arch/s390/mm/fault.c

   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/init.h>
  26 #include <linux/console.h>
  27 #include <linux/module.h>
  28 #include <linux/hardirq.h>
  29
  30 #include <asm/system.h>
  31 #include <asm/uaccess.h>
  32 #include <asm/pgtable.h>
  33
  34 #ifndef CONFIG_ARCH_S390X
  35 #define __FAIL_ADDR_MASK 0x7ffff000
  36 #define __FIXUP_MASK 0x7fffffff
  37 #define __SUBCODE_MASK 0x0200
  38 #define __PF_RES_FIELD 0ULL
  39 #else /* CONFIG_ARCH_S390X */
  40 #define __FAIL_ADDR_MASK -4096L
  41 #define __FIXUP_MASK ~0L
  42 #define __SUBCODE_MASK 0x0600
  43 #define __PF_RES_FIELD 0x8000000000000000ULL
  44 #endif /* CONFIG_ARCH_S390X */
  45
  46 #ifdef CONFIG_SYSCTL
  47 extern int sysctl_userprocess_debug;
  48 #endif
  49
  50 extern void die(const char *,struct pt_regs *,long);
  51
  52 extern spinlock_t timerlist_lock;
  53
  54 /*
  55  * Unlock any spinlocks which will prevent us from getting the
  56  * message out (timerlist_lock is acquired through the
  57  * console unblank code)
  58  */
  59 void bust_spinlocks(int yes)
  60 {
  61         if (yes) {
  62                 oops_in_progress = 1;
  63         } else {
  64                 int loglevel_save = console_loglevel;
  65                 console_unblank();
  66                 oops_in_progress = 0;
  67                 /*
  68                  * OK, the message is on the console.  Now we call printk()
  69                  * without oops_in_progress set so that printk will give klogd
  70                  * a poke.  Hold onto your hats...
  71                  */
  72                 console_loglevel = 15;
  73                 printk(" ");
  74                 console_loglevel = loglevel_save;
  75         }
  76 }
  77
  78 /*
  79  * Check which address space is addressed by the access
  80  * register in S390_lowcore.exc_access_id.
  81  * Returns 1 for user space and 0 for kernel space.
  82  */
  83 static int __check_access_register(struct pt_regs *regs, int error_code)
  84 {
  85         int areg = S390_lowcore.exc_access_id;
  86
  87         if (areg == 0)
  88                 /* Access via access register 0 -> kernel address */
  89                 return 0;
  90         save_access_regs(current->thread.acrs);
  91         if (regs && areg < NUM_ACRS && current->thread.acrs[areg] <= 1)
  92                 /*
  93                  * access register contains 0 -> kernel address,
  94                  * access register contains 1 -> user space address
  95                  */
  96                 return current->thread.acrs[areg];
  97
  98         /* Something unhealthy was done with the access registers... */
  99         die("page fault via unknown access register", regs, error_code);
 100         do_exit(SIGKILL);
 101         return 0;
 102 }
 103
 104 /*
 105  * Check which address space the address belongs to.
 106  * Returns 1 for user space and 0 for kernel space.
 107  */
 108 static inline int check_user_space(struct pt_regs *regs, int error_code)
 109 {
 110         /*
 111          * The lowest two bits of S390_lowcore.trans_exc_code indicate
 112          * which paging table was used:
 113          *   0: Primary Segment Table Descriptor
 114          *   1: STD determined via access register
 115          *   2: Secondary Segment Table Descriptor
 116          *   3: Home Segment Table Descriptor
 117          */
 118         int descriptor = S390_lowcore.trans_exc_code & 3;
 119         if (unlikely(descriptor == 1))
 120                 return __check_access_register(regs, error_code);
 121         if (descriptor == 2)
 122                 return current->thread.mm_segment.ar4;
 123         return descriptor != 0;
 124 }
 125
 126 /*
 127  * Send SIGSEGV to task.  This is an external routine
 128  * to keep the stack usage of do_page_fault small.
