1 /* 2 * Based on arch/arm/mm/fault.c 3 * 4 * Copyright (C) 1995 Linus Torvalds 5 * Copyright (C) 1995-2004 Russell King 6 * Copyright (C) 2012 ARM Ltd. 7 * 8 * This program is free software; you can redistribute it and/or modify 9 * it under the terms of the GNU General Public License version 2 as 10 * published by the Free Software Foundation. 11 * 12 * This program is distributed in the hope that it will be useful, 13 * but WITHOUT ANY WARRANTY; without even the implied warranty of 14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 15 * GNU General Public License for more details. 16 * 17 * You should have received a copy of the GNU General Public License 18 * along with this program. If not, see <http://www.gnu.org/licenses/>. 19 */ 20 21 #include <linux/module.h> 22 #include <linux/signal.h> 23 #include <linux/mm.h> 24 #include <linux/hardirq.h> 25 #include <linux/init.h> 26 #include <linux/kprobes.h> 27 #include <linux/uaccess.h> 28 #include <linux/page-flags.h> 29 #include <linux/sched.h> 30 #include <linux/highmem.h> 31 #include <linux/perf_event.h> 32 33 #include <asm/exception.h> 34 #include <asm/debug-monitors.h> 35 #include <asm/system_misc.h> 36 #include <asm/pgtable.h> 37 #include <asm/tlbflush.h> 38 39 /* 40 * Dump out the page tables associated with 'addr' in mm 'mm'. 41 */ 42 void show_pte(struct mm_struct *mm, unsigned long addr) 43 { 44 pgd_t *pgd; 45 46 if (!mm) 47 mm = &init_mm; 48 49 pr_alert("pgd = %p\n", mm->pgd); 50 pgd = pgd_offset(mm, addr); 51 pr_alert("[%08lx] *pgd=%016llx", addr, pgd_val(*pgd)); 52 53 do { 54 pud_t *pud; 55 pmd_t *pmd; 56 pte_t *pte; 57 58 if (pgd_none_or_clear_bad(pgd)) 59 break; 60 61 pud = pud_offset(pgd, addr); 62 if (pud_none_or_clear_bad(pud)) 63 break; 64 65 pmd = pmd_offset(pud, addr); 66 printk(", *pmd=%016llx", pmd_val(*pmd)); 67 if (pmd_none_or_clear_bad(pmd)) 68 break; 69 70 pte = pte_offset_map(pmd, addr); 71 printk(", *pte=%016llx", pte_val(*pte)); 72 pte_unmap(pte); 73 } while(0); 74 75 printk("\n"); 76 } 77 78 /* 79 * The kernel tried to access some page that wasn't present. 80 */ 81 static void __do_kernel_fault(struct mm_struct *mm, unsigned long addr, 82 unsigned int esr, struct pt_regs *regs) 83 { 84 /* 85 * Are we prepared to handle this kernel fault? 86 */ 87 if (fixup_exception(regs)) 88 return; 89 90 /* 91 * No handler, we'll have to terminate things with extreme prejudice. 92 */ 93 bust_spinlocks(1); 94 pr_alert("Unable to handle kernel %s at virtual address %08lx\n", 95 (addr < PAGE_SIZE) ? "NULL pointer dereference" : 96 "paging request", addr); 97 98 show_pte(mm, addr); 99 die("Oops", regs, esr); 100 bust_spinlocks(0); 101 do_exit(SIGKILL); 102 } 103 104 /* 105 * Something tried to access memory that isn't in our memory map. User mode 106 * accesses just cause a SIGSEGV 107 */ 108 static void __do_user_fault(struct task_struct *tsk, unsigned long addr, 109 unsigned int esr, unsigned int sig, int code, 110 struct pt_regs *regs) 111 { 112 struct siginfo si; 113 114 if (show_unhandled_signals) { 115 pr_info("%s[%d]: unhandled page fault (%d) at 0x%08lx, code 0x%03x\n", 116 tsk->comm, task_pid_nr(tsk), sig, addr, esr); 117 show_pte(tsk->mm, addr); 118 show_regs(regs); 119 } 120 121 tsk->thread.fault_address = addr; 122 si.si_signo = sig; 123 si.si_errno = 0; 124 si.si_code = code; 125 si.si_addr = (void __user *)addr; 126 force_sig_info(sig, &si, tsk); 127 } 128 129 void do_bad_area(unsigned long addr, unsigned int esr, struct pt_regs *regs) 130 { 131 struct task_struct *tsk = current; 132 struct mm_struct *mm = tsk->active_mm; 133 134 /* 135 * If we are in kernel mode at this point, we have no context to 136 * handle this fault with. 137 */ 138 if (user_mode(regs)) 139 __do_user_fault(tsk, addr, esr, SIGSEGV, SEGV_MAPERR, regs); 140 else 141 __do_kernel_fault(mm, addr, esr, regs); 142 } 143 144 #define VM_FAULT_BADMAP 0x010000 145 #define VM_FAULT_BADACCESS 0x020000 146 147 #define ESR_WRITE (1 << 6) 148 #define ESR_LNX_EXEC (1 << 24) 149 150 /* 151 * Check that the permissions on the VMA allow for the fault which occurred. 152 * If we encountered a write fault, we must have write permission, otherwise 153 * we allow any permission. 154 */ 155 static inline bool access_error(unsigned int esr, struct vm_area_struct *vma) 156 { 157 unsigned int mask = VM_READ | VM_WRITE | VM_EXEC; 158 159 if (esr & ESR_WRITE) 160 mask = VM_WRITE; 161 if (esr & ESR_LNX_EXEC) 162 mask = VM_EXEC; 163 164 return vma->vm_flags & mask ? false : true; 165 } 166 167 static int __do_page_fault(struct mm_struct *mm, unsigned long addr, 168 unsigned int esr, unsigned int flags, 169 struct task_struct *tsk) 170 { 171 struct vm_area_struct *vma; 172 int fault; 173 174 vma = find_vma(mm, addr); 175 fault = VM_FAULT_BADMAP; 176 if (unlikely(!vma)) 177 goto out; 178 if (unlikely(vma->vm_start > addr)) 179 goto check_stack; 180 181 /* 182 * Ok, we have a good vm_area for this memory access, so we can handle 183 * it. 184 */ 185 good_area: 186 if (access_error(esr, vma)) { 187 fault = VM_FAULT_BADACCESS; 188 goto out; 189 } 190 191 return handle_mm_fault(mm, vma, addr & PAGE_MASK, flags); 192 193 check_stack: 194 if (vma->vm_flags & VM_GROWSDOWN && !expand_stack(vma, addr)) 195 goto good_area; 196 out: 197 return fault; 198 } 199 200 static int __kprobes do_page_fault(unsigned long addr, unsigned int esr, 201 struct pt_regs *regs) 202 { 203 struct task_struct *tsk; 204 struct mm_struct *mm; 205 int fault, sig, code; 206 int write = esr & ESR_WRITE; 207 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE | 208 (write ? FAULT_FLAG_WRITE : 0); 209 210 tsk = current; 211 mm = tsk->mm; 212 213 /* Enable interrupts if they were enabled in the parent context. */ 214 if (interrupts_enabled(regs)) 215 local_irq_enable(); 216 217 /* 218 * If we're in an interrupt or have no user context, we must not take 219 * the fault. 220 */ 221 if (in_atomic() || !mm) 222 goto no_context; 223 224 /* 225 * As per x86, we may deadlock here. However, since the kernel only 226 * validly references user space from well defined areas of the code, 227 * we can bug out early if this is from code which shouldn't. 228 */ 229 if (!down_read_trylock(&mm->mmap_sem)) { 230 if (!user_mode(regs) && !search_exception_tables(regs->pc)) 231 goto no_context; 232 retry: 233 down_read(&mm->mmap_sem); 234 } else { 235 /* 236 * The above down_read_trylock() might have succeeded in which 237 * case, we'll have missed the might_sleep() from down_read(). 