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/perf_counter.h> 14 #include <linux/signal.h> 15 #include <linux/sched.h> 16 #include <linux/kernel.h> 17 #include <linux/errno.h> 18 #include <linux/string.h> 19 #include <linux/types.h> 20 #include <linux/ptrace.h> 21 #include <linux/mman.h> 22 #include <linux/mm.h> 23 #include <linux/compat.h> 24 #include <linux/smp.h> 25 #include <linux/kdebug.h> 26 #include <linux/init.h> 27 #include <linux/console.h> 28 #include <linux/module.h> 29 #include <linux/hardirq.h> 30 #include <linux/kprobes.h> 31 #include <linux/uaccess.h> 32 #include <linux/hugetlb.h> 33 #include <asm/system.h> 34 #include <asm/pgtable.h> 35 #include <asm/s390_ext.h> 36 #include <asm/mmu_context.h> 37 #include "../kernel/entry.h" 38 39 #ifndef CONFIG_64BIT 40 #define __FAIL_ADDR_MASK 0x7ffff000 41 #define __FIXUP_MASK 0x7fffffff 42 #define __SUBCODE_MASK 0x0200 43 #define __PF_RES_FIELD 0ULL 44 #else /* CONFIG_64BIT */ 45 #define __FAIL_ADDR_MASK -4096L 46 #define __FIXUP_MASK ~0L 47 #define __SUBCODE_MASK 0x0600 48 #define __PF_RES_FIELD 0x8000000000000000ULL 49 #endif /* CONFIG_64BIT */ 50 51 #ifdef CONFIG_SYSCTL 52 extern int sysctl_userprocess_debug; 53 #endif 54 55 #ifdef CONFIG_KPROBES 56 static inline int notify_page_fault(struct pt_regs *regs, long err) 57 { 58 int ret = 0; 59 60 /* kprobe_running() needs smp_processor_id() */ 61 if (!user_mode(regs)) { 62 preempt_disable(); 63 if (kprobe_running() && kprobe_fault_handler(regs, 14)) 64 ret = 1; 65 preempt_enable(); 66 } 67 68 return ret; 69 } 70 #else 71 static inline int notify_page_fault(struct pt_regs *regs, long err) 72 { 73 return 0; 74 } 75 #endif 76 77 78 /* 79 * Unlock any spinlocks which will prevent us from getting the 80 * message out. 81 */ 82 void bust_spinlocks(int yes) 83 { 84 if (yes) { 85 oops_in_progress = 1; 86 } else { 87 int loglevel_save = console_loglevel; 88 console_unblank(); 89 oops_in_progress = 0; 90 /* 91 * OK, the message is on the console. Now we call printk() 92 * without oops_in_progress set so that printk will give klogd 93 * a poke. Hold onto your hats... 94 */ 95 console_loglevel = 15; 96 printk(" "); 97 console_loglevel = loglevel_save; 98 } 99 } 100 101 /* 102 * Returns the address space associated with the fault. 103 * Returns 0 for kernel space, 1 for user space and 104 * 2 for code execution in user space with noexec=on. 105 */ 106 static inline int check_space(struct task_struct *tsk) 107 { 108 /* 109 * The lowest two bits of S390_lowcore.trans_exc_code 110 * indicate which paging table was used. 111 */ 112 int desc = S390_lowcore.trans_exc_code & 3; 113 114 if (desc == 3) /* Home Segment Table Descriptor */ 115 return switch_amode == 0; 116 if (desc == 2) /* Secondary Segment Table Descriptor */ 117 return tsk->thread.mm_segment.ar4; 118 #ifdef CONFIG_S390_SWITCH_AMODE 119 if (unlikely(desc == 1)) { /* STD determined via access register */ 120 /* %a0 always indicates primary space. */ 121 if (S390_lowcore.exc_access_id != 0) { 122 save_access_regs(tsk->thread.acrs); 123 /* 124 * An alet of 0 indicates primary space. 125 * An alet of 1 indicates secondary space. 