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 */ 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 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 isb(); 69 /* Set reserved ASID */ 70 write_sysreg(ttbr, ttbr1_el1); 71 isb(); 72 local_irq_restore(flags); 73 } 74 75 static inline void __uaccess_ttbr0_enable(void) 76 { 77 unsigned long flags, ttbr0, ttbr1; 78 79 /* 80 * Disable interrupts to avoid preemption between reading the 'ttbr0' 81 * variable and the MSR. A context switch could trigger an ASID 82 * roll-over and an update of 'ttbr0'. 83 */ 84 local_irq_save(flags); 85 ttbr0 = READ_ONCE(current_thread_info()->ttbr0); 86 87 /* Restore active ASID */ 88 ttbr1 = read_sysreg(ttbr1_el1); 89 ttbr1 &= ~TTBR_ASID_MASK; /* safety measure */ 90 ttbr1 |= ttbr0 & TTBR_ASID_MASK; 91 write_sysreg(ttbr1, ttbr1_el1); 92 isb(); 93 94 /* Restore user page table */ 95 write_sysreg(ttbr0, ttbr0_el1); 96 isb(); 97 local_irq_restore(flags); 98 } 99 100 static inline bool uaccess_ttbr0_disable(void) 101 { 102 if (!system_uses_ttbr0_pan()) 103 return false; 104 __uaccess_ttbr0_disable(); 105 return true; 106 } 107 108 static inline bool uaccess_ttbr0_enable(void) 109 { 110 if (!system_uses_ttbr0_pan()) 111 return false; 112 __uaccess_ttbr0_enable(); 113 return true; 114 } 115 #else 116 static inline bool uaccess_ttbr0_disable(void) 117 { 118 return false; 119 } 120 121 static inline bool uaccess_ttbr0_enable(void) 122 { 123 return false; 124 } 125 #endif 126 127 static inline void __uaccess_disable_hw_pan(void) 128 { 129 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_HAS_PAN, 130 CONFIG_ARM64_PAN)); 131 } 132 133 static inline void __uaccess_enable_hw_pan(void) 134 { 135 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_HAS_PAN, 136 CONFIG_ARM64_PAN)); 137 } 138 139 /* 140 * The Tag Check Flag (TCF) mode for MTE is per EL, hence TCF0 141 * affects EL0 and TCF affects EL1 irrespective of which TTBR is 142 * used. 143 * The kernel accesses TTBR0 usually with LDTR/STTR instructions 144 * when UAO is available, so these would act as EL0 accesses using 145 * TCF0. 146 * However futex.h code uses exclusives which would be executed as 147 * EL1, this can potentially cause a tag check fault even if the 148 * user disables TCF0. 149 * 150 * To address the problem we set the PSTATE.TCO bit in uaccess_enable() 151 * and reset it in uaccess_disable(). 152 * 153 * The Tag check override (TCO) bit disables temporarily the tag checking 154 * preventing the issue. 155 */ 156 static inline void __uaccess_disable_tco(void) 157 { 158 asm volatile(ALTERNATIVE("nop", SET_PSTATE_TCO(0), 159 ARM64_MTE, CONFIG_KASAN_HW_TAGS)); 160 } 161 162 static inline void __uaccess_enable_tco(void) 163 { 164 asm volatile(ALTERNATIVE("nop", SET_PSTATE_TCO(1), 165 ARM64_MTE, CONFIG_KASAN_HW_TAGS)); 166 } 167 168 /* 169 * These functions disable tag checking only if in MTE async mode 170 * since the sync mode generates exceptions synchronously and the 171 * nofault or load_unaligned_zeropad can handle