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/mmu.h>
23 #include <asm/ptrace.h>
24 #include <asm/memory.h>
25 #include <asm/extable.h>
26
27 #define get_fs() (current_thread_info()->addr_limit)
28
set_fs(mm_segment_t fs)29 static inline void set_fs(mm_segment_t fs)
30 {
31 current_thread_info()->addr_limit = fs;
32
33 /*
34 * Prevent a mispredicted conditional call to set_fs from forwarding
35 * the wrong address limit to access_ok under speculation.
36 */
37 spec_bar();
38
39 /* On user-mode return, check fs is correct */
40 set_thread_flag(TIF_FSCHECK);
41
42 /*
43 * Enable/disable UAO so that copy_to_user() etc can access
44 * kernel memory with the unprivileged instructions.
45 */
46 if (IS_ENABLED(CONFIG_ARM64_UAO) && fs == KERNEL_DS)
47 asm(ALTERNATIVE("nop", SET_PSTATE_UAO(1), ARM64_HAS_UAO));
48 else
49 asm(ALTERNATIVE("nop", SET_PSTATE_UAO(0), ARM64_HAS_UAO,
50 CONFIG_ARM64_UAO));
51 }
52
53 #define uaccess_kernel() (get_fs() == KERNEL_DS)
54
55 /*
56 * Test whether a block of memory is a valid user space address.
57 * Returns 1 if the range is valid, 0 otherwise.
58 *
59 * This is equivalent to the following test:
60 * (u65)addr + (u65)size <= (u65)current->addr_limit + 1
61 */
__range_ok(const void __user * addr,unsigned long size)62 static inline unsigned long __range_ok(const void __user *addr, unsigned long size)
63 {
64 unsigned long ret, limit = current_thread_info()->addr_limit;
65
66 /*
67 * Asynchronous I/O running in a kernel thread does not have the
68 * TIF_TAGGED_ADDR flag of the process owning the mm, so always untag
69 * the user address before checking.
70 */
71 if (IS_ENABLED(CONFIG_ARM64_TAGGED_ADDR_ABI) &&
72 (current->flags & PF_KTHREAD || test_thread_flag(TIF_TAGGED_ADDR)))
73 addr = untagged_addr(addr);
74
75 __chk_user_ptr(addr);
76 asm volatile(
77 // A + B <= C + 1 for all A,B,C, in four easy steps:
78 // 1: X = A + B; X' = X % 2^64
79 " adds %0, %3, %2\n"
80 // 2: Set C = 0 if X > 2^64, to guarantee X' > C in step 4
81 " csel %1, xzr, %1, hi\n"
82 // 3: Set X' = ~0 if X >= 2^64. For X == 2^64, this decrements X'
83 // to compensate for the carry flag being set in step 4. For
84 // X > 2^64, X' merely has to remain nonzero, which it does.
85 " csinv %0, %0, xzr, cc\n"
86 // 4: For X < 2^64, this gives us X' - C - 1 <= 0, where the -1
87 // comes from the carry in being clear. Otherwise, we are
88 // testing X' - C == 0, subject to the previous adjustments.
89 " sbcs xzr, %0, %1\n"
90 " cset %0, ls\n"
91 : "=&r" (ret), "+r" (limit) : "Ir" (size), "0" (addr) : "cc");
92
93 return ret;
94 }
95
96 #define access_ok(addr, size) __range_ok(addr, size)
97 #define user_addr_max get_fs
98
99 #define _ASM_EXTABLE(from, to) \
100 " .pushsection __ex_table, \"a\"\n" \
101 " .align 3\n" \
102 " .long (" #from " - .), (" #to " - .)\n" \
103 " .popsection\n"
104
105 /*
106 * User access enabling/disabling.
