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
set_fs(mm_segment_t fs)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 */
__range_ok(const void __user * addr,unsigned long size)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 if (IS_ENABLED(CONFIG_ARM64_TAGGED_ADDR_ABI) &&
66 test_thread_flag(TIF_TAGGED_ADDR))
67 addr = untagged_addr(addr);
68
69 __chk_user_ptr(addr);
70 asm volatile(
71 // A + B <= C + 1 for all A,B,C, in four easy steps:
72 // 1: X = A + B; X' = X % 2^64
73 " adds %0, %3, %2\n"
74 // 2: Set C = 0 if X > 2^64, to guarantee X' > C in step 4
75 " csel %1, xzr, %1, hi\n"
76 // 3: Set X' = ~0 if X >= 2^64. For X == 2^64, this decrements X'
77 // to compensate for the carry flag being set in step 4. For
78 // X > 2^64, X' merely has to remain nonzero, which it does.
79 " csinv %0, %0, xzr, cc\n"
80 // 4: For X < 2^64, this gives us X' - C - 1 <= 0, where the -1
81 // comes from the carry in being clear. Otherwise, we are
82 // testing X' - C == 0, subject to the previous adjustments.
83 " sbcs xzr, %0, %1\n"
84 " cset %0, ls\n"
85 : "=&r" (ret), "+r" (limit) : "Ir" (size), "0" (addr) : "cc");
86
87 return ret;
88 }
89
90 #define access_ok(addr, size) __range_ok(addr, size)
91 #define user_addr_max get_fs
92
93 #define _ASM_EXTABLE(from, to) \
94 " .pushsection __ex_table, \"a\"\n" \
95 " .align 3\n" \
96 " .long (" #from " - .), (" #to " - .)\n" \
97 " .popsection\n"
98
99 /*
100 * User access enabling/disabling.
101 */
102 #ifdef CONFIG_ARM64_SW_TTBR0_PAN
__uaccess_ttbr0_disable(void)103 static inline void __uaccess_ttbr0_disable(void)
104 {
105 unsigned long flags, ttbr;
106
107 local_irq_save(flags);
108 ttbr = read_sysreg(ttbr1_el1);
109 ttbr &= ~TTBR_ASID_MASK;
110 /* reserved_ttbr0 placed before swapper_pg_dir */
111 write_sysreg(ttbr - RESERVED_TTBR0_SIZE, ttbr0_el1);
112 isb();
113 /* Set reserved ASID */
114 write_sysreg(ttbr, ttbr1_el1);
115 isb();
116 local_irq_restore(flags);
117 }
118
__uaccess_ttbr0_enable(void)119 static inline void __uaccess_ttbr0_enable(void)
120 {
121 unsigned long flags, ttbr0, ttbr1;
122
123 /*
124 * Disable interrupts to avoid preemption between reading the 'ttbr0'
125 * variable and the MSR. A context switch could trigger an ASID
126 * roll-over and an update of 'ttbr0'.
127 */
128 local_irq_save(flags);
129 ttbr0 = READ_ONCE(current_thread_info()->ttbr0);
130
131 /* Restore active ASID */
132 ttbr1 = read_sysreg(ttbr1_el1);
133 ttbr1 &= ~TTBR_ASID_MASK; /* safety measure */
134 ttbr1 |= ttbr0 & TTBR_ASID_MASK;
135 write_sysreg(ttbr1, ttbr1_el1);
136 isb();
137
138 /* Restore user page table */
139 write_sysreg(ttbr0, ttbr0_el1);
140 isb();
141 local_irq_restore(flags);
142 }
143
uaccess_ttbr0_disable(void)144 static inline bool uaccess_ttbr0_disable(void)
145 {
146 if (!system_uses_ttbr0_pan())
147 return false;
148 __uaccess_ttbr0_disable();
149 return true;
150 }
151
uaccess_ttbr0_enable(void)152 static inline bool uaccess_ttbr0_enable(void)
153 {
154 if (!system_uses_ttbr0_pan())
155 return false;
156 __uaccess_ttbr0_enable();
157 return true;
158 }
159 #else
uaccess_ttbr0_disable(void)160 static inline bool uaccess_ttbr0_disable(void)
161 {
162 return false;
163 }
164
uaccess_ttbr0_enable(void)165 static inline bool uaccess_ttbr0_enable(void)
166 {
167 return false;
168 }
169 #endif
170
__uaccess_disable_hw_pan(void)171 static inline void __uaccess_disable_hw_pan(void)
172 {
173 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_HAS_PAN,
174 CONFIG_ARM64_PAN));
175 }
176
__uaccess_enable_hw_pan(void)177 static inline void __uaccess_enable_hw_pan(void)
178 {
179 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_HAS_PAN,
180 CONFIG_ARM64_PAN));
181 }
182
183 #define __uaccess_disable(alt) \
184 do { \
185 if (!uaccess_ttbr0_disable()) \
186 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), alt, \
187 CONFIG_ARM64_PAN)); \
188 } while (0)
189
190 #define __uaccess_enable(alt) \
191 do { \
192 if (!uaccess_ttbr0_enable()) \
193 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), alt, \
194 CONFIG_ARM64_PAN)); \
195 } while (0)
196
uaccess_disable(void)197 static inline void uaccess_disable(void)
198 {
199 __uaccess_disable(ARM64_HAS_PAN);
200 }
201
uaccess_enable(void)202 static inline void uaccess_enable(void)
203 {
204 __uaccess_enable(ARM64_HAS_PAN);
205 }
206
207 /*
208 * These functions are no-ops when UAO is present.
