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 static inline int notify_page_fault(struct pt_regs *regs) 71 { 72 int ret = 0; 73 74 /* kprobe_running() needs smp_processor_id() */ 75 if (kprobes_built_in() && !user_mode(regs)) { 76 preempt_disable(); 77 if (kprobe_running() && kprobe_fault_handler(regs, 14)) 78 ret = 1; 79 preempt_enable(); 80 } 81 return ret; 82 } 83 84 /* 85 * Find out which address space caused the exception. 86 * Access register mode is impossible, ignore space == 3. 87 */ 88 static inline enum fault_type get_fault_type(struct pt_regs *regs) 89 { 90 unsigned long trans_exc_code; 91 92 trans_exc_code = regs->int_parm_long & 3; 93 if (likely(trans_exc_code == 0)) { 94 /* primary space exception */ 95 if (IS_ENABLED(CONFIG_PGSTE) && 96 test_pt_regs_flag(regs, PIF_GUEST_FAULT)) 97 return GMAP_FAULT; 98 if (current->thread.mm_segment == USER_DS) 99 return USER_FAULT; 100 return KERNEL_FAULT; 101 } 102 if (trans_exc_code == 2) { 103 /* secondary space exception */ 104 if (current->thread.mm_segment & 1) { 105 if (current->thread.mm_segment == USER_DS_SACF) 106 return USER_FAULT; 107 return KERNEL_FAULT; 108 } 109 return VDSO_FAULT; 110 } 111 /* home space exception -> access via kernel ASCE */ 112 return KERNEL_FAULT; 113 } 114 115 static int bad_address(void *p) 116 { 117 unsigned long dummy; 118 119 return probe_kernel_address((unsigned long *)p, dummy); 120 } 121 122 static void dump_pagetable(unsigned long asce, unsigned long address) 123 { 124 unsigned long *table = __va(asce & _ASCE_ORIGIN); 125 126 pr_alert("AS:%016lx ", asce); 127 switch (asce & _ASCE_TYPE_MASK) { 128 case _ASCE_TYPE_REGION1: 129 table += (address & _REGION1_INDEX) >> _REGION1_SHIFT; 130 if (bad_address(table)) 131 goto bad; 132 pr_cont("R1:%016lx ", *table); 133 if (*table & _REGION_ENTRY_INVALID) 134 goto out; 135 table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN); 136 /* fallthrough */ 137 case _ASCE_TYPE_REGION2: 138 table += (address & _REGION2_INDEX) >> _REGION2_SHIFT; 139 if (bad_address(table)) 140 goto bad; 141 pr_cont("R2:%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_REGION3: 147 table += (address & _REGION3_INDEX) >> _REGION3_SHIFT; 148 if (bad_address(table)) 149 goto bad; 150 pr_cont("R3:%016lx ", *table); 151 if (*table & (_REGION_ENTRY_INVALID | _REGION3_ENTRY_LARGE)) 152 goto out; 153 table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN); 154 /* fallthrough */ 155 case _ASCE_TYPE_SEGMENT: 156 table += (address & _SEGMENT_INDEX) >> _SEGMENT_SHIFT; 157 if (bad_address(table)) 158 goto bad; 159 pr_cont("S:%016lx ", *table); 160 if (*table & (_SEGMENT_ENTRY_INVALID | _SEGMENT_ENTRY_LARGE)) 161 goto out; 162 table = (unsigned long *)(*table & _SEGMENT_ENTRY_ORIGIN); 163 } 164 table += (address & _PAGE_INDEX) >> _PAGE_SHIFT; 165 if (bad_address(table)) 166 goto bad; 167 pr_cont("P:%016lx ", *table); 168 out: 169 pr_cont("\n"); 170 return; 171 bad: 172 pr_cont("BAD\n"); 173 } 174 175 static void dump_fault_info(struct pt_regs *regs) 176 { 177 unsigned long asce; 178 179 pr_alert("Failing address: %016lx TEID: %016lx\n", 180 regs->int_parm_long & __FAIL_ADDR_MASK, regs->int_parm_long); 181 pr_alert("Fault in "); 182 switch (regs->int_parm_long & 3) { 183 case 3: 184 pr_cont("home space "); 185 break; 186 case 2: 187 pr_cont("secondary space "); 188 break; 189 case 1: 190 pr_cont("access register "); 191 break; 192 case 0: 193 pr_cont("primary space "); 194 break; 195 } 196 pr_cont("mode while using "); 197 switch (get_fault_type(regs)) { 198 case USER_FAULT: 199 asce = S390_lowcore.user_asce; 200 pr_cont("user "); 201 break; 202 case VDSO_FAULT: 203 asce = S390_lowcore.vdso_asce; 204 pr_cont("vdso "); 205 break; 206 case GMAP_FAULT: 207 asce = ((struct gmap *) S390_lowcore.gmap)->asce; 208 pr_cont("gmap "); 209 break; 210 case KERNEL_FAULT: 211 asce = S390_lowcore.kernel_asce; 212 pr_cont("kernel "); 213 break; 214 } 215 pr_cont("ASCE.