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/config.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/smp.h> 24#include <linux/smp_lock.h> 25#include <linux/compatmac.h> 26#include <linux/init.h> 27#include <linux/console.h> 28 29#include <asm/system.h> 30#include <asm/uaccess.h> 31#include <asm/pgtable.h> 32#include <asm/hardirq.h> 33 34#ifdef CONFIG_SYSCTL 35extern int sysctl_userprocess_debug; 36#endif 37 38extern void die(const char *,struct pt_regs *,long); 39 40extern spinlock_t timerlist_lock; 41 42/* 43 * Unlock any spinlocks which will prevent us from getting the 44 * message out (timerlist_lock is acquired through the 45 * console unblank code) 46 */ 47void bust_spinlocks(int yes) 48{ 49 spin_lock_init(&timerlist_lock); 50 if (yes) { 51 oops_in_progress = 1; 52 } else { 53 int loglevel_save = console_loglevel; 54 oops_in_progress = 0; 55 console_unblank(); 56 /* 57 * OK, the message is on the console. Now we call printk() 58 * without oops_in_progress set so that printk will give klogd 59 * a poke. Hold onto your hats... 60 */ 61 console_loglevel = 15; 62 printk(" "); 63 console_loglevel = loglevel_save; 64 } 65} 66 67/* 68 * Check which address space is addressed by the access 69 * register in S390_lowcore.exc_access_id. 70 * Returns 1 for user space and 0 for kernel space. 71 */ 72static int __check_access_register(struct pt_regs *regs, int error_code) 73{ 74 int areg = S390_lowcore.exc_access_id; 75 76 if (areg == 0) 77 /* Access via access register 0 -> kernel address */ 78 return 0; 79 if (regs && areg < NUM_ACRS && regs->acrs[areg] <= 1) 80 /* 81 * access register contains 0 -> kernel address, 82 * access register contains 1 -> user space address 83 */ 84 return regs->acrs[areg]; 85 86 /* Something unhealthy was done with the access registers... */ 87 die("page fault via unknown access register", regs, error_code); 88 do_exit(SIGKILL); 89 return 0; 90} 91 92/* 93 * Check which address space the address belongs to. 94 * Returns 1 for user space and 0 for kernel space. 95 */ 96static inline int check_user_space(struct pt_regs *regs, int error_code) 97{ 98 /* 99 * The lowest two bits of S390_lowcore.trans_exc_code indicate 100 * which paging table was used: 101 * 0: Primary Segment Table Descriptor 102 * 1: STD determined via access register 103 * 2: Secondary Segment Table Descriptor 104 * 3: Home Segment Table Descriptor 105 */ 106 int descriptor = S390_lowcore.trans_exc_code & 3; 107 if (descriptor == 1) 108 return __check_access_register(regs, error_code); 109 return descriptor >> 1; 110} 111 112/* 113 * Send SIGSEGV to task. This is an external routine 114 * to keep the stack usage of do_page_fault small. 115 */ 116static void force_sigsegv(struct pt_regs *regs, unsigned long error_code, 117 int si_code, unsigned long address) 118{ 119 struct siginfo si; 120 121#if defined(CONFIG_SYSCTL) || defined(CONFIG_PROCESS_DEBUG) 122#if defined(CONFIG_SYSCTL) 123 if (sysctl_userprocess_debug) 124#endif 125 { 126 printk("User process fault: interruption code 0x%lX\n", 127 error_code); 128 printk("failing address: %lX\n", address); 129 show_regs(regs); 130 } 131#endif 132 si.si_signo = SIGSEGV; 133 si.si_code = si_code; 134 si.si_addr = (void *) address; 135 force_sig_info(SIGSEGV, &si, current); 136} 137 138/* 139 * This routine handles page faults. It determines the address, 140 * and the problem, and then passes it off to one of the appropriate 141 * routines. 