linux/arch/s390/mm/fault.c
<<
>>
Prefs
   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/kernel_stat.h>
  14#include <linux/perf_event.h>
  15#include <linux/signal.h>
  16#include <linux/sched.h>
  17#include <linux/kernel.h>
  18#include <linux/errno.h>
  19#include <linux/string.h>
  20#include <linux/types.h>
  21#include <linux/ptrace.h>
  22#include <linux/mman.h>
  23#include <linux/mm.h>
  24#include <linux/compat.h>
  25#include <linux/smp.h>
  26#include <linux/kdebug.h>
  27#include <linux/init.h>
  28#include <linux/console.h>
  29#include <linux/module.h>
  30#include <linux/hardirq.h>
  31#include <linux/kprobes.h>
  32#include <linux/uaccess.h>
  33#include <linux/hugetlb.h>
  34#include <asm/asm-offsets.h>
  35#include <asm/system.h>
  36#include <asm/pgtable.h>
  37#include <asm/s390_ext.h>
  38#include <asm/mmu_context.h>
  39#include <asm/compat.h>
  40#include "../kernel/entry.h"
  41
  42#ifndef CONFIG_64BIT
  43#define __FAIL_ADDR_MASK 0x7ffff000
  44#define __SUBCODE_MASK 0x0200
  45#define __PF_RES_FIELD 0ULL
  46#else /* CONFIG_64BIT */
  47#define __FAIL_ADDR_MASK -4096L
  48#define __SUBCODE_MASK 0x0600
  49#define __PF_RES_FIELD 0x8000000000000000ULL
  50#endif /* CONFIG_64BIT */
  51
  52#define VM_FAULT_BADCONTEXT     0x010000
  53#define VM_FAULT_BADMAP         0x020000
  54#define VM_FAULT_BADACCESS      0x040000
  55
  56static unsigned long store_indication;
  57
  58void fault_init(void)
  59{
  60        if (test_facility(2) && test_facility(75))
  61                store_indication = 0xc00;
  62}
  63
  64static inline int notify_page_fault(struct pt_regs *regs)
  65{
  66        int ret = 0;
  67
  68        /* kprobe_running() needs smp_processor_id() */
  69        if (kprobes_built_in() && !user_mode(regs)) {
  70                preempt_disable();
  71                if (kprobe_running() && kprobe_fault_handler(regs, 14))
  72                        ret = 1;
  73                preempt_enable();
  74        }
  75        return ret;
  76}
  77
  78
  79/*
  80 * Unlock any spinlocks which will prevent us from getting the
  81 * message out.
  82 */
  83void bust_spinlocks(int yes)
  84{
  85        if (yes) {
  86                oops_in_progress = 1;
  87        } else {
  88                int loglevel_save = console_loglevel;
  89                console_unblank();
  90                oops_in_progress = 0;
  91                /*
  92                 * OK, the message is on the console.  Now we call printk()
  93                 * without oops_in_progress set so that printk will give klogd
  94                 * a poke.  Hold onto your hats...
  95                 */
  96                console_loglevel = 15;
  97                printk(" ");
  98                console_loglevel = loglevel_save;
  99        }
 100}
 101
 102/*
 103 * Returns the address space associated with the fault.
 104 * Returns 0 for kernel space and 1 for user space.
 105 */
 106static inline int user_space_fault(unsigned long trans_exc_code)
 107{
 108        /*
 109         * The lowest two bits of the translation exception
 110         * identification indicate which paging table was used.
 111         */
 112        trans_exc_code &= 3;
 113        if (trans_exc_code == 2)
 114                /* Access via secondary space, set_fs setting decides */
 115                return current->thread.mm_segment.ar4;
 116        if (user_mode == HOME_SPACE_MODE)
 117                /* User space if the access has been done via home space. */
 118                return trans_exc_code == 3;
 119        /*
 120         * If the user space is not the home space the kernel runs in home
 121         * space. Access via secondary space has already been covered,
 122         * access via primary space or access register is from user space
 123         * and access via home space is from the kernel.
 124         */
 125        return trans_exc_code != 3;
 126}
 127
 128static inline void report_user_fault(struct pt_regs *regs, long int_code,
 129                                     int signr, unsigned long address)
 130{
 131        if ((task_pid_nr(current) > 1) && !show_unhandled_signals)
 132                return;
 133        if (!unhandled_signal(current, signr))
 134                return;
 135        if (!printk_ratelimit())
 136                return;
 137        printk("User process fault: interruption code 0x%lX ", int_code);
 138        print_vma_addr(KERN_CONT "in ", regs->psw.addr & PSW_ADDR_INSN);
 139        printk("\n");
 140        printk("failing address: %lX\n", address);
 141        show_regs(regs);
 142}
 143
 144/*
 145 * Send SIGSEGV to task.  This is an external routine
 146 * to keep the stack usage of do_page_fault small.