107 */
108 #ifdef CONFIG_ARM64_SW_TTBR0_PAN
__uaccess_ttbr0_disable(void)109 static inline void __uaccess_ttbr0_disable(void)
110 {
111 unsigned long flags, ttbr;
112
113 local_irq_save(flags);
114 ttbr = read_sysreg(ttbr1_el1);
115 ttbr &= ~TTBR_ASID_MASK;
116 /* reserved_ttbr0 placed before swapper_pg_dir */
117 write_sysreg(ttbr - RESERVED_TTBR0_SIZE, ttbr0_el1);
118 isb();
119 /* Set reserved ASID */
120 write_sysreg(ttbr, ttbr1_el1);
121 isb();
122 local_irq_restore(flags);
123 }
124
__uaccess_ttbr0_enable(void)125 static inline void __uaccess_ttbr0_enable(void)
126 {
127 unsigned long flags, ttbr0, ttbr1;
128
129 /*
130 * Disable interrupts to avoid preemption between reading the 'ttbr0'
131 * variable and the MSR. A context switch could trigger an ASID
132 * roll-over and an update of 'ttbr0'.
133 */
134 local_irq_save(flags);
135 ttbr0 = READ_ONCE(current_thread_info()->ttbr0);
136
137 /* Restore active ASID */
138 ttbr1 = read_sysreg(ttbr1_el1);
139 ttbr1 &= ~TTBR_ASID_MASK; /* safety measure */
140 ttbr1 |= ttbr0 & TTBR_ASID_MASK;
141 write_sysreg(ttbr1, ttbr1_el1);
142 isb();
143
144 /* Restore user page table */
145 write_sysreg(ttbr0, ttbr0_el1);
146 isb();
147 local_irq_restore(flags);
148 }
149
uaccess_ttbr0_disable(void)150 static inline bool uaccess_ttbr0_disable(void)
151 {
152 if (!system_uses_ttbr0_pan())
153 return false;
154 __uaccess_ttbr0_disable();
155 return true;
156 }
157
uaccess_ttbr0_enable(void)158 static inline bool uaccess_ttbr0_enable(void)
159 {
160 if (!system_uses_ttbr0_pan())
161 return false;
162 __uaccess_ttbr0_enable();
163 return true;
164 }
165 #else
uaccess_ttbr0_disable(void)166 static inline bool uaccess_ttbr0_disable(void)
167 {
168 return false;
169 }
170
uaccess_ttbr0_enable(void)171 static inline bool uaccess_ttbr0_enable(void)
172 {
173 return false;
174 }
175 #endif
176
__uaccess_disable_hw_pan(void)177 static inline void __uaccess_disable_hw_pan(void)
178 {
179 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_HAS_PAN,
180 CONFIG_ARM64_PAN));
181 }
182
__uaccess_enable_hw_pan(void)183 static inline void __uaccess_enable_hw_pan(void)
184 {
185 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_HAS_PAN,
186 CONFIG_ARM64_PAN));
187 }
188
189 #define __uaccess_disable(alt) \
190 do { \
191 if (!uaccess_ttbr0_disable()) \
192 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), alt, \
193 CONFIG_ARM64_PAN)); \
194 } while (0)
195
196 #define __uaccess_enable(alt) \
197 do { \
198 if (!uaccess_ttbr0_enable()) \
199 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), alt, \
200 CONFIG_ARM64_PAN)); \
201 } while (0)
202
uaccess_disable(void)203 static inline void uaccess_disable(void)
204 {
205 __uaccess_disable(ARM64_HAS_PAN);
206 }
207
uaccess_enable(void)208 static inline void uaccess_enable(void)
209 {
210 __uaccess_enable(ARM64_HAS_PAN);
211 }
212
213 /*
214 * These functions are no-ops when UAO is present.
215 */
uaccess_disable_not_uao(void)216 static inline void uaccess_disable_not_uao(void)
217 {
218 __uaccess_disable(ARM64_ALT_PAN_NOT_UAO);
219 }
220
uaccess_enable_not_uao(void)221 static inline void uaccess_enable_not_uao(void)
222 {
223 __uaccess_enable(ARM64_ALT_PAN_NOT_UAO);
224 }
225
226 /*
227 * Sanitise a uaccess pointer such that it becomes NULL if above the
228 * current addr_limit. In case the pointer is tagged (has the top byte set),
229 * untag the pointer before checking.
