LXR linux/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
  20extern void die_if_kernel(char *, struct pt_regs *, long);
  21
  22int 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, current);
  34        } else {
  35                if (fixup_exception(regs))
  36                        return -1;
  37
  38                //if (signo == SIGBUS)
  39                //      force_sig_fault(si_signo, si_code, addr, current);
  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 */
  68int 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;
  88retry:
  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 */
 115good_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 */
 187out_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
 194no_context:
 195        current->thread.signo = SIGBUS;
 196        current->thread.faddr = address;
 197        return send_fault_sig(regs);
 198
 199bus_err:
 200        current->thread.signo = SIGBUS;
 201        current->thread.code = BUS_ADRERR;
 202        current->thread.faddr = address;
 203        goto send_sig;
 204
 205map_err:
 206        current->thread.signo = SIGSEGV;
 207        current->thread.code = SEGV_MAPERR;
 208        current->thread.faddr = address;
 209        goto send_sig;
 210
 211acc_err:
 212        current->thread.signo = SIGSEGV;
 213        current->thread.code = SEGV_ACCERR;
 214        current->thread.faddr = address;
 215
 216send_sig:
 217        up_read(&mm->mmap_sem);
 218        return send_fault_sig(regs);
 219}
 220