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 /* 86 * Unlock any spinlocks which will prevent us from getting the 87 * message out. 88 */ 89 void bust_spinlocks(int yes) 90 { 91 if (yes) { 92 oops_in_progress = 1; 93 } else { 94 int loglevel_save = console_loglevel; 95 console_unblank(); 96 oops_in_progress = 0; 97 /* 98 * OK, the message is on the console. Now we call printk() 99 * without oops_in_progress set so that printk will give klogd 100 * a poke. Hold onto your hats... 101 */ 102 console_loglevel = 15; 103 printk(" "); 104 console_loglevel = loglevel_save; 105 } 106 } 107 108 /* 109 * Find out which address space caused the exception. 110 * Access register mode is impossible, ignore space == 3. 111 */ 112 static inline enum fault_type get_fault_type(struct pt_regs *regs) 113 { 114 unsigned long trans_exc_code; 115 116 trans_exc_code = regs->int_parm_long & 3; 117 if (likely(trans_exc_code == 0)) { 118 /* primary space exception */ 119 if (IS_ENABLED(CONFIG_PGSTE) && 120 test_pt_regs_flag(regs, PIF_GUEST_FAULT)) 121 return GMAP_FAULT; 122 if (current->thread.mm_segment == USER_DS) 123 return USER_FAULT; 124 return KERNEL_FAULT; 125 } 126 if (trans_exc_code == 2) { 127 /* secondary space exception */ 128 if (current->thread.mm_segment & 1) { 129 if (current->thread.mm_segment == USER_DS_SACF) 130 return USER_FAULT; 131 return KERNEL_FAULT; 132 } 133 return VDSO_FAULT; 134 } 135 /* home space exception -> access via kernel ASCE */ 136 return KERNEL_FAULT; 137 } 138 139 static int bad_address(void *p) 140 { 141 unsigned long dummy; 142 143 return probe_kernel_address((unsigned long *)p, dummy); 144 } 145 146 static void dump_pagetable(unsigned long asce, unsigned long address) 147 { 148 unsigned long *table = __va(asce & _ASCE_ORIGIN); 149 150 pr_alert("AS:%016lx ", asce); 151 switch (asce & _ASCE_TYPE_MASK) { 152 case _ASCE_TYPE_REGION1: 153 table += (address & _REGION1_INDEX) >> _REGION1_SHIFT; 154 if (bad_address(table)) 155 goto bad; 156 pr_cont("R1:%016lx ", *table); 157 if (*table & _REGION_ENTRY_INVALID) 158 goto out; 159 table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN); 160 /* fallthrough */ 161 case _ASCE_TYPE_REGION2: 162 table += (address & _REGION2_INDEX) >> _REGION2_SHIFT; 163 if (bad_address(table)) 164 goto bad; 165 pr_cont("R2:%016lx ", *table); 166 if (*table & _REGION_ENTRY_INVALID) 167 goto out; 168 table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN); 169 /* fallthrough */ 170 case _ASCE_TYPE_REGION3: 171 table += (address & _REGION3_INDEX) >> _REGION3_SHIFT; 172 if (bad_address(table)) 173 goto bad; 174 pr_cont("R3:%016lx ", *table); 175 if (*table & (_REGION_ENTRY_INVALID | _REGION3_ENTRY_LARGE)) 176 goto out; 177 table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN); 178 /* fallthrough */ 179 case _ASCE_TYPE_SEGMENT: 180 table += (address & _SEGMENT_INDEX) >> _SEGMENT_SHIFT; 181 if (bad_address(table)) 182 goto bad; 183 pr_cont("S:%016lx ", *table); 184 if (*table & (_SEGMENT_ENTRY_INVALID | _SEGMENT_ENTRY_LARGE)) 185 goto out; 186 table = (unsigned long *)(*table & _SEGMENT_ENTRY_ORIGIN); 187 } 188 table += (address & _PAGE_INDEX) >> _PAGE_SHIFT; 189 if (bad_address(table)) 190 goto bad; 191 pr_cont("P:%016lx ", *table); 192 out: 193 pr_cont("\n"); 194 return; 195 bad: 196 pr_cont("BAD\n"); 197 } 198 199 static void dump_fault_info(struct pt_regs *regs) 200 { 201 unsigned long asce; 202 203 pr_alert("Failing address: %016lx TEID: %016lx\n", 204 regs->int_parm_long & __FAIL_ADDR_MASK, regs->int_parm_long); 205 pr_alert("Fault in "); 206 switch (regs->int_parm_long & 3) { 207 case 