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 <linux/kfence.h> 35 #include <asm/asm-extable.h> 36 #include <asm/asm-offsets.h> 37 #include <asm/diag.h> 38 #include <asm/gmap.h> 39 #include <asm/irq.h> 40 #include <asm/mmu_context.h> 41 #include <asm/facility.h> 42 #include <asm/uv.h> 43 #include "../kernel/entry.h" 44 45 #define __FAIL_ADDR_MASK -4096L 46 #define __SUBCODE_MASK 0x0600 47 #define __PF_RES_FIELD 0x8000000000000000ULL 48 49 /* 50 * Allocate private vm_fault_reason from top. Please make sure it won't 51 * collide with vm_fault_reason. 52 */ 53 #define VM_FAULT_BADCONTEXT ((__force vm_fault_t)0x80000000) 54 #define VM_FAULT_BADMAP ((__force vm_fault_t)0x40000000) 55 #define VM_FAULT_BADACCESS ((__force vm_fault_t)0x20000000) 56 #define VM_FAULT_SIGNAL ((__force vm_fault_t)0x10000000) 57 #define VM_FAULT_PFAULT ((__force vm_fault_t)0x8000000) 58 59 enum fault_type { 60 KERNEL_FAULT, 61 USER_FAULT, 62 GMAP_FAULT, 63 }; 64 65 static unsigned long store_indication __read_mostly; 66 67 static int __init fault_init(void) 68 { 69 if (test_facility(75)) 70 store_indication = 0xc00; 71 return 0; 72 } 73 early_initcall(fault_init); 74 75 /* 76 * Find out which address space caused the exception. 77 */ 78 static enum fault_type get_fault_type(struct pt_regs *regs) 79 { 80 unsigned long trans_exc_code; 81 82 trans_exc_code = regs->int_parm_long & 3; 83 if (likely(trans_exc_code == 0)) { 84 /* primary space exception */ 85 if (user_mode(regs)) 86 return USER_FAULT; 87 if (!IS_ENABLED(CONFIG_PGSTE)) 88 return KERNEL_FAULT; 89 if (test_pt_regs_flag(regs, PIF_GUEST_FAULT)) 90 return GMAP_FAULT; 91 return KERNEL_FAULT; 92 } 93 if (trans_exc_code == 2) 94 return USER_FAULT; 95 if (trans_exc_code == 1) { 96 /* access register mode, not used in the kernel */ 97 return USER_FAULT; 98 } 99 /* home space exception -> access via kernel ASCE */ 100 return KERNEL_FAULT; 101 } 102 103 static unsigned long get_fault_address(struct pt_regs *regs) 104 { 105 unsigned long trans_exc_code = regs->int_parm_long; 106 107 return trans_exc_code & __FAIL_ADDR_MASK; 108 } 109 110 static bool fault_is_write(struct pt_regs *regs) 111 { 112 unsigned long trans_exc_code = regs->int_parm_long; 113 114 return (trans_exc_code & store_indication) == 0x400; 115 } 116 117 static int bad_address(void *p) 118 { 119 unsigned long dummy; 120 121 return get_kernel_nofault(dummy, (unsigned long *)p); 122 } 123 124 static void dump_pagetable(unsigned long asce, unsigned long address) 125 { 126 unsigned long *table = __va(asce & _ASCE_ORIGIN); 127 128 pr_alert("AS:%016lx ", asce); 129 switch (asce & _ASCE_TYPE_MASK) { 130 case _ASCE_TYPE_REGION1: 131 table += (address & _REGION1_INDEX) >> _REGION1_SHIFT; 132 if (bad_address(table)) 133 goto bad; 134 pr_cont("R1:%016lx ", *table); 135 if (*table & _REGION_ENTRY_INVALID) 136 goto out; 137 table = __va(*table & _REGION_ENTRY_ORIGIN); 138 fallthrough; 139 case _ASCE_TYPE_REGION2: 140 table += (address & _REGION2_INDEX) >> _REGION2_SHIFT; 141 if (bad_address(table)) 142 goto bad; 143 