linux/arch/score/mm/fault.c
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   1/*
   2 * arch/score/mm/fault.c
   3 *
   4 * Score Processor version.
   5 *
   6 * Copyright (C) 2009 Sunplus Core Technology Co., Ltd.
   7 *  Lennox Wu <lennox.wu@sunplusct.com>
   8 *  Chen Liqin <liqin.chen@sunplusct.com>
   9 *
  10 * This program is free software; you can redistribute it and/or modify
  11 * it under the terms of the GNU General Public License as published by
  12 * the Free Software Foundation; either version 2 of the License, or
  13 * (at your option) any later version.
  14 *
  15 * This program is distributed in the hope that it will be useful,
  16 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 * GNU General Public License for more details.
  19 *
  20 * You should have received a copy of the GNU General Public License
  21 * along with this program; if not, see the file COPYING, or write
  22 * to the Free Software Foundation, Inc.,
  23 * 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  24 */
  25
  26#include <linux/errno.h>
  27#include <linux/interrupt.h>
  28#include <linux/kernel.h>
  29#include <linux/mm.h>
  30#include <linux/mman.h>
  31#include <linux/module.h>
  32#include <linux/signal.h>
  33#include <linux/sched.h>
  34#include <linux/string.h>
  35#include <linux/types.h>
  36#include <linux/ptrace.h>
  37
  38/*
  39 * This routine handles page faults.  It determines the address,
  40 * and the problem, and then passes it off to one of the appropriate
  41 * routines.
  42 */
  43asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long write,
  44                                unsigned long address)
  45{
  46        struct vm_area_struct *vma = NULL;
  47        struct task_struct *tsk = current;
  48        struct mm_struct *mm = tsk->mm;
  49        const int field = sizeof(unsigned long) * 2;
  50        siginfo_t info;
  51        int fault;
  52
  53        info.si_code = SEGV_MAPERR;
  54
  55        /*
  56        * We fault-in kernel-space virtual memory on-demand. The
  57        * 'reference' page table is init_mm.pgd.
  58        *
  59        * NOTE! We MUST NOT take any locks for this case. We may
  60        * be in an interrupt or a critical region, and should
  61        * only copy the information from the master page table,
  62        * nothing more.
  63        */
  64        if (unlikely(address >= VMALLOC_START && address <= VMALLOC_END))
  65                goto vmalloc_fault;
  66#ifdef MODULE_START
  67        if (unlikely(address >= MODULE_START && address < MODULE_END))
  68                goto vmalloc_fault;
  69#endif
  70
  71        /*
  72        * If we're in an interrupt or have no user
  73        * context, we must not take the fault..
  74        */
  75        if (in_atomic() || !mm)
  76                goto bad_area_nosemaphore;
  77
  78        down_read(&mm->mmap_sem);
  79        vma = find_vma(mm, address);
  80        if (!vma)
  81                goto bad_area;
  82        if (vma->vm_start <= address)
  83                goto good_area;
  84        if (!(vma->vm_flags & VM_GROWSDOWN))
  85                goto bad_area;
  86        if (expand_stack(vma, address))
  87                goto bad_area;
  88        /*
  89        * Ok, we have a good vm_area for this memory access, so
  90        * we can handle it..
  91         */
  92good_area:
  93        info.si_code = SEGV_ACCERR;
  94
  95        if (write) {
  96                if (!(vma->vm_flags & VM_WRITE))
  97                        goto bad_area;
  98        } else {
  99                if (!(vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)))
 100                        goto bad_area;
 101        }
 102
 103survive:
 104        /*
 105        * If for any reason at all we couldn't handle the fault,
 106        * make sure we exit gracefully rather than endlessly redo
 107        * the fault.
 108        */
 109        fault = handle_mm_fault(vma, address, write);
 110        if (unlikely(fault & VM_FAULT_ERROR)) {
 111                if (fault & VM_FAULT_OOM)
 112                        goto out_of_memory;
 113                else if (fault & VM_FAULT_SIGBUS)
 114                        goto do_sigbus;
 115                BUG();
 116        }
 117        if (fault & VM_FAULT_MAJOR)
 118                tsk->maj_flt++;
 119        else
 120                tsk->min_flt++;
 121
 122        up_read(&mm->mmap_sem);
 123        return;
 124
 125        /*
 126        * Something tried to access memory that isn't in our memory map..
