1 /* 2 * S390 version 3 * Copyright IBM Corp. 1999 4 * Author(s): Hartmut Penner (hp@de.ibm.com) 5 * Ulrich Weigand (uweigand@de.ibm.com) 6 * 7 * Derived from "arch/i386/mm/fault.c" 8 * Copyright (C) 1995 Linus Torvalds 9 */ 10 11 #include <linux/kernel_stat.h> 12 #include <linux/perf_event.h> 13 #include <linux/signal.h> 14 #include <linux/sched.h> 15 #include <linux/kernel.h> 16 #include <linux/errno.h> 17 #include <linux/string.h> 18 #include <linux/types.h> 19 #include <linux/ptrace.h> 20 #include <linux/mman.h> 21 #include <linux/mm.h> 22 #include <linux/compat.h> 23 #include <linux/smp.h> 24 #include <linux/kdebug.h> 25 #include <linux/init.h> 26 #include <linux/console.h> 27 #include <linux/module.h> 28 #include <linux/hardirq.h> 29 #include <linux/kprobes.h> 30 #include <linux/uaccess.h> 31 #include <linux/hugetlb.h> 32 #include <asm/asm-offsets.h> 33 #include <asm/pgtable.h> 34 #include <asm/irq.h> 35 #include <asm/mmu_context.h> 36 #include <asm/facility.h> 37 #include "../kernel/entry.h" 38 39 #ifndef CONFIG_64BIT 40 #define __FAIL_ADDR_MASK 0x7ffff000 41 #define __SUBCODE_MASK 0x0200 42 #define __PF_RES_FIELD 0ULL 43 #else /* CONFIG_64BIT */ 44 #define __FAIL_ADDR_MASK -4096L 45 #define __SUBCODE_MASK 0x0600 46 #define __PF_RES_FIELD 0x8000000000000000ULL 47 #endif /* CONFIG_64BIT */ 48 49 #define VM_FAULT_BADCONTEXT 0x010000 50 #define VM_FAULT_BADMAP 0x020000 51 #define VM_FAULT_BADACCESS 0x040000 52 #define VM_FAULT_SIGNAL 0x080000 53 #define VM_FAULT_PFAULT 0x100000 54 55 static unsigned long store_indication __read_mostly; 56 57 #ifdef CONFIG_64BIT 58 static int __init fault_init(void) 59 { 60 if (test_facility(75)) 61 store_indication = 0xc00; 62 return 0; 63 } 64 early_initcall(fault_init); 65 #endif 66 67 static inline int notify_page_fault(struct pt_regs *regs) 68 { 69 int ret = 0; 70 71 /* kprobe_running() needs smp_processor_id() */ 72 if (kprobes_built_in() && !user_mode(regs)) { 73 preempt_disable(); 74 if (kprobe_running() && kprobe_fault_handler(regs, 14)) 75 ret = 1; 76 preempt_enable(); 77 } 78 return ret; 79 } 80 81 82 /* 83 * Unlock any spinlocks which will prevent us from getting the 84 * message out. 85 */ 86 void bust_spinlocks(int yes) 87 { 88 if (yes) { 89 oops_in_progress = 1; 90 } else { 91 int loglevel_save = console_loglevel; 92 console_unblank(); 93 oops_in_progress = 0; 94 /* 95 * OK, the message is on the console. Now we call printk() 96 * without oops_in_progress set so that printk will give klogd 97 * a poke. Hold onto your hats... 98 */ 99 console_loglevel = 15; 100 printk(" "); 101 console_loglevel = loglevel_save; 102 } 103 } 104 105 /* 106 * Returns the address space associated with the fault. 107 * Returns 0 for kernel space and 1 for user space. 