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
  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         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  */
  69 int 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;
  89 retry:
  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  */
 116 good_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  */
 188 out_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
 195 no_context:
 196         current->thread.signo = SIGBUS;
 197         current->thread.faddr = address;
 198         return send_fault_sig(regs);
 199
 200 bus_err:
 201         current->thread.signo = SIGBUS;
 202         current->thread.code = BUS_ADRERR;
 203         current->thread.faddr = address;
 204         goto send_sig;
 205
 206 map_err:
 207         current->thread.signo = SIGSEGV;
 208         current->thread.code = SEGV_MAPERR;
 209         current->thread.faddr = address;
 210         goto send_sig;
 211
 212 acc_err:
 213         current->thread.signo = SIGSEGV;
 214         current->thread.code = SEGV_ACCERR;
 215         current->thread.faddr = address;
 216
 217 send_sig:
 218         up_read(&mm->mmap_sem);
 219         return send_fault_sig(regs);
 220 }