pr_cont("R2:%016lx ", *table); 144 if (*table & _REGION_ENTRY_INVALID) 145 goto out; 146 table = __va(*table & _REGION_ENTRY_ORIGIN); 147 fallthrough; 148 case _ASCE_TYPE_REGION3: 149 table += (address & _REGION3_INDEX) >> _REGION3_SHIFT; 150 if (bad_address(table)) 151 goto bad; 152 pr_cont("R3:%016lx ", *table); 153 if (*table & (_REGION_ENTRY_INVALID | _REGION3_ENTRY_LARGE)) 154 goto out; 155 table = __va(*table & _REGION_ENTRY_ORIGIN); 156 fallthrough; 157 case _ASCE_TYPE_SEGMENT: 158 table += (address & _SEGMENT_INDEX) >> _SEGMENT_SHIFT; 159 if (bad_address(table)) 160 goto bad; 161 pr_cont("S:%016lx ", *table); 162 if (*table & (_SEGMENT_ENTRY_INVALID | _SEGMENT_ENTRY_LARGE)) 163 goto out; 164 table = __va(*table & _SEGMENT_ENTRY_ORIGIN); 165 } 166 table += (address & _PAGE_INDEX) >> _PAGE_SHIFT; 167 if (bad_address(table)) 168 goto bad; 169 pr_cont("P:%016lx ", *table); 170 out: 171 pr_cont("\n"); 172 return; 173 bad: 174 pr_cont("BAD\n"); 175 } 176 177 static void dump_fault_info(struct pt_regs *regs) 178 { 179 unsigned long asce; 180 181 pr_alert("Failing address: %016lx TEID: %016lx\n", 182 regs->int_parm_long & __FAIL_ADDR_MASK, regs->int_parm_long); 183 pr_alert("Fault in "); 184 switch (regs->int_parm_long & 3) { 185 case 3: 186 pr_cont("home space "); 187 break; 188 case 2: 189 pr_cont("secondary space "); 190 break; 191 case 1: 192 pr_cont("access register "); 193 break; 194 case 0: 195 pr_cont("primary space "); 196 break; 197 } 198 pr_cont("mode while using "); 199 switch (get_fault_type(regs)) { 200 case USER_FAULT: 201 asce = S390_lowcore.user_asce; 202 pr_cont("user "); 203 break; 204 case GMAP_FAULT: 205 asce = ((struct gmap *) S390_lowcore.gmap)->asce; 206 pr_cont("gmap "); 207 break; 208 case KERNEL_FAULT: 209 asce = S390_lowcore.kernel_asce; 210 pr_cont("kernel "); 211 break; 212 default: 213 unreachable(); 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 } 248 249 static noinline void do_no_context(struct pt_regs *regs, vm_fault_t fault) 250 { 251 enum fault_type fault_type; 252 unsigned long address; 253 bool is_write; 254 255 if (fixup_exception(regs)) 256 return; 257 fault_type = get_fault_type(regs); 258 if ((fault_type == KERNEL_FAULT) && (fault == VM_FAULT_BADCONTEXT)) { 259 address = get_fault_address(regs); 260 is_write = fault_is_write(regs); 261 if (kfence_handle_page_fault(address, is_write, regs)) 262 return; 263 } 264 /* 265 * Oops. The kernel tried to access some bad page. We'll have to 266 * terminate things with extreme prejudice. 267 */ 268 if (fault_type == KERNEL_FAULT) 269 printk(KERN_ALERT "Unable to handle kernel pointer dereference" 270 " in virtual kernel address space\n"); 271 else 272 printk(KERN_ALERT "Unable to handle kernel paging request" 273 " in virtual user address space\n"); 274 dump_fault_info(regs); 275 die(regs, "Oops"); 276 } 277 278 static noinline void do_low_address(struct pt_regs *regs) 279 { 280 /* Low-address protection hit in kernel mode means 281 NULL pointer write access in kernel mode. */ 282 if (regs->psw.mask & PSW_MASK_PSTATE) { 283 /* Low-address protection hit in user mode 'cannot happen'. */ 284 die (regs, "Low-address protection"); 285 } 286 287 do_no_context(regs, VM_FAULT_BADACCESS); 288 } 289 290 static noinline void do_sigbus(struct pt_regs *regs) 291 { 292 /* 293 * Send a sigbus, regardless of whether we were in kernel 294 * or user mode. 295 */ 296 force_sig_fault(SIGBUS, BUS_ADRERR, 297 (void __user *)(regs->int_parm_long & __FAIL_ADDR_MASK)); 298 } 299 300 static noinline void do_fault_error(struct pt_regs *regs, vm_fault_t fault) 301 { 302 int si_code; 303 304 switch (fault) { 305 case VM_FAULT_BADACCESS: 306 case VM_FAULT_BADMAP: 307 /* Bad memory access. Check if it is kernel or user space. */ 308 if (user_mode(regs)) { 309 /* User mode accesses just cause a SIGSEGV */ 310 si_code = (fault == VM_FAULT_BADMAP) ? 311 SEGV_MAPERR : SEGV_ACCERR; 312 do_sigsegv(regs, si_code); 313 break; 314 } 315 fallthrough; 316 case VM_FAULT_BADCONTEXT: 317 case VM_FAULT_PFAULT: 318 do_no_context(regs, fault); 319 break; 320 case VM_FAULT_SIGNAL: 321 if (!user_mode(regs)) 322 do_no_context(regs, fault); 323 break; 324 default: /* fault & VM_FAULT_ERROR */ 325 if (fault & VM_FAULT_OOM) { 326 if (!user_mode(regs)) 327 do_no_context(regs, fault); 328 else 329 pagefault_out_of_memory(); 330 } else if (fault & VM_FAULT_SIGSEGV) { 331 /* Kernel mode? Handle exceptions or die */ 332 if (!user_mode(regs)) 333 do_no_context(regs, fault); 334 else 335 do_sigsegv(regs, SEGV_MAPERR); 336 } else if (fault & VM_FAULT_SIGBUS) { 337 /* Kernel mode? Handle exceptions or die */ 338 if (!user_mode(regs)) 339 do_no_context(regs, fault); 340 else 341 do_sigbus(regs); 342 } else 343 BUG(); 344 break; 345 } 346 } 347 348 /* 349 * This routine handles page faults. It determines the address, 350 * and the problem, and then passes it off to one of the appropriate 351 * routines. 352 * 353 * interruption code (int_code): 354 * 04 Protection -> Write-Protection (suppression) 355 * 10 Segment translation -> Not present (nullification) 356 * 11 Page translation -> Not present (nullification) 357 * 3b Region third trans. -> Not present (nullification) 358 */ 359 static inline vm_fault_t do_exception(struct pt_regs *regs, int access) 360 { 361 struct gmap *gmap; 362 struct task_struct *tsk; 363 struct mm_struct *mm; 364 struct vm_area_struct *vma; 365 enum fault_type type; 366 unsigned long address; 367 unsigned int flags; 368 vm_fault_t fault; 369 bool is_write; 370 371 tsk = current; 372 /* 373 * The instruction that caused the program check has 374 * been nullified. Don't signal single step via SIGTRAP. 375 */ 376 clear_thread_flag(TIF_PER_TRAP); 377 378 if (kprobe_page_fault(regs, 14)) 379 return 0; 380 381 mm = tsk->mm; 382 address = get_fault_address(regs); 383 is_write = fault_is_write(regs); 384 385 /* 386 * Verify that the fault happened in user space, that 387 * we are not in an interrupt and that there is a 388 * user context. 