fault.c

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/*
 *  linux/arch/frv/mm/fault.c
 *
 * Copyright (C) 2003 Red Hat, Inc. All Rights Reserved.
 * - Written by David Howells ([email protected])
 * - Derived from arch/m68knommu/mm/fault.c
 *   - Copyright (C) 1998  D. Jeff Dionne <[email protected]>,
 *   - Copyright (C) 2000  Lineo, Inc.  (www.lineo.com)
 *
 *  Based on:
 *
 *  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/hardirq.h>

#include <asm/pgtable.h>
#include <asm/uaccess.h>
#include <asm/gdb-stub.h>

/*****************************************************************************/
/*
 * This routine handles page faults.  It determines the problem, and
 * then passes it off to one of the appropriate routines.
 */
asmlinkage void do_page_fault(int datammu, unsigned long esr0, unsigned long ear0)
{
    struct vm_area_struct *vma;
    struct mm_struct *mm;
    unsigned long _pme, lrai, lrad, fixup;
    siginfo_t info;
    pgd_t *pge;
    pud_t *pue;
    pte_t *pte;
    int write;
    int fault;

#if 0
    const char *atxc[16] = {
        [0x0] = "mmu-miss", [0x8] = "multi-dat", [0x9] = "multi-sat",
        [0xa] = "tlb-miss", [0xc] = "privilege", [0xd] = "write-prot",
    };

    printk("do_page_fault(%d,%lx [%s],%lx)\n",
           datammu, esr0, atxc[esr0 >> 20 & 0xf], ear0);
#endif

    mm = current->mm;

    /*
     * 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 (!user_mode(__frame) && (esr0 & ESR0_ATXC) == ESR0_ATXC_AMRTLB_MISS) {
        if (ear0 >= VMALLOC_START && ear0 < VMALLOC_END)
            goto kernel_pte_fault;
        if (ear0 >= PKMAP_BASE && ear0 < PKMAP_END)
            goto kernel_pte_fault;
    }

    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, ear0);
    if (!vma)
        goto bad_area;
    if (vma->vm_start <= ear0)
        goto good_area;
    if (!(vma->vm_flags & VM_GROWSDOWN))
        goto bad_area;

    if (user_mode(__frame)) {
        /*
         * accessing the stack below %esp is always a bug.
         * The "+ 32" is there due to some instructions (like
         * pusha) doing post-decrement on the stack and that
         * doesn't show up until later..
         */
        if ((ear0 & PAGE_MASK) + 2 * PAGE_SIZE < __frame->sp) {
#if 0
            printk("[%d] ### Access below stack @%lx (sp=%lx)\n",
                   current->pid, ear0, __frame->sp);
            show_registers(__frame);
            printk("[%d] ### Code: [%08lx] %02x %02x %02x %02x %02x %02x %02x %02x\n",
                   current->pid,
                   __frame->pc,
                   ((u8*)__frame->pc)[0],
                   ((u8*)__frame->pc)[1],
                   ((u8*)__frame->pc)[2],
                   ((u8*)__frame->pc)[3],
                   ((u8*)__frame->pc)[4],
                   ((u8*)__frame->pc)[5],
                   ((u8*)__frame->pc)[6],
                   ((u8*)__frame->pc)[7]
                   );
#endif
            goto bad_area;
        }
    }

    if (expand_stack(vma, ear0))
        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 (esr0 & ESR0_ATXC) {
    default:
        /* handle write to write protected page */
    case ESR0_ATXC_WP_EXCEP:
#ifdef TEST_VERIFY_AREA
        if (!(user_mode(__frame)))
            printk("WP fault at %08lx\n", __frame->pc);
#endif
        if (!(vma->vm_flags & VM_WRITE))
            goto bad_area;
        write = 1;
        break;

         /* handle read from protected page */
    case ESR0_ATXC_PRIV_EXCEP:
        goto bad_area;

