1 /* 2 * linux/arch/arm/mm/fault.c 3 * 4 * Copyright (C) 1995 Linus Torvalds 5 * Modifications for ARM processor (c) 1995-2004 Russell King 6 * 7 * This program is free software; you can redistribute it and/or modify 8 * it under the terms of the GNU General Public License version 2 as 9 * published by the Free Software Foundation. 10 */ 11 #include <linux/module.h> 12 #include <linux/signal.h> 13 #include <linux/mm.h> 14 #include <linux/hardirq.h> 15 #include <linux/init.h> 16 #include <linux/kprobes.h> 17 #include <linux/uaccess.h> 18 #include <linux/page-flags.h> 19 #include <linux/sched.h> 20 #include <linux/highmem.h> 21 #include <linux/perf_event.h> 22 23 #include <asm/system.h> 24 #include <asm/pgtable.h> 25 #include <asm/tlbflush.h> 26 27 #include "fault.h" 28 29 /* 30 * Fault status register encodings. We steal bit 31 for our own purposes. 31 */ 32 #define FSR_LNX_PF (1 << 31) 33 #define FSR_WRITE (1 << 11) 34 #define FSR_FS4 (1 << 10) 35 #define FSR_FS3_0 (15) 36 37 static inline int fsr_fs(unsigned int fsr) 38 { 39 return (fsr & FSR_FS3_0) | (fsr & FSR_FS4) >> 6; 40 } 41 42 #ifdef CONFIG_MMU 43 44 #ifdef CONFIG_KPROBES 45 static inline int notify_page_fault(struct pt_regs *regs, unsigned int fsr) 46 { 47 int ret = 0; 48 49 if (!user_mode(regs)) { 50 /* kprobe_running() needs smp_processor_id() */ 51 preempt_disable(); 52 if (kprobe_running() && kprobe_fault_handler(regs, fsr)) 53 ret = 1; 54 preempt_enable(); 55 } 56 57 return ret; 58 } 59 #else 60 static inline int notify_page_fault(struct pt_regs *regs, unsigned int fsr) 61 { 62 return 0; 63 } 64 #endif 65 66 /* 67 * This is useful to dump out the page tables associated with 68 * 'addr' in mm 'mm'. 69 */ 70 void show_pte(struct mm_struct *mm, unsigned long addr) 71 { 72 pgd_t *pgd; 73 74 if (!mm) 75 mm = &init_mm; 76 77 printk(KERN_ALERT "pgd = %p\n", mm->pgd); 78 pgd = pgd_offset(mm, addr); 79 printk(KERN_ALERT "[%08lx] *pgd=%08llx", 80 addr, (long long)pgd_val(*pgd)); 81 82 do { 83 pud_t *pud; 84 pmd_t *pmd; 85 pte_t *pte; 86 87 if (pgd_none(*pgd)) 88 break; 89 90 if (pgd_bad(*pgd)) { 91 printk("(bad)"); 92 break; 93 } 94 95 pud = pud_offset(pgd, addr); 96 if (PTRS_PER_PUD != 1) 97 printk(", *pud=%08llx", (long long)pud_val(*pud)); 98 99 if (pud_none(*pud)) 100 break; 101 102 if (pud_bad(*pud)) { 103 printk("(bad)"); 104 break; 105 } 106 107 pmd = pmd_offset(pud, addr); 108 if (PTRS_PER_PMD != 1) 109 printk(", *pmd=%08llx", (long long)pmd_val(*pmd)); 110 111 if (pmd_none(*pmd)) 112 break; 113 114 if (pmd_bad(*pmd)) { 115 printk("(bad)"); 116 break; 117 } 118 119 /* We must not map this if we have highmem enabled */ 120 if (PageHighMem(pfn_to_page(pmd_val(*pmd) >> PAGE_SHIFT))) 121 break; 122 123 pte = pte_offset_map(pmd, addr); 124 printk(", *pte=%08llx", (long long)pte_val(*pte)); 125 printk(", *ppte=%08llx", 126 (long long)pte_val(pte[PTE_HWTABLE_PTRS])); 127 pte_unmap(pte); 128 } while(0); 129 130 printk("\n"); 131 } 132 #else /* CONFIG_MMU */ 133 void show_pte(struct mm_struct *mm, unsigned long addr) 134 { } 135 #endif /* CONFIG_MMU */ 136 137 /* 138 * Oops. The kernel tried to access some page that wasn't present. 