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   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/system.h>
  17 #include <asm/uaccess.h>
  18 #include <asm/pgalloc.h>
  19
  20 extern void die_if_kernel(char *, struct pt_regs *, long);
  21 extern const int frame_extra_sizes[]; /* in m68k/kernel/signal.c */
  22
  23 int send_fault_sig(struct pt_regs *regs)
  24 {
  25         siginfo_t siginfo = { 0, 0, 0, };
  26
  27         siginfo.si_signo = current->thread.signo;
  28         siginfo.si_code = current->thread.code;
  29         siginfo.si_addr = (void *)current->thread.faddr;
  30 #ifdef DEBUG
  31         printk("send_fault_sig: %p,%d,%d\n", siginfo.si_addr, siginfo.si_signo, siginfo.si_code);
  32 #endif
  33
  34         if (user_mode(regs)) {
  35                 force_sig_info(siginfo.si_signo,
  36                                &siginfo, current);
  37         } else {
  38                 const struct exception_table_entry *fixup;
  39
  40                 /* Are we prepared to handle this kernel fault? */
  41                 if ((fixup = search_exception_tables(regs->pc))) {
  42                         struct pt_regs *tregs;
  43                         /* Create a new four word stack frame, discarding the old
  44                            one.  */
  45                         regs->stkadj = frame_extra_sizes[regs->format];
  46                         tregs = (struct pt_regs *)((ulong)regs + regs->stkadj);
  47                         tregs->vector = regs->vector;
  48                         tregs->format = 0;
  49                         tregs->pc = fixup->fixup;
  50                         tregs->sr = regs->sr;
  51                         return -1;
  52                 }
  53
  54                 //if (siginfo.si_signo == SIGBUS)
  55                 //      force_sig_info(siginfo.si_signo,
  56                 //                     &siginfo, current);
  57
  58                 /*
  59                  * Oops. The kernel tried to access some bad page. We'll have to
  60                  * terminate things with extreme prejudice.
  61                  */
  62                 if ((unsigned long)siginfo.si_addr < PAGE_SIZE)
  63                         printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference");
  64                 else
  65                         printk(KERN_ALERT "Unable to handle kernel access");
  66                 printk(" at virtual address %p\n", siginfo.si_addr);
  67                 die_if_kernel("Oops", regs, 0 /*error_code*/);
  68                 do_exit(SIGKILL);
  69         }
  70
  71         return 1;
  72 }
  73
  74 /*
  75  * This routine handles page faults.  It determines the problem, and
  76  * then passes it off to one of the appropriate routines.
  77  *
  78  * error_code:
  79  *      bit 0 == 0 means no page found, 1 means protection fault
  80  *      bit 1 == 0 means read, 1 means write
  81  *
  82  * If this routine detects a bad access, it returns 1, otherwise it
  83  * returns 0.
  84  */
  85 int do_page_fault(struct pt_regs *regs, unsigned long address,
  86                               unsigned long error_code)
  87 {
  88         struct mm_struct *mm = current->mm;
  89         struct vm_area_struct * vma;
  90         int write, fault;
  91
  92 #ifdef DEBUG
  93         printk ("do page fault:\nregs->sr=%#x, regs->pc=%#lx, address=%#lx, %ld, %p\n",
  94                 regs->sr, regs->pc, address, error_code,
  95                 current->mm->pgd);
  96 #endif
  97
  98         /*
  99          * If we're in an interrupt or have no user
 100          * context, we must not take the fault..
 101          */
 102         if (in_interrupt() || !mm)
 103                 goto no_context;
 104
 105         down_read(&mm->mmap_sem);
 106
 107         vma = find_vma(mm, address);
 108         if (!vma)
 109                 goto map_err;
 110         if (vma->vm_flags & VM_IO)
 111                 goto acc_err;
 112         if (vma->vm_start <= address)
 113                 goto good_area;
 114         if (!(vma->vm_flags & VM_GROWSDOWN))
 115                 goto map_err;
 116         if (user_mode(regs)) {
 117                 /* Accessing the stack below usp is always a bug.  The
 118                    "+ 256" is there due to some instructions doing
 119                    pre-decrement on the stack and that doesn't show up
 120                    until later.  */
 121                 if (address + 256 < rdusp())
 122                         goto map_err;
 123         }
 124         if (expand_stack(vma, address))
 125                 goto map_err;
 126
 127 /*
 128  * Ok, we have a good vm_area for this memory access, so
 129  * we can handle it..
 130  */
 131 good_area:
 132 #ifdef DEBUG
 133         printk("do_page_fault: good_area\n");
 134 #endif
 135         write = 0;
 136         switch (error_code & 3) {
 137                 default:        /* 3: write, present */
 138                         /* fall through */
 139                 case 2:         /* write, not present */
 140                         if (!(vma->vm_flags & VM_WRITE))
 141                                 goto acc_err;
 142                         write++;
 143                         break;
 144                 case 1:         /* read, present */
 145                         goto acc_err;
 146                 case 0:         /* read, not present */
 147                         if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
 148                                 goto acc_err;
 149         }
 150
 151         /*
 152          * If for any reason at all we couldn't handle the fault,
 153          * make sure we exit gracefully rather than endlessly redo
 154          * the fault.
 155          */
 156
 157  survive:
 158         fault = handle_mm_fault(mm, vma, address, write);
 159 #ifdef DEBUG
 160         printk("handle_mm_fault returns %d\n",fault);
 161 #endif
 162         switch (fault) {
 163         case VM_FAULT_MINOR:
 164                 current->min_flt++;
 165                 break;
 166         case VM_FAULT_MAJOR:
 167                 current->maj_flt++;
 168                 break;
 169         case VM_FAULT_SIGBUS:
 170                 goto bus_err;
 171         default:
 172                 goto out_of_memory;
 173         }
 174
 175         up_read(&mm->mmap_sem);
 176         return 0;
 177
 178 /*
 179  * We ran out of memory, or some other thing happened to us that made
 180  * us unable to handle the page fault gracefully.
 181  */
 182 out_of_memory:
 183         up_read(&mm->mmap_sem);
 184         if (current->pid == 1) {
 185                 yield();
 186                 down_read(&mm->mmap_sem);
 187                 goto survive;
 188         }
 189
 190         printk("VM: killing process %s\n", current->comm);
 191         if (user_mode(regs))
 192                 do_exit(SIGKILL);
 193
 194 no_context:
 195         current->thread.signo = SIGBUS;
 196         current->thread.faddr = address;
 197         return send_fault_sig(regs);
 198
 199 bus_err:
 200         current->thread.signo = SIGBUS;
 201         current->thread.code = BUS_ADRERR;
 202         current->thread.faddr = address;
 203         goto send_sig;
 204
 205 map_err:
 206         current->thread.signo = SIGSEGV;
 207         current->thread.code = SEGV_MAPERR;
 208         current->thread.faddr = address;
 209         goto send_sig;
 210
 211 acc_err:
 212         current->thread.signo = SIGSEGV;
 213         current->thread.code = SEGV_ACCERR;
 214         current->thread.faddr = address;
 215
 216 send_sig:
 217         up_read(&mm->mmap_sem);
 218         return send_fault_sig(regs);
 219 }