126 * Any other alet values generate an 127 * alen-translation exception. 128 */ 129 if (tsk->thread.acrs[S390_lowcore.exc_access_id]) 130 return tsk->thread.mm_segment.ar4; 131 } 132 } 133 #endif 134 /* Primary Segment Table Descriptor */ 135 return switch_amode << s390_noexec; 136 } 137 138 /* 139 * Send SIGSEGV to task. This is an external routine 140 * to keep the stack usage of do_page_fault small. 141 */ 142 static void do_sigsegv(struct pt_regs *regs, unsigned long error_code, 143 int si_code, unsigned long address) 144 { 145 struct siginfo si; 146 147 #if defined(CONFIG_SYSCTL) || defined(CONFIG_PROCESS_DEBUG) 148 #if defined(CONFIG_SYSCTL) 149 if (sysctl_userprocess_debug) 150 #endif 151 { 152 printk("User process fault: interruption code 0x%lX\n", 153 error_code); 154 printk("failing address: %lX\n", address); 155 show_regs(regs); 156 } 157 #endif 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 void do_no_context(struct pt_regs *regs, unsigned long error_code, 165 unsigned long address) 166 { 167 const struct exception_table_entry *fixup; 168 169 /* Are we prepared to handle this kernel fault? */ 170 fixup = search_exception_tables(regs->psw.addr & __FIXUP_MASK); 171 if (fixup) { 172 regs->psw.addr = fixup->fixup | PSW_ADDR_AMODE; 173 return; 174 } 175 176 /* 177 * Oops. The kernel tried to access some bad page. We'll have to 178 * terminate things with extreme prejudice. 179 */ 180 if (check_space(current) == 0) 181 printk(KERN_ALERT "Unable to handle kernel pointer dereference" 182 " at virtual kernel address %p\n", (void *)address); 183 else 184 printk(KERN_ALERT "Unable to handle kernel paging request" 185 " at virtual user address %p\n", (void *)address); 186 187 die("Oops", regs, error_code); 188 do_exit(SIGKILL); 189 } 190 191 static void do_low_address(struct pt_regs *regs, unsigned long error_code) 192 { 193 /* Low-address protection hit in kernel mode means 194 NULL pointer write access in kernel mode. */ 195 if (regs->psw.mask & PSW_MASK_PSTATE) { 196 /* Low-address protection hit in user mode 'cannot happen'. */ 197 die ("Low-address protection", regs, error_code); 198 do_exit(SIGKILL); 199 } 200 201 do_no_context(regs, error_code, 0); 202 } 203 204 static void do_sigbus(struct pt_regs *regs, unsigned long error_code, 205 unsigned long address) 206 { 207 struct task_struct *tsk = current; 208 struct mm_struct *mm = tsk->mm; 209 210 up_read(&mm->mmap_sem); 211 /* 212 * Send a sigbus, regardless of whether we were in kernel 213 * or user mode. 214 */ 215 tsk->thread.prot_addr = address; 216 tsk->thread.trap_no = error_code; 217 force_sig(SIGBUS, tsk); 218 219 /* Kernel mode? Handle exceptions or die */ 220 if (!(regs->psw.mask & PSW_MASK_PSTATE)) 221 do_no_context(regs, error_code, address); 222 } 223 224 #ifdef CONFIG_S390_EXEC_PROTECT 225 static int signal_return(struct mm_struct *mm, struct pt_regs *regs, 226 unsigned long address, unsigned long error_code) 227 { 228 u16 instruction; 229 int rc; 230 #ifdef CONFIG_COMPAT 231 int compat; 232 #endif 233 234 pagefault_disable(); 235 rc = __get_user(instruction, (u16 __user *) regs->psw.addr); 236 pagefault_enable(); 237 if (rc) 238 