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 static unsigned long store_indication __read_mostly; 54 55 static int __init fault_init(void) 56 { 57 if (test_facility(75)) 58 store_indication = 0xc00; 59 return 0; 60 } 61 early_initcall(fault_init); 62 63 static inline int notify_page_fault(struct pt_regs *regs) 64 { 65 int ret = 0; 66 67 /* kprobe_running() needs smp_processor_id() */ 68 if (kprobes_built_in() && !user_mode(regs)) { 69 preempt_disable(); 70 if (kprobe_running() && kprobe_fault_handler(regs, 14)) 71 ret = 1; 72 preempt_enable(); 73 } 74 return ret; 75 } 76 77 78 /* 79 * Unlock any spinlocks which will prevent us from getting the 80 * message out. 81 */ 82 void bust_spinlocks(int yes) 83 { 84 if (yes) { 85 oops_in_progress = 1; 86 } else { 87 int loglevel_save = console_loglevel; 88 console_unblank(); 89 oops_in_progress = 0; 90 /* 91 * OK, the message is on the console. Now we call printk() 92 * without oops_in_progress set so that printk will give klogd 93 * a poke. Hold onto your hats... 94 */ 95 console_loglevel = 15; 96 printk(" "); 97 console_loglevel = loglevel_save; 98 } 99 } 100 101 /* 102 * Returns the address space associated with the fault. 103 * Returns 0 for kernel space and 1 for user space. 104 */ 105 static inline int user_space_fault(struct pt_regs *regs) 106 { 107 unsigned long trans_exc_code; 108 109 /* 110 * The lowest two bits of the translation exception 111 * identification indicate which paging table was used. 112 */ 113 trans_exc_code = regs->int_parm_long & 3; 114 if (trans_exc_code == 3) /* home space -> kernel */ 115 return 0; 116 if (user_mode(regs)) 117 return 1; 118 if (trans_exc_code == 2) /* secondary space -> set_fs */ 119 return current->thread.mm_segment.ar4; 120 if (current->flags & PF_VCPU) 121 return 1; 122 return 0; 123 } 124 125 static int bad_address(void *p) 126 { 127 unsigned long dummy; 128 129 return probe_kernel_address((unsigned long *)p, dummy); 130 } 131 132 static void dump_pagetable(unsigned long asce, unsigned long address) 133 { 134 unsigned long *table = __va(asce & _ASCE_ORIGIN); 135 136 pr_alert("AS:%016lx ", asce); 137 switch (asce & _ASCE_TYPE_MASK) { 138 case _ASCE_TYPE_REGION1: 139 table += (address & _REGION1_INDEX) >> _REGION1_SHIFT; 140 if (bad_address(table)) 141 goto bad; 142 pr_cont("R1:%016lx ", *table); 143 if (*table & _REGION_ENTRY_INVALID) 144 goto out; 145 table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN); 146 /* fallthrough */ 147 case _ASCE_TYPE_REGION2: 148 table += (address & _REGION2_INDEX) >> _REGION2_SHIFT; 149 if (bad_address(table)) 150 goto bad; 151 pr_cont("R2:%016lx ", *table); 152 if (*table & _REGION_ENTRY_INVALID) 153 goto out; 154 table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN); 155 /* fallthrough */ 156 case _ASCE_TYPE_REGION3: 157 table += (address & _REGION3_INDEX) >> _REGION3_SHIFT; 158 if (bad_address(table)) 159 goto bad; 160 pr_cont("R3:%016lx ", *table); 161 if (*table & (_REGION_ENTRY_INVALID | _REGION3_ENTRY_LARGE)) 162 goto out; 163 table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN); 164 /* fallthrough */ 165 case _ASCE_TYPE_SEGMENT: 166 table += (address & _SEGMENT_INDEX) >> _SEGMENT_SHIFT; 167 if (bad_address(table)) 168 goto bad; 169 pr_cont("S:%016lx ", *table); 170 if (*table & (_SEGMENT_ENTRY_INVALID | _SEGMENT_ENTRY_LARGE)) 171 goto out; 172 table = (unsigned long *)(*table & _SEGMENT_ENTRY_ORIGIN); 173 } 174 table += (address & _PAGE_INDEX) >> _PAGE_SHIFT; 175 if (bad_address(table)) 176 goto bad; 177 pr_cont("P:%016lx ", *table); 178 out: 179 pr_cont("\n"); 180 return; 181 bad: 182 