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/sched/debug.h> 16 #include <linux/kernel.h> 17 #include <linux/errno.h> 18 #include <linux/string.h> 19 #include <linux/types.h> 20 #include <linux/ptrace.h> 21 #include <linux/mman.h> 22 #include <linux/mm.h> 23 #include <linux/compat.h> 24 #include <linux/smp.h> 25 #include <linux/kdebug.h> 26 #include <linux/init.h> 27 #include <linux/console.h> 28 #include <linux/extable.h> 29 #include <linux/hardirq.h> 30 #include <linux/kprobes.h> 31 #include <linux/uaccess.h> 32 #include <linux/hugetlb.h> 33 #include <asm/asm-offsets.h> 34 #include <asm/diag.h> 35 #include <asm/pgtable.h> 36 #include <asm/gmap.h> 37 #include <asm/irq.h> 38 #include <asm/mmu_context.h> 39 #include <asm/facility.h> 40 #include "../kernel/entry.h" 41 42 #define __FAIL_ADDR_MASK -4096L 43 #define __SUBCODE_MASK 0x0600 44 #define __PF_RES_FIELD 0x8000000000000000ULL 45 46 #define VM_FAULT_BADCONTEXT 0x010000 47 #define VM_FAULT_BADMAP 0x020000 48 #define VM_FAULT_BADACCESS 0x040000 49 #define VM_FAULT_SIGNAL 0x080000 50 #define VM_FAULT_PFAULT 0x100000 51 52 static unsigned long store_indication __read_mostly; 53 54 static int __init fault_init(void) 55 { 56 if (test_facility(75)) 57 store_indication = 0xc00; 58 return 0; 59 } 60 early_initcall(fault_init); 61 62 static inline int notify_page_fault(struct pt_regs *regs) 63 { 64 int ret = 0; 65 66 /* kprobe_running() needs smp_processor_id() */ 67 if (kprobes_built_in() && !user_mode(regs)) { 68 preempt_disable(); 69 if (kprobe_running() && kprobe_fault_handler(regs, 14)) 70 ret = 1; 71 preempt_enable(); 72 } 73 return ret; 74 } 75 76 77 /* 78 * Unlock any spinlocks which will prevent us from getting the 79 * message out. 80 */ 81 void bust_spinlocks(int yes) 82 { 83 if (yes) { 84 oops_in_progress = 1; 85 } else { 86 int loglevel_save = console_loglevel; 87 console_unblank(); 88 oops_in_progress = 0; 89 /* 90 * OK, the message is on the console. Now we call printk() 91 * without oops_in_progress set so that printk will give klogd 92 * a poke. Hold onto your hats... 93 */ 94 console_loglevel = 15; 95 printk(" "); 96 console_loglevel = loglevel_save; 97 } 98 } 99 100 /* 101 * Returns the address space associated with the fault. 102 * Returns 0 for kernel space and 1 for user space. 103 */ 104 static inline int user_space_fault(struct pt_regs *regs) 105 { 106 unsigned long trans_exc_code; 107 108 /* 109 * The lowest two bits of the translation exception 110 * identification indicate which paging table was used. 111 */ 112 trans_exc_code = regs->int_parm_long & 3; 113 if (trans_exc_code == 3) /* home space -> kernel */ 114 return 0; 115 if (user_mode(regs)) 116 return 1; 117 if (trans_exc_code == 2) /* secondary space -> set_fs */ 118 return current->thread.mm_segment.ar4; 119 if (current->flags & PF_VCPU) 120 return 1; 121 return 0; 122 } 123 124 static int bad_address(void *p) 125 { 126 unsigned long dummy; 127 128 return probe_kernel_address((unsigned long *)p, dummy); 129 } 130 131 static void dump_pagetable(unsigned long asce, unsigned long address) 132 { 133 unsigned long *table = __va(asce & PAGE_MASK); 134 135 pr_alert("AS:%016lx ", asce); 136 switch (asce & _ASCE_TYPE_MASK) { 