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/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/smp.h> 23 #include <linux/smp_lock.h> 24 #include <linux/init.h> 25 #include <linux/console.h> 26 #include <linux/module.h> 27 #include <linux/hardirq.h> 28 #include <linux/kprobes.h> 29 30 #include <asm/system.h> 31 #include <asm/uaccess.h> 32 #include <asm/pgtable.h> 33 #include <asm/kdebug.h> 34 35 #ifndef CONFIG_64BIT 36 #define __FAIL_ADDR_MASK 0x7ffff000 37 #define __FIXUP_MASK 0x7fffffff 38 #define __SUBCODE_MASK 0x0200 39 #define __PF_RES_FIELD 0ULL 40 #else /* CONFIG_64BIT */ 41 #define __FAIL_ADDR_MASK -4096L 42 #define __FIXUP_MASK ~0L 43 #define __SUBCODE_MASK 0x0600 44 #define __PF_RES_FIELD 0x8000000000000000ULL 45 #endif /* CONFIG_64BIT */ 46 47 #ifdef CONFIG_SYSCTL 48 extern int sysctl_userprocess_debug; 49 #endif 50 51 extern void die(const char *,struct pt_regs *,long); 52 53 #ifdef CONFIG_KPROBES 54 ATOMIC_NOTIFIER_HEAD(notify_page_fault_chain); 55 int register_page_fault_notifier(struct notifier_block *nb) 56 { 57 return atomic_notifier_chain_register(¬ify_page_fault_chain, nb); 58 } 59 60 int unregister_page_fault_notifier(struct notifier_block *nb) 61 { 62 return atomic_notifier_chain_unregister(¬ify_page_fault_chain, nb); 63 } 64 65 static inline int notify_page_fault(enum die_val val, const char *str, 66 struct pt_regs *regs, long err, int trap, int sig) 67 { 68 struct die_args args = { 69 .regs = regs, 70 .str = str, 71 .err = err, 72 .trapnr = trap, 73 .signr = sig 74 }; 75 return atomic_notifier_call_chain(¬ify_page_fault_chain, val, &args); 76 } 77 #else 78 static inline int notify_page_fault(enum die_val val, const char *str, 79 struct pt_regs *regs, long err, int trap, int sig) 80 { 81 return NOTIFY_DONE; 82 } 83 #endif 84 85 extern spinlock_t timerlist_lock; 86 87 /* 88 * Unlock any spinlocks which will prevent us from getting the 89 * message out (timerlist_lock is acquired through the 90 * console unblank code) 91 */ 92 void bust_spinlocks(int yes) 93 { 94 if (yes) { 95 oops_in_progress = 1; 96 } else { 97 int loglevel_save = console_loglevel; 98 console_unblank(); 99 oops_in_progress = 0; 100 /* 101 * OK, the message is on the console. Now we call printk() 102 * without oops_in_progress set so that printk will give klogd 103 * a poke. Hold onto your hats... 104 */ 105 console_loglevel = 15; 106 printk(" "); 107 console_loglevel = loglevel_save; 108 } 109 } 110 111 /* 112 * Check which address space is addressed by the access 113 * register in S390_lowcore.exc_access_id. 114 * Returns 1 for user space and 0 for kernel space. 115 */ 116 static int __check_access_register(struct pt_regs *regs, int error_code) 117 { 118 int areg = S390_lowcore.exc_access_id; 119 120 if (areg == 0) 121 /* Access via access register 0 -> kernel address */ 122 return 0; 123 save_access_regs(current->thread.acrs); 124 if (regs && areg < NUM_ACRS && current->thread.acrs[areg] <= 1) 125 /* 126 * access register contains 0 -> kernel address, 127 * access register contains 1 -> user space address 128 */ 129 return current->thread.acrs[areg]; 130 131 /* Something unhealthy was done with the access registers... */ 132 die("page fault via unknown access register", regs, error_code); 133 do_exit(SIGKILL); 134 return 0; 135 } 136 137 /* 138 * Check which address space the address belongs to. 139 * Returns 1 for user space and 0 for kernel space. 