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/cpufeature.h> 34 #include <asm/exception.h> 35 #include <asm/debug-monitors.h> 36 #include <asm/esr.h> 37 #include <asm/sysreg.h> 38 #include <asm/system_misc.h> 39 #include <asm/pgtable.h> 40 #include <asm/tlbflush.h> 41 42 static const char *fault_name(unsigned int esr); 43 44 /* 45 * Dump out the page tables associated with 'addr' in mm 'mm'. 46 */ 47 void show_pte(struct mm_struct *mm, unsigned long addr) 48 { 49 pgd_t *pgd; 50 51 if (!mm) 52 mm = &init_mm; 53 54 pr_alert("pgd = %p\n", mm->pgd); 55 pgd = pgd_offset(mm, addr); 56 pr_alert("[%08lx] *pgd=%016llx", addr, pgd_val(*pgd)); 57 58 do { 59 pud_t *pud; 60 pmd_t *pmd; 61 pte_t *pte; 62 63 if (pgd_none(*pgd) || pgd_bad(*pgd)) 64 break; 65 66 pud = pud_offset(pgd, addr); 67 printk(", *pud=%016llx", pud_val(*pud)); 68 if (pud_none(*pud) || pud_bad(*pud)) 69 break; 70 71 pmd = pmd_offset(pud, addr); 72 printk(", *pmd=%016llx", pmd_val(*pmd)); 73 if (pmd_none(*pmd) || pmd_bad(*pmd)) 74 break; 75 76 pte = pte_offset_map(pmd, addr); 77 printk(", *pte=%016llx", pte_val(*pte)); 78 pte_unmap(pte); 79 } while(0); 80 81 printk("\n"); 82 } 83 84 /* 85 * The kernel tried to access some page that wasn't present. 86 */ 87 static void __do_kernel_fault(struct mm_struct *mm, unsigned long addr, 88 unsigned int esr, struct pt_regs *regs) 89 { 90 /* 91 * Are we prepared to handle this kernel fault? 92 */ 93 if (fixup_exception(regs)) 94 return; 95 96 /* 97 * No handler, we'll have to terminate things with extreme prejudice. 98 */ 99 bust_spinlocks(1); 100 pr_alert("Unable to handle kernel %s at virtual address %08lx\n", 101 (addr < PAGE_SIZE) ? "NULL pointer dereference" : 102 "paging request", addr); 103 104 show_pte(mm, addr); 105 die("Oops", regs, esr); 106 bust_spinlocks(0); 107 do_exit(SIGKILL); 108 } 109 110 /* 111 * Something tried to access memory that isn't in our memory map. User mode 112 * accesses just cause a SIGSEGV 113 */ 114 static void __do_user_fault(struct task_struct *tsk, unsigned long addr, 115 unsigned int esr, unsigned int sig, int code, 116 struct pt_regs *regs) 117 { 118 struct siginfo si; 119 120 if (unhandled_signal(tsk, sig) && show_unhandled_signals_ratelimited()) { 121 pr_info("%s[%d]: unhandled %s (%d) at 0x%08lx, esr 0x%03x\n", 122 tsk->comm, task_pid_nr(tsk), fault_name(esr), sig, 123 addr, esr); 124 show_pte(tsk->mm, addr); 125 show_regs(regs); 126 } 127 128 tsk->thread.fault_address = addr; 129 tsk->thread.fault_code = esr; 130 si.si_signo = sig; 131 si.si_errno = 0; 132 si.si_code = code; 133 si.si_addr = (void __user *)addr; 134 force_sig_info(sig, &si, tsk); 135 } 136 137 static void do_bad_area(unsigned long addr, unsigned int esr, struct pt_regs *regs) 138 { 139 struct task_struct *tsk = current; 140 struct mm_struct *mm = tsk->active_mm; 141 142 /* 143 * If we are in kernel mode at this point, we have no context to 144 * handle this fault with. 145 */ 146 if (user_mode(regs)) 147 __do_user_fault(tsk, addr, esr, SIGSEGV, SEGV_MAPERR, regs); 148 else 149 __do_kernel_fault(mm, addr, esr, regs); 150 } 151 152 #define VM_FAULT_BADMAP 0x010000 153 #define VM_FAULT_BADACCESS 0x020000 154 155 #define ESR_LNX_EXEC (1 << 24) 156 157 static int __do_page_fault(struct mm_struct *mm, unsigned long addr, 158 unsigned int mm_flags, unsigned long vm_flags, 159 struct task_struct *tsk) 160 { 161 struct vm_area_struct *vma; 162 int fault; 163 164 vma = find_vma(mm, addr); 165 fault = VM_FAULT_BADMAP; 166 if (unlikely(!vma)) 167 goto out; 168 if (unlikely(vma->vm_start > addr)) 169 goto check_stack; 170 171 /* 172 * Ok, we have a good vm_area for this memory access, so we can handle 173 * it. 174 */ 175 good_area: 176 /* 177 * Check that the permissions on the VMA allow for the fault which 178 * occurred. If we encountered a write or exec fault, we must have 179 * appropriate permissions, otherwise we allow any permission. 180 */ 181 if (!(vma->vm_flags & vm_flags)) { 182 fault = VM_FAULT_BADACCESS; 183 goto out; 184 } 185 186 return handle_mm_fault(mm, vma, addr & PAGE_MASK, mm_flags); 187 188 check_stack: 189 if (vma->vm_flags & VM_GROWSDOWN && !expand_stack(vma, addr)) 190 goto good_area; 191 out: 192 return fault; 193 } 194 195 static int __kprobes do_page_fault(unsigned long addr, unsigned int esr, 196 struct pt_regs *regs) 197 { 198 struct task_struct *tsk; 199 struct mm_struct *mm; 200 int fault, sig, code; 201 unsigned long vm_flags = VM_READ | VM_WRITE | VM_EXEC; 202 unsigned int mm_flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; 203 204 tsk = current; 205 mm = tsk->mm; 206 207 /* Enable interrupts if they were enabled in the parent context. */ 208 if (interrupts_enabled(regs)) 209 local_irq_enable(); 210 211 /* 212 * If we're in an interrupt or have no user context, we must not take 213 * the fault. 214 */ 215 if (faulthandler_disabled() || !mm) 216 goto no_context; 217 218 if (user_mode(regs)) 219 mm_flags |= FAULT_FLAG_USER; 220 221 if (esr & ESR_LNX_EXEC) { 222 vm_flags = VM_EXEC; 223 } else if ((esr & ESR_ELx_WNR) && !(esr & ESR_ELx_CM)) { 224 vm_flags = VM_WRITE; 225 mm_flags |= FAULT_FLAG_WRITE; 226 } 227 228 /* 229 * PAN bit set implies the fault happened in kernel space, but not 230 * in the arch's user access functions. 231 */ 232 if (IS_ENABLED(CONFIG_ARM64_PAN) && (regs->pstate & PSR_PAN_BIT)) 233 goto no_context; 234 235 /* 236 * As per x86, we may deadlock here. However, since the kernel only 237 * validly references user space from well defined areas of the code, 238 * we can bug out early if this is from code which shouldn't. 239 */ 240 if (!down_read_trylock(&mm->mmap_sem)) { 241 if (!user_mode(regs) && !search_exception_tables(regs->pc)) 242 goto no_context; 243 retry: 244 down_read(&mm->mmap_sem); 245 } else { 246 /* 247 * The above down_read_trylock() might have succeeded in which 248 * case, we'll have missed the might_sleep() from down_read(). 249 */ 250 might_sleep(); 251 #ifdef CONFIG_DEBUG_VM 252 if (!user_mode(regs) && !search_exception_tables(regs->pc)) 253 goto no_context; 254 #endif 255 } 256 257 fault = __do_page_fault(mm, addr, mm_flags, vm_flags, tsk); 258 259 /* 260 * If we need to retry but a fatal signal is pending, handle the 261 * signal first. We do not need to release the mmap_sem because it 262 * would already be released in __lock_page_or_retry in mm/filemap.c. 263 */ 264 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) 265 return 0; 266 267 /* 268 * Major/minor page fault accounting is only done on the initial 269 * attempt. If we go through a retry, it is extremely likely that the 270 * page will be found in page cache at that point. 