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 static const char *fault_name(unsigned int esr); 40 41 /* 42 * Dump out the page tables associated with 'addr' in mm 'mm'. 43 */ 44 void show_pte(struct mm_struct *mm, unsigned long addr) 45 { 46 pgd_t *pgd; 47 48 if (!mm) 49 mm = &init_mm; 50 51 pr_alert("pgd = %p\n", mm->pgd); 52 pgd = pgd_offset(mm, addr); 53 pr_alert("[%08lx] *pgd=%016llx", addr, pgd_val(*pgd)); 54 55 do { 56 pud_t *pud; 57 pmd_t *pmd; 58 pte_t *pte; 59 60 if (pgd_none_or_clear_bad(pgd)) 61 break; 62 63 pud = pud_offset(pgd, addr); 64 if (pud_none_or_clear_bad(pud)) 65 break; 66 67 pmd = pmd_offset(pud, addr); 68 printk(", *pmd=%016llx", pmd_val(*pmd)); 69 if (pmd_none_or_clear_bad(pmd)) 70 break; 71 72 pte = pte_offset_map(pmd, addr); 73 printk(", *pte=%016llx", pte_val(*pte)); 74 pte_unmap(pte); 75 } while(0); 76 77 printk("\n"); 78 } 79 80 /* 81 * The kernel tried to access some page that wasn't present. 82 */ 83 static void __do_kernel_fault(struct mm_struct *mm, unsigned long addr, 84 unsigned int esr, struct pt_regs *regs) 85 { 86 /* 87 * Are we prepared to handle this kernel fault? 88 */ 89 if (fixup_exception(regs)) 90 return; 91 92 /* 93 * No handler, we'll have to terminate things with extreme prejudice. 94 */ 95 bust_spinlocks(1); 96 pr_alert("Unable to handle kernel %s at virtual address %08lx\n", 97 (addr < PAGE_SIZE) ? "NULL pointer dereference" : 98 "paging request", addr); 99 100 show_pte(mm, addr); 101 die("Oops", regs, esr); 102 bust_spinlocks(0); 103 do_exit(SIGKILL); 104 } 105 106 /* 107 * Something tried to access memory that isn't in our memory map. User mode 108 * accesses just cause a SIGSEGV 109 */ 110 static void __do_user_fault(struct task_struct *tsk, unsigned long addr, 111 unsigned int esr, unsigned int sig, int code, 112 struct pt_regs *regs) 113 { 114 struct siginfo si; 115 116 if (show_unhandled_signals) { 117 pr_info("%s[%d]: unhandled %s (%d) at 0x%08lx, esr 0x%03x\n", 118 tsk->comm, task_pid_nr(tsk), fault_name(esr), sig, 119 addr, esr); 120 show_pte(tsk->mm, addr); 121 show_regs(regs); 122 } 123 124 tsk->thread.fault_address = addr; 125 si.si_signo = sig; 126 si.si_errno = 0; 127 si.si_code = code; 128 si.si_addr = (void __user *)addr; 129 force_sig_info(sig, &si, tsk); 130 } 131 132 void do_bad_area(unsigned long addr, unsigned int esr, struct pt_regs *regs) 133 { 134 struct task_struct *tsk = current; 135 struct mm_struct *mm = tsk->active_mm; 136 137 /* 138 * If we are in kernel mode at this point, we have no context to 139 * handle this fault with. 140 */ 141 if (user_mode(regs)) 142 __do_user_fault(tsk, addr, esr, SIGSEGV, SEGV_MAPERR, regs); 143 else 144 __do_kernel_fault(mm, addr, esr, regs); 145 } 146 147 #define VM_FAULT_BADMAP 0x010000 148 #define VM_FAULT_BADACCESS 0x020000 149 150 #define ESR_WRITE (1 << 6) 151 #define ESR_LNX_EXEC (1 << 24) 152 153 /* 154 * Check that the permissions on the VMA allow for the fault which occurred. 155 * If we encountered a write fault, we must have write permission, otherwise 156 * we allow any permission. 