3: 208 pr_cont("home space "); 209 break; 210 case 2: 211 pr_cont("secondary space "); 212 break; 213 case 1: 214 pr_cont("access register "); 215 break; 216 case 0: 217 pr_cont("primary space "); 218 break; 219 } 220 pr_cont("mode while using "); 221 switch (get_fault_type(regs)) { 222 case USER_FAULT: 223 asce = S390_lowcore.user_asce; 224 pr_cont("user "); 225 break; 226 case VDSO_FAULT: 227 asce = S390_lowcore.vdso_asce; 228 pr_cont("vdso "); 229 break; 230 case GMAP_FAULT: 231 asce = ((struct gmap *) S390_lowcore.gmap)->asce; 232 pr_cont("gmap "); 233 break; 234 case KERNEL_FAULT: 235 asce = S390_lowcore.kernel_asce; 236 pr_cont("kernel "); 237 break; 238 } 239 pr_cont("ASCE.\n"); 240 dump_pagetable(asce, regs->int_parm_long & __FAIL_ADDR_MASK); 241 } 242 243 int show_unhandled_signals = 1; 244 245 void report_user_fault(struct pt_regs *regs, long signr, int is_mm_fault) 246 { 247 if ((task_pid_nr(current) > 1) && !show_unhandled_signals) 248 return; 249 if (!unhandled_signal(current, signr)) 250 return; 251 if (!printk_ratelimit()) 252 return; 253 printk(KERN_ALERT "User process fault: interruption code %04x ilc:%d ", 254 regs->int_code & 0xffff, regs->int_code >> 17); 255 print_vma_addr(KERN_CONT "in ", regs->psw.addr); 256 printk(KERN_CONT "\n"); 257 if (is_mm_fault) 258 dump_fault_info(regs); 259 show_regs(regs); 260 } 261 262 /* 263 * Send SIGSEGV to task. This is an external routine 264 * to keep the stack usage of do_page_fault small. 265 */ 266 static noinline void do_sigsegv(struct pt_regs *regs, int si_code) 267 { 268 struct siginfo si; 269 270 report_user_fault(regs, SIGSEGV, 1); 271 si.si_signo = SIGSEGV; 272 si.si_errno = 0; 273 si.si_code = si_code; 274 si.si_addr = (void __user *)(regs->int_parm_long & __FAIL_ADDR_MASK); 275 force_sig_info(SIGSEGV, &si, current); 276 } 277 278 static noinline void do_no_context(struct pt_regs *regs) 279 { 280 const struct exception_table_entry *fixup; 281 282 /* Are we prepared to handle this kernel fault? */ 283 fixup = search_exception_tables(regs->psw.addr); 284 if (fixup) { 285 regs->psw.addr = extable_fixup(fixup); 286 return; 287 } 288 289 /* 290 * Oops. The kernel tried to access some bad page. We'll have to 291 * terminate things with extreme prejudice. 292 */ 293 if (get_fault_type(regs) == KERNEL_FAULT) 294 printk(KERN_ALERT "Unable to handle kernel pointer dereference" 295 " in virtual kernel address space\n"); 296 else 297 printk(KERN_ALERT "Unable to handle kernel paging request" 298 " in virtual user address space\n"); 299 dump_fault_info(regs); 300 die(regs, "Oops"); 301 do_exit(SIGKILL); 302 } 303 304 static noinline void do_low_address(struct pt_regs *regs) 305 { 306 /* Low-address protection hit in kernel mode means 307 NULL pointer write access in kernel mode. */ 308 if (regs->psw.mask & PSW_MASK_PSTATE) { 309 /* Low-address protection hit in user mode 'cannot happen'. */ 310 die (regs, "Low-address protection"); 311 do_exit(SIGKILL); 312 } 313 314 do_no_context(regs); 315 } 316 317 static noinline void do_sigbus(struct pt_regs *regs) 318 { 319 struct task_struct *tsk = current; 320 struct siginfo si; 321 322 /* 323 * Send a sigbus, regardless of whether we were in kernel 324 * or user mode. 325 */ 326 si.si_signo = SIGBUS; 327 si.si_errno = 0; 328 si.si_code = BUS_ADRERR; 329 si.si_addr = (void __user *)(regs->int_parm_long & __FAIL_ADDR_MASK); 330 force_sig_info(SIGBUS, &si, tsk); 331 } 332 333 static noinline int signal_return(struct pt_regs *regs) 334 { 335 u16 instruction; 336 int rc; 337 338 rc = __get_user(instruction, (u16 __user *) regs->psw.addr); 339 if (rc) 340 return rc; 341 if (instruction == 0x0a77) { 342 set_pt_regs_flag(regs, PIF_SYSCALL); 343 regs->int_code = 0x00040077; 344 return 0; 345 } else if (instruction == 0x0aad) { 346 set_pt_regs_flag(regs, PIF_SYSCALL); 347 regs->int_code = 0x000400ad; 348 return 0; 349 } 350 return -EACCES; 351 } 352 353 static noinline void do_fault_error(struct pt_regs *regs, int access, int fault) 354 { 355 int si_code; 356 357 switch (fault) { 358 case VM_FAULT_BADACCESS: 359 if (access == VM_EXEC && signal_return(regs) == 0) 360 break; 361 case VM_FAULT_BADMAP: 362 /* Bad memory access. Check if it is kernel or user space. */ 363 if (user_mode(regs)) { 364 /* User mode accesses just cause a SIGSEGV */ 365 si_code = (fault == VM_FAULT_BADMAP) ? 366 SEGV_MAPERR : SEGV_ACCERR; 367 do_sigsegv(regs, si_code); 368 break; 369 } 370 case VM_FAULT_BADCONTEXT: 371 case VM_FAULT_PFAULT: 372 do_no_context(regs); 373 break; 374 case VM_FAULT_SIGNAL: 375 if (!user_mode(regs)) 376 do_no_context(regs); 377 break; 378 default: /* fault & VM_FAULT_ERROR */ 379 if (fault & VM_FAULT_OOM) { 380 if (!user_mode(regs)) 381 do_no_context(regs); 382 else 383 pagefault_out_of_memory(); 384 } else if (fault & VM_FAULT_SIGSEGV) { 385 /* Kernel mode? Handle exceptions or die */ 386 if (!user_mode(regs)) 387 do_no_context(regs); 388 else 389 do_sigsegv(regs, SEGV_MAPERR); 390 } else if (fault & VM_FAULT_SIGBUS) { 391 /* Kernel mode? Handle exceptions or die */ 392 if (!user_mode(regs)) 393 do_no_context(regs); 394 else 395 do_sigbus(regs); 396 } else 397 BUG(); 398 break; 399 } 400 } 401 402 /* 403 * This routine handles page faults. It determines the address, 404 * and the problem, and then passes it off to one of the appropriate 405 * routines. 406 * 407 * interruption code (int_code): 408 * 04 Protection -> Write-Protection (suprression) 409 * 10 Segment translation -> Not present (nullification) 410 * 11 Page translation -> Not present (nullification) 411 * 3b Region third trans. -> Not present (nullification) 412 */ 413 static inline int do_exception(struct pt_regs *regs, int access) 414 { 415 struct gmap *gmap; 416 struct task_struct *tsk; 417 struct mm_struct *mm; 418 struct vm_area_struct *vma; 419 enum fault_type type; 420 unsigned long trans_exc_code; 421 unsigned long address; 422 unsigned int flags; 423 int fault; 424 425 tsk = current; 426 /* 427 * The instruction that caused the program check has 428 * been nullified. Don't signal single step via SIGTRAP. 429 */ 430 clear_pt_regs_flag(regs, PIF_PER_TRAP); 431 432 if (notify_page_fault(regs)) 433 return 0; 434 435 mm = tsk->mm; 436 trans_exc_code = regs->int_parm_long; 437 438 /* 439 * Verify that the fault happened in user space, that 440 * we are not in an interrupt and that there is a 441 * user context. 442 */ 443 fault = VM_FAULT_BADCONTEXT; 444 type = get_fault_type(regs); 445 switch (type) { 446 case KERNEL_FAULT: 447 goto out; 448 case VDSO_FAULT: 449 fault = VM_FAULT_BADMAP; 450 goto out; 451 case USER_FAULT: 452 case GMAP_FAULT: 453 if (faulthandler_disabled() || !mm) 454 goto out; 455 break; 456 } 457 458 address = trans_exc_code & __FAIL_ADDR_MASK; 459 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 460 flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; 461 if (user_mode(regs)) 462 flags |= FAULT_FLAG_USER; 463 if (access == VM_WRITE || (trans_exc_code & store_indication) == 0x400) 464 flags |= FAULT_FLAG_WRITE; 465 down_read(&mm->mmap_sem); 466 467 gmap = NULL; 468 if (IS_ENABLED(CONFIG_PGSTE) && type == GMAP_FAULT) { 469 gmap = (struct gmap *) S390_lowcore.gmap; 470 current->thread.gmap_addr = address; 471 current->thread.gmap_write_flag = !!