137 case _ASCE_TYPE_REGION1: 138 table = table + ((address >> 53) & 0x7ff); 139 if (bad_address(table)) 140 goto bad; 141 pr_cont("R1:%016lx ", *table); 142 if (*table & _REGION_ENTRY_INVALID) 143 goto out; 144 table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN); 145 /* fallthrough */ 146 case _ASCE_TYPE_REGION2: 147 table = table + ((address >> 42) & 0x7ff); 148 if (bad_address(table)) 149 goto bad; 150 pr_cont("R2:%016lx ", *table); 151 if (*table & _REGION_ENTRY_INVALID) 152 goto out; 153 table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN); 154 /* fallthrough */ 155 case _ASCE_TYPE_REGION3: 156 table = table + ((address >> 31) & 0x7ff); 157 if (bad_address(table)) 158 goto bad; 159 pr_cont("R3:%016lx ", *table); 160 if (*table & (_REGION_ENTRY_INVALID | _REGION3_ENTRY_LARGE)) 161 goto out; 162 table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN); 163 /* fallthrough */ 164 case _ASCE_TYPE_SEGMENT: 165 table = table + ((address >> 20) & 0x7ff); 166 if (bad_address(table)) 167 goto bad; 168 pr_cont("S:%016lx ", *table); 169 if (*table & (_SEGMENT_ENTRY_INVALID | _SEGMENT_ENTRY_LARGE)) 170 goto out; 171 table = (unsigned long *)(*table & _SEGMENT_ENTRY_ORIGIN); 172 } 173 table = table + ((address >> 12) & 0xff); 174 if (bad_address(table)) 175 goto bad; 176 pr_cont("P:%016lx ", *table); 177 out: 178 pr_cont("\n"); 179 return; 180 bad: 181 pr_cont("BAD\n"); 182 } 183 184 static void dump_fault_info(struct pt_regs *regs) 185 { 186 unsigned long asce; 187 188 pr_alert("Failing address: %016lx TEID: %016lx\n", 189 regs->int_parm_long & __FAIL_ADDR_MASK, regs->int_parm_long); 190 pr_alert("Fault in "); 191 switch (regs->int_parm_long & 3) { 192 case 3: 193 pr_cont("home space "); 194 break; 195 case 2: 196 pr_cont("secondary space "); 197 break; 198 case 1: 199 pr_cont("access register "); 200 break; 201 case 0: 202 pr_cont("primary space "); 203 break; 204 } 205 pr_cont("mode while using "); 206 if (!user_space_fault(regs)) { 207 asce = S390_lowcore.kernel_asce; 208 pr_cont("kernel "); 209 } 210 #ifdef CONFIG_PGSTE 211 else if ((current->flags & PF_VCPU) && S390_lowcore.gmap) { 212 struct gmap *gmap = (struct gmap *)S390_lowcore.gmap; 213 asce = gmap->asce; 214 pr_cont("gmap "); 215 } 216 #endif 217 else { 218 asce = S390_lowcore.user_asce; 219 pr_cont("user "); 220 } 221 pr_cont("ASCE.\n"); 222 dump_pagetable(asce, regs->int_parm_long & __FAIL_ADDR_MASK); 223 } 224 225 int show_unhandled_signals = 1; 226 227 void report_user_fault(struct pt_regs *regs, long signr, int is_mm_fault) 228 { 229 if ((task_pid_nr(current) > 1) && !show_unhandled_signals) 230 return; 231 if (!unhandled_signal(current, signr)) 232 return; 233 if (!printk_ratelimit()) 234 return; 235 printk(KERN_ALERT "User process fault: interruption code %04x ilc:%d ", 236 regs->int_code & 0xffff, regs->int_code >> 17); 237 print_vma_addr(KERN_CONT "in ", regs->psw.addr); 238 printk(KERN_CONT "\n"); 239 if (is_mm_fault) 240 dump_fault_info(regs); 241 show_regs(regs); 242 } 243 244 /* 245 * Send SIGSEGV to task. This is an external routine 246 * to keep the stack usage of do_page_fault small. 