1 /* 2 * S390 version 3 * Copyright IBM Corp. 1999 4 * Author(s): Hartmut Penner (hp@de.ibm.com) 5 * Ulrich Weigand (uweigand@de.ibm.com) 6 * 7 * Derived from "arch/i386/mm/fault.c" 8 * Copyright (C) 1995 Linus Torvalds 9 */ 10 11 #include <linux/kernel_stat.h> 12 #include <linux/perf_event.h> 13 #include <linux/signal.h> 14 #include <linux/sched.h> 15 #include <linux/kernel.h> 16 #include <linux/errno.h> 17 #include <linux/string.h> 18 #include <linux/types.h> 19 #include <linux/ptrace.h> 20 #include <linux/mman.h> 21 #include <linux/mm.h> 22 #include <linux/compat.h> 23 #include <linux/smp.h> 24 #include <linux/kdebug.h> 25 #include <linux/init.h> 26 #include <linux/console.h> 27 #include <linux/module.h> 28 #include <linux/hardirq.h> 29 #include <linux/kprobes.h> 30 #include <linux/uaccess.h> 31 #include <linux/hugetlb.h> 32 #include <asm/asm-offsets.h> 33 #include <asm/pgtable.h> 34 #include <asm/irq.h> 35 #include <asm/mmu_context.h> 36 #include <asm/facility.h> 37 #include "../kernel/entry.h" 38 39 #ifndef CONFIG_64BIT 40 #define __FAIL_ADDR_MASK 0x7ffff000 41 #define __SUBCODE_MASK 0x0200 42 #define __PF_RES_FIELD 0ULL 43 #else /* CONFIG_64BIT */ 44 #define __FAIL_ADDR_MASK -4096L 45 #define __SUBCODE_MASK 0x0600 46 #define __PF_RES_FIELD 0x8000000000000000ULL 47 #endif /* CONFIG_64BIT */ 48 49 #define VM_FAULT_BADCONTEXT 0x010000 50 #define VM_FAULT_BADMAP 0x020000 51 #define VM_FAULT_BADACCESS 0x040000 52 #define VM_FAULT_SIGNAL 0x080000 53 54 static unsigned long store_indication __read_mostly; 55 56 #ifdef CONFIG_64BIT 57 static int __init fault_init(void) 58 { 59 if (test_facility(75)) 60 store_indication = 0xc00; 61 return 0; 62 } 63 early_initcall(fault_init); 64 #endif 65 66 static inline int notify_page_fault(struct pt_regs *regs) 67 { 68 int ret = 0; 69 70 /* kprobe_running() needs smp_processor_id() */ 71 if (kprobes_built_in() && !user_mode(regs)) { 72 preempt_disable(); 73 if (kprobe_running() && kprobe_fault_handler(regs, 14)) 74 ret = 1; 75 preempt_enable(); 76 } 77 return ret; 78 } 79 80 81 /* 82 * Unlock any spinlocks which will prevent us from getting the 83 * message out. 84 */ 85 void bust_spinlocks(int yes) 86 { 87 if (yes) { 88 oops_in_progress = 1; 89 } else { 90 int loglevel_save = console_loglevel; 91 console_unblank(); 92 oops_in_progress = 0; 93 /* 94 * OK, the message is on the console. Now we call printk() 95 * without oops_in_progress set so that printk will give klogd 96 * a poke. Hold onto your hats... 97 */ 98 console_loglevel = 15; 99 printk(" "); 100 console_loglevel = loglevel_save; 101 } 102 } 103 104 /* 105 * Returns the address space associated with the fault. 106 * Returns 0 for kernel space and 1 for user space. 107 */ 108 static inline int user_space_fault(unsigned long trans_exc_code) 109 { 110 /* 111 * The lowest two bits of the translation exception 112 * identification indicate which paging table was used. 113 */ 114 trans_exc_code &= 3; 115 if (trans_exc_code == 2) 116 /* Access via secondary space, set_fs setting decides */ 117 return current->thread.mm_segment.ar4; 118 /* 119 * Access via primary space or access register is from user space 120 * and access via home space is from the kernel. 121 */ 122 return trans_exc_code != 3; 123 } 124 125 static inline void report_user_fault(struct pt_regs *regs, long signr) 126 { 127 if ((task_pid_nr(current) > 1) && !show_unhandled_signals) 128 return; 129 if (!unhandled_signal(current, signr)) 130 return; 131 if (!printk_ratelimit()) 132 return; 133 printk(KERN_ALERT "User process fault: interruption code 0x%X ", 134 regs->int_code); 135 print_vma_addr(KERN_CONT "in ", regs->psw.addr & PSW_ADDR_INSN); 136 printk(KERN_CONT "\n"); 137 printk(KERN_ALERT "failing address: %lX\n", 138 regs->int_parm_long & __FAIL_ADDR_MASK); 139 show_regs(regs); 140 } 141 142 /* 143 * Send SIGSEGV to task. This is an external routine 144 * to keep the stack usage of do_page_fault small. 