1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * S390 version 4 * Copyright IBM Corp. 1999 5 * Author(s): Hartmut Penner (hp@de.ibm.com) 6 * Ulrich Weigand (uweigand@de.ibm.com) 7 * 8 * Derived from "arch/i386/mm/fault.c" 9 * Copyright (C) 1995 Linus Torvalds 10 */ 11 12 #include <linux/kernel_stat.h> 13 #include <linux/perf_event.h> 14 #include <linux/signal.h> 15 #include <linux/sched.h> 16 #include <linux/sched/debug.h> 17 #include <linux/kernel.h> 18 #include <linux/errno.h> 19 #include <linux/string.h> 20 #include <linux/types.h> 21 #include <linux/ptrace.h> 22 #include <linux/mman.h> 23 #include <linux/mm.h> 24 #include <linux/compat.h> 25 #include <linux/smp.h> 26 #include <linux/kdebug.h> 27 #include <linux/init.h> 28 #include <linux/console.h> 29 #include <linux/extable.h> 30 #include <linux/hardirq.h> 31 #include <linux/kprobes.h> 32 #include <linux/uaccess.h> 33 #include <linux/hugetlb.h> 34 #include <asm/asm-offsets.h> 35 #include <asm/diag.h> 36 #include <asm/pgtable.h> 37 #include <asm/gmap.h> 38 #include <asm/irq.h> 39 #include <asm/mmu_context.h> 40 #include <asm/facility.h> 41 #include "../kernel/entry.h" 42 43 #define __FAIL_ADDR_MASK -4096L 44 #define __SUBCODE_MASK 0x0600 45 #define __PF_RES_FIELD 0x8000000000000000ULL 46 47 #define VM_FAULT_BADCONTEXT 0x010000 48 #define VM_FAULT_BADMAP 0x020000 49 #define VM_FAULT_BADACCESS 0x040000 50 #define VM_FAULT_SIGNAL 0x080000 51 #define VM_FAULT_PFAULT 0x100000 52 53 enum fault_type { 54 KERNEL_FAULT, 55 USER_FAULT, 56 VDSO_FAULT, 57 GMAP_FAULT, 58 }; 59 60 static unsigned long store_indication __read_mostly; 61 62 static int __init fault_init(void) 63 { 64 if (test_facility(75)) 65 store_indication = 0xc00; 66 return 0; 67 } 68 early_initcall(fault_init); 69 70 /* 71 * Find out which address space caused the exception. 72 */ 73 static enum fault_type get_fault_type(struct pt_regs *regs) 74 { 75 unsigned long trans_exc_code; 76 77 trans_exc_code = regs->int_parm_long & 3; 78 if (likely(trans_exc_code == 0)) { 79 /* primary space exception */ 80 if (IS_ENABLED(CONFIG_PGSTE) && 81 test_pt_regs_flag(regs, PIF_GUEST_FAULT)) 82 return GMAP_FAULT; 83 if (current->thread.mm_segment == USER_DS) 84 return USER_FAULT; 85 return KERNEL_FAULT; 86 } 87 if (trans_exc_code == 2) { 88 /* secondary space exception */ 89 if (current->thread.mm_segment & 1) { 90 if (current->thread.mm_segment == USER_DS_SACF) 91 return USER_FAULT; 92 return KERNEL_FAULT; 93 } 94 return VDSO_FAULT; 95 } 96 if (trans_exc_code == 1) { 97 /* access register mode, not used in the kernel */ 98 return USER_FAULT; 99 } 100 /* home space exception -> access via kernel ASCE */ 101 return KERNEL_FAULT; 102 } 103 104 static int bad_address(void *p) 105 { 106 unsigned long dummy; 107 108 return probe_kernel_address((unsigned long *)p, dummy); 109 } 110 111 static void dump_pagetable(unsigned long asce, unsigned long address) 112 { 113 unsigned long *table = __va(asce & _ASCE_ORIGIN); 114 115 pr_alert("AS:%016lx ", asce); 116 switch (asce & _ASCE_TYPE_MASK) { 117 case _ASCE_TYPE_REGION1: 118 table += (address & _REGION1_INDEX) >> _REGION1_SHIFT; 119 if (bad_address(table)) 120 goto bad; 121 pr_cont("R1:%016lx ", *table); 122 if (*table & _REGION_ENTRY_INVALID) 123 goto out; 124 table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN); 125 /* fallthrough */ 126 case _ASCE_TYPE_REGION2: 127 table += (address & _REGION2_INDEX) >> _REGION2_SHIFT; 128 if (bad_address(table)) 129 goto bad; 130 pr_cont("R2:%016lx ", *table); 131 if (*table & _REGION_ENTRY_INVALID) 132 goto out; 133 