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 const struct exception_table_entry *s390_search_extables(unsigned long addr) 251 { 252 const struct exception_table_entry *fixup; 253 254 fixup = search_extable(__start_dma_ex_table, 255 __stop_dma_ex_table - __start_dma_ex_table, 256 addr); 257 if (!fixup) 258 fixup = search_exception_tables(addr); 259 return fixup; 260 } 261 262 static noinline void do_no_context(struct pt_regs *regs) 263 { 264 const struct exception_table_entry *fixup; 265 266 /* Are we prepared to handle this kernel fault? */ 267 fixup = s390_search_extables(regs->psw.addr); 268 if (fixup) { 269 regs->psw.addr = extable_fixup(fixup); 270 return; 271 } 272 273 /* 274 * Oops. The kernel tried to access some bad page. We'll have to 275 * terminate things with extreme prejudice. 276 */ 277 if (get_fault_type(regs) == KERNEL_FAULT) 278 printk(KERN_ALERT "Unable to handle kernel pointer dereference" 279 " in virtual kernel address space\n"); 280 else 281 printk(KERN_ALERT "Unable to handle kernel paging request" 282 " in virtual user address space\n"); 283 dump_fault_info(regs); 284 die(regs, "Oops"); 285 do_exit(SIGKILL); 286 } 287 288 static noinline void do_low_address(struct pt_regs *regs) 289 { 290 /* Low-address protection hit in kernel mode means 291 NULL pointer write access in kernel mode. */ 292 if (regs->psw.mask & PSW_MASK_PSTATE) { 293 /* Low-address protection hit in user mode 'cannot happen'. */ 294 die (regs, "Low-address protection"); 295 do_exit(SIGKILL); 296 } 297 298 do_no_context(regs); 299 } 300 301 static noinline void do_sigbus(struct pt_regs *regs) 302 { 303 /* 304 * Send a sigbus, regardless of whether we were in kernel 305 * or user mode. 306 */ 307 force_sig_fault(SIGBUS, BUS_ADRERR, 308 (void __user *)(regs->int_parm_long & __FAIL_ADDR_MASK), 309 current); 310 } 311 312 static noinline int signal_return(struct pt_regs *regs) 313 { 314 u16 instruction; 315 int rc; 316 317 rc = __get_user(instruction, (u16 __user *) regs->psw.addr); 318 if (rc) 319 return rc; 320 if (instruction == 0x0a77) { 321 set_pt_regs_flag(regs, PIF_SYSCALL); 322 regs->int_code = 0x00040077; 323 return 0; 324 } else if (instruction == 0x0aad) { 325 set_pt_regs_flag(regs, PIF_SYSCALL); 326 regs->int_code = 0x000400ad; 327 return 0; 328 } 329 return -EACCES; 330 } 331 332 static noinline void do_fault_error(struct pt_regs *regs, int access, 333 vm_fault_t fault) 334 { 335 int si_code; 336 337 switch (fault) { 338 case VM_FAULT_BADACCESS: 339 if (access == VM_EXEC && signal_return(regs) == 0) 340 break; 341 case VM_FAULT_BADMAP: 342 /* Bad memory access. Check if it is kernel or user space. */ 343 if (user_mode(regs)) { 344 /* User mode accesses just cause a SIGSEGV */ 345 si_code = (fault == VM_FAULT_BADMAP) ? 346 SEGV_MAPERR : SEGV_ACCERR; 347 do_sigsegv(regs, si_code); 348 break; 349 } 350 case VM_FAULT_BADCONTEXT: 351 case VM_FAULT_PFAULT: 352 do_no_context(regs); 353 break; 354 case VM_FAULT_SIGNAL: 355 if (!user_mode(regs)) 356 do_no_context(regs); 357 break; 358 default: /* fault & VM_FAULT_ERROR */ 359 if (fault & VM_FAULT_OOM) { 360 if (!user_mode(regs)) 361 do_no_context(regs); 362 else 363 pagefault_out_of_memory(); 364 } else if (fault & VM_FAULT_SIGSEGV) { 365 /* Kernel mode? Handle exceptions or die */ 366 if (!user_mode(regs)) 367 do_no_context(regs); 368 else 369 do_sigsegv(regs, SEGV_MAPERR); 370 } else if (fault & VM_FAULT_SIGBUS) { 371 /* Kernel mode? Handle exceptions or die */ 372 if (!user_mode(regs)) 373 do_no_context(regs); 374 else 375 do_sigbus(regs); 376 } else 377 BUG(); 378 break; 379 } 380 } 381 382 /* 383 * This routine handles page faults. It determines the address, 384 * and the problem, and then passes it off to one of the appropriate 385 * routines. 