fault.c

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/*
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 *
 * Copyright (C) 1995, 1996, 1997, 1998 by Ralf Baechle
 * Copyright 1999 SuSE GmbH (Philipp Rumpf, [email protected])
 * Copyright 1999 Hewlett Packard Co.
 *
 */

#include <linux/mm.h>
#include <linux/ptrace.h>
#include <linux/sched.h>
#include <linux/interrupt.h>
#include <linux/module.h>

#include <asm/uaccess.h>
#include <asm/traps.h>

#define PRINT_USER_FAULTS /* (turn this on if you want user faults to be */
             /*  dumped to the console via printk)          */


/* Various important other fields */
#define bit22set(x)     (x & 0x00000200)
#define bits23_25set(x)     (x & 0x000001c0)
#define isGraphicsFlushRead(x)  ((x & 0xfc003fdf) == 0x04001a80)
                /* extended opcode is 0x6a */

#define BITSSET     0x1c0   /* for identifying LDCW */


DEFINE_PER_CPU(struct exception_data, exception_data);

/*
 * parisc_acctyp(unsigned int inst) --
 *    Given a PA-RISC memory access instruction, determine if the
 *    the instruction would perform a memory read or memory write
 *    operation.
 *
 *    This function assumes that the given instruction is a memory access
 *    instruction (i.e. you should really only call it if you know that
 *    the instruction has generated some sort of a memory access fault).
 *
 * Returns:
 *   VM_READ  if read operation
 *   VM_WRITE if write operation
 *   VM_EXEC  if execute operation
 */
static unsigned long
parisc_acctyp(unsigned long code, unsigned int inst)
{
    if (code == 6 || code == 16)
        return VM_EXEC;

    switch (inst & 0xf0000000) {
    case 0x40000000: /* load */
    case 0x50000000: /* new load */
        return VM_READ;

    case 0x60000000: /* store */
    case 0x70000000: /* new store */
        return VM_WRITE;

    case 0x20000000: /* coproc */
    case 0x30000000: /* coproc2 */
        if (bit22set(inst))
            return VM_WRITE;

    case 0x0: /* indexed/memory management */
        if (bit22set(inst)) {
            /*
             * Check for the 'Graphics Flush Read' instruction.
             * It resembles an FDC instruction, except for bits
             * 20 and 21. Any combination other than zero will
             * utilize the block mover functionality on some
             * older PA-RISC platforms.  The case where a block
             * move is performed from VM to graphics IO space
             * should be treated as a READ.
             *
             * The significance of bits 20,21 in the FDC
             * instruction is:
             *
             *   00  Flush data cache (normal instruction behavior)
             *   01  Graphics flush write  (IO space -> VM)
             *   10  Graphics flush read   (VM -> IO space)
             *   11  Graphics flush read/write (VM <-> IO space)
             */
            if (isGraphicsFlushRead(inst))
                return VM_READ;
            return VM_WRITE;
        } else {
            /*
             * Check for LDCWX and LDCWS (semaphore instructions).
             * If bits 23 through 25 are all 1's it is one of
             * the above two instructions and is a write.
             *
             * Note: With the limited bits we are looking at,
             * this will also catch PROBEW and PROBEWI. However,
             * these should never get in here because they don't
             * generate exceptions of the type:
             *   Data TLB miss fault/data page fault
             *   Data memory protection trap
             */
            if (bits23_25set(inst) == BITSSET)
                return VM_WRITE;
        }
        return VM_READ; /* Default */
    }
    return VM_READ; /* Default */
}

