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 } 253 254 const struct exception_table_entry *s390_search_extables(unsigned long addr) 255 { 256 const struct exception_table_entry *fixup; 257 258 fixup = search_extable(__start_dma_ex_table, 259 __stop_dma_ex_table - __start_dma_ex_table, 260 addr); 261 if (!fixup) 262 fixup = search_exception_tables(addr); 263 return fixup; 264 } 265 266 static noinline void do_no_context(struct pt_regs *regs) 267 { 268 const struct exception_table_entry *fixup; 269 270 /* Are we prepared to handle this kernel fault? */ 271 fixup = s390_search_extables(regs->psw.addr); 272 if (fixup) { 273 regs->psw.addr = extable_fixup(fixup); 274 return; 275 } 276 277 /* 278 * Oops. The kernel tried to access some bad page. We'll have to 279 * terminate things with extreme prejudice. 280 */ 281 if (get_fault_type(regs) == KERNEL_FAULT) 282 printk(KERN_ALERT "Unable to handle kernel pointer dereference" 283 " in virtual kernel address space\n"); 284 else 285 printk(KERN_ALERT "Unable to handle kernel paging request" 286 " in virtual user address space\n"); 287 dump_fault_info(regs); 288 die(regs, "Oops"); 289 do_exit(SIGKILL); 290 } 291 292 static noinline void do_low_address(struct pt_regs *regs) 293 { 294 /* Low-address protection hit in kernel mode means 295 NULL pointer write access in kernel mode. */ 296 if (regs->psw.mask & PSW_MASK_PSTATE) { 297 /* Low-address protection hit in user mode 'cannot happen'. */ 298 die (regs, "Low-address protection"); 299 do_exit(SIGKILL); 300 } 301 302 do_no_context(regs); 303 } 304 305 static noinline void do_sigbus(struct pt_regs *regs) 306 { 307 /* 308 * Send a sigbus, regardless of whether we were in kernel 309 * or user mode. 310 */ 311 force_sig_fault(SIGBUS, BUS_ADRERR, 312 (void __user *)(regs->int_parm_long & __FAIL_ADDR_MASK)); 313 } 314 315 static noinline int signal_return(struct pt_regs *regs) 316 { 317 u16 instruction; 318 int rc; 319 320 rc = __get_user(instruction, (u16 __user *) regs->psw.addr); 321 if (rc) 322 return rc; 323 if (instruction == 0x0a77) { 324 set_pt_regs_flag(regs, PIF_SYSCALL); 325 regs->int_code = 0x00040077; 326 return 0; 327 } else if (instruction == 0x0aad) { 328 set_pt_regs_flag(regs, PIF_SYSCALL); 329 regs->int_code = 0x000400ad; 330 return 0; 331 } 332 return -EACCES; 333 } 334 335 static noinline void do_fault_error(struct pt_regs *regs, int access, 336 vm_fault_t 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 vm_fault_t do_exception(struct pt_regs *regs, int access) 397 { 398 struct gmap *gmap; 399 struct task_struct *tsk; 400 struct mm_struct *mm; 401 struct vm_area_struct *vma; 402 enum fault_type type; 403 unsigned long trans_exc_code; 404 unsigned long address; 405 unsigned int flags; 406 vm_fault_t fault; 407 408 tsk = current; 409 /* 410 * The instruction that caused the program check has 411 * been nullified. Don't signal single step via SIGTRAP. 412 */ 413 clear_pt_regs_flag(regs, PIF_PER_TRAP); 414 415 if (notify_page_fault(regs)) 416 return 0; 417 418 mm = tsk->mm; 419 trans_exc_code = regs->int_parm_long; 420 421 /* 422 * Verify that the fault happened in user space, that 423 * we are not in an interrupt and that there is a 424 * user context. 425 */ 426 fault = VM_FAULT_BADCONTEXT; 427 type = get_fault_type(regs); 428 switch (type) { 429 case KERNEL_FAULT: 430 goto out; 431 case VDSO_FAULT: 432 fault = VM_FAULT_BADMAP; 433 goto out; 434 case USER_FAULT: 435 case GMAP_FAULT: 436 if (faulthandler_disabled() || !mm) 437 goto out; 438 break; 439 } 440 441 address = trans_exc_code & __FAIL_ADDR_MASK; 442 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 443 flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; 444 if (user_mode(regs)) 445 flags |= FAULT_FLAG_USER; 446 if (access == VM_WRITE || (trans_exc_code & store_indication) == 0x400) 447 flags |= FAULT_FLAG_WRITE; 448 down_read(&mm->mmap_sem); 449 450 gmap = NULL; 451 if (IS_ENABLED(CONFIG_PGSTE) && type == GMAP_FAULT) { 452 gmap = (struct gmap *) S390_lowcore.gmap; 453 current->thread.gmap_addr = address; 454 current->thread.gmap_write_flag = !!