them. 172 */ 173 static inline void __uaccess_disable_tco_async(void) 174 { 175 if (system_uses_mte_async_or_asymm_mode()) 176 __uaccess_disable_tco(); 177 } 178 179 static inline void __uaccess_enable_tco_async(void) 180 { 181 if (system_uses_mte_async_or_asymm_mode()) 182 __uaccess_enable_tco(); 183 } 184 185 static inline void uaccess_disable_privileged(void) 186 { 187 __uaccess_disable_tco(); 188 189 if (uaccess_ttbr0_disable()) 190 return; 191 192 __uaccess_enable_hw_pan(); 193 } 194 195 static inline void uaccess_enable_privileged(void) 196 { 197 __uaccess_enable_tco(); 198 199 if (uaccess_ttbr0_enable()) 200 return; 201 202 __uaccess_disable_hw_pan(); 203 } 204 205 /* 206 * Sanitize a uaccess pointer such that it cannot reach any kernel address. 207 * 208 * Clearing bit 55 ensures the pointer cannot address any portion of the TTBR1 209 * address range (i.e. any kernel address), and either the pointer falls within 210 * the TTBR0 address range or must cause a fault. 211 */ 212 #define uaccess_mask_ptr(ptr) (__typeof__(ptr))__uaccess_mask_ptr(ptr) 213 static inline void __user *__uaccess_mask_ptr(const void __user *ptr) 214 { 215 void __user *safe_ptr; 216 217 asm volatile( 218 " bic %0, %1, %2\n" 219 : "=r" (safe_ptr) 220 : "r" (ptr), 221 "i" (BIT(55)) 222 ); 223 224 return safe_ptr; 225 } 226 227 /* 228 * The "__xxx" versions of the user access functions do not verify the address 229 * space - it must have been done previously with a separate "access_ok()" 230 * call. 231 * 232 * The "__xxx_error" versions set the third argument to -EFAULT if an error 233 * occurs, and leave it unchanged on success. 234 */ 235 #define __get_mem_asm(load, reg, x, addr, err, type) \ 236 asm volatile( \ 237 "1: " load " " reg "1, [%2]\n" \ 238 "2:\n" \ 239 _ASM_EXTABLE_##type##ACCESS_ERR_ZERO(1b, 2b, %w0, %w1) \ 240 : "+r" (err), "=&r" (x) \ 241 : "r" (addr)) 242 243 #define __raw_get_mem(ldr, x, ptr, err, type) \ 244 do { \ 245 unsigned long __gu_val; \ 246 switch (sizeof(*(ptr))) { \ 247 case 1: \ 248 __get_mem_asm(ldr "b", "%w", __gu_val, (ptr), (err), type); \ 249 break; \ 250 case 2: \ 251 __get_mem_asm(ldr "h", "%w", __gu_val, (ptr), (err), type); \ 252 break; \ 253 case 4: \ 254 __get_mem_asm(ldr, "%w", __gu_val, (ptr), (err), type); \ 255 break; \ 256 case 8: \ 257 __get_mem_asm(ldr, "%x", __gu_val, (ptr), (err), type); \ 258 break; \ 259 default: \ 260 BUILD_BUG(); \ 261 } \ 262 (x) = (__force __typeof__(*(ptr)))__gu_val; \ 263 } while (0) 264 265 /* 266 * We must not call into the scheduler between uaccess_ttbr0_enable() and 267 * uaccess_ttbr0_disable(). As `x` and `ptr` could contain blocking functions, 268 * we must evaluate these outside of the critical section. 