247 */ 248 static noinline void do_sigsegv(struct pt_regs *regs, int si_code) 249 { 250 struct siginfo si; 251 252 report_user_fault(regs, SIGSEGV, 1); 253 si.si_signo = SIGSEGV; 254 si.si_errno = 0; 255 si.si_code = si_code; 256 si.si_addr = (void __user *)(regs->int_parm_long & __FAIL_ADDR_MASK); 257 force_sig_info(SIGSEGV, &si, current); 258 } 259 260 static noinline void do_no_context(struct pt_regs *regs) 261 { 262 const struct exception_table_entry *fixup; 263 264 /* Are we prepared to handle this kernel fault? */ 265 fixup = search_exception_tables(regs->psw.addr); 266 if (fixup) { 267 regs->psw.addr = extable_fixup(fixup); 268 return; 269 } 270 271 /* 272 * Oops. The kernel tried to access some bad page. We'll have to 273 * terminate things with extreme prejudice. 274 */ 275 if (!user_space_fault(regs)) 276 printk(KERN_ALERT "Unable to handle kernel pointer dereference" 277 " in virtual kernel address space\n"); 278 else 279 printk(KERN_ALERT "Unable to handle kernel paging request" 280 " in virtual user address space\n"); 281 dump_fault_info(regs); 282 die(regs, "Oops"); 283 do_exit(SIGKILL); 284 } 285 286 static noinline void do_low_address(struct pt_regs *regs) 287 { 288 /* Low-address protection hit in kernel mode means 289 NULL pointer write access in kernel mode. */ 290 if (regs->psw.mask & PSW_MASK_PSTATE) { 291 /* Low-address protection hit in user mode 'cannot happen'. */ 292 die (regs, "Low-address protection"); 293 do_exit(SIGKILL); 294 } 295 296 do_no_context(regs); 297 } 298 299 static noinline void do_sigbus(struct pt_regs *regs) 300 { 301 struct task_struct *tsk = current; 302 struct siginfo si; 303 304 /* 305 * Send a sigbus, regardless of whether we were in kernel 306 * or user mode. 307 */ 308 si.si_signo = SIGBUS; 309 si.si_errno = 0; 310 si.si_code = BUS_ADRERR; 311 si.si_addr = (void __user *)(regs->int_parm_long & __FAIL_ADDR_MASK); 312 force_sig_info(SIGBUS, &si, tsk); 313 } 314 315 static noinline int signal_return(struct pt_regs *regs) 316 { 317 u16 instruction; 318 int rc; 319 320 rc = __get_user(instruction, (u16 __user *) regs->psw.addr); 321 if (rc) 322 return rc; 323 if (instruction == 0x0a77) { 324 set_pt_regs_flag(regs, PIF_SYSCALL); 325 regs->int_code = 0x00040077; 326 return 0; 327 } else if (instruction == 0x0aad) { 328 set_pt_regs_flag(regs, PIF_SYSCALL); 329 regs->int_code = 0x000400ad; 330 return 0; 331 } 332 return -EACCES; 333 } 334 335 static noinline void do_fault_error(struct pt_regs *regs, int access, int fault) 336 { 337 int si_code; 338 339 switch (fault) { 340 case VM_FAULT_BADACCESS: 341 if (access == VM_EXEC && signal_return(regs) == 0) 342 break; 343 case VM_FAULT_BADMAP: 344 /* Bad memory access. Check if it is kernel or user space. */ 345 if (user_mode(regs)) { 346 /* User mode accesses just cause a SIGSEGV */ 347 si_code = (fault == VM_FAULT_BADMAP) ? 