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 #include "fault.h"
  21
  22 extern void die_if_kernel(char *, struct pt_regs *, long);
  23
  24 int send_fault_sig(struct pt_regs *regs)
  25 {
  26         int signo, si_code;
  27         void __user *addr;
  28
  29         signo = current->thread.signo;
  30         si_code = current->thread.code;
  31         addr = (void __user *)current->thread.faddr;
  32         pr_debug("send_fault_sig: %p,%d,%d\n", addr, signo, si_code);
  33
  34         if (user_mode(regs)) {
  35                 force_sig_fault(signo, si_code, addr);
  36         } else {
  37                 if (fixup_exception(regs))
  38                         return -1;
  39
  40                 //if (signo == SIGBUS)
  41                 //      force_sig_fault(si_signo, si_code, addr);
  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)addr < PAGE_SIZE)
  48                         pr_alert("Unable to handle kernel NULL pointer dereference");
  49                 else
  50                         pr_alert("Unable to handle kernel access");
  51                 pr_cont(" at virtual address %p\n", addr);
  52                 die_if_kernel("Oops", regs, 0 /*error_code*/);
  53                 make_task_dead(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         vm_fault_t fault;
  76         unsigned int flags = FAULT_FLAG_DEFAULT;
  77
  78         pr_debug("do page fault:\nregs->sr=%#x, regs->pc=%#lx, address=%#lx, %ld, %p\n",
  79                 regs->sr, regs->pc, address, error_code, mm ? mm->pgd : NULL);
  80
  81         /*
  82          * If we're in an interrupt or have no user
  83          * context, we must not take the fault..
  84          */
  85         if (faulthandler_disabled() || !mm)
  86                 goto no_context;
  87
  88         if (user_mode(regs))
  89                 flags |= FAULT_FLAG_USER;
  90
  91         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
  92 retry:
  93         mmap_read_lock(mm);
  94
  95         vma = find_vma(mm, address);
  96         if (!vma)
  97                 goto map_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         vma = expand_stack(mm, address);
 111         if (!vma)
 112                 goto map_err_nosemaphore;
 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         pr_debug("do_page_fault: good_area\n");
 120         switch (error_code & 3) {
 121                 default:        /* 3: write, present */
 122                         fallthrough;
 123                 case 2:         /* write, not present */
 124                         if (!(vma->vm_flags & VM_WRITE))
 125                                 goto acc_err;
 126                         flags |= FAULT_FLAG_WRITE;
 127                         break;
 128                 case 1:         /* read, present */
 129                         goto acc_err;
 130                 case 0:         /* read, not present */
 131                         if (unlikely(!vma_is_accessible(vma)))
 132                                 goto acc_err;
 133         }
 134
 135         /*
 136          * If for any reason at all we couldn't handle the fault,
 137          * make sure we exit gracefully rather than endlessly redo
 138          * the fault.
 139          */
 140
 141         fault = handle_mm_fault(vma, address, flags, regs);
 142         pr_debug("handle_mm_fault returns %x\n", fault);
 143
 144         if (fault_signal_pending(fault, regs)) {
 145                 if (!user_mode(regs))
 146                         goto no_context;
 147                 return 0;
 148         }
 149
 150         /* The fault is fully completed (including releasing mmap lock) */
 151         if (fault & VM_FAULT_COMPLETED)
 152                 return 0;
 153
 154         if (unlikely(fault & VM_FAULT_ERROR)) {
 155                 if (fault & VM_FAULT_OOM)
 156                         goto out_of_memory;
 157                 else if (fault & VM_FAULT_SIGSEGV)
 158                         goto map_err;
 159                 else if (fault & VM_FAULT_SIGBUS)
 160                         goto bus_err;
 161                 BUG();
 162         }
 163
 164         if (fault & VM_FAULT_RETRY) {
 165                 flags |= FAULT_FLAG_TRIED;
 166
 167                 /*
 168                  * No need to mmap_read_unlock(mm) as we would
 169                  * have already released it in __lock_page_or_retry
 170                  * in mm/filemap.c.
 171                  */
 172
 173                 goto retry;
 174         }
 175
 176         mmap_read_unlock(mm);
 177         return 0;
 178
 179 /*
 180  * We ran out of memory, or some other thing happened to us that made
 181  * us unable to handle the page fault gracefully.
 182  */
 183 out_of_memory:
 184         mmap_read_unlock(mm);
 185         if (!user_mode(regs))
 186                 goto no_context;
 187         pagefault_out_of_memory();
 188         return 0;
 189
 190 no_context:
 191         current->thread.signo = SIGBUS;
 192         current->thread.faddr = address;
 193         return send_fault_sig(regs);
 194
 195 bus_err:
 196         current->thread.signo = SIGBUS;
 197         current->thread.code = BUS_ADRERR;
 198         current->thread.faddr = address;
 199         goto send_sig;
 200
 201 map_err:
 202         mmap_read_unlock(mm);
 203 map_err_nosemaphore:
 204         current->thread.signo = SIGSEGV;
 205         current->thread.code = SEGV_MAPERR;
 206         current->thread.faddr = address;
 207         return send_fault_sig(regs);
 208
 209 acc_err:
 210         current->thread.signo = SIGSEGV;
 211         current->thread.code = SEGV_ACCERR;
 212         current->thread.faddr = address;
 213
 214 send_sig:
 215         mmap_read_unlock(mm);
 216         return send_fault_sig(regs);
 217 }