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 #define VM_FAULT_PFAULT 0x100000 54 55 static unsigned long store_indication __read_mostly; 56 57 #ifdef CONFIG_64BIT 58 static int __init fault_init(void) 59 { 60 if (test_facility(75)) 61 store_indication = 0xc00; 62 return 0; 63 } 64 early_initcall(fault_init); 65 #endif 66 67 static inline int notify_page_fault(struct pt_regs *regs) 68 { 69 int ret = 0; 70 71 /* kprobe_running() needs smp_processor_id() */ 72 if (kprobes_built_in() && !user_mode(regs)) { 73 preempt_disable(); 74 if (kprobe_running() && kprobe_fault_handler(regs, 14)) 75 ret = 1; 76 preempt_enable(); 77 } 78 return ret; 79 } 80 81 82 /* 83 * Unlock any spinlocks which will prevent us from getting the 84 * message out. 85 */ 86 void bust_spinlocks(int yes) 87 { 88 if (yes) { 89 oops_in_progress = 1; 90 } else { 91 int loglevel_save = console_loglevel; 92 console_unblank(); 93 oops_in_progress = 0; 94 /* 95 * OK, the message is on the console. Now we call printk() 96 * without oops_in_progress set so that printk will give klogd 97 * a poke. Hold onto your hats... 98 */ 99 console_loglevel = 15; 100 printk(" "); 101 console_loglevel = loglevel_save; 102 } 103 } 104 105 /* 106 * Returns the address space associated with the fault. 107 * Returns 0 for kernel space and 1 for user space. 108 */ 109 static inline int user_space_fault(struct pt_regs *regs) 110 { 111 unsigned long trans_exc_code; 112 113 /* 114 * The lowest two bits of the translation exception 115 * identification indicate which paging table was used. 116 */ 117 trans_exc_code = regs->int_parm_long & 3; 118 if (trans_exc_code == 3) /* home space -> kernel */ 119 return 0; 120 if (user_mode(regs)) 121 return 1; 122 if (trans_exc_code == 2) /* secondary space -> set_fs */ 123 return current->thread.mm_segment.ar4; 124 if (current->flags & PF_VCPU) 125 return 1; 126 return 0; 127 } 128 129 static inline void report_user_fault(struct pt_regs *regs, long signr) 130 { 131 if ((task_pid_nr(current) > 1) && !show_unhandled_signals) 132 return; 133 if (!unhandled_signal(current, signr)) 134 return; 135 if (!printk_ratelimit()) 136 return; 137 printk(KERN_ALERT "User process fault: interruption code 0x%X ", 138 regs->int_code); 139 print_vma_addr(KERN_CONT "in ", regs->psw.addr & PSW_ADDR_INSN); 140 printk(KERN_CONT "\n"); 141 printk(KERN_ALERT "failing address: %lX\n", 142 regs->int_parm_long & __FAIL_ADDR_MASK); 143 show_regs(regs); 144 } 145 146 /* 147 * Send SIGSEGV to task. This is an external routine 148 * to keep the stack usage of do_page_fault small. 149 */ 150 static noinline void do_sigsegv(struct pt_regs *regs, int si_code) 151 { 152 struct siginfo si; 153 154 report_user_fault(regs, SIGSEGV); 155 si.si_signo = SIGSEGV; 156 si.si_code = si_code; 157 si.si_addr = (void __user *)(regs->int_parm_long & __FAIL_ADDR_MASK); 158 force_sig_info(SIGSEGV, &si, current); 159 } 160 161 static noinline void do_no_context(struct pt_regs *regs) 162 { 163 const struct exception_table_entry *fixup; 164 unsigned long address; 165 166 /* Are we prepared to handle this kernel fault? */ 167 fixup = search_exception_tables(regs->psw.addr & PSW_ADDR_INSN); 168 if (fixup) { 169 regs->psw.addr = extable_fixup(fixup) | PSW_ADDR_AMODE; 170 return; 171 } 172 173 /* 174 * Oops. The kernel tried to access some bad page. We'll have to 175 * terminate things with extreme prejudice. 