348 SEGV_MAPERR : SEGV_ACCERR; 349 do_sigsegv(regs, si_code); 350 break; 351 } 352 case VM_FAULT_BADCONTEXT: 353 case VM_FAULT_PFAULT: 354 do_no_context(regs); 355 break; 356 case VM_FAULT_SIGNAL: 357 if (!user_mode(regs)) 358 do_no_context(regs); 359 break; 360 default: /* fault & VM_FAULT_ERROR */ 361 if (fault & VM_FAULT_OOM) { 362 if (!user_mode(regs)) 363 do_no_context(regs); 364 else 365 pagefault_out_of_memory(); 366 } else if (fault & VM_FAULT_SIGSEGV) { 367 /* Kernel mode? Handle exceptions or die */ 368 if (!user_mode(regs)) 369 do_no_context(regs); 370 else 371 do_sigsegv(regs, SEGV_MAPERR); 372 } else if (fault & VM_FAULT_SIGBUS) { 373 /* Kernel mode? Handle exceptions or die */ 374 if (!user_mode(regs)) 375 do_no_context(regs); 376 else 377 do_sigbus(regs); 378 } else 379 BUG(); 380 break; 381 } 382 } 383 384 /* 385 * This routine handles page faults. It determines the address, 386 * and the problem, and then passes it off to one of the appropriate 387 * routines. 388 * 389 * interruption code (int_code): 390 * 04 Protection -> Write-Protection (suprression) 391 * 10 Segment translation -> Not present (nullification) 392 * 11 Page translation -> Not present (nullification) 393 * 3b Region third trans. -> Not present (nullification) 394 */ 395 static inline int do_exception(struct pt_regs *regs, int access) 396 { 397 #ifdef CONFIG_PGSTE 398 struct gmap *gmap; 399 #endif 400 struct task_struct *tsk; 401 struct mm_struct *mm; 402 struct vm_area_struct *vma; 403 unsigned long trans_exc_code; 404 unsigned long address; 405 unsigned int flags; 406 int fault; 407 408 tsk = current; 409 /* 410 * The instruction that caused the program check has 411 * been nullified. Don't signal single step via SIGTRAP. 412 */ 413 clear_pt_regs_flag(regs, PIF_PER_TRAP); 414 415 if (notify_page_fault(regs)) 416 return 0; 417 418 mm = tsk->mm; 419 trans_exc_code = regs->int_parm_long; 420 421 /* 422 * Verify that the fault happened in user space, that 423 * we are not in an interrupt and that there is a 424 * user context. 425 */ 426 fault = VM_FAULT_BADCONTEXT; 427 if (unlikely(!user_space_fault(regs) || faulthandler_disabled() || !mm)) 428 goto out; 429 430 address = trans_exc_code & __FAIL_ADDR_MASK; 431 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 432 flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; 433 if (user_mode(regs)) 434 flags |= FAULT_FLAG_USER; 435 if (access == VM_WRITE || (trans_exc_code & store_indication) == 0x400) 436 flags |= FAULT_FLAG_WRITE; 437 down_read(&mm->mmap_sem); 438 439 #ifdef CONFIG_PGSTE 440 gmap = (current->flags & PF_VCPU) ? 441 (struct gmap *) S390_lowcore.gmap : NULL; 442 if (gmap) { 443 current->thread.gmap_addr = address; 444 current->thread.gmap_write_flag = !!(flags & FAULT_FLAG_WRITE); 445 current->thread.gmap_int_code = regs->int_code & 0xffff; 446 address = __gmap_translate(gmap, address); 447 if (address == -EFAULT) { 448 fault = VM_FAULT_BADMAP; 449 goto out_up; 450 } 451 if (gmap->pfault_enabled) 452 flags |= FAULT_FLAG_RETRY_NOWAIT; 453 } 454 #endif 455 456 retry: 457 fault = VM_FAULT_BADMAP; 458 vma = find_vma(mm, address); 459 if (!vma) 460 goto out_up; 461 462 if (unlikely(vma->vm_start > address)) { 463 if (!(vma->vm_flags & VM_GROWSDOWN)) 464 goto out_up; 465 if (expand_stack(vma, address)) 466 goto out_up; 467 } 468 469 /* 470 * Ok, we have a good vm_area for this memory access, so 471 * we can handle it.. 472 */ 473 fault = VM_FAULT_BADACCESS; 474 if (unlikely(!