root/arch/m68k/mm/fault.c

DEFINITIONS

1. send_fault_sig
2. do_page_fault

   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         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_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
  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 retry:
  89         down_read(&mm->mmap_sem);
  90 
  91         vma = find_vma(mm, address);
  92         if (!vma)
  93                 goto map_err;
  94         if (vma->vm_flags & VM_IO)
  95                 goto acc_err;
  96         if (vma->vm_start <= address)
  97                 goto good_area;
  98         if (!(vma->vm_flags & VM_GROWSDOWN))
  99                 goto map_err;
 100         if (user_mode(regs)) {
 101                 /* Accessing the stack below usp is always a bug.  The
 102                    "+ 256" is there due to some instructions doing
 103                    pre-decrement on the stack and that doesn't show up
 104                    until later.  */
 105                 if (address + 256 < rdusp())
 106                         goto map_err;
 107         }
 108         if (expand_stack(vma, address))
 109                 goto map_err;
 110 
 111 /*
 112  * Ok, we have a good vm_area for this memory access, so
 113  * we can handle it..
 114  */
 115 good_area:
 116         pr_debug("do_page_fault: good_area\n");
 117         switch (error_code & 3) {
 118                 default:        /* 3: write, present */
 119                         /* fall through */
 120                 case 2:         /* write, not present */
 121                         if (!(vma->vm_flags & VM_WRITE))
 122                                 goto acc_err;
 123                         flags |= FAULT_FLAG_WRITE;
 124                         break;
 125                 case 1:         /* read, present */
 126                         goto acc_err;
 127                 case 0:         /* read, not present */
 128                         if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
 129                                 goto acc_err;
 130         }
 131 
 132         /*
 133          * If for any reason at all we couldn't handle the fault,
 134          * make sure we exit gracefully rather than endlessly redo
 135          * the fault.
 136          */
 137 
 138         fault = handle_mm_fault(vma, address, flags);
 139         pr_debug("handle_mm_fault returns %x\n", fault);
 140 
 141         if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
 142                 return 0;
 143 
 144         if (unlikely(fault & VM_FAULT_ERROR)) {
 145                 if (fault & VM_FAULT_OOM)
 146                         goto out_of_memory;
 147                 else if (fault & VM_FAULT_SIGSEGV)
 148                         goto map_err;
 149                 else if (fault & VM_FAULT_SIGBUS)
 150                         goto bus_err;
 151                 BUG();
 152         }
 153 
 154         /*
 155          * Major/minor page fault accounting is only done on the
 156          * initial attempt. If we go through a retry, it is extremely
 157          * likely that the page will be found in page cache at that point.
 158          */
 159         if (flags & FAULT_FLAG_ALLOW_RETRY) {
 160                 if (fault & VM_FAULT_MAJOR)
 161                         current->maj_flt++;
 162                 else
 163                         current->min_flt++;
 164                 if (fault & VM_FAULT_RETRY) {
 165                         /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
 166                          * of starvation. */
 167                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
 168                         flags |= FAULT_FLAG_TRIED;
 169 
 170                         /*
 171                          * No need to up_read(&mm->mmap_sem) as we would
 172                          * have already released it in __lock_page_or_retry
 173                          * in mm/filemap.c.
 174                          */
 175 
 176                         goto retry;
 177                 }
 178         }
 179 
 180         up_read(&mm->mmap_sem);
 181         return 0;
 182 
 183 /*
 184  * We ran out of memory, or some other thing happened to us that made
 185  * us unable to handle the page fault gracefully.
 186  */
 187 out_of_memory:
 188         up_read(&mm->mmap_sem);
 189         if (!user_mode(regs))
 190                 goto no_context;
 191         pagefault_out_of_memory();
 192         return 0;
 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 }