142 * 143 * error_code: 144 * 04 Protection -> Write-Protection (suprression) 145 * 10 Segment translation -> Not present (nullification) 146 * 11 Page translation -> Not present (nullification) 147 */ 148extern inline void do_exception(struct pt_regs *regs, unsigned long error_code) 149{ 150 struct task_struct *tsk; 151 struct mm_struct *mm; 152 struct vm_area_struct * vma; 153 unsigned long address; 154 int user_address; 155 unsigned long fixup; 156 int si_code = SEGV_MAPERR; 157 158 tsk = current; 159 mm = tsk->mm; 160 161 /* 162 * Check for low-address protection. This needs to be treated 163 * as a special case because the translation exception code 164 * field is not guaranteed to contain valid data in this case. 165 */ 166 if (error_code == 4 && !(S390_lowcore.trans_exc_code & 4)) { 167 168 /* Low-address protection hit in kernel mode means 169 NULL pointer write access in kernel mode. */ 170 if (!(regs->psw.mask & PSW_PROBLEM_STATE)) { 171 address = 0; 172 user_address = 0; 173 goto no_context; 174 } 175 176 /* Low-address protection hit in user mode 'cannot happen'. */ 177 die ("Low-address protection", regs, error_code); 178 do_exit(SIGKILL); 179 } 180 181 /* 182 * get the failing address 183 * more specific the segment and page table portion of 184 * the address 185 */ 186 address = S390_lowcore.trans_exc_code&0x7ffff000; 187 user_address = check_user_space(regs, error_code); 188 189 /* 190 * Verify that the fault happened in user space, that 191 * we are not in an interrupt and that there is a 192 * user context. 193 */ 194 if (user_address == 0 || in_interrupt() || !mm) 195 goto no_context; 196 197 /* 198 * When we get here, the fault happened in the current 199 * task's user address space, so we can switch on the 200 * interrupts again and then search the VMAs 201 */ 202 __sti(); 203 204 down_read(&mm->mmap_sem); 205 206 vma = find_vma(mm, address); 207 if (!vma) 208 goto bad_area; 209 if (vma->vm_start <= address) 210 goto good_area; 211 if (!(vma->vm_flags & VM_GROWSDOWN)) 212 goto bad_area; 213 if (expand_stack(vma, address)) 214 goto bad_area; 215/* 216 * Ok, we have a good vm_area for this memory access, so 217 * we can handle it.. 218 */ 219good_area: 220 si_code = SEGV_ACCERR; 221 if (error_code != 4) { 222 /* page not present, check vm flags */ 223 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))) 224 goto bad_area; 225 } else { 226 if (!(vma->vm_flags & VM_WRITE)) 227 goto bad_area; 228 } 229 230survive: 231 /* 232 * If for any reason at all we couldn't handle the fault, 233 * make sure we exit gracefully rather than endlessly redo 234 * the fault. 235 */ 236 switch (handle_mm_fault(mm, vma, address, error_code == 4)) { 237 case 1: 238 tsk->min_flt++; 239 break; 240 case 2: 241 tsk->maj_flt++; 242 break; 243 case 0: 244 goto do_sigbus; 245 default: 246 goto out_of_memory; 247 } 248 249 up_read(&mm->mmap_sem); 250 return; 251 252/* 253 * Something tried to access memory that isn't in our memory map.. 254 * Fix it, but check if it's kernel or user first.. 255 */ 256bad_area: 257 up_read(&mm->mmap_sem); 258 259 /* User mode accesses just cause a SIGSEGV */ 260 if (regs->psw.mask & PSW_PROBLEM_STATE) { 261 tsk->thread.prot_addr = address; 262 tsk->thread.trap_no = error_code; 263 force_sigsegv(regs, error_code, si_code, address); 264 return; 265 } 266 267no_context: 268 /* Are we prepared to handle this kernel fault? */ 269 if ((fixup = search_exception_table(regs->psw.addr)) != 0) { 270 regs->psw.addr = fixup; 271 return; 272 } 273 274/* 275 * Oops. The kernel tried to access some bad page. We'll have to 276 * terminate things with extreme prejudice. 277 */ 278 if (user_address == 0) 279 printk(KERN_ALERT "Unable to handle kernel pointer dereference" 280 " at virtual kernel address %08lx\n", address); 281 else 282 printk(KERN_ALERT "Unable to handle kernel paging request" 283 " at virtual user address %08lx\n", address); 284 285 die("Oops", regs, error_code); 286 do_exit(SIGKILL); 287 288 289/* 290 * We ran out of memory, or some other thing happened to us that made 291 * us unable to handle the page fault gracefully. 