(vma->vm_flags & access))) 475 goto out_up; 476 477 if (is_vm_hugetlb_page(vma)) 478 address &= HPAGE_MASK; 479 /* 480 * If for any reason at all we couldn't handle the fault, 481 * make sure we exit gracefully rather than endlessly redo 482 * the fault. 483 */ 484 fault = handle_mm_fault(vma, address, flags); 485 /* No reason to continue if interrupted by SIGKILL. */ 486 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) { 487 fault = VM_FAULT_SIGNAL; 488 goto out; 489 } 490 if (unlikely(fault & VM_FAULT_ERROR)) 491 goto out_up; 492 493 /* 494 * Major/minor page fault accounting is only done on the 495 * initial attempt. If we go through a retry, it is extremely 496 * likely that the page will be found in page cache at that point. 497 */ 498 if (flags & FAULT_FLAG_ALLOW_RETRY) { 499 if (fault & VM_FAULT_MAJOR) { 500 tsk->maj_flt++; 501 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, 502 regs, address); 503 } else { 504 tsk->min_flt++; 505 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, 506 regs, address); 507 } 508 if (fault & VM_FAULT_RETRY) { 509 #ifdef CONFIG_PGSTE 510 if (gmap && (flags & FAULT_FLAG_RETRY_NOWAIT)) { 511 /* FAULT_FLAG_RETRY_NOWAIT has been set, 512 * mmap_sem has not been released */ 513 current->thread.gmap_pfault = 1; 514 fault = VM_FAULT_PFAULT; 515 goto out_up; 516 } 517 #endif 518 /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk 519 * of starvation. */ 520 flags &= ~(FAULT_FLAG_ALLOW_RETRY | 521 FAULT_FLAG_RETRY_NOWAIT); 522 flags |= FAULT_FLAG_TRIED; 523 down_read(&mm->mmap_sem); 524 goto retry; 525 } 526 } 527 #ifdef CONFIG_PGSTE 528 if (gmap) { 529 address = __gmap_link(gmap, current->thread.gmap_addr, 530 address); 531 if (address == -EFAULT) { 532 fault = VM_FAULT_BADMAP; 533 goto out_up; 534 } 535 if (address == -ENOMEM) { 536 fault = VM_FAULT_OOM; 537 goto out_up; 538 } 539 } 540 #endif 541 fault = 0; 542 out_up: 543 up_read(&mm->mmap_sem); 544 out: 545 return fault; 546 } 547 548 void do_protection_exception(struct pt_regs *regs) 549 { 550 unsigned long trans_exc_code; 551 int access, fault; 552 553 trans_exc_code = regs->int_parm_long; 554 /* 555 * Protection exceptions are suppressing, decrement psw address. 556 * The exception to this rule are aborted transactions, for these 557 * the PSW already points to the correct location. 558 */ 559 if (!(regs->int_code & 0x200)) 560 regs->psw.addr = __rewind_psw(regs->psw, regs->int_code >> 16); 561 /* 562 * Check for low-address protection. This needs to be treated 563 * as a special case because the translation exception code 564 * field is not guaranteed to contain valid data in this case. 565 */ 566 if (unlikely(!(trans_exc_code & 4))) { 567 do_low_address(regs); 568 return; 569 } 570 if (unlikely(MACHINE_HAS_NX && (trans_exc_code & 0x80))) { 571 regs->int_parm_long = (trans_exc_code & ~PAGE_MASK) | 572 (regs->psw.addr & PAGE_MASK); 573 access = VM_EXEC; 574 fault = VM_FAULT_BADACCESS; 575 } else { 576 access = VM_WRITE; 577 fault = do_exception(regs, access); 578 } 579 if (unlikely(fault)) 580 do_fault_error(regs, access, fault); 581 } 582 NOKPROBE_SYMBOL(do_protection_exception); 583 584 void do_dat_exception(struct pt_regs *regs) 585 { 586 int access, fault; 587 588 access = VM_READ | VM_EXEC | VM_WRITE; 589 fault = do_exception(regs, access); 590 if (unlikely(fault)) 591 do_fault_error(regs, access, fault); 592 } 593 NOKPROBE_SYMBOL(do_dat_exception); 594 595 #ifdef CONFIG_PFAULT 596 /* 597 * 'pfault' pseudo page faults routines. 