386 * 387 * interruption code (int_code): 388 * 04 Protection -> Write-Protection (suprression) 389 * 10 Segment translation -> Not present (nullification) 390 * 11 Page translation -> Not present (nullification) 391 * 3b Region third trans. -> Not present (nullification) 392 */ 393 static inline vm_fault_t do_exception(struct pt_regs *regs, int access) 394 { 395 struct gmap *gmap; 396 struct task_struct *tsk; 397 struct mm_struct *mm; 398 struct vm_area_struct *vma; 399 enum fault_type type; 400 unsigned long trans_exc_code; 401 unsigned long address; 402 unsigned int flags; 403 vm_fault_t fault; 404 405 tsk = current; 406 /* 407 * The instruction that caused the program check has 408 * been nullified. Don't signal single step via SIGTRAP. 409 */ 410 clear_pt_regs_flag(regs, PIF_PER_TRAP); 411 412 if (notify_page_fault(regs)) 413 return 0; 414 415 mm = tsk->mm; 416 trans_exc_code = regs->int_parm_long; 417 418 /* 419 * Verify that the fault happened in user space, that 420 * we are not in an interrupt and that there is a 421 * user context. 422 */ 423 fault = VM_FAULT_BADCONTEXT; 424 type = get_fault_type(regs); 425 switch (type) { 426 case KERNEL_FAULT: 427 goto out; 428 case VDSO_FAULT: 429 fault = VM_FAULT_BADMAP; 430 goto out; 431 case USER_FAULT: 432 case GMAP_FAULT: 433 if (faulthandler_disabled() || !mm) 434 goto out; 435 break; 436 } 437 438 address = trans_exc_code & __FAIL_ADDR_MASK; 439 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 440 flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; 441 if (user_mode(regs)) 442 flags |= FAULT_FLAG_USER; 443 if (access == VM_WRITE || (trans_exc_code & store_indication) == 0x400) 444 flags |= FAULT_FLAG_WRITE; 445 down_read(&mm->mmap_sem); 446 447 gmap = NULL; 448 if (IS_ENABLED(CONFIG_PGSTE) && type == GMAP_FAULT) { 449 gmap = (struct gmap *) S390_lowcore.gmap; 450 current->thread.gmap_addr = address; 451 current->thread.gmap_write_flag = !!(flags & FAULT_FLAG_WRITE); 452 current->thread.gmap_int_code = regs->int_code & 0xffff; 453 address = __gmap_translate(gmap, address); 454 if (address == -EFAULT) { 455 fault = VM_FAULT_BADMAP; 456 goto out_up; 457 } 458 if (gmap->pfault_enabled) 459 flags |= FAULT_FLAG_RETRY_NOWAIT; 460 } 461 462 retry: 463 fault = VM_FAULT_BADMAP; 464 vma = find_vma(mm, address); 465 if (!vma) 466 goto out_up; 467 468 if (unlikely(vma->vm_start > address)) { 469 if (!(vma->vm_flags & VM_GROWSDOWN)) 470 goto out_up; 471 if (expand_stack(vma, address)) 472 goto out_up; 473 } 474 475 /* 476 * Ok, we have a good vm_area for this memory access, so 477 * we can handle it.. 478 */ 479 fault = VM_FAULT_BADACCESS; 480 if (unlikely(!(vma->vm_flags & access))) 481 goto out_up; 482 483 if (is_vm_hugetlb_page(vma)) 484 address &= HPAGE_MASK; 485 /* 486 * If for any reason at all we couldn't handle the fault, 487 * make sure we exit gracefully rather than endlessly redo 488 * the fault. 