1 /* 2 * Based on arch/arm/include/asm/uaccess.h 3 * 4 * Copyright (C) 2012 ARM Ltd. 5 * 6 * This program is free software; you can redistribute it and/or modify 7 * it under the terms of the GNU General Public License version 2 as 8 * published by the Free Software Foundation. 9 * 10 * This program is distributed in the hope that it will be useful, 11 * but WITHOUT ANY WARRANTY; without even the implied warranty of 12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 13 * GNU General Public License for more details. 14 * 15 * You should have received a copy of the GNU General Public License 16 * along with this program. If not, see <http://www.gnu.org/licenses/>. 17 */ 18 #ifndef __ASM_UACCESS_H 19 #define __ASM_UACCESS_H 20 21 #include <asm/alternative.h> 22 #include <asm/kernel-pgtable.h> 23 #include <asm/sysreg.h> 24 25 /* 26 * User space memory access functions 27 */ 28 #include <linux/bitops.h> 29 #include <linux/kasan-checks.h> 30 #include <linux/string.h> 31 #include <linux/thread_info.h> 32 33 #include <asm/cpufeature.h> 34 #include <asm/ptrace.h> 35 #include <asm/errno.h> 36 #include <asm/memory.h> 37 #include <asm/compiler.h> 38 39 #define VERIFY_READ 0 40 #define VERIFY_WRITE 1 41 42 /* 43 * The exception table consists of pairs of relative offsets: the first 44 * is the relative offset to an instruction that is allowed to fault, 45 * and the second is the relative offset at which the program should 46 * continue. No registers are modified, so it is entirely up to the 47 * continuation code to figure out what to do. 48 * 49 * All the routines below use bits of fixup code that are out of line 50 * with the main instruction path. This means when everything is well, 51 * we don't even have to jump over them. Further, they do not intrude 52 * on our cache or tlb entries. 53 */ 54 55 struct exception_table_entry 56 { 57 int insn, fixup; 58 }; 59 60 #define ARCH_HAS_RELATIVE_EXTABLE 61 62 extern int fixup_exception(struct pt_regs *regs); 63 64 #define KERNEL_DS (-1UL) 65 #define get_ds() (KERNEL_DS) 66 67 #define USER_DS TASK_SIZE_64 68 #define get_fs() (current_thread_info()->addr_limit) 69 70 static inline void set_fs(mm_segment_t fs) 71 { 72 current_thread_info()->addr_limit = fs; 73 74 /* 75 * Enable/disable UAO so that copy_to_user() etc can access 76 * kernel memory with the unprivileged instructions. 77 */ 78 if (IS_ENABLED(CONFIG_ARM64_UAO) && fs == KERNEL_DS) 79 asm(ALTERNATIVE("nop", SET_PSTATE_UAO(1), ARM64_HAS_UAO)); 80 else 81 asm(ALTERNATIVE("nop", SET_PSTATE_UAO(0), ARM64_HAS_UAO, 82 CONFIG_ARM64_UAO)); 83 } 84 85 #define segment_eq(a, b) ((a) == (b)) 86 87 /* 88 * Test whether a block of memory is a valid user space address. 89 * Returns 1 if the range is valid, 0 otherwise. 90 * 91 * This is equivalent to the following test: 92 * (u65)addr + (u65)size <= current->addr_limit 93 * 94 * This needs 65-bit arithmetic. 