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
  14 #include <asm/setup.h>
  15 #include <asm/traps.h>
  16 #include <asm/uaccess.h>
  17 #include <asm/pgalloc.h>
  18
  19 extern void die_if_kernel(char *, struct pt_regs *, long);
  20
  21 int 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 #ifdef DEBUG
  29         printk("send_fault_sig: %p,%d,%d\n", siginfo.si_addr, siginfo.si_signo, siginfo.si_code);
  30 #endif
  31
  32         if (user_mode(regs)) {
  33                 force_sig_info(siginfo.si_signo,
  34                                &siginfo, current);
  35         } else {
  36                 if (handle_kernel_fault(regs))
  37                         return -1;
  38
  39                 //if (siginfo.si_signo == SIGBUS)
  40                 //      force_sig_info(siginfo.si_signo,
  41                 //                     &siginfo, current);
  42
  43                 /*
  44                  * Oops. The kernel tried to access some bad page. We'll have to
  45                  * terminate things with extreme prejudice.
  46                  */
  47                 if ((unsigned long)siginfo.si_addr < PAGE_SIZE)
  48                         printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference");
  49                 else
  50                         printk(KERN_ALERT "Unable to handle kernel access");
  51                 printk(" at virtual address %p\n", siginfo.si_addr);
  52                 die_if_kernel("Oops", regs, 0 /*error_code*/);
  53                 do_exit(SIGKILL);
  54         }
  55
  56         return 1;
  57 }
  58
  59 /*
  60  * This routine handles page faults.  It determines the problem, and
  61  * then passes it off to one of the appropriate routines.
  62  *
  63  * error_code:
  64  *      bit 0 == 0 means no page found, 1 means protection fault
  65  *      bit 1 == 0 means read, 1 means write
  66  *
  67  * If this routine detects a bad access, it returns 1, otherwise it
  68  * returns 0.
  69  */
  70 int do_page_fault(struct pt_regs *regs, unsigned long address,
  71                               unsigned long error_code)
  72 {
  73         struct mm_struct *mm = current->mm;
  74         struct vm_area_struct * vma;
  75         int fault;
  76         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
  77
  78 #ifdef DEBUG
  79         printk ("do page fault:\nregs->sr=%#x, regs->pc=%#lx, address=%#lx, %ld, %p\n",
  80                 regs->sr, regs->pc, address, error_code,
  81                 current->mm->pgd);
  82 #endif
  83
  84         /*
  85          * If we're in an interrupt or have no user
  86          * context, we must not take the fault..
  87          */
  88         if (in_atomic() || !mm)
  89                 goto no_context;
  90
  91 retry:
  92         down_read(&mm->mmap_sem);
  93
  94         vma = find_vma(mm, address);
  95         if (!vma)
  96                 goto map_err;
  97         if (vma->vm_flags & VM_IO)
  98                 goto acc_err;
  99         if (vma->vm_start <= address)
 100                 goto good_area;
 101         if (!(vma->vm_flags & VM_GROWSDOWN))
 102                 goto map_err;
 103         if (user_mode(regs)) {
 104                 /* Accessing the stack below usp is always a bug.  The
 105                    "+ 256" is there due to some instructions doing
 106                    pre-decrement on the stack and that doesn't show up
 107                    until later.  */
 108                 if (address + 256 < rdusp())
 109                         goto map_err;
 110         }
 111         if (expand_stack(vma, address))
 112                 goto map_err;
 113
 114 /*
 115  * Ok, we have a good vm_area for this memory access, so
 116  * we can handle it..
 117  */
 118 good_area:
 119 #ifdef DEBUG
 120         printk("do_page_fault: good_area\n");
 121 #endif
 122         switch (error_code & 3) {
 123                 default:        /* 3: write, present */
 124                         /* fall through */
 125                 case 2:         /* write, not present */
 126                         if (!(vma->vm_flags & VM_WRITE))
 127                                 goto acc_err;
 128                         flags |= FAULT_FLAG_WRITE;
 129                         break;
 130                 case 1:         /* read, present */
 131                         goto acc_err;
 132                 case 0:         /* read, not present */
 133                         if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
 134                                 goto acc_err;
 135         }
 136
 137         /*
 138          * If for any reason at all we couldn't handle the fault,
 139          * make sure we exit gracefully rather than endlessly redo
 140          * the fault.
 141          */
 142
 143         fault = handle_mm_fault(mm, vma, address, flags);
 144 #ifdef DEBUG
 145         printk("handle_mm_fault returns %d\n",fault);
 146 #endif
 147
 148         if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
 149                 return 0;
 150
 151         if (unlikely(fault & VM_FAULT_ERROR)) {
 152                 if (fault & VM_FAULT_OOM)
 153                         goto out_of_memory;
 154                 else if (fault & VM_FAULT_SIGBUS)
 155                         goto bus_err;
 156                 BUG();
 157         }
 158
 159         /*
 160          * Major/minor page fault accounting is only done on the
 161          * initial attempt. If we go through a retry, it is extremely
 162          * likely that the page will be found in page cache at that point.
 163          */
 164         if (flags & FAULT_FLAG_ALLOW_RETRY) {
 165                 if (fault & VM_FAULT_MAJOR)
 166                         current->maj_flt++;
 167                 else
 168                         current->min_flt++;
 169                 if (fault & VM_FAULT_RETRY) {
 170                         /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
 171                          * of starvation. */
 172                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
 173                         flags |= FAULT_FLAG_TRIED;
 174
 175                         /*
 176                          * No need to up_read(&mm->mmap_sem) as we would
 177                          * have already released it in __lock_page_or_retry
 178                          * in mm/filemap.c.
 179                          */
 180
 181                         goto retry;
 182                 }
 183         }
 184
 185         up_read(&mm->mmap_sem);
 186         return 0;
 187
 188 /*
 189  * We ran out of memory, or some other thing happened to us that made
 190  * us unable to handle the page fault gracefully.
 191  */
 192 out_of_memory:
 193         up_read(&mm->mmap_sem);
 194         if (!user_mode(regs))
 195                 goto no_context;
 196         pagefault_out_of_memory();
 197         return 0;
 198
 199 no_context:
 200         current->thread.signo = SIGBUS;
 201         current->thread.faddr = address;
 202         return send_fault_sig(regs);
 203
 204 bus_err:
 205         current->thread.signo = SIGBUS;
 206         current->thread.code = BUS_ADRERR;
 207         current->thread.faddr = address;
 208         goto send_sig;
 209
 210 map_err:
 211         current->thread.signo = SIGSEGV;
 212         current->thread.code = SEGV_MAPERR;
 213         current->thread.faddr = address;
 214         goto send_sig;
 215
 216 acc_err:
 217         current->thread.signo = SIGSEGV;
 218         current->thread.code = SEGV_ACCERR;
 219         current->thread.faddr = address;
 220
 221 send_sig:
 222         up_read(&mm->mmap_sem);
 223         return send_fault_sig(regs);
 224 }