389 */ 390 fault = VM_FAULT_BADCONTEXT; 391 type = get_fault_type(regs); 392 switch (type) { 393 case KERNEL_FAULT: 394 goto out; 395 case USER_FAULT: 396 case GMAP_FAULT: 397 if (faulthandler_disabled() || !mm) 398 goto out; 399 break; 400 } 401 402 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 403 flags = FAULT_FLAG_DEFAULT; 404 if (user_mode(regs)) 405 flags |= FAULT_FLAG_USER; 406 if (is_write) 407 access = VM_WRITE; 408 if (access == VM_WRITE) 409 flags |= FAULT_FLAG_WRITE; 410 #ifdef CONFIG_PER_VMA_LOCK 411 if (!(flags & FAULT_FLAG_USER)) 412 goto lock_mmap; 413 vma = lock_vma_under_rcu(mm, address); 414 if (!vma) 415 goto lock_mmap; 416 if (!(vma->vm_flags & access)) { 417 vma_end_read(vma); 418 goto lock_mmap; 419 } 420 fault = handle_mm_fault(vma, address, flags | FAULT_FLAG_VMA_LOCK, regs); 421 vma_end_read(vma); 422 if (!(fault & VM_FAULT_RETRY)) { 423 count_vm_vma_lock_event(VMA_LOCK_SUCCESS); 424 goto out; 425 } 426 count_vm_vma_lock_event(VMA_LOCK_RETRY); 427 /* Quick path to respond to signals */ 428 if (fault_signal_pending(fault, regs)) { 429 fault = VM_FAULT_SIGNAL; 430 goto out; 431 } 432 lock_mmap: 433 #endif /* CONFIG_PER_VMA_LOCK */ 434 mmap_read_lock(mm); 435 436 gmap = NULL; 437 if (IS_ENABLED(CONFIG_PGSTE) && type == GMAP_FAULT) { 438 gmap = (struct gmap *) S390_lowcore.gmap; 439 current->thread.gmap_addr = address; 440 current->thread.gmap_write_flag = !!(flags & FAULT_FLAG_WRITE); 441 current->thread.gmap_int_code = regs->int_code & 0xffff; 442 address = __gmap_translate(gmap, address); 443 if (address == -EFAULT) { 444 fault = VM_FAULT_BADMAP; 445 goto out_up; 446 } 447 if (gmap->pfault_enabled) 448 flags |= FAULT_FLAG_RETRY_NOWAIT; 449 } 450 451 retry: 452 fault = VM_FAULT_BADMAP; 453 vma = find_vma(mm, address); 454 if (!vma) 455 goto out_up; 456 457 if (unlikely(vma->vm_start > address)) { 458 if (!(vma->vm_flags & VM_GROWSDOWN)) 459 goto out_up; 460 if (expand_stack(vma, address)) 461 goto out_up; 462 } 463 464 /* 465 * Ok, we have a good vm_area for this memory access, so 466 * we can handle it.. 467 */ 468 fault = VM_FAULT_BADACCESS; 469 if (unlikely(!(vma->vm_flags & access))) 470 goto out_up; 471 472 /* 473 * If for any reason at all we couldn't handle the fault, 474 * make sure we exit gracefully rather than endlessly redo 475 * the fault. 476 */ 477 fault = handle_mm_fault(vma, address, flags, regs); 478 if (fault_signal_pending(fault, regs)) { 479 fault = VM_FAULT_SIGNAL; 480 if (flags & FAULT_FLAG_RETRY_NOWAIT) 481 goto out_up; 482 goto out; 483 } 484 485 /* The fault is fully completed (including releasing mmap lock) */ 486 if (fault & VM_FAULT_COMPLETED) { 487 if (gmap) { 488 mmap_read_lock(mm); 489 goto out_gmap; 490 } 491 fault = 0; 492 goto out; 493 } 494 495 if (unlikely(fault & VM_FAULT_ERROR)) 496 goto out_up; 497 498 if (fault & VM_FAULT_RETRY) { 499 if (IS_ENABLED(CONFIG_PGSTE) && gmap && 500 (flags & FAULT_FLAG_RETRY_NOWAIT)) { 501 /* 502 * FAULT_FLAG_RETRY_NOWAIT has been set, mmap_lock has 503 * not been released 504 */ 505 current->thread.gmap_pfault = 1; 506 fault = VM_FAULT_PFAULT; 507 goto out_up; 508 } 509 flags &= ~FAULT_FLAG_RETRY_NOWAIT; 510 flags |= FAULT_FLAG_TRIED; 