95 */ 96 #define __range_ok(addr, size) \ 97 ({ \ 98 unsigned long flag, roksum; \ 99 __chk_user_ptr(addr); \ 100 asm("adds %1, %1, %3; ccmp %1, %4, #2, cc; cset %0, ls" \ 101 : "=&r" (flag), "=&r" (roksum) \ 102 : "1" (addr), "Ir" (size), \ 103 "r" (current_thread_info()->addr_limit) \ 104 : "cc"); \ 105 flag; \ 106 }) 107 108 /* 109 * When dealing with data aborts or instruction traps we may end up with 110 * a tagged userland pointer. Clear the tag to get a sane pointer to pass 111 * on to access_ok(), for instance. 112 */ 113 #define untagged_addr(addr) sign_extend64(addr, 55) 114 115 #define access_ok(type, addr, size) __range_ok(addr, size) 116 #define user_addr_max get_fs 117 118 #define _ASM_EXTABLE(from, to) \ 119 " .pushsection __ex_table, \"a\"\n" \ 120 " .align 3\n" \ 121 " .long (" #from " - .), (" #to " - .)\n" \ 122 " .popsection\n" 123 124 /* 125 * User access enabling/disabling. 126 */ 127 #ifdef CONFIG_ARM64_SW_TTBR0_PAN 128 static inline void __uaccess_ttbr0_disable(void) 129 { 130 unsigned long ttbr; 131 132 /* reserved_ttbr0 placed at the end of swapper_pg_dir */ 133 ttbr = read_sysreg(ttbr1_el1) + SWAPPER_DIR_SIZE; 134 write_sysreg(ttbr, ttbr0_el1); 135 isb(); 136 } 137 138 static inline void __uaccess_ttbr0_enable(void) 139 { 140 unsigned long flags; 141 142 /* 143 * Disable interrupts to avoid preemption between reading the 'ttbr0' 144 * variable and the MSR. A context switch could trigger an ASID 145 * roll-over and an update of 'ttbr0'. 146 */ 147 local_irq_save(flags); 148 write_sysreg(current_thread_info()->ttbr0, ttbr0_el1); 149 isb(); 150 local_irq_restore(flags); 151 } 152 153 static inline bool uaccess_ttbr0_disable(void) 154 { 155 if (!system_uses_ttbr0_pan()) 156 return false; 157 __uaccess_ttbr0_disable(); 158 return true; 159 } 160 161 static inline bool uaccess_ttbr0_enable(void) 162 { 163 if (!system_uses_ttbr0_pan()) 164 return false; 165 __uaccess_ttbr0_enable(); 166 return true; 167 } 168 #else 169 static inline bool uaccess_ttbr0_disable(void) 170 { 171 return false; 172 } 173 174 static inline bool uaccess_ttbr0_enable(void) 175 { 176 return false; 177 } 178 #endif 179 180 #define __uaccess_disable(alt) \ 181 do { \ 182 if (!uaccess_ttbr0_disable()) \ 183 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), alt, \ 184 CONFIG_ARM64_PAN)); \ 185 } while (0) 186 187 #define __uaccess_enable(alt) \ 188 do { \ 189 if (!uaccess_ttbr0_enable()) \ 190 asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), alt, \ 191 CONFIG_ARM64_PAN)); \ 192 } while (0) 193 194 static inline void uaccess_disable(void) 195 { 196 __uaccess_disable(ARM64_HAS_PAN); 197 } 198 199 static inline void uaccess_enable(void) 200 { 201 __uaccess_enable(ARM64_HAS_PAN); 202 } 203 204 /* 205 * These functions are no-ops when UAO is present. 206 */ 207 static inline void uaccess_disable_not_uao(void) 208 { 209 __uaccess_disable(ARM64_ALT_PAN_NOT_UAO); 210 } 211 212 static inline void uaccess_enable_not_uao(void) 213 { 214 __uaccess_enable(ARM64_ALT_PAN_NOT_UAO); 215 } 216 217 /* 218 * The "__xxx" versions of the user access functions do not verify the address 219 * space - it must have been done previously with a separate "access_ok()" 220 * call. 221 * 222 * The "__xxx_error" versions set the third argument to -EFAULT if an error 223 * occurs, and leave it unchanged on success. 