108 */ 109 static inline int user_space_fault(struct pt_regs *regs) 110 { 111 unsigned long trans_exc_code; 112 113 /* 114 * The lowest two bits of the translation exception 115 * identification indicate which paging table was used. 116 */ 117 trans_exc_code = regs->int_parm_long & 3; 118 if (trans_exc_code == 3) /* home space -> kernel */ 119 return 0; 120 if (user_mode(regs)) 121 return 1; 122 if (trans_exc_code == 2) /* secondary space -> set_fs */ 123 return current->thread.mm_segment.ar4; 124 if (current->flags & PF_VCPU) 125 return 1; 126 return 0; 127 } 128 129 static int bad_address(void *p) 130 { 131 unsigned long dummy; 132 133 return probe_kernel_address((unsigned long *)p, dummy); 134 } 135 136 #ifdef CONFIG_64BIT 137 static void dump_pagetable(unsigned long asce, unsigned long address) 138 { 139 unsigned long *table = __va(asce & PAGE_MASK); 140 141 pr_alert("AS:%016lx ", asce); 142 switch (asce & _ASCE_TYPE_MASK) { 143 case _ASCE_TYPE_REGION1: 144 table = table + ((address >> 53) & 0x7ff); 145 if (bad_address(table)) 146 goto bad; 147 pr_cont("R1:%016lx ", *table); 148 if (*table & _REGION_ENTRY_INVALID) 149 goto out; 150 table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN); 151 /* fallthrough */ 152 case _ASCE_TYPE_REGION2: 153 table = table + ((address >> 42) & 0x7ff); 154 if (bad_address(table)) 155 goto bad; 156 pr_cont("R2:%016lx ", *table); 157 if (*table & _REGION_ENTRY_INVALID) 158 goto out; 159 table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN); 160 /* fallthrough */ 161 case _ASCE_TYPE_REGION3: 162 table = table + ((address >> 31) & 0x7ff); 163 if (bad_address(table)) 164 goto bad; 165 pr_cont("R3:%016lx ", *table); 166 if (*table & (_REGION_ENTRY_INVALID | _REGION3_ENTRY_LARGE)) 167 goto out; 168 table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN); 169 /* fallthrough */ 170 case _ASCE_TYPE_SEGMENT: 171 table = table + ((address >> 20) & 0x7ff); 172 if (bad_address(table)) 173 goto bad; 174 pr_cont("S:%016lx ", *table); 175 if (*table & (_SEGMENT_ENTRY_INVALID | _SEGMENT_ENTRY_LARGE)) 176 goto out; 177 table = (unsigned long *)(*table & _SEGMENT_ENTRY_ORIGIN); 178 } 179 table = table + ((address >> 12) & 0xff); 180 if (bad_address(table)) 181 goto bad; 182 pr_cont("P:%016lx ", *table); 183 out: 184 pr_cont("\n"); 185 return; 186 bad: 187 pr_cont("BAD\n"); 188 } 189 190 #else /* CONFIG_64BIT */ 191 192 static void dump_pagetable(unsigned long asce, unsigned long address) 193 { 194 unsigned long *table = __va(asce & PAGE_MASK); 195 196 pr_alert("AS:%08lx ", asce); 197 table = table + ((address >> 20) & 0x7ff); 198 if (bad_address(table)) 199 goto bad; 200 pr_cont("S:%08lx ", *table); 201 if (*table & _SEGMENT_ENTRY_INVALID) 202 goto out; 203 table = (unsigned long *)(*table & _SEGMENT_ENTRY_ORIGIN); 204 table = table + ((address >> 12) & 0xff); 205 if (bad_address(table)) 206 goto bad; 207 pr_cont("P:%08lx ", *table); 208 out: 209 pr_cont("\n"); 210 return; 211 bad: 212 pr_cont("BAD\n"); 213 } 214 215 #endif /* CONFIG_64BIT */ 216 217 static void dump_fault_info(struct pt_regs *regs) 218 { 219 unsigned long asce; 220 221 pr_alert("Fault in "); 222 switch (regs->int_parm_long & 3) { 223 case 3: 224 pr_cont("home space "); 225 break; 226 case 2: 227 pr_cont("secondary space "); 228 break; 229 case 1: 230 pr_cont("access register "); 231 break; 232 case 0: 233 pr_cont("primary space "); 234 break; 235 } 236 pr_cont("mode while using "); 237 if (!user_space_fault(regs)) { 238 asce = S390_lowcore.kernel_asce; 239 pr_cont("kernel "); 240 } 241 #ifdef CONFIG_PGSTE 242 else if ((current->flags & PF_VCPU) && S390_lowcore.gmap) { 243 struct gmap *gmap = (struct gmap *)S390_lowcore.gmap; 244 asce = gmap->asce; 245 pr_cont("gmap "); 246 } 247 #endif 248 else { 249 asce = S390_lowcore.user_asce; 250 pr_cont("user "); 251 } 252 pr_cont("ASCE.