table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN); 134 /* fallthrough */ 135 case _ASCE_TYPE_REGION3: 136 table += (address & _REGION3_INDEX) >> _REGION3_SHIFT; 137 if (bad_address(table)) 138 goto bad; 139 pr_cont("R3:%016lx ", *table); 140 if (*table & (_REGION_ENTRY_INVALID | _REGION3_ENTRY_LARGE)) 141 goto out; 142 table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN); 143 /* fallthrough */ 144 case _ASCE_TYPE_SEGMENT: 145 table += (address & _SEGMENT_INDEX) >> _SEGMENT_SHIFT; 146 if (bad_address(table)) 147 goto bad; 148 pr_cont("S:%016lx ", *table); 149 if (*table & (_SEGMENT_ENTRY_INVALID | _SEGMENT_ENTRY_LARGE)) 150 goto out; 151 table = (unsigned long *)(*table & _SEGMENT_ENTRY_ORIGIN); 152 } 153 table += (address & _PAGE_INDEX) >> _PAGE_SHIFT; 154 if (bad_address(table)) 155 goto bad; 156 pr_cont("P:%016lx ", *table); 157 out: 158 pr_cont("\n"); 159 return; 160 bad: 161 pr_cont("BAD\n"); 162 } 163 164 static void dump_fault_info(struct pt_regs *regs) 165 { 166 unsigned long asce; 167 168 pr_alert("Failing address: %016lx TEID: %016lx\n", 169 regs->int_parm_long & __FAIL_ADDR_MASK, regs->int_parm_long); 170 pr_alert("Fault in "); 171 switch (regs->int_parm_long & 3) { 172 case 3: 173 pr_cont("home space "); 174 break; 175 case 2: 176 pr_cont("secondary space "); 177 break; 178 case 1: 179 pr_cont("access register "); 180 break; 181 case 0: 182 pr_cont("primary space "); 183 break; 184 } 185 pr_cont("mode while using "); 186 switch (get_fault_type(regs)) { 187 case USER_FAULT: 188 asce = S390_lowcore.user_asce; 189 pr_cont("user "); 190 break; 191 case VDSO_FAULT: 192 asce = S390_lowcore.vdso_asce; 193 pr_cont("vdso "); 194 break; 195 case GMAP_FAULT: 196 asce = ((struct gmap *) S390_lowcore.gmap)->asce; 197 pr_cont("gmap "); 198 break; 199 case KERNEL_FAULT: 200 asce = S390_lowcore.kernel_asce; 201 pr_cont("kernel "); 202 break; 203 default: 204 unreachable(); 205 } 206 pr_cont("ASCE.\n"); 207 dump_pagetable(asce, regs->int_parm_long & __FAIL_ADDR_MASK); 208 } 209 210 int show_unhandled_signals = 1; 211 212 void report_user_fault(struct pt_regs *regs, long signr, int is_mm_fault) 213 { 214 if ((task_pid_nr(current) > 1) && !show_unhandled_signals) 215 return; 216 if (!unhandled_signal(current, signr)) 217 return; 218 if (!printk_ratelimit()) 219 return; 220 printk(KERN_ALERT "User process fault: interruption code %04x ilc:%d ", 221 regs->int_code & 0xffff, regs->int_code >> 17); 222 print_vma_addr(KERN_CONT "in ", regs->psw.addr); 223 printk(KERN_CONT "\n"); 224 if (is_mm_fault) 225 dump_fault_info(regs); 226 show_regs(regs); 227 } 228 229 /* 230 * Send SIGSEGV to task. This is an external routine 231 * to keep the stack usage of do_page_fault small. 232 */ 233 static noinline void do_sigsegv(struct pt_regs *regs, int si_code) 234 { 235 report_user_fault(regs, SIGSEGV, 1); 236 force_sig_fault(SIGSEGV, si_code, 237 (void __user *)(regs->int_parm_long & __FAIL_ADDR_MASK)); 238 } 239 240 const struct exception_table_entry *s390_search_extables(unsigned long addr) 241 { 242 const struct exception_table_entry *fixup; 243 244 fixup = search_extable(__start_dma_ex_table, 245 __stop_dma_ex_table - __start_dma_ex_table, 246 addr); 247 if (!fixup) 248 fixup = search_exception_tables(addr); 249 return fixup; 250 } 251 252 static noinline void do_no_context(struct pt_regs *regs) 253 { 254 const struct exception_table_entry *fixup; 255 256 /* Are we prepared to handle this kernel fault? */ 257 fixup = s390_search_extables(regs->psw.addr); 258 if (fixup) { 259 regs->psw.addr = extable_fixup(fixup); 260 return; 261 } 262 263 /* 264 * Oops. The kernel tried to access some bad page. We'll have to 265 * terminate things with extreme prejudice. 