157 */ 158 static inline bool access_error(unsigned int esr, struct vm_area_struct *vma) 159 { 160 unsigned int mask = VM_READ | VM_WRITE | VM_EXEC; 161 162 if (esr & ESR_WRITE) 163 mask = VM_WRITE; 164 if (esr & ESR_LNX_EXEC) 165 mask = VM_EXEC; 166 167 return vma->vm_flags & mask ? false : true; 168 } 169 170 static int __do_page_fault(struct mm_struct *mm, unsigned long addr, 171 unsigned int esr, unsigned int flags, 172 struct task_struct *tsk) 173 { 174 struct vm_area_struct *vma; 175 int fault; 176 177 vma = find_vma(mm, addr); 178 fault = VM_FAULT_BADMAP; 179 if (unlikely(!vma)) 180 goto out; 181 if (unlikely(vma->vm_start > addr)) 182 goto check_stack; 183 184 /* 185 * Ok, we have a good vm_area for this memory access, so we can handle 186 * it. 187 */ 188 good_area: 189 if (access_error(esr, vma)) { 190 fault = VM_FAULT_BADACCESS; 191 goto out; 192 } 193 194 return handle_mm_fault(mm, vma, addr & PAGE_MASK, flags); 195 196 check_stack: 197 if (vma->vm_flags & VM_GROWSDOWN && !expand_stack(vma, addr)) 198 goto good_area; 199 out: 200 return fault; 201 } 202 203 static int __kprobes do_page_fault(unsigned long addr, unsigned int esr, 204 struct pt_regs *regs) 205 { 206 struct task_struct *tsk; 207 struct mm_struct *mm; 208 int fault, sig, code; 209 int write = esr & ESR_WRITE; 210 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE | 211 (write ? FAULT_FLAG_WRITE : 0); 212 213 tsk = current; 214 mm = tsk->mm; 215 216 /* Enable interrupts if they were enabled in the parent context. */ 217 if (interrupts_enabled(regs)) 218 local_irq_enable(); 219 220 /* 221 * If we're in an interrupt or have no user context, we must not take 222 * the fault. 223 */ 224 if (in_atomic() || !mm) 225 goto no_context; 226 227 /* 228 * As per x86, we may deadlock here. However, since the kernel only 229 * validly references user space from well defined areas of the code, 230 * we can bug out early if this is from code which shouldn't. 231 */ 232 if (!down_read_trylock(&mm->mmap_sem)) { 233 if (!user_mode(regs) && !search_exception_tables(regs->pc)) 234 goto no_context; 235 retry: 236 down_read(&mm->mmap_sem); 237 } else { 238 /* 239 * The above down_read_trylock() might have succeeded in which 240 * case, we'll have missed the might_sleep() from down_read(). 241 */ 242 might_sleep(); 243 #ifdef CONFIG_DEBUG_VM 244 if (!user_mode(regs) && !search_exception_tables(regs->pc)) 245 goto no_context; 246 #endif 247 } 248 249 fault = __do_page_fault(mm, addr, esr, flags, tsk); 250 251 /* 252 * If we need to retry but a fatal signal is pending, handle the 253 * signal first. We do not need to release the mmap_sem because it 254 * would already be released in __lock_page_or_retry in mm/filemap.c. 255 */ 256 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) 257 return 0; 258 259 /* 260 * Major/minor page fault accounting is only done on the initial 261 * attempt. If we go through a retry, it is extremely likely that the 262 * page will be found in page cache at that point. 