1 /* 2 * arch/s390/mm/fault.c 3 * 4 * S390 version 5 * Copyright (C) 1999 IBM Deutschland Entwicklung GmbH, IBM Corporation 6 * Author(s): Hartmut Penner (hp@de.ibm.com) 7 * Ulrich Weigand (uweigand@de.ibm.com) 8 * 9 * Derived from "arch/i386/mm/fault.c" 10 * Copyright (C) 1995 Linus Torvalds 11 */ 12 13 #include <linux/kernel_stat.h> 14 #include <linux/perf_event.h> 15 #include <linux/signal.h> 16 #include <linux/sched.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/module.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/system.h> 36 #include <asm/pgtable.h> 37 #include <asm/s390_ext.h> 38 #include <asm/mmu_context.h> 39 #include <asm/compat.h> 40 #include "../kernel/entry.h" 41 42 #ifndef CONFIG_64BIT 43 #define __FAIL_ADDR_MASK 0x7ffff000 44 #define __SUBCODE_MASK 0x0200 45 #define __PF_RES_FIELD 0ULL 46 #else /* CONFIG_64BIT */ 47 #define __FAIL_ADDR_MASK -4096L 48 #define __SUBCODE_MASK 0x0600 49 #define __PF_RES_FIELD 0x8000000000000000ULL 50 #endif /* CONFIG_64BIT */ 51 52 #define VM_FAULT_BADCONTEXT 0x010000 53 #define VM_FAULT_BADMAP 0x020000 54 #define VM_FAULT_BADACCESS 0x040000 55 56 static unsigned long store_indication; 57 58 void fault_init(void) 59 { 60 if (test_facility(2) && test_facility(75)) 61 store_indication = 0xc00; 62 } 63 64 static inline int notify_page_fault(struct pt_regs *regs) 65 { 66 int ret = 0; 67 68 /* kprobe_running() needs smp_processor_id() */ 69 if (kprobes_built_in() && !user_mode(regs)) { 70 preempt_disable(); 71 if (kprobe_running() && kprobe_fault_handler(regs, 14)) 72 ret = 1; 73 preempt_enable(); 74 } 75 return ret; 76 } 77 78 79 /* 80 * Unlock any spinlocks which will prevent us from getting the 81 * message out. 82 */ 83 void bust_spinlocks(int yes) 84 { 85 if (yes) { 86 oops_in_progress = 1; 87 } else { 88 int loglevel_save = console_loglevel; 89 console_unblank(); 90 oops_in_progress = 0; 91 /* 92 * OK, the message is on the console. Now we call printk() 93 * without oops_in_progress set so that printk will give klogd 94 * a poke. Hold onto your hats... 95 */ 96 console_loglevel = 15; 97 printk(" "); 98 console_loglevel = loglevel_save; 99 } 100 } 101 102 /* 103 * Returns the address space associated with the fault. 104 * Returns 0 for kernel space and 1 for user space. 105 */ 106 static inline int user_space_fault(unsigned long trans_exc_code) 107 { 108 /* 109 * The lowest two bits of the translation exception 110 * identification indicate which paging table was used. 111 */ 112 trans_exc_code &= 3; 113 if (trans_exc_code == 2) 114 /* Access via secondary space, set_fs setting decides */ 115 return current->thread.mm_segment.ar4; 116 if (user_mode == HOME_SPACE_MODE) 117 /* User space if the access has been done via home space. */ 118 return trans_exc_code == 3; 119 /* 120 * If the user space is not the home space the kernel runs in home 121 * space. Access via secondary space has already been covered, 122 * access via primary space or access register is from user space 123 * and access via home space is from the kernel. 124 */ 125 return trans_exc_code != 3; 126 } 127 128 static inline void report_user_fault(struct pt_regs *regs, long int_code, 129 int signr, unsigned long address) 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("User process fault: interruption code 0x%lX ", int_code); 138 print_vma_addr(KERN_CONT "in ", regs->psw.addr & PSW_ADDR_INSN); 139 printk("\n"); 140 printk("failing address: %lX\n", address); 141 show_regs(regs); 142 } 143 144 /* 145 * Send SIGSEGV to task. This is an external routine 146 * to keep the stack usage of do_page_fault small. 