arch/m68k/mm/fault.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *  linux/arch/m68k/mm/fault.c
   4  *
   5  *  Copyright (C) 1995  Hamish Macdonald
   6  */
   7
   8 #include <linux/mman.h>
   9 #include <linux/mm.h>
  10 #include <linux/kernel.h>
  11 #include <linux/ptrace.h>
  12 #include <linux/interrupt.h>
  13 #include <linux/module.h>
  14 #include <linux/uaccess.h>
  15 #include <linux/perf_event.h>
  16
  17 #include <asm/setup.h>
  18 #include <asm/traps.h>
  19
  20 extern void die_if_kernel(char *, struct pt_regs *, long);
  21
  22 int send_fault_sig(struct pt_regs *regs)
  23 {
  24         int signo, si_code;
  25         void __user *addr;
  26
  27         signo = current->thread.signo;
  28         si_code = current->thread.code;
  29         addr = (void __user *)current->thread.faddr;
  30         pr_debug("send_fault_sig: %p,%d,%d\n", addr, signo, si_code);
  31
  32         if (user_mode(regs)) {
  33                 force_sig_fault(signo, si_code, addr);
  34         } else {
  35                 if (fixup_exception(regs))
  36                         return -1;
  37
  38                 //if (signo == SIGBUS)
  39                 //      force_sig_fault(si_signo, si_code, addr);
  40
  41                 /*
  42                  * Oops. The kernel tried to access some bad page. We'll have to
  43                  * terminate things with extreme prejudice.
  44                  */
  45                 if ((unsigned long)addr < PAGE_SIZE)
  46                         pr_alert("Unable to handle kernel NULL pointer dereference");
  47                 else
  48                         pr_alert("Unable to handle kernel access");
  49                 pr_cont(" at virtual address %p\n", addr);
  50                 die_if_kernel("Oops", regs, 0 /*error_code*/);
  51                 do_exit(SIGKILL);
  52         }
  53
  54         return 1;
  55 }
  56
  57 /*
  58  * This routine handles page faults.  It determines the problem, and
  59  * then passes it off to one of the appropriate routines.
  60  *
  61  * error_code:
  62  *      bit 0 == 0 means no page found, 1 means protection fault
  63  *      bit 1 == 0 means read, 1 means write
  64  *
  65  * If this routine detects a bad access, it returns 1, otherwise it
  66  * returns 0.
  67  */
  68 int do_page_fault(struct pt_regs *regs, unsigned long address,
  69                               unsigned long error_code)
  70 {
  71         struct mm_struct *mm = current->mm;
  72         struct vm_area_struct * vma;
  73         vm_fault_t fault;
  74         unsigned int flags = FAULT_FLAG_DEFAULT;
  75
  76         pr_debug("do page fault:\nregs->sr=%#x, regs->pc=%#lx, address=%#lx, %ld, %p\n",
  77                 regs->sr, regs->pc, address, error_code, mm ? mm->pgd : NULL);
  78
  79         /*
  80          * If we're in an interrupt or have no user
  81          * context, we must not take the fault..
  82          */
  83         if (faulthandler_disabled() || !mm)
  84                 goto no_context;
  85
  86         if (user_mode(regs))
  87                 flags |= FAULT_FLAG_USER;
  88
  89         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
  90 retry:
  91         mmap_read_lock(mm);
  92
  93         vma = find_vma(mm, address);
  94         if (!vma)
  95                 goto map_err;
  96         if (vma->vm_flags & VM_IO)
  97                 goto acc_err;
  98         if (vma->vm_start <= address)
  99                 goto good_area;
 100         if (!(vma->vm_flags & VM_GROWSDOWN))
 101                 goto map_err;
 102         if (user_mode(regs)) {
 103                 /* Accessing the stack below usp is always a bug.  The
 104                    "+ 256" is there due to some instructions doing
 105                    pre-decrement on the stack and that doesn't show up
 106                    until later.  */
 107                 if (address + 256 < rdusp())
 108                         goto map_err;
 109         }
 110         if (expand_stack(vma, address))
 111                 goto map_err;
 112
 113 /*
 114  * Ok, we have a good vm_area for this memory access, so
 115  * we can handle it..
 116  */
 117 good_area:
 118         pr_debug("do_page_fault: good_area\n");
 119         switch (error_code & 3) {
 120                 default:        /* 3: write, present */
 121                         fallthrough;
 122                 case 2:         /* write, not present */
 123                         if (!(vma->vm_flags & VM_WRITE))
 124                                 goto acc_err;
 125                         flags |= FAULT_FLAG_WRITE;
 126                         break;
 127                 case 1:         /* read, present */
 128                         goto acc_err;
 129                 case 0:         /* read, not present */
 130                         if (unlikely(!vma_is_accessible(vma)))
 131                                 goto acc_err;
 132         }
 133
 134         /*
 135          * If for any reason at all we couldn't handle the fault,
 136          * make sure we exit gracefully rather than endlessly redo
 137          * the fault.
 138          */
 139
 140         fault = handle_mm_fault(vma, address, flags, regs);
 141         pr_debug("handle_mm_fault returns %x\n", fault);
 142
 143         if (fault_signal_pending(fault, regs))
 144                 return 0;
 145
 146         if (unlikely(fault & VM_FAULT_ERROR)) {
 147                 if (fault & VM_FAULT_OOM)
 148                         goto out_of_memory;
 149                 else if (fault & VM_FAULT_SIGSEGV)
 150                         goto map_err;
 151                 else if (fault & VM_FAULT_SIGBUS)
 152                         goto bus_err;
 153                 BUG();
 154         }
 155
 156         if (flags & FAULT_FLAG_ALLOW_RETRY) {
 157                 if (fault & VM_FAULT_RETRY) {
 158                         flags |= FAULT_FLAG_TRIED;
 159
 160                         /*
 161                          * No need to mmap_read_unlock(mm) as we would
 162                          * have already released it in __lock_page_or_retry
 163                          * in mm/filemap.c.
 164                          */
 165
 166                         goto retry;
 167                 }
 168         }
 169
 170         mmap_read_unlock(mm);
 171         return 0;
 172
 173 /*
 174  * We ran out of memory, or some other thing happened to us that made
 175  * us unable to handle the page fault gracefully.
 176  */
 177 out_of_memory:
 178         mmap_read_unlock(mm);
 179         if (!user_mode(regs))
 180                 goto no_context;
 181         pagefault_out_of_memory();
 182         return 0;
 183
 184 no_context:
 185         current->thread.signo = SIGBUS;
 186         current->thread.faddr = address;
 187         return send_fault_sig(regs);
 188
 189 bus_err:
 190         current->thread.signo = SIGBUS;
 191         current->thread.code = BUS_ADRERR;
 192         current->thread.faddr = address;
 193         goto send_sig;
 194
 195 map_err:
 196         current->thread.signo = SIGSEGV;
 197         current->thread.code = SEGV_MAPERR;
 198         current->thread.faddr = address;
 199         goto send_sig;
 200
 201 acc_err:
 202         current->thread.signo = SIGSEGV;
 203         current->thread.code = SEGV_ACCERR;
 204         current->thread.faddr = address;
 205
 206 send_sig:
 207         mmap_read_unlock(mm);
 208         return send_fault_sig(regs);
 209 }