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 /* fallthrough */ 331 case VM_FAULT_BADMAP: 332 /* Bad memory access. Check if it is kernel or user space. */ 333 if (user_mode(regs)) { 334 /* User mode accesses just cause a SIGSEGV */ 335 si_code = (fault == VM_FAULT_BADMAP) ? 336 SEGV_MAPERR : SEGV_ACCERR; 337 do_sigsegv(regs, si_code); 338 break; 339 } 340 /* fallthrough */ 341 case VM_FAULT_BADCONTEXT: 342 /* fallthrough */ 343 case VM_FAULT_PFAULT: 344 do_no_context(regs); 345 break; 346 case VM_FAULT_SIGNAL: 347 if (!user_mode(regs)) 348 do_no_context(regs); 349 break; 350 default: /* fault & VM_FAULT_ERROR */ 351 if (fault & VM_FAULT_OOM) { 352 if (!user_mode(regs)) 353 do_no_context(regs); 354 else 355 pagefault_out_of_memory(); 356 } else if (fault & VM_FAULT_SIGSEGV) { 357 /* Kernel mode? Handle exceptions or die */ 358 if (!user_mode(regs)) 359 do_no_context(regs); 360 else 361 do_sigsegv(regs, SEGV_MAPERR); 362 } else if (fault & VM_FAULT_SIGBUS) { 363 /* Kernel mode? Handle exceptions or die */ 364 if (!user_mode(regs)) 365 do_no_context(regs); 366 else 367 do_sigbus(regs); 368 } else 369 BUG(); 370 break; 371 } 372 } 373 374 /* 375 * This routine handles page faults. It determines the address, 376 * and the problem, and then passes it off to one of the appropriate 377 * routines. 378 * 379 * interruption code (int_code): 380 * 04 Protection -> Write-Protection (suprression) 381 * 10 Segment translation -> Not present (nullification) 382 * 11 Page translation -> Not present (nullification) 383 * 3b Region third trans. -> Not present (nullification) 384 */ 385 static inline vm_fault_t do_exception(struct pt_regs *regs, int access) 386 { 387 struct gmap *gmap; 388 struct task_struct *tsk; 389 struct mm_struct *mm; 390 struct vm_area_struct *vma; 391 enum fault_type type; 392 unsigned long trans_exc_code; 393 unsigned long address; 394 unsigned int flags; 395 vm_fault_t fault; 396 397 tsk = current; 398 /* 399 * The instruction that caused the program check has 400 * been nullified. Don't signal single step via SIGTRAP. 401 */ 402 clear_pt_regs_flag(regs, PIF_PER_TRAP); 403 404 if (kprobe_page_fault(regs, 14)) 405 return 0; 406 407 mm = tsk->mm; 408 trans_exc_code = regs->int_parm_long; 409 410 /* 411 * Verify that the fault happened in user space, that 412 * we are not in an interrupt and that there is a 413 * user context. 414 */ 415 fault = VM_FAULT_BADCONTEXT; 416 type = get_fault_type(regs); 417 switch (type) { 418 case KERNEL_FAULT: 419 goto out; 420 case VDSO_FAULT: 421 fault = VM_FAULT_BADMAP; 422 goto out; 423 case USER_FAULT: 424 case GMAP_FAULT: 425 if (faulthandler_disabled() || !mm) 426 goto out; 427 break; 428 } 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 gmap = NULL; 440 if (IS_ENABLED(CONFIG_PGSTE) && type == GMAP_FAULT) { 441 gmap = (struct gmap *) S390_lowcore.gmap; 442 current->thread.gmap_addr = address; 443 current->thread.gmap_write_flag = !!(flags & FAULT_FLAG_WRITE); 444 current->thread.gmap_int_code = regs->int_code & 0xffff; 445 address = __gmap_translate(gmap, address); 446 if (address == -EFAULT) { 447 fault = VM_FAULT_BADMAP; 448 goto out_up; 449 } 450 if (gmap->pfault_enabled) 451 flags |= FAULT_FLAG_RETRY_NOWAIT; 452 } 453 454 retry: 455 fault = VM_FAULT_BADMAP; 456 vma = find_vma(mm, address); 457 if (!vma) 458 goto out_up; 459 460 if (unlikely(vma->vm_start > address)) { 461 if (!