209 */
uaccess_disable_not_uao(void)210 static inline void uaccess_disable_not_uao(void)
211 {
212 __uaccess_disable(ARM64_ALT_PAN_NOT_UAO);
213 }
214
uaccess_enable_not_uao(void)215 static inline void uaccess_enable_not_uao(void)
216 {
217 __uaccess_enable(ARM64_ALT_PAN_NOT_UAO);
218 }
219
220 /*
221 * Sanitise a uaccess pointer such that it becomes NULL if above the
222 * current addr_limit. In case the pointer is tagged (has the top byte set),
223 * untag the pointer before checking.
224 */
225 #define uaccess_mask_ptr(ptr) (__typeof__(ptr))__uaccess_mask_ptr(ptr)
__uaccess_mask_ptr(const void __user * ptr)226 static inline void __user *__uaccess_mask_ptr(const void __user *ptr)
227 {
228 void __user *safe_ptr;
229
230 asm volatile(
231 " bics xzr, %3, %2\n"
232 " csel %0, %1, xzr, eq\n"
233 : "=&r" (safe_ptr)
234 : "r" (ptr), "r" (current_thread_info()->addr_limit),
235 "r" (untagged_addr(ptr))
236 : "cc");
237
238 csdb();
239 return safe_ptr;
240 }
241
242 /*
243 * The "__xxx" versions of the user access functions do not verify the address
244 * space - it must have been done previously with a separate "access_ok()"
245 * call.
246 *
247 * The "__xxx_error" versions set the third argument to -EFAULT if an error
248 * occurs, and leave it unchanged on success.
249 */
250 #define __get_user_asm(instr, alt_instr, reg, x, addr, err, feature) \
251 asm volatile( \
252 "1:"ALTERNATIVE(instr " " reg "1, [%2]\n", \
253 alt_instr " " reg "1, [%2]\n", feature) \
254 "2:\n" \
255 " .section .fixup, \"ax\"\n" \
256 " .align 2\n" \
257 "3: mov %w0, %3\n" \
258 " mov %1, #0\n" \
259 " b 2b\n" \
260 " .previous\n" \
261 _ASM_EXTABLE(1b, 3b) \
262 : "+r" (err), "=&r" (x) \
263 : "r" (addr), "i" (-EFAULT))
264
265 #define __raw_get_user(x, ptr, err) \
266 do { \
267 unsigned long __gu_val; \
268 __chk_user_ptr(ptr); \
269 uaccess_enable_not_uao(); \
270 switch (sizeof(*(ptr))) { \
271 case 1: \
272 __get_user_asm("ldrb", "ldtrb", "%w", __gu_val, (ptr), \
273 (err), ARM64_HAS_UAO); \
274 break; \
275 case 2: \
276 __get_user_asm("ldrh", "ldtrh", "%w", __gu_val, (ptr), \
277 (err), ARM64_HAS_UAO); \
278 break; \
279 case 4: \
280 __get_user_asm("ldr", "ldtr", "%w", __gu_val, (ptr), \
281 (err), ARM64_HAS_UAO); \
282 break; \
283 case 8: \
284 __get_user_asm("ldr", "ldtr", "%x", __gu_val, (ptr), \
285 (err), ARM64_HAS_UAO); \
286 break; \
287 default: \
288 BUILD_BUG(); \
289 } \
290 uaccess_disable_not_uao(); \
291 (x) = (__force __typeof__(*(ptr)))__gu_val; \
292 } while (0)
293
294 #define __get_user_error(x, ptr, err) \
295 do { \
296 __typeof__(*(ptr)) __user *__p = (ptr); \
297 might_fault(); \
298 if (access_ok(__p, sizeof(*__p))) { \
299 __p = uaccess_mask_ptr(__p); \
300 __raw_get_user((x), __p, (err)); \
301 } else { \
302 (x) = 0; (err) = -EFAULT; \
303 } \
304 } while (0)
305
306 #define __get_user(x, ptr) \
307 ({ \
308 int __gu_err = 0; \
309 __get_user_error((x), (ptr), __gu_err); \
310 __gu_err; \
311 })
312
313 #define get_user __get_user
314
315 #define __put_user_asm(instr, alt_instr, reg, x, addr, err, feature) \
316 asm volatile( \
317 "1:"ALTERNATIVE(instr " " reg "1, [%2]\n", \
318 alt_instr " " reg "1, [%2]\n", feature) \
319 "2:\n" \
320 " .section .fixup,\"ax\"\n" \
321 " .align 2\n" \
322 "3: mov %w0, %3\n" \
323 " b 2b\n" \
324 " .previous\n" \
325 _ASM_EXTABLE(1b, 3b) \
326 : "+r" (err) \
327 : "r" (x), "r" (addr), "i" (-EFAULT))
328
329 #define __raw_put_user(x, ptr, err) \
330 do { \
331 __typeof__(*(ptr)) __pu_val = (x); \
332 __chk_user_ptr(ptr); \