224 */ 225 #define __get_user_asm(instr, alt_instr, reg, x, addr, err, feature) \ 226 asm volatile( \ 227 "1:"ALTERNATIVE(instr " " reg "1, [%2]\n", \ 228 alt_instr " " reg "1, [%2]\n", feature) \ 229 "2:\n" \ 230 " .section .fixup, \"ax\"\n" \ 231 " .align 2\n" \ 232 "3: mov %w0, %3\n" \ 233 " mov %1, #0\n" \ 234 " b 2b\n" \ 235 " .previous\n" \ 236 _ASM_EXTABLE(1b, 3b) \ 237 : "+r" (err), "=&r" (x) \ 238 : "r" (addr), "i" (-EFAULT)) 239 240 #define __get_user_err(x, ptr, err) \ 241 do { \ 242 unsigned long __gu_val; \ 243 __chk_user_ptr(ptr); \ 244 uaccess_enable_not_uao(); \ 245 switch (sizeof(*(ptr))) { \ 246 case 1: \ 247 __get_user_asm("ldrb", "ldtrb", "%w", __gu_val, (ptr), \ 248 (err), ARM64_HAS_UAO); \ 249 break; \ 250 case 2: \ 251 __get_user_asm("ldrh", "ldtrh", "%w", __gu_val, (ptr), \ 252 (err), ARM64_HAS_UAO); \ 253 break; \ 254 case 4: \ 255 __get_user_asm("ldr", "ldtr", "%w", __gu_val, (ptr), \ 256 (err), ARM64_HAS_UAO); \ 257 break; \ 258 case 8: \ 259 __get_user_asm("ldr", "ldtr", "%", __gu_val, (ptr), \ 260 (err), ARM64_HAS_UAO); \ 261 break; \ 262 default: \ 263 BUILD_BUG(); \ 264 } \ 265 uaccess_disable_not_uao(); \ 266 (x) = (__force __typeof__(*(ptr)))__gu_val; \ 267 } while (0) 268 269 #define __get_user(x, ptr) \ 270 ({ \ 271 int __gu_err = 0; \ 272 __get_user_err((x), (ptr), __gu_err); \ 273 __gu_err; \ 274 }) 275 276 #define __get_user_error(x, ptr, err) \ 277 ({ \ 278 __get_user_err((x), (ptr), (err)); \ 279 (void)0; \ 280 }) 281 282 #define __get_user_unaligned __get_user 283 284 #define get_user(x, ptr) \ 285 ({ \ 286 __typeof__(*(ptr)) __user *__p = (ptr); \ 287 might_fault(); \ 288 access_ok(VERIFY_READ, __p, sizeof(*__p)) ? \ 289 __get_user((x), __p) : \ 290 ((x) = 0, -EFAULT); \ 291 }) 292 293 #define __put_user_asm(instr, alt_instr, reg, x, addr, err, feature) \ 294 asm volatile( \ 295 "1:"ALTERNATIVE(instr " " reg "1, [%2]\n", \ 296 alt_instr " " reg "1, [%2]\n", feature) \ 297 "2:\n" \ 298 " .section .fixup,\"ax\"\n" \ 299 " .align 2\n" \ 300 "3: mov %w0, %3\n" \ 301 " b 2b\n" \ 302 " .previous\n" \ 303 _ASM_EXTABLE(1b, 3b) \ 304 : "+r" (err) \ 305 : "r" (x), "r" (addr), "i" (-EFAULT)) 306 307 #define __put_user_err(x, ptr, err) \ 308 do { \ 309 __typeof__(*(ptr)) __pu_val = (x); \ 310 __chk_user_ptr(ptr); \ 311 uaccess_enable_not_uao(); \ 312 switch (sizeof(*(ptr))) { \ 313 case 1: \ 314 __put_user_asm("strb", "sttrb", "%w", __pu_val, (ptr), \ 315 (err), ARM64_HAS_UAO); \ 316 break; \ 317 case 2: \ 318 __put_user_asm("strh", "sttrh", "%w", __pu_val, (ptr), \ 319 (err), ARM64_HAS_UAO); \ 320 break; \ 321 case 4: \ 322 __put_user_asm("str", "sttr", "%w", __pu_val, (ptr), \ 323 (err), ARM64_HAS_UAO); \ 324 break; \ 325 case 8: \ 326 __put_user_asm("str", "sttr", "%", __pu_val, (ptr), \ 327 (err), ARM64_HAS_UAO); \ 328 break; \ 329 default: \ 330 BUILD_BUG(); \ 