511 mmap_read_lock(mm); 512 goto retry; 513 } 514 out_gmap: 515 if (IS_ENABLED(CONFIG_PGSTE) && gmap) { 516 address = __gmap_link(gmap, current->thread.gmap_addr, 517 address); 518 if (address == -EFAULT) { 519 fault = VM_FAULT_BADMAP; 520 goto out_up; 521 } 522 if (address == -ENOMEM) { 523 fault = VM_FAULT_OOM; 524 goto out_up; 525 } 526 } 527 fault = 0; 528 out_up: 529 mmap_read_unlock(mm); 530 out: 531 return fault; 532 } 533 534 void do_protection_exception(struct pt_regs *regs) 535 { 536 unsigned long trans_exc_code; 537 int access; 538 vm_fault_t fault; 539 540 trans_exc_code = regs->int_parm_long; 541 /* 542 * Protection exceptions are suppressing, decrement psw address. 543 * The exception to this rule are aborted transactions, for these 544 * the PSW already points to the correct location. 545 */ 546 if (!(regs->int_code & 0x200)) 547 regs->psw.addr = __rewind_psw(regs->psw, regs->int_code >> 16); 548 /* 549 * Check for low-address protection. This needs to be treated 550 * as a special case because the translation exception code 551 * field is not guaranteed to contain valid data in this case. 552 */ 553 if (unlikely(!(trans_exc_code & 4))) { 554 do_low_address(regs); 555 return; 556 } 557 if (unlikely(MACHINE_HAS_NX && (trans_exc_code & 0x80))) { 558 regs->int_parm_long = (trans_exc_code & ~PAGE_MASK) | 559 (regs->psw.addr & PAGE_MASK); 560 access = VM_EXEC; 561 fault = VM_FAULT_BADACCESS; 562 } else { 563 access = VM_WRITE; 564 fault = do_exception(regs, access); 565 } 566 if (unlikely(fault)) 567 do_fault_error(regs, fault); 568 } 569 NOKPROBE_SYMBOL(do_protection_exception); 570 571 void do_dat_exception(struct pt_regs *regs) 572 { 573 int access; 574 vm_fault_t fault; 575 576 access = VM_ACCESS_FLAGS; 577 fault = do_exception(regs, access); 578 if (unlikely(fault)) 579 do_fault_error(regs, fault); 580 } 581 NOKPROBE_SYMBOL(do_dat_exception); 582 583 #ifdef CONFIG_PFAULT 584 /* 585 * 'pfault' pseudo page faults routines. 586 */ 587 static int pfault_disable; 588 589 static int __init nopfault(char *str) 590 { 591 pfault_disable = 1; 592 return 1; 593 } 594 595 __setup("nopfault", nopfault); 596 597 struct pfault_refbk { 598 u16 refdiagc; 599 u16 reffcode; 600 u16 refdwlen; 601 u16 refversn; 602 u64 refgaddr; 603 u64 refselmk; 604 u64 refcmpmk; 605 u64 reserved; 606 } __attribute__ ((packed, aligned(8))); 607 608 static struct pfault_refbk pfault_init_refbk = { 609 .refdiagc = 0x258, 610 .reffcode = 0, 611 .refdwlen = 5, 612 .refversn = 2, 613 .refgaddr = __LC_LPP, 614 .refselmk = 1ULL << 48, 615 .refcmpmk = 1ULL << 48, 616 .reserved = __PF_RES_FIELD 617 }; 618 619 int pfault_init(void) 620 { 621 int rc; 622 623 if (pfault_disable) 624 return -1; 625 diag_stat_inc(DIAG_STAT_X258); 626 asm volatile( 627 " diag %1,%0,0x258\n" 628 "0: j 2f\n" 629 "1: la %0,8\n" 630 "2:\n" 631 EX_TABLE(0b,1b) 632 : "=d" (rc) 633 : "a" (&pfault_init_refbk), "m" (pfault_init_refbk) : "cc"); 634 return rc; 635 } 636 637 static struct pfault_refbk pfault_fini_refbk = { 638 .refdiagc = 0x258, 639 .reffcode = 1, 640 .refdwlen = 5, 641 .refversn = 2, 642 }; 643 644 void pfault_fini(void) 645 { 646 647 if (pfault_disable) 648 return; 649 diag_stat_inc(DIAG_STAT_X258); 650 asm volatile( 651 " diag %0,0,0x258\n" 652 "0: nopr %%r7\n" 653 EX_TABLE(0b,0b) 654 : : "a" (&pfault_fini_refbk), "m" (pfault_fini_refbk) : "cc"); 655 } 656 657 static DEFINE_SPINLOCK(pfault_lock); 658 static LIST_HEAD(pfault_list); 659 660 #define PF_COMPLETE 0x0080 661 662 /* 663 * The mechanism of our pfault code: if Linux is running as guest, runs a user 664 * space process and the user space process accesses a page that the host has 665 * paged out we get a pfault interrupt. 666 * 667 * This allows us, within the guest, to schedule a different process. Without 668 * this mechanism the host would have to suspend the whole virtual cpu until 669 * the page has been paged in. 670 * 671 * So when we get such an interrupt then we set the state of the current task 672 * to uninterruptible and also set the need_resched flag. Both happens within 673 * interrupt context(!). If we later on want to return to user space we 674 * recognize the need_resched flag and then call schedule(). It's not very 675 * obvious how this works... 676 * 677 * Of course we have a lot of additional fun with the completion interrupt (-> 678 * host signals that a page of a process has been paged in and the process can 679 * continue to run). This interrupt can arrive on any cpu and, since we have 680 * virtual cpus, actually appear before the interrupt that signals that a page 681 * is missing. 682 */ 683 static void pfault_interrupt(struct ext_code ext_code, 684 unsigned int param32, unsigned long param64) 685 { 686 struct task_struct *tsk; 687 __u16 subcode; 688 pid_t pid; 689 690 /* 691 * Get the external interruption subcode & pfault initial/completion 692 * signal bit. VM stores this in the 'cpu address' field associated 693 * with the external interrupt. 694 */ 695 subcode = ext_code.subcode; 696 if ((subcode & 0xff00) != __SUBCODE_MASK) 697 return; 698 inc_irq_stat(IRQEXT_PFL); 699 /* Get the token (= pid of the affected task). */ 700 pid = param64 & LPP_PID_MASK; 701 rcu_read_lock(); 702 tsk = find_task_by_pid_ns(pid, &init_pid_ns); 703 if (tsk) 704 get_task_struct(tsk); 705 rcu_read_unlock(); 706 if (!tsk) 707 return; 708 spin_lock(&pfault_lock); 709 if (subcode & PF_COMPLETE) { 710 /* signal bit is set -> a page has been swapped in by VM */ 711 if (tsk->thread.pfault_wait == 1) { 712 /* Initial interrupt was faster than the completion 713 * interrupt. pfault_wait is valid. Set pfault_wait 714 * back to zero and wake up the process. This can 715 * safely be done because the task is still sleeping 716 * and can't produce new pfaults. */ 717 tsk->thread.pfault_wait = 0; 718 list_del(&tsk->thread.list); 719 wake_up_process(tsk); 720 put_task_struct(tsk); 721 } else { 722 /* Completion interrupt was faster than initial 723 * interrupt. Set pfault_wait to -1 so the initial 724 * interrupt doesn't put the task to sleep. 