags);
147 }
148
149 static inline bool uaccess_ttbr0_disable(void)
150 {
151 if (!system_uses_ttbr0_pan())
152 return false;
153 __uaccess_ttbr0_disable();
154 return true;
155 }
156
157 static inline bool uaccess_ttbr0_enable(void)
158 {
159 if (!system_uses_ttbr0_pan())
160 return false;
161 __uaccess_ttbr0_enable();
162 return true;
163 }
164 #else
165 static inline bool uaccess_ttbr0_disable(void)
166 {
167 return false;
168 }
169
170 static inline bool uaccess_ttbr0_enable(void)
171 {
172 return false;
173 }
174 #endif
175
176 static inline void __uaccess_disable_hw_pan(void)
177 {
178 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_HAS_PAN,
179 CONFIG_ARM64_PAN));
180 }
181
182 static inline void __uaccess_enable_hw_pan(void)
183 {
184 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_HAS_PAN,
185 CONFIG_ARM64_PAN));
186 }
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
202 static inline void uaccess_disable(void)
203 {
204 __uaccess_disable(ARM64_HAS_PAN);
205 }
206
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 */
215 static inline void uaccess_disable_not_uao(void)
216 {
217 __uaccess_disable(ARM64_ALT_PAN_NOT_UAO);
218 }
219
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. In case the pointer is tagged (has the top byte set),
228 * untag the pointer before checking.
229 */
230 #define uaccess_mask_ptr(ptr) (__typeof__(ptr))__uaccess_mask_ptr(ptr)
231 static inline void __user *__uaccess_mask_ptr(const void __user *ptr)
232 {
233 void __user *safe_ptr;
234
235 asm volatile(
236 " bics xzr, %3, %2\n"
237 " csel %0, %1, xzr, eq\n"
238 : "=&r" (safe_ptr)
239 : "r" (ptr), "r" (current_thread_info()->addr_limit),
240 "r" (untagged_addr(ptr))
241 : "cc");
242
243 csdb();
244 return safe_ptr;
245 }
246
247 /*
248 * The "__xxx" versions of the user access functions do not verify the address
249 * space - it must have been done previously with a separate "access_ok()"
250 * call.
251 *
252 * The "__xxx_error" versions set the third argument to -EFAULT if an error
253 * occurs, and leave it unchanged on success.
254 */
255 #define __get_user_asm(instr, alt_instr, reg, x, addr, err, feature) \
256 asm volatile( \
257 "1:"ALTERNATIVE(instr " " reg "1, [%2]\n", \
258 alt_instr " " reg "1, [%2]\n", feature) \
259 "2:\n" \
260 " .section .fixup, \"ax\"\n" \
261 " .align 2\n" \
262 "3: mov %w0, %3\n" \
263 " mov %1, #0\n" \
264 " b 2b\n" \
265 " .previous\n" \
266 _ASM_EXTABLE(1b, 3b) \
267 : "+r" (err), "=&r" (x) \
268 : "r" (addr), "i" (-EFAULT))
269
270 #define __raw_get_user(x, ptr, err) \
271 do { \
272 unsigned long __gu_val; \
273 __chk_user_ptr(ptr); \
274 uaccess_enable_not_uao(); \
275 switch (sizeof(*(ptr))) { \
276 case 1: \
277 __get_user_asm("ldrb", "ldtrb", "%w", __gu_val, (ptr), \
278 (err), ARM64_HAS_UAO); \
279 break; \
280 case 2: \
281 __get_user_asm("ldrh", "ldtrh", "%w", __gu_val, (ptr), \
282 (err), ARM64_HAS_UAO); \
283 break; \
284 case 4: \
285 __get_user_asm("ldr", "ldtr", "%w", __gu_val, (ptr), \
286 (err), ARM64_HAS_UAO); \
287 break; \
288 case 8: \
289 __get_user_asm("ldr", "ldtr", "%x", __gu_val, (ptr), \
290 (err), ARM64_HAS_UAO); \
291 break; \
292 default: \
293 BUILD_BUG(); \
294 } \
295 uaccess_disable_not_uao(); \
296 (x) = (__force __typeof__(*(ptr)))__gu_val; \
297 } while (0)
298
299 #define __get_user_error(x, ptr, err) \
300 do { \
301 __typeof__(*(ptr)) __user *__p = (ptr); \
302 might_fault(); \
303 if (access_ok(__p, sizeof(*__p))) { \
304 __p = uaccess_mask_ptr(__p); \
305 __raw_get_user((x), __p, (err)); \
306 } else { \
307 (x) = 0; (err) = -EFAULT; \
308 } \
309 } while (0)
310
311 #define __get_user(x, ptr) \
312 ({ \
313 int __gu_err = 0; \
314 __get_user_error((x), (ptr), __gu_err); \
315 __gu_err; \
316 })
317
318 #define get_user __get_user
319