pr_cont("BAD\n"); 183 } 184 185 static void dump_fault_info(struct pt_regs *regs) 186 { 187 unsigned long asce; 188 189 pr_alert("Failing address: %016lx TEID: %016lx\n", 190 regs->int_parm_long & __FAIL_ADDR_MASK, regs->int_parm_long); 191 pr_alert("Fault in "); 192 switch (regs->int_parm_long & 3) { 193 case 3: 194 pr_cont("home space "); 195 break; 196 case 2: 197 pr_cont("secondary space "); 198 break; 199 case 1: 200 pr_cont("access register "); 201 break; 202 case 0: 203 pr_cont("primary space "); 204 break; 205 } 206 pr_cont("mode while using "); 207 if (!user_space_fault(regs)) { 208 asce = S390_lowcore.kernel_asce; 209 pr_cont("kernel "); 210 } 211 #ifdef CONFIG_PGSTE 212 else if ((current->flags & PF_VCPU) && S390_lowcore.gmap) { 213 struct gmap *gmap = (struct gmap *)S390_lowcore.gmap; 214 asce = gmap->asce; 215 pr_cont("gmap "); 216 } 217 #endif 218 else { 219 asce = S390_lowcore.user_asce; 220 pr_cont("user "); 221 } 222 pr_cont("ASCE.\n"); 223 dump_pagetable(asce, regs->int_parm_long & __FAIL_ADDR_MASK); 224 } 225 226 int show_unhandled_signals = 1; 227 228 void report_user_fault(struct pt_regs *regs, long signr, int is_mm_fault) 229 { 230 if ((task_pid_nr(current) > 1) && !show_unhandled_signals) 231 return; 232 if (!unhandled_signal(current, signr)) 233 return; 234 if (!printk_ratelimit()) 235 return; 236 printk(KERN_ALERT "User process fault: interruption code %04x ilc:%d ", 237 regs->int_code & 0xffff, regs->int_code >> 17); 238 print_vma_addr(KERN_CONT "in ", regs->psw.addr); 239 printk(KERN_CONT "\n"); 240 if (is_mm_fault) 241 dump_fault_info(regs); 242 show_regs(regs); 243 } 244 245 /* 246 * Send SIGSEGV to task. This is an external routine 247 * to keep the stack usage of do_page_fault small. 248 */ 249 static noinline void do_sigsegv(struct pt_regs *regs, int si_code) 250 { 251 struct siginfo si; 252 253 report_user_fault(regs, SIGSEGV, 1); 254 si.si_signo = SIGSEGV; 255 si.si_errno = 0; 256 si.si_code = si_code; 257 si.si_addr = (void __user *)(regs->int_parm_long & __FAIL_ADDR_MASK); 258 force_sig_info(SIGSEGV, &si, current); 259 } 260 261 static noinline void do_no_context(struct pt_regs *regs) 262 { 263 const struct exception_table_entry *fixup; 264 265 /* Are we prepared to handle this kernel fault? */ 266 fixup = search_exception_tables(regs->psw.addr); 267 if (fixup) { 268 regs->psw.addr = extable_fixup(fixup); 269 return; 270 } 271 272 /* 273 * Oops. The kernel tried to access some bad page. We'll have to 274 * terminate things with extreme prejudice. 275 */ 276 if (!user_space_fault(regs)) 277 printk(KERN_ALERT "Unable to handle kernel pointer dereference" 278 " in virtual kernel address space\n"); 279 else 280 printk(KERN_ALERT "Unable to handle kernel paging request" 281 " in virtual user address space\n"); 282 dump_fault_info(regs); 283 die(regs, "Oops"); 284 do_exit(SIGKILL); 285 } 286 287 static noinline void do_low_address(struct pt_regs *regs) 288 { 289 /* Low-address protection hit in kernel mode means 290 NULL pointer write access in kernel mode. */ 291 if (regs->psw.mask & PSW_MASK_PSTATE) { 292 /* Low-address protection hit in user mode 'cannot happen'. */ 293 die (regs, "Low-address protection"); 294 do_exit(SIGKILL); 295 } 296 297 do_no_context(regs); 298 } 299 300 static noinline void do_sigbus(struct pt_regs *regs) 301 { 302 struct task_struct *tsk = current; 303 struct siginfo si; 304 305 /* 306 * Send a sigbus, regardless of whether we were in kernel 307 * or user mode. 308 */ 309 si.si_signo = SIGBUS; 310 si.si_errno = 0; 311 si.si_code = BUS_ADRERR; 312 si.si_addr = (void __user *)(regs->int_parm_long & __FAIL_ADDR_MASK); 313 force_sig_info(SIGBUS, &si, tsk); 314 } 315 316 static noinline int signal_return(struct pt_regs *regs) 317 { 318 u16 instruction; 319 int rc; 320 321 rc = __get_user(instruction, (u16 __user *) regs->psw.addr); 322 if (rc) 323 return rc; 324 if (instruction == 0x0a77) { 325 set_pt_regs_flag(regs, PIF_SYSCALL); 326 regs->int_code = 0x00040077; 327 return 0; 328 } else if (instruction == 0x0aad) { 329 set_pt_regs_flag(regs, PIF_SYSCALL); 330 regs->int_code = 0x000400ad; 331 return 0; 332 } 333 return -EACCES; 334 } 335 336 static noinline void do_fault_error(struct pt_regs *regs, int access, int fault) 337 { 338 int si_code; 339 340 switch (fault) { 341 case VM_FAULT_BADACCESS: 342 if (access == VM_EXEC && signal_return(regs) == 0) 343 break; 344 case VM_FAULT_BADMAP: 345 /* Bad memory access. Check if it is kernel or user space. */ 346 if (user_mode(regs)) { 347 /* User mode accesses just cause a SIGSEGV */ 348 si_code = (fault == VM_FAULT_BADMAP) ? 349 SEGV_MAPERR : SEGV_ACCERR; 350 do_sigsegv(regs, si_code); 351 break; 352 } 353 case VM_FAULT_BADCONTEXT: 354 case VM_FAULT_PFAULT: 355 do_no_context(regs); 356 break; 357 case VM_FAULT_SIGNAL: 358 if (!user_mode(regs)) 359 do_no_context(regs); 360 break; 361 default: /* fault & VM_FAULT_ERROR */ 362 if (fault & VM_FAULT_OOM) { 363 if (!user_mode(regs)) 364 do_no_context(regs); 365 else 366 pagefault_out_of_memory(); 367 } else if (fault & VM_FAULT_SIGSEGV) { 368 /* Kernel mode? Handle exceptions or die */ 369 if (!user_mode(regs)) 370 do_no_context(regs); 371 else 372 do_sigsegv(regs, SEGV_MAPERR); 373 } else if (fault & VM_FAULT_SIGBUS) { 374 /* Kernel mode? Handle exceptions or die */ 375 if (!user_mode(regs)) 376 do_no_context(regs); 377 else 378 do_sigbus(regs); 379 } else 380 BUG(); 381 break; 382 } 383 } 384 385 /* 386 * This routine handles page faults. It determines the address, 387 * and the problem, and then passes it off to one of the appropriate 388 * routines. 389 * 390 * interruption code (int_code): 391 * 04 Protection -> Write-Protection (suprression) 392 * 10 Segment translation -> Not present (nullification) 393 * 11 Page translation -> Not present (nullification) 394 * 3b Region third trans. -> Not present (nullification) 395 */ 396 static inline int do_exception(struct pt_regs *regs, int access) 397 { 398 #ifdef CONFIG_PGSTE 399 struct gmap *gmap; 400 #endif 401 struct task_struct *tsk; 402 struct mm_struct *mm; 403 struct vm_area_struct *vma; 404 unsigned long trans_exc_code; 405 unsigned long address; 406 unsigned int flags; 407 int fault; 408 409 tsk = current; 410 /* 411 * The instruction that caused the program check has 412 * been nullified. Don't signal single step via SIGTRAP. 413 */ 414 clear_pt_regs_flag(regs, PIF_PER_TRAP); 415 416 if (notify_page_fault(regs)) 417 return 0; 418 419 mm = tsk->mm; 420 trans_exc_code = regs->int_parm_long; 421 422 /* 423 * Verify that the fault happened in user space, that 424 * we are not in an interrupt and that there is a 425 * user context. 426 */ 427 fault = VM_FAULT_BADCONTEXT; 428 if (unlikely(!user_space_fault(regs) || faulthandler_disabled() || !mm)) 429 goto out; 430 431 address = trans_exc_code & __FAIL_ADDR_MASK; 432 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 433 flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; 434 if (user_mode(regs)) 435 flags |= FAULT_FLAG_USER; 436 if (access == VM_WRITE || (trans_exc_code & store_indication) == 0x400) 437 flags |= FAULT_FLAG_WRITE; 438 down_read(&mm->mmap_sem); 439 440 #ifdef CONFIG_PGSTE 441 gmap = (current->flags & PF_VCPU) ? 