145 */ 146 static noinline void do_sigsegv(struct pt_regs *regs, int si_code) 147 { 148 struct siginfo si; 149 150 report_user_fault(regs, SIGSEGV); 151 si.si_signo = SIGSEGV; 152 si.si_code = si_code; 153 si.si_addr = (void __user *)(regs->int_parm_long & __FAIL_ADDR_MASK); 154 force_sig_info(SIGSEGV, &si, current); 155 } 156 157 static noinline void do_no_context(struct pt_regs *regs) 158 { 159 const struct exception_table_entry *fixup; 160 unsigned long address; 161 162 /* Are we prepared to handle this kernel fault? */ 163 fixup = search_exception_tables(regs->psw.addr & PSW_ADDR_INSN); 164 if (fixup) { 165 regs->psw.addr = extable_fixup(fixup) | PSW_ADDR_AMODE; 166 return; 167 } 168 169 /* 170 * Oops. The kernel tried to access some bad page. We'll have to 171 * terminate things with extreme prejudice. 172 */ 173 address = regs->int_parm_long & __FAIL_ADDR_MASK; 174 if (!user_space_fault(regs->int_parm_long)) 175 printk(KERN_ALERT "Unable to handle kernel pointer dereference" 176 " at virtual kernel address %p\n", (void *)address); 177 else 178 printk(KERN_ALERT "Unable to handle kernel paging request" 179 " at virtual user address %p\n", (void *)address); 180 181 die(regs, "Oops"); 182 do_exit(SIGKILL); 183 } 184 185 static noinline void do_low_address(struct pt_regs *regs) 186 { 187 /* Low-address protection hit in kernel mode means 188 NULL pointer write access in kernel mode. */ 189 if (regs->psw.mask & PSW_MASK_PSTATE) { 190 /* Low-address protection hit in user mode 'cannot happen'. */ 191 die (regs, "Low-address protection"); 192 do_exit(SIGKILL); 193 } 194 195 do_no_context(regs); 196 } 197 198 static noinline void do_sigbus(struct pt_regs *regs) 199 { 200 struct task_struct *tsk = current; 201 struct siginfo si; 202 203 /* 204 * Send a sigbus, regardless of whether we were in kernel 205 * or user mode. 206 */ 207 si.si_signo = SIGBUS; 208 si.si_errno = 0; 209 si.si_code = BUS_ADRERR; 210 si.si_addr = (void __user *)(regs->int_parm_long & __FAIL_ADDR_MASK); 211 force_sig_info(SIGBUS, &si, tsk); 212 } 213 214 static noinline void do_fault_error(struct pt_regs *regs, int fault) 215 { 216 int si_code; 217 218 switch (fault) { 219 case VM_FAULT_BADACCESS: 220 case VM_FAULT_BADMAP: 221 /* Bad memory access. Check if it is kernel or user space. */ 222 if (user_mode(regs)) { 223 /* User mode accesses just cause a SIGSEGV */ 224 si_code = (fault == VM_FAULT_BADMAP) ? 225 SEGV_MAPERR : SEGV_ACCERR; 226 do_sigsegv(regs, si_code); 227 return; 228 } 229 case VM_FAULT_BADCONTEXT: 230 do_no_context(regs); 231 break; 232 case VM_FAULT_SIGNAL: 233 if (!user_mode(regs)) 234 do_no_context(regs); 235 break; 236 default: /* fault & VM_FAULT_ERROR */ 237 if (fault & VM_FAULT_OOM) { 238 if (!user_mode(regs)) 239 do_no_context(regs); 240 else 241 pagefault_out_of_memory(); 242 } else if (fault & VM_FAULT_SIGBUS) { 243 /* Kernel mode? Handle exceptions or die */ 244 if (!user_mode(regs)) 245 do_no_context(regs); 246 else 247 do_sigbus(regs); 248 } else 249 BUG(); 250 break; 251 } 252 } 253 254 /* 255 * This routine handles page faults. It determines the address, 256 * and the problem, and then passes it off to one of the appropriate 257 * routines. 