 147 */
 148static noinline void do_sigsegv(struct pt_regs *regs, long int_code,
 149                                int si_code, unsigned long trans_exc_code)
 150{
 151        struct siginfo si;
 152        unsigned long address;
 153
 154        address = trans_exc_code & __FAIL_ADDR_MASK;
 155        current->thread.prot_addr = address;
 156        current->thread.trap_no = int_code;
 157        report_user_fault(regs, int_code, SIGSEGV, address);
 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
 164static noinline void do_no_context(struct pt_regs *regs, long int_code,
 165                                   unsigned long trans_exc_code)
 166{
 167        const struct exception_table_entry *fixup;
 168        unsigned long address;
 169
 170        /* Are we prepared to handle this kernel fault?  */
 171        fixup = search_exception_tables(regs->psw.addr & PSW_ADDR_INSN);
 172        if (fixup) {
 173                regs->psw.addr = fixup->fixup | PSW_ADDR_AMODE;
 174                return;
 175        }
 176
 177        /*
 178         * Oops. The kernel tried to access some bad page. We'll have to
 179         * terminate things with extreme prejudice.
 180         */
 181        address = trans_exc_code & __FAIL_ADDR_MASK;
 182        if (!user_space_fault(trans_exc_code))
 183                printk(KERN_ALERT "Unable to handle kernel pointer dereference"
 184                       " at virtual kernel address %p\n", (void *)address);
 185        else
 186                printk(KERN_ALERT "Unable to handle kernel paging request"
 187                       " at virtual user address %p\n", (void *)address);
 188
 189        die("Oops", regs, int_code);
 190        do_exit(SIGKILL);
 191}
 192
 193static noinline void do_low_address(struct pt_regs *regs, long int_code,
 194                                    unsigned long trans_exc_code)
 195{
 196        /* Low-address protection hit in kernel mode means
 197           NULL pointer write access in kernel mode.  */
 198        if (regs->psw.mask & PSW_MASK_PSTATE) {
 199                /* Low-address protection hit in user mode 'cannot happen'. */
 200                die ("Low-address protection", regs, int_code);
 201                do_exit(SIGKILL);
 202        }
 203
 204        do_no_context(regs, int_code, trans_exc_code);
 205}
 206
 207static noinline void do_sigbus(struct pt_regs *regs, long int_code,
 208                               unsigned long trans_exc_code)
 209{
 210        struct task_struct *tsk = current;
 211        unsigned long address;
 212        struct siginfo si;
 213
 214        /*
 215         * Send a sigbus, regardless of whether we were in kernel
 216         * or user mode.
 217         */
 218        address = trans_exc_code & __FAIL_ADDR_MASK;
 219        tsk->thread.prot_addr = address;
 220        tsk->thread.trap_no = int_code;
 221        si.si_signo = SIGBUS;
 222        si.si_errno = 0;
 223        si.si_code = BUS_ADRERR;
 224        si.si_addr = (void __user *) address;
 225        force_sig_info(SIGBUS, &si, tsk);
 226}
 227
 228#ifdef CONFIG_S390_EXEC_PROTECT
 229static noinline int signal_return(struct pt_regs *regs, long int_code,
 230                                  unsigned long trans_exc_code)
 231{
 232        u16 instruction;
 233        int rc;
 234
 235        rc = __get_user(instruction, (u16 __user *) regs->psw.addr);
 236
 237        if (!rc && instruction == 0x0a77) {
 238                clear_tsk_thread_flag(current, TIF_PER_TRAP);
 239                if (is_compat_task())
 240                        sys32_sigreturn();
 241                else
 242                        sys_sigreturn();
 243        } else if (!rc && instruction == 0x0aad) {
 244                clear_tsk_thread_flag(current, TIF_PER_TRAP);
 245                if (is_compat_task())
 246                        sys32_rt_sigreturn();
 247                else
 248                        sys_rt_sigreturn();
 249        } else
 250                do_sigsegv(regs, int_code, SEGV_MAPERR, trans_exc_code);
 251        return 0;
 252}
 253#endif /* CONFIG_S390_EXEC_PROTECT */
 254
 255static noinline void do_fault_error(struct pt_regs *regs, long int_code,
 256                                    unsigned long trans_exc_code, int fault)
 257{
 258        int si_code;
 259
 260        switch (fault) {
 261        case VM_FAULT_BADACCESS:
 262#ifdef CONFIG_S390_EXEC_PROTECT
 263                if ((regs->psw.mask & PSW_MASK_ASC) == PSW_ASC_SECONDARY &&
 264                    (trans_exc_code & 3) == 0) {
 265                        signal_return(regs, int_code, trans_exc_code);
 266                        break;
 267                }
 268#endif /* CONFIG_S390_EXEC_PROTECT */
 269        case VM_FAULT_BADMAP:
 270                /* Bad memory access. Check if it is kernel or user space. */
 271                if (regs->psw.mask & PSW_MASK_PSTATE) {
 272                        /* User mode accesses just cause a SIGSEGV */
 273                        si_code = (fault == VM_FAULT_BADMAP) ?