442 (struct gmap *) S390_lowcore.gmap : NULL; 443 if (gmap) { 444 current->thread.gmap_addr = address; 445 current->thread.gmap_write_flag = !!(flags & FAULT_FLAG_WRITE); 446 current->thread.gmap_int_code = regs->int_code & 0xffff; 447 address = __gmap_translate(gmap, address); 448 if (address == -EFAULT) { 449 fault = VM_FAULT_BADMAP; 450 goto out_up; 451 } 452 if (gmap->pfault_enabled) 453 flags |= FAULT_FLAG_RETRY_NOWAIT; 454 } 455 #endif 456 457 retry: 458 fault = VM_FAULT_BADMAP; 459 vma = find_vma(mm, address); 460 if (!vma) 461 goto out_up; 462 463 if (unlikely(vma->vm_start > address)) { 464 if (!(vma->vm_flags & VM_GROWSDOWN)) 465 goto out_up; 466 if (expand_stack(vma, address)) 467 goto out_up; 468 } 469 470 /* 471 * Ok, we have a good vm_area for this memory access, so 472 * we can handle it.. 473 */ 474 fault = VM_FAULT_BADACCESS; 475 if (unlikely(!(vma->vm_flags & access))) 476 goto out_up; 477 478 if (is_vm_hugetlb_page(vma)) 479 address &= HPAGE_MASK; 480 /* 481 * If for any reason at all we couldn't handle the fault, 482 * make sure we exit gracefully rather than endlessly redo 483 * the fault. 484 */ 485 fault = handle_mm_fault(vma, address, flags); 486 /* No reason to continue if interrupted by SIGKILL. */ 487 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) { 488 fault = VM_FAULT_SIGNAL; 489 goto out; 490 } 491 if (unlikely(fault & VM_FAULT_ERROR)) 492 goto out_up; 493 494 /* 495 * Major/minor page fault accounting is only done on the 496 * initial attempt. If we go through a retry, it is extremely 497 * likely that the page will be found in page cache at that point. 498 */ 499 if (flags & FAULT_FLAG_ALLOW_RETRY) { 500 if (fault & VM_FAULT_MAJOR) { 501 tsk->maj_flt++; 502 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, 503 regs, address); 504 } else { 505 tsk->min_flt++; 506 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, 507 regs, address); 508 } 509 if (fault & VM_FAULT_RETRY) { 510 #ifdef CONFIG_PGSTE 511 if (gmap && (flags & FAULT_FLAG_RETRY_NOWAIT)) { 512 /* FAULT_FLAG_RETRY_NOWAIT has been set, 513 * mmap_sem has not been released */ 514 current->thread.gmap_pfault = 1; 515 fault = VM_FAULT_PFAULT; 516 goto out_up; 517 } 518 #endif 519 /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk 520 * of starvation. */ 521 flags &= ~(FAULT_FLAG_ALLOW_RETRY | 522 FAULT_FLAG_RETRY_NOWAIT); 523 flags |= FAULT_FLAG_TRIED; 524 down_read(&mm->mmap_sem); 525 goto retry; 526 } 527 } 528 #ifdef CONFIG_PGSTE 529 if (gmap) { 530 address = __gmap_link(gmap, current->thread.gmap_addr, 531 address); 532 if (address == -EFAULT) { 533 fault = VM_FAULT_BADMAP; 534 goto out_up; 535 } 536 if (address == -ENOMEM) { 537 fault = VM_FAULT_OOM; 538 goto out_up; 539 } 540 } 541 #endif 542 fault = 0; 543 out_up: 544 up_read(&mm->mmap_sem); 545 out: 546 return fault; 547 } 548 549 void do_protection_exception(struct pt_regs *regs) 550 { 551 unsigned long trans_exc_code; 552 int access, fault; 553 554 trans_exc_code = regs->int_parm_long; 555 /* 556 * Protection exceptions are suppressing, decrement psw address. 557 * The exception to this rule are aborted transactions, for these 558 * the PSW already points to the correct location. 559 */ 560 if (!(regs->int_code & 0x200)) 561 regs->psw.addr = __rewind_psw(regs->psw, regs->int_code >> 16); 562 /* 563 * Check for low-address protection. This needs to be treated 564 * as a special case because the translation exception code 565 * field is not guaranteed to contain valid data in this case. 566 */ 567 if (unlikely(!