\n"); 253 dump_pagetable(asce, regs->int_parm_long & __FAIL_ADDR_MASK); 254 } 255 256 static inline void report_user_fault(struct pt_regs *regs, long signr) 257 { 258 if ((task_pid_nr(current) > 1) && !show_unhandled_signals) 259 return; 260 if (!unhandled_signal(current, signr)) 261 return; 262 if (!printk_ratelimit()) 263 return; 264 printk(KERN_ALERT "User process fault: interruption code %04x ilc:%d ", 265 regs->int_code & 0xffff, regs->int_code >> 17); 266 print_vma_addr(KERN_CONT "in ", regs->psw.addr & PSW_ADDR_INSN); 267 printk(KERN_CONT "\n"); 268 printk(KERN_ALERT "failing address: %016lx TEID: %016lx\n", 269 regs->int_parm_long & __FAIL_ADDR_MASK, regs->int_parm_long); 270 dump_fault_info(regs); 271 show_regs(regs); 272 } 273 274 /* 275 * Send SIGSEGV to task. This is an external routine 276 * to keep the stack usage of do_page_fault small. 277 */ 278 static noinline void do_sigsegv(struct pt_regs *regs, int si_code) 279 { 280 struct siginfo si; 281 282 report_user_fault(regs, SIGSEGV); 283 si.si_signo = SIGSEGV; 284 si.si_code = si_code; 285 si.si_addr = (void __user *)(regs->int_parm_long & __FAIL_ADDR_MASK); 286 force_sig_info(SIGSEGV, &si, current); 287 } 288 289 static noinline void do_no_context(struct pt_regs *regs) 290 { 291 const struct exception_table_entry *fixup; 292 unsigned long address; 293 294 /* Are we prepared to handle this kernel fault? */ 295 fixup = search_exception_tables(regs->psw.addr & PSW_ADDR_INSN); 296 if (fixup) { 297 regs->psw.addr = extable_fixup(fixup) | PSW_ADDR_AMODE; 298 return; 299 } 300 301 /* 302 * Oops. The kernel tried to access some bad page. We'll have to 303 * terminate things with extreme prejudice. 304 */ 305 address = regs->int_parm_long & __FAIL_ADDR_MASK; 306 if (!user_space_fault(regs)) 307 printk(KERN_ALERT "Unable to handle kernel pointer dereference" 308 " in virtual kernel address space\n"); 309 else 310 printk(KERN_ALERT "Unable to handle kernel paging request" 311 " in virtual user address space\n"); 312 printk(KERN_ALERT "failing address: %016lx TEID: %016lx\n", 313 regs->int_parm_long & __FAIL_ADDR_MASK, regs->int_parm_long); 314 dump_fault_info(regs); 315 die(regs, "Oops"); 316 do_exit(SIGKILL); 317 } 318 319 static noinline void do_low_address(struct pt_regs *regs) 320 { 321 /* Low-address protection hit in kernel mode means 322 NULL pointer write access in kernel mode. */ 323 if (regs->psw.mask & PSW_MASK_PSTATE) { 324 /* Low-address protection hit in user mode 'cannot happen'. */ 325 die (regs, "Low-address protection"); 326 do_exit(SIGKILL); 327 } 328 329 do_no_context(regs); 330 } 331 332 static noinline void do_sigbus(struct pt_regs *regs) 333 { 334 struct task_struct *tsk = current; 335 struct siginfo si; 336 337 /* 338 * Send a sigbus, regardless of whether