725 * If the task is not running, ignore the completion 726 * interrupt since it must be a leftover of a PFAULT 727 * CANCEL operation which didn't remove all pending 728 * completion interrupts. */ 729 if (task_is_running(tsk)) 730 tsk->thread.pfault_wait = -1; 731 } 732 } else { 733 /* signal bit not set -> a real page is missing. */ 734 if (WARN_ON_ONCE(tsk != current)) 735 goto out; 736 if (tsk->thread.pfault_wait == 1) { 737 /* Already on the list with a reference: put to sleep */ 738 goto block; 739 } else if (tsk->thread.pfault_wait == -1) { 740 /* Completion interrupt was faster than the initial 741 * interrupt (pfault_wait == -1). Set pfault_wait 742 * back to zero and exit. */ 743 tsk->thread.pfault_wait = 0; 744 } else { 745 /* Initial interrupt arrived before completion 746 * interrupt. Let the task sleep. 747 * An extra task reference is needed since a different 748 * cpu may set the task state to TASK_RUNNING again 749 * before the scheduler is reached. */ 750 get_task_struct(tsk); 751 tsk->thread.pfault_wait = 1; 752 list_add(&tsk->thread.list, &pfault_list); 753 block: 754 /* Since this must be a userspace fault, there 755 * is no kernel task state to trample. Rely on the 756 * return to userspace schedule() to block. */ 757 __set_current_state(TASK_UNINTERRUPTIBLE); 758 set_tsk_need_resched(tsk); 759 set_preempt_need_resched(); 760 } 761 } 762 out: 763 spin_unlock(&pfault_lock); 764 put_task_struct(tsk); 765 } 766 767 static int pfault_cpu_dead(unsigned int cpu) 768 { 769 struct thread_struct *thread, *next; 770 struct task_struct *tsk; 771 772 spin_lock_irq(&pfault_lock); 773 list_for_each_entry_safe(thread, next, &pfault_list, list) { 774 thread->pfault_wait = 0; 775 list_del(&thread->list); 776 tsk = container_of(thread, struct task_struct, thread); 777 wake_up_process(tsk); 778 put_task_struct(tsk); 779 } 780 spin_unlock_irq(&pfault_lock); 781 return 0; 782 } 783 784 static int __init pfault_irq_init(void) 785 { 786 int rc; 787 788 rc = register_external_irq(EXT_IRQ_CP_SERVICE, pfault_interrupt); 789 if (rc) 790 goto out_extint; 791 rc = pfault_init() == 0 ? 0 : -EOPNOTSUPP; 792 if (rc) 793 goto out_pfault; 794 irq_subclass_register(IRQ_SUBCLASS_SERVICE_SIGNAL); 795 cpuhp_setup_state_nocalls(CPUHP_S390_PFAULT_DEAD, "s390/pfault:dead", 796 NULL, pfault_cpu_dead); 797 return 0; 798 799 out_pfault: 800 unregister_external_irq(EXT_IRQ_CP_SERVICE, pfault_interrupt); 801 out_extint: 802 pfault_disable = 1; 803 return rc; 804 } 805 early_initcall(pfault_irq_init); 806 807 #endif /* CONFIG_PFAULT */ 808 809 #if IS_ENABLED(CONFIG_PGSTE) 810 811 void do_secure_storage_access(struct pt_regs *regs) 812 { 813 unsigned long addr = regs->int_parm_long & __FAIL_ADDR_MASK; 814 struct vm_area_struct *vma; 815 struct mm_struct *mm; 816 struct page *page; 817 struct gmap *gmap; 818 int rc; 819 820 /* 821 * bit 61 tells us if the address is valid, if it's not we 822 * have a major problem and should stop the kernel or send a 823 * SIGSEGV to the process. Unfortunately bit 61 is not 824 * reliable without the misc UV feature so we need to check 825 * for that as well. 826 */ 827 if (test_bit_inv(BIT_UV_FEAT_MISC, &uv_info.uv_feature_indications) && 828 !test_bit_inv(61, ®s->int_parm_long)) { 829 /* 830 * When this happens, userspace did something that it 831 * was not supposed to do, e.g. branching into secure 832 * memory. Trigger a segmentation fault. 