489 */ 490 fault = handle_mm_fault(vma, address, flags); 491 /* No reason to continue if interrupted by SIGKILL. */ 492 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) { 493 fault = VM_FAULT_SIGNAL; 494 if (flags & FAULT_FLAG_RETRY_NOWAIT) 495 goto out_up; 496 goto out; 497 } 498 if (unlikely(fault & VM_FAULT_ERROR)) 499 goto out_up; 500 501 /* 502 * Major/minor page fault accounting is only done on the 503 * initial attempt. If we go through a retry, it is extremely 504 * likely that the page will be found in page cache at that point. 505 */ 506 if (flags & FAULT_FLAG_ALLOW_RETRY) { 507 if (fault & VM_FAULT_MAJOR) { 508 tsk->maj_flt++; 509 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, 510 regs, address); 511 } else { 512 tsk->min_flt++; 513 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, 514 regs, address); 515 } 516 if (fault & VM_FAULT_RETRY) { 517 if (IS_ENABLED(CONFIG_PGSTE) && gmap && 518 (flags & FAULT_FLAG_RETRY_NOWAIT)) { 519 /* FAULT_FLAG_RETRY_NOWAIT has been set, 520 * mmap_sem has not been released */ 521 current->thread.gmap_pfault = 1; 522 fault = VM_FAULT_PFAULT; 523 goto out_up; 524 } 525 /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk 526 * of starvation. */ 527 flags &= ~(FAULT_FLAG_ALLOW_RETRY | 528 FAULT_FLAG_RETRY_NOWAIT); 529 flags |= FAULT_FLAG_TRIED; 530 down_read(&mm->mmap_sem); 531 goto retry; 532 } 533 } 534 if (IS_ENABLED(CONFIG_PGSTE) && gmap) { 535 address = __gmap_link(gmap, current->thread.gmap_addr, 536 address); 537 if (address == -EFAULT) { 538 fault = VM_FAULT_BADMAP; 539 goto out_up; 540 } 541 if (address == -ENOMEM) { 542 fault = VM_FAULT_OOM; 543 goto out_up; 544 } 545 } 546 fault = 0; 547 out_up: 548 up_read(&mm->mmap_sem); 549 out: 550 return fault; 551 } 552 553 void do_protection_exception(struct pt_regs *regs) 554 { 555 unsigned long trans_exc_code; 556 int access; 557 vm_fault_t fault; 558 559 trans_exc_code = regs->int_parm_long; 560 /* 561 * Protection exceptions are suppressing, decrement psw address. 562 * The exception to this rule are aborted transactions, for these 563 * the PSW already points to the correct location. 564 */ 565 if (!(regs->int_code & 0x200)) 566 regs->psw.addr = __rewind_psw(regs->psw, regs->int_code >> 16); 567 /* 568 * Check for low-address protection. This needs to be treated 569 * as a special case because the translation exception code 570 * field is not guaranteed to contain valid data in this case. 571 */ 572 if (unlikely(!(trans_exc_code & 4))) { 573 do_low_address(regs); 574 return; 575 } 576 if (unlikely(MACHINE_HAS_NX && (trans_exc_code & 0x80))) { 577 regs->int_parm_long = (trans_exc_code & ~PAGE_MASK) | 578 (regs->psw.addr & PAGE_MASK); 579 access = VM_EXEC; 580 fault = VM_FAULT_BADACCESS; 581 } else { 582 access = VM_WRITE; 583 fault = do_exception(regs, access); 584 } 585 if (unlikely(fault)) 586 do_fault_error(regs, access, fault); 587 } 588 NOKPROBE_SYMBOL(do_protection_exception); 589 590 void do_dat_exception(struct pt_regs *regs) 591 { 592 int access; 593 vm_fault_t fault; 594 595 access = VM_READ | VM_EXEC | VM_WRITE; 596 fault = do_exception(regs, access); 597 if (unlikely(fault)) 598 do_fault_error(regs, access, fault); 599 } 600 NOKPROBE_SYMBOL(do_dat_exception); 601 602 #ifdef CONFIG_PFAULT 603 /* 604 * 'pfault' pseudo page faults routines. 