\n"); 216 dump_pagetable(asce, regs->int_parm_long & __FAIL_ADDR_MASK); 217 } 218 219 int show_unhandled_signals = 1; 220 221 void report_user_fault(struct pt_regs *regs, long signr, int is_mm_fault) 222 { 223 if ((task_pid_nr(current) > 1) && !show_unhandled_signals) 224 return; 225 if (!unhandled_signal(current, signr)) 226 return; 227 if (!printk_ratelimit()) 228 return; 229 printk(KERN_ALERT "User process fault: interruption code %04x ilc:%d ", 230 regs->int_code & 0xffff, regs->int_code >> 17); 231 print_vma_addr(KERN_CONT "in ", regs->psw.addr); 232 printk(KERN_CONT "\n"); 233 if (is_mm_fault) 234 dump_fault_info(regs); 235 show_regs(regs); 236 } 237 238 /* 239 * Send SIGSEGV to task. This is an external routine 240 * to keep the stack usage of do_page_fault small. 241 */ 242 static noinline void do_sigsegv(struct pt_regs *regs, int si_code) 243 { 244 report_user_fault(regs, SIGSEGV, 1); 245 force_sig_fault(SIGSEGV, si_code, 246 (void __user *)(regs->int_parm_long & __FAIL_ADDR_MASK), 247 current); 248 } 249 250 static noinline void do_no_context(struct pt_regs *regs) 251 { 252 const struct exception_table_entry *fixup; 253 254 /* Are we prepared to handle this kernel fault? */ 255 fixup = search_exception_tables(regs->psw.addr); 256 if (fixup) { 257 regs->psw.addr = extable_fixup(fixup); 258 return; 259 } 260 261 /* 262 * Oops. The kernel tried to access some bad page. We'll have to 263 * terminate things with extreme prejudice. 264 */ 265 if (get_fault_type(regs) == KERNEL_FAULT) 266 printk(KERN_ALERT "Unable to handle kernel pointer dereference" 267 " in virtual kernel address space\n"); 268 else 269 printk(KERN_ALERT "Unable to handle kernel paging request" 270 " in virtual user address space\n"); 271 dump_fault_info(regs); 272 die(regs, "Oops"); 273 do_exit(SIGKILL); 274 } 275 276 static noinline void do_low_address(struct pt_regs *regs) 277 { 278 /* Low-address protection hit in kernel mode means 279 NULL pointer write access in kernel mode. */ 280 if (regs->psw.mask & PSW_MASK_PSTATE) { 281 /* Low-address protection hit in user mode 'cannot happen'. */ 282 die (regs, "Low-address protection"); 283 do_exit(SIGKILL); 284 } 285 286 do_no_context(regs); 287 } 288 289 static noinline void do_sigbus(struct pt_regs *regs) 290 { 291 /* 292 * Send a sigbus, regardless of whether we were in kernel 293 * or user mode. 294 */ 295 force_sig_fault(SIGBUS, BUS_ADRERR, 296 (void __user *)(regs->int_parm_long & __FAIL_ADDR_MASK), 297 current); 298 } 299 300 static noinline int signal_return(struct pt_regs *regs) 301 { 302 u16 instruction; 303 int rc; 304 305 rc = __get_user(instruction, (u16 __user *) regs->psw.addr); 306 if (rc) 307 return rc; 308 if (instruction == 0x0a77) { 309 set_pt_regs_flag(regs, PIF_SYSCALL); 310 regs->int_code = 0x00040077; 311 return 0; 312 } else if (instruction == 0x0aad) { 313 set_pt_regs_flag(regs, PIF_SYSCALL); 314 regs->int_code = 0x000400ad; 315 return 0; 316 } 317 return -EACCES; 318 } 319 320 static noinline void do_fault_error(struct pt_regs *regs, int access, 321 vm_fault_t fault) 322 { 323 int si_code; 324 325 switch (fault) { 326 case VM_FAULT_BADACCESS: 327 if (access == VM_EXEC && signal_return(regs) == 0) 328 break; 329 case VM_FAULT_BADMAP: 330 /* Bad memory access. Check if it is kernel or user space. */ 331 if (user_mode(regs)) { 332 /* User mode accesses just cause a SIGSEGV */ 333 si_code = (fault == VM_FAULT_BADMAP) ? 