we were in kernel 339 * or user mode. 340 */ 341 si.si_signo = SIGBUS; 342 si.si_errno = 0; 343 si.si_code = BUS_ADRERR; 344 si.si_addr = (void __user *)(regs->int_parm_long & __FAIL_ADDR_MASK); 345 force_sig_info(SIGBUS, &si, tsk); 346 } 347 348 static noinline void do_fault_error(struct pt_regs *regs, int fault) 349 { 350 int si_code; 351 352 switch (fault) { 353 case VM_FAULT_BADACCESS: 354 case VM_FAULT_BADMAP: 355 /* Bad memory access. Check if it is kernel or user space. */ 356 if (user_mode(regs)) { 357 /* User mode accesses just cause a SIGSEGV */ 358 si_code = (fault == VM_FAULT_BADMAP) ? 359 SEGV_MAPERR : SEGV_ACCERR; 360 do_sigsegv(regs, si_code); 361 return; 362 } 363 case VM_FAULT_BADCONTEXT: 364 case VM_FAULT_PFAULT: 365 do_no_context(regs); 366 break; 367 case VM_FAULT_SIGNAL: 368 if (!user_mode(regs)) 369 do_no_context(regs); 370 break; 371 default: /* fault & VM_FAULT_ERROR */ 372 if (fault & VM_FAULT_OOM) { 373 if (!user_mode(regs)) 374 do_no_context(regs); 375 else 376 pagefault_out_of_memory(); 377 } else if (fault & VM_FAULT_SIGSEGV) { 378 /* Kernel mode? Handle exceptions or die */ 379 if (!user_mode(regs)) 380 do_no_context(regs); 381 else 382 do_sigsegv(regs, SEGV_MAPERR); 383 } else if (fault & VM_FAULT_SIGBUS) { 384 /* Kernel mode? Handle exceptions or die */ 385 if (!user_mode(regs)) 386 do_no_context(regs); 387 else 388 do_sigbus(regs); 389 } else 390 BUG(); 391 break; 392 } 393 } 394 395 /* 396 * This routine handles page faults. It determines the address, 397 * and the problem, and then passes it off to one of the appropriate 398 * routines. 399 * 400 * interruption code (int_code): 401 * 04 Protection -> Write-Protection (suprression) 402 * 10 Segment translation -> Not present (nullification) 403 * 11 Page translation -> Not present (nullification) 404 * 3b Region third trans. -> Not present (nullification) 405 */ 406 static inline int do_exception(struct pt_regs *regs, int access) 407 { 408 #ifdef CONFIG_PGSTE 409 struct gmap *gmap; 410 #endif 411 struct task_struct *tsk; 412 struct mm_struct *mm; 413 struct vm_area_struct *vma; 414 unsigned long trans_exc_code; 415 unsigned long address; 416 unsigned int flags; 417 int fault; 418 419 tsk = current; 420 /* 421 * The instruction that caused the program check has 422 * been nullified. Don't signal single step via SIGTRAP. 423 */ 424 clear_pt_regs_flag(regs, PIF_PER_TRAP); 425 426 if (notify_page_fault(regs)) 427 return 0; 428 429 mm = tsk->mm; 430 trans_exc_code = regs->int_parm_long; 431 432 /* 433 * Verify that the fault happened in user space, that 434 * we are not in an interrupt and that there is a 435 * user context. 436 */ 437 fault = VM_FAULT_BADCONTEXT; 438 if (unlikely(!user_space_fault(regs) || in_atomic() || !mm)) 439 goto out; 440 441 address = trans_exc_code & __FAIL_ADDR_MASK; 442 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 443 flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; 444 if (user_mode(regs)) 445 flags |= FAULT_FLAG_USER; 446 if (access == VM_WRITE || (trans_exc_code & store_indication) == 0x400) 447 flags |= FAULT_FLAG_WRITE; 448 down_read(&mm->mmap_sem); 449 450 #ifdef CONFIG_PGSTE 451 gmap = (current->flags & PF_VCPU) ? 