147 */ 148 static noinline void do_sigsegv(struct pt_regs *regs, long int_code, 149 int si_code, unsigned long trans_exc_code) 150 { 151 struct siginfo si; 152 unsigned long address; 153 154 address = trans_exc_code & __FAIL_ADDR_MASK; 155 current->thread.prot_addr = address; 156 current->thread.trap_no = int_code; 157 report_user_fault(regs, int_code, SIGSEGV, address); 158 si.si_signo = SIGSEGV; 159 si.si_code = si_code; 160 si.si_addr = (void __user *) address; 161 force_sig_info(SIGSEGV, &si, current); 162 } 163 164 static noinline void do_no_context(struct pt_regs *regs, long int_code, 165 unsigned long trans_exc_code) 166 { 167 const struct exception_table_entry *fixup; 168 unsigned long address; 169 170 /* Are we prepared to handle this kernel fault? */ 171 fixup = search_exception_tables(regs->psw.addr & PSW_ADDR_INSN); 172 if (fixup) { 173 regs->psw.addr = fixup->fixup | PSW_ADDR_AMODE; 174 return; 175 } 176 177 /* 178 * Oops. The kernel tried to access some bad page. We'll have to 179 * terminate things with extreme prejudice. 180 */ 181 address = trans_exc_code & __FAIL_ADDR_MASK; 182 if (!user_space_fault(trans_exc_code)) 183 printk(KERN_ALERT "Unable to handle kernel pointer dereference" 184 " at virtual kernel address %p\n", (void *)address); 185 else 186 printk(KERN_ALERT "Unable to handle kernel paging request" 187 " at virtual user address %p\n", (void *)address); 188 189 die("Oops", regs, int_code); 190 do_exit(SIGKILL); 191 } 192 193 static noinline void do_low_address(struct pt_regs *regs, long int_code, 194 unsigned long trans_exc_code) 195 { 196 /* Low-address protection hit in kernel mode means 197 NULL pointer write access in kernel mode. */ 198 if (regs->psw.mask & PSW_MASK_PSTATE) { 199 /* Low-address protection hit in user mode 'cannot happen'. */ 200 die ("Low-address protection", regs, int_code); 201 do_exit(SIGKILL); 202 } 203 204 do_no_context(regs, int_code, trans_exc_code); 205 } 206 207 static noinline void do_sigbus(struct pt_regs *regs, long int_code, 208 unsigned long trans_exc_code) 209 { 210 struct task_struct *tsk = current; 211 unsigned long address; 212 struct siginfo si; 213 214 /* 215 * Send a sigbus, regardless of whether we were in kernel 216 * or user mode. 217 */ 218 address = trans_exc_code & __FAIL_ADDR_MASK; 219 tsk->thread.prot_addr = address; 220 tsk->thread.trap_no = int_code; 221 si.si_signo = SIGBUS; 222 si.si_errno = 0; 223 si.si_code = BUS_ADRERR; 224 si.si_addr = (void __user *) address; 225 force_sig_info(SIGBUS, &si, tsk); 226 } 227 228 #ifdef CONFIG_S390_EXEC_PROTECT 229 static noinline int signal_return(struct pt_regs *regs, long int_code, 230 unsigned long trans_exc_code) 231 { 232 u16 instruction; 233 int rc; 234 235 rc = __get_user(instruction, (u16 __user *) regs->psw.addr); 236 237 if (!rc && instruction == 0x0a77) { 238 clear_tsk_thread_flag(current, TIF_PER_TRAP); 239 if (is_compat_task()) 240 sys32_sigreturn(); 241 else 242 sys_sigreturn(); 243 } else if (!rc && instruction == 0x0aad) { 244 clear_tsk_thread_flag(current, TIF_PER_TRAP); 245 if (is_compat_task()) 246 sys32_rt_sigreturn(); 247 else 248 sys_rt_sigreturn(); 249 } else 250 do_sigsegv(regs, int_code, SEGV_MAPERR, trans_exc_code); 251 return 0; 252 } 253 #endif /* CONFIG_S390_EXEC_PROTECT */ 254 255 static noinline void do_fault_error(struct pt_regs *regs, long int_code, 256 unsigned long trans_exc_code, int fault) 257 { 258 int si_code; 259 260 switch (fault) { 261 case VM_FAULT_BADACCESS: 262 #ifdef CONFIG_S390_EXEC_PROTECT 263 if ((regs->psw.mask & PSW_MASK_ASC) == PSW_ASC_SECONDARY && 264 (trans_exc_code & 3) == 0) { 265 signal_return(regs, int_code, trans_exc_code); 266 break; 267 } 268 #endif /* CONFIG_S390_EXEC_PROTECT */ 269 case VM_FAULT_BADMAP: 270 /* Bad memory access. Check if it is kernel or user space. */ 271 if (regs->psw.mask & PSW_MASK_PSTATE) { 272 /* User mode accesses just cause a SIGSEGV */ 273 si_code = (fault == VM_FAULT_BADMAP) ? 274 SEGV_MAPERR : SEGV_ACCERR; 275 do_sigsegv(regs, int_code, si_code, trans_exc_code); 276 return; 277 } 278 case VM_FAULT_BADCONTEXT: 279 do_no_context(regs, int_code, trans_exc_code); 280 break; 281 default: /* fault & VM_FAULT_ERROR */ 282 if (fault & VM_FAULT_OOM) 283 pagefault_out_of_memory(); 284 else if (fault & VM_FAULT_SIGBUS) { 285 /* Kernel mode? Handle exceptions or die */ 286 if (!(regs->psw.mask & PSW_MASK_PSTATE)) 287 do_no_context(regs, int_code, trans_exc_code); 288 else 289 do_sigbus(regs, int_code, trans_exc_code); 290 } else 291 BUG(); 292 break; 293 } 294 } 295 296 /* 297 * This routine handles page faults. It determines the address, 298 * and the problem, and then passes it off to one of the appropriate 299 * routines. 300 * 301 * interruption code (int_code): 302 * 04 Protection -> Write-Protection (suprression) 303 * 10 Segment translation -> Not present (nullification) 304 * 11 Page translation -> Not present (nullification) 305 * 3b Region third trans. -> Not present (nullification) 306 */ 307 static inline int do_exception(struct pt_regs *regs, int access, 308 unsigned long trans_exc_code) 309 { 310 struct task_struct *tsk; 311 struct mm_struct *mm; 312 struct vm_area_struct *vma; 313 unsigned long address; 314 int fault, write; 315 316 if (notify_page_fault(regs)) 317 return 0; 318 319 tsk = current; 320 mm = tsk->mm; 321 322 /* 323 * Verify that the fault happened in user space, that 324 * we are not in an interrupt and that there is a 325 * user context. 326 */ 327 fault = VM_FAULT_BADCONTEXT; 328 if (unlikely(!user_space_fault(trans_exc_code) || in_atomic() || !mm)) 329 goto out; 330 331 address = trans_exc_code & __FAIL_ADDR_MASK; 332 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, 0, regs, address); 333 down_read(&mm->mmap_sem); 334 335 fault = VM_FAULT_BADMAP; 336 vma = find_vma(mm, address); 337 if (!vma) 338 goto out_up; 339 340 if (unlikely(vma->vm_start > address)) { 341 if (!(vma->vm_flags & VM_GROWSDOWN)) 342 goto out_up; 343 if (expand_stack(vma, address)) 344 goto out_up; 345 } 346 347 /* 348 * Ok, we have a good vm_area for this memory access, so 349 * we can handle it.. 350 */ 351 fault = VM_FAULT_BADACCESS; 352 if (unlikely(!(vma->vm_flags & access))) 353 goto out_up; 354 355 if (is_vm_hugetlb_page(vma)) 356 address &= HPAGE_MASK; 357 /* 358 * If for any reason at all we couldn't handle the fault, 359 * make sure we exit gracefully rather than endlessly redo 360 * the fault. 361 */ 362 write = (access == VM_WRITE || 363 (trans_exc_code & store_indication) == 0x400) ? 