LXR linux/arch/m68k/mm/fault.c

   1/*
   2 *  linux/arch/m68k/mm/fault.c
   3 *
   4 *  Copyright (C) 1995  Hamish Macdonald
   5 */
   6
   7#include <linux/mman.h>
   8#include <linux/mm.h>
   9#include <linux/kernel.h>
  10#include <linux/ptrace.h>
  11#include <linux/interrupt.h>
  12#include <linux/module.h>
  13#include <linux/uaccess.h>
  14
  15#include <asm/setup.h>
  16#include <asm/traps.h>
  17#include <asm/pgalloc.h>
  18
  19extern void die_if_kernel(char *, struct pt_regs *, long);
  20
  21int send_fault_sig(struct pt_regs *regs)
  22{
  23        siginfo_t siginfo = { 0, 0, 0, };
  24
  25        siginfo.si_signo = current->thread.signo;
  26        siginfo.si_code = current->thread.code;
  27        siginfo.si_addr = (void *)current->thread.faddr;
  28        pr_debug("send_fault_sig: %p,%d,%d\n", siginfo.si_addr,
  29                 siginfo.si_signo, siginfo.si_code);
  30
  31        if (user_mode(regs)) {
  32                force_sig_info(siginfo.si_signo,
  33                               &siginfo, current);
  34        } else {
  35                if (handle_kernel_fault(regs))
  36                        return -1;
  37
  38                //if (siginfo.si_signo == SIGBUS)
  39                //      force_sig_info(siginfo.si_signo,
  40                //                     &siginfo, current);
  41
  42                /*
  43                 * Oops. The kernel tried to access some bad page. We'll have to
  44                 * terminate things with extreme prejudice.
  45                 */
  46                if ((unsigned long)siginfo.si_addr < PAGE_SIZE)
  47                        pr_alert("Unable to handle kernel NULL pointer dereference");
  48                else
  49                        pr_alert("Unable to handle kernel access");
  50                pr_cont(" at virtual address %p\n", siginfo.si_addr);
  51                die_if_kernel("Oops", regs, 0 /*error_code*/);
  52                do_exit(SIGKILL);
  53        }
  54
  55        return 1;
  56}
  57
  58/*
  59 * This routine handles page faults.  It determines the problem, and
  60 * then passes it off to one of the appropriate routines.
  61 *
  62 * error_code:
  63 *      bit 0 == 0 means no page found, 1 means protection fault
  64 *      bit 1 == 0 means read, 1 means write
  65 *
  66 * If this routine detects a bad access, it returns 1, otherwise it
  67 * returns 0.
  68 */
  69int do_page_fault(struct pt_regs *regs, unsigned long address,
  70                              unsigned long error_code)
  71{
  72        struct mm_struct *mm = current->mm;
  73        struct vm_area_struct * vma;
  74        int fault;
  75        unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
  76
  77        pr_debug("do page fault:\nregs->sr=%#x, regs->pc=%#lx, address=%#lx, %ld, %p\n",
  78                regs->sr, regs->pc, address, error_code, mm ? mm->pgd : NULL);
  79
  80        /*
  81         * If we're in an interrupt or have no user
  82         * context, we must not take the fault..
  83         */
  84        if (faulthandler_disabled() || !mm)
  85                goto no_context;
  86
  87        if (user_mode(regs))
  88                flags |= FAULT_FLAG_USER;
  89retry:
  90        down_read(&mm->mmap_sem);
  91
  92        vma = find_vma(mm, address);
  93        if (!vma)
  94                goto map_err;
  95        if (vma->vm_flags & VM_IO)
  96                goto acc_err;
  97        if (vma->vm_start <= address)
  98                goto good_area;
  99        if (!(vma->vm_flags & VM_GROWSDOWN))
 100                goto map_err;
 101        if (user_mode(regs)) {
 102                /* Accessing the stack below usp is always a bug.  The
 103                   "+ 256" is there due to some instructions doing
 104                   pre-decrement on the stack and that doesn't show up
 105                   until later.  */
 106                if (address + 256 < rdusp())
 107                        goto map_err;
 108        }
 109        if (expand_stack(vma, address))
 110                goto map_err;
 111
 112/*
 113 * Ok, we have a good vm_area for this memory access, so
 114 * we can handle it..