269 */ 270 #define __raw_get_user(x, ptr, err) \ 271 do { \ 272 __typeof__(*(ptr)) __user *__rgu_ptr = (ptr); \ 273 __typeof__(x) __rgu_val; \ 274 __chk_user_ptr(ptr); \ 275 \ 276 uaccess_ttbr0_enable(); \ 277 __raw_get_mem("ldtr", __rgu_val, __rgu_ptr, err, U); \ 278 uaccess_ttbr0_disable(); \ 279 \ 280 (x) = __rgu_val; \ 281 } while (0) 282 283 #define __get_user_error(x, ptr, err) \ 284 do { \ 285 __typeof__(*(ptr)) __user *__p = (ptr); \ 286 might_fault(); \ 287 if (access_ok(__p, sizeof(*__p))) { \ 288 __p = uaccess_mask_ptr(__p); \ 289 __raw_get_user((x), __p, (err)); \ 290 } else { \ 291 (x) = (__force __typeof__(x))0; (err) = -EFAULT; \ 292 } \ 293 } while (0) 294 295 #define __get_user(x, ptr) \ 296 ({ \ 297 int __gu_err = 0; \ 298 __get_user_error((x), (ptr), __gu_err); \ 299 __gu_err; \ 300 }) 301 302 #define get_user __get_user 303 304 /* 305 * We must not call into the scheduler between __uaccess_enable_tco_async() and 306 * __uaccess_disable_tco_async(). As `dst` and `src` may contain blocking 307 * functions, we must evaluate these outside of the critical section. 308 */ 309 #define __get_kernel_nofault(dst, src, type, err_label) \ 310 do { \ 311 __typeof__(dst) __gkn_dst = (dst); \ 312 __typeof__(src) __gkn_src = (src); \ 313 int __gkn_err = 0; \ 314 \ 315 __uaccess_enable_tco_async(); \ 316 __raw_get_mem("ldr", *((type *)(__gkn_dst)), \ 317 (__force type *)(__gkn_src), __gkn_err, K); \ 318 __uaccess_disable_tco_async(); \ 319 \ 320 if (unlikely(__gkn_err)) \ 321 goto err_label; \ 322 } while (0) 323 324 #define __put_mem_asm(store, reg, x, addr, err, type) \ 325 asm volatile( \ 326 "1: " store " " reg "1, [%2]\n" \ 327 "2:\n" \ 328 _ASM_EXTABLE_##type##ACCESS_ERR(1b, 2b, %w0) \ 329 : "+r" (err) \ 330 : "r" (x), "r" (addr)) 331 332 #define __raw_put_mem(str, x, ptr, err, type) \ 333 do { \ 334 __typeof__(*(ptr)) __pu_val = (x); \ 335 switch (sizeof(*(ptr))) { \ 336 case 1: \ 337 __put_mem_asm(str "b", "%w", __pu_val, (ptr), (err), type); \ 338 break; \ 339 case 2: \ 340 __put_mem_asm(str "h", "%w", __pu_val, (ptr), (err), type); \ 341 break; \ 342 case 4: \ 343 __put_mem_asm(str, "%w", __pu_val, (ptr), (err), type); \ 344 break; \ 345 case 8: \ 346 __put_mem_asm(str, "%x", __pu_val, (ptr), (err), type); \ 347 break; \ 348 default: \ 349 BUILD_BUG(); \ 350 } \ 351 } while (0) 352 353 /* 354 * We must not call into the scheduler between uaccess_ttbr0_enable() and 355 * uaccess_ttbr0_disable(). As `x` and `ptr` could contain blocking functions, 356 * we must evaluate these outside of the critical section. 357 */ 358 #define __raw_put_user(x, ptr, err) \ 359 do { \ 360 __typeof__(*(ptr)) __user *__rpu_ptr = (ptr); \ 361 __typeof__(*(ptr)) __rpu_val = (x); \ 362 __chk_user_ptr(__rpu_ptr); \ 363 \ 364 uaccess_ttbr0_enable(); \ 365 __raw_put_mem("sttr", __rpu_val, __rpu_ptr, err, U); \ 366 uaccess_ttbr0_disable(); \ 367 } while (0) 368 369 #define __put_user_error(x, ptr, err) \ 370 do { \ 371 __typeof__(*(ptr)) __user *__p = (ptr); \ 372 might_fault(); \ 373 if (access_ok(__p, sizeof(*__p))) { \ 374 __p = uaccess_mask_ptr(__p); \ 375 __raw_put_user((x), __p, (err)); \ 376 } else { \ 377 (err) = -EFAULT; \ 378 } \ 379 } while (0) 380 381 #define __put_user(x, ptr) \ 382 ({ \ 383 int __pu_err = 0; \ 384 __put_user_error((x), (ptr), __pu_err); \ 385 __pu_err; \ 386 }) 387 388 #define put_user __put_user 389 390 /* 391 * We must not call into the scheduler between __uaccess_enable_tco_async() and 392 * __uaccess_disable_tco_async(). As `dst` and `src` may contain blocking 393 * functions, we must evaluate these outside of the critical section. 