 274                                SEGV_MAPERR : SEGV_ACCERR;
 275                        do_sigsegv(regs, int_code, si_code, trans_exc_code);
 276                        return;
 277                }
 278        case VM_FAULT_BADCONTEXT:
 279                do_no_context(regs, int_code, trans_exc_code);
 280                break;
 281        default: /* fault & VM_FAULT_ERROR */
 282                if (fault & VM_FAULT_OOM)
 283                        pagefault_out_of_memory();
 284                else if (fault & VM_FAULT_SIGBUS) {
 285                        /* Kernel mode? Handle exceptions or die */
 286                        if (!(regs->psw.mask & PSW_MASK_PSTATE))
 287                                do_no_context(regs, int_code, trans_exc_code);
 288                        else
 289                                do_sigbus(regs, int_code, trans_exc_code);
 290                } else
 291                        BUG();
 292                break;
 293        }
 294}
 295
 296/*
 297 * This routine handles page faults.  It determines the address,
 298 * and the problem, and then passes it off to one of the appropriate
 299 * routines.
 300 *
 301 * interruption code (int_code):
 302 *   04       Protection           ->  Write-Protection  (suprression)
 303 *   10       Segment translation  ->  Not present       (nullification)
 304 *   11       Page translation     ->  Not present       (nullification)
 305 *   3b       Region third trans.  ->  Not present       (nullification)
 306 */
 307static inline int do_exception(struct pt_regs *regs, int access,
 308                               unsigned long trans_exc_code)
 309{
 310        struct task_struct *tsk;
 311        struct mm_struct *mm;
 312        struct vm_area_struct *vma;
 313        unsigned long address;
 314        int fault, write;
 315
 316        if (notify_page_fault(regs))
 317                return 0;
 318
 319        tsk = current;
 320        mm = tsk->mm;
 321
 322        /*
 323         * Verify that the fault happened in user space, that
 324         * we are not in an interrupt and that there is a 
 325         * user context.
 326         */
 327        fault = VM_FAULT_BADCONTEXT;
 328        if (unlikely(!user_space_fault(trans_exc_code) || in_atomic() || !mm))
 329                goto out;
 330
 331        address = trans_exc_code & __FAIL_ADDR_MASK;
 332        perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, 0, regs, address);
 333        down_read(&mm->mmap_sem);
 334
 335        fault = VM_FAULT_BADMAP;
 336        vma = find_vma(mm, address);
 337        if (!vma)
 338                goto out_up;
 339
 340        if (unlikely(vma->vm_start > address)) {
 341                if (!(vma->vm_flags & VM_GROWSDOWN))
 342                        goto out_up;
 343                if (expand_stack(vma, address))
 344                        goto out_up;
 345        }
 346
 347        /*
 348         * Ok, we have a good vm_area for this memory access, so
 349         * we can handle it..
 350         */
 351        fault = VM_FAULT_BADACCESS;
 352        if (unlikely(!(vma->vm_flags & access)))
 353                goto out_up;
 354
 355        if (is_vm_hugetlb_page(vma))
 356                address &= HPAGE_MASK;
 357        /*
 358         * If for any reason at all we couldn't handle the fault,
 359         * make sure we exit gracefully rather than endlessly redo
 360         * the fault.
 361         */
 362        write = (access == VM_WRITE ||
 363                 (trans_exc_code & store_indication) == 0x400) ?
 364                FAULT_FLAG_WRITE : 0;
 365        fault = handle_mm_fault(mm, vma, address, write);
 366        if (unlikely(fault & VM_FAULT_ERROR))
 367                goto out_up;
 368
 369        if (fault & VM_FAULT_MAJOR) {
 370                tsk->maj_flt++;
 371                perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, 0,
 372                                     regs, address);
 373        } else {
 374                tsk->min_flt++;
 375                perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, 0,
 376                                     regs, address);
 377        }
 378        /*
 379         * The instruction that caused the program check will
 380         * be repeated. Don't signal single step via SIGTRAP.
