/* MN10300 MMU Fault handler
 *
 * Copyright (C) 2007 Matsushita Electric Industrial Co., Ltd.
 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
 * Modified by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public Licence
 * as published by the Free Software Foundation; either version
 * 2 of the Licence, or (at your option) any later version.
 */

#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/ptrace.h>
#include <linux/mman.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/interrupt.h>
#include <linux/init.h>
#include <linux/vt_kern.h>              /* For unblank_screen() */
#include <linux/uaccess.h>

#include <asm/pgalloc.h>
#include <asm/hardirq.h>
#include <asm/cpu-regs.h>
#include <asm/debugger.h>
#include <asm/gdb-stub.h>

/*
 * Unlock any spinlocks which will prevent us from getting the
 * message out
 */
void bust_spinlocks(int yes)
{
        if (yes) {
                oops_in_progress = 1;
        } else {
                int loglevel_save = console_loglevel;
#ifdef CONFIG_VT
                unblank_screen();
#endif
                oops_in_progress = 0;
                /*
                 * OK, the message is on the console.  Now we call printk()
                 * without oops_in_progress set so that printk will give klogd
                 * a poke.  Hold onto your hats...
                 */
                console_loglevel = 15;  /* NMI oopser may have shut the console
                                         * up */
                printk(" ");
                console_loglevel = loglevel_save;
        }
}

void do_BUG(const char *file, int line)
{
        bust_spinlocks(1);
        printk(KERN_EMERG "------------[ cut here ]------------\n");
        printk(KERN_EMERG "kernel BUG at %s:%d!\n", file, line);
}

#if 0
static void print_pagetable_entries(pgd_t *pgdir, unsigned long address)
{
        pgd_t *pgd;
        pmd_t *pmd;
        pte_t *pte;

        pgd = pgdir + __pgd_offset(address);
        printk(KERN_DEBUG "pgd entry %p: %016Lx\n",
               pgd, (long long) pgd_val(*pgd));

        if (!pgd_present(*pgd)) {
                printk(KERN_DEBUG "... pgd not present!\n");
                return;
        }
        pmd = pmd_offset(pgd, address);
        printk(KERN_DEBUG "pmd entry %p: %016Lx\n",
               pmd, (long long)pmd_val(*pmd));

        if (!pmd_present(*pmd)) {
                printk(KERN_DEBUG "... pmd not present!\n");
                return;
        }
        pte = pte_offset(pmd, address);
        printk(KERN_DEBUG "pte entry %p: %016Lx\n",
               pte, (long long) pte_val(*pte));

        if (!pte_present(*pte))
                printk(KERN_DEBUG "... pte not present!\n");
}
#endif

/*
 * This routine handles page faults.  It determines the address,
 * and the problem, and then passes it off to one of the appropriate
 * routines.
 *
 * fault_code:
 * - LSW: either MMUFCR_IFC or MMUFCR_DFC as appropriate
 * - MSW: 0 if data access, 1 if instruction access
 * - bit 0: TLB miss flag
 * - bit 1: initial write
 * - bit 2: page invalid
 * - bit 3: protection violation
 * - bit 4: accessor (0=user 1=kernel)
 * - bit 5: 0=read 1=write
 * - bit 6-8: page protection spec
 * - bit 9: illegal address
 * - bit 16: 0=data 1=ins
 *
 */
asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long fault_code,
                              unsigned long address)
{
        struct vm_area_struct *vma;
        struct task_struct *tsk;
        struct mm_struct *mm;
        unsigned long page;
        siginfo_t info;
        int fault;
        unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;

#ifdef CONFIG_GDBSTUB
        /* handle GDB stub causing a fault */
        if (gdbstub_busy) {
                gdbstub_exception(regs, TBR & TBR_INT_CODE);
                return;
        }
#endif

#if 0
        printk(KERN_DEBUG "--- do_page_fault(%p,%s:%04lx,%08lx)\n",
               regs,
               fault_code & 0x10000 ? "ins" : "data",
               fault_code & 0xffff, address);
#endif

        tsk = current;