(trans_exc_code & 4))) { 568 do_low_address(regs); 569 return; 570 } 571 if (unlikely(MACHINE_HAS_NX && (trans_exc_code & 0x80))) { 572 regs->int_parm_long = (trans_exc_code & ~PAGE_MASK) | 573 (regs->psw.addr & PAGE_MASK); 574 access = VM_EXEC; 575 fault = VM_FAULT_BADACCESS; 576 } else { 577 access = VM_WRITE; 578 fault = do_exception(regs, access); 579 } 580 if (unlikely(fault)) 581 do_fault_error(regs, access, fault); 582 } 583 NOKPROBE_SYMBOL(do_protection_exception); 584 585 void do_dat_exception(struct pt_regs *regs) 586 { 587 int access, fault; 588 589 access = VM_READ | VM_EXEC | VM_WRITE; 590 fault = do_exception(regs, access); 591 if (unlikely(fault)) 592 do_fault_error(regs, access, fault); 593 } 594 NOKPROBE_SYMBOL(do_dat_exception); 595 596 #ifdef CONFIG_PFAULT 597 /* 598 * 'pfault' pseudo page faults routines. 599 */ 600 static int pfault_disable; 601 602 static int __init nopfault(char *str) 603 { 604 pfault_disable = 1; 605 return 1; 606 } 607 608 __setup("nopfault", nopfault); 609 610 struct pfault_refbk { 611 u16 refdiagc; 612 u16 reffcode; 613 u16 refdwlen; 614 u16 refversn; 615 u64 refgaddr; 616 u64 refselmk; 617 u64 refcmpmk; 618 u64 reserved; 619 } __attribute__ ((packed, aligned(8))); 620 621 int pfault_init(void) 622 { 623 struct pfault_refbk refbk = { 624 .refdiagc = 0x258, 625 .reffcode = 0, 626 .refdwlen = 5, 627 .refversn = 2, 628 .refgaddr = __LC_LPP, 629 .refselmk = 1ULL << 48, 630 .refcmpmk = 1ULL << 48, 631 .reserved = __PF_RES_FIELD }; 632 int rc; 633 634 if (pfault_disable) 635 return -1; 636 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) : "a" (&refbk), "m" (refbk) : "cc"); 644 return rc; 645 } 646 647 void pfault_fini(void) 648 { 649 struct pfault_refbk refbk = { 650 .refdiagc = 0x258, 651 .reffcode = 1, 652 .refdwlen = 5, 653 .refversn = 2, 654 }; 655 656 if (pfault_disable) 657 return; 658 diag_stat_inc(DIAG_STAT_X258); 659 asm volatile( 660 " diag %0,0,0x258\n" 661 "0: nopr %%r7\n" 662 EX_TABLE(0b,0b) 663 : : "a" (&refbk), "m" (refbk) : "cc"); 664 } 665 666 static DEFINE_SPINLOCK(pfault_lock); 667 static LIST_HEAD(pfault_list); 668 669 #define PF_COMPLETE 0x0080 670 671 /* 672 * The mechanism of our pfault code: if Linux is running as guest, runs a user 673 * space process and the user space process accesses a page that the host has 674 * paged out we get a pfault interrupt. 675 * 676 * This allows us, within the guest, to schedule a different process. Without 677 * this mechanism the host would have to suspend the whole virtual cpu until 678 * the page has been paged in. 679 * 680 * So when we get such an interrupt then we set the state of the current task 681 * to uninterruptible and also set the need_resched flag. Both happens within 682 * interrupt context(!). If we later on want to return to user space we 683 * recognize the need_resched flag and then call schedule(). It's not very 684 * obvious how this works... 685 * 686 * Of course we have a lot of additional fun with the completion interrupt (-> 687 * host signals that a page of a process has been paged in and the process can 688 * continue to run). This interrupt can arrive on any cpu and, since we have 689 * virtual cpus, actually appear before the interrupt that signals that a page 690 * is missing. 691 */ 692 static void pfault_interrupt(struct ext_code ext_code, 693 unsigned int param32, unsigned long param64) 694 { 695 struct task_struct *tsk; 696 __u16 subcode; 697 pid_t pid; 698 699 /* 700 * Get the external interruption subcode & pfault initial/completion 701 * signal bit. VM stores this in the 'cpu address' field associated 702 * with the external interrupt. 