266 */ 267 if (get_fault_type(regs) == KERNEL_FAULT) 268 printk(KERN_ALERT "Unable to handle kernel pointer dereference" 269 " in virtual kernel address space\n"); 270 else 271 printk(KERN_ALERT "Unable to handle kernel paging request" 272 " in virtual user address space\n"); 273 dump_fault_info(regs); 274 die(regs, "Oops"); 275 do_exit(SIGKILL); 276 } 277 278 static noinline void do_low_address(struct pt_regs *regs) 279 { 280 /* Low-address protection hit in kernel mode means 281 NULL pointer write access in kernel mode. */ 282 if (regs->psw.mask & PSW_MASK_PSTATE) { 283 /* Low-address protection hit in user mode 'cannot happen'. */ 284 die (regs, "Low-address protection"); 285 do_exit(SIGKILL); 286 } 287 288 do_no_context(regs); 289 } 290 291 static noinline void do_sigbus(struct pt_regs *regs) 292 { 293 /* 294 * Send a sigbus, regardless of whether we were in kernel 295 * or user mode. 296 */ 297 force_sig_fault(SIGBUS, BUS_ADRERR, 298 (void __user *)(regs->int_parm_long & __FAIL_ADDR_MASK)); 299 } 300 301 static noinline int signal_return(struct pt_regs *regs) 302 { 303 u16 instruction; 304 int rc; 305 306 rc = __get_user(instruction, (u16 __user *) regs->psw.addr); 307 if (rc) 308 return rc; 309 if (instruction == 0x0a77) { 310 set_pt_regs_flag(regs, PIF_SYSCALL); 311 regs->int_code = 0x00040077; 312 return 0; 313 } else if (instruction == 0x0aad) { 314 set_pt_regs_flag(regs, PIF_SYSCALL); 315 regs->int_code = 0x000400ad; 316 return 0; 317 } 318 return -EACCES; 319 } 320 321 static noinline void do_fault_error(struct pt_regs *regs, int access, 322 vm_fault_t fault) 323 { 324 int si_code; 325 326 switch (fault) { 327 case VM_FAULT_BADACCESS: 328 if (access == VM_EXEC && signal_return(regs) == 0) 329 break; 330 case VM_FAULT_BADMAP: 331 /* Bad memory access. Check if it is kernel or user space. */ 332 if (user_mode(regs)) { 333 /* User mode accesses just cause a SIGSEGV */ 334 si_code = (fault == VM_FAULT_BADMAP) ? 335 SEGV_MAPERR : SEGV_ACCERR; 336 do_sigsegv(regs, si_code); 337 break; 338 } 339 case VM_FAULT_BADCONTEXT: 340 case VM_FAULT_PFAULT: 341 do_no_context(regs); 342 break; 343 case VM_FAULT_SIGNAL: 344 if (!user_mode(regs)) 345 do_no_context(regs); 346 break; 347 default: /* fault & VM_FAULT_ERROR */ 348 if (fault & VM_FAULT_OOM) { 349 if (!user_mode(regs)) 350 do_no_context(regs); 351 else 352 pagefault_out_of_memory(); 353 } else if (fault & VM_FAULT_SIGSEGV) { 354 /* Kernel mode? Handle exceptions or die */ 355 if (!user_mode(regs)) 356 do_no_context(regs); 357 else 358 do_sigsegv(regs, SEGV_MAPERR); 359 } else if (fault & VM_FAULT_SIGBUS) { 360 /* Kernel mode? Handle exceptions or die */ 361 if (!user_mode(regs)) 362 do_no_context(regs); 363 else 364 do_sigbus(regs); 365 } else 366 BUG(); 367 break; 368 } 369 } 370 371 /* 372 * This routine handles page faults. It determines the address, 373 * and the problem, and then passes it off to one of the appropriate 374 * routines. 375 * 376 * interruption code (int_code): 377 * 04 Protection -> Write-Protection (suprression) 378 * 10 Segment translation -> Not present (nullification) 379 * 11 Page translation -> Not present (nullification) 380 * 3b Region third trans. -> Not present (nullification) 381 */ 382 static inline vm_fault_t do_exception(struct pt_regs *regs, int access) 383 { 384 struct gmap *gmap; 385 struct task_struct *tsk; 386 struct mm_struct *mm; 387 struct vm_area_struct *vma; 388 enum fault_type type; 389 unsigned long trans_exc_code; 390 unsigned long address; 391 unsigned int flags; 392 vm_fault_t fault; 393 394 tsk = current; 395 /* 396 * The instruction that caused the program check has 397 * been nullified. Don't signal single step via SIGTRAP. 