/*
 *  linux/arch/m68k/mm/fault.c
 *
 *  Copyright (C) 1995  Hamish Macdonald
 */

#include <linux/mman.h>
#include <linux/mm.h>
#include <linux/kernel.h>
#include <linux/ptrace.h>
#include <linux/interrupt.h>
#include <linux/module.h>

#include <asm/setup.h>
#include <asm/traps.h>
#include <asm/system.h>
#include <asm/uaccess.h>
#include <asm/pgalloc.h>

extern void die_if_kernel(char *, struct pt_regs *, long);
extern const int frame_extra_sizes[]; /* in m68k/kernel/signal.c */

int send_fault_sig(struct pt_regs *regs)
{
        siginfo_t siginfo = { 0, 0, 0, };

        siginfo.si_signo = current->thread.signo;
        siginfo.si_code = current->thread.code;
        siginfo.si_addr = (void *)current->thread.faddr;
#ifdef DEBUG
        printk("send_fault_sig: %p,%d,%d\n", siginfo.si_addr, siginfo.si_signo, siginfo.si_code);
#endif

        if (user_mode(regs)) {
                force_sig_info(siginfo.si_signo,
                               &siginfo, current);
        } else {
                const struct exception_table_entry *fixup;

                /* Are we prepared to handle this kernel fault? */
                if ((fixup = search_exception_tables(regs->pc))) {
                        struct pt_regs *tregs;
                        /* Create a new four word stack frame, discarding the old
                           one.  */
                        regs->stkadj = frame_extra_sizes[regs->format];
                        tregs = (struct pt_regs *)((ulong)regs + regs->stkadj);
                        tregs->vector = regs->vector;
                        tregs->format = 0;
                        tregs->pc = fixup->fixup;
                        tregs->sr = regs->sr;
                        return -1;
                }

                //if (siginfo.si_signo == SIGBUS)
                //      force_sig_info(siginfo.si_signo,
                //                     &siginfo, current);

                /*
                 * Oops. The kernel tried to access some bad page. We'll have to
                 * terminate things with extreme prejudice.
                 */
                if ((unsigned long)siginfo.si_addr < PAGE_SIZE)
                        printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference");
                else
                        printk(KERN_ALERT "Unable to handle kernel access");
                printk(" at virtual address %p\n", siginfo.si_addr);
                die_if_kernel("Oops", regs, 0 /*error_code*/);
                do_exit(SIGKILL);
        }

        return 1;
}

/*
 * This routine handles page faults.  It determines the problem, and
 * then passes it off to one of the appropriate routines.
 *
 * error_code:
 *      bit 0 == 0 means no page found, 1 means protection fault
 *      bit 1 == 0 means read, 1 means write
 *
 * If this routine detects a bad access, it returns 1, otherwise it
 * returns 0.
 */
int do_page_fault(struct pt_regs *regs, unsigned long address,
                              unsigned long error_code)
{
        struct mm_struct *mm = current->mm;
        struct vm_area_struct * vma;
        int write, fault;

#ifdef DEBUG
        printk ("do page fault:\nregs->sr=%#x, regs->pc=%#lx, address=%#lx, %ld, %p\n",
                regs->sr, regs->pc, address, error_code,
                current->mm->pgd);
#endif

        /*
         * If we're in an interrupt or have no user
         * context, we must not take the fault..
         */
        if (in_atomic() || !mm)
                goto no_context;

        down_read(&mm->mmap_sem);

        vma = find_vma(mm, address);
        if (!vma)
                goto map_err;
        if (vma->vm_flags & VM_IO)
                goto acc_err;
        if (vma->vm_start <= address)
                goto good_area;
        if (!(vma->vm_flags & VM_GROWSDOWN))
                goto map_err;
        if (user_mode(regs)) {
                /* Accessing the stack below usp is always a bug.  The
                   "+ 256" is there due to some instructions doing
                   pre-decrement on the stack and that doesn't show up
                   until later.  */
                if (address + 256 < rdusp())
                        goto map_err;
        }
        if (expand_stack(vma, address))
                goto map_err;

/*
 * Ok, we have a good vm_area for this memory access, so
 * we can handle it..
 */
good_area:
#ifdef DEBUG
        printk("do_page_fault: good_area\n");
#endif
        write = 0;
        switch (error_code & 3) {
                default:        /* 3: write, present */
                        /* fall through */
                case 2:         /* write, not present */
                        if (!(vma->vm_flags & VM_WRITE))
                                goto acc_err;
                        write++;
                        break;
                case 1:         /* read, present */
                        goto acc_err;
                case 0:         /* read, not present */
                        if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
                                goto acc_err;
        }

        /*
         * If for any reason at all we couldn't handle the fault,
         * make sure we exit gracefully rather than endlessly redo
         * the fault.
         */

 survive:
        fault = handle_mm_fault(mm, vma, address, write);
#ifdef DEBUG
        printk("handle_mm_fault returns %d\n",fault);
#endif
        if (unlikely(fault & VM_FAULT_ERROR)) {
                if (fault & VM_FAULT_OOM)
                        goto out_of_memory;
                else if (fault & VM_FAULT_SIGBUS)
                        goto bus_err;
                BUG();
        }
        if (fault & VM_FAULT_MAJOR)
                current->maj_flt++;
        else
                current->min_flt++;

        up_read(&mm->mmap_sem);
        return 0;

/*
 * We ran out of memory, or some other thing happened to us that made
 * us unable to handle the page fault gracefully.
 */
out_of_memory:
        up_read(&mm->mmap_sem);
        if (is_global_init(current)) {
                yield();
                down_read(&mm->mmap_sem);
                goto survive;
        }

        printk("VM: killing process %s\n", current->comm);
        if (user_mode(regs))
                do_group_exit(SIGKILL);

no_context:
        current->thread.signo = SIGBUS;
        current->thread.faddr = address;
        return send_fault_sig(regs);

bus_err:
        current->thread.signo = SIGBUS;
        current->thread.code = BUS_ADRERR;
        current->thread.faddr = address;
        goto send_sig;

map_err:
        current->thread.signo = SIGSEGV;
        current->thread.code = SEGV_MAPERR;
        current->thread.faddr = address;
        goto send_sig;

acc_err:
        current->thread.signo = SIGSEGV;
        current->thread.code = SEGV_ACCERR;
        current->thread.faddr = address;

send_sig:
        up_read(&mm->mmap_sem);
        return send_fault_sig(regs);
}