(vma->vm_flags & VM_GROWSDOWN)) 462 goto out_up; 463 if (expand_stack(vma, address)) 464 goto out_up; 465 } 466 467 /* 468 * Ok, we have a good vm_area for this memory access, so 469 * we can handle it.. 470 */ 471 fault = VM_FAULT_BADACCESS; 472 if (unlikely(!(vma->vm_flags & access))) 473 goto out_up; 474 475 if (is_vm_hugetlb_page(vma)) 476 address &= HPAGE_MASK; 477 /* 478 * If for any reason at all we couldn't handle the fault, 479 * make sure we exit gracefully rather than endlessly redo 480 * the fault. 481 */ 482 fault = handle_mm_fault(vma, address, flags); 483 /* No reason to continue if interrupted by SIGKILL. */ 484 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) { 485 fault = VM_FAULT_SIGNAL; 486 if (flags & FAULT_FLAG_RETRY_NOWAIT) 487 goto out_up; 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 if (IS_ENABLED(CONFIG_PGSTE) && gmap && 510 (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 /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk 518 * of starvation. */ 519 flags &= ~(FAULT_FLAG_ALLOW_RETRY | 520 FAULT_FLAG_RETRY_NOWAIT); 521 flags |= FAULT_FLAG_TRIED; 522 down_read(&mm->mmap_sem); 523 goto retry; 524 } 525 } 526 if (IS_ENABLED(CONFIG_PGSTE) && gmap) { 527 address = __gmap_link(gmap, current->thread.gmap_addr, 528 address); 529 if (address == -EFAULT) { 530 fault = VM_FAULT_BADMAP; 531 goto out_up; 532 } 533 if (address == -ENOMEM) { 534 fault = VM_FAULT_OOM; 535 goto out_up; 536 } 537 } 538 fault = 0; 539 out_up: 540 up_read(&mm->mmap_sem); 541 out: 542 return fault; 543 } 544 545 void do_protection_exception(struct pt_regs *regs) 546 { 547 unsigned long trans_exc_code; 548 int access; 549 vm_fault_t fault; 550 551 trans_exc_code = regs->int_parm_long; 552 /* 553 * Protection exceptions are suppressing, decrement psw address. 554 * The exception to this rule are aborted transactions, for these 555 * the PSW already points to the correct location. 556 */ 557 if (!(regs->int_code & 0x200)) 558 regs->psw.addr = __rewind_psw(regs->psw, regs->int_code >> 16); 559 /* 560 * Check for low-address protection. This needs to be treated 561 * as a special case because the translation exception code 562 * field is not guaranteed to contain valid data in this case. 563 */ 564 if (unlikely(!(trans_exc_code & 4))) { 565 do_low_address(regs); 566 return; 567 } 568 if (unlikely(MACHINE_HAS_NX && (trans_exc_code & 0x80))) { 569 regs->int_parm_long = (trans_exc_code & ~PAGE_MASK) | 570 (regs->psw.addr & PAGE_MASK); 571 access = VM_EXEC; 572 fault = VM_FAULT_BADACCESS; 573 } else { 574 access = VM_WRITE; 575 fault = do_exception(regs, access); 576 } 577 if (unlikely(fault)) 578 do_fault_error(regs, access, fault); 579 } 580 NOKPROBE_SYMBOL(do_protection_exception); 581 582 void do_dat_exception(struct pt_regs *regs) 583 { 584 int access; 585 vm_fault_t fault; 586 587 access = VM_READ | VM_EXEC | VM_WRITE; 588 fault = do_exception(regs, access); 589 if (unlikely(fault)) 590 do_fault_error(regs, access, fault); 591 } 592 NOKPROBE_SYMBOL(do_dat_exception); 593 594 #ifdef CONFIG_PFAULT 595 /* 596 * 'pfault' pseudo page faults routines. 