238 */ 239 might_sleep(); 240 #ifdef CONFIG_DEBUG_VM 241 if (!user_mode(regs) && !search_exception_tables(regs->pc)) 242 goto no_context; 243 #endif 244 } 245 246 fault = __do_page_fault(mm, addr, esr, flags, tsk); 247 248 /* 249 * If we need to retry but a fatal signal is pending, handle the 250 * signal first. We do not need to release the mmap_sem because it 251 * would already be released in __lock_page_or_retry in mm/filemap.c. 252 */ 253 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) 254 return 0; 255 256 /* 257 * Major/minor page fault accounting is only done on the initial 258 * attempt. If we go through a retry, it is extremely likely that the 259 * page will be found in page cache at that point. 260 */ 261 262 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr); 263 if (flags & FAULT_FLAG_ALLOW_RETRY) { 264 if (fault & VM_FAULT_MAJOR) { 265 tsk->maj_flt++; 266 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, 267 addr); 268 } else { 269 tsk->min_flt++; 270 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, 271 addr); 272 } 273 if (fault & VM_FAULT_RETRY) { 274 /* 275 * Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk of 276 * starvation. 277 */ 278 flags &= ~FAULT_FLAG_ALLOW_RETRY; 279 goto retry; 280 } 281 } 282 283 up_read(&mm->mmap_sem); 284 285 /* 286 * Handle the "normal" case first - VM_FAULT_MAJOR / VM_FAULT_MINOR 287 */ 288 if (likely(!(fault & (VM_FAULT_ERROR | VM_FAULT_BADMAP | 289 VM_FAULT_BADACCESS)))) 290 return 0; 291 292 if (fault & VM_FAULT_OOM) { 293 /* 294 * We ran out of memory, call the OOM killer, and return to 295 * userspace (which will retry the fault, or kill us if we got 296 * oom-killed). 297 */ 298 pagefault_out_of_memory(); 299 return 0; 300 } 301 302 /* 303 * If we are in kernel mode at this point, we have no context to 304 * handle this fault with. 305 */ 306 if (!user_mode(regs)) 307 goto no_context; 308 309 if (fault & VM_FAULT_SIGBUS) { 310 /* 311 * We had some memory, but were unable to successfully fix up 312 * this page fault. 313 */ 314 sig = SIGBUS; 315 code = BUS_ADRERR; 316 } else { 317 /* 318 * Something tried to access memory that isn't in our memory 319 * map. 320 */ 321 sig = SIGSEGV; 322 code = fault == VM_FAULT_BADACCESS ? 323 SEGV_ACCERR : SEGV_MAPERR; 324 } 325 326 __do_user_fault(tsk, addr, esr, sig, code, regs); 327 return 0; 328 329 no_context: 330 __do_kernel_fault(mm, addr, esr, regs); 331 return 0; 332 } 333 334 /* 335 * First Level Translation Fault Handler 336 * 337 * We enter here because the first level page table doesn't contain a valid 338 * entry for the address. 339 * 340 * If the address is in kernel space (>= TASK_SIZE), then we are probably 341 * faulting in the vmalloc() area. 342 * 343 * If the init_task's first level page tables contains the relevant entry, we 344 * copy the it to this task. If not, we send the process a signal, fixup the 345 * exception, or oops the kernel. 