364 FAULT_FLAG_WRITE : 0; 365 fault = handle_mm_fault(mm, vma, address, write); 366 if (unlikely(fault & VM_FAULT_ERROR)) 367 goto out_up; 368 369 if (fault & VM_FAULT_MAJOR) { 370 tsk->maj_flt++; 371 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, 0, 372 regs, address); 373 } else { 374 tsk->min_flt++; 375 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, 0, 376 regs, address); 377 } 378 /* 379 * The instruction that caused the program check will 380 * be repeated. Don't signal single step via SIGTRAP. 381 */ 382 clear_tsk_thread_flag(tsk, TIF_PER_TRAP); 383 fault = 0; 384 out_up: 385 up_read(&mm->mmap_sem); 386 out: 387 return fault; 388 } 389 390 void __kprobes do_protection_exception(struct pt_regs *regs, long pgm_int_code, 391 unsigned long trans_exc_code) 392 { 393 int fault; 394 395 /* Protection exception is suppressing, decrement psw address. */ 396 regs->psw.addr -= (pgm_int_code >> 16); 397 /* 398 * Check for low-address protection. This needs to be treated 399 * as a special case because the translation exception code 400 * field is not guaranteed to contain valid data in this case. 401 */ 402 if (unlikely(!(trans_exc_code & 4))) { 403 do_low_address(regs, pgm_int_code, trans_exc_code); 404 return; 405 } 406 fault = do_exception(regs, VM_WRITE, trans_exc_code); 407 if (unlikely(fault)) 408 do_fault_error(regs, 4, trans_exc_code, fault); 409 } 410 411 void __kprobes do_dat_exception(struct pt_regs *regs, long pgm_int_code, 412 unsigned long trans_exc_code) 413 { 414 int access, fault; 415 416 access = VM_READ | VM_EXEC | VM_WRITE; 417 #ifdef CONFIG_S390_EXEC_PROTECT 418 if ((regs->psw.mask & PSW_MASK_ASC) == PSW_ASC_SECONDARY && 419 (trans_exc_code & 3) == 0) 420 access = VM_EXEC; 421 #endif 422 fault = do_exception(regs, access, trans_exc_code); 423 if (unlikely(fault)) 424 do_fault_error(regs, pgm_int_code & 255, trans_exc_code, fault); 425 } 426 427 #ifdef CONFIG_64BIT 428 void __kprobes do_asce_exception(struct pt_regs *regs, long pgm_int_code, 429 unsigned long trans_exc_code) 430 { 431 struct mm_struct *mm = current->mm; 432 struct vm_area_struct *vma; 433 434 if (unlikely(!user_space_fault(trans_exc_code) || in_atomic() || !mm)) 435 goto no_context; 436 437 down_read(&mm->mmap_sem); 438 vma = find_vma(mm, trans_exc_code & __FAIL_ADDR_MASK); 439 up_read(&mm->mmap_sem); 440 441 if (vma) { 442 update_mm(mm, current); 443 return; 444 } 445 446 /* User mode accesses just cause a SIGSEGV */ 447 if (regs->psw.mask & PSW_MASK_PSTATE) { 448 do_sigsegv(regs, pgm_int_code, SEGV_MAPERR, trans_exc_code); 449 return; 450 } 451 452 no_context: 453 do_no_context(regs, pgm_int_code, trans_exc_code); 454 } 455 #endif 456 457 int __handle_fault(unsigned long uaddr, unsigned long pgm_int_code, int write) 458 { 459 struct pt_regs regs; 460 int access, fault; 461 462 regs.psw.mask = psw_kernel_bits; 463 if (!irqs_disabled()) 464 regs.psw.mask |= PSW_MASK_IO | PSW_MASK_EXT; 465 regs.psw.addr = (unsigned long) __builtin_return_address(0); 466 regs.psw.addr |= PSW_ADDR_AMODE; 467 uaddr &= PAGE_MASK; 468 access = write ? VM_WRITE : VM_READ; 469 fault = do_exception(®s, access, uaddr | 2); 470 if (unlikely(fault)) { 471 if (fault & VM_FAULT_OOM) { 472 pagefault_out_of_memory(); 473 fault = 0; 474 } else if (fault & VM_FAULT_SIGBUS) 475 do_sigbus(®s, pgm_int_code, uaddr); 476 } 477 return fault ? -EFAULT : 0; 478 } 479 480 #ifdef CONFIG_PFAULT 481 /* 482 * 'pfault' pseudo page faults routines. 