139 */ 140 static void 141 __do_kernel_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr, 142 struct pt_regs *regs) 143 { 144 /* 145 * Are we prepared to handle this kernel fault? 146 */ 147 if (fixup_exception(regs)) 148 return; 149 150 /* 151 * No handler, we'll have to terminate things with extreme prejudice. 152 */ 153 bust_spinlocks(1); 154 printk(KERN_ALERT 155 "Unable to handle kernel %s at virtual address %08lx\n", 156 (addr < PAGE_SIZE) ? "NULL pointer dereference" : 157 "paging request", addr); 158 159 show_pte(mm, addr); 160 die("Oops", regs, fsr); 161 bust_spinlocks(0); 162 do_exit(SIGKILL); 163 } 164 165 /* 166 * Something tried to access memory that isn't in our memory map.. 167 * User mode accesses just cause a SIGSEGV 168 */ 169 static void 170 __do_user_fault(struct task_struct *tsk, unsigned long addr, 171 unsigned int fsr, unsigned int sig, int code, 172 struct pt_regs *regs) 173 { 174 struct siginfo si; 175 176 #ifdef CONFIG_DEBUG_USER 177 if (user_debug & UDBG_SEGV) { 178 printk(KERN_DEBUG "%s: unhandled page fault (%d) at 0x%08lx, code 0x%03x\n", 179 tsk->comm, sig, addr, fsr); 180 show_pte(tsk->mm, addr); 181 show_regs(regs); 182 } 183 #endif 184 185 tsk->thread.address = addr; 186 tsk->thread.error_code = fsr; 187 tsk->thread.trap_no = 14; 188 si.si_signo = sig; 189 si.si_errno = 0; 190 si.si_code = code; 191 si.si_addr = (void __user *)addr; 192 force_sig_info(sig, &si, tsk); 193 } 194 195 void do_bad_area(unsigned long addr, unsigned int fsr, struct pt_regs *regs) 196 { 197 struct task_struct *tsk = current; 198 struct mm_struct *mm = tsk->active_mm; 199 200 /* 201 * If we are in kernel mode at this point, we 202 * have no context to handle this fault with. 203 */ 204 if (user_mode(regs)) 205 __do_user_fault(tsk, addr, fsr, SIGSEGV, SEGV_MAPERR, regs); 206 else 207 __do_kernel_fault(mm, addr, fsr, regs); 208 } 209 210 #ifdef CONFIG_MMU 211 #define VM_FAULT_BADMAP 0x010000 212 #define VM_FAULT_BADACCESS 0x020000 213 214 /* 215 * Check that the permissions on the VMA allow for the fault which occurred. 216 * If we encountered a write fault, we must have write permission, otherwise 217 * we allow any permission. 218 */ 219 static inline bool access_error(unsigned int fsr, struct vm_area_struct *vma) 220 { 221 unsigned int mask = VM_READ | VM_WRITE | VM_EXEC; 222 223 if (fsr & FSR_WRITE) 224 mask = VM_WRITE; 225 if (fsr & FSR_LNX_PF) 226 mask = VM_EXEC; 227 228 return vma->vm_flags & mask ? false : true; 229 } 230 231 static int __kprobes 232 __do_page_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr, 233 struct task_struct *tsk) 234 { 235 struct vm_area_struct *vma; 236 int fault; 237 238 vma = find_vma(mm, addr); 239 fault = VM_FAULT_BADMAP; 240 if (unlikely(!vma)) 241 goto out; 242 if (unlikely(vma->vm_start > addr)) 243 goto check_stack; 244 245 /* 246 * Ok, we have a good vm_area for this 247 * memory access, so we can handle it. 248 */ 249 good_area: 250 if (access_error(fsr, vma)) { 251 fault = VM_FAULT_BADACCESS; 252 goto out; 253 } 254 255 /* 256 * If for any reason at all we couldn't handle the fault, make 257 * sure we exit gracefully rather than endlessly redo the fault. 