176 */ 177 address = regs->int_parm_long & __FAIL_ADDR_MASK; 178 if (!user_space_fault(regs)) 179 printk(KERN_ALERT "Unable to handle kernel pointer dereference" 180 " at virtual kernel address %p\n", (void *)address); 181 else 182 printk(KERN_ALERT "Unable to handle kernel paging request" 183 " at virtual user address %p\n", (void *)address); 184 185 die(regs, "Oops"); 186 do_exit(SIGKILL); 187 } 188 189 static noinline void do_low_address(struct pt_regs *regs) 190 { 191 /* Low-address protection hit in kernel mode means 192 NULL pointer write access in kernel mode. */ 193 if (regs->psw.mask & PSW_MASK_PSTATE) { 194 /* Low-address protection hit in user mode 'cannot happen'. */ 195 die (regs, "Low-address protection"); 196 do_exit(SIGKILL); 197 } 198 199 do_no_context(regs); 200 } 201 202 static noinline void do_sigbus(struct pt_regs *regs) 203 { 204 struct task_struct *tsk = current; 205 struct siginfo si; 206 207 /* 208 * Send a sigbus, regardless of whether we were in kernel 209 * or user mode. 210 */ 211 si.si_signo = SIGBUS; 212 si.si_errno = 0; 213 si.si_code = BUS_ADRERR; 214 si.si_addr = (void __user *)(regs->int_parm_long & __FAIL_ADDR_MASK); 215 force_sig_info(SIGBUS, &si, tsk); 216 } 217 218 static noinline void do_fault_error(struct pt_regs *regs, int fault) 219 { 220 int si_code; 221 222 switch (fault) { 223 case VM_FAULT_BADACCESS: 224 case VM_FAULT_BADMAP: 225 /* Bad memory access. Check if it is kernel or user space. */ 226 if (user_mode(regs)) { 227 /* User mode accesses just cause a SIGSEGV */ 228 si_code = (fault == VM_FAULT_BADMAP) ? 229 SEGV_MAPERR : SEGV_ACCERR; 230 do_sigsegv(regs, si_code); 231 return; 232 } 233 case VM_FAULT_BADCONTEXT: 234 case VM_FAULT_PFAULT: 235 do_no_context(regs); 236 break; 237 case VM_FAULT_SIGNAL: 238 if (!user_mode(regs)) 239 do_no_context(regs); 240 break; 241 default: /* fault & VM_FAULT_ERROR */ 242 if (fault & VM_FAULT_OOM) { 243 if (!user_mode(regs)) 244 do_no_context(regs); 245 else 246 pagefault_out_of_memory(); 247 } else if (fault & VM_FAULT_SIGBUS) { 248 /* Kernel mode? Handle exceptions or die */ 249 if (!user_mode(regs)) 250 do_no_context(regs); 251 else 252 do_sigbus(regs); 253 } else 254 BUG(); 255 break; 256 } 257 } 258 259 /* 260 * This routine handles page faults. It determines the address, 261 * and the problem, and then passes it off to one of the appropriate 262 * routines. 263 * 264 * interruption code (int_code): 265 * 04 Protection -> Write-Protection (suprression) 266 * 10 Segment translation -> Not present (nullification) 267 * 11 Page translation -> Not present (nullification) 268 * 3b Region third trans. -> Not present (nullification) 269 */ 270 static inline int do_exception(struct pt_regs *regs, int access) 271 { 272 #ifdef CONFIG_PGSTE 273 struct gmap *gmap; 274 #endif 275 struct task_struct *tsk; 276 struct mm_struct *mm; 277 struct vm_area_struct *vma; 278 unsigned long trans_exc_code; 279 unsigned long address; 280 unsigned int flags; 281 int fault; 282 283 tsk = current; 284 /* 285 * The instruction that caused the program check has 286 * been nullified. Don't signal single step via SIGTRAP. 