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;
  25
  26         clear_siginfo(&siginfo);
  27         siginfo.si_signo = current->thread.signo;
  28         siginfo.si_code = current->thread.code;
  29         siginfo.si_addr = (void *)current->thread.faddr;
  30         pr_debug("send_fault_sig: %p,%d,%d\n", siginfo.si_addr,
  31                  siginfo.si_signo, siginfo.si_code);
  32
  33         if (user_mode(regs)) {
  34                 force_sig_info(siginfo.si_signo,
  35                                &siginfo, current);
  36         } else {
  37                 if (fixup_exception(regs))
  38                         return -1;
  39
  40                 //if (siginfo.si_signo == SIGBUS)
  41                 //      force_sig_info(siginfo.si_signo,
  42                 //                     &siginfo, current);
  43
  44                 /*
  45                  * Oops. The kernel tried to access some bad page. We'll have to
  46                  * terminate things with extreme prejudice.
  47                  */
  48                 if ((unsigned long)siginfo.si_addr < PAGE_SIZE)
  49                         pr_alert("Unable to handle kernel NULL pointer dereference");
  50                 else
  51                         pr_alert("Unable to handle kernel access");
  52                 pr_cont(" at virtual address %p\n", siginfo.si_addr);
  53                 die_if_kernel("Oops", regs, 0 /*error_code*/);
  54                 do_exit(SIGKILL);
  55         }
  56
  57         return 1;
  58 }
  59
  60 /*
  61  * This routine handles page faults.  It determines the problem, and
  62  * then passes it off to one of the appropriate routines.
  63  *
  64  * error_code:
  65  *      bit 0 == 0 means no page found, 1 means protection fault
  66  *      bit 1 == 0 means read, 1 means write
  67  *
  68  * If this routine detects a bad access, it returns 1, otherwise it
  69  * returns 0.
  70  */
  71 int do_page_fault(struct pt_regs *regs, unsigned long address,
  72                               unsigned long error_code)
  73 {
  74         struct mm_struct *mm = current->mm;
  75         struct vm_area_struct * vma;
  76         int fault;
  77         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
  78
  79         pr_debug("do page fault:\nregs->sr=%#x, regs->pc=%#lx, address=%#lx, %ld, %p\n",
  80                 regs->sr, regs->pc, address, error_code, mm ? mm->pgd : NULL);
  81
  82         /*
  83          * If we're in an interrupt or have no user
  84          * context, we must not take the fault..
  85          */
  86         if (faulthandler_disabled() || !mm)
  87                 goto no_context;
  88
  89         if (user_mode(regs))
  90                 flags |= FAULT_FLAG_USER;
  91 retry:
  92         down_read(&mm->mmap_sem);
  93
  94         vma = find_vma(mm, address);
  95         if (!vma)
  96                 goto map_err;
  97         if (vma->vm_flags & VM_IO)
  98                 goto acc_err;
  99         if (vma->vm_start <= address)
 100                 goto good_area;
 101         if (!(vma->vm_flags & VM_GROWSDOWN))
 102                 goto map_err;
 103         if (user_mode(regs)) {
 104                 /* Accessing the stack below usp is always a bug.  The
 105                    "+ 256" is there due to some instructions doing
 106                    pre-decrement on the stack and that doesn't show up
 107                    until later.  */
 108                 if (address + 256 < rdusp())
 109                         goto map_err;
 110         }
 111         if (expand_stack(vma, address))
 112                 goto map_err;
 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                         /* fall through */
 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 (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
 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);
 142         pr_debug("handle_mm_fault returns %d\n", fault);
 143
 144         if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
 145                 return 0;
 146
 147         if (unlikely(fault & VM_FAULT_ERROR)) {
 148                 if (fault & VM_FAULT_OOM)
 149                         goto out_of_memory;
 150                 else if (fault & VM_FAULT_SIGSEGV)
 151                         goto map_err;
 152                 else if (fault & VM_FAULT_SIGBUS)
 153                         goto bus_err;
 154                 BUG();
 155         }
 156
 157         /*
 158          * Major/minor page fault accounting is only done on the
 159          * initial attempt. If we go through a retry, it is extremely
 160          * likely that the page will be found in page cache at that point.
 161          */
 162         if (flags & FAULT_FLAG_ALLOW_RETRY) {
 163                 if (fault & VM_FAULT_MAJOR)
 164                         current->maj_flt++;
 165                 else
 166                         current->min_flt++;
 167                 if (fault & VM_FAULT_RETRY) {
 168                         /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
 169                          * of starvation. */
 170                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
 171                         flags |= FAULT_FLAG_TRIED;
 172
 173                         /*
 174                          * No need to up_read(&mm->mmap_sem) as we would
 175                          * have already released it in __lock_page_or_retry
 176                          * in mm/filemap.c.
 177                          */
 178
 179                         goto retry;
 180                 }
 181         }
 182
 183         up_read(&mm->mmap_sem);
 184         return 0;
 185
 186 /*
 187  * We ran out of memory, or some other thing happened to us that made
 188  * us unable to handle the page fault gracefully.
 189  */
 190 out_of_memory:
 191         up_read(&mm->mmap_sem);
 192         if (!user_mode(regs))
 193                 goto no_context;
 194         pagefault_out_of_memory();
 195         return 0;
 196
 197 no_context:
 198         current->thread.signo = SIGBUS;
 199         current->thread.faddr = address;
 200         return send_fault_sig(regs);
 201
 202 bus_err:
 203         current->thread.signo = SIGBUS;
 204         current->thread.code = BUS_ADRERR;
 205         current->thread.faddr = address;
 206         goto send_sig;
 207
 208 map_err:
 209         current->thread.signo = SIGSEGV;
 210         current->thread.code = SEGV_MAPERR;
 211         current->thread.faddr = address;
 212         goto send_sig;
 213
 214 acc_err:
 215         current->thread.signo = SIGSEGV;
 216         current->thread.code = SEGV_ACCERR;
 217         current->thread.faddr = address;
 218
 219 send_sig:
 220         up_read(&mm->mmap_sem);
 221         return send_fault_sig(regs);
 222 }