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 */ 87 static enum fault_type get_fault_type(struct pt_regs *regs) 88 { 89 unsigned long trans_exc_code; 90 91 trans_exc_code = regs->int_parm_long & 3; 92 if (likely(trans_exc_code == 0)) { 93 /* primary space exception */ 94 if (IS_ENABLED(CONFIG_PGSTE) && 95 test_pt_regs_flag(regs, PIF_GUEST_FAULT)) 96 return GMAP_FAULT; 97 if (current->thread.mm_segment == USER_DS) 98 return USER_FAULT; 99 return KERNEL_FAULT; 100 } 101 if (trans_exc_code == 2) { 102 /* secondary space exception */ 103 if (current->thread.mm_segment & 1) { 104 if (current->thread.mm_segment == USER_DS_SACF) 105 return USER_FAULT; 106 return KERNEL_FAULT; 107 } 108 return VDSO_FAULT; 109 } 110 if (trans_exc_code == 1) { 111 /* access register mode, not used in the kernel */ 112 return USER_FAULT; 113 } 114 /* home space exception -> access via kernel ASCE */ 115 return KERNEL_FAULT; 116 } 117 118 static int bad_address(void *p) 119 { 120 unsigned long dummy; 121 122 return probe_kernel_address((unsigned long *)p, dummy); 123 } 124 125 static void dump_pagetable(unsigned long asce, unsigned long address) 126 { 127 unsigned long *table = __va(asce & _ASCE_ORIGIN); 128 129 pr_alert("AS:%016lx ", asce); 130 switch (asce & _ASCE_TYPE_MASK) { 131 case _ASCE_TYPE_REGION1: 132 table += (address & _REGION1_INDEX) >> _REGION1_SHIFT; 133 if (bad_address(table)) 134 goto bad; 135 pr_cont("R1:%016lx ", *table); 136 if (*table & _REGION_ENTRY_INVALID) 137 goto out; 138 table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN); 139 /* fallthrough */ 140 case _ASCE_TYPE_REGION2: 141 table += (address & _REGION2_INDEX) >> _REGION2_SHIFT; 142 if (bad_address(table)) 143 goto bad; 144 pr_cont("R2:%016lx ", *table); 145 if (*table & _REGION_ENTRY_INVALID) 146 goto out; 147 table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN); 148 /* fallthrough */ 149 case _ASCE_TYPE_REGION3: 150 table += (address & _REGION3_INDEX) >> _REGION3_SHIFT; 151 if (bad_address(table)) 152 goto bad; 153 pr_cont("R3:%016lx ", *table); 154 if (*table & (_REGION_ENTRY_INVALID | _REGION3_ENTRY_LARGE)) 155 goto out; 156 table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN); 157 /* fallthrough */ 158 case _ASCE_TYPE_SEGMENT: 159 table += (address & _SEGMENT_INDEX) >> _SEGMENT_SHIFT; 160 if (bad_address(table)) 161 goto bad; 162 pr_cont("S:%016lx ", *table); 163 if (*table & (_SEGMENT_ENTRY_INVALID | _SEGMENT_ENTRY_LARGE)) 164 goto out; 165 table = (unsigned long *)(*table & _SEGMENT_ENTRY_ORIGIN); 166 } 167 table += (address & _PAGE_INDEX) >> _PAGE_SHIFT; 168 if (bad_address(table)) 169 goto bad; 170 pr_cont("P:%016lx ", *table); 171 out: 172 pr_cont("\n"); 173 return; 174 bad: 175 pr_cont("BAD\n"); 176 } 177 178 static void dump_fault_info(struct pt_regs *regs) 179 { 180 unsigned long asce; 181 182 pr_alert("Failing address: %016lx TEID: %016lx\n", 183 regs->int_parm_long & __FAIL_ADDR_MASK, regs->int_parm_long); 184 pr_alert("Fault in "); 185 switch (regs->int_parm_long & 3) { 186 case 3: 187 pr_cont("home space "); 188 break; 189 case 2: 190 pr_cont("secondary space "); 191 break; 192 case 1: 193 pr_cont("access register "); 194 break; 195 case 0: 196 pr_cont("primary space "); 197 break; 198 } 199 pr_cont("mode while using "); 200 switch (get_fault_type(regs)) { 201 case USER_FAULT: 202 asce = S390_lowcore.user_asce; 203 pr_cont("user "); 204 break; 205 case VDSO_FAULT: 206 asce = S390_lowcore.vdso_asce; 207 pr_cont("vdso "); 208 break; 209 case GMAP_FAULT: 210 asce = ((struct gmap *) S390_lowcore.gmap)->asce; 211 pr_cont("gmap "); 212 break; 213 case KERNEL_FAULT: 214 asce = S390_lowcore.kernel_asce; 215 pr_cont("kernel "); 216 break; 217 default: 218 unreachable(); 219 } 220 pr_cont("ASCE.