287 */ 288 clear_tsk_thread_flag(tsk, TIF_PER_TRAP); 289 290 if (notify_page_fault(regs)) 291 return 0; 292 293 mm = tsk->mm; 294 trans_exc_code = regs->int_parm_long; 295 296 /* 297 * Verify that the fault happened in user space, that 298 * we are not in an interrupt and that there is a 299 * user context. 300 */ 301 fault = VM_FAULT_BADCONTEXT; 302 if (unlikely(!user_space_fault(regs) || in_atomic() || !mm)) 303 goto out; 304 305 address = trans_exc_code & __FAIL_ADDR_MASK; 306 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 307 flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; 308 if (user_mode(regs)) 309 flags |= FAULT_FLAG_USER; 310 if (access == VM_WRITE || (trans_exc_code & store_indication) == 0x400) 311 flags |= FAULT_FLAG_WRITE; 312 down_read(&mm->mmap_sem); 313 314 #ifdef CONFIG_PGSTE 315 gmap = (struct gmap *) 316 ((current->flags & PF_VCPU) ? S390_lowcore.gmap : 0); 317 if (gmap) { 318 address = __gmap_fault(address, gmap); 319 if (address == -EFAULT) { 320 fault = VM_FAULT_BADMAP; 321 goto out_up; 322 } 323 if (address == -ENOMEM) { 324 fault = VM_FAULT_OOM; 325 goto out_up; 326 } 327 if (gmap->pfault_enabled) 328 flags |= FAULT_FLAG_RETRY_NOWAIT; 329 } 330 #endif 331 332 retry: 333 fault = VM_FAULT_BADMAP; 334 vma = find_vma(mm, address); 335 if (!vma) 336 goto out_up; 337 338 if (unlikely(vma->vm_start > address)) { 339 if (!(vma->vm_flags & VM_GROWSDOWN)) 340 goto out_up; 341 if (expand_stack(vma, address)) 342 goto out_up; 343 } 344 345 /* 346 * Ok, we have a good vm_area for this memory access, so 347 * we can handle it.. 348 */ 349 fault = VM_FAULT_BADACCESS; 350 if (unlikely(!(vma->vm_flags & access))) 351 goto out_up; 352 353 if (is_vm_hugetlb_page(vma)) 354 address &= HPAGE_MASK; 355 /* 356 * If for any reason at all we couldn't handle the fault, 357 * make sure we exit gracefully rather than endlessly redo 358 * the fault. 359 */ 360 fault = handle_mm_fault(mm, vma, address, flags); 361 /* No reason to continue if interrupted by SIGKILL. */ 362 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) { 363 fault = VM_FAULT_SIGNAL; 364 goto out; 365 } 366 if (unlikely(fault & VM_FAULT_ERROR)) 367 goto out_up; 368 369 /* 370 * Major/minor page fault accounting is only done on the 371 * initial attempt. If we go through a retry, it is extremely 372 * likely that the page will be found in page cache at that point. 373 */ 374 if (flags & FAULT_FLAG_ALLOW_RETRY) { 375 if (fault & VM_FAULT_MAJOR) { 376 tsk->maj_flt++; 377 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, 378 regs, address); 379 } else { 380 tsk->min_flt++; 381 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, 382 regs, address); 383 } 384 if (fault & VM_FAULT_RETRY) { 385 #ifdef CONFIG_PGSTE 386 if (gmap && (flags & FAULT_FLAG_RETRY_NOWAIT)) { 387 /* FAULT_FLAG_RETRY_NOWAIT has been set, 388 * mmap_sem has not been released */ 389 current->thread.gmap_pfault = 1; 390 fault = VM_FAULT_PFAULT; 391 goto out_up; 392 } 393 #endif 394 /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk 395 * of starvation. */ 396 flags &= ~(FAULT_FLAG_ALLOW_RETRY | 397 FAULT_FLAG_RETRY_NOWAIT); 398 flags |= FAULT_FLAG_TRIED; 399 down_read(&mm->mmap_sem); 400 goto retry; 401 } 402 } 403 fault = 0; 404 out_up: 405 up_read(&mm->mmap_sem); 406 out: 407 return fault; 408 } 409 410 void __kprobes do_protection_exception(struct pt_regs *regs) 411 { 412 unsigned long trans_exc_code; 413 int fault; 414 415 trans_exc_code = regs->int_parm_long; 416 /* 417 * Protection exceptions are suppressing, decrement psw address. 