333 uaccess_enable_not_uao(); \
334 switch (sizeof(*(ptr))) { \
335 case 1: \
336 __put_user_asm("strb", "sttrb", "%w", __pu_val, (ptr), \
337 (err), ARM64_HAS_UAO); \
338 break; \
339 case 2: \
340 __put_user_asm("strh", "sttrh", "%w", __pu_val, (ptr), \
341 (err), ARM64_HAS_UAO); \
342 break; \
343 case 4: \
344 __put_user_asm("str", "sttr", "%w", __pu_val, (ptr), \
345 (err), ARM64_HAS_UAO); \
346 break; \
347 case 8: \
348 __put_user_asm("str", "sttr", "%x", __pu_val, (ptr), \
349 (err), ARM64_HAS_UAO); \
350 break; \
351 default: \
352 BUILD_BUG(); \
353 } \
354 uaccess_disable_not_uao(); \
355 } while (0)
356
357 #define __put_user_error(x, ptr, err) \
358 do { \
359 __typeof__(*(ptr)) __user *__p = (ptr); \
360 might_fault(); \
361 if (access_ok(__p, sizeof(*__p))) { \
362 __p = uaccess_mask_ptr(__p); \
363 __raw_put_user((x), __p, (err)); \
364 } else { \
365 (err) = -EFAULT; \
366 } \
367 } while (0)
368
369 #define __put_user(x, ptr) \
370 ({ \
371 int __pu_err = 0; \
372 __put_user_error((x), (ptr), __pu_err); \
373 __pu_err; \
374 })
375
376 #define put_user __put_user
377
378 extern unsigned long __must_check __arch_copy_from_user(void *to, const void __user *from, unsigned long n);
379 #define raw_copy_from_user(to, from, n) \
380 ({ \
381 unsigned long __acfu_ret; \
382 uaccess_enable_not_uao(); \
383 __acfu_ret = __arch_copy_from_user((to), \
384 __uaccess_mask_ptr(from), (n)); \
385 uaccess_disable_not_uao(); \
386 __acfu_ret; \
387 })
388
389 extern unsigned long __must_check __arch_copy_to_user(void __user *to, const void *from, unsigned long n);
390 #define raw_copy_to_user(to, from, n) \
391 ({ \
392 unsigned long __actu_ret; \
393 uaccess_enable_not_uao(); \
394 __actu_ret = __arch_copy_to_user(__uaccess_mask_ptr(to), \
395 (from), (n)); \
396 uaccess_disable_not_uao(); \
397 __actu_ret; \
398 })
399
400 extern unsigned long __must_check __arch_copy_in_user(void __user *to, const void __user *from, unsigned long n);
401 #define raw_copy_in_user(to, from, n) \
402 ({ \
403 unsigned long __aciu_ret; \
404 uaccess_enable_not_uao(); \
405 __aciu_ret = __arch_copy_in_user(__uaccess_mask_ptr(to), \
406 __uaccess_mask_ptr(from), (n)); \
407 uaccess_disable_not_uao(); \
408 __aciu_ret; \
409 })
410
411 #define INLINE_COPY_TO_USER
412 #define INLINE_COPY_FROM_USER
413
414 extern unsigned long __must_check __arch_clear_user(void __user *to, unsigned long n);
__clear_user(void __user * to,unsigned long n)415 static inline unsigned long __must_check __clear_user(void __user *to, unsigned long n)
416 {
417 if (access_ok(to, n)) {
418 uaccess_enable_not_uao();
419 n = __arch_clear_user(__uaccess_mask_ptr(to), n);
420 uaccess_disable_not_uao();
421 }
422 return n;
423 }
424 #define clear_user __clear_user
425
426 extern long strncpy_from_user(char *dest, const char __user *src, long count);
427
428 extern __must_check long strnlen_user(const char __user *str, long n);
429
430 #ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
431 struct page;
432 void memcpy_page_flushcache(char *to, struct page *page, size_t offset, size_t len);
433 extern unsigned long __must_check __copy_user_flushcache(void *to, const void __user *from, unsigned long n);
434
__copy_from_user_flushcache(void * dst,const void __user * src,unsigned size)435 static inline int __copy_from_user_flushcache(void *dst, const void __user *src, unsigned size)
436 {
437 kasan_check_write(dst, size);
438 return __copy_user_flushcache(dst, __uaccess_mask_ptr(src), size);
439 }
440 #endif
441
442 #endif /* __ASM_UACCESS_H */
443