258 */ 259 fault = handle_mm_fault(mm, vma, addr & PAGE_MASK, (fsr & FSR_WRITE) ? FAULT_FLAG_WRITE : 0); 260 if (unlikely(fault & VM_FAULT_ERROR)) 261 return fault; 262 if (fault & VM_FAULT_MAJOR) 263 tsk->maj_flt++; 264 else 265 tsk->min_flt++; 266 return fault; 267 268 check_stack: 269 if (vma->vm_flags & VM_GROWSDOWN && !expand_stack(vma, addr)) 270 goto good_area; 271 out: 272 return fault; 273 } 274 275 static int __kprobes 276 do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs) 277 { 278 struct task_struct *tsk; 279 struct mm_struct *mm; 280 int fault, sig, code; 281 282 if (notify_page_fault(regs, fsr)) 283 return 0; 284 285 tsk = current; 286 mm = tsk->mm; 287 288 /* Enable interrupts if they were enabled in the parent context. */ 289 if (interrupts_enabled(regs)) 290 local_irq_enable(); 291 292 /* 293 * If we're in an interrupt or have no user 294 * context, we must not take the fault.. 295 */ 296 if (in_atomic() || !mm) 297 goto no_context; 298 299 /* 300 * As per x86, we may deadlock here. However, since the kernel only 301 * validly references user space from well defined areas of the code, 302 * we can bug out early if this is from code which shouldn't. 303 */ 304 if (!down_read_trylock(&mm->mmap_sem)) { 305 if (!user_mode(regs) && !search_exception_tables(regs->ARM_pc)) 306 goto no_context; 307 down_read(&mm->mmap_sem); 308 } else { 309 /* 310 * The above down_read_trylock() might have succeeded in 311 * which case, we'll have missed the might_sleep() from 312 * down_read() 313 */ 314 might_sleep(); 315 #ifdef CONFIG_DEBUG_VM 316 if (!user_mode(regs) && 317 !search_exception_tables(regs->ARM_pc)) 318 goto no_context; 319 #endif 320 } 321 322 fault = __do_page_fault(mm, addr, fsr, tsk); 323 up_read(&mm->mmap_sem); 324 325 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr); 326 if (fault & VM_FAULT_MAJOR) 327 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, addr); 328 else if (fault & VM_FAULT_MINOR) 329 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, addr); 330 331 /* 332 * Handle the "normal" case first - VM_FAULT_MAJOR / VM_FAULT_MINOR 333 */ 334 if (likely(!(fault & (VM_FAULT_ERROR | VM_FAULT_BADMAP | VM_FAULT_BADACCESS)))) 335 return 0; 336 337 if (fault & VM_FAULT_OOM) { 338 /* 339 * We ran out of memory, call the OOM killer, and return to 340 * userspace (which will retry the fault, or kill us if we 341 * got oom-killed) 342 */ 343 pagefault_out_of_memory(); 344 return 0; 345 } 346 347 /* 348 * If we are in kernel mode at this point, we 349 * have no context to handle this fault with. 350 */ 351 if (!user_mode(regs)) 352 goto no_context; 353 354 if (fault & VM_FAULT_SIGBUS) { 355 /* 356 * We had some memory, but were unable to 357 * successfully fix up this page fault. 358 */ 359 sig = SIGBUS; 360 code = BUS_ADRERR; 361 } else { 362 /* 363 * Something tried to access memory that 364 * isn't in our memory map.. 365 */ 366 sig = SIGSEGV; 367 code = fault == VM_FAULT_BADACCESS ? 