Subversion Repositories or1k

/*

 *  linux/arch/or32/mm/fault.c

 *

 *  or32 version

 *    author(s): Matjaz Breskvar (phoenix@opencores.org)

 *

 *  derived from cris, i386, m68k, ppc, sh ports.

 *

 *  changes:

 *  18. 11. 2003: Matjaz Breskvar (phoenix@opencores.org)

 *    initial port to or32 architecture

 *

 *  based on:

 *

 *  PowerPC version

 *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)

 *

 *  Derived from "arch/i386/mm/fault.c"

 *    Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds

 *

 *  Modified by Cort Dougan and Paul Mackerras.

 *

 *  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.

 */

#include <linux/config.h>

#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/interrupt.h>

#include <asm/page.h>

#include <asm/pgtable.h>

#include <asm/mmu.h>

#include <asm/mmu_context.h>

#include <asm/system.h>

#include <asm/uaccess.h>

/* debug of low-level TLB reload */

#undef DEBUG

#ifdef DEBUG

#define D(x) x

#else

#define D(x)

#endif

/* debug of higher-level faults */

#define DPG(x) x

#define NUM_TLB_ENTRIES 64

#define TLB_OFFSET(add) (((add) >> PAGE_SHIFT) & (NUM_TLB_ENTRIES-1))

unsigned long pte_misses;       /* updated by do_page_fault() */

unsigned long pte_errors;       /* updated by do_page_fault() */

/* __PHX__ :: - check the vmalloc_fault in do_page_fault()

 *            - also look into include/asm-or32/mmu_context.h

 */

volatile pgd_t *current_pgd;

extern void die(char *, struct pt_regs *, long);

/*

 * This routine handles page faults.  It determines the address,

 * and the problem, and then passes it off to one of the appropriate

 * routines.

 *

 * If this routine detects a bad access, it returns 1, otherwise it

 * returns 0.

 */

asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long address,

                              unsigned long vector, int write_acc)

{

        struct task_struct *tsk;

        struct mm_struct *mm;

        struct vm_area_struct * vma;

        unsigned long fixup;

        siginfo_t info;

        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.

         *

         * NOTE2: This is done so that, when updating the vmalloc

         * mappings we don't have to walk all processes pgdirs and

         * add the high mappings all at once. Instead we do it as they

         * are used. However vmalloc'ed page entries have the PAGE_GLOBAL

         * bit set so sometimes the TLB can use a lingering entry.

         *

         * This verifies that the fault happens in kernel space

         * and that the fault was not a protection error.

         */

        D(phx_mmu("dpf :: addr %x, vect %x, write %x, regs %x, user %x\n",

               address, vector, write_acc, regs, user_mode(regs)));

        if (address >= VMALLOC_START &&

            (vector != 0x300 && vector != 0x400) &&

            !user_mode(regs))

                goto vmalloc_fault;

        /* we can and should enable interrupts at this point */

        sti();

        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_interrupt() || !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 (user_mode(regs)) {

                /*

                 * accessing the stack below usp is always a bug.

                 * we get page-aligned addresses so we can only check

                 * if we're within a page from usp, but that might be

                 * enough to catch brutal errors at least.

                 */

                if (address + PAGE_SIZE < regs->sp)

                        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;

        /* first do some preliminary protection checks */

        if (write_acc) {

                if (!(vma->vm_flags & VM_WRITE))

                        goto bad_area;

        } else {

                /* not present */

                if (!(vma->vm_flags & (VM_READ | VM_EXEC)))

                        goto bad_area;

        }

        /* are we trying to execute nonexecutable area */

        if ((vector == 0x400) && !(vma->vm_page_prot.pgprot & _PAGE_EXEC))

                goto bad_area;

        /*

         * If for any reason at all we couldn't handle the fault,

         * make sure we exit gracefully rather than endlessly redo

         * the fault.

         */

        switch (handle_mm_fault(mm, vma, address, write_acc)) {

        case 1:

                tsk->min_flt++;

                break;

        case 2:

                tsk->maj_flt++;

                break;

        case 0:

                goto do_sigbus;

        default:

                goto out_of_memory;

        }

        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)) {

                printk("USERSPACE: SIGSEGV (current %p, pid %d)\n",

                       current, current->pid);

                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);

                DPG(show_regs(regs));

                __asm__ __volatile__("l.nop 1");

                return;

        }

//      DPG(show_regs(regs));

 no_context:

        /* Are we prepared to handle this kernel fault?

         *

         * (The kernel has valid exception-points in the source

         *  when it acesses user-memory. When it fails in one

         *  of those points, we find it in a table and do a jump

         *  to some fixup code that loads an appropriate error

         *  code)

         */

        phx_mmu("search exception table");

        if ((fixup = search_exception_table(regs->pc)) != 0) {

                /* Adjust the instruction pointer in the stackframe */

                phx_mmu("kernel: doing fixup at EPC=0x%x to 0x%lx\n", regs->pc, fixup);

                regs->pc = fixup;

                return;

        }

        /*

         * Oops. The kernel tried to access some bad page. We'll have to

         * terminate things with extreme prejudice.

         */

        if ((unsigned long) (address) < PAGE_SIZE)

                printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference");

        else

                printk(KERN_ALERT "Unable to handle kernel access");

        printk(" at virtual address 0x%08lx\n",address);

        die("Oops", regs, write_acc);

        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("VM: killing process %s\n", tsk->comm);

        if (user_mode(regs))

                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 (!user_mode(regs))

                goto no_context;

        return;

vmalloc_fault:

        {

                /*

                 * Synchronize this task's top level page-table

                 * with the 'reference' page table.

                 *

                 * Use current_pgd instead of tsk->active_mm->pgd

                 * since the latter might be unavailable if this

                 * code is executed in a misfortunately run irq

                 * (like inside schedule() between switch_mm and

                 *  switch_to...).

                 */

                phx_warn("do_page_fault(): vmalloc_fault will not work, "

                         "since current_pgd assign a proper value somewhere\n"

                         "anyhow we don't need this at the moment\n");

                int offset = pgd_index(address);

                pgd_t *pgd, *pgd_k;

                pmd_t *pmd, *pmd_k;

                pte_t *pte_k;

                phx_mmu("vmalloc_fault");

                pgd = (pgd_t *)current_pgd + offset;

                pgd_k = init_mm.pgd + offset;

                /* Since we're two-level, we don't need to do both

                 * set_pgd and set_pmd (they do the same thing). If

                 * we go three-level at some point, do the right thing

                 * with pgd_present and set_pgd here.

                 *

                 * Also, since the vmalloc area is global, we don't

                 * need to copy individual PTE's, it is enough to

                 * copy the pgd pointer into the pte page of the

                 * root task. If that is there, we'll find our pte if

                 * it exists.

                 */

                pmd = pmd_offset(pgd, address);

                pmd_k = pmd_offset(pgd_k, address);

                if (!pmd_present(*pmd_k))

                        goto bad_area_nosemaphore;

                set_pmd(pmd, *pmd_k);

                /* Make sure the actual PTE exists as well to

                 * catch kernel vmalloc-area accesses to non-mapped

                 * addresses. If we don't do this, this will just

                 * silently loop forever.

                 */

                pte_k = pte_offset(pmd_k, address);

                if (!pte_present(*pte_k))

                        goto no_context;

                return;

        }

}