\n"); 221 dump_pagetable(asce, regs->int_parm_long & __FAIL_ADDR_MASK); 222 } 223 224 int show_unhandled_signals = 1; 225 226 void report_user_fault(struct pt_regs *regs, long signr, int is_mm_fault) 227 { 228 if ((task_pid_nr(current) > 1) && !show_unhandled_signals) 229 return; 230 if (!unhandled_signal(current, signr)) 231 return; 232 if (!printk_ratelimit()) 233 return; 234 printk(KERN_ALERT "User process fault: interruption code %04x ilc:%d ", 235 regs->int_code & 0xffff, regs->int_code >> 17); 236 print_vma_addr(KERN_CONT "in ", regs->psw.addr); 237 printk(KERN_CONT "\n"); 238 if (is_mm_fault) 239 dump_fault_info(regs); 240 show_regs(regs); 241 } 242 243 /* 244 * Send SIGSEGV to task. This is an external routine 245 * to keep the stack usage of do_page_fault small. 246 */ 247 static noinline void do_sigsegv(struct pt_regs *regs, int si_code) 248 { 249 report_user_fault(regs, SIGSEGV, 1); 250 force_sig_fault(SIGSEGV, si_code, 251 (void __user *)(regs->int_parm_long & __FAIL_ADDR_MASK), 252 current); 253 } 254 255 const struct exception_table_entry *s390_search_extables(unsigned long addr) 256 { 257 const struct exception_table_entry *fixup; 258 259 fixup = search_extable(__start_dma_ex_table, 260 __stop_dma_ex_table - __start_dma_ex_table, 261 addr); 262 if (!fixup) 263 fixup = search_exception_tables(addr); 264 return fixup; 265 } 266 267 static noinline void do_no_context(struct pt_regs *regs) 268 { 269 const struct exception_table_entry *fixup; 270 271 /* Are we prepared to handle this kernel fault? */ 272 fixup = s390_search_extables(regs->psw.addr); 273 if (fixup) { 274 regs->psw.addr = extable_fixup(fixup); 275 return; 276 } 277 278 /* 279 * Oops. The kernel tried to access some bad page. We'll have to 280 * terminate things with extreme prejudice. 281 */ 282 if (get_fault_type(regs) == KERNEL_FAULT) 283 printk(KERN_ALERT "Unable to handle kernel pointer dereference" 284 " in virtual kernel address space\n"); 285 else 286 printk(KERN_ALERT "Unable to handle kernel paging request" 287 " in virtual user address space\n"); 288 dump_fault_info(regs); 289 die(regs, "Oops"); 290 do_exit(SIGKILL); 291 } 292 293 static noinline void do_low_address(struct pt_regs *regs) 294 { 295 /* Low-address protection hit in kernel mode means 296 NULL pointer write access in kernel mode. */ 297 if (regs->psw.mask & PSW_MASK_PSTATE) { 298 /* Low-address protection hit in user mode 'cannot happen'. */ 299 die (regs, "Low-address protection"); 300 do_exit(SIGKILL); 301 } 302 303 do_no_context(regs); 304 } 305 306 static noinline void do_sigbus(struct pt_regs *regs) 307 { 308 /* 309 * Send a sigbus, regardless of whether we were in kernel 310 * or user mode. 311 */ 312 force_sig_fault(SIGBUS, BUS_ADRERR, 313 (void __user *)(regs->int_parm_long & __FAIL_ADDR_MASK), 314 current); 315 } 316 317 static noinline int signal_return(struct pt_regs *regs) 318 { 319 u16 instruction; 320 int rc; 321 322 rc = __get_user(instruction, (u16 __user *) regs->psw.addr); 323 if (rc) 324 return rc; 325 if (instruction == 0x0a77) { 326 set_pt_regs_flag(regs, PIF_SYSCALL); 327 regs->int_code = 0x00040077; 328 return 0; 329 } else if (instruction == 0x0aad) { 330 set_pt_regs_flag(regs, PIF_SYSCALL); 331 regs->int_code = 0x000400ad; 332 return 0; 333 } 334 return -EACCES; 335 } 336 337 static noinline void do_fault_error(struct pt_regs *regs, int access, 338 vm_fault_t fault) 339 { 340 int si_code; 341 342 switch (fault) { 343 case VM_FAULT_BADACCESS: 344 if (access == VM_EXEC && signal_return(regs) == 0) 345 break; 346 case VM_FAULT_BADMAP: 347 /* Bad memory access. Check if it is kernel or user space. */ 348 if (user_mode(regs)) { 349 /* User mode accesses just cause a SIGSEGV */ 350 si_code = (fault == VM_FAULT_BADMAP) ? 