292*/ 293out_of_memory: 294 if (tsk->pid == 1) { 295 yield(); 296 goto survive; 297 } 298 up_read(&mm->mmap_sem); 299 printk("VM: killing process %s\n", tsk->comm); 300 if (regs->psw.mask & PSW_PROBLEM_STATE) 301 do_exit(SIGKILL); 302 goto no_context; 303 304do_sigbus: 305 up_read(&mm->mmap_sem); 306 307 /* 308 * Send a sigbus, regardless of whether we were in kernel 309 * or user mode. 310 */ 311 tsk->thread.prot_addr = address; 312 tsk->thread.trap_no = error_code; 313 force_sig(SIGBUS, tsk); 314 315 /* Kernel mode? Handle exceptions or die */ 316 if (!(regs->psw.mask & PSW_PROBLEM_STATE)) 317 goto no_context; 318} 319 320void do_protection_exception(struct pt_regs *regs, unsigned long error_code) 321{ 322 regs->psw.addr -= (error_code >> 16); 323 do_exception(regs, 4); 324} 325 326void do_segment_exception(struct pt_regs *regs, unsigned long error_code) 327{ 328 do_exception(regs, 0x10); 329} 330 331void do_page_exception(struct pt_regs *regs, unsigned long error_code) 332{ 333 do_exception(regs, 0x11); 334} 335 336typedef struct _pseudo_wait_t { 337 struct _pseudo_wait_t *next; 338 wait_queue_head_t queue; 339 unsigned long address; 340 int resolved; 341} pseudo_wait_t; 342 343static pseudo_wait_t *pseudo_lock_queue = NULL; 344static spinlock_t pseudo_wait_spinlock; /* spinlock to protect lock queue */ 345 346/* 347 * This routine handles 'pagex' pseudo page faults. 348 */ 349asmlinkage void 350do_pseudo_page_fault(struct pt_regs *regs, unsigned long error_code) 351{ 352 pseudo_wait_t wait_struct; 353 pseudo_wait_t *ptr, *last, *next; 354 unsigned long address; 355 356 /* 357 * get the failing address 358 * more specific the segment and page table portion of 359 * the address 360 */ 361 address = S390_lowcore.trans_exc_code & 0xfffff000; 362 363 if (address & 0x80000000) { 364 /* high bit set -> a page has been swapped in by VM */ 365 address &= 0x7fffffff; 366 spin_lock(&pseudo_wait_spinlock); 367 last = NULL; 368 ptr = pseudo_lock_queue; 369 while (ptr != NULL) { 370 next = ptr->next; 371 if (address == ptr->address) { 372 /* 373 * This is one of the processes waiting 374 * for the page. Unchain from the queue. 375 * There can be more than one process 376 * waiting for the same page. VM presents 377 * an initial and a completion interrupt for 378 * every process that tries to access a 379 * page swapped out by VM. 380 */ 381 if (last == NULL) 382 pseudo_lock_queue = next; 383 else 384 last->next = next; 385 /* now wake up the process */ 386 ptr->resolved = 1; 387 wake_up(&ptr->queue); 388 } else 389 last = ptr; 390 ptr = next; 391 } 392 spin_unlock(&pseudo_wait_spinlock); 393 } else { 394 /* Pseudo page faults in kernel mode is a bad idea */ 395 if (!(regs->psw.mask & PSW_PROBLEM_STATE)) { 396 /* 397 * VM presents pseudo page faults if the interrupted 398 * state was not disabled for interrupts. So we can 399 * get pseudo page fault interrupts while running 400 * in kernel mode. We simply access the page here 401 * while we are running disabled. VM will then swap 402 * in the page synchronously. 