483 */ 484 static int pfault_disable; 485 486 static int __init nopfault(char *str) 487 { 488 pfault_disable = 1; 489 return 1; 490 } 491 492 __setup("nopfault", nopfault); 493 494 typedef struct { 495 __u16 refdiagc; 496 __u16 reffcode; 497 __u16 refdwlen; 498 __u16 refversn; 499 __u64 refgaddr; 500 __u64 refselmk; 501 __u64 refcmpmk; 502 __u64 reserved; 503 } __attribute__ ((packed, aligned(8))) pfault_refbk_t; 504 505 int pfault_init(void) 506 { 507 pfault_refbk_t refbk = 508 { 0x258, 0, 5, 2, __LC_CURRENT, 1ULL << 48, 1ULL << 48, 509 __PF_RES_FIELD }; 510 int rc; 511 512 if (!MACHINE_IS_VM || pfault_disable) 513 return -1; 514 asm volatile( 515 " diag %1,%0,0x258\n" 516 "0: j 2f\n" 517 "1: la %0,8\n" 518 "2:\n" 519 EX_TABLE(0b,1b) 520 : "=d" (rc) : "a" (&refbk), "m" (refbk) : "cc"); 521 __ctl_set_bit(0, 9); 522 return rc; 523 } 524 525 void pfault_fini(void) 526 { 527 pfault_refbk_t refbk = 528 { 0x258, 1, 5, 2, 0ULL, 0ULL, 0ULL, 0ULL }; 529 530 if (!MACHINE_IS_VM || pfault_disable) 531 return; 532 __ctl_clear_bit(0,9); 533 asm volatile( 534 " diag %0,0,0x258\n" 535 "0:\n" 536 EX_TABLE(0b,0b) 537 : : "a" (&refbk), "m" (refbk) : "cc"); 538 } 539 540 static void pfault_interrupt(unsigned int ext_int_code, 541 unsigned int param32, unsigned long param64) 542 { 543 struct task_struct *tsk; 544 __u16 subcode; 545 546 kstat_cpu(smp_processor_id()).irqs[EXTINT_PFL]++; 547 /* 548 * Get the external interruption subcode & pfault 549 * initial/completion signal bit. VM stores this 550 * in the 'cpu address' field associated with the 551 * external interrupt. 552 */ 553 subcode = ext_int_code >> 16; 554 if ((subcode & 0xff00) != __SUBCODE_MASK) 555 return; 556 557 /* 558 * Get the token (= address of the task structure of the affected task). 559 */ 560 #ifdef CONFIG_64BIT 561 tsk = *(struct task_struct **) param64; 562 #else 563 tsk = *(struct task_struct **) param32; 564 #endif 565 566 if (subcode & 0x0080) { 567 /* signal bit is set -> a page has been swapped in by VM */ 568 if (xchg(&tsk->thread.pfault_wait, -1) != 0) { 569 /* Initial interrupt was faster than the completion 570 * interrupt. pfault_wait is valid. Set pfault_wait 571 * back to zero and wake up the process. This can 572 * safely be done because the task is still sleeping 573 * and can't produce new pfaults. */ 574 tsk->thread.pfault_wait = 0; 575 wake_up_process(tsk); 576 put_task_struct(tsk); 577 } 578 } else { 579 /* signal bit not set -> a real page is missing. */ 580 get_task_struct(tsk); 581 set_task_state(tsk, TASK_UNINTERRUPTIBLE); 582 if (xchg(&tsk->thread.pfault_wait, 1) != 0) { 583 /* Completion interrupt was faster than the initial 584 * interrupt (swapped in a -1 for pfault_wait). Set 585 * pfault_wait back to zero and exit. This can be 586 * done safely because tsk is running in kernel 587 * mode and can't produce new pfaults. */ 588 tsk->thread.pfault_wait = 0; 589 set_task_state(tsk, TASK_RUNNING); 590 put_task_struct(tsk); 591 } else 592 set_tsk_need_resched(tsk); 593 } 594 } 595 596 static int __init pfault_irq_init(void) 597 { 598 int rc; 599 600 if (!MACHINE_IS_VM) 601 return 0; 602 /* 603 * Try to get pfault pseudo page faults going. 604 */ 605 rc = register_external_interrupt(0x2603, pfault_interrupt); 606 if (rc) { 607 pfault_disable = 1; 608 return rc; 609 } 610 if (pfault_init() == 0) 611 return 0; 612 613 /* Tough luck, no pfault. */ 614 pfault_disable = 1; 615 unregister_external_interrupt(0x2603, pfault_interrupt); 616 return 0; 617 } 618 early_initcall(pfault_irq_init); 619 620 #endif 621