351 SEGV_MAPERR : SEGV_ACCERR; 352 do_sigsegv(regs, si_code); 353 break; 354 } 355 case VM_FAULT_BADCONTEXT: 356 case VM_FAULT_PFAULT: 357 do_no_context(regs); 358 break; 359 case VM_FAULT_SIGNAL: 360 if (!user_mode(regs)) 361 do_no_context(regs); 362 break; 363 default: /* fault & VM_FAULT_ERROR */ 364 if (fault & VM_FAULT_OOM) { 365 if (!user_mode(regs)) 366 do_no_context(regs); 367 else 368 pagefault_out_of_memory(); 369 } else if (fault & VM_FAULT_SIGSEGV) { 370 /* Kernel mode? Handle exceptions or die */ 371 if (!user_mode(regs)) 372 do_no_context(regs); 373 else 374 do_sigsegv(regs, SEGV_MAPERR); 375 } else if (fault & VM_FAULT_SIGBUS) { 376 /* Kernel mode? Handle exceptions or die */ 377 if (!user_mode(regs)) 378 do_no_context(regs); 379 else 380 do_sigbus(regs); 381 } else 382 BUG(); 383 break; 384 } 385 } 386 387 /* 388 * This routine handles page faults. It determines the address, 389 * and the problem, and then passes it off to one of the appropriate 390 * routines. 391 * 392 * interruption code (int_code): 393 * 04 Protection -> Write-Protection (suprression) 394 * 10 Segment translation -> Not present (nullification) 395 * 11 Page translation -> Not present (nullification) 396 * 3b Region third trans. -> Not present (nullification) 397 */ 398 static inline vm_fault_t do_exception(struct pt_regs *regs, int access) 399 { 400 struct gmap *gmap; 401 struct task_struct *tsk; 402 struct mm_struct *mm; 403 struct vm_area_struct *vma; 404 enum fault_type type; 405 unsigned long trans_exc_code; 406 unsigned long address; 407 unsigned int flags; 408 vm_fault_t fault; 409 410 tsk = current; 411 /* 412 * The instruction that caused the program check has 413 * been nullified. Don't signal single step via SIGTRAP. 414 */ 415 clear_pt_regs_flag(regs, PIF_PER_TRAP); 416 417 if (notify_page_fault(regs)) 418 return 0; 419 420 mm = tsk->mm; 421 trans_exc_code = regs->int_parm_long; 422 423 /* 424 * Verify that the fault happened in user space, that 425 * we are not in an interrupt and that there is a 426 * user context. 427 */ 428 fault = VM_FAULT_BADCONTEXT; 429 type = get_fault_type(regs); 430 switch (type) { 431 case KERNEL_FAULT: 432 goto out; 433 case VDSO_FAULT: 434 fault = VM_FAULT_BADMAP; 435 goto out; 436 case USER_FAULT: 437 case GMAP_FAULT: 438 if (faulthandler_disabled() || !mm) 439 goto out; 440 break; 441 } 442 443 address = trans_exc_code & __FAIL_ADDR_MASK; 444 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 445 flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; 446 if (user_mode(regs)) 447 flags |= FAULT_FLAG_USER; 448 if (access == VM_WRITE || (trans_exc_code & store_indication) == 0x400) 449 flags |= FAULT_FLAG_WRITE; 450 down_read(&mm->mmap_sem); 451 452 gmap = NULL; 453 if (IS_ENABLED(CONFIG_PGSTE) && type == GMAP_FAULT) { 454 gmap = (struct gmap *) S390_lowcore.gmap; 455 current->thread.gmap_addr = address; 456 current->thread.gmap_write_flag = !!(flags & FAULT_FLAG_WRITE); 457 current->thread.gmap_int_code = regs->int_code & 0xffff; 458 address = __gmap_translate(gmap, address); 459 if (address == -EFAULT) { 460 fault = VM_FAULT_BADMAP; 461 goto out_up; 462 } 463 if (gmap->pfault_enabled) 464 flags |= FAULT_FLAG_RETRY_NOWAIT; 465 } 466 467 retry: 468 fault = VM_FAULT_BADMAP; 469 vma = find_vma(mm, address); 470 if (!vma) 471 goto out_up; 472 473 if (unlikely(vma->vm_start > address)) { 474 if (!