368 SEGV_ACCERR : SEGV_MAPERR; 369 } 370 371 __do_user_fault(tsk, addr, fsr, sig, code, regs); 372 return 0; 373 374 no_context: 375 __do_kernel_fault(mm, addr, fsr, regs); 376 return 0; 377 } 378 #else /* CONFIG_MMU */ 379 static int 380 do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs) 381 { 382 return 0; 383 } 384 #endif /* CONFIG_MMU */ 385 386 /* 387 * First Level Translation Fault Handler 388 * 389 * We enter here because the first level page table doesn't contain 390 * a valid entry for the address. 391 * 392 * If the address is in kernel space (>= TASK_SIZE), then we are 393 * probably faulting in the vmalloc() area. 394 * 395 * If the init_task's first level page tables contains the relevant 396 * entry, we copy the it to this task. If not, we send the process 397 * a signal, fixup the exception, or oops the kernel. 398 * 399 * NOTE! We MUST NOT take any locks for this case. We may be in an 400 * interrupt or a critical region, and should only copy the information 401 * from the master page table, nothing more. 402 */ 403 #ifdef CONFIG_MMU 404 static int __kprobes 405 do_translation_fault(unsigned long addr, unsigned int fsr, 406 struct pt_regs *regs) 407 { 408 unsigned int index; 409 pgd_t *pgd, *pgd_k; 410 pud_t *pud, *pud_k; 411 pmd_t *pmd, *pmd_k; 412 413 if (addr < TASK_SIZE) 414 return do_page_fault(addr, fsr, regs); 415 416 if (user_mode(regs)) 417 goto bad_area; 418 419 index = pgd_index(addr); 420 421 /* 422 * FIXME: CP15 C1 is write only on ARMv3 architectures. 423 */ 424 pgd = cpu_get_pgd() + index; 425 pgd_k = init_mm.pgd + index; 426 427 if (pgd_none(*pgd_k)) 428 goto bad_area; 429 if (!pgd_present(*pgd)) 430 set_pgd(pgd, *pgd_k); 431 432 pud = pud_offset(pgd, addr); 433 pud_k = pud_offset(pgd_k, addr); 434 435 if (pud_none(*pud_k)) 436 goto bad_area; 437 if (!pud_present(*pud)) 438 set_pud(pud, *pud_k); 439 440 pmd = pmd_offset(pud, addr); 441 pmd_k = pmd_offset(pud_k, addr); 442 443 /* 444 * On ARM one Linux PGD entry contains two hardware entries (see page 445 * tables layout in pgtable.h). We normally guarantee that we always 446 * fill both L1 entries. But create_mapping() doesn't follow the rule. 447 * It can create inidividual L1 entries, so here we have to call 448 * pmd_none() check for the entry really corresponded to address, not 449 * for the first of pair. 450 */ 451 index = (addr >> SECTION_SHIFT) & 1; 452 if (pmd_none(pmd_k[index])) 453 goto bad_area; 454 455 copy_pmd(pmd, pmd_k); 456 return 0; 457 458 bad_area: 459 do_bad_area(addr, fsr, regs); 460 return 0; 461 } 462 #else /* CONFIG_MMU */ 463 static int 464 do_translation_fault(unsigned long addr, unsigned int fsr, 465 struct pt_regs *regs) 466 { 467 return 0; 468 } 469 #endif /* CONFIG_MMU */ 470 471 /* 472 * Some section permission faults need to be handled gracefully. 473 * They can happen due to a __{get,put}_user during an oops. 474 */ 475 static int 476 do_sect_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs) 477 { 478 do_bad_area(addr, fsr, regs); 479 return 0; 480 } 481 482 /* 483 * This abort handler always returns "fault". 