230 */
231 #define uaccess_mask_ptr(ptr) (__typeof__(ptr))__uaccess_mask_ptr(ptr)
__uaccess_mask_ptr(const void __user * ptr)232 static inline void __user *__uaccess_mask_ptr(const void __user *ptr)
233 {
234 void __user *safe_ptr;
235
236 asm volatile(
237 " bics xzr, %3, %2\n"
238 " csel %0, %1, xzr, eq\n"
239 : "=&r" (safe_ptr)
240 : "r" (ptr), "r" (current_thread_info()->addr_limit),
241 "r" (untagged_addr(ptr))
242 : "cc");
243
244 csdb();
245 return safe_ptr;
246 }
247
248 /*
249 * The "__xxx" versions of the user access functions do not verify the address
250 * space - it must have been done previously with a separate "access_ok()"
251 * call.
252 *
253 * The "__xxx_error" versions set the third argument to -EFAULT if an error
254 * occurs, and leave it unchanged on success.
255 */
256 #define __get_user_asm(instr, alt_instr, reg, x, addr, err, feature) \
257 asm volatile( \
258 "1:"ALTERNATIVE(instr " " reg "1, [%2]\n", \
259 alt_instr " " reg "1, [%2]\n", feature) \
260 "2:\n" \
261 " .section .fixup, \"ax\"\n" \
262 " .align 2\n" \
263 "3: mov %w0, %3\n" \
264 " mov %1, #0\n" \
265 " b 2b\n" \
266 " .previous\n" \
267 _ASM_EXTABLE(1b, 3b) \
268 : "+r" (err), "=&r" (x) \
269 : "r" (addr), "i" (-EFAULT))
270
271 #define __raw_get_user(x, ptr, err) \
272 do { \
273 unsigned long __gu_val; \
274 __chk_user_ptr(ptr); \
275 uaccess_enable_not_uao(); \
276 switch (sizeof(*(ptr))) { \
277 case 1: \
278 __get_user_asm("ldrb", "ldtrb", "%w", __gu_val, (ptr), \
279 (err), ARM64_HAS_UAO); \
280 break; \
281 case 2: \
282 __get_user_asm("ldrh", "ldtrh", "%w", __gu_val, (ptr), \
283 (err), ARM64_HAS_UAO); \
284 break; \
285 case 4: \
286 __get_user_asm("ldr", "ldtr", "%w", __gu_val, (ptr), \
287 (err), ARM64_HAS_UAO); \
288 break; \
289 case 8: \
290 __get_user_asm("ldr", "ldtr", "%x", __gu_val, (ptr), \
291 (err), ARM64_HAS_UAO); \
292 break; \
293 default: \
294 BUILD_BUG(); \
295 } \
296 uaccess_disable_not_uao(); \
297 (x) = (__force __typeof__(*(ptr)))__gu_val; \
298 } while (0)
299
300 #define __get_user_error(x, ptr, err) \
301 do { \
302 __typeof__(*(ptr)) __user *__p = (ptr); \
303 might_fault(); \
304 if (access_ok(__p, sizeof(*__p))) { \
305 __p = uaccess_mask_ptr(__p); \
306 __raw_get_user((x), __p, (err)); \
307 } else { \
308 (x) = (__force __typeof__(x))0; (err) = -EFAULT; \
309 } \
310 } while (0)
311
312 #define __get_user(x, ptr) \
313 ({ \
314 int __gu_err = 0; \
315 __get_user_error((x), (ptr), __gu_err); \
316 __gu_err; \
317 })
318
319 #define get_user __get_user
320
321 #define __put_user_asm(instr, alt_instr, reg, x, addr, err, feature) \
322 asm volatile( \
323 "1:"ALTERNATIVE(instr " " reg "1, [%2]\n", \
324 alt_instr " " reg "1, [%2]\n", feature) \
325 "2:\n" \
326 " .section .fixup,\"ax\"\n" \
327 " .align 2\n" \
328 "3: mov %w0, %3\n" \
329 " b 2b\n" \
330 " .previous\n" \
331 _ASM_EXTABLE(1b, 3b) \
332 : "+r" (err) \
333 : "r" (x), "r" (addr), "i" (-EFAULT))
334
335 #define __raw_put_user(x, ptr, err) \
336 do { \
337 __typeof__(*(ptr)) __pu_val = (x); \
338 __chk_user_ptr(ptr); \
339 uaccess_enable_not_uao(); \
340 switch (sizeof(*(ptr))) { \
341 case 1: \
342 __put_user_asm("strb", "sttrb", "%w", __pu_val, (ptr), \
343 (err), ARM64_HAS_UAO); \
344 break; \
345 case 2: \
346 __put_user_asm("strh", "sttrh", "%w", __pu_val, (ptr), \