334 SEGV_MAPERR : SEGV_ACCERR; 335 do_sigsegv(regs, si_code); 336 break; 337 } 338 case VM_FAULT_BADCONTEXT: 339 case VM_FAULT_PFAULT: 340 do_no_context(regs); 341 break; 342 case VM_FAULT_SIGNAL: 343 if (!user_mode(regs)) 344 do_no_context(regs); 345 break; 346 default: /* fault & VM_FAULT_ERROR */ 347 if (fault & VM_FAULT_OOM) { 348 if (!user_mode(regs)) 349 do_no_context(regs); 350 else 351 pagefault_out_of_memory(); 352 } else if (fault & VM_FAULT_SIGSEGV) { 353 /* Kernel mode? Handle exceptions or die */ 354 if (!user_mode(regs)) 355 do_no_context(regs); 356 else 357 do_sigsegv(regs, SEGV_MAPERR); 358 } else if (fault & VM_FAULT_SIGBUS) { 359 /* Kernel mode? Handle exceptions or die */ 360 if (!user_mode(regs)) 361 do_no_context(regs); 362 else 363 do_sigbus(regs); 364 } else 365 BUG(); 366 break; 367 } 368 } 369 370 /* 371 * This routine handles page faults. It determines the address, 372 * and the problem, and then passes it off to one of the appropriate 373 * routines. 374 * 375 * interruption code (int_code): 376 * 04 Protection -> Write-Protection (suprression) 377 * 10 Segment translation -> Not present (nullification) 378 * 11 Page translation -> Not present (nullification) 379 * 3b Region third trans. -> Not present (nullification) 380 */ 381 static inline vm_fault_t do_exception(struct pt_regs *regs, int access) 382 { 383 struct gmap *gmap; 384 struct task_struct *tsk; 385 struct mm_struct *mm; 386 struct vm_area_struct *vma; 387 enum fault_type type; 388 unsigned long trans_exc_code; 389 unsigned long address; 390 unsigned int flags; 391 vm_fault_t fault; 392 393 tsk = current; 394 /* 395 * The instruction that caused the program check has 396 * been nullified. Don't signal single step via SIGTRAP. 397 */ 398 clear_pt_regs_flag(regs, PIF_PER_TRAP); 399 400 if (notify_page_fault(regs)) 401 return 0; 402 403 mm = tsk->mm; 404 trans_exc_code = regs->int_parm_long; 405 406 /* 407 * Verify that the fault happened in user space, that 408 * we are not in an interrupt and that there is a 409 * user context. 410 */ 411 fault = VM_FAULT_BADCONTEXT; 412 type = get_fault_type(regs); 413 switch (type) { 414 case KERNEL_FAULT: 415 goto out; 416 case VDSO_FAULT: 417 fault = VM_FAULT_BADMAP; 418 goto out; 419 case USER_FAULT: 420 case GMAP_FAULT: 421 if (faulthandler_disabled() || !mm) 422 goto out; 423 break; 424 } 425 426 address = trans_exc_code & __FAIL_ADDR_MASK; 427 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 428 flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; 429 if (user_mode(regs)) 430 flags |= FAULT_FLAG_USER; 431 if (access == VM_WRITE || (trans_exc_code & store_indication) == 0x400) 432 flags |= FAULT_FLAG_WRITE; 433 down_read(&mm->mmap_sem); 434 435 gmap = NULL; 436 if (IS_ENABLED(CONFIG_PGSTE) && type == GMAP_FAULT) { 437 gmap = (struct gmap *) S390_lowcore.gmap; 438 current->thread.gmap_addr = address; 439 current->thread.gmap_write_flag = !!(flags & FAULT_FLAG_WRITE); 440 current->thread.gmap_int_code = regs->int_code & 0xffff; 441 address = __gmap_translate(gmap, address); 442 if (address == -EFAULT) { 443 fault = VM_FAULT_BADMAP; 444 goto out_up; 445 } 446 if (gmap->pfault_enabled) 447 flags |= FAULT_FLAG_RETRY_NOWAIT; 448 } 449 450 retry: 451 fault = VM_FAULT_BADMAP; 452 vma = find_vma(mm, address); 453 if (!vma) 454 goto out_up; 455 456 if (unlikely(vma->vm_start > address)) { 457 if (!