(flags & FAULT_FLAG_WRITE); 455 current->thread.gmap_int_code = regs->int_code & 0xffff; 456 address = __gmap_translate(gmap, address); 457 if (address == -EFAULT) { 458 fault = VM_FAULT_BADMAP; 459 goto out_up; 460 } 461 if (gmap->pfault_enabled) 462 flags |= FAULT_FLAG_RETRY_NOWAIT; 463 } 464 465 retry: 466 fault = VM_FAULT_BADMAP; 467 vma = find_vma(mm, address); 468 if (!vma) 469 goto out_up; 470 471 if (unlikely(vma->vm_start > address)) { 472 if (!(vma->vm_flags & VM_GROWSDOWN)) 473 goto out_up; 474 if (expand_stack(vma, address)) 475 goto out_up; 476 } 477 478 /* 479 * Ok, we have a good vm_area for this memory access, so 480 * we can handle it.. 481 */ 482 fault = VM_FAULT_BADACCESS; 483 if (unlikely(!(vma->vm_flags & access))) 484 goto out_up; 485 486 if (is_vm_hugetlb_page(vma)) 487 address &= HPAGE_MASK; 488 /* 489 * If for any reason at all we couldn't handle the fault, 490 * make sure we exit gracefully rather than endlessly redo 491 * the fault. 492 */ 493 fault = handle_mm_fault(vma, address, flags); 494 /* No reason to continue if interrupted by SIGKILL. */ 495 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) { 496 fault = VM_FAULT_SIGNAL; 497 if (flags & FAULT_FLAG_RETRY_NOWAIT) 498 goto out_up; 499 goto out; 500 } 501 if (unlikely(fault & VM_FAULT_ERROR)) 502 goto out_up; 503 504 /* 505 * Major/minor page fault accounting is only done on the 506 * initial attempt. If we go through a retry, it is extremely 507 * likely that the page will be found in page cache at that point. 508 */ 509 if (flags & FAULT_FLAG_ALLOW_RETRY) { 510 if (fault & VM_FAULT_MAJOR) { 511 tsk->maj_flt++; 512 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, 513 regs, address); 514 } else { 515 tsk->min_flt++; 516 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, 517 regs, address); 518 } 519 if (fault & VM_FAULT_RETRY) { 520 if (IS_ENABLED(CONFIG_PGSTE) && gmap && 521 (flags & FAULT_FLAG_RETRY_NOWAIT)) { 522 /* FAULT_FLAG_RETRY_NOWAIT has been set, 523 * mmap_sem has not been released */ 524 current->thread.gmap_pfault = 1; 525 fault = VM_FAULT_PFAULT; 526 goto out_up; 527 } 528 /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk 529 * of starvation. */ 530 flags &= ~(FAULT_FLAG_ALLOW_RETRY | 531 FAULT_FLAG_RETRY_NOWAIT); 532 flags |= FAULT_FLAG_TRIED; 533 down_read(&mm->mmap_sem); 534 goto retry; 535 } 536 } 537 if (IS_ENABLED(CONFIG_PGSTE) && gmap) { 538 address = __gmap_link(gmap, current->thread.gmap_addr, 539 address); 540 if (address == -EFAULT) { 541 fault = VM_FAULT_BADMAP; 542 goto out_up; 543 } 544 if (address == -ENOMEM) { 545 fault = VM_FAULT_OOM; 546 goto out_up; 547 } 548 } 549 fault = 0; 550 out_up: 551 up_read(&mm->mmap_sem); 552 out: 553 return fault; 554 } 555 556 void do_protection_exception(struct pt_regs *regs) 557 { 558 unsigned long trans_exc_code; 559 int access; 560 vm_fault_t fault; 561 562 trans_exc_code = regs->int_parm_long; 563 /* 564 * Protection exceptions are suppressing, decrement psw address. 565 * The exception to this rule are aborted transactions, for these 566 * the PSW already points to the correct location. 567 */ 568 if (!(regs->int_code & 0x200)) 569 regs->psw.addr = __rewind_psw(regs->psw, regs->int_code >> 16); 570 /* 571 * Check for low-address protection. This needs to be treated 572 * as a special case because the translation exception code 573 * field is not guaranteed to contain valid data in this case. 574 */ 575 if (unlikely(!