418 * The exception to this rule are aborted transactions, for these 419 * the PSW already points to the correct location. 420 */ 421 if (!(regs->int_code & 0x200)) 422 regs->psw.addr = __rewind_psw(regs->psw, regs->int_code >> 16); 423 /* 424 * Check for low-address protection. This needs to be treated 425 * as a special case because the translation exception code 426 * field is not guaranteed to contain valid data in this case. 427 */ 428 if (unlikely(!(trans_exc_code & 4))) { 429 do_low_address(regs); 430 return; 431 } 432 fault = do_exception(regs, VM_WRITE); 433 if (unlikely(fault)) 434 do_fault_error(regs, fault); 435 } 436 437 void __kprobes do_dat_exception(struct pt_regs *regs) 438 { 439 int access, fault; 440 441 access = VM_READ | VM_EXEC | VM_WRITE; 442 fault = do_exception(regs, access); 443 if (unlikely(fault)) 444 do_fault_error(regs, fault); 445 } 446 447 #ifdef CONFIG_PFAULT 448 /* 449 * 'pfault' pseudo page faults routines. 450 */ 451 static int pfault_disable; 452 453 static int __init nopfault(char *str) 454 { 455 pfault_disable = 1; 456 return 1; 457 } 458 459 __setup("nopfault", nopfault); 460 461 struct pfault_refbk { 462 u16 refdiagc; 463 u16 reffcode; 464 u16 refdwlen; 465 u16 refversn; 466 u64 refgaddr; 467 u64 refselmk; 468 u64 refcmpmk; 469 u64 reserved; 470 } __attribute__ ((packed, aligned(8))); 471 472 int pfault_init(void) 473 { 474 struct pfault_refbk refbk = { 475 .refdiagc = 0x258, 476 .reffcode = 0, 477 .refdwlen = 5, 478 .refversn = 2, 479 .refgaddr = __LC_CURRENT_PID, 480 .refselmk = 1ULL << 48, 481 .refcmpmk = 1ULL << 48, 482 .reserved = __PF_RES_FIELD }; 483 int rc; 484 485 if (pfault_disable) 486 return -1; 487 asm volatile( 488 " diag %1,%0,0x258\n" 489 "0: j 2f\n" 490 "1: la %0,8\n" 491 "2:\n" 492 EX_TABLE(0b,1b) 493 : "=d" (rc) : "a" (&refbk), "m" (refbk) : "cc"); 494 return rc; 495 } 496 497 void pfault_fini(void) 498 { 499 struct pfault_refbk refbk = { 500 .refdiagc = 0x258, 501 .reffcode = 1, 502 .refdwlen = 5, 503 .refversn = 2, 504 }; 505 506 if (pfault_disable) 507 return; 508 asm volatile( 509 " diag %0,0,0x258\n" 510 "0:\n" 511 EX_TABLE(0b,0b) 512 : : "a" (&refbk), "m" (refbk) : "cc"); 513 } 514 515 static DEFINE_SPINLOCK(pfault_lock); 516 static LIST_HEAD(pfault_list); 517 518 static void pfault_interrupt(struct ext_code ext_code, 519 unsigned int param32, unsigned long param64) 520 { 521 struct task_struct *tsk; 522 __u16 subcode; 523 pid_t pid; 524 525 /* 526 * Get the external interruption subcode & pfault 527 * initial/completion signal bit. VM stores this 528 * in the 'cpu address' field associated with the 529 * external interrupt. 