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         if (user_mode(regs))
  92                 flags |= FAULT_FLAG_USER;
  93 retry:
  94         down_read(&mm->mmap_sem);
  95
  96         vma = find_vma(mm, address);
  97         if (!vma)
  98                 goto map_err;
  99         if (vma->vm_flags & VM_IO)
 100                 goto acc_err;
 101         if (vma->vm_start <= address)
 102                 goto good_area;
 103         if (!(vma->vm_flags & VM_GROWSDOWN))
 104                 goto map_err;
 105         if (user_mode(regs)) {
 106                 /* Accessing the stack below usp is always a bug.  The
 107                    "+ 256" is there due to some instructions doing
 108                    pre-decrement on the stack and that doesn't show up
 109                    until later.  */
 110                 if (address + 256 < rdusp())
 111                         goto map_err;
 112         }
 113         if (expand_stack(vma, address))
 114                 goto map_err;
 115
 116 /*
 117  * Ok, we have a good vm_area for this memory access, so
 118  * we can handle it..
 119  */
 120 good_area:
 121 #ifdef DEBUG
 122         printk("do_page_fault: good_area\n");
 123 #endif
 124         switch (error_code & 3) {
 125                 default:        /* 3: write, present */
 126                         /* fall through */
 127                 case 2:         /* write, not present */
 128                         if (!(vma->vm_flags & VM_WRITE))
 129                                 goto acc_err;
 130                         flags |= FAULT_FLAG_WRITE;
 131                         break;
 132                 case 1:         /* read, present */
 133                         goto acc_err;
 134                 case 0:         /* read, not present */
 135                         if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
 136                                 goto acc_err;
 137         }
 138
 139         /*
 140          * If for any reason at all we couldn't handle the fault,
 141          * make sure we exit gracefully rather than endlessly redo
 142          * the fault.
 143          */
 144
 145         fault = handle_mm_fault(mm, vma, address, flags);
 146 #ifdef DEBUG
 147         printk("handle_mm_fault returns %d\n",fault);
 148 #endif
 149
 150         if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
 151                 return 0;
 152
 153         if (unlikely(fault & VM_FAULT_ERROR)) {
 154                 if (fault & VM_FAULT_OOM)
 155                         goto out_of_memory;
 156                 else if (fault & VM_FAULT_SIGBUS)
 157                         goto bus_err;
 158                 BUG();
 159         }
 160
 161         /*
 162          * Major/minor page fault accounting is only done on the
 163          * initial attempt. If we go through a retry, it is extremely
 164          * likely that the page will be found in page cache at that point.
 165          */
 166         if (flags & FAULT_FLAG_ALLOW_RETRY) {
 167                 if (fault & VM_FAULT_MAJOR)
 168                         current->maj_flt++;
 169                 else
 170                         current->min_flt++;
 171                 if (fault & VM_FAULT_RETRY) {
 172                         /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
 173                          * of starvation. */
 174                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
 175                         flags |= FAULT_FLAG_TRIED;
 176
 177                         /*
 178                          * No need to up_read(&mm->mmap_sem) as we would
 179                          * have already released it in __lock_page_or_retry
 180                          * in mm/filemap.c.
 181                          */
 182
 183                         goto retry;
 184                 }
 185         }
 186
 187         up_read(&mm->mmap_sem);
 188         return 0;
 189
 190 /*
 191  * We ran out of memory, or some other thing happened to us that made
 192  * us unable to handle the page fault gracefully.
 193  */
 194 out_of_memory:
 195         up_read(&mm->mmap_sem);
 196         if (!user_mode(regs))
 197                 goto no_context;
 198         pagefault_out_of_memory();
 199         return 0;
 200
 201 no_context:
 202         current->thread.signo = SIGBUS;
 203         current->thread.faddr = address;
 204         return send_fault_sig(regs);
 205
 206 bus_err:
 207         current->thread.signo = SIGBUS;
 208         current->thread.code = BUS_ADRERR;
 209         current->thread.faddr = address;
 210         goto send_sig;
 211
 212 map_err:
 213         current->thread.signo = SIGSEGV;
 214         current->thread.code = SEGV_MAPERR;
 215         current->thread.faddr = address;
 216         goto send_sig;
 217
 218 acc_err:
 219         current->thread.signo = SIGSEGV;
 220         current->thread.code = SEGV_ACCERR;
 221         current->thread.faddr = address;
 222
 223 send_sig:
 224         up_read(&mm->mmap_sem);
 225         return send_fault_sig(regs);
 226 }