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
  16 #include <asm/setup.h>
  17 #include <asm/traps.h>
  18 #include <asm/pgalloc.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         siginfo_t siginfo = { 0, 0, 0, };
  25
  26         siginfo.si_signo = current->thread.signo;
  27         siginfo.si_code = current->thread.code;
  28         siginfo.si_addr = (void *)current->thread.faddr;
  29         pr_debug("send_fault_sig: %p,%d,%d\n", siginfo.si_addr,
  30                  siginfo.si_signo, siginfo.si_code);
  31
  32         if (user_mode(regs)) {
  33                 force_sig_info(siginfo.si_signo,
  34                                &siginfo, current);
  35         } else {
  36                 if (fixup_exception(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                         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", 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         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 retry:
  91         down_read(&mm->mmap_sem);
  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                         /* fall through */
 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 (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
 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);
 141         pr_debug("handle_mm_fault returns %d\n", fault);
 142
 143         if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
 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         /*
 157          * Major/minor page fault accounting is only done on the
 158          * initial attempt. If we go through a retry, it is extremely
 159          * likely that the page will be found in page cache at that point.
 160          */
 161         if (flags & FAULT_FLAG_ALLOW_RETRY) {
 162                 if (fault & VM_FAULT_MAJOR)
 163                         current->maj_flt++;
 164                 else
 165                         current->min_flt++;
 166                 if (fault & VM_FAULT_RETRY) {
 167                         /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
 168                          * of starvation. */
 169                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
 170                         flags |= FAULT_FLAG_TRIED;
 171
 172                         /*
 173                          * No need to up_read(&mm->mmap_sem) as we would
 174                          * have already released it in __lock_page_or_retry
 175                          * in mm/filemap.c.
 176                          */
 177
 178                         goto retry;
 179                 }
 180         }
 181
 182         up_read(&mm->mmap_sem);
 183         return 0;
 184
 185 /*
 186  * We ran out of memory, or some other thing happened to us that made
 187  * us unable to handle the page fault gracefully.
 188  */
 189 out_of_memory:
 190         up_read(&mm->mmap_sem);
 191         if (!user_mode(regs))
 192                 goto no_context;
 193         pagefault_out_of_memory();
 194         return 0;
 195
 196 no_context:
 197         current->thread.signo = SIGBUS;
 198         current->thread.faddr = address;
 199         return send_fault_sig(regs);
 200
 201 bus_err:
 202         current->thread.signo = SIGBUS;
 203         current->thread.code = BUS_ADRERR;
 204         current->thread.faddr = address;
 205         goto send_sig;
 206
 207 map_err:
 208         current->thread.signo = SIGSEGV;
 209         current->thread.code = SEGV_MAPERR;
 210         current->thread.faddr = address;
 211         goto send_sig;
 212
 213 acc_err:
 214         current->thread.signo = SIGSEGV;
 215         current->thread.code = SEGV_ACCERR;
 216         current->thread.faddr = address;
 217
 218 send_sig:
 219         up_read(&mm->mmap_sem);
 220         return send_fault_sig(regs);
 221 }