530 */ 531 subcode = ext_code.subcode; 532 if ((subcode & 0xff00) != __SUBCODE_MASK) 533 return; 534 inc_irq_stat(IRQEXT_PFL); 535 /* Get the token (= pid of the affected task). */ 536 pid = sizeof(void *) == 4 ? param32 : param64; 537 rcu_read_lock(); 538 tsk = find_task_by_pid_ns(pid, &init_pid_ns); 539 if (tsk) 540 get_task_struct(tsk); 541 rcu_read_unlock(); 542 if (!tsk) 543 return; 544 spin_lock(&pfault_lock); 545 if (subcode & 0x0080) { 546 /* signal bit is set -> a page has been swapped in by VM */ 547 if (tsk->thread.pfault_wait == 1) { 548 /* Initial interrupt was faster than the completion 549 * interrupt. pfault_wait is valid. Set pfault_wait 550 * back to zero and wake up the process. This can 551 * safely be done because the task is still sleeping 552 * and can't produce new pfaults. */ 553 tsk->thread.pfault_wait = 0; 554 list_del(&tsk->thread.list); 555 wake_up_process(tsk); 556 put_task_struct(tsk); 557 } else { 558 /* Completion interrupt was faster than initial 559 * interrupt. Set pfault_wait to -1 so the initial 560 * interrupt doesn't put the task to sleep. 561 * If the task is not running, ignore the completion 562 * interrupt since it must be a leftover of a PFAULT 563 * CANCEL operation which didn't remove all pending 564 * completion interrupts. */ 565 if (tsk->state == TASK_RUNNING) 566 tsk->thread.pfault_wait = -1; 567 } 568 } else { 569 /* signal bit not set -> a real page is missing. */ 570 if (WARN_ON_ONCE(tsk != current)) 571 goto out; 572 if (tsk->thread.pfault_wait == 1) { 573 /* Already on the list with a reference: put to sleep */ 574 __set_task_state(tsk, TASK_UNINTERRUPTIBLE); 575 set_tsk_need_resched(tsk); 576 } else if (tsk->thread.pfault_wait == -1) { 577 /* Completion interrupt was faster than the initial 578 * interrupt (pfault_wait == -1). Set pfault_wait 579 * back to zero and exit. */ 580 tsk->thread.pfault_wait = 0; 581 } else { 582 /* Initial interrupt arrived before completion 583 * interrupt. Let the task sleep. 584 * An extra task reference is needed since a different 585 * cpu may set the task state to TASK_RUNNING again 586 * before the scheduler is reached. */ 587 get_task_struct(tsk); 588 tsk->thread.pfault_wait = 1; 589 list_add(&tsk->thread.list, &pfault_list); 590 __set_task_state(tsk, TASK_UNINTERRUPTIBLE); 591 set_tsk_need_resched(tsk); 592 } 593 } 594 out: 595 spin_unlock(&pfault_lock); 596 put_task_struct(tsk); 597 } 598 599 static int pfault_cpu_notify(struct notifier_block *self, unsigned long action, 600 void *hcpu) 601 { 602 struct thread_struct *thread, *next; 603 struct task_struct *tsk; 604 605 switch (action & ~CPU_TASKS_FROZEN) { 606 case CPU_DEAD: 607 spin_lock_irq(&pfault_lock); 608 list_for_each_entry_safe(thread, next, &pfault_list, list) { 609 thread->pfault_wait = 0; 610 list_del(&thread->list); 611 tsk = container_of(thread, struct task_struct, thread); 612 wake_up_process(tsk); 613 put_task_struct(tsk); 614 } 615 spin_unlock_irq(&pfault_lock); 616 break; 617 default: 618 break; 619 } 620 return NOTIFY_OK; 621 } 622 623 static int __init pfault_irq_init(void) 624 { 625 int rc; 626 627 rc = register_external_irq(EXT_IRQ_CP_SERVICE, pfault_interrupt); 628 if (rc) 629 goto out_extint; 630 rc = pfault_init() == 0 ? 0 : -EOPNOTSUPP; 631 if (rc) 632 goto out_pfault; 633 irq_subclass_register(IRQ_SUBCLASS_SERVICE_SIGNAL); 634 hotcpu_notifier(pfault_cpu_notify, 0); 635 return 0; 636 637 out_pfault: 638 unregister_external_irq(EXT_IRQ_CP_SERVICE, pfault_interrupt); 639 out_extint: 640 pfault_disable = 1; 641 return rc; 642 } 643 early_initcall(pfault_irq_init); 644 645 #endif /* CONFIG_PFAULT */ 646