258 * 259 * interruption code (int_code): 260 * 04 Protection -> Write-Protection (suprression) 261 * 10 Segment translation -> Not present (nullification) 262 * 11 Page translation -> Not present (nullification) 263 * 3b Region third trans. -> Not present (nullification) 264 */ 265 static inline int do_exception(struct pt_regs *regs, int access) 266 { 267 struct task_struct *tsk; 268 struct mm_struct *mm; 269 struct vm_area_struct *vma; 270 unsigned long trans_exc_code; 271 unsigned long address; 272 unsigned int flags; 273 int fault; 274 275 tsk = current; 276 /* 277 * The instruction that caused the program check has 278 * been nullified. Don't signal single step via SIGTRAP. 279 */ 280 clear_tsk_thread_flag(tsk, TIF_PER_TRAP); 281 282 if (notify_page_fault(regs)) 283 return 0; 284 285 mm = tsk->mm; 286 trans_exc_code = regs->int_parm_long; 287 288 /* 289 * Verify that the fault happened in user space, that 290 * we are not in an interrupt and that there is a 291 * user context. 292 */ 293 fault = VM_FAULT_BADCONTEXT; 294 if (unlikely(!user_space_fault(trans_exc_code) || in_atomic() || !mm)) 295 goto out; 296 297 address = trans_exc_code & __FAIL_ADDR_MASK; 298 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 299 flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; 300 if (user_mode(regs)) 301 flags |= FAULT_FLAG_USER; 302 if (access == VM_WRITE || (trans_exc_code & store_indication) == 0x400) 303 flags |= FAULT_FLAG_WRITE; 304 down_read(&mm->mmap_sem); 305 306 #ifdef CONFIG_PGSTE 307 if ((current->flags & PF_VCPU) && S390_lowcore.gmap) { 308 address = __gmap_fault(address, 309 (struct gmap *) S390_lowcore.gmap); 310 if (address == -EFAULT) { 311 fault = VM_FAULT_BADMAP; 312 goto out_up; 313 } 314 if (address == -ENOMEM) { 315 fault = VM_FAULT_OOM; 316 goto out_up; 317 } 318 } 319 #endif 320 321 retry: 322 fault = VM_FAULT_BADMAP; 323 vma = find_vma(mm, address); 324 if (!vma) 325 goto out_up; 326 327 if (unlikely(vma->vm_start > address)) { 328 if (!(vma->vm_flags & VM_GROWSDOWN)) 329 goto out_up; 330 if (expand_stack(vma, address)) 331 goto out_up; 332 } 333 334 /* 335 * Ok, we have a good vm_area for this memory access, so 336 * we can handle it.. 337 */ 338 fault = VM_FAULT_BADACCESS; 339 if (unlikely(!(vma->vm_flags & access))) 340 goto out_up; 341 342 if (is_vm_hugetlb_page(vma)) 343 address &= HPAGE_MASK; 344 /* 345 * If for any reason at all we couldn't handle the fault, 346 * make sure we exit gracefully rather than endlessly redo 347 * the fault. 348 */ 349 fault = handle_mm_fault(mm, vma, address, flags); 350 /* No reason to continue if interrupted by SIGKILL. */ 351 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) { 352 fault = VM_FAULT_SIGNAL; 353 goto out; 354 } 355 if (unlikely(fault & VM_FAULT_ERROR)) 356 goto out_up; 357 358 /* 359 * Major/minor page fault accounting is only done on the 360 * initial attempt. If we go through a retry, it is extremely 361 * likely that the page will be found in page cache at that point. 362 */ 363 if (flags & FAULT_FLAG_ALLOW_RETRY) { 364 if (fault & VM_FAULT_MAJOR) { 365 tsk->maj_flt++; 366 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, 367 regs, address); 368 } else { 369 tsk->min_flt++; 370 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, 371 regs, address); 372 } 373 if (fault & VM_FAULT_RETRY) { 374 /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk 375 * of starvation. */ 376 flags &= ~FAULT_FLAG_ALLOW_RETRY; 377 flags |= FAULT_FLAG_TRIED; 378 down_read(&mm->mmap_sem); 379 goto retry; 380 } 381 } 382 fault = 0; 383 out_up: 384 up_read(&mm->mmap_sem); 385 out: 386 return fault; 387 } 388 389 void __kprobes do_protection_exception(struct pt_regs *regs) 390 { 391 unsigned long trans_exc_code; 392 int fault; 393 394 trans_exc_code = regs->int_parm_long; 395 /* 396 * Protection exceptions are suppressing, decrement psw address. 