(vma->vm_flags & VM_GROWSDOWN)) 475 goto out_up; 476 if (expand_stack(vma, address)) 477 goto out_up; 478 } 479 480 /* 481 * Ok, we have a good vm_area for this memory access, so 482 * we can handle it.. 483 */ 484 fault = VM_FAULT_BADACCESS; 485 if (unlikely(!(vma->vm_flags & access))) 486 goto out_up; 487 488 if (is_vm_hugetlb_page(vma)) 489 address &= HPAGE_MASK; 490 /* 491 * If for any reason at all we couldn't handle the fault, 492 * make sure we exit gracefully rather than endlessly redo 493 * the fault. 494 */ 495 fault = handle_mm_fault(vma, address, flags); 496 /* No reason to continue if interrupted by SIGKILL. */ 497 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) { 498 fault = VM_FAULT_SIGNAL; 499 if (flags & FAULT_FLAG_RETRY_NOWAIT) 500 goto out_up; 501 goto out; 502 } 503 if (unlikely(fault & VM_FAULT_ERROR)) 504 goto out_up; 505 506 /* 507 * Major/minor page fault accounting is only done on the 508 * initial attempt. If we go through a retry, it is extremely 509 * likely that the page will be found in page cache at that point. 510 */ 511 if (flags & FAULT_FLAG_ALLOW_RETRY) { 512 if (fault & VM_FAULT_MAJOR) { 513 tsk->maj_flt++; 514 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, 515 regs, address); 516 } else { 517 tsk->min_flt++; 518 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, 519 regs, address); 520 } 521 if (fault & VM_FAULT_RETRY) { 522 if (IS_ENABLED(CONFIG_PGSTE) && gmap && 523 (flags & FAULT_FLAG_RETRY_NOWAIT)) { 524 /* FAULT_FLAG_RETRY_NOWAIT has been set, 525 * mmap_sem has not been released */ 526 current->thread.gmap_pfault = 1; 527 fault = VM_FAULT_PFAULT; 528 goto out_up; 529 } 530 /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk 531 * of starvation. */ 532 flags &= ~(FAULT_FLAG_ALLOW_RETRY | 533 FAULT_FLAG_RETRY_NOWAIT); 534 flags |= FAULT_FLAG_TRIED; 535 down_read(&mm->mmap_sem); 536 goto retry; 537 } 538 } 539 if (IS_ENABLED(CONFIG_PGSTE) && gmap) { 540 address = __gmap_link(gmap, current->thread.gmap_addr, 541 address); 542 if (address == -EFAULT) { 543 fault = VM_FAULT_BADMAP; 544 goto out_up; 545 } 546 if (address == -ENOMEM) { 547 fault = VM_FAULT_OOM; 548 goto out_up; 549 } 550 } 551 fault = 0; 552 out_up: 553 up_read(&mm->mmap_sem); 554 out: 555 return fault; 556 } 557 558 void do_protection_exception(struct pt_regs *regs) 559 { 560 unsigned long trans_exc_code; 561 int access; 562 vm_fault_t fault; 563 564 trans_exc_code = regs->int_parm_long; 565 /* 566 * Protection exceptions are suppressing, decrement psw address. 567 * The exception to this rule are aborted transactions, for these 568 * the PSW already points to the correct location. 569 */ 570 if (!(regs->int_code & 0x200)) 571 regs->psw.addr = __rewind_psw(regs->psw, regs->int_code >> 16); 572 /* 573 * Check for low-address protection. This needs to be treated 574 * as a special case because the translation exception code 575 * field is not guaranteed to contain valid data in this case. 576 */ 577 if (unlikely(!