(trans_exc_code & 4))) { 576 do_low_address(regs); 577 return; 578 } 579 if (unlikely(MACHINE_HAS_NX && (trans_exc_code & 0x80))) { 580 regs->int_parm_long = (trans_exc_code & ~PAGE_MASK) | 581 (regs->psw.addr & PAGE_MASK); 582 access = VM_EXEC; 583 fault = VM_FAULT_BADACCESS; 584 } else { 585 access = VM_WRITE; 586 fault = do_exception(regs, access); 587 } 588 if (unlikely(fault)) 589 do_fault_error(regs, access, fault); 590 } 591 NOKPROBE_SYMBOL(do_protection_exception); 592 593 void do_dat_exception(struct pt_regs *regs) 594 { 595 int access; 596 vm_fault_t fault; 597 598 access = VM_READ | VM_EXEC | VM_WRITE; 599 fault = do_exception(regs, access); 600 if (unlikely(fault)) 601 do_fault_error(regs, access, fault); 602 } 603 NOKPROBE_SYMBOL(do_dat_exception); 604 605 #ifdef CONFIG_PFAULT 606 /* 607 * 'pfault' pseudo page faults routines. 608 */ 609 static int pfault_disable; 610 611 static int __init nopfault(char *str) 612 { 613 pfault_disable = 1; 614 return 1; 615 } 616 617 __setup("nopfault", nopfault); 618 619 struct pfault_refbk { 620 u16 refdiagc; 621 u16 reffcode; 622 u16 refdwlen; 623 u16 refversn; 624 u64 refgaddr; 625 u64 refselmk; 626 u64 refcmpmk; 627 u64 reserved; 628 } __attribute__ ((packed, aligned(8))); 629 630 static struct pfault_refbk pfault_init_refbk = { 631 .refdiagc = 0x258, 632 .reffcode = 0, 633 .refdwlen = 5, 634 .refversn = 2, 635 .refgaddr = __LC_LPP, 636 .refselmk = 1ULL << 48, 637 .refcmpmk = 1ULL << 48, 638 .reserved = __PF_RES_FIELD 639 }; 640 641 int pfault_init(void) 642 { 643 int rc; 644 645 if (pfault_disable) 646 return -1; 647 diag_stat_inc(DIAG_STAT_X258); 648 asm volatile( 649 " diag %1,%0,0x258\n" 650 "0: j 2f\n" 651 "1: la %0,8\n" 652 "2:\n" 653 EX_TABLE(0b,1b) 654 : "=d" (rc) 655 : "a" (&pfault_init_refbk), "m" (pfault_init_refbk) : "cc"); 656 return rc; 657 } 658 659 static struct pfault_refbk pfault_fini_refbk = { 660 .refdiagc = 0x258, 661 .reffcode = 1, 662 .refdwlen = 5, 663 .refversn = 2, 664 }; 665 666 void pfault_fini(void) 667 { 668 669 if (pfault_disable) 670 return; 671 diag_stat_inc(DIAG_STAT_X258); 672 asm volatile( 673 " diag %0,0,0x258\n" 674 "0: nopr %%r7\n" 675 EX_TABLE(0b,0b) 676 : : "a" (&pfault_fini_refbk), "m" (pfault_fini_refbk) : "cc"); 677 } 678 679 static DEFINE_SPINLOCK(pfault_lock); 680 static LIST_HEAD(pfault_list); 681 682 #define PF_COMPLETE 0x0080 683 684 /* 685 * The mechanism of our pfault code: if Linux is running as guest, runs a user 686 * space process and the user space process accesses a page that the host has 687 * paged out we get a pfault interrupt. 688 * 689 * This allows us, within the guest, to schedule a different process. Without 690 * this mechanism the host would have to suspend the whole virtual cpu until 691 * the page has been paged in. 692 * 693 * So when we get such an interrupt then we set the state of the current task 694 * to uninterruptible and also set the need_resched flag. Both happens within 695 * interrupt context(!). If we later on want to return to user space we 696 * recognize the need_resched flag and then call schedule(). It's not very 697 * obvious how this works... 698 * 699 * Of course we have a lot of additional fun with the completion interrupt (-> 700 * host signals that a page of a process has been paged in and the process can 701 * continue to run). This interrupt can arrive on any cpu and, since we have 702 * virtual cpus, actually appear before the interrupt that signals that a page 703 * is missing. 704 */ 705 static void pfault_interrupt(struct ext_code ext_code, 706 unsigned int param32, unsigned long param64) 707 { 708 struct task_struct *tsk; 709 __u16 subcode; 710 pid_t pid; 711 712 /* 713 * Get the external interruption subcode & pfault initial/completion 714 * signal bit. VM stores this in the 'cpu address' field associated 715 * with the external interrupt. 