         /* handle read, write or exec on absent page
          * - can't support write without permitting read
          * - don't support execute without permitting read and vice-versa
          */
    case ESR0_ATXC_AMRTLB_MISS:
        if (!(vma->vm_flags & (VM_READ | VM_WRITE | 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, ear0, 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 (user_mode(__frame)) {
        info.si_signo = SIGSEGV;
        info.si_errno = 0;
        /* info.si_code has been set above */
        info.si_addr = (void *) ear0;
        force_sig_info(SIGSEGV, &info, current);
        return;
    }

 no_context:
    /* are we prepared to handle this kernel fault? */
    if ((fixup = search_exception_table(__frame->pc)) != 0) {
        __frame->pc = fixup;
        return;
    }

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

    bust_spinlocks(1);

    if (ear0 < 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 addr %08lx\n", ear0);
    printk("  PC  : %08lx\n", __frame->pc);
    printk("  EXC : esr0=%08lx ear0=%08lx\n", esr0, ear0);

    asm("lrai %1,%0,#1,#0,#0" : "=&r"(lrai) : "r"(ear0));
    asm("lrad %1,%0,#1,#0,#0" : "=&r"(lrad) : "r"(ear0));

    printk(KERN_ALERT "  LRAI: %08lx\n", lrai);
    printk(KERN_ALERT "  LRAD: %08lx\n", lrad);

    __break_hijack_kernel_event();

    pge = pgd_offset(current->mm, ear0);
    pue = pud_offset(pge, ear0);
    _pme = pue->pue[0].ste[0];

    printk(KERN_ALERT "  PGE : %8p { PME %08lx }\n", pge, _pme);

    if (_pme & xAMPRx_V) {
        unsigned long dampr, damlr, val;

        asm volatile("movsg dampr2,%0 ! movgs %2,dampr2 ! movsg damlr2,%1"
                 : "=&r"(dampr), "=r"(damlr)
                 : "r" (_pme | xAMPRx_L|xAMPRx_SS_16Kb|xAMPRx_S|xAMPRx_C|xAMPRx_V)
                 );

        pte = (pte_t *) damlr + __pte_index(ear0);
        val = pte_val(*pte);

        asm volatile("movgs %0,dampr2" :: "r" (dampr));

        printk(KERN_ALERT "  PTE : %8p { %08lx }\n", pte, val);
    }

    die_if_kernel("Oops\n");
    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 (!user_mode(__frame))
        goto no_context;
    pagefault_out_of_memory();
    return;

 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 *) ear0;
    force_sig_info(SIGBUS, &info, current);

    /* Kernel mode? Handle exceptions or die */
    if (!user_mode(__frame))
        goto no_context;
    return;

/*
 * The fault was caused by a kernel PTE (such as installed by vmalloc or kmap)
 */
 kernel_pte_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(ear0);
        pgd_t *pgd, *pgd_k;
        pud_t *pud, *pud_k;
        pmd_t *pmd, *pmd_k;
        pte_t *pte_k;

        pgd = (pgd_t *) __get_TTBR();
        pgd = (pgd_t *)__va(pgd) + index;
        pgd_k = ((pgd_t *)(init_mm.pgd)) + index;

        if (!pgd_present(*pgd_k))
            goto no_context;
        //set_pgd(pgd, *pgd_k); /////// gcc ICE's on this line

        pud_k = pud_offset(pgd_k, ear0);
        if (!pud_present(*pud_k))
            goto no_context;

        pmd_k = pmd_offset(pud_k, ear0);
        if (!pmd_present(*pmd_k))
            goto no_context;

        pud = pud_offset(pgd, ear0);
        pmd = pmd_offset(pud, ear0);
        set_pmd(pmd, *pmd_k);

        pte_k = pte_offset_kernel(pmd_k, ear0);
        if (!pte_present(*pte_k))
            goto no_context;
        return;
    }
} /* end do_page_fault() */