398 */ 399 clear_pt_regs_flag(regs, PIF_PER_TRAP); 400 401 if (kprobe_page_fault(regs, 14)) 402 return 0; 403 404 mm = tsk->mm; 405 trans_exc_code = regs->int_parm_long; 406 407 /* 408 * Verify that the fault happened in user space, that 409 * we are not in an interrupt and that there is a 410 * user context. 411 */ 412 fault = VM_FAULT_BADCONTEXT; 413 type = get_fault_type(regs); 414 switch (type) { 415 case KERNEL_FAULT: 416 goto out; 417 case VDSO_FAULT: 418 fault = VM_FAULT_BADMAP; 419 goto out; 420 case USER_FAULT: 421 case GMAP_FAULT: 422 if (faulthandler_disabled() || !mm) 423 goto out; 424 break; 425 } 426 427 address = trans_exc_code & __FAIL_ADDR_MASK; 428 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 429 flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; 430 if (user_mode(regs)) 431 flags |= FAULT_FLAG_USER; 432 if (access == VM_WRITE || (trans_exc_code & store_indication) == 0x400) 433 flags |= FAULT_FLAG_WRITE; 434 down_read(&mm->mmap_sem); 435 436 gmap = NULL; 437 if (IS_ENABLED(CONFIG_PGSTE) && type == GMAP_FAULT) { 438 gmap = (struct gmap *) S390_lowcore.gmap; 439 current->thread.gmap_addr = address; 440 current->thread.gmap_write_flag = !!(flags & FAULT_FLAG_WRITE); 441 current->thread.gmap_int_code = regs->int_code & 0xffff; 442 address = __gmap_translate(gmap, address); 443 if (address == -EFAULT) { 444 fault = VM_FAULT_BADMAP; 445 goto out_up; 446 } 447 if (gmap->pfault_enabled) 448 flags |= FAULT_FLAG_RETRY_NOWAIT; 449 } 450 451 retry: 452 fault = VM_FAULT_BADMAP; 453 vma = find_vma(mm, address); 454 if (!vma) 455 goto out_up; 456 457 if (unlikely(vma->vm_start > address)) { 458 if (!(vma->vm_flags & VM_GROWSDOWN)) 459 goto out_up; 460 if (expand_stack(vma, address)) 461 goto out_up; 462 } 463 464 /* 465 * Ok, we have a good vm_area for this memory access, so 466 * we can handle it.. 467 */ 468 fault = VM_FAULT_BADACCESS; 469 if (unlikely(!(vma->vm_flags & access))) 470 goto out_up; 471 472 if (is_vm_hugetlb_page(vma)) 473 address &= HPAGE_MASK; 474 /* 475 * If for any reason at all we couldn't handle the fault, 476 * make sure we exit gracefully rather than endlessly redo 477 * the fault. 478 */ 479 fault = handle_mm_fault(vma, address, flags); 480 /* No reason to continue if interrupted by SIGKILL. */ 481 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) { 482 fault = VM_FAULT_SIGNAL; 483 if (flags & FAULT_FLAG_RETRY_NOWAIT) 484 goto out_up; 485 goto out; 486 } 487 if (unlikely(fault & VM_FAULT_ERROR)) 488 goto out_up; 489 490 /* 491 * Major/minor page fault accounting is only done on the 492 * initial attempt. If we go through a retry, it is extremely 493 * likely that the page will be found in page cache at that point. 494 */ 495 if (flags & FAULT_FLAG_ALLOW_RETRY) { 496 if (fault & VM_FAULT_MAJOR) { 497 tsk->maj_flt++; 498 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, 499 regs, address); 500 } else { 501 tsk->min_flt++; 502 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, 503 regs, address); 504 } 505 if (fault & VM_FAULT_RETRY) { 506 if (IS_ENABLED(CONFIG_PGSTE) && gmap && 507 (flags & FAULT_FLAG_RETRY_NOWAIT)) { 508 /* FAULT_FLAG_RETRY_NOWAIT has been set, 509 * mmap_sem has not been released */ 510 current->thread.gmap_pfault = 1; 511 fault = VM_FAULT_PFAULT; 512 