        /*
         * We fault-in kernel-space virtual memory on-demand. The
         * 'reference' page table is init_mm.pgd.
         *
         * NOTE! We MUST NOT take any locks for this case. We may
         * be in an interrupt or a critical region, and should
         * only copy the information from the master page table,
         * nothing more.
         *
         * This verifies that the fault happens in kernel space
         * and that the fault was a page not present (invalid) error
         */
        if (address >= VMALLOC_START && address < VMALLOC_END &&
            (fault_code & MMUFCR_xFC_ACCESS) == MMUFCR_xFC_ACCESS_SR &&
            (fault_code & MMUFCR_xFC_PGINVAL) == MMUFCR_xFC_PGINVAL
            )
                goto vmalloc_fault;

        mm = tsk->mm;
        info.si_code = SEGV_MAPERR;

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

        if ((fault_code & MMUFCR_xFC_ACCESS) == MMUFCR_xFC_ACCESS_USR)
                flags |= FAULT_FLAG_USER;
retry:
        down_read(&mm->mmap_sem);

        vma = find_vma(mm, address);
        if (!vma)
                goto bad_area;
        if (vma->vm_start <= address)
                goto good_area;
        if (!(vma->vm_flags & VM_GROWSDOWN))
                goto bad_area;

        if ((fault_code & MMUFCR_xFC_ACCESS) == MMUFCR_xFC_ACCESS_USR) {
                /* accessing the stack below the stack pointer is always a
                 * bug */
                if ((address & PAGE_MASK) + 2 * PAGE_SIZE < regs->sp) {
#if 0
                        printk(KERN_WARNING
                               "[%d] ### Access below stack @%lx (sp=%lx)\n",
                               current->pid, address, regs->sp);
                        printk(KERN_WARNING
                               "vma [%08x - %08x]\n",
                               vma->vm_start, vma->vm_end);
                        show_registers(regs);
                        printk(KERN_WARNING
                               "[%d] ### Code: [%08lx]"
                               " %02x %02x %02x %02x %02x %02x %02x %02x\n",
                               current->pid,
                               regs->pc,
                               ((u8 *) regs->pc)[0],
                               ((u8 *) regs->pc)[1],
                               ((u8 *) regs->pc)[2],
                               ((u8 *) regs->pc)[3],
                               ((u8 *) regs->pc)[4],
                               ((u8 *) regs->pc)[5],
                               ((u8 *) regs->pc)[6],
                               ((u8 *) regs->pc)[7]
                               );
#endif
                        goto bad_area;
                }
        }

        if (expand_stack(vma, address))
                goto bad_area;

/*
 * Ok, we have a good vm_area for this memory access, so
 * we can handle it..
 */
good_area:
        info.si_code = SEGV_ACCERR;
        switch (fault_code & (MMUFCR_xFC_PGINVAL|MMUFCR_xFC_TYPE)) {
        default:        /* 3: write, present */
        case MMUFCR_xFC_TYPE_WRITE:
#ifdef TEST_VERIFY_AREA
                if ((fault_code & MMUFCR_xFC_ACCESS) == MMUFCR_xFC_ACCESS_SR)
                        printk(KERN_DEBUG "WP fault at %08lx\n", regs->pc);
#endif
                /* write to absent page */
        case MMUFCR_xFC_PGINVAL | MMUFCR_xFC_TYPE_WRITE:
                if (!(vma->vm_flags & VM_WRITE))
                        goto bad_area;
                flags |= FAULT_FLAG_WRITE;
                break;

                /* read from protected page */
        case MMUFCR_xFC_TYPE_READ:
                goto bad_area;

                /* read from absent page present */
        case MMUFCR_xFC_PGINVAL | MMUFCR_xFC_TYPE_READ:
                if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
                        goto bad_area;
                break;
        }

        /*
         * If for any reason at all we couldn't handle the fault,
         * make sure we exit gracefully rather than endlessly redo
         * the fault.
         */
        fault = handle_mm_fault(mm, vma, address, flags);

        if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
                return;

        if (unlikely(fault & VM_FAULT_ERROR)) {
                if (fault & VM_FAULT_OOM)
                        goto out_of_memory;
                else if (fault & VM_FAULT_SIGSEGV)
                        goto bad_area;
                else if (fault & VM_FAULT_SIGBUS)
                        goto do_sigbus;
                BUG();
        }
        if (flags & FAULT_FLAG_ALLOW_RETRY) {
                if (fault & VM_FAULT_MAJOR)
                        current->maj_flt++;
                else
                        current->min_flt++;
                if (fault & VM_FAULT_RETRY) {
                        flags &= ~FAULT_FLAG_ALLOW_RETRY;