return -EFAULT; 239 240 up_read(&mm->mmap_sem); 241 clear_tsk_thread_flag(current, TIF_SINGLE_STEP); 242 #ifdef CONFIG_COMPAT 243 compat = is_compat_task(); 244 if (compat && instruction == 0x0a77) 245 sys32_sigreturn(); 246 else if (compat && instruction == 0x0aad) 247 sys32_rt_sigreturn(); 248 else 249 #endif 250 if (instruction == 0x0a77) 251 sys_sigreturn(); 252 else if (instruction == 0x0aad) 253 sys_rt_sigreturn(); 254 else { 255 current->thread.prot_addr = address; 256 current->thread.trap_no = error_code; 257 do_sigsegv(regs, error_code, SEGV_MAPERR, address); 258 } 259 return 0; 260 } 261 #endif /* CONFIG_S390_EXEC_PROTECT */ 262 263 /* 264 * This routine handles page faults. It determines the address, 265 * and the problem, and then passes it off to one of the appropriate 266 * routines. 267 * 268 * error_code: 269 * 04 Protection -> Write-Protection (suprression) 270 * 10 Segment translation -> Not present (nullification) 271 * 11 Page translation -> Not present (nullification) 272 * 3b Region third trans. -> Not present (nullification) 273 */ 274 static inline void 275 do_exception(struct pt_regs *regs, unsigned long error_code, int write) 276 { 277 struct task_struct *tsk; 278 struct mm_struct *mm; 279 struct vm_area_struct *vma; 280 unsigned long address; 281 int space; 282 int si_code; 283 int fault; 284 285 if (notify_page_fault(regs, error_code)) 286 return; 287 288 tsk = current; 289 mm = tsk->mm; 290 291 /* get the failing address and the affected space */ 292 address = S390_lowcore.trans_exc_code & __FAIL_ADDR_MASK; 293 space = check_space(tsk); 294 295 /* 296 * Verify that the fault happened in user space, that 297 * we are not in an interrupt and that there is a 298 * user context. 299 */ 300 if (unlikely(space == 0 || in_atomic() || !mm)) 301 goto no_context; 302 303 /* 304 * When we get here, the fault happened in the current 305 * task's user address space, so we can switch on the 306 * interrupts again and then search the VMAs 307 */ 308 local_irq_enable(); 309 perf_swcounter_event(PERF_COUNT_SW_PAGE_FAULTS, 1, 0, regs, address); 310 down_read(&mm->mmap_sem); 311 312 si_code = SEGV_MAPERR; 313 vma = find_vma(mm, address); 314 if (!vma) 315 goto bad_area; 316 317 #ifdef CONFIG_S390_EXEC_PROTECT 318 if (unlikely((space == 2) && !(vma->vm_flags & VM_EXEC))) 319 if (!signal_return(mm, regs, address, error_code)) 320 /* 321 * signal_return() has done an up_read(&mm->mmap_sem) 322 * if it returns 0. 323 */ 324 return; 325 #endif 326 327 if (vma->vm_start <= address) 328 goto good_area; 329 if (!(vma->vm_flags & VM_GROWSDOWN)) 330 goto bad_area; 331 if (expand_stack(vma, address)) 332 goto bad_area; 333 /* 334 * Ok, we have a good vm_area for this memory access, so 335 * we can handle it.. 336 */ 337 good_area: 338 si_code = SEGV_ACCERR; 339 if (!write) { 340 /* page not present, check vm flags */ 341 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))) 342 goto bad_area; 343 } else { 344 if (!(vma->vm_flags & VM_WRITE)) 345 goto bad_area; 346 } 347 348 if (is_vm_hugetlb_page(vma)) 349 address &= HPAGE_MASK; 350 /* 351 * If for any reason at all we couldn't handle the fault, 352 * make sure we exit gracefully rather than endlessly redo 353 * the fault. 