263 */ 264 265 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr); 266 if (flags & FAULT_FLAG_ALLOW_RETRY) { 267 if (fault & VM_FAULT_MAJOR) { 268 tsk->maj_flt++; 269 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, 270 addr); 271 } else { 272 tsk->min_flt++; 273 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, 274 addr); 275 } 276 if (fault & VM_FAULT_RETRY) { 277 /* 278 * Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk of 279 * starvation. 280 */ 281 flags &= ~FAULT_FLAG_ALLOW_RETRY; 282 goto retry; 283 } 284 } 285 286 up_read(&mm->mmap_sem); 287 288 /* 289 * Handle the "normal" case first - VM_FAULT_MAJOR / VM_FAULT_MINOR 290 */ 291 if (likely(!(fault & (VM_FAULT_ERROR | VM_FAULT_BADMAP | 292 VM_FAULT_BADACCESS)))) 293 return 0; 294 295 if (fault & VM_FAULT_OOM) { 296 /* 297 * We ran out of memory, call the OOM killer, and return to 298 * userspace (which will retry the fault, or kill us if we got 299 * oom-killed). 300 */ 301 pagefault_out_of_memory(); 302 return 0; 303 } 304 305 /* 306 * If we are in kernel mode at this point, we have no context to 307 * handle this fault with. 308 */ 309 if (!user_mode(regs)) 310 goto no_context; 311 312 if (fault & VM_FAULT_SIGBUS) { 313 /* 314 * We had some memory, but were unable to successfully fix up 315 * this page fault. 316 */ 317 sig = SIGBUS; 318 code = BUS_ADRERR; 319 } else { 320 /* 321 * Something tried to access memory that isn't in our memory 322 * map. 323 */ 324 sig = SIGSEGV; 325 code = fault == VM_FAULT_BADACCESS ? 326 SEGV_ACCERR : SEGV_MAPERR; 327 } 328 329 __do_user_fault(tsk, addr, esr, sig, code, regs); 330 return 0; 331 332 no_context: 333 __do_kernel_fault(mm, addr, esr, regs); 334 return 0; 335 } 336 337 /* 338 * First Level Translation Fault Handler 339 * 340 * We enter here because the first level page table doesn't contain a valid 341 * entry for the address. 342 * 343 * If the address is in kernel space (>= TASK_SIZE), then we are probably 344 * faulting in the vmalloc() area. 345 * 346 * If the init_task's first level page tables contains the relevant entry, we 347 * copy the it to this task. If not, we send the process a signal, fixup the 348 * exception, or oops the kernel. 349 * 350 * NOTE! We MUST NOT take any locks for this case. We may be in an interrupt 351 * or a critical region, and should only copy the information from the master 352 * page table, nothing more. 353 */ 354 static int __kprobes do_translation_fault(unsigned long addr, 355 unsigned int esr, 356 struct pt_regs *regs) 357 { 358 if (addr < TASK_SIZE) 359 return do_page_fault(addr, esr, regs); 360 361 do_bad_area(addr, esr, regs); 362 return 0; 363 } 364 365 /* 366 * Some section permission faults need to be handled gracefully. They can 367 * happen due to a __{get,put}_user during an oops. 368 */ 369 static int do_sect_fault(unsigned long addr, unsigned int esr, 370 struct pt_regs *regs) 371 { 372 do_bad_area(addr, esr, regs); 373 return 0; 374 } 375 376 /* 377 * This abort handler always returns "fault". 