605 */ 606 static int pfault_disable; 607 608 static int __init nopfault(char *str) 609 { 610 pfault_disable = 1; 611 return 1; 612 } 613 614 __setup("nopfault", nopfault); 615 616 struct pfault_refbk { 617 u16 refdiagc; 618 u16 reffcode; 619 u16 refdwlen; 620 u16 refversn; 621 u64 refgaddr; 622 u64 refselmk; 623 u64 refcmpmk; 624 u64 reserved; 625 } __attribute__ ((packed, aligned(8))); 626 627 static struct pfault_refbk pfault_init_refbk = { 628 .refdiagc = 0x258, 629 .reffcode = 0, 630 .refdwlen = 5, 631 .refversn = 2, 632 .refgaddr = __LC_LPP, 633 .refselmk = 1ULL << 48, 634 .refcmpmk = 1ULL << 48, 635 .reserved = __PF_RES_FIELD 636 }; 637 638 int pfault_init(void) 639 { 640 int rc; 641 642 if (pfault_disable) 643 return -1; 644 diag_stat_inc(DIAG_STAT_X258); 645 asm volatile( 646 " diag %1,%0,0x258\n" 647 "0: j 2f\n" 648 "1: la %0,8\n" 649 "2:\n" 650 EX_TABLE(0b,1b) 651 : "=d" (rc) 652 : "a" (&pfault_init_refbk), "m" (pfault_init_refbk) : "cc"); 653 return rc; 654 } 655 656 static struct pfault_refbk pfault_fini_refbk = { 657 .refdiagc = 0x258, 658 .reffcode = 1, 659 .refdwlen = 5, 660 .refversn = 2, 661 }; 662 663 void pfault_fini(void) 664 { 665 666 if (pfault_disable) 667 return; 668 diag_stat_inc(DIAG_STAT_X258); 669 asm volatile( 670 " diag %0,0,0x258\n" 671 "0: nopr %%r7\n" 672 EX_TABLE(0b,0b) 673 : : "a" (&pfault_fini_refbk), "m" (pfault_fini_refbk) : "cc"); 674 } 675 676 static DEFINE_SPINLOCK(pfault_lock); 677 static LIST_HEAD(pfault_list); 678 679 #define PF_COMPLETE 0x0080 680 681 /* 682 * The mechanism of our pfault code: if Linux is running as guest, runs a user 683 * space process and the user space process accesses a page that the host has 684 * paged out we get a pfault interrupt. 685 * 686 * This allows us, within the guest, to schedule a different process. Without 687 * this mechanism the host would have to suspend the whole virtual cpu until 688 * the page has been paged in. 689 * 690 * So when we get such an interrupt then we set the state of the current task 691 * to uninterruptible and also set the need_resched flag. Both happens within 692 * interrupt context(!). If we later on want to return to user space we 693 * recognize the need_resched flag and then call schedule(). It's not very 694 * obvious how this works... 695 * 696 * Of course we have a lot of additional fun with the completion interrupt (-> 697 * host signals that a page of a process has been paged in and the process can 698 * continue to run). This interrupt can arrive on any cpu and, since we have 699 * virtual cpus, actually appear before the interrupt that signals that a page 700 * is missing. 701 */ 702 static void pfault_interrupt(struct ext_code ext_code, 703 unsigned int param32, unsigned long param64) 704 { 705 struct task_struct *tsk; 706 __u16 subcode; 707 pid_t pid; 708 709 /* 710 * Get the external interruption subcode & pfault initial/completion 711 * signal bit. VM stores this in the 'cpu address' field associated 712 * with the external interrupt. 