fault.c

Go to the documentation of this file.

/*
 * arch/score/mm/fault.c
 *
 * Score Processor version.
 *
 * Copyright (C) 2009 Sunplus Core Technology Co., Ltd.
 *  Lennox Wu <[email protected]>
 *  Chen Liqin <[email protected]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, see the file COPYING, or write
 * to the Free Software Foundation, Inc.,
 * 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */

#include <linux/errno.h>
#include <linux/interrupt.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/mman.h>
#include <linux/module.h>
#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/ptrace.h>

/*
 * This routine handles page faults.  It determines the address,
 * and the problem, and then passes it off to one of the appropriate
 * routines.
 */
asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long write,
                unsigned long address)
{
    struct vm_area_struct *vma = NULL;
    struct task_struct *tsk = current;
    struct mm_struct *mm = tsk->mm;
    const int field = sizeof(unsigned long) * 2;
    siginfo_t info;
    int fault;

    info.si_code = SEGV_MAPERR;

    /*
    * 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.
    */
    if (unlikely(address >= VMALLOC_START && address <= VMALLOC_END))
        goto vmalloc_fault;
#ifdef MODULE_START
    if (unlikely(address >= MODULE_START && address < MODULE_END))
        goto vmalloc_fault;
#endif

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

    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 (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;

    if (write) {
        if (!(vma->vm_flags & VM_WRITE))
            goto bad_area;
    } else {
        if (!(vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)))
            goto bad_area;
    }

survive:
    /*
    * 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);
    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)
        tsk->maj_flt++;
    else
        tsk->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);

bad_area_nosemaphore:
    /* User mode accesses just cause a SIGSEGV */
    if (user_mode(regs)) {
        tsk->thread.cp0_badvaddr = address;
        tsk->thread.error_code = write;
        info.si_signo = SIGSEGV;
        info.si_errno = 0;
        /* info.si_code has been set above */
        info.si_addr = (void __user *) address;
        force_sig_info(SIGSEGV, &info, tsk);
        return;
    }

no_context:
    /* Are we prepared to handle this kernel fault? */
    if (fixup_exception(regs)) {
        current->thread.cp0_baduaddr = address;
        return;
    }

    /*
    * Oops. The kernel tried to access some bad page. We'll have to
    * terminate things with extreme prejudice.
    */
    bust_spinlocks(1);

    printk(KERN_ALERT "CPU %d Unable to handle kernel paging request at "
            "virtual address %0*lx, epc == %0*lx, ra == %0*lx\n",
            0, field, address, field, regs->cp0_epc,
            field, regs->regs[3]);
    die("Oops", regs);

    /*
    * 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(tsk)) {
        yield();
        down_read(&mm->mmap_sem);
        goto survive;
    }
    printk("VM: killing process %s\n", tsk->comm);
    if (user_mode(regs))
        do_group_exit(SIGKILL);
    goto no_context;

do_sigbus:
    up_read(&mm->mmap_sem);
    /* Kernel mode? Handle exceptions or die */
    if (!user_mode(regs))
        goto no_context;
    else
    /*
    * Send a sigbus, regardless of whether we were in kernel
    * or user mode.
    */
    tsk->thread.cp0_badvaddr = address;
    info.si_signo = SIGBUS;
    info.si_errno = 0;
    info.si_code = BUS_ADRERR;
    info.si_addr = (void __user *) address;
    force_sig_info(SIGBUS, &info, tsk);
    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 offset = __pgd_offset(address);
        pgd_t *pgd, *pgd_k;
        pud_t *pud, *pud_k;
        pmd_t *pmd, *pmd_k;
        pte_t *pte_k;

        pgd = (pgd_t *) pgd_current + offset;
        pgd_k = init_mm.pgd + offset;

        if (!pgd_present(*pgd_k))
            goto no_context;
        set_pgd(pgd, *pgd_k);

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

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

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