354 */ 355 fault = handle_mm_fault(mm, vma, address, write ? FAULT_FLAG_WRITE : 0); 356 if (unlikely(fault & VM_FAULT_ERROR)) { 357 if (fault & VM_FAULT_OOM) { 358 up_read(&mm->mmap_sem); 359 pagefault_out_of_memory(); 360 return; 361 } else if (fault & VM_FAULT_SIGBUS) { 362 do_sigbus(regs, error_code, address); 363 return; 364 } 365 BUG(); 366 } 367 if (fault & VM_FAULT_MAJOR) { 368 tsk->maj_flt++; 369 perf_swcounter_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, 0, 370 regs, address); 371 } else { 372 tsk->min_flt++; 373 perf_swcounter_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, 0, 374 regs, address); 375 } 376 up_read(&mm->mmap_sem); 377 /* 378 * The instruction that caused the program check will 379 * be repeated. Don't signal single step via SIGTRAP. 380 */ 381 clear_tsk_thread_flag(tsk, TIF_SINGLE_STEP); 382 return; 383 384 /* 385 * Something tried to access memory that isn't in our memory map.. 386 * Fix it, but check if it's kernel or user first.. 387 */ 388 bad_area: 389 up_read(&mm->mmap_sem); 390 391 /* User mode accesses just cause a SIGSEGV */ 392 if (regs->psw.mask & PSW_MASK_PSTATE) { 393 tsk->thread.prot_addr = address; 394 tsk->thread.trap_no = error_code; 395 do_sigsegv(regs, error_code, si_code, address); 396 return; 397 } 398 399 no_context: 400 do_no_context(regs, error_code, address); 401 } 402 403 void __kprobes do_protection_exception(struct pt_regs *regs, 404 long error_code) 405 { 406 /* Protection exception is supressing, decrement psw address. */ 407 regs->psw.addr -= (error_code >> 16); 408 /* 409 * Check for low-address protection. This needs to be treated 410 * as a special case because the translation exception code 411 * field is not guaranteed to contain valid data in this case. 412 */ 413 if (unlikely(!(S390_lowcore.trans_exc_code & 4))) { 414 do_low_address(regs, error_code); 415 return; 416 } 417 do_exception(regs, 4, 1); 418 } 419 420 void __kprobes do_dat_exception(struct pt_regs *regs, long error_code) 421 { 422 do_exception(regs, error_code & 0xff, 0); 423 } 424 425 #ifdef CONFIG_64BIT 426 void __kprobes do_asce_exception(struct pt_regs *regs, unsigned long error_code) 427 { 428 struct mm_struct *mm; 429 struct vm_area_struct *vma; 430 unsigned long address; 431 int space; 432 433 mm = current->mm; 434 address = S390_lowcore.trans_exc_code & __FAIL_ADDR_MASK; 435 space = check_space(current); 436 437 if (unlikely(space == 0 || in_atomic() || !mm)) 438 goto no_context; 439 440 local_irq_enable(); 441 442 down_read(&mm->mmap_sem); 443 vma = find_vma(mm, address); 444 up_read(&mm->mmap_sem); 445 446 if (vma) { 447 update_mm(mm, current); 448 return; 449 } 450 451 /* User mode accesses just cause a SIGSEGV */ 452 if (regs->psw.mask & PSW_MASK_PSTATE) { 453 current->thread.prot_addr = address; 454 current->thread.trap_no = error_code; 455 do_sigsegv(regs, error_code, SEGV_MAPERR, address); 456 return; 457 } 458 459 no_context: 460 do_no_context(regs, error_code, address); 461 } 462 #endif 463 464 #ifdef CONFIG_PFAULT 465 /* 466 * 'pfault' pseudo page faults routines. 