140 */ 141 static inline int check_user_space(struct pt_regs *regs, int error_code) 142 { 143 /* 144 * The lowest two bits of S390_lowcore.trans_exc_code indicate 145 * which paging table was used: 146 * 0: Primary Segment Table Descriptor 147 * 1: STD determined via access register 148 * 2: Secondary Segment Table Descriptor 149 * 3: Home Segment Table Descriptor 150 */ 151 int descriptor = S390_lowcore.trans_exc_code & 3; 152 if (unlikely(descriptor == 1)) 153 return __check_access_register(regs, error_code); 154 if (descriptor == 2) 155 return current->thread.mm_segment.ar4; 156 return descriptor != 0; 157 } 158 159 /* 160 * Send SIGSEGV to task. This is an external routine 161 * to keep the stack usage of do_page_fault small. 162 */ 163 static void do_sigsegv(struct pt_regs *regs, unsigned long error_code, 164 int si_code, unsigned long address) 165 { 166 struct siginfo si; 167 168 #if defined(CONFIG_SYSCTL) || defined(CONFIG_PROCESS_DEBUG) 169 #if defined(CONFIG_SYSCTL) 170 if (sysctl_userprocess_debug) 171 #endif 172 { 173 printk("User process fault: interruption code 0x%lX\n", 174 error_code); 175 printk("failing address: %lX\n", address); 176 show_regs(regs); 177 } 178 #endif 179 si.si_signo = SIGSEGV; 180 si.si_code = si_code; 181 si.si_addr = (void __user *) address; 182 force_sig_info(SIGSEGV, &si, current); 183 } 184 185 /* 186 * This routine handles page faults. It determines the address, 187 * and the problem, and then passes it off to one of the appropriate 188 * routines. 189 * 190 * error_code: 191 * 04 Protection -> Write-Protection (suprression) 192 * 10 Segment translation -> Not present (nullification) 193 * 11 Page translation -> Not present (nullification) 194 * 3b Region third trans. -> Not present (nullification) 195 */ 196 static inline void __kprobes 197 do_exception(struct pt_regs *regs, unsigned long error_code, int is_protection) 198 { 199 struct task_struct *tsk; 200 struct mm_struct *mm; 201 struct vm_area_struct * vma; 202 unsigned long address; 203 int user_address; 204 const struct exception_table_entry *fixup; 205 int si_code = SEGV_MAPERR; 206 207 tsk = current; 208 mm = tsk->mm; 209 210 if (notify_page_fault(DIE_PAGE_FAULT, "page fault", regs, error_code, 14, 211 SIGSEGV) == NOTIFY_STOP) 212 return; 213 214 /* 215 * Check for low-address protection. This needs to be treated 216 * as a special case because the translation exception code 217 * field is not guaranteed to contain valid data in this case. 218 */ 219 if (is_protection && !(S390_lowcore.trans_exc_code & 4)) { 220 221 /* Low-address protection hit in kernel mode means 222 NULL pointer write access in kernel mode. */ 223 if (!(regs->psw.mask & PSW_MASK_PSTATE)) { 224 address = 0; 225 user_address = 0; 226 goto no_context; 227 } 228 229 /* Low-address protection hit in user mode 'cannot happen'. */ 230 die ("Low-address protection", regs, error_code); 231 do_exit(SIGKILL); 232 } 233 234 /* 235 * get the failing address 236 * more specific the segment and page table portion of 237 * the address 238 */ 239 address = S390_lowcore.trans_exc_code & __FAIL_ADDR_MASK; 240 user_address = check_user_space(regs, error_code); 241 242 /* 243 * Verify that the fault happened in user space, that 244 * we are not in an interrupt and that there is a 245 * user context. 