397 * The exception to this rule are aborted transactions, for these 398 * the PSW already points to the correct location. 399 */ 400 if (!(regs->int_code & 0x200)) 401 regs->psw.addr = __rewind_psw(regs->psw, regs->int_code >> 16); 402 /* 403 * Check for low-address protection. This needs to be treated 404 * as a special case because the translation exception code 405 * field is not guaranteed to contain valid data in this case. 406 */ 407 if (unlikely(!(trans_exc_code & 4))) { 408 do_low_address(regs); 409 return; 410 } 411 fault = do_exception(regs, VM_WRITE); 412 if (unlikely(fault)) 413 do_fault_error(regs, fault); 414 } 415 416 void __kprobes do_dat_exception(struct pt_regs *regs) 417 { 418 int access, fault; 419 420 access = VM_READ | VM_EXEC | VM_WRITE; 421 fault = do_exception(regs, access); 422 if (unlikely(fault)) 423 do_fault_error(regs, fault); 424 } 425 426 int __handle_fault(unsigned long uaddr, unsigned long pgm_int_code, int write) 427 { 428 struct pt_regs regs; 429 int access, fault; 430 431 /* Emulate a uaccess fault from kernel mode. */ 432 regs.psw.mask = PSW_KERNEL_BITS | PSW_MASK_DAT | PSW_MASK_MCHECK; 433 if (!irqs_disabled()) 434 regs.psw.mask |= PSW_MASK_IO | PSW_MASK_EXT; 435 regs.psw.addr = (unsigned long) __builtin_return_address(0); 436 regs.psw.addr |= PSW_ADDR_AMODE; 437 regs.int_code = pgm_int_code; 438 regs.int_parm_long = (uaddr & PAGE_MASK) | 2; 439 access = write ? VM_WRITE : VM_READ; 440 fault = do_exception(®s, access); 441 /* 442 * Since the fault happened in kernel mode while performing a uaccess 443 * all we need to do now is emulating a fixup in case "fault" is not 444 * zero. 445 * For the calling uaccess functions this results always in -EFAULT. 446 */ 447 return fault ? -EFAULT : 0; 448 } 449 450 #ifdef CONFIG_PFAULT 451 /* 452 * 'pfault' pseudo page faults routines. 453 */ 454 static int pfault_disable; 455 456 static int __init nopfault(char *str) 457 { 458 pfault_disable = 1; 459 return 1; 460 } 461 462 __setup("nopfault", nopfault); 463 464 struct pfault_refbk { 465 u16 refdiagc; 466 u16 reffcode; 467 u16 refdwlen; 468 u16 refversn; 469 u64 refgaddr; 470 u64 refselmk; 471 u64 refcmpmk; 472 u64 reserved; 473 } __attribute__ ((packed, aligned(8))); 474 475 int pfault_init(void) 476 { 477 struct pfault_refbk refbk = { 478 .refdiagc = 0x258, 479 .reffcode = 0, 480 .refdwlen = 5, 481 .refversn = 2, 482 .refgaddr = __LC_CURRENT_PID, 483 .refselmk = 1ULL << 48, 484 .refcmpmk = 1ULL << 48, 485 .reserved = __PF_RES_FIELD }; 486 int rc; 487 488 if (pfault_disable) 489 return -1; 490 asm volatile( 491 " diag %1,%0,0x258\n" 492 "0: j 2f\n" 493 "1: la %0,8\n" 494 "2:\n" 495 EX_TABLE(0b,1b) 496 : "=d" (rc) : "a" (&refbk), "m" (refbk) : "cc"); 497 return rc; 498 } 499 500 void pfault_fini(void) 501 { 502 struct pfault_refbk refbk = { 503 .refdiagc = 0x258, 504 .reffcode = 1, 505 .refdwlen = 5, 506 .refversn = 2, 507 }; 508 509 if (pfault_disable) 510 return; 511 asm volatile( 512 " diag %0,0,0x258\n" 513 "0:\n" 514 EX_TABLE(0b,0b) 515 : : "a" (&refbk), "m" (refbk) : "cc"); 516 } 517 518 static DEFINE_SPINLOCK(pfault_lock); 519 static LIST_HEAD(pfault_list); 520 521 static void pfault_interrupt(struct ext_code ext_code, 522 unsigned int param32, unsigned long param64) 523 { 524 struct task_struct *tsk; 525 __u16 subcode; 526 pid_t pid; 527 528 /* 529 * Get the external interruption subcode & pfault 530 * initial/completion signal bit. VM stores this 531 * in the 'cpu address' field associated with the 532 * external interrupt. 