467 */ 468 static ext_int_info_t ext_int_pfault; 469 static int pfault_disable = 0; 470 471 static int __init nopfault(char *str) 472 { 473 pfault_disable = 1; 474 return 1; 475 } 476 477 __setup("nopfault", nopfault); 478 479 typedef struct { 480 __u16 refdiagc; 481 __u16 reffcode; 482 __u16 refdwlen; 483 __u16 refversn; 484 __u64 refgaddr; 485 __u64 refselmk; 486 __u64 refcmpmk; 487 __u64 reserved; 488 } __attribute__ ((packed, aligned(8))) pfault_refbk_t; 489 490 int pfault_init(void) 491 { 492 pfault_refbk_t refbk = 493 { 0x258, 0, 5, 2, __LC_CURRENT, 1ULL << 48, 1ULL << 48, 494 __PF_RES_FIELD }; 495 int rc; 496 497 if (!MACHINE_IS_VM || pfault_disable) 498 return -1; 499 asm volatile( 500 " diag %1,%0,0x258\n" 501 "0: j 2f\n" 502 "1: la %0,8\n" 503 "2:\n" 504 EX_TABLE(0b,1b) 505 : "=d" (rc) : "a" (&refbk), "m" (refbk) : "cc"); 506 __ctl_set_bit(0, 9); 507 return rc; 508 } 509 510 void pfault_fini(void) 511 { 512 pfault_refbk_t refbk = 513 { 0x258, 1, 5, 2, 0ULL, 0ULL, 0ULL, 0ULL }; 514 515 if (!MACHINE_IS_VM || pfault_disable) 516 return; 517 __ctl_clear_bit(0,9); 518 asm volatile( 519 " diag %0,0,0x258\n" 520 "0:\n" 521 EX_TABLE(0b,0b) 522 : : "a" (&refbk), "m" (refbk) : "cc"); 523 } 524 525 static void pfault_interrupt(__u16 error_code) 526 { 527 struct task_struct *tsk; 528 __u16 subcode; 529 530 /* 531 * Get the external interruption subcode & pfault 532 * initial/completion signal bit. VM stores this 533 * in the 'cpu address' field associated with the 534 * external interrupt. 535 */ 536 subcode = S390_lowcore.cpu_addr; 537 if ((subcode & 0xff00) != __SUBCODE_MASK) 538 return; 539 540 /* 541 * Get the token (= address of the task structure of the affected task). 542 */ 543 tsk = *(struct task_struct **) __LC_PFAULT_INTPARM; 544 545 if (subcode & 0x0080) { 546 /* signal bit is set -> a page has been swapped in by VM */ 547 if (xchg(&tsk->thread.pfault_wait, -1) != 0) { 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 wake_up_process(tsk); 555 put_task_struct(tsk); 556 } 557 } else { 558 /* signal bit not set -> a real page is missing. */ 559 get_task_struct(tsk); 560 set_task_state(tsk, TASK_UNINTERRUPTIBLE); 561 if (xchg(&tsk->thread.pfault_wait, 1) != 0) { 562 /* Completion interrupt was faster than the initial 563 * interrupt (swapped in a -1 for pfault_wait). Set 564 * pfault_wait back to zero and exit. This can be 565 * done safely because tsk is running in kernel 566 * mode and can't produce new pfaults. */ 567 tsk->thread.pfault_wait = 0; 568 set_task_state(tsk, TASK_RUNNING); 569 put_task_struct(tsk); 570 } else 571 set_tsk_need_resched(tsk); 572 } 573 } 574 575 void __init pfault_irq_init(void) 576 { 577 if (!MACHINE_IS_VM) 578 return; 579 580 /* 581 * Try to get pfault pseudo page faults going. 582 */ 583 if (register_early_external_interrupt(0x2603, pfault_interrupt, 584 &ext_int_pfault) != 0) 585 panic("Couldn't request external interrupt 0x2603"); 586 587 if (pfault_init() == 0) 588 return; 589 590 /* Tough luck, no pfault. */ 591 pfault_disable = 1; 592 unregister_early_external_interrupt(0x2603, pfault_interrupt, 593 &ext_int_pfault); 594 } 595 #endif 596