246 */ 247 if (user_address == 0 || in_atomic() || !mm) 248 goto no_context; 249 250 /* 251 * When we get here, the fault happened in the current 252 * task's user address space, so we can switch on the 253 * interrupts again and then search the VMAs 254 */ 255 local_irq_enable(); 256 257 down_read(&mm->mmap_sem); 258 259 vma = find_vma(mm, address); 260 if (!vma) 261 goto bad_area; 262 if (vma->vm_start <= address) 263 goto good_area; 264 if (!(vma->vm_flags & VM_GROWSDOWN)) 265 goto bad_area; 266 if (expand_stack(vma, address)) 267 goto bad_area; 268 /* 269 * Ok, we have a good vm_area for this memory access, so 270 * we can handle it.. 271 */ 272 good_area: 273 si_code = SEGV_ACCERR; 274 if (!is_protection) { 275 /* page not present, check vm flags */ 276 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))) 277 goto bad_area; 278 } else { 279 if (!(vma->vm_flags & VM_WRITE)) 280 goto bad_area; 281 } 282 283 survive: 284 /* 285 * If for any reason at all we couldn't handle the fault, 286 * make sure we exit gracefully rather than endlessly redo 287 * the fault. 288 */ 289 switch (handle_mm_fault(mm, vma, address, is_protection)) { 290 case VM_FAULT_MINOR: 291 tsk->min_flt++; 292 break; 293 case VM_FAULT_MAJOR: 294 tsk->maj_flt++; 295 break; 296 case VM_FAULT_SIGBUS: 297 goto do_sigbus; 298 case VM_FAULT_OOM: 299 goto out_of_memory; 300 default: 301 BUG(); 302 } 303 304 up_read(&mm->mmap_sem); 305 /* 306 * The instruction that caused the program check will 307 * be repeated. Don't signal single step via SIGTRAP. 308 */ 309 clear_tsk_thread_flag(current, TIF_SINGLE_STEP); 310 return; 311 312 /* 313 * Something tried to access memory that isn't in our memory map.. 314 * Fix it, but check if it's kernel or user first.. 315 */ 316 bad_area: 317 up_read(&mm->mmap_sem); 318 319 /* User mode accesses just cause a SIGSEGV */ 320 if (regs->psw.mask & PSW_MASK_PSTATE) { 321 tsk->thread.prot_addr = address; 322 tsk->thread.trap_no = error_code; 323 do_sigsegv(regs, error_code, si_code, address); 324 return; 325 } 326 327 no_context: 328 /* Are we prepared to handle this kernel fault? */ 329 fixup = search_exception_tables(regs->psw.addr & __FIXUP_MASK); 330 if (fixup) { 331 regs->psw.addr = fixup->fixup | PSW_ADDR_AMODE; 332 return; 333 } 334 335 /* 336 * Oops. The kernel tried to access some bad page. We'll have to 337 * terminate things with extreme prejudice. 338 */ 339 if (user_address == 0) 340 printk(KERN_ALERT "Unable to handle kernel pointer dereference" 341 " at virtual kernel address %p\n", (void *)address); 342 else 343 printk(KERN_ALERT "Unable to handle kernel paging request" 344 " at virtual user address %p\n", (void *)address); 345 346 die("Oops", regs, error_code); 347 do_exit(SIGKILL); 348 349 350 /* 351 * We ran out of memory, or some other thing happened to us that made 352 * us unable to handle the page fault gracefully. 353 */ 354 out_of_memory: 355 up_read(&mm->mmap_sem); 356 if (tsk->pid == 1) { 357 yield(); 358 goto survive; 359 } 360 printk("VM: killing process %s\n", tsk->comm); 361 if (regs->psw.mask & PSW_MASK_PSTATE) 362 do_exit(SIGKILL); 363 goto no_context; 364 365 do_sigbus: 366 up_read(&mm->mmap_sem); 367 368 /* 369 * Send a sigbus, regardless of whether we were in kernel 370 * or user mode. 371 */ 372 tsk->thread.prot_addr = address; 373 tsk->thread.trap_no = error_code; 374 force_sig(SIGBUS, tsk); 375 376 /* Kernel mode? Handle exceptions or die */ 377 if (!