378 */ 379 static int do_bad(unsigned long addr, unsigned int esr, struct pt_regs *regs) 380 { 381 return 1; 382 } 383 384 static struct fault_info { 385 int (*fn)(unsigned long addr, unsigned int esr, struct pt_regs *regs); 386 int sig; 387 int code; 388 const char *name; 389 } fault_info[] = { 390 { do_bad, SIGBUS, 0, "ttbr address size fault" }, 391 { do_bad, SIGBUS, 0, "level 1 address size fault" }, 392 { do_bad, SIGBUS, 0, "level 2 address size fault" }, 393 { do_bad, SIGBUS, 0, "level 3 address size fault" }, 394 { do_translation_fault, SIGSEGV, SEGV_MAPERR, "input address range fault" }, 395 { do_translation_fault, SIGSEGV, SEGV_MAPERR, "level 1 translation fault" }, 396 { do_translation_fault, SIGSEGV, SEGV_MAPERR, "level 2 translation fault" }, 397 { do_page_fault, SIGSEGV, SEGV_MAPERR, "level 3 translation fault" }, 398 { do_bad, SIGBUS, 0, "reserved access flag fault" }, 399 { do_bad, SIGSEGV, SEGV_ACCERR, "level 1 access flag fault" }, 400 { do_bad, SIGSEGV, SEGV_ACCERR, "level 2 access flag fault" }, 401 { do_page_fault, SIGSEGV, SEGV_ACCERR, "level 3 access flag fault" }, 402 { do_bad, SIGBUS, 0, "reserved permission fault" }, 403 { do_bad, SIGSEGV, SEGV_ACCERR, "level 1 permission fault" }, 404 { do_sect_fault, SIGSEGV, SEGV_ACCERR, "level 2 permission fault" }, 405 { do_page_fault, SIGSEGV, SEGV_ACCERR, "level 3 permission fault" }, 406 { do_bad, SIGBUS, 0, "synchronous external abort" }, 407 { do_bad, SIGBUS, 0, "asynchronous external abort" }, 408 { do_bad, SIGBUS, 0, "unknown 18" }, 409 { do_bad, SIGBUS, 0, "unknown 19" }, 410 { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" }, 411 { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" }, 412 { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" }, 413 { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" }, 414 { do_bad, SIGBUS, 0, "synchronous parity error" }, 415 { do_bad, SIGBUS, 0, "asynchronous parity error" }, 416 { do_bad, SIGBUS, 0, "unknown 26" }, 417 { do_bad, SIGBUS, 0, "unknown 27" }, 418 { do_bad, SIGBUS, 0, "synchronous parity error (translation table walk" }, 419 { do_bad, SIGBUS, 0, "synchronous parity error (translation table walk" }, 420 { do_bad, SIGBUS, 0, "synchronous parity error (translation table walk" }, 421 { do_bad, SIGBUS, 0, "synchronous parity error (translation table walk" }, 422 { do_bad, SIGBUS, 0, "unknown 32" }, 423 { do_bad, SIGBUS, BUS_ADRALN, "alignment fault" }, 424 { do_bad, SIGBUS, 0, "debug event" }, 425 { do_bad, SIGBUS, 0, "unknown 35" }, 426 { do_bad, SIGBUS, 0, "unknown 36" }, 427 { do_bad, SIGBUS, 0, "unknown 37" }, 428 { do_bad, SIGBUS, 0, "unknown 38" }, 429 { do_bad, SIGBUS, 0, "unknown 39" }, 430 { do_bad, SIGBUS, 0, "unknown 40" }, 431 { do_bad, SIGBUS, 0, "unknown 41" }, 432 { do_bad, SIGBUS, 0, "unknown 42" }, 433 { do_bad, SIGBUS, 0, "unknown 43" }, 434 { do_bad, SIGBUS, 0, "unknown 44" }, 435 { do_bad, SIGBUS, 0, "unknown 45" }, 436 { do_bad, SIGBUS, 0, "unknown 46" }, 437 { do_bad, SIGBUS, 0, "unknown 47" }, 438 { do_bad, SIGBUS, 0, "unknown 48" }, 439 { do_bad, SIGBUS, 0, "unknown 49" }, 440 { do_bad, SIGBUS, 0, "unknown 50" }, 441 { do_bad, SIGBUS, 0, "unknown 51" }, 442 { do_bad, SIGBUS, 0, "implementation