#undef bit22set
#undef bits23_25set
#undef isGraphicsFlushRead
#undef BITSSET


#if 0
/* This is the treewalk to find a vma which is the highest that has
 * a start < addr.  We're using find_vma_prev instead right now, but
 * we might want to use this at some point in the future.  Probably
 * not, but I want it committed to CVS so I don't lose it :-)
 */
            while (tree != vm_avl_empty) {
                if (tree->vm_start > addr) {
                    tree = tree->vm_avl_left;
                } else {
                    prev = tree;
                    if (prev->vm_next == NULL)
                        break;
                    if (prev->vm_next->vm_start > addr)
                        break;
                    tree = tree->vm_avl_right;
                }
            }
#endif

int fixup_exception(struct pt_regs *regs)
{
    const struct exception_table_entry *fix;

    fix = search_exception_tables(regs->iaoq[0]);
    if (fix) {
        struct exception_data *d;
        d = &__get_cpu_var(exception_data);
        d->fault_ip = regs->iaoq[0];
        d->fault_space = regs->isr;
        d->fault_addr = regs->ior;

        regs->iaoq[0] = ((fix->fixup) & ~3);
        /*
         * NOTE: In some cases the faulting instruction
         * may be in the delay slot of a branch. We
         * don't want to take the branch, so we don't
         * increment iaoq[1], instead we set it to be
         * iaoq[0]+4, and clear the B bit in the PSW
         */
        regs->iaoq[1] = regs->iaoq[0] + 4;
        regs->gr[0] &= ~PSW_B; /* IPSW in gr[0] */

        return 1;
    }

    return 0;
}

void do_page_fault(struct pt_regs *regs, unsigned long code,
                  unsigned long address)
{
    struct vm_area_struct *vma, *prev_vma;
    struct task_struct *tsk = current;
    struct mm_struct *mm = tsk->mm;
    unsigned long acc_type;
    int fault;

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

    down_read(&mm->mmap_sem);
    vma = find_vma_prev(mm, address, &prev_vma);
    if (!vma || address < vma->vm_start)
        goto check_expansion;
/*
 * Ok, we have a good vm_area for this memory access. We still need to
 * check the access permissions.
 */

good_area:

    acc_type = parisc_acctyp(code,regs->iir);

    if ((vma->vm_flags & acc_type) != acc_type)
        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.
     */

    fault = handle_mm_fault(mm, vma, address, (acc_type & VM_WRITE) ? FAULT_FLAG_WRITE : 0);
    if (unlikely(fault & VM_FAULT_ERROR)) {
        /*
         * We hit a shared mapping outside of the file, or some
         * other thing happened to us that made us unable to
         * handle the page fault gracefully.
         */
        if (fault & VM_FAULT_OOM)
            goto out_of_memory;
        else if (fault & VM_FAULT_SIGBUS)
            goto bad_area;
        BUG();
    }
    if (fault & VM_FAULT_MAJOR)
        current->maj_flt++;
    else
        current->min_flt++;
    up_read(&mm->mmap_sem);
    return;

check_expansion:
    vma = prev_vma;
    if (vma && (expand_stack(vma, address) == 0))
        goto good_area;

/*
 * Something tried to access memory that isn't in our memory map..
 */
bad_area:
    up_read(&mm->mmap_sem);

    if (user_mode(regs)) {
        struct siginfo si;

#ifdef PRINT_USER_FAULTS
        printk(KERN_DEBUG "\n");
        printk(KERN_DEBUG "do_page_fault() pid=%d command='%s' type=%lu address=0x%08lx\n",
            task_pid_nr(tsk), tsk->comm, code, address);
        if (vma) {
            printk(KERN_DEBUG "vm_start = 0x%08lx, vm_end = 0x%08lx\n",
                    vma->vm_start, vma->vm_end);
        }
        show_regs(regs);
#endif
        /* FIXME: actually we need to get the signo and code correct */
        si.si_signo = SIGSEGV;
        si.si_errno = 0;
        si.si_code = SEGV_MAPERR;
        si.si_addr = (void __user *) address;
        force_sig_info(SIGSEGV, &si, current);
        return;
    }

no_context:

    if (!user_mode(regs) && fixup_exception(regs)) {
        return;
    }

    parisc_terminate("Bad Address (null pointer deref?)", regs, code, address);

  out_of_memory:
    up_read(&mm->mmap_sem);
    if (!user_mode(regs))
        goto no_context;
    pagefault_out_of_memory();
}