347 (err), ARM64_HAS_UAO); \
348 break; \
349 case 4: \
350 __put_user_asm("str", "sttr", "%w", __pu_val, (ptr), \
351 (err), ARM64_HAS_UAO); \
352 break; \
353 case 8: \
354 __put_user_asm("str", "sttr", "%x", __pu_val, (ptr), \
355 (err), ARM64_HAS_UAO); \
356 break; \
357 default: \
358 BUILD_BUG(); \
359 } \
360 uaccess_disable_not_uao(); \
361 } while (0)
362
363 #define __put_user_error(x, ptr, err) \
364 do { \
365 __typeof__(*(ptr)) __user *__p = (ptr); \
366 might_fault(); \
367 if (access_ok(__p, sizeof(*__p))) { \
368 __p = uaccess_mask_ptr(__p); \
369 __raw_put_user((x), __p, (err)); \
370 } else { \
371 (err) = -EFAULT; \
372 } \
373 } while (0)
374
375 #define __put_user(x, ptr) \
376 ({ \
377 int __pu_err = 0; \
378 __put_user_error((x), (ptr), __pu_err); \
379 __pu_err; \
380 })
381
382 #define put_user __put_user
383
384 extern unsigned long __must_check __arch_copy_from_user(void *to, const void __user *from, unsigned long n);
385 #define raw_copy_from_user(to, from, n) \
386 ({ \
387 unsigned long __acfu_ret; \
388 uaccess_enable_not_uao(); \
389 __acfu_ret = __arch_copy_from_user((to), \
390 __uaccess_mask_ptr(from), (n)); \
391 uaccess_disable_not_uao(); \
392 __acfu_ret; \
393 })
394
395 extern unsigned long __must_check __arch_copy_to_user(void __user *to, const void *from, unsigned long n);
396 #define raw_copy_to_user(to, from, n) \
397 ({ \
398 unsigned long __actu_ret; \
399 uaccess_enable_not_uao(); \
400 __actu_ret = __arch_copy_to_user(__uaccess_mask_ptr(to), \
401 (from), (n)); \
402 uaccess_disable_not_uao(); \
403 __actu_ret; \
404 })
405
406 extern unsigned long __must_check __arch_copy_in_user(void __user *to, const void __user *from, unsigned long n);
407 #define raw_copy_in_user(to, from, n) \
408 ({ \
409 unsigned long __aciu_ret; \
410 uaccess_enable_not_uao(); \
411 __aciu_ret = __arch_copy_in_user(__uaccess_mask_ptr(to), \
412 __uaccess_mask_ptr(from), (n)); \
413 uaccess_disable_not_uao(); \
414 __aciu_ret; \
415 })
416
417 #define INLINE_COPY_TO_USER
418 #define INLINE_COPY_FROM_USER
419
420 extern unsigned long __must_check __arch_clear_user(void __user *to, unsigned long n);
__clear_user(void __user * to,unsigned long n)421 static inline unsigned long __must_check __clear_user(void __user *to, unsigned long n)
422 {
423 if (access_ok(to, n)) {
424 uaccess_enable_not_uao();
425 n = __arch_clear_user(__uaccess_mask_ptr(to), n);
426 uaccess_disable_not_uao();
427 }
428 return n;
429 }
430 #define clear_user __clear_user
431
432 extern long strncpy_from_user(char *dest, const char __user *src, long count);
433
434 extern __must_check long strnlen_user(const char __user *str, long n);
435
436 #ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
437 struct page;
438 void memcpy_page_flushcache(char *to, struct page *page, size_t offset, size_t len);
439 extern unsigned long __must_check __copy_user_flushcache(void *to, const void __user *from, unsigned long n);
440
__copy_from_user_flushcache(void * dst,const void __user * src,unsigned size)441 static inline int __copy_from_user_flushcache(void *dst, const void __user *src, unsigned size)
442 {
443 kasan_check_write(dst, size);
444 return __copy_user_flushcache(dst, __uaccess_mask_ptr(src), size);
445 }
446 #endif
447
448 #endif /* __ASM_UACCESS_H */
449