                         /* No need to up_read(&mm->mmap_sem) as we would
                         * have already released it in __lock_page_or_retry
                         * in mm/filemap.c.
                         */

                        goto retry;
                }
        }

        up_read(&mm->mmap_sem);
        return;

/*
 * Something tried to access memory that isn't in our memory map..
 * Fix it, but check if it's kernel or user first..
 */
bad_area:
        up_read(&mm->mmap_sem);

        /* User mode accesses just cause a SIGSEGV */
        if ((fault_code & MMUFCR_xFC_ACCESS) == MMUFCR_xFC_ACCESS_USR) {
                info.si_signo = SIGSEGV;
                info.si_errno = 0;
                /* info.si_code has been set above */
                info.si_addr = (void *)address;
                force_sig_info(SIGSEGV, &info, tsk);
                return;
        }

no_context:
        /* Are we prepared to handle this kernel fault?  */
        if (fixup_exception(regs))
                return;

/*
 * Oops. The kernel tried to access some bad page. We'll have to
 * terminate things with extreme prejudice.
 */

        bust_spinlocks(1);

        if (address < PAGE_SIZE)
                printk(KERN_ALERT
                       "Unable to handle kernel NULL pointer dereference");
        else
                printk(KERN_ALERT
                       "Unable to handle kernel paging request");
        printk(" at virtual address %08lx\n", address);
        printk(" printing pc:\n");
        printk(KERN_ALERT "%08lx\n", regs->pc);

        debugger_intercept(fault_code & 0x00010000 ? EXCEP_IAERROR : EXCEP_DAERROR,
                           SIGSEGV, SEGV_ACCERR, regs);

        page = PTBR;
        page = ((unsigned long *) __va(page))[address >> 22];
        printk(KERN_ALERT "*pde = %08lx\n", page);
        if (page & 1) {
                page &= PAGE_MASK;
                address &= 0x003ff000;
                page = ((unsigned long *) __va(page))[address >> PAGE_SHIFT];
                printk(KERN_ALERT "*pte = %08lx\n", page);
        }

        die("Oops", regs, fault_code);
        do_exit(SIGKILL);

/*
 * 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 ((fault_code & MMUFCR_xFC_ACCESS) == MMUFCR_xFC_ACCESS_USR) {
                pagefault_out_of_memory();
                return;
        }
        goto no_context;

do_sigbus:
        up_read(&mm->mmap_sem);

        /*
         * Send a sigbus, regardless of whether we were in kernel
         * or user mode.
         */
        info.si_signo = SIGBUS;
        info.si_errno = 0;
        info.si_code = BUS_ADRERR;
        info.si_addr = (void *)address;
        force_sig_info(SIGBUS, &info, tsk);

        /* Kernel mode? Handle exceptions or die */
        if ((fault_code & MMUFCR_xFC_ACCESS) == MMUFCR_xFC_ACCESS_SR)
                goto no_context;
        return;

vmalloc_fault:
        {
                /*
                 * Synchronize this task's top level page-table
                 * with the 'reference' page table.
                 *
                 * Do _not_ use "tsk" here. We might be inside
                 * an interrupt in the middle of a task switch..
                 */
                int index = pgd_index(address);
                pgd_t *pgd, *pgd_k;
                pud_t *pud, *pud_k;
                pmd_t *pmd, *pmd_k;
                pte_t *pte_k;

                pgd_k = init_mm.pgd + index;

                if (!pgd_present(*pgd_k))
                        goto no_context;

                pud_k = pud_offset(pgd_k, address);
                if (!pud_present(*pud_k))
                        goto no_context;

                pmd_k = pmd_offset(pud_k, address);
                if (!pmd_present(*pmd_k))
                        goto no_context;

                pgd = (pgd_t *) PTBR + index;
                pud = pud_offset(pgd, address);
                pmd = pmd_offset(pud, address);
                set_pmd(pmd, *pmd_k);

                pte_k = pte_offset_kernel(pmd_k, address);
                if (!pte_present(*pte_k))
                        goto no_context;
                return;
        }
}