271 */ 272 273 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr); 274 if (mm_flags & FAULT_FLAG_ALLOW_RETRY) { 275 if (fault & VM_FAULT_MAJOR) { 276 tsk->maj_flt++; 277 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, 278 addr); 279 } else { 280 tsk->min_flt++; 281 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, 282 addr); 283 } 284 if (fault & VM_FAULT_RETRY) { 285 /* 286 * Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk of 287 * starvation. 288 */ 289 mm_flags &= ~FAULT_FLAG_ALLOW_RETRY; 290 goto retry; 291 } 292 } 293 294 up_read(&mm->mmap_sem); 295 296 /* 297 * Handle the "normal" case first - VM_FAULT_MAJOR / VM_FAULT_MINOR 298 */ 299 if (likely(!(fault & (VM_FAULT_ERROR | VM_FAULT_BADMAP | 300 VM_FAULT_BADACCESS)))) 301 return 0; 302 303 /* 304 * If we are in kernel mode at this point, we have no context to 305 * handle this fault with. 306 */ 307 if (!user_mode(regs)) 308 goto no_context; 309 310 if (fault & VM_FAULT_OOM) { 311 /* 312 * We ran out of memory, call the OOM killer, and return to 313 * userspace (which will retry the fault, or kill us if we got 314 * oom-killed). 315 */ 316 pagefault_out_of_memory(); 317 return 0; 318 } 319 320 if (fault & VM_FAULT_SIGBUS) { 321 /* 322 * We had some memory, but were unable to successfully fix up 323 * this page fault. 324 */ 325 sig = SIGBUS; 326 code = BUS_ADRERR; 327 } else { 328 /* 329 * Something tried to access memory that isn't in our memory 330 * map. 331 */ 332 sig = SIGSEGV; 333 code = fault == VM_FAULT_BADACCESS ? 334 SEGV_ACCERR : SEGV_MAPERR; 335 } 336 337 __do_user_fault(tsk, addr, esr, sig, code, regs); 338 return 0; 339 340 no_context: 341 __do_kernel_fault(mm, addr, esr, regs); 342 return 0; 343 } 344 345 /* 346 * First Level Translation Fault Handler 347 * 348 * We enter here because the first level page table doesn't contain a valid 349 * entry for the address. 350 * 351 * If the address is in kernel space (>= TASK_SIZE), then we are probably 352 * faulting in the vmalloc() area. 353 * 354 * If the init_task's first level page tables contains the relevant entry, we 355 * copy the it to this task. If not, we send the process a signal, fixup the 356 * exception, or oops the kernel. 357 * 358 * NOTE! We MUST NOT take any locks for this case. We may be in an interrupt 359 * or a critical region, and should only copy the information from the master 360 * page table, nothing more. 361 */ 362 static int __kprobes do_translation_fault(unsigned long addr, 363 unsigned int esr, 364 struct pt_regs *regs) 365 { 366 if (addr < TASK_SIZE) 367 return do_page_fault(addr, esr, 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, "level 0 translation 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_page_fault, SIGSEGV, SEGV_ACCERR, "level 1 access flag fault" }, 397 { do_page_fault, 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_page_fault, SIGSEGV, SEGV_ACCERR, "level 1 permission fault" }, 401 { do_page_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 static const char *fault_name(unsigned int esr) 454 { 455 const struct fault_info *inf = fault_info + (esr & 63); 456 return inf->name; 457 } 458 459 /* 460 * Dispatch a data abort to the relevant handler. 