 129  */
 130 static void do_sigsegv(struct pt_regs *regs, unsigned long error_code,
 131                        int si_code, unsigned long address)
 132 {
 133         struct siginfo si;
 134
 135 #if defined(CONFIG_SYSCTL) || defined(CONFIG_PROCESS_DEBUG)
 136 #if defined(CONFIG_SYSCTL)
 137         if (sysctl_userprocess_debug)
 138 #endif
 139         {
 140                 printk("User process fault: interruption code 0x%lX\n",
 141                        error_code);
 142                 printk("failing address: %lX\n", address);
 143                 show_regs(regs);
 144         }
 145 #endif
 146         si.si_signo = SIGSEGV;
 147         si.si_code = si_code;
 148         si.si_addr = (void *) address;
 149         force_sig_info(SIGSEGV, &si, current);
 150 }
 151
 152 /*
 153  * This routine handles page faults.  It determines the address,
 154  * and the problem, and then passes it off to one of the appropriate
 155  * routines.
 156  *
 157  * error_code:
 158  *   04       Protection           ->  Write-Protection  (suprression)
 159  *   10       Segment translation  ->  Not present       (nullification)
 160  *   11       Page translation     ->  Not present       (nullification)
 161  *   3b       Region third trans.  ->  Not present       (nullification)
 162  */
 163 extern inline void
 164 do_exception(struct pt_regs *regs, unsigned long error_code, int is_protection)
 165 {
 166         struct task_struct *tsk;
 167         struct mm_struct *mm;
 168         struct vm_area_struct * vma;
 169         unsigned long address;
 170         int user_address;
 171         const struct exception_table_entry *fixup;
 172         int si_code = SEGV_MAPERR;
 173
 174         tsk = current;
 175         mm = tsk->mm;
 176
 177         /*
 178          * Check for low-address protection.  This needs to be treated
 179          * as a special case because the translation exception code
 180          * field is not guaranteed to contain valid data in this case.
 181          */
 182         if (is_protection && !(S390_lowcore.trans_exc_code & 4)) {
 183
 184                 /* Low-address protection hit in kernel mode means
 185                    NULL pointer write access in kernel mode.  */
 186                 if (!(regs->psw.mask & PSW_MASK_PSTATE)) {
 187                         address = 0;
 188                         user_address = 0;
 189                         goto no_context;
 190                 }
 191
 192                 /* Low-address protection hit in user mode 'cannot happen'.  */
 193                 die ("Low-address protection", regs, error_code);
 194                 do_exit(SIGKILL);
 195         }
 196
 197         /*
 198          * get the failing address
 199          * more specific the segment and page table portion of
 200          * the address
 201          */
 202         address = S390_lowcore.trans_exc_code & __FAIL_ADDR_MASK;
 203         user_address = check_user_space(regs, error_code);
 204
 205         /*
 206          * Verify that the fault happened in user space, that
 207          * we are not in an interrupt and that there is a
 208          * user context.
 209          */
 210         if (user_address == 0 || in_interrupt() || !mm)
 211                 goto no_context;
 212
 213         /*
 214          * When we get here, the fault happened in the current
 215          * task's user address space, so we can switch on the
 216          * interrupts again and then search the VMAs
 217          */
 218         local_irq_enable();
 219
 220         down_read(&mm->mmap_sem);
 221
 222         vma = find_vma(mm, address);
 223         if (!vma)
 224                 goto bad_area;
 225         if (vma->vm_start <= address)
 226                 goto good_area;
 227         if (!(vma->vm_flags & VM_GROWSDOWN))
 228                 goto bad_area;
 229         if (expand_stack(vma, address))
 230                 goto bad_area;
 231 /*
 232  * Ok, we have a good vm_area for this memory access, so
 233  * we can handle it..
 234  */
 235 good_area:
 236         si_code = SEGV_ACCERR;
 237         if (!is_protection) {
 238                 /* page not present, check vm flags */
 239                 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
 240                         goto bad_area;
 241         } else {
 242                 if (!(vma->vm_flags & VM_WRITE))
 243                         goto bad_area;
 244         }
 245
 246 survive:
 247         /*
 248          * If for any reason at all we couldn't handle the fault,
 249          * make sure we exit gracefully rather than endlessly redo
 250          * the fault.