(flags & FAULT_FLAG_WRITE); 472 current->thread.gmap_int_code = regs->int_code & 0xffff; 473 address = __gmap_translate(gmap, address); 474 if (address == -EFAULT) { 475 fault = VM_FAULT_BADMAP; 476 goto out_up; 477 } 478 if (gmap->pfault_enabled) 479 flags |= FAULT_FLAG_RETRY_NOWAIT; 480 } 481 482 retry: 483 fault = VM_FAULT_BADMAP; 484 vma = find_vma(mm, address); 485 if (!vma) 486 goto out_up; 487 488 if (unlikely(vma->vm_start > address)) { 489 if (!(vma->vm_flags & VM_GROWSDOWN)) 490 goto out_up; 491 if (expand_stack(vma, address)) 492 goto out_up; 493 } 494 495 /* 496 * Ok, we have a good vm_area for this memory access, so 497 * we can handle it.. 498 */ 499 fault = VM_FAULT_BADACCESS; 500 if (unlikely(!(vma->vm_flags & access))) 501 goto out_up; 502 503 if (is_vm_hugetlb_page(vma)) 504 address &= HPAGE_MASK; 505 /* 506 * If for any reason at all we couldn't handle the fault, 507 * make sure we exit gracefully rather than endlessly redo 508 * the fault. 509 */ 510 fault = handle_mm_fault(vma, address, flags); 511 /* No reason to continue if interrupted by SIGKILL. */ 512 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) { 513 fault = VM_FAULT_SIGNAL; 514 goto out; 515 } 516 if (unlikely(fault & VM_FAULT_ERROR)) 517 goto out_up; 518 519 /* 520 * Major/minor page fault accounting is only done on the 521 * initial attempt. If we go through a retry, it is extremely 522 * likely that the page will be found in page cache at that point. 523 */ 524 if (flags & FAULT_FLAG_ALLOW_RETRY) { 525 if (fault & VM_FAULT_MAJOR) { 526 tsk->maj_flt++; 527 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, 528 regs, address); 529 } else { 530 tsk->min_flt++; 531 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, 532 regs, address); 533 } 534 if (fault & VM_FAULT_RETRY) { 535 if (IS_ENABLED(CONFIG_PGSTE) && gmap && 536 (flags & FAULT_FLAG_RETRY_NOWAIT)) { 537 /* FAULT_FLAG_RETRY_NOWAIT has been set, 538 * mmap_sem has not been released */ 539 current->thread.gmap_pfault = 1; 540 fault = VM_FAULT_PFAULT; 541 goto out_up; 542 } 543 /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk 544 * of starvation. */ 545 flags &= ~(FAULT_FLAG_ALLOW_RETRY | 546 FAULT_FLAG_RETRY_NOWAIT); 547 flags |= FAULT_FLAG_TRIED; 548 down_read(&mm->mmap_sem); 549 goto retry; 550 } 551 } 552 if (IS_ENABLED(CONFIG_PGSTE) && gmap) { 553 address = __gmap_link(gmap, current->thread.gmap_addr, 554 address); 555 if (address == -EFAULT) { 556 fault = VM_FAULT_BADMAP; 557 goto out_up; 558 } 559 if (address == -ENOMEM) { 560 fault = VM_FAULT_OOM; 561 goto out_up; 562 } 563 } 564 fault = 0; 565 out_up: 566 up_read(&mm->mmap_sem); 567 out: 568 return fault; 569 } 570 571 void do_protection_exception(struct pt_regs *regs) 572 { 573 unsigned long trans_exc_code; 574 int access, fault; 575 576 trans_exc_code = regs->int_parm_long; 577 /* 578 * Protection exceptions are suppressing, decrement psw address. 579 * The exception to this rule are aborted transactions, for these 580 * the PSW already points to the correct location. 581 */ 582 if (!(regs->int_code & 0x200)) 583 regs->psw.addr = __rewind_psw(regs->psw, regs->int_code >> 16); 584 /* 585 * Check for low-address protection. This needs to be treated 586 * as a special case because the translation exception code 587 * field is not guaranteed to contain valid data in this case. 588 */ 589 if (unlikely(!