fault.c

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/* 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 ([email protected])
 *
 * 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 <asm/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 write, fault;

#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 (in_atomic() || !mm)
        goto no_context;

    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;
    write = 0;
    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;
        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, write ? FAULT_FLAG_WRITE : 0);
    if (unlikely(fault & VM_FAULT_ERROR)) {
        if (fault & VM_FAULT_OOM)
            goto out_of_memory;
        else if (fault & VM_FAULT_SIGBUS)
            goto do_sigbus;
        BUG();
    }
    if (fault & VM_FAULT_MAJOR)
        current->maj_flt++;
    else
        current->min_flt++;

    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);
    printk(KERN_ALERT "VM: killing process %s\n", tsk->comm);
    if ((fault_code & MMUFCR_xFC_ACCESS) == MMUFCR_xFC_ACCESS_USR)
        do_exit(SIGKILL);
    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;
    }
}