320 #define __put_user_asm(instr, alt_instr, reg, x, addr, err, feature) \
321 asm volatile( \
322 "1:"ALTERNATIVE(instr " " reg "1, [%2]\n", \
323 alt_instr " " reg "1, [%2]\n", feature) \
324 "2:\n" \
325 " .section .fixup,\"ax\"\n" \
326 " .align 2\n" \
327 "3: mov %w0, %3\n" \
328 " b 2b\n" \
329 " .previous\n" \
330 _ASM_EXTABLE(1b, 3b) \
331 : "+r" (err) \
332 : "r" (x), "r" (addr), "i" (-EFAULT))
333
334 #define __raw_put_user(x, ptr, err) \
335 do { \
336 __typeof__(*(ptr)) __pu_val = (x); \
337 __chk_user_ptr(ptr); \
338 uaccess_enable_not_uao(); \
339 switch (sizeof(*(ptr))) { \
340 case 1: \
341 __put_user_asm("strb", "sttrb", "%w", __pu_val, (ptr), \
342 (err), ARM64_HAS_UAO); \
343 break; \
344 case 2: \
345 __put_user_asm("strh", "sttrh", "%w", __pu_val, (ptr), \
346 (err), ARM64_HAS_UAO); \
347 break; \
348 case 4: \
349 __put_user_asm("str", "sttr", "%w", __pu_val, (ptr), \
350 (err), ARM64_HAS_UAO); \
351 break; \
352 case 8: \
353 __put_user_asm("str", "sttr", "%x", __pu_val, (ptr), \
354 (err), ARM64_HAS_UAO); \
355 break; \
356 default: \
357 BUILD_BUG(); \
358 } \
359 uaccess_disable_not_uao(); \
360 } while (0)
361
362 #define __put_user_error(x, ptr, err) \
363 do { \
364 __typeof__(*(ptr)) __user *__p = (ptr); \
365 might_fault(); \
366 if (access_ok(__p, sizeof(*__p))) { \
367 __p = uaccess_mask_ptr(__p); \
368 __raw_put_user((x), __p, (err)); \
369 } else { \
370 (err) = -EFAULT; \
371 } \
372 } while (0)
373
374 #define __put_user(x, ptr) \
375 ({ \
376 int __pu_err = 0; \
377 __put_user_error((x), (ptr), __pu_err); \
378 __pu_err; \
379 })
380
381 #define put_user __put_user
382
383 extern unsigned long __must_check __arch_copy_from_user(void *to, const void __user *from, unsigned long n);
384 #define raw_copy_from_user(to, from, n) \
385 ({ \
386 unsigned long __acfu_ret; \
387 uaccess_enable_not_uao(); \
388 __acfu_ret = __arch_copy_from_user((to), \
389 __uaccess_mask_ptr(from), (n)); \
390 uaccess_disable_not_uao(); \
391 __acfu_ret; \
392 })
393
394 extern unsigned long __must_check __arch_copy_to_user(void __user *to, const void *from, unsigned long n);
395 #define raw_copy_to_user(to, from, n) \
396 ({ \
397 unsigned long __actu_ret; \
398 uaccess_enable_not_uao(); \
399 __actu_ret = __arch_copy_to_user(__uaccess_mask_ptr(to), \
400 (from), (n)); \
401 uaccess_disable_not_uao(); \
402 __actu_ret; \
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 unsigned long __aciu_ret; \
409 uaccess_enable_not_uao(); \
410 __aciu_ret = __arch_copy_in_user(__uaccess_mask_ptr(to), \
411 __uaccess_mask_ptr(from), (n)); \
412 uaccess_disable_not_uao(); \
413 __aciu_ret; \
414 })
415
416 #define INLINE_COPY_TO_USER
417 #define INLINE_COPY_FROM_USER
418
419 extern unsigned long __must_check __arch_clear_user(void __user *to, unsigned long n);
420 static inline unsigned long __must_check __clear_user(void __user *to, unsigned long n)
421 {
422 if (access_ok(to, n)) {
423 uaccess_enable_not_uao();
424 n = __arch_clear_user(__uaccess_mask_ptr(to), n);
425 uaccess_disable_not_uao();
426 }
427 return n;
428 }
429 #define clear_user __clear_user
430
431 extern long strncpy_from_user(char *dest, const char __user *src, long count);
432
433 extern __must_check long strnlen_user(const char __user *str, long n);
434
435 #ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
436 struct page;
437 void memcpy_page_flushcache(char *to, struct page *page, size_t offset, size_t len);
438 extern unsigned long __must_check __copy_user_flushcache(void *to, const void __user *from, unsigned long n);
439
440 static inline int __copy_from_user_flushcache(void *dst, const void __user *src, unsigned size)
441 {
442 kasan_check_write(dst, size);
443 return __copy_user_flushcache(dst, __uaccess_mask_ptr(src), size);
444 }
445 #endif
446
447 #endif /* __ASM_UACCESS_H */