598 */ 599 static int pfault_disable; 600 601 static int __init nopfault(char *str) 602 { 603 pfault_disable = 1; 604 return 1; 605 } 606 607 __setup("nopfault", nopfault); 608 609 struct pfault_refbk { 610 u16 refdiagc; 611 u16 reffcode; 612 u16 refdwlen; 613 u16 refversn; 614 u64 refgaddr; 615 u64 refselmk; 616 u64 refcmpmk; 617 u64 reserved; 618 } __attribute__ ((packed, aligned(8))); 619 620 int pfault_init(void) 621 { 622 struct pfault_refbk refbk = { 623 .refdiagc = 0x258, 624 .reffcode = 0, 625 .refdwlen = 5, 626 .refversn = 2, 627 .refgaddr = __LC_LPP, 628 .refselmk = 1ULL << 48, 629 .refcmpmk = 1ULL << 48, 630 .reserved = __PF_RES_FIELD }; 631 int rc; 632 633 if (pfault_disable) 634 return -1; 635 diag_stat_inc(DIAG_STAT_X258); 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 diag_stat_inc(DIAG_STAT_X258); 658 asm volatile( 659 " diag %0,0,0x258\n" 660 "0: nopr %%r7\n" 661 EX_TABLE(0b,0b) 662 : : "a" (&refbk), "m" (refbk) : "cc"); 663 } 664 665 static DEFINE_SPINLOCK(pfault_lock); 666 static LIST_HEAD(pfault_list); 667 668 #define PF_COMPLETE 0x0080 669 670 /* 671 * The mechanism of our pfault code: if Linux is running as guest, runs a user 672 * space process and the user space process accesses a page that the host has 673 * paged out we get a pfault interrupt. 674 * 675 * This allows us, within the guest, to schedule a different process. Without 676 * this mechanism the host would have to suspend the whole virtual cpu until 677 * the page has been paged in. 678 * 679 * So when we get such an interrupt then we set the state of the current task 680 * to uninterruptible and also set the need_resched flag. Both happens within 681 * interrupt context(!). If we later on want to return to user space we 682 * recognize the need_resched flag and then call schedule(). It's not very 683 * obvious how this works... 684 * 685 * Of course we have a lot of additional fun with the completion interrupt (-> 686 * host signals that a page of a process has been paged in and the process can 687 * continue to run). This interrupt can arrive on any cpu and, since we have 688 * virtual cpus, actually appear before the interrupt that signals that a page 689 * is missing. 690 */ 691 static void pfault_interrupt(struct ext_code ext_code, 692 unsigned int param32, unsigned long param64) 693 { 694 struct task_struct *tsk; 695 __u16 subcode; 696 pid_t pid; 697 698 /* 699 * Get the external interruption subcode & pfault initial/completion 700 * signal bit. VM stores this in the 'cpu address' field associated 701 * with the external interrupt. 