goto out_up; 513 } 514 /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk 515 * of starvation. */ 516 flags &= ~(FAULT_FLAG_ALLOW_RETRY | 517 FAULT_FLAG_RETRY_NOWAIT); 518 flags |= FAULT_FLAG_TRIED; 519 down_read(&mm->mmap_sem); 520 goto retry; 521 } 522 } 523 if (IS_ENABLED(CONFIG_PGSTE) && gmap) { 524 address = __gmap_link(gmap, current->thread.gmap_addr, 525 address); 526 if (address == -EFAULT) { 527 fault = VM_FAULT_BADMAP; 528 goto out_up; 529 } 530 if (address == -ENOMEM) { 531 fault = VM_FAULT_OOM; 532 goto out_up; 533 } 534 } 535 fault = 0; 536 out_up: 537 up_read(&mm->mmap_sem); 538 out: 539 return fault; 540 } 541 542 void do_protection_exception(struct pt_regs *regs) 543 { 544 unsigned long trans_exc_code; 545 int access; 546 vm_fault_t fault; 547 548 trans_exc_code = regs->int_parm_long; 549 /* 550 * Protection exceptions are suppressing, decrement psw address. 551 * The exception to this rule are aborted transactions, for these 552 * the PSW already points to the correct location. 553 */ 554 if (!(regs->int_code & 0x200)) 555 regs->psw.addr = __rewind_psw(regs->psw, regs->int_code >> 16); 556 /* 557 * Check for low-address protection. This needs to be treated 558 * as a special case because the translation exception code 559 * field is not guaranteed to contain valid data in this case. 560 */ 561 if (unlikely(!(trans_exc_code & 4))) { 562 do_low_address(regs); 563 return; 564 } 565 if (unlikely(MACHINE_HAS_NX && (trans_exc_code & 0x80))) { 566 regs->int_parm_long = (trans_exc_code & ~PAGE_MASK) | 567 (regs->psw.addr & PAGE_MASK); 568 access = VM_EXEC; 569 fault = VM_FAULT_BADACCESS; 570 } else { 571 access = VM_WRITE; 572 fault = do_exception(regs, access); 573 } 574 if (unlikely(fault)) 575 do_fault_error(regs, access, fault); 576 } 577 NOKPROBE_SYMBOL(do_protection_exception); 578 579 void do_dat_exception(struct pt_regs *regs) 580 { 581 int access; 582 vm_fault_t fault; 583 584 access = VM_READ | VM_EXEC | VM_WRITE; 585 fault = do_exception(regs, access); 586 if (unlikely(fault)) 587 do_fault_error(regs, access, fault); 588 } 589 NOKPROBE_SYMBOL(do_dat_exception); 590 591 #ifdef CONFIG_PFAULT 592 /* 593 * 'pfault' pseudo page faults routines. 594 */ 595 static int pfault_disable; 596 597 static int __init nopfault(char *str) 598 { 599 pfault_disable = 1; 600 return 1; 601 } 602 603 __setup("nopfault", nopfault); 604 605 struct pfault_refbk { 606 u16 refdiagc; 607 u16 reffcode; 608 u16 refdwlen; 609 u16 refversn; 610 u64 refgaddr; 611 u64 refselmk; 612 u64 refcmpmk; 613 u64 reserved; 614 } __attribute__ ((packed, aligned(8))); 615 616 static struct pfault_refbk pfault_init_refbk = { 617 .refdiagc = 0x258, 618 .reffcode = 0, 619 .refdwlen = 5, 620 .refversn = 2, 621 .refgaddr = __LC_LPP, 622 .refselmk = 1ULL << 48, 623 .refcmpmk = 1ULL << 48, 624 .reserved = __PF_RES_FIELD 625 }; 626 627 int pfault_init(void) 628 { 629 int rc; 630 631 if (pfault_disable) 632 return -1; 633 diag_stat_inc(DIAG_STAT_X258); 634 asm volatile( 635 " diag %1,%0,0x258\n" 636 "0: j 2f\n" 637 "1: la %0,8\n" 638 "2:\n" 639 EX_TABLE(0b,1b) 640 : "=d" (rc) 641 : "a" (&pfault_init_refbk), "m" (pfault_init_refbk) : "cc"); 642 return rc; 643 } 644 645 static struct pfault_refbk pfault_fini_refbk = { 646 .refdiagc = 0x258, 647 .reffcode = 1, 648 .refdwlen = 5, 649 .refversn = 2, 650 }; 651 652 void pfault_fini(void) 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" (&pfault_fini_refbk), "m" (pfault_fini_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_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