484 */ 485 static int 486 do_bad(unsigned long addr, unsigned int fsr, struct pt_regs *regs) 487 { 488 return 1; 489 } 490 491 static struct fsr_info { 492 int (*fn)(unsigned long addr, unsigned int fsr, struct pt_regs *regs); 493 int sig; 494 int code; 495 const char *name; 496 } fsr_info[] = { 497 /* 498 * The following are the standard ARMv3 and ARMv4 aborts. ARMv5 499 * defines these to be "precise" aborts. 500 */ 501 { do_bad, SIGSEGV, 0, "vector exception" }, 502 { do_bad, SIGBUS, BUS_ADRALN, "alignment exception" }, 503 { do_bad, SIGKILL, 0, "terminal exception" }, 504 { do_bad, SIGBUS, BUS_ADRALN, "alignment exception" }, 505 { do_bad, SIGBUS, 0, "external abort on linefetch" }, 506 { do_translation_fault, SIGSEGV, SEGV_MAPERR, "section translation fault" }, 507 { do_bad, SIGBUS, 0, "external abort on linefetch" }, 508 { do_page_fault, SIGSEGV, SEGV_MAPERR, "page translation fault" }, 509 { do_bad, SIGBUS, 0, "external abort on non-linefetch" }, 510 { do_bad, SIGSEGV, SEGV_ACCERR, "section domain fault" }, 511 { do_bad, SIGBUS, 0, "external abort on non-linefetch" }, 512 { do_bad, SIGSEGV, SEGV_ACCERR, "page domain fault" }, 513 { do_bad, SIGBUS, 0, "external abort on translation" }, 514 { do_sect_fault, SIGSEGV, SEGV_ACCERR, "section permission fault" }, 515 { do_bad, SIGBUS, 0, "external abort on translation" }, 516 { do_page_fault, SIGSEGV, SEGV_ACCERR, "page permission fault" }, 517 /* 518 * The following are "imprecise" aborts, which are signalled by bit 519 * 10 of the FSR, and may not be recoverable. These are only 520 * supported if the CPU abort handler supports bit 10. 521 */ 522 { do_bad, SIGBUS, 0, "unknown 16" }, 523 { do_bad, SIGBUS, 0, "unknown 17" }, 524 { do_bad, SIGBUS, 0, "unknown 18" }, 525 { do_bad, SIGBUS, 0, "unknown 19" }, 526 { do_bad, SIGBUS, 0, "lock abort" }, /* xscale */ 527 { do_bad, SIGBUS, 0, "unknown 21" }, 528 { do_bad, SIGBUS, BUS_OBJERR, "imprecise external abort" }, /* xscale */ 529 { do_bad, SIGBUS, 0, "unknown 23" }, 530 { do_bad, SIGBUS, 0, "dcache parity error" }, /* xscale */ 531 { do_bad, SIGBUS, 0, "unknown 25" }, 532 { do_bad, SIGBUS, 0, "unknown 26" }, 533 { do_bad, SIGBUS, 0, "unknown 27" }, 534 { do_bad, SIGBUS, 0, "unknown 28" }, 535 { do_bad, SIGBUS, 0, "unknown 29" }, 536 { do_bad, SIGBUS, 0, "unknown 30" }, 537 { do_bad, SIGBUS, 0, "unknown 31" } 538 }; 539 540 void __init 541 hook_fault_code(int nr, int (*fn)(unsigned long, unsigned int, struct pt_regs *), 542 int sig, int code, const char *name) 543 { 544 if (nr < 0 || nr >= ARRAY_SIZE(fsr_info)) 545 BUG(); 546 547 fsr_info[nr].fn = fn; 548 fsr_info[nr].sig = sig; 549 fsr_info[nr].code = code; 550 fsr_info[nr].name = name; 551 } 552 553 /* 554 * Dispatch a data abort to the relevant handler. 555 */ 556 asmlinkage void __exception 557 do_DataAbort(unsigned long addr, unsigned int fsr, struct pt_regs *regs) 558 { 559 const struct fsr_info *inf = fsr_info + fsr_fs(fsr); 560 struct siginfo info; 561 562 if (!inf->fn(addr, fsr & ~FSR_LNX_PF, regs)) 563 return; 564 565 printk(KERN_ALERT "Unhandled fault: %s (0x%03x) at 0x%08lx\n", 566 inf->name, fsr, addr); 567 568 info.si_signo = inf->sig; 569 info.si_errno = 0; 570 info.si_code = inf->code; 571 info.si_addr = (void __user *)addr; 572 arm_notify_die("", regs, &info, fsr, 0); 573 } 574 575 576 static struct