833 */ 834 if (user_mode(regs)) { 835 send_sig(SIGSEGV, current, 0); 836 return; 837 } 838 839 /* 840 * The kernel should never run into this case and we 841 * have no way out of this situation. 842 */ 843 panic("Unexpected PGM 0x3d with TEID bit 61=0"); 844 } 845 846 switch (get_fault_type(regs)) { 847 case GMAP_FAULT: 848 mm = current->mm; 849 gmap = (struct gmap *)S390_lowcore.gmap; 850 mmap_read_lock(mm); 851 addr = __gmap_translate(gmap, addr); 852 mmap_read_unlock(mm); 853 if (IS_ERR_VALUE(addr)) { 854 do_fault_error(regs, VM_FAULT_BADMAP); 855 break; 856 } 857 fallthrough; 858 case USER_FAULT: 859 mm = current->mm; 860 mmap_read_lock(mm); 861 vma = find_vma(mm, addr); 862 if (!vma) { 863 mmap_read_unlock(mm); 864 do_fault_error(regs, VM_FAULT_BADMAP); 865 break; 866 } 867 page = follow_page(vma, addr, FOLL_WRITE | FOLL_GET); 868 if (IS_ERR_OR_NULL(page)) { 869 mmap_read_unlock(mm); 870 break; 871 } 872 if (arch_make_page_accessible(page)) 873 send_sig(SIGSEGV, current, 0); 874 put_page(page); 875 mmap_read_unlock(mm); 876 break; 877 case KERNEL_FAULT: 878 page = phys_to_page(addr); 879 if (unlikely(!try_get_page(page))) 880 break; 881 rc = arch_make_page_accessible(page); 882 put_page(page); 883 if (rc) 884 BUG(); 885 break; 886 default: 887 do_fault_error(regs, VM_FAULT_BADMAP); 888 WARN_ON_ONCE(1); 889 } 890 } 891 NOKPROBE_SYMBOL(do_secure_storage_access); 892 893 void do_non_secure_storage_access(struct pt_regs *regs) 894 { 895 unsigned long gaddr = regs->int_parm_long & __FAIL_ADDR_MASK; 896 struct gmap *gmap = (struct gmap *)S390_lowcore.gmap; 897 898 if (get_fault_type(regs) != GMAP_FAULT) { 899 do_fault_error(regs, VM_FAULT_BADMAP); 900 WARN_ON_ONCE(1); 901 return; 902 } 903 904 if (gmap_convert_to_secure(gmap, gaddr) == -EINVAL) 905 send_sig(SIGSEGV, current, 0); 906 } 907 NOKPROBE_SYMBOL(do_non_secure_storage_access); 908 909 void do_secure_storage_violation(struct pt_regs *regs) 910 { 911 unsigned long gaddr = regs->int_parm_long & __FAIL_ADDR_MASK; 912 struct gmap *gmap = (struct gmap *)S390_lowcore.gmap; 913 914 /* 915 * If the VM has been rebooted, its address space might still contain 916 * secure pages from the previous boot. 917 * Clear the page so it can be reused. 918 */ 919 if (!gmap_destroy_page(gmap, gaddr)) 920 return; 921 /* 922 * Either KVM messed up the secure guest mapping or the same 923 * page is mapped into multiple secure guests. 924 * 925 * This exception is only triggered when a guest 2 is running 926 * and can therefore never occur in kernel context. 927 */ 928 printk_ratelimited(KERN_WARNING 929 "Secure storage violation in task: %s, pid %d\n", 930 current->comm, current->pid); 931 send_sig(SIGSEGV, current, 0); 932 } 933 934 #endif /* CONFIG_PGSTE */ 935