(trans_exc_code & 4))) { 590 do_low_address(regs); 591 return; 592 } 593 if (unlikely(MACHINE_HAS_NX && (trans_exc_code & 0x80))) { 594 regs->int_parm_long = (trans_exc_code & ~PAGE_MASK) | 595 (regs->psw.addr & PAGE_MASK); 596 access = VM_EXEC; 597 fault = VM_FAULT_BADACCESS; 598 } else { 599 access = VM_WRITE; 600 fault = do_exception(regs, access); 601 } 602 if (unlikely(fault)) 603 do_fault_error(regs, access, fault); 604 } 605 NOKPROBE_SYMBOL(do_protection_exception); 606 607 void do_dat_exception(struct pt_regs *regs) 608 { 609 int access, fault; 610 611 access = VM_READ | VM_EXEC | VM_WRITE; 612 fault = do_exception(regs, access); 613 if (unlikely(fault)) 614 do_fault_error(regs, access, fault); 615 } 616 NOKPROBE_SYMBOL(do_dat_exception); 617 618 #ifdef CONFIG_PFAULT 619 /* 620 * 'pfault' pseudo page faults routines. 621 */ 622 static int pfault_disable; 623 624 static int __init nopfault(char *str) 625 { 626 pfault_disable = 1; 627 return 1; 628 } 629 630 __setup("nopfault", nopfault); 631 632 struct pfault_refbk { 633 u16 refdiagc; 634 u16 reffcode; 635 u16 refdwlen; 636 u16 refversn; 637 u64 refgaddr; 638 u64 refselmk; 639 u64 refcmpmk; 640 u64 reserved; 641 } __attribute__ ((packed, aligned(8))); 642 643 int pfault_init(void) 644 { 645 struct pfault_refbk refbk = { 646 .refdiagc = 0x258, 647 .reffcode = 0, 648 .refdwlen = 5, 649 .refversn = 2, 650 .refgaddr = __LC_LPP, 651 .refselmk = 1ULL << 48, 652 .refcmpmk = 1ULL << 48, 653 .reserved = __PF_RES_FIELD }; 654 int rc; 655 656 if (pfault_disable) 657 return -1; 658 diag_stat_inc(DIAG_STAT_X258); 659 asm volatile( 660 " diag %1,%0,0x258\n" 661 "0: j 2f\n" 662 "1: la %0,8\n" 663 "2:\n" 664 EX_TABLE(0b,1b) 665 : "=d" (rc) : "a" (&refbk), "m" (refbk) : "cc"); 666 return rc; 667 } 668 669 void pfault_fini(void) 670 { 671 struct pfault_refbk refbk = { 672 .refdiagc = 0x258, 673 .reffcode = 1, 674 .refdwlen = 5, 675 .refversn = 2, 676 }; 677 678 if (pfault_disable) 679 return; 680 diag_stat_inc(DIAG_STAT_X258); 681 asm volatile( 682 " diag %0,0,0x258\n" 683 "0: nopr %%r7\n" 684 EX_TABLE(0b,0b) 685 : : "a" (&refbk), "m" (refbk) : "cc"); 686 } 687 688 static DEFINE_SPINLOCK(pfault_lock); 689 static LIST_HEAD(pfault_list); 690 691 #define PF_COMPLETE 0x0080 692 693 /* 694 * The mechanism of our pfault code: if Linux is running as guest, runs a user 695 * space process and the user space process accesses a page that the host has 696 * paged out we get a pfault interrupt. 697 * 698 * This allows us, within the guest, to schedule a different process. Without 699 * this mechanism the host would have to suspend the whole virtual cpu until 700 * the page has been paged in. 701 * 702 * So when we get such an interrupt then we set the state of the current task 703 * to uninterruptible and also set the need_resched flag. Both happens within 704 * interrupt context(!). If we later on want to return to user space we 705 * recognize the need_resched flag and then call schedule(). It's not very 706 * obvious how this works... 707 * 708 * Of course we have a lot of additional fun with the completion interrupt (-> 709 * host signals that a page of a process has been paged in and the process can 710 * continue to run). This interrupt can arrive on any cpu and, since we have 711 * virtual cpus, actually appear before the interrupt that signals that a page 712 * is missing. 713 */ 714 static void pfault_interrupt(struct ext_code ext_code, 715 unsigned int param32, unsigned long param64) 716 { 717 struct task_struct *tsk; 718 __u16 subcode; 719 pid_t pid; 720 721 /* 722 * Get the external interruption subcode & pfault initial/completion 723 * signal bit. VM stores this in the 'cpu address' field associated 724 * with the external interrupt. 