716 */ 717 subcode = ext_code.subcode; 718 if ((subcode & 0xff00) != __SUBCODE_MASK) 719 return; 720 inc_irq_stat(IRQEXT_PFL); 721 /* Get the token (= pid of the affected task). */ 722 pid = param64 & LPP_PID_MASK; 723 rcu_read_lock(); 724 tsk = find_task_by_pid_ns(pid, &init_pid_ns); 725 if (tsk) 726 get_task_struct(tsk); 727 rcu_read_unlock(); 728 if (!tsk) 729 return; 730 spin_lock(&pfault_lock); 731 if (subcode & PF_COMPLETE) { 732 /* signal bit is set -> a page has been swapped in by VM */ 733 if (tsk->thread.pfault_wait == 1) { 734 /* Initial interrupt was faster than the completion 735 * interrupt. pfault_wait is valid. Set pfault_wait 736 * back to zero and wake up the process. This can 737 * safely be done because the task is still sleeping 738 * and can't produce new pfaults. */ 739 tsk->thread.pfault_wait = 0; 740 list_del(&tsk->thread.list); 741 wake_up_process(tsk); 742 put_task_struct(tsk); 743 } else { 744 /* Completion interrupt was faster than initial 745 * interrupt. Set pfault_wait to -1 so the initial 746 * interrupt doesn't put the task to sleep. 747 * If the task is not running, ignore the completion 748 * interrupt since it must be a leftover of a PFAULT 749 * CANCEL operation which didn't remove all pending 750 * completion interrupts. */ 751 if (tsk->state == TASK_RUNNING) 752 tsk->thread.pfault_wait = -1; 753 } 754 } else { 755 /* signal bit not set -> a real page is missing. */ 756 if (WARN_ON_ONCE(tsk != current)) 757 goto out; 758 if (tsk->thread.pfault_wait == 1) { 759 /* Already on the list with a reference: put to sleep */ 760 goto block; 761 } else if (tsk->thread.pfault_wait == -1) { 762 /* Completion interrupt was faster than the initial 763 * interrupt (pfault_wait == -1). Set pfault_wait 764 * back to zero and exit. */ 765 tsk->thread.pfault_wait = 0; 766 } else { 767 /* Initial interrupt arrived before completion 768 * interrupt. Let the task sleep. 769 * An extra task reference is needed since a different 770 * cpu may set the task state to TASK_RUNNING again 771 * before the scheduler is reached. */ 772 get_task_struct(tsk); 773 tsk->thread.pfault_wait = 1; 774 list_add(&tsk->thread.list, &pfault_list); 775 block: 776 /* Since this must be a userspace fault, there 777 * is no kernel task state to trample. Rely on the 778 * return to userspace schedule() to block. */ 779 __set_current_state(TASK_UNINTERRUPTIBLE); 780 set_tsk_need_resched(tsk); 781 set_preempt_need_resched(); 782 } 783 } 784 out: 785 spin_unlock(&pfault_lock); 786 put_task_struct(tsk); 787 } 788 789 static int pfault_cpu_dead(unsigned int cpu) 790 { 791 struct thread_struct *thread, *next; 792 struct task_struct *tsk; 793 794 spin_lock_irq(&pfault_lock); 795 list_for_each_entry_safe(thread, next, &pfault_list, list) { 796 thread->pfault_wait = 0; 797 list_del(&thread->list); 798 tsk = container_of(thread, struct task_struct, thread); 799 wake_up_process(tsk); 800 put_task_struct(tsk); 801 } 802 spin_unlock_irq(&pfault_lock); 803 return 0; 804 } 805 806 static int __init pfault_irq_init(void) 807 { 808 int rc; 809 810 rc = register_external_irq(EXT_IRQ_CP_SERVICE, pfault_interrupt); 811 if (rc) 812 goto out_extint; 813 rc = pfault_init() == 0 ? 0 : -EOPNOTSUPP; 814 if (rc) 815 goto out_pfault; 816 irq_subclass_register(IRQ_SUBCLASS_SERVICE_SIGNAL); 817 cpuhp_setup_state_nocalls(CPUHP_S390_PFAULT_DEAD, "s390/pfault:dead", 818 NULL, pfault_cpu_dead); 819 return 0; 820 821 out_pfault: 822 unregister_external_irq(EXT_IRQ_CP_SERVICE, pfault_interrupt); 823 out_extint: 824 pfault_disable = 1; 825 return rc; 826 } 827 early_initcall(pfault_irq_init); 828 829 #endif /* CONFIG_PFAULT */ 830