703 */ 704 subcode = ext_code.subcode; 705 if ((subcode & 0xff00) != __SUBCODE_MASK) 706 return; 707 inc_irq_stat(IRQEXT_PFL); 708 /* Get the token (= pid of the affected task). */ 709 pid = param64 & LPP_PFAULT_PID_MASK; 710 rcu_read_lock(); 711 tsk = find_task_by_pid_ns(pid, &init_pid_ns); 712 if (tsk) 713 get_task_struct(tsk); 714 rcu_read_unlock(); 715 if (!tsk) 716 return; 717 spin_lock(&pfault_lock); 718 if (subcode & PF_COMPLETE) { 719 /* signal bit is set -> a page has been swapped in by VM */ 720 if (tsk->thread.pfault_wait == 1) { 721 /* Initial interrupt was faster than the completion 722 * interrupt. pfault_wait is valid. Set pfault_wait 723 * back to zero and wake up the process. This can 724 * safely be done because the task is still sleeping 725 * and can't produce new pfaults. */ 726 tsk->thread.pfault_wait = 0; 727 list_del(&tsk->thread.list); 728 wake_up_process(tsk); 729 put_task_struct(tsk); 730 } else { 731 /* Completion interrupt was faster than initial 732 * interrupt. Set pfault_wait to -1 so the initial 733 * interrupt doesn't put the task to sleep. 734 * If the task is not running, ignore the completion 735 * interrupt since it must be a leftover of a PFAULT 736 * CANCEL operation which didn't remove all pending 737 * completion interrupts. */ 738 if (tsk->state == TASK_RUNNING) 739 tsk->thread.pfault_wait = -1; 740 } 741 } else { 742 /* signal bit not set -> a real page is missing. */ 743 if (WARN_ON_ONCE(tsk != current)) 744 goto out; 745 if (tsk->thread.pfault_wait == 1) { 746 /* Already on the list with a reference: put to sleep */ 747 goto block; 748 } else if (tsk->thread.pfault_wait == -1) { 749 /* Completion interrupt was faster than the initial 750 * interrupt (pfault_wait == -1). Set pfault_wait 751 * back to zero and exit. */ 752 tsk->thread.pfault_wait = 0; 753 } else { 754 /* Initial interrupt arrived before completion 755 * interrupt. Let the task sleep. 756 * An extra task reference is needed since a different 757 * cpu may set the task state to TASK_RUNNING again 758 * before the scheduler is reached. */ 759 get_task_struct(tsk); 760 tsk->thread.pfault_wait = 1; 761 list_add(&tsk->thread.list, &pfault_list); 762 block: 763 /* Since this must be a userspace fault, there 764 * is no kernel task state to trample. Rely on the 765 * return to userspace schedule() to block. */ 766 __set_current_state(TASK_UNINTERRUPTIBLE); 767 set_tsk_need_resched(tsk); 768 set_preempt_need_resched(); 769 } 770 } 771 out: 772 spin_unlock(&pfault_lock); 773 put_task_struct(tsk); 774 } 775 776 static int pfault_cpu_dead(unsigned int cpu) 777 { 778 struct thread_struct *thread, *next; 779 struct task_struct *tsk; 780 781 spin_lock_irq(&pfault_lock); 782 list_for_each_entry_safe(thread, next, &pfault_list, list) { 783 thread->pfault_wait = 0; 784 list_del(&thread->list); 785 tsk = container_of(thread, struct task_struct, thread); 786 wake_up_process(tsk); 787 put_task_struct(tsk); 788 } 789 spin_unlock_irq(&pfault_lock); 790 return 0; 791 } 792 793 static int __init pfault_irq_init(void) 794 { 795 int rc; 796 797 rc = register_external_irq(EXT_IRQ_CP_SERVICE, pfault_interrupt); 798 if (rc) 799 goto out_extint; 800 rc = pfault_init() == 0 ? 0 : -EOPNOTSUPP; 801 if (rc) 802 goto out_pfault; 803 irq_subclass_register(IRQ_SUBCLASS_SERVICE_SIGNAL); 804 cpuhp_setup_state_nocalls(CPUHP_S390_PFAULT_DEAD, "s390/pfault:dead", 805 NULL, pfault_cpu_dead); 806 return 0; 807 808 out_pfault: 809 unregister_external_irq(EXT_IRQ_CP_SERVICE, pfault_interrupt); 810 out_extint: 811 pfault_disable = 1; 812 return rc; 813 } 814 early_initcall(pfault_irq_init); 815 816 #endif /* CONFIG_PFAULT */ 817