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