(vma->vm_flags & VM_GROWSDOWN)) 458 goto out_up; 459 if (expand_stack(vma, address)) 460 goto out_up; 461 } 462 463 /* 464 * Ok, we have a good vm_area for this memory access, so 465 * we can handle it.. 466 */ 467 fault = VM_FAULT_BADACCESS; 468 if (unlikely(!(vma->vm_flags & access))) 469 goto out_up; 470 471 if (is_vm_hugetlb_page(vma)) 472 address &= HPAGE_MASK; 473 /* 474 * If for any reason at all we couldn't handle the fault, 475 * make sure we exit gracefully rather than endlessly redo 476 * the fault. 477 */ 478 fault = handle_mm_fault(vma, address, flags); 479 /* No reason to continue if interrupted by SIGKILL. */ 480 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) { 481 fault = VM_FAULT_SIGNAL; 482 if (flags & FAULT_FLAG_RETRY_NOWAIT) 483 goto out_up; 484 goto out; 485 } 486 if (unlikely(fault & VM_FAULT_ERROR)) 487 goto out_up; 488 489 /* 490 * Major/minor page fault accounting is only done on the 491 * initial attempt. If we go through a retry, it is extremely 492 * likely that the page will be found in page cache at that point. 493 */ 494 if (flags & FAULT_FLAG_ALLOW_RETRY) { 495 if (fault & VM_FAULT_MAJOR) { 496 tsk->maj_flt++; 497 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, 498 regs, address); 499 } else { 500 tsk->min_flt++; 501 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, 502 regs, address); 503 } 504 if (fault & VM_FAULT_RETRY) { 505 if (IS_ENABLED(CONFIG_PGSTE) && gmap && 506 (flags & FAULT_FLAG_RETRY_NOWAIT)) { 507 /* FAULT_FLAG_RETRY_NOWAIT has been set, 508 * mmap_sem has not been released */ 509 current->thread.gmap_pfault = 1; 510 fault = VM_FAULT_PFAULT; 511 goto out_up; 512 } 513 /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk 514 * of starvation. */ 515 flags &= ~(FAULT_FLAG_ALLOW_RETRY | 516 FAULT_FLAG_RETRY_NOWAIT); 517 flags |= FAULT_FLAG_TRIED; 518 down_read(&mm->mmap_sem); 519 goto retry; 520 } 521 } 522 if (IS_ENABLED(CONFIG_PGSTE) && gmap) { 523 address = __gmap_link(gmap, current->thread.gmap_addr, 524 address); 525 if (address == -EFAULT) { 526 fault = VM_FAULT_BADMAP; 527 goto out_up; 528 } 529 if (address == -ENOMEM) { 530 fault = VM_FAULT_OOM; 531 goto out_up; 532 } 533 } 534 fault = 0; 535 out_up: 536 up_read(&mm->mmap_sem); 537 out: 538 return fault; 539 } 540 541 void do_protection_exception(struct pt_regs *regs) 542 { 543 unsigned long trans_exc_code; 544 int access; 545 vm_fault_t fault; 546 547 trans_exc_code = regs->int_parm_long; 548 /* 549 * Protection exceptions are suppressing, decrement psw address. 550 * The exception to this rule are aborted transactions, for these 551 * the PSW already points to the correct location. 552 */ 553 if (!(regs->int_code & 0x200)) 554 regs->psw.addr = __rewind_psw(regs->psw, regs->int_code >> 16); 555 /* 556 * Check for low-address protection. This needs to be treated 557 * as a special case because the translation exception code 558 * field is not guaranteed to contain valid data in this case. 559 */ 560 if (unlikely(!(trans_exc_code & 4))) { 561 do_low_address(regs); 562 return; 563 } 564 if (unlikely(MACHINE_HAS_NX && (trans_exc_code & 0x80))) { 565 regs->int_parm_long = (trans_exc_code & ~PAGE_MASK) | 566 (regs->psw.addr & PAGE_MASK); 567 access = VM_EXEC; 568 fault = VM_FAULT_BADACCESS; 569 } else { 570 access = VM_WRITE; 571 fault = do_exception(regs, access); 572 } 573 if (unlikely(fault)) 574 do_fault_error(regs, access, fault); 575 } 576 NOKPROBE_SYMBOL(do_protection_exception); 577 578 void do_dat_exception(struct pt_regs *regs) 579 { 580 int access; 581 vm_fault_t fault; 582 583 access = VM_READ | VM_EXEC | VM_WRITE; 584 fault = do_exception(regs, access); 585 if (unlikely(fault)) 586 do_fault_error(regs, access, fault); 587 } 588 NOKPROBE_SYMBOL(do_dat_exception); 589 590 #ifdef CONFIG_PFAULT 591 /* 592 * 'pfault' pseudo page faults routines. 