fsr_info ifsr_info[] = { 577 { do_bad, SIGBUS, 0, "unknown 0" }, 578 { do_bad, SIGBUS, 0, "unknown 1" }, 579 { do_bad, SIGBUS, 0, "debug event" }, 580 { do_bad, SIGSEGV, SEGV_ACCERR, "section access flag fault" }, 581 { do_bad, SIGBUS, 0, "unknown 4" }, 582 { do_translation_fault, SIGSEGV, SEGV_MAPERR, "section translation fault" }, 583 { do_bad, SIGSEGV, SEGV_ACCERR, "page access flag fault" }, 584 { do_page_fault, SIGSEGV, SEGV_MAPERR, "page translation fault" }, 585 { do_bad, SIGBUS, 0, "external abort on non-linefetch" }, 586 { do_bad, SIGSEGV, SEGV_ACCERR, "section domain fault" }, 587 { do_bad, SIGBUS, 0, "unknown 10" }, 588 { do_bad, SIGSEGV, SEGV_ACCERR, "page domain fault" }, 589 { do_bad, SIGBUS, 0, "external abort on translation" }, 590 { do_sect_fault, SIGSEGV, SEGV_ACCERR, "section permission fault" }, 591 { do_bad, SIGBUS, 0, "external abort on translation" }, 592 { do_page_fault, SIGSEGV, SEGV_ACCERR, "page permission fault" }, 593 { do_bad, SIGBUS, 0, "unknown 16" }, 594 { do_bad, SIGBUS, 0, "unknown 17" }, 595 { do_bad, SIGBUS, 0, "unknown 18" }, 596 { do_bad, SIGBUS, 0, "unknown 19" }, 597 { do_bad, SIGBUS, 0, "unknown 20" }, 598 { do_bad, SIGBUS, 0, "unknown 21" }, 599 { do_bad, SIGBUS, 0, "unknown 22" }, 600 { do_bad, SIGBUS, 0, "unknown 23" }, 601 { do_bad, SIGBUS, 0, "unknown 24" }, 602 { do_bad, SIGBUS, 0, "unknown 25" }, 603 { do_bad, SIGBUS, 0, "unknown 26" }, 604 { do_bad, SIGBUS, 0, "unknown 27" }, 605 { do_bad, SIGBUS, 0, "unknown 28" }, 606 { do_bad, SIGBUS, 0, "unknown 29" }, 607 { do_bad, SIGBUS, 0, "unknown 30" }, 608 { do_bad, SIGBUS, 0, "unknown 31" }, 609 }; 610 611 void __init 612 hook_ifault_code(int nr, int (*fn)(unsigned long, unsigned int, struct pt_regs *), 613 int sig, int code, const char *name) 614 { 615 if (nr < 0 || nr >= ARRAY_SIZE(ifsr_info)) 616 BUG(); 617 618 ifsr_info[nr].fn = fn; 619 ifsr_info[nr].sig = sig; 620 ifsr_info[nr].code = code; 621 ifsr_info[nr].name = name; 622 } 623 624 asmlinkage void __exception 625 do_PrefetchAbort(unsigned long addr, unsigned int ifsr, struct pt_regs *regs) 626 { 627 const struct fsr_info *inf = ifsr_info + fsr_fs(ifsr); 628 struct siginfo info; 629 630 if (!inf->fn(addr, ifsr | FSR_LNX_PF, regs)) 631 return; 632 633 printk(KERN_ALERT "Unhandled prefetch abort: %s (0x%03x) at 0x%08lx\n", 634 inf->name, ifsr, addr); 635 636 info.si_signo = inf->sig; 637 info.si_errno = 0; 638 info.si_code = inf->code; 639 info.si_addr = (void __user *)addr; 640 arm_notify_die("", regs, &info, ifsr, 0); 641 } 642 643 static int __init exceptions_init(void) 644 { 645 if (cpu_architecture() >= CPU_ARCH_ARMv6) { 646 hook_fault_code(4, do_translation_fault, SIGSEGV, SEGV_MAPERR, 647 "I-cache maintenance fault"); 648 } 649 650 if (cpu_architecture() >= CPU_ARCH_ARMv7) { 651 /* 652 * TODO: Access flag faults introduced in ARMv6K. 653 * Runtime check for 'K' extension is needed 654 */ 655 hook_fault_code(3, do_bad, SIGSEGV, SEGV_MAPERR, 656 "section access flag fault"); 657 hook_fault_code(6, do_bad, SIGSEGV, SEGV_MAPERR, 658 "section access flag fault"); 659 } 660 661 return 0; 662 } 663 664 arch_initcall(exceptions_init); 665