725 */ 726 subcode = ext_code.subcode; 727 if ((subcode & 0xff00) != __SUBCODE_MASK) 728 return; 729 inc_irq_stat(IRQEXT_PFL); 730 /* Get the token (= pid of the affected task). */ 731 pid = param64 & LPP_PID_MASK; 732 rcu_read_lock(); 733 tsk = find_task_by_pid_ns(pid, &init_pid_ns); 734 if (tsk) 735 get_task_struct(tsk); 736 rcu_read_unlock(); 737 if (!tsk) 738 return; 739 spin_lock(&pfault_lock); 740 if (subcode & PF_COMPLETE) { 741 /* signal bit is set -> a page has been swapped in by VM */ 742 if (tsk->thread.pfault_wait == 1) { 743 /* Initial interrupt was faster than the completion 744 * interrupt. pfault_wait is valid. Set pfault_wait 745 * back to zero and wake up the process. This can 746 * safely be done because the task is still sleeping 747 * and can't produce new pfaults. */ 748 tsk->thread.pfault_wait = 0; 749 list_del(&tsk->thread.list); 750 wake_up_process(tsk); 751 put_task_struct(tsk); 752 } else { 753 /* Completion interrupt was faster than initial 754 * interrupt. Set pfault_wait to -1 so the initial 755 * interrupt doesn't put the task to sleep. 756 * If the task is not running, ignore the completion 757 * interrupt since it must be a leftover of a PFAULT 758 * CANCEL operation which didn't remove all pending 759 * completion interrupts. */ 760 if (tsk->state == TASK_RUNNING) 761 tsk->thread.pfault_wait = -1; 762 } 763 } else { 764 /* signal bit not set -> a real page is missing. */ 765 if (WARN_ON_ONCE(tsk != current)) 766 goto out; 767 if (tsk->thread.pfault_wait == 1) { 768 /* Already on the list with a reference: put to sleep */ 769 goto block; 770 } else if (tsk->thread.pfault_wait == -1) { 771 /* Completion interrupt was faster than the initial 772 * interrupt (pfault_wait == -1). Set pfault_wait 773 * back to zero and exit. */ 774 tsk->thread.pfault_wait = 0; 775 } else { 776 /* Initial interrupt arrived before completion 777 * interrupt. Let the task sleep. 778 * An extra task reference is needed since a different 779 * cpu may set the task state to TASK_RUNNING again 780 * before the scheduler is reached. */ 781 get_task_struct(tsk); 782 tsk->thread.pfault_wait = 1; 783 list_add(&tsk->thread.list, &pfault_list); 784 block: 785 /* Since this must be a userspace fault, there 786 * is no kernel task state to trample. Rely on the 787 * return to userspace schedule() to block. */ 788 __set_current_state(TASK_UNINTERRUPTIBLE); 789 set_tsk_need_resched(tsk); 790 set_preempt_need_resched(); 791 } 792 } 793 out: 794 spin_unlock(&pfault_lock); 795 put_task_struct(tsk); 796 } 797 798 static int pfault_cpu_dead(unsigned int cpu) 799 { 800 struct thread_struct *thread, *next; 801 struct task_struct *tsk; 802 803 spin_lock_irq(&pfault_lock); 804 list_for_each_entry_safe(thread, next, &pfault_list, list) { 805 thread->pfault_wait = 0; 806 list_del(&thread->list); 807 tsk = container_of(thread, struct task_struct, thread); 808 wake_up_process(tsk); 809 put_task_struct(tsk); 810 } 811 spin_unlock_irq(&pfault_lock); 812 return 0; 813 } 814 815 static int __init pfault_irq_init(void) 816 { 817 int rc; 818 819 rc = register_external_irq(EXT_IRQ_CP_SERVICE, pfault_interrupt); 820 if (rc) 821 goto out_extint; 822 rc = pfault_init() == 0 ? 0 : -EOPNOTSUPP; 823 if (rc) 824 goto out_pfault; 825 irq_subclass_register(IRQ_SUBCLASS_SERVICE_SIGNAL); 826 cpuhp_setup_state_nocalls(CPUHP_S390_PFAULT_DEAD, "s390/pfault:dead", 827 NULL, pfault_cpu_dead); 828 return 0; 829 830 out_pfault: 831 unregister_external_irq(EXT_IRQ_CP_SERVICE, pfault_interrupt); 832 out_extint: 833 pfault_disable = 1; 834 return rc; 835 } 836 early_initcall(pfault_irq_init); 837 838 #endif /* CONFIG_PFAULT */ 839