346 * 347 * NOTE! We MUST NOT take any locks for this case. We may be in an interrupt 348 * or a critical region, and should only copy the information from the master 349 * page table, nothing more. 350 */ 351 static int __kprobes do_translation_fault(unsigned long addr, 352 unsigned int esr, 353 struct pt_regs *regs) 354 { 355 if (addr < TASK_SIZE) 356 return do_page_fault(addr, esr, regs); 357 358 do_bad_area(addr, esr, regs); 359 return 0; 360 } 361 362 /* 363 * Some section permission faults need to be handled gracefully. They can 364 * happen due to a __{get,put}_user during an oops. 365 */ 366 static int do_sect_fault(unsigned long addr, unsigned int esr, 367 struct pt_regs *regs) 368 { 369 do_bad_area(addr, esr, regs); 370 return 0; 371 } 372 373 /* 374 * This abort handler always returns "fault". 375 */ 376 static int do_bad(unsigned long addr, unsigned int esr, struct pt_regs *regs) 377 { 378 return 1; 379 } 380 381 static struct fault_info { 382 int (*fn)(unsigned long addr, unsigned int esr, struct pt_regs *regs); 383 int sig; 384 int code; 385 const char *name; 386 } fault_info[] = { 387 { do_bad, SIGBUS, 0, "ttbr address size fault" }, 388 { do_bad, SIGBUS, 0, "level 1 address size fault" }, 389 { do_bad, SIGBUS, 0, "level 2 address size fault" }, 390 { do_bad, SIGBUS, 0, "level 3 address size fault" }, 391 { do_translation_fault, SIGSEGV, SEGV_MAPERR, "input address range fault" }, 392 { do_translation_fault, SIGSEGV, SEGV_MAPERR, "level 1 translation fault" }, 393 { do_translation_fault, SIGSEGV, SEGV_MAPERR, "level 2 translation fault" }, 394 { do_page_fault, SIGSEGV, SEGV_MAPERR, "level 3 translation fault" }, 395 { do_bad, SIGBUS, 0, "reserved access flag fault" }, 396 { do_bad, SIGSEGV, SEGV_ACCERR, "level 1 access flag fault" }, 397 { do_bad, SIGSEGV, SEGV_ACCERR, "level 2 access flag fault" }, 398 { do_page_fault, SIGSEGV, SEGV_ACCERR, "level 3 access flag fault" }, 399 { do_bad, SIGBUS, 0, "reserved permission fault" }, 400 { do_bad, SIGSEGV, SEGV_ACCERR, "level 1 permission fault" }, 401 { do_sect_fault, SIGSEGV, SEGV_ACCERR, "level 2 permission fault" }, 402 { do_page_fault, SIGSEGV, SEGV_ACCERR, "level 3 permission fault" }, 403 { do_bad, SIGBUS, 0, "synchronous external abort" }, 404 { do_bad, SIGBUS, 0, "asynchronous external abort" }, 405 { do_bad, SIGBUS, 0, "unknown 18" }, 406 { do_bad, SIGBUS, 0, "unknown 19" }, 407 { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" }, 408 { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" }, 409 { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" }, 410 { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" }, 411 { do_bad, SIGBUS, 0, "synchronous parity error" }, 412 { do_bad, SIGBUS, 0, "asynchronous parity error" }, 413 { do_bad, SIGBUS, 0, "unknown 26" }, 414 { do_bad, SIGBUS, 0, "unknown 27" }, 415 { do_bad, SIGBUS, 0, "synchronous parity error (translation table walk" }, 416 { do_bad, SIGBUS, 0, "synchronous parity error (translation table walk" }, 417 { do_bad, SIGBUS, 0, "synchronous parity error (translation table walk" }, 418 { do_bad, SIGBUS, 0, "synchronous parity error (translation table walk" }, 419 { do_bad, SIGBUS, 0, "unknown 32" }, 420 { do_bad, SIGBUS, BUS_ADRALN, "alignment fault" }, 421 { do_bad, SIGBUS, 0, "debug event" }, 422 { do_bad, SIGBUS, 0, "unknown 35" }, 423 { do_bad, SIGBUS, 0, "unknown 36" }, 424 { do_bad, SIGBUS, 0, "unknown 37" }, 425 { do_bad, SIGBUS, 0, "unknown 38" }, 426 { do_bad, SIGBUS, 0, "unknown 39" }, 427 { do_bad, SIGBUS, 0, "unknown 40" }, 428 { do_bad, SIGBUS, 0, "unknown 41" }, 429 { do_bad, SIGBUS, 0, "unknown 42" }, 430 { do_bad, SIGBUS, 0, "unknown 43" }, 431 { do_bad, SIGBUS, 