linux/arch/metag/mm/fault.c
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   1/*
   2 *  Meta page fault handling.
   3 *
   4 *  Copyright (C) 2005-2012 Imagination Technologies Ltd.
   5 */
   6
   7#include <linux/mman.h>
   8#include <linux/mm.h>
   9#include <linux/kernel.h>
  10#include <linux/ptrace.h>
  11#include <linux/interrupt.h>
  12#include <linux/uaccess.h>
  13
  14#include <asm/tlbflush.h>
  15#include <asm/mmu.h>
  16#include <asm/traps.h>
  17
  18/* Clear any pending catch buffer state. */
  19static void clear_cbuf_entry(struct pt_regs *regs, unsigned long addr,
  20                             unsigned int trapno)
  21{
  22        PTBICTXEXTCB0 cbuf = regs->extcb0;
  23
  24        switch (trapno) {
  25                /* Instruction fetch faults leave no catch buffer state. */
  26        case TBIXXF_SIGNUM_IGF:
  27        case TBIXXF_SIGNUM_IPF:
  28                return;
  29        default:
  30                if (cbuf[0].CBAddr == addr) {
  31                        cbuf[0].CBAddr = 0;
  32                        cbuf[0].CBFlags &= ~TXCATCH0_FAULT_BITS;
  33
  34                        /* And, as this is the ONLY catch entry, we
  35                         * need to clear the cbuf bit from the context!
  36                         */
  37                        regs->ctx.SaveMask &= ~(TBICTX_CBUF_BIT |
  38                                                TBICTX_XCBF_BIT);
  39
  40                        return;
  41                }
  42                pr_err("Failed to clear cbuf entry!\n");
  43        }
  44}
  45
  46int show_unhandled_signals = 1;
  47
  48int do_page_fault(struct pt_regs *regs, unsigned long address,
  49                  unsigned int write_access, unsigned int trapno)
  50{
  51        struct task_struct *tsk;
  52        struct mm_struct *mm;
  53        struct vm_area_struct *vma, *prev_vma;
  54        siginfo_t info;
  55        int fault;
  56        unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
  57
  58        tsk = current;
  59
  60        if ((address >= VMALLOC_START) && (address < VMALLOC_END)) {
  61                /*
  62                 * Synchronize this task's top level page-table
  63                 * with the 'reference' page table.
  64                 *
  65                 * Do _not_ use "tsk" here. We might be inside
  66                 * an interrupt in the middle of a task switch..
  67                 */
  68                int offset = pgd_index(address);
  69                pgd_t *pgd, *pgd_k;
  70                pud_t *pud, *pud_k;
  71                pmd_t *pmd, *pmd_k;
  72                pte_t *pte_k;
  73
  74                pgd = ((pgd_t *)mmu_get_base()) + offset;
  75                pgd_k = swapper_pg_dir + offset;
  76
  77                /* This will never happen with the folded page table. */
  78                if (!pgd_present(*pgd)) {
  79                        if (!pgd_present(*pgd_k))
  80                                goto bad_area_nosemaphore;
  81                        set_pgd(pgd, *pgd_k);
  82                        return 0;
  83                }
  84
  85                pud = pud_offset(pgd, address);
  86                pud_k = pud_offset(pgd_k, address);
  87                if (!pud_present(*pud_k))
  88                        goto bad_area_nosemaphore;
  89                set_pud(pud, *pud_k);
  90
  91                pmd = pmd_offset(pud, address);
  92                pmd_k = pmd_offset(pud_k, address);
  93                if (!pmd_present(*pmd_k))
  94                        goto bad_area_nosemaphore;
  95                set_pmd(pmd, *pmd_k);
  96
  97                pte_k = pte_offset_kernel(pmd_k, address);
  98                if (!pte_present(*pte_k))
  99                        goto bad_area_nosemaphore;
 100
 101                /* May only be needed on Chorus2 */
 102                flush_tlb_all();
 103                return 0;
 104        }
 105
 106        mm = tsk->mm;
 107
 108        if (in_atomic() || !mm)
 109                goto no_context;
 110
 111        if (user_mode(regs))
 112                flags |= FAULT_FLAG_USER;
 113retry:
 114        down_read(&mm->mmap_sem);
 115
 116        vma = find_vma_prev(mm, address, &prev_vma);
 117
 118        if (!vma || address < vma->vm_start)
 119                goto check_expansion;
 120
 121good_area:
 122        if (write_access) {
 123                if (!(vma->vm_flags & VM_WRITE))
 124                        goto bad_area;
 125                flags |= FAULT_FLAG_WRITE;
 126        } else {
 127                if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
 128                        goto bad_area;
 129        }
 130
 131        /*
 132         * If for any reason at all we couldn't handle the fault,
 133         * make sure we exit gracefully rather than endlessly redo
 134         * the fault.