702 */ 703 subcode = ext_code.subcode; 704 if ((subcode & 0xff00) != __SUBCODE_MASK) 705 return; 706 inc_irq_stat(IRQEXT_PFL); 707 /* Get the token (= pid of the affected task). */ 708 pid = param64 & LPP_PFAULT_PID_MASK; 709 rcu_read_lock(); 710 tsk = find_task_by_pid_ns(pid, &init_pid_ns); 711 if (tsk) 712 get_task_struct(tsk); 713 rcu_read_unlock(); 714 if (!tsk) 715 return; 716 spin_lock(&pfault_lock); 717 if (subcode & PF_COMPLETE) { 718 /* signal bit is set -> a page has been swapped in by VM */ 719 if (tsk->thread.pfault_wait == 1) { 720 /* Initial interrupt was faster than the completion 721 * interrupt. pfault_wait is valid. Set pfault_wait 722 * back to zero and wake up the process. This can 723 * safely be done because the task is still sleeping 724 * and can't produce new pfaults. */ 725 tsk->thread.pfault_wait = 0; 726 list_del(&tsk->thread.list); 727 wake_up_process(tsk); 728 put_task_struct(tsk); 729 } else { 730 /* Completion interrupt was faster than initial 731 * interrupt. Set pfault_wait to -1 so the initial 732 * interrupt doesn't put the task to sleep. 733 * If the task is not running, ignore the completion 734 * interrupt since it must be a leftover of a PFAULT 735 * CANCEL operation which didn't remove all pending 736 * completion interrupts. */ 737 if (tsk->state == TASK_RUNNING) 738 tsk->thread.pfault_wait = -1; 739 } 740 } else { 741 /* signal bit not set -> a real page is missing. */ 742 if (WARN_ON_ONCE(tsk != current)) 743 goto out; 744 if (tsk->thread.pfault_wait == 1) { 745 /* Already on the list with a reference: put to sleep */ 746 goto block; 747 } else if (tsk->thread.pfault_wait == -1) { 748 /* Completion interrupt was faster than the initial 749 * interrupt (pfault_wait == -1). Set pfault_wait 750 * back to zero and exit. */ 751 tsk->thread.pfault_wait = 0; 752 } else { 753 /* Initial interrupt arrived before completion 754 * interrupt. Let the task sleep. 755 * An extra task reference is needed since a different 756 * cpu may set the task state to TASK_RUNNING again 757 * before the scheduler is reached. */ 758 get_task_struct(tsk); 759 tsk->thread.pfault_wait = 1; 760 list_add(&tsk->thread.list, &pfault_list); 761 block: 762 /* Since this must be a userspace fault, there 763 * is no kernel task state to trample. Rely on the 764 * return to userspace schedule() to block. */ 765 __set_current_state(TASK_UNINTERRUPTIBLE); 766 set_tsk_need_resched(tsk); 767 set_preempt_need_resched(); 768 } 769 } 770 out: 771 spin_unlock(&pfault_lock); 772 put_task_struct(tsk); 773 } 774 775 static int pfault_cpu_dead(unsigned int cpu) 776 { 777 struct thread_struct *thread, *next; 778 struct task_struct *tsk; 779 780 spin_lock_irq(&pfault_lock); 781 list_for_each_entry_safe(thread, next, &pfault_list, list) { 782 thread->pfault_wait = 0; 783 list_del(&thread->list); 784 tsk = container_of(thread, struct task_struct, thread); 785 wake_up_process(tsk); 786 put_task_struct(tsk); 787 } 788 spin_unlock_irq(&pfault_lock); 789 return 0; 790 } 791 792 static int __init pfault_irq_init(void) 793 { 794 int rc; 795 796 rc = register_external_irq(EXT_IRQ_CP_SERVICE, pfault_interrupt); 797 if (rc) 798 goto out_extint; 799 rc = pfault_init() == 0 ? 0 : -EOPNOTSUPP; 800 if (rc) 801 goto out_pfault; 802 irq_subclass_register(IRQ_SUBCLASS_SERVICE_SIGNAL); 803 cpuhp_setup_state_nocalls(CPUHP_S390_PFAULT_DEAD, "s390/pfault:dead", 804 NULL, pfault_cpu_dead); 805 return 0; 806 807 out_pfault: 808 unregister_external_irq(EXT_IRQ_CP_SERVICE, pfault_interrupt); 809 out_extint: 810 pfault_disable = 1; 811 return rc; 812 } 813 early_initcall(pfault_irq_init); 814 815 #endif /* CONFIG_PFAULT */ 816