fault (lockdown abort)" }, 443 { do_bad, SIGBUS, 0, "unknown 53" }, 444 { do_bad, SIGBUS, 0, "unknown 54" }, 445 { do_bad, SIGBUS, 0, "unknown 55" }, 446 { do_bad, SIGBUS, 0, "unknown 56" }, 447 { do_bad, SIGBUS, 0, "unknown 57" }, 448 { do_bad, SIGBUS, 0, "implementation fault (coprocessor abort)" }, 449 { do_bad, SIGBUS, 0, "unknown 59" }, 450 { do_bad, SIGBUS, 0, "unknown 60" }, 451 { do_bad, SIGBUS, 0, "unknown 61" }, 452 { do_bad, SIGBUS, 0, "unknown 62" }, 453 { do_bad, SIGBUS, 0, "unknown 63" }, 454 }; 455 456 static const char *fault_name(unsigned int esr) 457 { 458 const struct fault_info *inf = fault_info + (esr & 63); 459 return inf->name; 460 } 461 462 /* 463 * Dispatch a data abort to the relevant handler. 464 */ 465 asmlinkage void __exception do_mem_abort(unsigned long addr, unsigned int esr, 466 struct pt_regs *regs) 467 { 468 const struct fault_info *inf = fault_info + (esr & 63); 469 struct siginfo info; 470 471 if (!inf->fn(addr, esr, regs)) 472 return; 473 474 pr_alert("Unhandled fault: %s (0x%08x) at 0x%016lx\n", 475 inf->name, esr, addr); 476 477 info.si_signo = inf->sig; 478 info.si_errno = 0; 479 info.si_code = inf->code; 480 info.si_addr = (void __user *)addr; 481 arm64_notify_die("", regs, &info, esr); 482 } 483 484 /* 485 * Handle stack alignment exceptions. 486 */ 487 asmlinkage void __exception do_sp_pc_abort(unsigned long addr, 488 unsigned int esr, 489 struct pt_regs *regs) 490 { 491 struct siginfo info; 492 493 info.si_signo = SIGBUS; 494 info.si_errno = 0; 495 info.si_code = BUS_ADRALN; 496 info.si_addr = (void __user *)addr; 497 arm64_notify_die("", regs, &info, esr); 498 } 499 500 static struct fault_info debug_fault_info[] = { 501 { do_bad, SIGTRAP, TRAP_HWBKPT, "hardware breakpoint" }, 502 { do_bad, SIGTRAP, TRAP_HWBKPT, "hardware single-step" }, 503 { do_bad, SIGTRAP, TRAP_HWBKPT, "hardware watchpoint" }, 504 { do_bad, SIGBUS, 0, "unknown 3" }, 505 { do_bad, SIGTRAP, TRAP_BRKPT, "aarch32 BKPT" }, 506 { do_bad, SIGTRAP, 0, "aarch32 vector catch" }, 507 { do_bad, SIGTRAP, TRAP_BRKPT, "aarch64 BRK" }, 508 { do_bad, SIGBUS, 0, "unknown 7" }, 509 }; 510 511 void __init hook_debug_fault_code(int nr, 512 int (*fn)(unsigned long, unsigned int, struct pt_regs *), 513 int sig, int code, const char *name) 514 { 515 BUG_ON(nr < 0 || nr >= ARRAY_SIZE(debug_fault_info)); 516 517 debug_fault_info[nr].fn = fn; 518 debug_fault_info[nr].sig = sig; 519 debug_fault_info[nr].code = code; 520 debug_fault_info[nr].name = name; 521 } 522 523 asmlinkage int __exception do_debug_exception(unsigned long addr, 524 unsigned int esr, 525 struct pt_regs *regs) 526 { 527 const struct fault_info *inf = debug_fault_info + DBG_ESR_EVT(esr); 528 struct siginfo info; 529 530 if (!inf->fn(addr, esr, regs)) 531 return 1; 532 533 pr_alert("Unhandled debug exception: %s (0x%08x) at 0x%016lx\n", 534 inf->name, esr, addr); 535 536 info.si_signo = inf->sig; 537 info.si_errno = 0; 538 info.si_code = inf->code; 539 info.si_addr = (void __user *)addr; 540 arm64_notify_die("", regs, &info, esr); 541 542 return 0; 543 } 544