 135         */
 136        fault = handle_mm_fault(mm, vma, address, flags);
 137
 138        if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
 139                return 0;
 140
 141        if (unlikely(fault & VM_FAULT_ERROR)) {
 142                if (fault & VM_FAULT_OOM)
 143                        goto out_of_memory;
 144                else if (fault & VM_FAULT_SIGBUS)
 145                        goto do_sigbus;
 146                BUG();
 147        }
 148        if (flags & FAULT_FLAG_ALLOW_RETRY) {
 149                if (fault & VM_FAULT_MAJOR)
 150                        tsk->maj_flt++;
 151                else
 152                        tsk->min_flt++;
 153                if (fault & VM_FAULT_RETRY) {
 154                        flags &= ~FAULT_FLAG_ALLOW_RETRY;
 155                        flags |= FAULT_FLAG_TRIED;
 156
 157                        /*
 158                         * No need to up_read(&mm->mmap_sem) as we would
 159                         * have already released it in __lock_page_or_retry
 160                         * in mm/filemap.c.
 161                         */
 162
 163                        goto retry;
 164                }
 165        }
 166
 167        up_read(&mm->mmap_sem);
 168        return 0;
 169
 170check_expansion:
 171        vma = prev_vma;
 172        if (vma && (expand_stack(vma, address) == 0))
 173                goto good_area;
 174
 175bad_area:
 176        up_read(&mm->mmap_sem);
 177
 178bad_area_nosemaphore:
 179        if (user_mode(regs)) {
 180                info.si_signo = SIGSEGV;
 181                info.si_errno = 0;
 182                info.si_code = SEGV_MAPERR;
 183                info.si_addr = (__force void __user *)address;
 184                info.si_trapno = trapno;
 185
 186                if (show_unhandled_signals && unhandled_signal(tsk, SIGSEGV) &&
 187                    printk_ratelimit()) {
 188                        pr_info("%s%s[%d]: segfault at %lx pc %08x sp %08x write %d trap %#x (%s)",
 189                               task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
 190                               tsk->comm, task_pid_nr(tsk), address,
 191                               regs->ctx.CurrPC, regs->ctx.AX[0].U0,
 192                               write_access, trapno, trap_name(trapno));
 193                        print_vma_addr(" in ", regs->ctx.CurrPC);
 194                        print_vma_addr(" rtp in ", regs->ctx.DX[4].U1);
 195                        printk("\n");
 196                        show_regs(regs);
 197                }
 198                force_sig_info(SIGSEGV, &info, tsk);
 199                return 1;
 200        }
 201        goto no_context;
 202
 203do_sigbus:
 204        up_read(&mm->mmap_sem);
 205
 206        /*
 207         * Send a sigbus, regardless of whether we were in kernel
 208         * or user mode.
 209         */
 210        info.si_signo = SIGBUS;
 211        info.si_errno = 0;
 212        info.si_code = BUS_ADRERR;
 213        info.si_addr = (__force void __user *)address;
 214        info.si_trapno = trapno;
 215        force_sig_info(SIGBUS, &info, tsk);
 216
 217        /* Kernel mode? Handle exceptions or die */
 218        if (!user_mode(regs))
 219                goto no_context;
 220
 221        return 1;
 222
 223        /*
 224         * We ran out of memory, or some other thing happened to us that made
 225         * us unable to handle the page fault gracefully.
 226         */
 227out_of_memory:
 228        up_read(&mm->mmap_sem);
 229        if (user_mode(regs)) {
 230                pagefault_out_of_memory();
 231                return 1;
 232        }
 233
 234no_context:
 235        /* Are we prepared to handle this kernel fault?  */
 236        if (fixup_exception(regs)) {
 237                clear_cbuf_entry(regs, address, trapno);
 238                return 1;
 239        }
 240
 241        die("Oops", regs, (write_access << 15) | trapno, address);
 242        do_exit(SIGKILL);
 243}
 244