 251          */
 252         switch (handle_mm_fault(mm, vma, address, is_protection)) {
 253         case VM_FAULT_MINOR:
 254                 tsk->min_flt++;
 255                 break;
 256         case VM_FAULT_MAJOR:
 257                 tsk->maj_flt++;
 258                 break;
 259         case VM_FAULT_SIGBUS:
 260                 goto do_sigbus;
 261         case VM_FAULT_OOM:
 262                 goto out_of_memory;
 263         default:
 264                 BUG();
 265         }
 266
 267         up_read(&mm->mmap_sem);
 268         /*
 269          * The instruction that caused the program check will
 270          * be repeated. Don't signal single step via SIGTRAP.
 271          */
 272         clear_tsk_thread_flag(current, TIF_SINGLE_STEP);
 273         return;
 274
 275 /*
 276  * Something tried to access memory that isn't in our memory map..
 277  * Fix it, but check if it's kernel or user first..
 278  */
 279 bad_area:
 280         up_read(&mm->mmap_sem);
 281
 282         /* User mode accesses just cause a SIGSEGV */
 283         if (regs->psw.mask & PSW_MASK_PSTATE) {
 284                 tsk->thread.prot_addr = address;
 285                 tsk->thread.trap_no = error_code;
 286                 do_sigsegv(regs, error_code, si_code, address);
 287                 return;
 288         }
 289
 290 no_context:
 291         /* Are we prepared to handle this kernel fault?  */
 292         fixup = search_exception_tables(regs->psw.addr & __FIXUP_MASK);
 293         if (fixup) {
 294                 regs->psw.addr = fixup->fixup | PSW_ADDR_AMODE;
 295                 return;
 296         }
 297
 298 /*
 299  * Oops. The kernel tried to access some bad page. We'll have to
 300  * terminate things with extreme prejudice.
 301  */
 302         if (user_address == 0)
 303                 printk(KERN_ALERT "Unable to handle kernel pointer dereference"
 304                        " at virtual kernel address %p\n", (void *)address);
 305         else
 306                 printk(KERN_ALERT "Unable to handle kernel paging request"
 307                        " at virtual user address %p\n", (void *)address);
 308
 309         die("Oops", regs, error_code);
 310         do_exit(SIGKILL);
 311
 312
 313 /*
 314  * We ran out of memory, or some other thing happened to us that made
 315  * us unable to handle the page fault gracefully.
 316 */
 317 out_of_memory:
 318         up_read(&mm->mmap_sem);
 319         if (tsk->pid == 1) {
 320                 yield();
 321                 goto survive;
 322         }
 323         printk("VM: killing process %s\n", tsk->comm);
 324         if (regs->psw.mask & PSW_MASK_PSTATE)
 325                 do_exit(SIGKILL);
 326         goto no_context;
 327
 328 do_sigbus:
 329         up_read(&mm->mmap_sem);
 330
 331         /*
 332          * Send a sigbus, regardless of whether we were in kernel
 333          * or user mode.
 334          */
 335         tsk->thread.prot_addr = address;
 336         tsk->thread.trap_no = error_code;
 337         force_sig(SIGBUS, tsk);
 338
 339         /* Kernel mode? Handle exceptions or die */
 340         if (!(regs->psw.mask & PSW_MASK_PSTATE))
 341                 goto no_context;
 342 }
 343
 344 void do_protection_exception(struct pt_regs *regs, unsigned long error_code)
 345 {
 346         regs->psw.addr -= (error_code >> 16);
 347         do_exception(regs, 4, 1);
 348 }
 349
 350 void do_dat_exception(struct pt_regs *regs, unsigned long error_code)
 351 {
 352         do_exception(regs, error_code & 0xff, 0);
 353 }
 354
 355 #ifndef CONFIG_ARCH_S390X
 356
 357 typedef struct _pseudo_wait_t {
 358        struct _pseudo_wait_t *next;
 359        wait_queue_head_t queue;
 360        unsigned long address;
 361        int resolved;
 362 } pseudo_wait_t;
 363
 364 static pseudo_wait_t *pseudo_lock_queue = NULL;
 365 static spinlock_t pseudo_wait_spinlock; /* spinlock to protect lock queue */
 366
 367 /*
 368  * This routine handles 'pagex' pseudo page faults.