461 */ 462 asmlinkage void __exception do_mem_abort(unsigned long addr, unsigned int esr, 463 struct pt_regs *regs) 464 { 465 const struct fault_info *inf = fault_info + (esr & 63); 466 struct siginfo info; 467 468 if (!inf->fn(addr, esr, regs)) 469 return; 470 471 pr_alert("Unhandled fault: %s (0x%08x) at 0x%016lx\n", 472 inf->name, esr, addr); 473 474 info.si_signo = inf->sig; 475 info.si_errno = 0; 476 info.si_code = inf->code; 477 info.si_addr = (void __user *)addr; 478 arm64_notify_die("", regs, &info, esr); 479 } 480 481 /* 482 * Handle stack alignment exceptions. 483 */ 484 asmlinkage void __exception do_sp_pc_abort(unsigned long addr, 485 unsigned int esr, 486 struct pt_regs *regs) 487 { 488 struct siginfo info; 489 struct task_struct *tsk = current; 490 491 if (show_unhandled_signals && unhandled_signal(tsk, SIGBUS)) 492 pr_info_ratelimited("%s[%d]: %s exception: pc=%p sp=%p\n", 493 tsk->comm, task_pid_nr(tsk), 494 esr_get_class_string(esr), (void *)regs->pc, 495 (void *)regs->sp); 496 497 info.si_signo = SIGBUS; 498 info.si_errno = 0; 499 info.si_code = BUS_ADRALN; 500 info.si_addr = (void __user *)addr; 501 arm64_notify_die("Oops - SP/PC alignment exception", regs, &info, esr); 502 } 503 504 int __init early_brk64(unsigned long addr, unsigned int esr, 505 struct pt_regs *regs); 506 507 /* 508 * __refdata because early_brk64 is __init, but the reference to it is 509 * clobbered at arch_initcall time. 510 * See traps.c and debug-monitors.c:debug_traps_init(). 511 */ 512 static struct fault_info __refdata debug_fault_info[] = { 513 { do_bad, SIGTRAP, TRAP_HWBKPT, "hardware breakpoint" }, 514 { do_bad, SIGTRAP, TRAP_HWBKPT, "hardware single-step" }, 515 { do_bad, SIGTRAP, TRAP_HWBKPT, "hardware watchpoint" }, 516 { do_bad, SIGBUS, 0, "unknown 3" }, 517 { do_bad, SIGTRAP, TRAP_BRKPT, "aarch32 BKPT" }, 518 { do_bad, SIGTRAP, 0, "aarch32 vector catch" }, 519 { early_brk64, SIGTRAP, TRAP_BRKPT, "aarch64 BRK" }, 520 { do_bad, SIGBUS, 0, "unknown 7" }, 521 }; 522 523 void __init hook_debug_fault_code(int nr, 524 int (*fn)(unsigned long, unsigned int, struct pt_regs *), 525 int sig, int code, const char *name) 526 { 527 BUG_ON(nr < 0 || nr >= ARRAY_SIZE(debug_fault_info)); 528 529 debug_fault_info[nr].fn = fn; 530 debug_fault_info[nr].sig = sig; 531 debug_fault_info[nr].code = code; 532 debug_fault_info[nr].name = name; 533 } 534 535 asmlinkage int __exception do_debug_exception(unsigned long addr, 536 unsigned int esr, 537 struct pt_regs *regs) 538 { 539 const struct fault_info *inf = debug_fault_info + DBG_ESR_EVT(esr); 540 struct siginfo info; 541 542 if (!inf->fn(addr, esr, regs)) 543 return 1; 544 545 pr_alert("Unhandled debug exception: %s (0x%08x) at 0x%016lx\n", 546 inf->name, esr, addr); 547 548 info.si_signo = inf->sig; 549 info.si_errno = 0; 550 info.si_code = inf->code; 551 info.si_addr = (void __user *)addr; 552 arm64_notify_die("", regs, &info, 0); 553 554 return 0; 555 } 556 557 #ifdef CONFIG_ARM64_PAN 558 void cpu_enable_pan(void) 559 { 560 config_sctlr_el1(SCTLR_EL1_SPAN, 0); 561 } 562 #endif /* CONFIG_ARM64_PAN */ 563