 381         */
 382        clear_tsk_thread_flag(tsk, TIF_PER_TRAP);
 383        fault = 0;
 384out_up:
 385        up_read(&mm->mmap_sem);
 386out:
 387        return fault;
 388}
 389
 390void __kprobes do_protection_exception(struct pt_regs *regs, long pgm_int_code,
 391                                       unsigned long trans_exc_code)
 392{
 393        int fault;
 394
 395        /* Protection exception is suppressing, decrement psw address. */
 396        regs->psw.addr -= (pgm_int_code >> 16);
 397        /*
 398         * Check for low-address protection.  This needs to be treated
 399         * as a special case because the translation exception code
 400         * field is not guaranteed to contain valid data in this case.
 401         */
 402        if (unlikely(!(trans_exc_code & 4))) {
 403                do_low_address(regs, pgm_int_code, trans_exc_code);
 404                return;
 405        }
 406        fault = do_exception(regs, VM_WRITE, trans_exc_code);
 407        if (unlikely(fault))
 408                do_fault_error(regs, 4, trans_exc_code, fault);
 409}
 410
 411void __kprobes do_dat_exception(struct pt_regs *regs, long pgm_int_code,
 412                                unsigned long trans_exc_code)
 413{
 414        int access, fault;
 415
 416        access = VM_READ | VM_EXEC | VM_WRITE;
 417#ifdef CONFIG_S390_EXEC_PROTECT
 418        if ((regs->psw.mask & PSW_MASK_ASC) == PSW_ASC_SECONDARY &&
 419            (trans_exc_code & 3) == 0)
 420                access = VM_EXEC;
 421#endif
 422        fault = do_exception(regs, access, trans_exc_code);
 423        if (unlikely(fault))
 424                do_fault_error(regs, pgm_int_code & 255, trans_exc_code, fault);
 425}
 426
 427#ifdef CONFIG_64BIT
 428void __kprobes do_asce_exception(struct pt_regs *regs, long pgm_int_code,
 429                                 unsigned long trans_exc_code)
 430{
 431        struct mm_struct *mm = current->mm;
 432        struct vm_area_struct *vma;
 433
 434        if (unlikely(!user_space_fault(trans_exc_code) || in_atomic() || !mm))
 435                goto no_context;
 436
 437        down_read(&mm->mmap_sem);
 438        vma = find_vma(mm, trans_exc_code & __FAIL_ADDR_MASK);
 439        up_read(&mm->mmap_sem);
 440
 441        if (vma) {
 442                update_mm(mm, current);
 443                return;
 444        }
 445
 446        /* User mode accesses just cause a SIGSEGV */
 447        if (regs->psw.mask & PSW_MASK_PSTATE) {
 448                do_sigsegv(regs, pgm_int_code, SEGV_MAPERR, trans_exc_code);
 449                return;
 450        }
 451
 452no_context:
 453        do_no_context(regs, pgm_int_code, trans_exc_code);
 454}
 455#endif
 456
 457int __handle_fault(unsigned long uaddr, unsigned long pgm_int_code, int write)
 458{
 459        struct pt_regs regs;
 460        int access, fault;
 461
 462        regs.psw.mask = psw_kernel_bits;
 463        if (!irqs_disabled())
 464                regs.psw.mask |= PSW_MASK_IO | PSW_MASK_EXT;
 465        regs.psw.addr = (unsigned long) __builtin_return_address(0);
 466        regs.psw.addr |= PSW_ADDR_AMODE;
 467        uaddr &= PAGE_MASK;
 468        access = write ? VM_WRITE : VM_READ;
 469        fault = do_exception(&regs, access, uaddr | 2);
 470        if (unlikely(fault)) {
 471                if (fault & VM_FAULT_OOM) {
 472                        pagefault_out_of_memory();
 473                        fault = 0;
 474                } else if (fault & VM_FAULT_SIGBUS)
 475                        do_sigbus(&regs, pgm_int_code, uaddr);
 476        }
 477        return fault ? -EFAULT : 0;
 478}
 479
 480#ifdef CONFIG_PFAULT 
 481/*
 482 * 'pfault' pseudo page faults routines.