597 */ 598 static int pfault_disable; 599 600 static int __init nopfault(char *str) 601 { 602 pfault_disable = 1; 603 return 1; 604 } 605 606 __setup("nopfault", nopfault); 607 608 struct pfault_refbk { 609 u16 refdiagc; 610 u16 reffcode; 611 u16 refdwlen; 612 u16 refversn; 613 u64 refgaddr; 614 u64 refselmk; 615 u64 refcmpmk; 616 u64 reserved; 617 } __attribute__ ((packed, aligned(8))); 618 619 static struct pfault_refbk pfault_init_refbk = { 620 .refdiagc = 0x258, 621 .reffcode = 0, 622 .refdwlen = 5, 623 .refversn = 2, 624 .refgaddr = __LC_LPP, 625 .refselmk = 1ULL << 48, 626 .refcmpmk = 1ULL << 48, 627 .reserved = __PF_RES_FIELD 628 }; 629 630 int pfault_init(void) 631 { 632 int rc; 633 634 if (pfault_disable) 635 return -1; 636 diag_stat_inc(DIAG_STAT_X258); 637 asm volatile( 638 " diag %1,%0,0x258\n" 639 "0: j 2f\n" 640 "1: la %0,8\n" 641 "2:\n" 642 EX_TABLE(0b,1b) 643 : "=d" (rc) 644 : "a" (&pfault_init_refbk), "m" (pfault_init_refbk) : "cc"); 645 return rc; 646 } 647 648 static struct pfault_refbk pfault_fini_refbk = { 649 .refdiagc = 0x258, 650 .reffcode = 1, 651 .refdwlen = 5, 652 .refversn = 2, 653 }; 654 655 void pfault_fini(void) 656 { 657 658 if (pfault_disable) 659 return; 660 diag_stat_inc(DIAG_STAT_X258); 661 asm volatile( 662 " diag %0,0,0x258\n" 663 "0: nopr %%r7\n" 664 EX_TABLE(0b,0b) 665 : : "a" (&pfault_fini_refbk), "m" (pfault_fini_refbk) : "cc"); 666 } 667 668 static DEFINE_SPINLOCK(pfault_lock); 669 static LIST_HEAD(pfault_list); 670 671 #define PF_COMPLETE 0x0080 672 673 /* 674 * The mechanism of our pfault code: if Linux is running as guest, runs a user 675 * space process and the user space process accesses a page that the host has 676 * paged out we get a pfault interrupt. 677 * 678 * This allows us, within the guest, to schedule a different process. Without 679 * this mechanism the host would have to suspend the whole virtual cpu until 680 * the page has been paged in. 681 * 682 * So when we get such an interrupt then we set the state of the current task 683 * to uninterruptible and also set the need_resched flag. Both happens within 684 * interrupt context(!). If we later on want to return to user space we 685 * recognize the need_resched flag and then call schedule(). It's not very 686 * obvious how this works... 687 * 688 * Of course we have a lot of additional fun with the completion interrupt (-> 689 * host signals that a page of a process has been paged in and the process can 690 * continue to run). This interrupt can arrive on any cpu and, since we have 691 * virtual cpus, actually appear before the interrupt that signals that a page 692 * is missing. 693 */ 694 static void pfault_interrupt(struct ext_code ext_code, 695 unsigned int param32, unsigned long param64) 696 { 697 struct task_struct *tsk; 698 __u16 subcode; 699 pid_t pid; 700 701 /* 702 * Get the external interruption subcode & pfault initial/completion 703 * signal bit. VM stores this in the 'cpu address' field associated 704 * with the external interrupt. 