452 (struct gmap *) S390_lowcore.gmap : NULL; 453 if (gmap) { 454 current->thread.gmap_addr = address; 455 address = __gmap_translate(gmap, address); 456 if (address == -EFAULT) { 457 fault = VM_FAULT_BADMAP; 458 goto out_up; 459 } 460 if (gmap->pfault_enabled) 461 flags |= FAULT_FLAG_RETRY_NOWAIT; 462 } 463 #endif 464 465 retry: 466 fault = VM_FAULT_BADMAP; 467 vma = find_vma(mm, address); 468 if (!vma) 469 goto out_up; 470 471 if (unlikely(vma->vm_start > address)) { 472 if (!(vma->vm_flags & VM_GROWSDOWN)) 473 goto out_up; 474 if (expand_stack(vma, address)) 475 goto out_up; 476 } 477 478 /* 479 * Ok, we have a good vm_area for this memory access, so 480 * we can handle it.. 481 */ 482 fault = VM_FAULT_BADACCESS; 483 if (unlikely(!(vma->vm_flags & access))) 484 goto out_up; 485 486 if (is_vm_hugetlb_page(vma)) 487 address &= HPAGE_MASK; 488 /* 489 * If for any reason at all we couldn't handle the fault, 490 * make sure we exit gracefully rather than endlessly redo 491 * the fault. 492 */ 493 fault = handle_mm_fault(mm, vma, address, flags); 494 /* No reason to continue if interrupted by SIGKILL. */ 495 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) { 496 fault = VM_FAULT_SIGNAL; 497 goto out; 498 } 499 if (unlikely(fault & VM_FAULT_ERROR)) 500 goto out_up; 501 502 /* 503 * Major/minor page fault accounting is only done on the 504 * initial attempt. If we go through a retry, it is extremely 505 * likely that the page will be found in page cache at that point. 506 */ 507 if (flags & FAULT_FLAG_ALLOW_RETRY) { 508 if (fault & VM_FAULT_MAJOR) { 509 tsk->maj_flt++; 510 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, 511 regs, address); 512 } else { 513 tsk->min_flt++; 514 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, 515 regs, address); 516 } 517 if (fault & VM_FAULT_RETRY) { 518 #ifdef CONFIG_PGSTE 519 if (gmap && (flags & FAULT_FLAG_RETRY_NOWAIT)) { 520 /* FAULT_FLAG_RETRY_NOWAIT has been set, 521 * mmap_sem has not been released */ 522 current->thread.gmap_pfault = 1; 523 fault = VM_FAULT_PFAULT; 524 goto out_up; 525 } 526 #endif 527 /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk 528 * of starvation. */ 529 flags &= ~(FAULT_FLAG_ALLOW_RETRY | 530 FAULT_FLAG_RETRY_NOWAIT); 531 flags |= FAULT_FLAG_TRIED; 532 down_read(&mm->mmap_sem); 533 goto retry; 534 } 535 } 536 #ifdef CONFIG_PGSTE 537 if (gmap) { 538 address = __gmap_link(gmap, current->thread.gmap_addr, 539 address); 540 if (address == -EFAULT) { 541 fault = VM_FAULT_BADMAP; 542 goto out_up; 543 } 544 if (address == -ENOMEM) { 545 fault = VM_FAULT_OOM; 546 goto out_up; 547 } 548 } 549 #endif 550 fault = 0; 551 out_up: 552 up_read(&mm->mmap_sem); 553 out: 554 return fault; 555 } 556 557 void do_protection_exception(struct pt_regs *regs) 558 { 559 unsigned long trans_exc_code; 560 int fault; 561 562 trans_exc_code = regs->int_parm_long; 563 /* 564 * Protection exceptions are suppressing, decrement psw address. 565 * The exception to this rule are aborted transactions, for these 566 * the PSW already points to the correct location. 