 115 */
 116good_area:
 117        pr_debug("do_page_fault: good_area\n");
 118        switch (error_code & 3) {
 119                default:        /* 3: write, present */
 120                        /* fall through */
 121                case 2:         /* write, not present */
 122                        if (!(vma->vm_flags & VM_WRITE))
 123                                goto acc_err;
 124                        flags |= FAULT_FLAG_WRITE;
 125                        break;
 126                case 1:         /* read, present */
 127                        goto acc_err;
 128                case 0:         /* read, not present */
 129                        if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
 130                                goto acc_err;
 131        }
 132
 133        /*
 134         * If for any reason at all we couldn't handle the fault,
 135         * make sure we exit gracefully rather than endlessly redo
 136         * the fault.
 137         */
 138
 139        fault = handle_mm_fault(vma, address, flags);
 140        pr_debug("handle_mm_fault returns %d\n", fault);
 141
 142        if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
 143                return 0;
 144
 145        if (unlikely(fault & VM_FAULT_ERROR)) {
 146                if (fault & VM_FAULT_OOM)
 147                        goto out_of_memory;
 148                else if (fault & VM_FAULT_SIGSEGV)
 149                        goto map_err;
 150                else if (fault & VM_FAULT_SIGBUS)
 151                        goto bus_err;
 152                BUG();
 153        }
 154
 155        /*
 156         * Major/minor page fault accounting is only done on the
 157         * initial attempt. If we go through a retry, it is extremely
 158         * likely that the page will be found in page cache at that point.
 159         */
 160        if (flags & FAULT_FLAG_ALLOW_RETRY) {
 161                if (fault & VM_FAULT_MAJOR)
 162                        current->maj_flt++;
 163                else
 164                        current->min_flt++;
 165                if (fault & VM_FAULT_RETRY) {
 166                        /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
 167                         * of starvation. */
 168                        flags &= ~FAULT_FLAG_ALLOW_RETRY;
 169                        flags |= FAULT_FLAG_TRIED;
 170
 171                        /*
 172                         * No need to up_read(&mm->mmap_sem) as we would
 173                         * have already released it in __lock_page_or_retry
 174                         * in mm/filemap.c.
 175                         */
 176
 177                        goto retry;
 178                }
 179        }
 180
 181        up_read(&mm->mmap_sem);
 182        return 0;
 183
 184/*
 185 * We ran out of memory, or some other thing happened to us that made
 186 * us unable to handle the page fault gracefully.
 187 */
 188out_of_memory:
 189        up_read(&mm->mmap_sem);
 190        if (!user_mode(regs))
 191                goto no_context;
 192        pagefault_out_of_memory();
 193        return 0;
 194
 195no_context:
 196        current->thread.signo = SIGBUS;
 197        current->thread.faddr = address;
 198        return send_fault_sig(regs);
 199
 200bus_err:
 201        current->thread.signo = SIGBUS;
 202        current->thread.code = BUS_ADRERR;
 203        current->thread.faddr = address;
 204        goto send_sig;
 205
 206map_err:
 207        current->thread.signo = SIGSEGV;
 208        current->thread.code = SEGV_MAPERR;
 209        current->thread.faddr = address;
 210        goto send_sig;
 211
 212acc_err:
 213        current->thread.signo = SIGSEGV;
 214        current->thread.code = SEGV_ACCERR;
 215        current->thread.faddr = address;
 216
 217send_sig:
 218        up_read(&mm->mmap_sem);
 219        return send_fault_sig(regs);
 220}
 221