593 */ 594 static int pfault_disable; 595 596 static int __init nopfault(char *str) 597 { 598 pfault_disable = 1; 599 return 1; 600 } 601 602 __setup("nopfault", nopfault); 603 604 struct pfault_refbk { 605 u16 refdiagc; 606 u16 reffcode; 607 u16 refdwlen; 608 u16 refversn; 609 u64 refgaddr; 610 u64 refselmk; 611 u64 refcmpmk; 612 u64 reserved; 613 } __attribute__ ((packed, aligned(8))); 614 615 static struct pfault_refbk pfault_init_refbk = { 616 .refdiagc = 0x258, 617 .reffcode = 0, 618 .refdwlen = 5, 619 .refversn = 2, 620 .refgaddr = __LC_LPP, 621 .refselmk = 1ULL << 48, 622 .refcmpmk = 1ULL << 48, 623 .reserved = __PF_RES_FIELD 624 }; 625 626 int pfault_init(void) 627 { 628 int rc; 629 630 if (pfault_disable) 631 return -1; 632 diag_stat_inc(DIAG_STAT_X258); 633 asm volatile( 634 " diag %1,%0,0x258\n" 635 "0: j 2f\n" 636 "1: la %0,8\n" 637 "2:\n" 638 EX_TABLE(0b,1b) 639 : "=d" (rc) 640 : "a" (&pfault_init_refbk), "m" (pfault_init_refbk) : "cc"); 641 return rc; 642 } 643 644 static struct pfault_refbk pfault_fini_refbk = { 645 .refdiagc = 0x258, 646 .reffcode = 1, 647 .refdwlen = 5, 648 .refversn = 2, 649 }; 650 651 void pfault_fini(void) 652 { 653 654 if (pfault_disable) 655 return; 656 diag_stat_inc(DIAG_STAT_X258); 657 asm volatile( 658 " diag %0,0,0x258\n" 659 "0: nopr %%r7\n" 660 EX_TABLE(0b,0b) 661 : : "a" (&pfault_fini_refbk), "m" (pfault_fini_refbk) : "cc"); 662 } 663 664 static DEFINE_SPINLOCK(pfault_lock); 665 static LIST_HEAD(pfault_list); 666 667 #define PF_COMPLETE 0x0080 668 669 /* 670 * The mechanism of our pfault code: if Linux is running as guest, runs a user 671 * space process and the user space process accesses a page that the host has 672 * paged out we get a pfault interrupt. 673 * 674 * This allows us, within the guest, to schedule a different process. Without 675 * this mechanism the host would have to suspend the whole virtual cpu until 676 * the page has been paged in. 677 * 678 * So when we get such an interrupt then we set the state of the current task 679 * to uninterruptible and also set the need_resched flag. Both happens within 680 * interrupt context(!). If we later on want to return to user space we 681 * recognize the need_resched flag and then call schedule(). It's not very 682 * obvious how this works... 683 * 684 * Of course we have a lot of additional fun with the completion interrupt (-> 685 * host signals that a page of a process has been paged in and the process can 686 * continue to run). This interrupt can arrive on any cpu and, since we have 687 * virtual cpus, actually appear before the interrupt that signals that a page 688 * is missing. 689 */ 690 static void pfault_interrupt(struct ext_code ext_code, 691 unsigned int param32, unsigned long param64) 692 { 693 struct task_struct *tsk; 694 __u16 subcode; 695 pid_t pid; 696 697 /* 698 * Get the external interruption subcode & pfault initial/completion 699 * signal bit. VM stores this in the 'cpu address' field associated 700 * with the external interrupt. 