713 */ 714 subcode = ext_code.subcode; 715 if ((subcode & 0xff00) != __SUBCODE_MASK) 716 return; 717 inc_irq_stat(IRQEXT_PFL); 718 /* Get the token (= pid of the affected task). */ 719 pid = param64 & LPP_PID_MASK; 720 rcu_read_lock(); 721 tsk = find_task_by_pid_ns(pid, &init_pid_ns); 722 if (tsk) 723 get_task_struct(tsk); 724 rcu_read_unlock(); 725 if (!tsk) 726 return; 727 spin_lock(&pfault_lock); 728 if (subcode & PF_COMPLETE) { 729 /* signal bit is set -> a page has been swapped in by VM */ 730 if (tsk->thread.pfault_wait == 1) { 731 /* Initial interrupt was faster than the completion 732 * interrupt. pfault_wait is valid. Set pfault_wait 733 * back to zero and wake up the process. This can 734 * safely be done because the task is still sleeping 735 * and can't produce new pfaults. */ 736 tsk->thread.pfault_wait = 0; 737 list_del(&tsk->thread.list); 738 wake_up_process(tsk); 739 put_task_struct(tsk); 740 } else { 741 /* Completion interrupt was faster than initial 742 * interrupt. Set pfault_wait to -1 so the initial 743 * interrupt doesn't put the task to sleep. 744 * If the task is not running, ignore the completion 745 * interrupt since it must be a leftover of a PFAULT 746 * CANCEL operation which didn't remove all pending 747 * completion interrupts. */ 748 if (tsk->state == TASK_RUNNING) 749 tsk->thread.pfault_wait = -1; 750 } 751 } else { 752 /* signal bit not set -> a real page is missing. */ 753 if (WARN_ON_ONCE(tsk != current)) 754 goto out; 755 if (tsk->thread.pfault_wait == 1) { 756 /* Already on the list with a reference: put to sleep */ 757 goto block; 758 } else if (tsk->thread.pfault_wait == -1) { 759 /* Completion interrupt was faster than the initial 760 * interrupt (pfault_wait == -1). Set pfault_wait 761 * back to zero and exit. */ 762 tsk->thread.pfault_wait = 0; 763 } else { 764 /* Initial interrupt arrived before completion 765 * interrupt. Let the task sleep. 766 * An extra task reference is needed since a different 767 * cpu may set the task state to TASK_RUNNING again 768 * before the scheduler is reached. */ 769 get_task_struct(tsk); 770 tsk->thread.pfault_wait = 1; 771 list_add(&tsk->thread.list, &pfault_list); 772 block: 773 /* Since this must be a userspace fault, there 774 * is no kernel task state to trample. Rely on the 775 * return to userspace schedule() to block. */ 776 __set_current_state(TASK_UNINTERRUPTIBLE); 777 set_tsk_need_resched(tsk); 778 set_preempt_need_resched(); 779 } 780 } 781 out: 782 spin_unlock(&pfault_lock); 783 put_task_struct(tsk); 784 } 785 786 static int pfault_cpu_dead(unsigned int cpu) 787 { 788 struct thread_struct *thread, *next; 789 struct task_struct *tsk; 790 791 spin_lock_irq(&pfault_lock); 792 list_for_each_entry_safe(thread, next, &pfault_list, list) { 793 thread->pfault_wait = 0; 794 list_del(&thread->list); 795 tsk = container_of(thread, struct task_struct, thread); 796 wake_up_process(tsk); 797 put_task_struct(tsk); 798 } 799 spin_unlock_irq(&pfault_lock); 800 return 0; 801 } 802 803 static int __init pfault_irq_init(void) 804 { 805 int rc; 806 807 rc = register_external_irq(EXT_IRQ_CP_SERVICE, pfault_interrupt); 808 if (rc) 809 goto out_extint; 810 rc = pfault_init() == 0 ? 0 : -EOPNOTSUPP; 811 if (rc) 812 goto out_pfault; 813 irq_subclass_register(IRQ_SUBCLASS_SERVICE_SIGNAL); 814 cpuhp_setup_state_nocalls(CPUHP_S390_PFAULT_DEAD, "s390/pfault:dead", 815 NULL, pfault_cpu_dead); 816 return 0; 817 818 out_pfault: 819 unregister_external_irq(EXT_IRQ_CP_SERVICE, pfault_interrupt); 820 out_extint: 821 pfault_disable = 1; 822 return rc; 823 } 824 early_initcall(pfault_irq_init); 825 826 #endif /* CONFIG_PFAULT */ 827