567 */ 568 if (!(regs->int_code & 0x200)) 569 regs->psw.addr = __rewind_psw(regs->psw, regs->int_code >> 16); 570 /* 571 * Check for low-address protection. This needs to be treated 572 * as a special case because the translation exception code 573 * field is not guaranteed to contain valid data in this case. 574 */ 575 if (unlikely(!(trans_exc_code & 4))) { 576 do_low_address(regs); 577 return; 578 } 579 fault = do_exception(regs, VM_WRITE); 580 if (unlikely(fault)) 581 do_fault_error(regs, fault); 582 } 583 NOKPROBE_SYMBOL(do_protection_exception); 584 585 void do_dat_exception(struct pt_regs *regs) 586 { 587 int access, fault; 588 589 access = VM_READ | VM_EXEC | VM_WRITE; 590 fault = do_exception(regs, access); 591 if (unlikely(fault)) 592 do_fault_error(regs, fault); 593 } 594 NOKPROBE_SYMBOL(do_dat_exception); 595 596 #ifdef CONFIG_PFAULT 597 /* 598 * 'pfault' pseudo page faults routines. 599 */ 600 static int pfault_disable; 601 602 static int __init nopfault(char *str) 603 { 604 pfault_disable = 1; 605 return 1; 606 } 607 608 __setup("nopfault", nopfault); 609 610 struct pfault_refbk { 611 u16 refdiagc; 612 u16 reffcode; 613 u16 refdwlen; 614 u16 refversn; 615 u64 refgaddr; 616 u64 refselmk; 617 u64 refcmpmk; 618 u64 reserved; 619 } __attribute__ ((packed, aligned(8))); 620 621 int pfault_init(void) 622 { 623 struct pfault_refbk refbk = { 624 .refdiagc = 0x258, 625 .reffcode = 0, 626 .refdwlen = 5, 627 .refversn = 2, 628 .refgaddr = __LC_CURRENT_PID, 629 .refselmk = 1ULL << 48, 630 .refcmpmk = 1ULL << 48, 631 .reserved = __PF_RES_FIELD }; 632 int rc; 633 634 if (pfault_disable) 635 return -1; 636 asm volatile( 637 " diag %1,%0,0x258\n" 638 "0: j 2f\n" 639 "1: la %0,8\n" 640 "2:\n" 641 EX_TABLE(0b,1b) 642 : "=d" (rc) : "a" (&refbk), "m" (refbk) : "cc"); 643 return rc; 644 } 645 646 void pfault_fini(void) 647 { 648 struct pfault_refbk refbk = { 649 .refdiagc = 0x258, 650 .reffcode = 1, 651 .refdwlen = 5, 652 .refversn = 2, 653 }; 654 655 if (pfault_disable) 656 return; 657 asm volatile( 658 " diag %0,0,0x258\n" 659 "0:\n" 660 EX_TABLE(0b,0b) 661 : : "a" (&refbk), "m" (refbk) : "cc"); 662 } 663 664 static DEFINE_SPINLOCK(pfault_lock); 665 static LIST_HEAD(pfault_list); 666 667 static void pfault_interrupt(struct ext_code ext_code, 668 unsigned int param32, unsigned long param64) 669 { 670 struct task_struct *tsk; 671 __u16 subcode; 672 pid_t pid; 673 674 /* 675 * Get the external interruption subcode & pfault 676 * initial/completion signal bit. VM stores this 677 * in the 'cpu address' field associated with the 678 * external interrupt. 679 */ 680 subcode = ext_code.subcode; 681 if ((subcode & 0xff00) != __SUBCODE_MASK) 682 return; 683 inc_irq_stat(IRQEXT_PFL); 684 /* Get the token (= pid of the affected task). */ 685 pid = sizeof(void *) == 4 ? param32 : param64; 686 rcu_read_lock(); 687 tsk = find_task_by_pid_ns(pid, &init_pid_ns); 688 if (tsk) 689 get_task_struct(tsk); 690 rcu_read_unlock(); 691 if (!tsk) 692 return; 693 spin_lock(&pfault_lock); 694 if (subcode & 0x0080) { 695 /* signal bit is set -> a page has been swapped in by VM */ 696 if (tsk->thread.pfault_wait == 1) { 697 /* Initial interrupt was faster than the completion 698 * interrupt. pfault_wait is valid. Set pfault_wait 699 * back to zero and wake up the process. This can 700 * safely be done because the task is still sleeping 701 * and can't produce new pfaults. */ 702 tsk->thread.pfault_wait = 0; 703 list_del(&tsk->thread.list); 704 wake_up_process(tsk); 705 put_task_struct(tsk); 706 } else { 707 /* Completion interrupt was faster than initial 708 * interrupt. Set pfault_wait to -1 so the initial 709 * interrupt doesn't put the task to sleep. 710 * If the task is not running, ignore the completion 711 * interrupt since it must be a leftover of a PFAULT 712 * CANCEL operation which didn't remove all pending 713 * completion interrupts. */ 714 if (tsk->state == TASK_RUNNING) 715 tsk->thread.pfault_wait = -1; 716 } 717 } else { 718 /* signal bit not set -> a real page is missing. */ 719 if (WARN_ON_ONCE(tsk != current)) 720 goto out; 721 if (tsk->thread.pfault_wait == 1) { 722 /* Already on the list with a reference: put to sleep */ 723 __set_task_state(tsk, TASK_UNINTERRUPTIBLE); 724 set_tsk_need_resched(tsk); 725 } else if (tsk->thread.pfault_wait == -1) { 726 /* Completion interrupt was faster than the initial 727 * interrupt (pfault_wait == -1). Set pfault_wait 728 * back to zero and exit. */ 729 tsk->thread.pfault_wait = 0; 730 } else { 731 /* Initial interrupt arrived before completion 732 * interrupt. Let the task sleep. 733 * An extra task reference is needed since a different 734 * cpu may set the task state to TASK_RUNNING again 735 * before the scheduler is reached. */ 736 get_task_struct(tsk); 737 tsk->thread.pfault_wait = 1; 738 list_add(&tsk->thread.list, &pfault_list); 739 __set_task_state(tsk, TASK_UNINTERRUPTIBLE); 740 set_tsk_need_resched(tsk); 741 } 742 } 743 out: 744 spin_unlock(&pfault_lock); 745 put_task_struct(tsk); 746 } 747 748 static int pfault_cpu_notify(struct notifier_block *self, unsigned long action, 749 void *hcpu) 750 { 751 struct thread_struct *thread, *next; 752 struct task_struct *tsk; 753 754 switch (action & ~CPU_TASKS_FROZEN) { 755 case CPU_DEAD: 756 spin_lock_irq(&pfault_lock); 757 list_for_each_entry_safe(thread, next, &pfault_list, list) { 758 thread->pfault_wait = 0; 759 list_del(&thread->list); 760 tsk = container_of(thread, struct task_struct, thread); 761 wake_up_process(tsk); 762 put_task_struct(tsk); 763 } 764 spin_unlock_irq(&pfault_lock); 765 break; 766 default: 767 break; 768 } 769 return NOTIFY_OK; 770 } 771 772 static int __init pfault_irq_init(void) 773 { 774 int rc; 775 776 rc = register_external_irq(EXT_IRQ_CP_SERVICE, pfault_interrupt); 777 if (rc) 778 goto out_extint; 779 rc = pfault_init() == 0 ? 0 : -EOPNOTSUPP; 780 if (rc) 781 goto out_pfault; 782 irq_subclass_register(IRQ_SUBCLASS_SERVICE_SIGNAL); 783 hotcpu_notifier(pfault_cpu_notify, 0); 784 return 0; 785 786 out_pfault: 787 unregister_external_irq(EXT_IRQ_CP_SERVICE, pfault_interrupt); 788 out_extint: 789 pfault_disable = 1; 790 return rc; 791 } 792 early_initcall(pfault_irq_init); 793 794 #endif /* CONFIG_PFAULT */ 795