0, "unknown 44" }, 432 { do_bad, SIGBUS, 0, "unknown 45" }, 433 { do_bad, SIGBUS, 0, "unknown 46" }, 434 { do_bad, SIGBUS, 0, "unknown 47" }, 435 { do_bad, SIGBUS, 0, "unknown 48" }, 436 { do_bad, SIGBUS, 0, "unknown 49" }, 437 { do_bad, SIGBUS, 0, "unknown 50" }, 438 { do_bad, SIGBUS, 0, "unknown 51" }, 439 { do_bad, SIGBUS, 0, "implementation fault (lockdown abort)" }, 440 { do_bad, SIGBUS, 0, "unknown 53" }, 441 { do_bad, SIGBUS, 0, "unknown 54" }, 442 { do_bad, SIGBUS, 0, "unknown 55" }, 443 { do_bad, SIGBUS, 0, "unknown 56" }, 444 { do_bad, SIGBUS, 0, "unknown 57" }, 445 { do_bad, SIGBUS, 0, "implementation fault (coprocessor abort)" }, 446 { do_bad, SIGBUS, 0, "unknown 59" }, 447 { do_bad, SIGBUS, 0, "unknown 60" }, 448 { do_bad, SIGBUS, 0, "unknown 61" }, 449 { do_bad, SIGBUS, 0, "unknown 62" }, 450 { do_bad, SIGBUS, 0, "unknown 63" }, 451 }; 452 453 /* 454 * Dispatch a data abort to the relevant handler. 455 */ 456 asmlinkage void __exception do_mem_abort(unsigned long addr, unsigned int esr, 457 struct pt_regs *regs) 458 { 459 const struct fault_info *inf = fault_info + (esr & 63); 460 struct siginfo info; 461 462 if (!inf->fn(addr, esr, regs)) 463 return; 464 465 pr_alert("Unhandled fault: %s (0x%08x) at 0x%016lx\n", 466 inf->name, esr, addr); 467 468 info.si_signo = inf->sig; 469 info.si_errno = 0; 470 info.si_code = inf->code; 471 info.si_addr = (void __user *)addr; 472 arm64_notify_die("", regs, &info, esr); 473 } 474 475 /* 476 * Handle stack alignment exceptions. 477 */ 478 asmlinkage void __exception do_sp_pc_abort(unsigned long addr, 479 unsigned int esr, 480 struct pt_regs *regs) 481 { 482 struct siginfo info; 483 484 info.si_signo = SIGBUS; 485 info.si_errno = 0; 486 info.si_code = BUS_ADRALN; 487 info.si_addr = (void __user *)addr; 488 arm64_notify_die("", regs, &info, esr); 489 } 490 491 static struct fault_info debug_fault_info[] = { 492 { do_bad, SIGTRAP, TRAP_HWBKPT, "hardware breakpoint" }, 493 { do_bad, SIGTRAP, TRAP_HWBKPT, "hardware single-step" }, 494 { do_bad, SIGTRAP, TRAP_HWBKPT, "hardware watchpoint" }, 495 { do_bad, SIGBUS, 0, "unknown 3" }, 496 { do_bad, SIGTRAP, TRAP_BRKPT, "aarch32 BKPT" }, 497 { do_bad, SIGTRAP, 0, "aarch32 vector catch" }, 498 { do_bad, SIGTRAP, TRAP_BRKPT, "aarch64 BRK" }, 499 { do_bad, SIGBUS, 0, "unknown 7" }, 500 }; 501 502 void __init hook_debug_fault_code(int nr, 503 int (*fn)(unsigned long, unsigned int, struct pt_regs *), 504 int sig, int code, const char *name) 505 { 506 BUG_ON(nr < 0 || nr >= ARRAY_SIZE(debug_fault_info)); 507 508 debug_fault_info[nr].fn = fn; 509 debug_fault_info[nr].sig = sig; 510 debug_fault_info[nr].code = code; 511 debug_fault_info[nr].name = name; 512 } 513 514 asmlinkage int __exception do_debug_exception(unsigned long addr, 515 unsigned int esr, 516 struct pt_regs *regs) 517 { 518 const struct fault_info *inf = debug_fault_info + DBG_ESR_EVT(esr); 519 struct siginfo info; 520 521 if (!inf->fn(addr, esr, regs)) 522 return 1; 523 524 pr_alert("Unhandled debug exception: %s (0x%08x) at 0x%016lx\n", 525 inf->name, esr, addr); 526 527 info.si_signo = inf->sig; 528 info.si_errno = 0; 529 info.si_code = inf->code; 530 info.si_addr = (void __user *)addr; 531 arm64_notify_die("", regs, &info, esr); 532 533 return 0; 534 } 535