331 } \ 332 uaccess_disable_not_uao(); \ 333 } while (0) 334 335 #define __put_user(x, ptr) \ 336 ({ \ 337 int __pu_err = 0; \ 338 __put_user_err((x), (ptr), __pu_err); \ 339 __pu_err; \ 340 }) 341 342 #define __put_user_error(x, ptr, err) \ 343 ({ \ 344 __put_user_err((x), (ptr), (err)); \ 345 (void)0; \ 346 }) 347 348 #define __put_user_unaligned __put_user 349 350 #define put_user(x, ptr) \ 351 ({ \ 352 __typeof__(*(ptr)) __user *__p = (ptr); \ 353 might_fault(); \ 354 access_ok(VERIFY_WRITE, __p, sizeof(*__p)) ? \ 355 __put_user((x), __p) : \ 356 -EFAULT; \ 357 }) 358 359 extern unsigned long __must_check __arch_copy_from_user(void *to, const void __user *from, unsigned long n); 360 extern unsigned long __must_check __arch_copy_to_user(void __user *to, const void *from, unsigned long n); 361 extern unsigned long __must_check __copy_in_user(void __user *to, const void __user *from, unsigned long n); 362 extern unsigned long __must_check __clear_user(void __user *addr, unsigned long n); 363 364 static inline unsigned long __must_check __copy_from_user(void *to, const void __user *from, unsigned long n) 365 { 366 kasan_check_write(to, n); 367 check_object_size(to, n, false); 368 return __arch_copy_from_user(to, from, n); 369 } 370 371 static inline unsigned long __must_check __copy_to_user(void __user *to, const void *from, unsigned long n) 372 { 373 kasan_check_read(from, n); 374 check_object_size(from, n, true); 375 return __arch_copy_to_user(to, from, n); 376 } 377 378 static inline unsigned long __must_check copy_from_user(void *to, const void __user *from, unsigned long n) 379 { 380 unsigned long res = n; 381 kasan_check_write(to, n); 382 check_object_size(to, n, false); 383 384 if (access_ok(VERIFY_READ, from, n)) { 385 res = __arch_copy_from_user(to, from, n); 386 } 387 if (unlikely(res)) 388 memset(to + (n - res), 0, res); 389 return res; 390 } 391 392 static inline unsigned long __must_check copy_to_user(void __user *to, const void *from, unsigned long n) 393 { 394 kasan_check_read(from, n); 395 check_object_size(from, n, true); 396 397 if (access_ok(VERIFY_WRITE, to, n)) { 398 n = __arch_copy_to_user(to, from, n); 399 } 400 return n; 401 } 402 403 static inline unsigned long __must_check copy_in_user(void __user *to, const void __user *from, unsigned long n) 404 { 405 if (access_ok(VERIFY_READ, from, n) && access_ok(VERIFY_WRITE, to, n)) 406 n = __copy_in_user(to, from, n); 407 return n; 408 } 409 410 #define __copy_to_user_inatomic __copy_to_user 411 #define __copy_from_user_inatomic __copy_from_user 412 413 static inline unsigned long __must_check clear_user(void __user *to, unsigned long n) 414 { 415 if (access_ok(VERIFY_WRITE, to, n)) 416 n = __clear_user(to, n); 417 return n; 418 } 419 420 extern long strncpy_from_user(char *dest, const char __user *src, long count); 421 422 extern __must_check long strlen_user(const char __user *str); 423 extern __must_check long strnlen_user(const char __user *str, long n); 424 425 #endif /* __ASM_UACCESS_H */ 426