(regs->psw.mask & PSW_MASK_PSTATE)) 378 goto no_context; 379 } 380 381 void do_protection_exception(struct pt_regs *regs, unsigned long error_code) 382 { 383 regs->psw.addr -= (error_code >> 16); 384 do_exception(regs, 4, 1); 385 } 386 387 void do_dat_exception(struct pt_regs *regs, unsigned long error_code) 388 { 389 do_exception(regs, error_code & 0xff, 0); 390 } 391 392 #ifdef CONFIG_PFAULT 393 /* 394 * 'pfault' pseudo page faults routines. 395 */ 396 static int pfault_disable = 0; 397 398 static int __init nopfault(char *str) 399 { 400 pfault_disable = 1; 401 return 1; 402 } 403 404 __setup("nopfault", nopfault); 405 406 typedef struct { 407 __u16 refdiagc; 408 __u16 reffcode; 409 __u16 refdwlen; 410 __u16 refversn; 411 __u64 refgaddr; 412 __u64 refselmk; 413 __u64 refcmpmk; 414 __u64 reserved; 415 } __attribute__ ((packed)) pfault_refbk_t; 416 417 int pfault_init(void) 418 { 419 pfault_refbk_t refbk = 420 { 0x258, 0, 5, 2, __LC_CURRENT, 1ULL << 48, 1ULL << 48, 421 __PF_RES_FIELD }; 422 int rc; 423 424 if (pfault_disable) 425 return -1; 426 __asm__ __volatile__( 427 " diag %1,%0,0x258\n" 428 "0: j 2f\n" 429 "1: la %0,8\n" 430 "2:\n" 431 ".section __ex_table,\"a\"\n" 432 " .align 4\n" 433 #ifndef CONFIG_64BIT 434 " .long 0b,1b\n" 435 #else /* CONFIG_64BIT */ 436 " .quad 0b,1b\n" 437 #endif /* CONFIG_64BIT */ 438 ".previous" 439 : "=d" (rc) : "a" (&refbk), "m" (refbk) : "cc" ); 440 __ctl_set_bit(0, 9); 441 return rc; 442 } 443 444 void pfault_fini(void) 445 { 446 pfault_refbk_t refbk = 447 { 0x258, 1, 5, 2, 0ULL, 0ULL, 0ULL, 0ULL }; 448 449 if (pfault_disable) 450 return; 451 __ctl_clear_bit(0,9); 452 __asm__ __volatile__( 453 " diag %0,0,0x258\n" 454 "0:\n" 455 ".section __ex_table,\"a\"\n" 456 " .align 4\n" 457 #ifndef CONFIG_64BIT 458 " .long 0b,0b\n" 459 #else /* CONFIG_64BIT */ 460 " .quad 0b,0b\n" 461 #endif /* CONFIG_64BIT */ 462 ".previous" 463 : : "a" (&refbk), "m" (refbk) : "cc" ); 464 } 465 466 asmlinkage void 467 pfault_interrupt(struct pt_regs *regs, __u16 error_code) 468 { 469 struct task_struct *tsk; 470 __u16 subcode; 471 472 /* 473 * Get the external interruption subcode & pfault 474 * initial/completion signal bit. VM stores this 475 * in the 'cpu address' field associated with the 476 * external interrupt. 477 */ 478 subcode = S390_lowcore.cpu_addr; 479 if ((subcode & 0xff00) != __SUBCODE_MASK) 480 return; 481 482 /* 483 * Get the token (= address of the task structure of the affected task). 484 */ 485 tsk = *(struct task_struct **) __LC_PFAULT_INTPARM; 486 487 if (subcode & 0x0080) { 488 /* signal bit is set -> a page has been swapped in by VM */ 489 if (xchg(&tsk->thread.pfault_wait, -1) != 0) { 490 /* Initial interrupt was faster than the completion 491 * interrupt. pfault_wait is valid. Set pfault_wait 492 * back to zero and wake up the process. This can 493 * safely be done because the task is still sleeping 494 * and can't produce new pfaults. */ 495 tsk->thread.pfault_wait = 0; 496 wake_up_process(tsk); 497 put_task_struct(tsk); 498 } 499 } else { 500 /* signal bit not set -> a real page is missing. */ 501 get_task_struct(tsk); 502 set_task_state(tsk, TASK_UNINTERRUPTIBLE); 503 if (xchg(&tsk->thread.pfault_wait, 1) != 0) { 504 /* Completion interrupt was faster than the initial 505 * interrupt (swapped in a -1 for pfault_wait). Set 506 * pfault_wait back to zero and exit. This can be 507 * done safely because tsk is running in kernel 508 * mode and can't produce new pfaults. */ 509 tsk->thread.pfault_wait = 0; 510 set_task_state(tsk, TASK_RUNNING); 511 put_task_struct(tsk); 512 } else 513 set_tsk_need_resched(tsk); 514 } 515 } 516 #endif 517 518