(trans_exc_code & 4))) { 578 do_low_address(regs); 579 return; 580 } 581 if (unlikely(MACHINE_HAS_NX && (trans_exc_code & 0x80))) { 582 regs->int_parm_long = (trans_exc_code & ~PAGE_MASK) | 583 (regs->psw.addr & PAGE_MASK); 584 access = VM_EXEC; 585 fault = VM_FAULT_BADACCESS; 586 } else { 587 access = VM_WRITE; 588 fault = do_exception(regs, access); 589 } 590 if (unlikely(fault)) 591 do_fault_error(regs, access, fault); 592 } 593 NOKPROBE_SYMBOL(do_protection_exception); 594 595 void do_dat_exception(struct pt_regs *regs) 596 { 597 int access; 598 vm_fault_t fault; 599 600 access = VM_READ | VM_EXEC | VM_WRITE; 601 fault = do_exception(regs, access); 602 if (unlikely(fault)) 603 do_fault_error(regs, access, fault); 604 } 605 NOKPROBE_SYMBOL(do_dat_exception); 606 607 #ifdef CONFIG_PFAULT 608 /* 609 * 'pfault' pseudo page faults routines. 610 */ 611 static int pfault_disable; 612 613 static int __init nopfault(char *str) 614 { 615 pfault_disable = 1; 616 return 1; 617 } 618 619 __setup("nopfault", nopfault); 620 621 struct pfault_refbk { 622 u16 refdiagc; 623 u16 reffcode; 624 u16 refdwlen; 625 u16 refversn; 626 u64 refgaddr; 627 u64 refselmk; 628 u64 refcmpmk; 629 u64 reserved; 630 } __attribute__ ((packed, aligned(8))); 631 632 static struct pfault_refbk pfault_init_refbk = { 633 .refdiagc = 0x258, 634 .reffcode = 0, 635 .refdwlen = 5, 636 .refversn = 2, 637 .refgaddr = __LC_LPP, 638 .refselmk = 1ULL << 48, 639 .refcmpmk = 1ULL << 48, 640 .reserved = __PF_RES_FIELD 641 }; 642 643 int pfault_init(void) 644 { 645 int rc; 646 647 if (pfault_disable) 648 return -1; 649 diag_stat_inc(DIAG_STAT_X258); 650 asm volatile( 651 " diag %1,%0,0x258\n" 652 "0: j 2f\n" 653 "1: la %0,8\n" 654 "2:\n" 655 EX_TABLE(0b,1b) 656 : "=d" (rc) 657 : "a" (&pfault_init_refbk), "m" (pfault_init_refbk) : "cc"); 658 return rc; 659 } 660 661 static struct pfault_refbk pfault_fini_refbk = { 662 .refdiagc = 0x258, 663 .reffcode = 1, 664 .refdwlen = 5, 665 .refversn = 2, 666 }; 667 668 void pfault_fini(void) 669 { 670 671 if (pfault_disable) 672 return; 673 diag_stat_inc(DIAG_STAT_X258); 674 asm volatile( 675 " diag %0,0,0x258\n" 676 "0: nopr %%r7\n" 677 EX_TABLE(0b,0b) 678 : : "a" (&pfault_fini_refbk), "m" (pfault_fini_refbk) : "cc"); 679 } 680 681 static DEFINE_SPINLOCK(pfault_lock); 682 static LIST_HEAD(pfault_list); 683 684 #define PF_COMPLETE 0x0080 685 686 /* 687 * The mechanism of our pfault code: if Linux is running as guest, runs a user 688 * space process and the user space process accesses a page that the host has 689 * paged out we get a pfault interrupt. 690 * 691 * This allows us, within the guest, to schedule a different process. Without 692 * this mechanism the host would have to suspend the whole virtual cpu until 693 * the page has been paged in. 694 * 695 * So when we get such an interrupt then we set the state of the current task 696 * to uninterruptible and also set the need_resched flag. Both happens within 697 * interrupt context(!). If we later on want to return to user space we 698 * recognize the need_resched flag and then call schedule(). It's not very 699 * obvious how this works... 700 * 701 * Of course we have a lot of additional fun with the completion interrupt (-> 702 * host signals that a page of a process has been paged in and the process can 703 * continue to run). This interrupt can arrive on any cpu and, since we have 704 * virtual cpus, actually appear before the interrupt that signals that a page 705 * is missing. 706 */ 707 static void pfault_interrupt(struct ext_code ext_code, 708 unsigned int param32, unsigned long param64) 709 { 710 struct task_struct *tsk; 711 __u16 subcode; 712 pid_t pid; 713 714 /* 715 * Get the external interruption subcode & pfault initial/completion 716 * signal bit. VM stores this in the 'cpu address' field associated 717 * with the external interrupt. 