 369  */
 370 asmlinkage void
 371 do_pseudo_page_fault(struct pt_regs *regs, unsigned long error_code)
 372 {
 373         pseudo_wait_t wait_struct;
 374         pseudo_wait_t *ptr, *last, *next;
 375         unsigned long address;
 376
 377         /*
 378          * get the failing address
 379          * more specific the segment and page table portion of
 380          * the address
 381          */
 382         address = S390_lowcore.trans_exc_code & 0xfffff000;
 383
 384         if (address & 0x80000000) {
 385                 /* high bit set -> a page has been swapped in by VM */
 386                 address &= 0x7fffffff;
 387                 spin_lock(&pseudo_wait_spinlock);
 388                 last = NULL;
 389                 ptr = pseudo_lock_queue;
 390                 while (ptr != NULL) {
 391                         next = ptr->next;
 392                         if (address == ptr->address) {
 393                                  /*
 394                                  * This is one of the processes waiting
 395                                  * for the page. Unchain from the queue.
 396                                  * There can be more than one process
 397                                  * waiting for the same page. VM presents
 398                                  * an initial and a completion interrupt for
 399                                  * every process that tries to access a
 400                                  * page swapped out by VM.
 401                                  */
 402                                 if (last == NULL)
 403                                         pseudo_lock_queue = next;
 404                                 else
 405                                         last->next = next;
 406                                 /* now wake up the process */
 407                                 ptr->resolved = 1;
 408                                 wake_up(&ptr->queue);
 409                         } else
 410                                 last = ptr;
 411                         ptr = next;
 412                 }
 413                 spin_unlock(&pseudo_wait_spinlock);
 414         } else {
 415                 /* Pseudo page faults in kernel mode is a bad idea */
 416                 if (!(regs->psw.mask & PSW_MASK_PSTATE)) {
 417                         /*
 418                          * VM presents pseudo page faults if the interrupted
 419                          * state was not disabled for interrupts. So we can
 420                          * get pseudo page fault interrupts while running
 421                          * in kernel mode. We simply access the page here
 422                          * while we are running disabled. VM will then swap
 423                          * in the page synchronously.
 424                          */
 425                          if (check_user_space(regs, error_code) == 0)
 426                                  /* dereference a virtual kernel address */
 427                                  __asm__ __volatile__ (
 428                                          "  ic 0,0(%0)"
 429                                          : : "a" (address) : "0");
 430                          else
 431                                  /* dereference a virtual user address */
 432                                  __asm__ __volatile__ (
 433                                          "  la   2,0(%0)\n"
 434                                          "  sacf 512\n"
 435                                          "  ic   2,0(2)\n"
 436                                          "0:sacf 0\n"
 437                                          ".section __ex_table,\"a\"\n"
 438                                          "  .align 4\n"
 439                                          "  .long  0b,0b\n"
 440                                          ".previous"
 441                                          : : "a" (address) : "2" );
 442
 443                         return;
 444                 }
 445                 /* initialize and add element to pseudo_lock_queue */
 446                 init_waitqueue_head (&wait_struct.queue);
 447                 wait_struct.address = address;
 448                 wait_struct.resolved = 0;
 449                 spin_lock(&pseudo_wait_spinlock);
 450                 wait_struct.next = pseudo_lock_queue;
 451                 pseudo_lock_queue = &wait_struct;
 452                 spin_unlock(&pseudo_wait_spinlock);
 453                 /*
 454                  * The instruction that caused the program check will
 455                  * be repeated. Don't signal single step via SIGTRAP.
 456                  */
 457                 clear_tsk_thread_flag(current, TIF_SINGLE_STEP);
 458                 /* go to sleep */
 459                 wait_event(wait_struct.queue, wait_struct.resolved);
 460         }
 461 }
 462 #endif /* CONFIG_ARCH_S390X */
 463
 464 #ifdef CONFIG_PFAULT
 465 /*
 466  * 'pfault' pseudo page faults routines.