403 */ 404 if (check_user_space(regs, error_code) == 0) 405 /* dereference a virtual kernel address */ 406 __asm__ __volatile__ ( 407 " ic 0,0(%0)" 408 : : "a" (address) : "0"); 409 else 410 /* dereference a virtual user address */ 411 __asm__ __volatile__ ( 412 " la 2,0(%0)\n" 413 " sacf 512\n" 414 " ic 2,0(2)\n" 415 "0:sacf 0\n" 416 ".section __ex_table,\"a\"\n" 417 " .align 4\n" 418 " .long 0b,0b\n" 419 ".previous" 420 : : "a" (address) : "2" ); 421 422 return; 423 } 424 /* initialize and add element to pseudo_lock_queue */ 425 init_waitqueue_head (&wait_struct.queue); 426 wait_struct.address = address; 427 wait_struct.resolved = 0; 428 spin_lock(&pseudo_wait_spinlock); 429 wait_struct.next = pseudo_lock_queue; 430 pseudo_lock_queue = &wait_struct; 431 spin_unlock(&pseudo_wait_spinlock); 432 /* go to sleep */ 433 wait_event(wait_struct.queue, wait_struct.resolved); 434 } 435} 436 437#ifdef CONFIG_PFAULT 438/* 439 * 'pfault' pseudo page faults routines. 440 */ 441static int pfault_disable = 0; 442 443static int __init nopfault(char *str) 444{ 445 pfault_disable = 1; 446 return 1; 447} 448 449__setup("nopfault", nopfault); 450 451typedef struct { 452 __u16 refdiagc; 453 __u16 reffcode; 454 __u16 refdwlen; 455 __u16 refversn; 456 __u64 refgaddr; 457 __u64 refselmk; 458 __u64 refcmpmk; 459 __u64 reserved; 460} __attribute__ ((packed)) pfault_refbk_t; 461 462int pfault_init(void) 463{ 464 pfault_refbk_t refbk = 465 { 0x258, 0, 5, 2, __LC_KERNEL_STACK, 1ULL << 48, 1ULL << 48, 0ULL }; 466 int rc; 467 468 if (pfault_disable) 469 return -1; 470 __asm__ __volatile__( 471 " diag %1,%0,0x258\n" 472 "0: j 2f\n" 473 "1: la %0,8\n" 474 "2:\n" 475 ".section __ex_table,\"a\"\n" 476 " .align 4\n" 477 " .long 0b,1b\n" 478 ".previous" 479 : "=d" (rc) : "a" (&refbk) : "cc" ); 480 __ctl_set_bit(0, 9); 481 return rc; 482} 483 484void pfault_fini(void) 485{ 486 pfault_refbk_t refbk = 487 { 0x258, 1, 5, 2, 0ULL, 0ULL, 0ULL, 0ULL }; 488 489 if (pfault_disable) 490 return; 491 __ctl_clear_bit(0,9); 492 __asm__ __volatile__( 493 " diag %0,0,0x258\n" 494 "0:\n" 495 ".section __ex_table,\"a\"\n" 496 " .align 4\n" 497 " .long 0b,0b\n" 498 ".previous" 499 : : "a" (&refbk) : "cc" ); 500} 501 502asmlinkage void 503pfault_interrupt(struct pt_regs *regs, __u16 error_code) 504{ 505 struct task_struct *tsk; 506 wait_queue_head_t queue; 507 wait_queue_head_t *qp; 508 __u16 subcode; 509 510 /* 511 * Get the external interruption subcode & pfault 512 * initial/completion signal bit. VM stores this 513 * in the 'cpu address' field associated with the 514 * external interrupt. 515 */ 516 subcode = S390_lowcore.cpu_addr; 517 if ((subcode & 0xff00) != 0x0200) 518 return; 519 520 /* 521 * Get the token (= address of kernel stack of affected task). 522 */ 523 tsk = (struct task_struct *) 524 (*((unsigned long *) __LC_PFAULT_INTPARM) - THREAD_SIZE); 525 526 /* 527 * We got all needed information from the lowcore and can 528 * now safely switch on interrupts. 529 */ 530 if (regs->psw.mask & PSW_PROBLEM_STATE) 531 __sti(); 532 533 if (subcode & 0x0080) { 534 /* signal bit is set -> a page has been swapped in by VM */ 535 qp = (wait_queue_head_t *) 536 xchg(&tsk->thread.pfault_wait, -1); 537 if (qp != NULL) { 538 /* Initial interrupt was faster than the completion 539 * interrupt. pfault_wait is valid. Set pfault_wait 540 * back to zero and wake up the process. This can 541 * safely be done because the task is still sleeping 542 * and can't procude new pfaults. */ 543 tsk->thread.pfault_wait = 0ULL; 544 wake_up(qp); 545 } 546 } else { 547 /* signal bit not set -> a real page is missing. */ 548 init_waitqueue_head (&queue); 549 qp = (wait_queue_head_t *) 550 xchg(&tsk->thread.pfault_wait, (addr_t) &queue); 551 if (qp != NULL) { 552 /* Completion interrupt was faster than the initial 553 * interrupt (swapped in a -1 for pfault_wait). Set 554 * pfault_wait back to zero and exit. This can be 555 * done safely because tsk is running in kernel 556 * mode and can't produce new pfaults. */ 557 tsk->thread.pfault_wait = 0ULL; 558 } 559 560 /* go to sleep */ 561 wait_event(queue, tsk->thread.pfault_wait == 0ULL); 562 } 563} 564#endif 565 566