718 */ 719 subcode = ext_code.subcode; 720 if ((subcode & 0xff00) != __SUBCODE_MASK) 721 return; 722 inc_irq_stat(IRQEXT_PFL); 723 /* Get the token (= pid of the affected task). */ 724 pid = param64 & LPP_PID_MASK; 725 rcu_read_lock(); 726 tsk = find_task_by_pid_ns(pid, &init_pid_ns); 727 if (tsk) 728 get_task_struct(tsk); 729 rcu_read_unlock(); 730 if (!tsk) 731 return; 732 spin_lock(&pfault_lock); 733 if (subcode & PF_COMPLETE) { 734 /* signal bit is set -> a page has been swapped in by VM */ 735 if (tsk->thread.pfault_wait == 1) { 736 /* Initial interrupt was faster than the completion 737 * interrupt. pfault_wait is valid. Set pfault_wait 738 * back to zero and wake up the process. This can 739 * safely be done because the task is still sleeping 740 * and can't produce new pfaults. */ 741 tsk->thread.pfault_wait = 0; 742 list_del(&tsk->thread.list); 743 wake_up_process(tsk); 744 put_task_struct(tsk); 745 } else { 746 /* Completion interrupt was faster than initial 747 * interrupt. Set pfault_wait to -1 so the initial 748 * interrupt doesn't put the task to sleep. 749 * If the task is not running, ignore the completion 750 * interrupt since it must be a leftover of a PFAULT 751 * CANCEL operation which didn't remove all pending 752 * completion interrupts. */ 753 if (tsk->state == TASK_RUNNING) 754 tsk->thread.pfault_wait = -1; 755 } 756 } else { 757 /* signal bit not set -> a real page is missing. */ 758 if (WARN_ON_ONCE(tsk != current)) 759 goto out; 760 if (tsk->thread.pfault_wait == 1) { 761 /* Already on the list with a reference: put to sleep */ 762 goto block; 763 } else if (tsk->thread.pfault_wait == -1) { 764 /* Completion interrupt was faster than the initial 765 * interrupt (pfault_wait == -1). Set pfault_wait 766 * back to zero and exit. */ 767 tsk->thread.pfault_wait = 0; 768 } else { 769 /* Initial interrupt arrived before completion 770 * interrupt. Let the task sleep. 771 * An extra task reference is needed since a different 772 * cpu may set the task state to TASK_RUNNING again 773 * before the scheduler is reached. */ 774 get_task_struct(tsk); 775 tsk->thread.pfault_wait = 1; 776 list_add(&tsk->thread.list, &pfault_list); 777 block: 778 /* Since this must be a userspace fault, there 779 * is no kernel task state to trample. Rely on the 780 * return to userspace schedule() to block. */ 781 __set_current_state(TASK_UNINTERRUPTIBLE); 782 set_tsk_need_resched(tsk); 783 set_preempt_need_resched(); 784 } 785 } 786 out: 787 spin_unlock(&pfault_lock); 788 put_task_struct(tsk); 789 } 790 791 static int pfault_cpu_dead(unsigned int cpu) 792 { 793 struct thread_struct *thread, *next; 794 struct task_struct *tsk; 795 796 spin_lock_irq(&pfault_lock); 797 list_for_each_entry_safe(thread, next, &pfault_list, list) { 798 thread->pfault_wait = 0; 799 list_del(&thread->list); 800 tsk = container_of(thread, struct task_struct, thread); 801 wake_up_process(tsk); 802 put_task_struct(tsk); 803 } 804 spin_unlock_irq(&pfault_lock); 805 return 0; 806 } 807 808 static int __init pfault_irq_init(void) 809 { 810 int rc; 811 812 rc = register_external_irq(EXT_IRQ_CP_SERVICE, pfault_interrupt); 813 if (rc) 814 goto out_extint; 815 rc = pfault_init() == 0 ? 0 : -EOPNOTSUPP; 816 if (rc) 817 goto out_pfault; 818 irq_subclass_register(IRQ_SUBCLASS_SERVICE_SIGNAL); 819 cpuhp_setup_state_nocalls(CPUHP_S390_PFAULT_DEAD, "s390/pfault:dead", 820 NULL, pfault_cpu_dead); 821 return 0; 822 823 out_pfault: 824 unregister_external_irq(EXT_IRQ_CP_SERVICE, pfault_interrupt); 825 out_extint: 826 pfault_disable = 1; 827 return rc; 828 } 829 early_initcall(pfault_irq_init); 830 831 #endif /* CONFIG_PFAULT */ 832