705 */ 706 subcode = ext_code.subcode; 707 if ((subcode & 0xff00) != __SUBCODE_MASK) 708 return; 709 inc_irq_stat(IRQEXT_PFL); 710 /* Get the token (= pid of the affected task). */ 711 pid = param64 & LPP_PID_MASK; 712 rcu_read_lock(); 713 tsk = find_task_by_pid_ns(pid, &init_pid_ns); 714 if (tsk) 715 get_task_struct(tsk); 716 rcu_read_unlock(); 717 if (!tsk) 718 return; 719 spin_lock(&pfault_lock); 720 if (subcode & PF_COMPLETE) { 721 /* signal bit is set -> a page has been swapped in by VM */ 722 if (tsk->thread.pfault_wait == 1) { 723 /* Initial interrupt was faster than the completion 724 * interrupt. pfault_wait is valid. Set pfault_wait 725 * back to zero and wake up the process. This can 726 * safely be done because the task is still sleeping 727 * and can't produce new pfaults. */ 728 tsk->thread.pfault_wait = 0; 729 list_del(&tsk->thread.list); 730 wake_up_process(tsk); 731 put_task_struct(tsk); 732 } else { 733 /* Completion interrupt was faster than initial 734 * interrupt. Set pfault_wait to -1 so the initial 735 * interrupt doesn't put the task to sleep. 736 * If the task is not running, ignore the completion 737 * interrupt since it must be a leftover of a PFAULT 738 * CANCEL operation which didn't remove all pending 739 * completion interrupts. */ 740 if (tsk->state == TASK_RUNNING) 741 tsk->thread.pfault_wait = -1; 742 } 743 } else { 744 /* signal bit not set -> a real page is missing. */ 745 if (WARN_ON_ONCE(tsk != current)) 746 goto out; 747 if (tsk->thread.pfault_wait == 1) { 748 /* Already on the list with a reference: put to sleep */ 749 goto block; 750 } else if (tsk->thread.pfault_wait == -1) { 751 /* Completion interrupt was faster than the initial 752 * interrupt (pfault_wait == -1). Set pfault_wait 753 * back to zero and exit. */ 754 tsk->thread.pfault_wait = 0; 755 } else { 756 /* Initial interrupt arrived before completion 757 * interrupt. Let the task sleep. 758 * An extra task reference is needed since a different 759 * cpu may set the task state to TASK_RUNNING again 760 * before the scheduler is reached. */ 761 get_task_struct(tsk); 762 tsk->thread.pfault_wait = 1; 763 list_add(&tsk->thread.list, &pfault_list); 764 block: 765 /* Since this must be a userspace fault, there 766 * is no kernel task state to trample. Rely on the 767 * return to userspace schedule() to block. */ 768 __set_current_state(TASK_UNINTERRUPTIBLE); 769 set_tsk_need_resched(tsk); 770 set_preempt_need_resched(); 771 } 772 } 773 out: 774 spin_unlock(&pfault_lock); 775 put_task_struct(tsk); 776 } 777 778 static int pfault_cpu_dead(unsigned int cpu) 779 { 780 struct thread_struct *thread, *next; 781 struct task_struct *tsk; 782 783 spin_lock_irq(&pfault_lock); 784 list_for_each_entry_safe(thread, next, &pfault_list, list) { 785 thread->pfault_wait = 0; 786 list_del(&thread->list); 787 tsk = container_of(thread, struct task_struct, thread); 788 wake_up_process(tsk); 789 put_task_struct(tsk); 790 } 791 spin_unlock_irq(&pfault_lock); 792 return 0; 793 } 794 795 static int __init pfault_irq_init(void) 796 { 797 int rc; 798 799 rc = register_external_irq(EXT_IRQ_CP_SERVICE, pfault_interrupt); 800 if (rc) 801 goto out_extint; 802 rc = pfault_init() == 0 ? 0 : -EOPNOTSUPP; 803 if (rc) 804 goto out_pfault; 805 irq_subclass_register(IRQ_SUBCLASS_SERVICE_SIGNAL); 806 cpuhp_setup_state_nocalls(CPUHP_S390_PFAULT_DEAD, "s390/pfault:dead", 807 NULL, pfault_cpu_dead); 808 return 0; 809 810 out_pfault: 811 unregister_external_irq(EXT_IRQ_CP_SERVICE, pfault_interrupt); 812 out_extint: 813 pfault_disable = 1; 814 return rc; 815 } 816 early_initcall(pfault_irq_init); 817 818 #endif /* CONFIG_PFAULT */ 819