533 */ 534 subcode = ext_code.subcode; 535 if ((subcode & 0xff00) != __SUBCODE_MASK) 536 return; 537 inc_irq_stat(IRQEXT_PFL); 538 /* Get the token (= pid of the affected task). */ 539 pid = sizeof(void *) == 4 ? param32 : param64; 540 rcu_read_lock(); 541 tsk = find_task_by_pid_ns(pid, &init_pid_ns); 542 if (tsk) 543 get_task_struct(tsk); 544 rcu_read_unlock(); 545 if (!tsk) 546 return; 547 spin_lock(&pfault_lock); 548 if (subcode & 0x0080) { 549 /* signal bit is set -> a page has been swapped in by VM */ 550 if (tsk->thread.pfault_wait == 1) { 551 /* Initial interrupt was faster than the completion 552 * interrupt. pfault_wait is valid. Set pfault_wait 553 * back to zero and wake up the process. This can 554 * safely be done because the task is still sleeping 555 * and can't produce new pfaults. */ 556 tsk->thread.pfault_wait = 0; 557 list_del(&tsk->thread.list); 558 wake_up_process(tsk); 559 put_task_struct(tsk); 560 } else { 561 /* Completion interrupt was faster than initial 562 * interrupt. Set pfault_wait to -1 so the initial 563 * interrupt doesn't put the task to sleep. 564 * If the task is not running, ignore the completion 565 * interrupt since it must be a leftover of a PFAULT 566 * CANCEL operation which didn't remove all pending 567 * completion interrupts. */ 568 if (tsk->state == TASK_RUNNING) 569 tsk->thread.pfault_wait = -1; 570 } 571 } else { 572 /* signal bit not set -> a real page is missing. */ 573 if (WARN_ON_ONCE(tsk != current)) 574 goto out; 575 if (tsk->thread.pfault_wait == 1) { 576 /* Already on the list with a reference: put to sleep */ 577 __set_task_state(tsk, TASK_UNINTERRUPTIBLE); 578 set_tsk_need_resched(tsk); 579 } else if (tsk->thread.pfault_wait == -1) { 580 /* Completion interrupt was faster than the initial 581 * interrupt (pfault_wait == -1). Set pfault_wait 582 * back to zero and exit. */ 583 tsk->thread.pfault_wait = 0; 584 } else { 585 /* Initial interrupt arrived before completion 586 * interrupt. Let the task sleep. 587 * An extra task reference is needed since a different 588 * cpu may set the task state to TASK_RUNNING again 589 * before the scheduler is reached. */ 590 get_task_struct(tsk); 591 tsk->thread.pfault_wait = 1; 592 list_add(&tsk->thread.list, &pfault_list); 593 __set_task_state(tsk, TASK_UNINTERRUPTIBLE); 594 set_tsk_need_resched(tsk); 595 } 596 } 597 out: 598 spin_unlock(&pfault_lock); 599 put_task_struct(tsk); 600 } 601 602 static int pfault_cpu_notify(struct notifier_block *self, unsigned long action, 603 void *hcpu) 604 { 605 struct thread_struct *thread, *next; 606 struct task_struct *tsk; 607 608 switch (action & ~CPU_TASKS_FROZEN) { 609 case CPU_DEAD: 610 spin_lock_irq(&pfault_lock); 611 list_for_each_entry_safe(thread, next, &pfault_list, list) { 612 thread->pfault_wait = 0; 613 list_del(&thread->list); 614 tsk = container_of(thread, struct task_struct, thread); 615 wake_up_process(tsk); 616 put_task_struct(tsk); 617 } 618 spin_unlock_irq(&pfault_lock); 619 break; 620 default: 621 break; 622 } 623 return NOTIFY_OK; 624 } 625 626 static int __init pfault_irq_init(void) 627 { 628 int rc; 629 630 rc = register_external_interrupt(0x2603, pfault_interrupt); 631 if (rc) 632 goto out_extint; 633 rc = pfault_init() == 0 ? 0 : -EOPNOTSUPP; 634 if (rc) 635 goto out_pfault; 636 irq_subclass_register(IRQ_SUBCLASS_SERVICE_SIGNAL); 637 hotcpu_notifier(pfault_cpu_notify, 0); 638 return 0; 639 640 out_pfault: 641 unregister_external_interrupt(0x2603, pfault_interrupt); 642 out_extint: 643 pfault_disable = 1; 644 return rc; 645 } 646 early_initcall(pfault_irq_init); 647 648 #endif /* CONFIG_PFAULT */ 649