701 */ 702 subcode = ext_code.subcode; 703 if ((subcode & 0xff00) != __SUBCODE_MASK) 704 return; 705 inc_irq_stat(IRQEXT_PFL); 706 /* Get the token (= pid of the affected task). */ 707 pid = param64 & LPP_PID_MASK; 708 rcu_read_lock(); 709 tsk = find_task_by_pid_ns(pid, &init_pid_ns); 710 if (tsk) 711 get_task_struct(tsk); 712 rcu_read_unlock(); 713 if (!tsk) 714 return; 715 spin_lock(&pfault_lock); 716 if (subcode & PF_COMPLETE) { 717 /* signal bit is set -> a page has been swapped in by VM */ 718 if (tsk->thread.pfault_wait == 1) { 719 /* Initial interrupt was faster than the completion 720 * interrupt. pfault_wait is valid. Set pfault_wait 721 * back to zero and wake up the process. This can 722 * safely be done because the task is still sleeping 723 * and can't produce new pfaults. */ 724 tsk->thread.pfault_wait = 0; 725 list_del(&tsk->thread.list); 726 wake_up_process(tsk); 727 put_task_struct(tsk); 728 } else { 729 /* Completion interrupt was faster than initial 730 * interrupt. Set pfault_wait to -1 so the initial 731 * interrupt doesn't put the task to sleep. 732 * If the task is not running, ignore the completion 733 * interrupt since it must be a leftover of a PFAULT 734 * CANCEL operation which didn't remove all pending 735 * completion interrupts. */ 736 if (tsk->state == TASK_RUNNING) 737 tsk->thread.pfault_wait = -1; 738 } 739 } else { 740 /* signal bit not set -> a real page is missing. */ 741 if (WARN_ON_ONCE(tsk != current)) 742 goto out; 743 if (tsk->thread.pfault_wait == 1) { 744 /* Already on the list with a reference: put to sleep */ 745 goto block; 746 } else if (tsk->thread.pfault_wait == -1) { 747 /* Completion interrupt was faster than the initial 748 * interrupt (pfault_wait == -1). Set pfault_wait 749 * back to zero and exit. */ 750 tsk->thread.pfault_wait = 0; 751 } else { 752 /* Initial interrupt arrived before completion 753 * interrupt. Let the task sleep. 754 * An extra task reference is needed since a different 755 * cpu may set the task state to TASK_RUNNING again 756 * before the scheduler is reached. */ 757 get_task_struct(tsk); 758 tsk->thread.pfault_wait = 1; 759 list_add(&tsk->thread.list, &pfault_list); 760 block: 761 /* Since this must be a userspace fault, there 762 * is no kernel task state to trample. Rely on the 763 * return to userspace schedule() to block. */ 764 __set_current_state(TASK_UNINTERRUPTIBLE); 765 set_tsk_need_resched(tsk); 766 set_preempt_need_resched(); 767 } 768 } 769 out: 770 spin_unlock(&pfault_lock); 771 put_task_struct(tsk); 772 } 773 774 static int pfault_cpu_dead(unsigned int cpu) 775 { 776 struct thread_struct *thread, *next; 777 struct task_struct *tsk; 778 779 spin_lock_irq(&pfault_lock); 780 list_for_each_entry_safe(thread, next, &pfault_list, list) { 781 thread->pfault_wait = 0; 782 list_del(&thread->list); 783 tsk = container_of(thread, struct task_struct, thread); 784 wake_up_process(tsk); 785 put_task_struct(tsk); 786 } 787 spin_unlock_irq(&pfault_lock); 788 return 0; 789 } 790 791 static int __init pfault_irq_init(void) 792 { 793 int rc; 794 795 rc = register_external_irq(EXT_IRQ_CP_SERVICE, pfault_interrupt); 796 if (rc) 797 goto out_extint; 798 rc = pfault_init() == 0 ? 0 : -EOPNOTSUPP; 799 if (rc) 800 goto out_pfault; 801 irq_subclass_register(IRQ_SUBCLASS_SERVICE_SIGNAL); 802 cpuhp_setup_state_nocalls(CPUHP_S390_PFAULT_DEAD, "s390/pfault:dead", 803 NULL, pfault_cpu_dead); 804 return 0; 805 806 out_pfault: 807 unregister_external_irq(EXT_IRQ_CP_SERVICE, pfault_interrupt); 808 out_extint: 809 pfault_disable = 1; 810 return rc; 811 } 812 early_initcall(pfault_irq_init); 813 814 #endif /* CONFIG_PFAULT */ 815