 483 */
 484static int pfault_disable;
 485
 486static int __init nopfault(char *str)
 487{
 488        pfault_disable = 1;
 489        return 1;
 490}
 491
 492__setup("nopfault", nopfault);
 493
 494typedef struct {
 495        __u16 refdiagc;
 496        __u16 reffcode;
 497        __u16 refdwlen;
 498        __u16 refversn;
 499        __u64 refgaddr;
 500        __u64 refselmk;
 501        __u64 refcmpmk;
 502        __u64 reserved;
 503} __attribute__ ((packed, aligned(8))) pfault_refbk_t;
 504
 505int pfault_init(void)
 506{
 507        pfault_refbk_t refbk =
 508                { 0x258, 0, 5, 2, __LC_CURRENT, 1ULL << 48, 1ULL << 48,
 509                  __PF_RES_FIELD };
 510        int rc;
 511
 512        if (!MACHINE_IS_VM || pfault_disable)
 513                return -1;
 514        asm volatile(
 515                "       diag    %1,%0,0x258\n"
 516                "0:     j       2f\n"
 517                "1:     la      %0,8\n"
 518                "2:\n"
 519                EX_TABLE(0b,1b)
 520                : "=d" (rc) : "a" (&refbk), "m" (refbk) : "cc");
 521        __ctl_set_bit(0, 9);
 522        return rc;
 523}
 524
 525void pfault_fini(void)
 526{
 527        pfault_refbk_t refbk =
 528        { 0x258, 1, 5, 2, 0ULL, 0ULL, 0ULL, 0ULL };
 529
 530        if (!MACHINE_IS_VM || pfault_disable)
 531                return;
 532        __ctl_clear_bit(0,9);
 533        asm volatile(
 534                "       diag    %0,0,0x258\n"
 535                "0:\n"
 536                EX_TABLE(0b,0b)
 537                : : "a" (&refbk), "m" (refbk) : "cc");
 538}
 539
 540static void pfault_interrupt(unsigned int ext_int_code,
 541                             unsigned int param32, unsigned long param64)
 542{
 543        struct task_struct *tsk;
 544        __u16 subcode;
 545
 546        /*
 547         * Get the external interruption subcode & pfault
 548         * initial/completion signal bit. VM stores this 
 549         * in the 'cpu address' field associated with the
 550         * external interrupt. 
 551         */
 552        subcode = ext_int_code >> 16;
 553        if ((subcode & 0xff00) != __SUBCODE_MASK)
 554                return;
 555        kstat_cpu(smp_processor_id()).irqs[EXTINT_PFL]++;
 556
 557        /*
 558         * Get the token (= address of the task structure of the affected task).
 559         */
 560#ifdef CONFIG_64BIT
 561        tsk = (struct task_struct *) param64;
 562#else
 563        tsk = (struct task_struct *) param32;
 564#endif
 565
 566        if (subcode & 0x0080) {
 567                /* signal bit is set -> a page has been swapped in by VM */
 568                if (xchg(&tsk->thread.pfault_wait, -1) != 0) {
 569                        /* Initial interrupt was faster than the completion
 570                         * interrupt. pfault_wait is valid. Set pfault_wait
 571                         * back to zero and wake up the process. This can
 572                         * safely be done because the task is still sleeping
 573                         * and can't produce new pfaults. */
 574                        tsk->thread.pfault_wait = 0;
 575                        wake_up_process(tsk);
 576                        put_task_struct(tsk);
 577                }
 578        } else {
 579                /* signal bit not set -> a real page is missing. */
 580                get_task_struct(tsk);
 581                set_task_state(tsk, TASK_UNINTERRUPTIBLE);
 582                if (xchg(&tsk->thread.pfault_wait, 1) != 0) {
 583                        /* Completion interrupt was faster than the initial
 584                         * interrupt (swapped in a -1 for pfault_wait). Set
 585                         * pfault_wait back to zero and exit. This can be
 586                         * done safely because tsk is running in kernel 
 587                         * mode and can't produce new pfaults. */
 588                        tsk->thread.pfault_wait = 0;
 589                        set_task_state(tsk, TASK_RUNNING);
 590                        put_task_struct(tsk);
 591                } else
 592                        set_tsk_need_resched(tsk);
 593        }
 594}
 595
 596static int __init pfault_irq_init(void)
 597{
 598        int rc;
 599
 600        if (!MACHINE_IS_VM)
 601                return 0;
 602        /*
 603         * Try to get pfault pseudo page faults going.
 604         */
 605        rc = register_external_interrupt(0x2603, pfault_interrupt);
 606        if (rc) {
 607                pfault_disable = 1;
 608                return rc;
 609        }
 610        if (pfault_init() == 0)
 611                return 0;
 612
 613        /* Tough luck, no pfault. */
 614        pfault_disable = 1;
 615        unregister_external_interrupt(0x2603, pfault_interrupt);
 616        return 0;
 617}
 618early_initcall(pfault_irq_init);
 619
 620#endif
 621