394 */ 395 #define __put_kernel_nofault(dst, src, type, err_label) \ 396 do { \ 397 __typeof__(dst) __pkn_dst = (dst); \ 398 __typeof__(src) __pkn_src = (src); \ 399 int __pkn_err = 0; \ 400 \ 401 __uaccess_enable_tco_async(); \ 402 __raw_put_mem("str", *((type *)(__pkn_src)), \ 403 (__force type *)(__pkn_dst), __pkn_err, K); \ 404 __uaccess_disable_tco_async(); \ 405 \ 406 if (unlikely(__pkn_err)) \ 407 goto err_label; \ 408 } while(0) 409 410 extern unsigned long __must_check __arch_copy_from_user(void *to, const void __user *from, unsigned long n); 411 #define raw_copy_from_user(to, from, n) \ 412 ({ \ 413 unsigned long __acfu_ret; \ 414 uaccess_ttbr0_enable(); \ 415 __acfu_ret = __arch_copy_from_user((to), \ 416 __uaccess_mask_ptr(from), (n)); \ 417 uaccess_ttbr0_disable(); \ 418 __acfu_ret; \ 419 }) 420 421 extern unsigned long __must_check __arch_copy_to_user(void __user *to, const void *from, unsigned long n); 422 #define raw_copy_to_user(to, from, n) \ 423 ({ \ 424 unsigned long __actu_ret; \ 425 uaccess_ttbr0_enable(); \ 426 __actu_ret = __arch_copy_to_user(__uaccess_mask_ptr(to), \ 427 (from), (n)); \ 428 uaccess_ttbr0_disable(); \ 429 __actu_ret; \ 430 }) 431 432 #define INLINE_COPY_TO_USER 433 #define INLINE_COPY_FROM_USER 434 435 extern unsigned long __must_check __arch_clear_user(void __user *to, unsigned long n); 436 static inline unsigned long __must_check __clear_user(void __user *to, unsigned long n) 437 { 438 if (access_ok(to, n)) { 439 uaccess_ttbr0_enable(); 440 n = __arch_clear_user(__uaccess_mask_ptr(to), n); 441 uaccess_ttbr0_disable(); 442 } 443 return n; 444 } 445 #define clear_user __clear_user 446 447 extern long strncpy_from_user(char *dest, const char __user *src, long count); 448 449 extern __must_check long strnlen_user(const char __user *str, long n); 450 451 #ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE 452 struct page; 453 void memcpy_page_flushcache(char *to, struct page *page, size_t offset, size_t len); 454 extern unsigned long __must_check __copy_user_flushcache(void *to, const void __user *from, unsigned long n); 455 456 static inline int __copy_from_user_flushcache(void *dst, const void __user *src, unsigned size) 457 { 458 kasan_check_write(dst, size); 459 return __copy_user_flushcache(dst, __uaccess_mask_ptr(src), size); 460 } 461 #endif 462 463 #ifdef CONFIG_ARCH_HAS_SUBPAGE_FAULTS 464 465 /* 466 * Return 0 on success, the number of bytes not probed otherwise. 467 */ 468 static inline size_t probe_subpage_writeable(const char __user *uaddr, 469 size_t size) 470 { 471 if (!system_supports_mte()) 472 return 0; 473 return mte_probe_user_range(uaddr, size); 474 } 475 476 #endif /* CONFIG_ARCH_HAS_SUBPAGE_FAULTS */ 477 478 #endif /* __ASM_UACCESS_H */ 479