 127        * Fix it, but check if it's kernel or user first..
 128         */
 129bad_area:
 130        up_read(&mm->mmap_sem);
 131
 132bad_area_nosemaphore:
 133        /* User mode accesses just cause a SIGSEGV */
 134        if (user_mode(regs)) {
 135                tsk->thread.cp0_badvaddr = address;
 136                tsk->thread.error_code = write;
 137                info.si_signo = SIGSEGV;
 138                info.si_errno = 0;
 139                /* info.si_code has been set above */
 140                info.si_addr = (void __user *) address;
 141                force_sig_info(SIGSEGV, &info, tsk);
 142                return;
 143        }
 144
 145no_context:
 146        /* Are we prepared to handle this kernel fault? */
 147        if (fixup_exception(regs)) {
 148                current->thread.cp0_baduaddr = address;
 149                return;
 150        }
 151
 152        /*
 153        * Oops. The kernel tried to access some bad page. We'll have to
 154        * terminate things with extreme prejudice.
 155        */
 156        bust_spinlocks(1);
 157
 158        printk(KERN_ALERT "CPU %d Unable to handle kernel paging request at "
 159                        "virtual address %0*lx, epc == %0*lx, ra == %0*lx\n",
 160                        0, field, address, field, regs->cp0_epc,
 161                        field, regs->regs[3]);
 162        die("Oops", regs);
 163
 164        /*
 165        * We ran out of memory, or some other thing happened to us that made
 166        * us unable to handle the page fault gracefully.
 167        */
 168out_of_memory:
 169        up_read(&mm->mmap_sem);
 170        if (is_global_init(tsk)) {
 171                yield();
 172                down_read(&mm->mmap_sem);
 173                goto survive;
 174        }
 175        printk("VM: killing process %s\n", tsk->comm);
 176        if (user_mode(regs))
 177                do_group_exit(SIGKILL);
 178        goto no_context;
 179
 180do_sigbus:
 181        up_read(&mm->mmap_sem);
 182        /* Kernel mode? Handle exceptions or die */
 183        if (!user_mode(regs))
 184                goto no_context;
 185        else
 186        /*
 187        * Send a sigbus, regardless of whether we were in kernel
 188        * or user mode.
 189        */
 190        tsk->thread.cp0_badvaddr = address;
 191        info.si_signo = SIGBUS;
 192        info.si_errno = 0;
 193        info.si_code = BUS_ADRERR;
 194        info.si_addr = (void __user *) address;
 195        force_sig_info(SIGBUS, &info, tsk);
 196        return;
 197vmalloc_fault:
 198        {
 199                /*
 200                * Synchronize this task's top level page-table
 201                * with the 'reference' page table.
 202                *
 203                * Do _not_ use "tsk" here. We might be inside
 204                * an interrupt in the middle of a task switch..
 205                */
 206                int offset = __pgd_offset(address);
 207                pgd_t *pgd, *pgd_k;
 208                pud_t *pud, *pud_k;
 209                pmd_t *pmd, *pmd_k;
 210                pte_t *pte_k;
 211
 212                pgd = (pgd_t *) pgd_current + offset;
 213                pgd_k = init_mm.pgd + offset;
 214
 215                if (!pgd_present(*pgd_k))
 216                        goto no_context;
 217                set_pgd(pgd, *pgd_k);
 218
 219                pud = pud_offset(pgd, address);
 220                pud_k = pud_offset(pgd_k, address);
 221                if (!pud_present(*pud_k))
 222                        goto no_context;
 223
 224                pmd = pmd_offset(pud, address);
 225                pmd_k = pmd_offset(pud_k, address);
 226                if (!pmd_present(*pmd_k))
 227                        goto no_context;
 228                set_pmd(pmd, *pmd_k);
 229
 230                pte_k = pte_offset_kernel(pmd_k, address);
 231                if (!pte_present(*pte_k))
 232                        goto no_context;
 233                return;
 234        }
 235}
 236