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 static 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_atomic() || !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 #ifdef CONFIG_PFAULT
 356 /*
 357  * 'pfault' pseudo page faults routines.
 358  */
 359 static int pfault_disable = 0;
 360
 361 static int __init nopfault(char *str)
 362 {
 363         pfault_disable = 1;
 364         return 1;
 365 }
 366
 367 __setup("nopfault", nopfault);
 368
 369 typedef struct {
 370         __u16 refdiagc;
 371         __u16 reffcode;
 372         __u16 refdwlen;
 373         __u16 refversn;
 374         __u64 refgaddr;
 375         __u64 refselmk;
 376         __u64 refcmpmk;
 377         __u64 reserved;
 378 } __attribute__ ((packed)) pfault_refbk_t;
 379
 380 int pfault_init(void)
 381 {
 382         pfault_refbk_t refbk =
 383                 { 0x258, 0, 5, 2, __LC_CURRENT, 1ULL << 48, 1ULL << 48,
 384                   __PF_RES_FIELD };
 385         int rc;
 386
 387         if (pfault_disable)
 388                 return -1;
 389         __asm__ __volatile__(
 390                 "    diag  %1,%0,0x258\n"
 391                 "0:  j     2f\n"
 392                 "1:  la    %0,8\n"
 393                 "2:\n"
 394                 ".section __ex_table,\"a\"\n"
 395                 "   .align 4\n"
 396 #ifndef CONFIG_ARCH_S390X
 397                 "   .long  0b,1b\n"
 398 #else /* CONFIG_ARCH_S390X */
 399                 "   .quad  0b,1b\n"
 400 #endif /* CONFIG_ARCH_S390X */
 401                 ".previous"
 402                 : "=d" (rc) : "a" (&refbk), "m" (refbk) : "cc" );
 403         __ctl_set_bit(0, 9);
 404         return rc;
 405 }
 406
 407 void pfault_fini(void)
 408 {
 409         pfault_refbk_t refbk =
 410         { 0x258, 1, 5, 2, 0ULL, 0ULL, 0ULL, 0ULL };
 411
 412         if (pfault_disable)
 413                 return;
 414         __ctl_clear_bit(0,9);
 415         __asm__ __volatile__(
 416                 "    diag  %0,0,0x258\n"
 417                 "0:\n"
 418                 ".section __ex_table,\"a\"\n"
 419                 "   .align 4\n"
 420 #ifndef CONFIG_ARCH_S390X
 421                 "   .long  0b,0b\n"
 422 #else /* CONFIG_ARCH_S390X */
 423                 "   .quad  0b,0b\n"
 424 #endif /* CONFIG_ARCH_S390X */
 425                 ".previous"
 426                 : : "a" (&refbk), "m" (refbk) : "cc" );
 427 }
 428
 429 asmlinkage void
 430 pfault_interrupt(struct pt_regs *regs, __u16 error_code)
 431 {
 432         struct task_struct *tsk;
 433         __u16 subcode;
 434
 435         /*
 436          * Get the external interruption subcode & pfault
 437          * initial/completion signal bit. VM stores this
 438          * in the 'cpu address' field associated with the
 439          * external interrupt.
 440          */
 441         subcode = S390_lowcore.cpu_addr;
 442         if ((subcode & 0xff00) != __SUBCODE_MASK)
 443                 return;
 444
 445         /*
 446          * Get the token (= address of the task structure of the affected task).
 447          */
 448         tsk = *(struct task_struct **) __LC_PFAULT_INTPARM;
 449
 450         if (subcode & 0x0080) {
 451                 /* signal bit is set -> a page has been swapped in by VM */
 452                 if (xchg(&tsk->thread.pfault_wait, -1) != 0) {
 453                         /* Initial interrupt was faster than the completion
 454                          * interrupt. pfault_wait is valid. Set pfault_wait
 455                          * back to zero and wake up the process. This can
 456                          * safely be done because the task is still sleeping
 457                          * and can't produce new pfaults. */
 458                         tsk->thread.pfault_wait = 0;
 459                         wake_up_process(tsk);
 460                         put_task_struct(tsk);
 461                 }
 462         } else {
 463                 /* signal bit not set -> a real page is missing. */
 464                 get_task_struct(tsk);
 465                 set_task_state(tsk, TASK_UNINTERRUPTIBLE);
 466                 if (xchg(&tsk->thread.pfault_wait, 1) != 0) {
 467                         /* Completion interrupt was faster than the initial
 468                          * interrupt (swapped in a -1 for pfault_wait). Set
 469                          * pfault_wait back to zero and exit. This can be
 470                          * done safely because tsk is running in kernel
 471                          * mode and can't produce new pfaults. */
 472                         tsk->thread.pfault_wait = 0;
 473                         set_task_state(tsk, TASK_RUNNING);
 474                         put_task_struct(tsk);
 475                 } else
 476                         set_tsk_need_resched(tsk);
 477         }
 478 }
 479 #endif
 480