vm_fault.c

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/*
 * Memory fault handling for Hexagon
 *
 * Copyright (c) 2010-2011, The Linux Foundation. All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 and
 * only version 2 as published by the Free Software Foundation.
 *
 * 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, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 */

/*
 * Page fault handling for the Hexagon Virtual Machine.
 * Can also be called by a native port emulating the HVM
 * execptions.
 */

#include <asm/pgtable.h>
#include <asm/traps.h>
#include <asm/uaccess.h>
#include <linux/mm.h>
#include <linux/signal.h>
#include <linux/module.h>
#include <linux/hardirq.h>

/*
 * Decode of hardware exception sends us to one of several
 * entry points.  At each, we generate canonical arguments
 * for handling by the abstract memory management code.
 */
#define FLT_IFETCH     -1
#define FLT_LOAD        0
#define FLT_STORE       1


/*
 * Canonical page fault handler
 */
void do_page_fault(unsigned long address, long cause, struct pt_regs *regs)
{
    struct vm_area_struct *vma;
    struct mm_struct *mm = current->mm;
    siginfo_t info;
    int si_code = SEGV_MAPERR;
    int fault;
    const struct exception_table_entry *fixup;
    unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE |
                 (cause > 0 ? FAULT_FLAG_WRITE : 0);

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

    local_irq_enable();

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 (expand_stack(vma, address))
        goto bad_area;

good_area:
    /* Address space is OK.  Now check access rights. */
    si_code = SEGV_ACCERR;

    switch (cause) {
    case FLT_IFETCH:
        if (!(vma->vm_flags & VM_EXEC))
            goto bad_area;
        break;
    case FLT_LOAD:
        if (!(vma->vm_flags & VM_READ))
            goto bad_area;
        break;
    case FLT_STORE:
        if (!(vma->vm_flags & VM_WRITE))
            goto bad_area;
        break;
    }

    fault = handle_mm_fault(mm, vma, address, flags);

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

    /* The most common case -- we are done. */
    if (likely(!(fault & VM_FAULT_ERROR))) {
        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;
                flags |= FAULT_FLAG_TRIED;
                goto retry;
            }
        }

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

    up_read(&mm->mmap_sem);

    /* Handle copyin/out exception cases */
    if (!user_mode(regs))
        goto no_context;

    if (fault & VM_FAULT_OOM) {
        pagefault_out_of_memory();
        return;
    }

    /* User-mode address is in the memory map, but we are
     * unable to fix up the page fault.
     */
    if (fault & VM_FAULT_SIGBUS) {
        info.si_signo = SIGBUS;
        info.si_code = BUS_ADRERR;
    }
    /* Address is not in the memory map */
    else {
        info.si_signo = SIGSEGV;
        info.si_code = SEGV_ACCERR;
    }
    info.si_errno = 0;
    info.si_addr = (void __user *)address;
    force_sig_info(info.si_code, &info, current);
    return;

bad_area:
    up_read(&mm->mmap_sem);

    if (user_mode(regs)) {
        info.si_signo = SIGSEGV;
        info.si_errno = 0;
        info.si_code = si_code;
        info.si_addr = (void *)address;
        force_sig_info(SIGSEGV, &info, current);
        return;
    }
    /* Kernel-mode fault falls through */

no_context:
    fixup = search_exception_tables(pt_elr(regs));
    if (fixup) {
        pt_set_elr(regs, fixup->fixup);
        return;
    }

    /* Things are looking very, very bad now */
    bust_spinlocks(1);
    printk(KERN_EMERG "Unable to handle kernel paging request at "
        "virtual address 0x%08lx, regs %p\n", address, regs);
    die("Bad Kernel VA", regs, SIGKILL);
}


void read_protection_fault(struct pt_regs *regs)
{
    unsigned long badvadr = pt_badva(regs);

    do_page_fault(badvadr, FLT_LOAD, regs);
}

void write_protection_fault(struct pt_regs *regs)
{
    unsigned long badvadr = pt_badva(regs);

    do_page_fault(badvadr, FLT_STORE, regs);
}

void execute_protection_fault(struct pt_regs *regs)
{
    unsigned long badvadr = pt_badva(regs);

    do_page_fault(badvadr, FLT_IFETCH, regs);
}