 467  */
 468 static int pfault_disable = 0;
 469
 470 static int __init nopfault(char *str)
 471 {
 472         pfault_disable = 1;
 473         return 1;
 474 }
 475
 476 __setup("nopfault", nopfault);
 477
 478 typedef struct {
 479         __u16 refdiagc;
 480         __u16 reffcode;
 481         __u16 refdwlen;
 482         __u16 refversn;
 483         __u64 refgaddr;
 484         __u64 refselmk;
 485         __u64 refcmpmk;
 486         __u64 reserved;
 487 } __attribute__ ((packed)) pfault_refbk_t;
 488
 489 int pfault_init(void)
 490 {
 491         pfault_refbk_t refbk =
 492                 { 0x258, 0, 5, 2, __LC_CURRENT, 1ULL << 48, 1ULL << 48,
 493                   __PF_RES_FIELD };
 494         int rc;
 495
 496         if (pfault_disable)
 497                 return -1;
 498         __asm__ __volatile__(
 499                 "    diag  %1,%0,0x258\n"
 500                 "0:  j     2f\n"
 501                 "1:  la    %0,8\n"
 502                 "2:\n"
 503                 ".section __ex_table,\"a\"\n"
 504                 "   .align 4\n"
 505 #ifndef CONFIG_ARCH_S390X
 506                 "   .long  0b,1b\n"
 507 #else /* CONFIG_ARCH_S390X */
 508                 "   .quad  0b,1b\n"
 509 #endif /* CONFIG_ARCH_S390X */
 510                 ".previous"
 511                 : "=d" (rc) : "a" (&refbk) : "cc" );
 512         __ctl_set_bit(0, 9);
 513         return rc;
 514 }
 515
 516 void pfault_fini(void)
 517 {
 518         pfault_refbk_t refbk =
 519         { 0x258, 1, 5, 2, 0ULL, 0ULL, 0ULL, 0ULL };
 520
 521         if (pfault_disable)
 522                 return;
 523         __ctl_clear_bit(0,9);
 524         __asm__ __volatile__(
 525                 "    diag  %0,0,0x258\n"
 526                 "0:\n"
 527                 ".section __ex_table,\"a\"\n"
 528                 "   .align 4\n"
 529 #ifndef CONFIG_ARCH_S390X
 530                 "   .long  0b,0b\n"
 531 #else /* CONFIG_ARCH_S390X */
 532                 "   .quad  0b,0b\n"
 533 #endif /* CONFIG_ARCH_S390X */
 534                 ".previous"
 535                 : : "a" (&refbk) : "cc" );
 536 }
 537
 538 asmlinkage void
 539 pfault_interrupt(struct pt_regs *regs, __u16 error_code)
 540 {
 541         struct task_struct *tsk;
 542         __u16 subcode;
 543
 544         /*
 545          * Get the external interruption subcode & pfault
 546          * initial/completion signal bit. VM stores this
 547          * in the 'cpu address' field associated with the
 548          * external interrupt.
 549          */
 550         subcode = S390_lowcore.cpu_addr;
 551         if ((subcode & 0xff00) != __SUBCODE_MASK)
 552                 return;
 553
 554         /*
 555          * Get the token (= address of the task structure of the affected task).
 556          */
 557         tsk = *(struct task_struct **) __LC_PFAULT_INTPARM;
 558
 559         if (subcode & 0x0080) {
 560                 /* signal bit is set -> a page has been swapped in by VM */
 561                 if (xchg(&tsk->thread.pfault_wait, -1) != 0) {
 562                         /* Initial interrupt was faster than the completion
 563                          * interrupt. pfault_wait is valid. Set pfault_wait
 564                          * back to zero and wake up the process. This can
 565                          * safely be done because the task is still sleeping
 566                          * and can't procude new pfaults. */
 567                         tsk->thread.pfault_wait = 0;
 568                         wake_up_process(tsk);
 569                 }
 570         } else {
 571                 /* signal bit not set -> a real page is missing. */
 572                 set_task_state(tsk, TASK_UNINTERRUPTIBLE);
 573                 if (xchg(&tsk->thread.pfault_wait, 1) != 0) {
 574                         /* Completion interrupt was faster than the initial
 575                          * interrupt (swapped in a -1 for pfault_wait). Set
 576                          * pfault_wait back to zero and exit. This can be
 577                          * done safely because tsk is running in kernel
 578                          * mode and can't produce new pfaults. */
 579                         tsk->thread.pfault_wait = 0;
 580                         set_task_state(tsk, TASK_RUNNING);
 581                 } else
 582                         set_tsk_need_resched(tsk);
 583         }
 584 }
 585 #endif
 586