arch/metag/mm/fault.c

   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. */
  19 static 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
  46 int show_unhandled_signals = 1;
  47
  48 int 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                                 (write_access ? FAULT_FLAG_WRITE : 0);
  58
  59         tsk = current;
  60
  61         if ((address >= VMALLOC_START) && (address < VMALLOC_END)) {
  62                 /*
  63                  * Synchronize this task's top level page-table
  64                  * with the 'reference' page table.
  65                  *
  66                  * Do _not_ use "tsk" here. We might be inside
  67                  * an interrupt in the middle of a task switch..
  68                  */
  69                 int offset = pgd_index(address);
  70                 pgd_t *pgd, *pgd_k;
  71                 pud_t *pud, *pud_k;
  72                 pmd_t *pmd, *pmd_k;
  73                 pte_t *pte_k;
  74
  75                 pgd = ((pgd_t *)mmu_get_base()) + offset;
  76                 pgd_k = swapper_pg_dir + offset;
  77
  78                 /* This will never happen with the folded page table. */
  79                 if (!pgd_present(*pgd)) {
  80                         if (!pgd_present(*pgd_k))
  81                                 goto bad_area_nosemaphore;
  82                         set_pgd(pgd, *pgd_k);
  83                         return 0;
  84                 }
  85
  86                 pud = pud_offset(pgd, address);
  87                 pud_k = pud_offset(pgd_k, address);
  88                 if (!pud_present(*pud_k))
  89                         goto bad_area_nosemaphore;
  90                 set_pud(pud, *pud_k);
  91
  92                 pmd = pmd_offset(pud, address);
  93                 pmd_k = pmd_offset(pud_k, address);
  94                 if (!pmd_present(*pmd_k))
  95                         goto bad_area_nosemaphore;
  96                 set_pmd(pmd, *pmd_k);
  97
  98                 pte_k = pte_offset_kernel(pmd_k, address);
  99                 if (!pte_present(*pte_k))
 100                         goto bad_area_nosemaphore;
 101
 102                 /* May only be needed on Chorus2 */
 103                 flush_tlb_all();
 104                 return 0;
 105         }
 106
 107         mm = tsk->mm;
 108
 109         if (in_atomic() || !mm)
 110                 goto no_context;
 111
 112 retry:
 113         down_read(&mm->mmap_sem);
 114
 115         vma = find_vma_prev(mm, address, &prev_vma);
 116
 117         if (!vma || address < vma->vm_start)
 118                 goto check_expansion;
 119
 120 good_area:
 121         if (write_access) {
 122                 if (!(vma->vm_flags & VM_WRITE))
 123                         goto bad_area;
 124         } else {
 125                 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
 126                         goto bad_area;
 127         }
 128
 129         /*
 130          * If for any reason at all we couldn't handle the fault,
 131          * make sure we exit gracefully rather than endlessly redo
 132          * the fault.
 133          */
 134         fault = handle_mm_fault(mm, vma, address, flags);
 135
 136         if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
 137                 return 0;
 138
 139         if (unlikely(fault & VM_FAULT_ERROR)) {
 140                 if (fault & VM_FAULT_OOM)
 141                         goto out_of_memory;
 142                 else if (fault & VM_FAULT_SIGBUS)
 143                         goto do_sigbus;
 144                 BUG();
 145         }
 146         if (flags & FAULT_FLAG_ALLOW_RETRY) {
 147                 if (fault & VM_FAULT_MAJOR)
 148                         tsk->maj_flt++;
 149                 else
 150                         tsk->min_flt++;
 151                 if (fault & VM_FAULT_RETRY) {
 152                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
 153                         flags |= FAULT_FLAG_TRIED;
 154
 155                         /*
 156                          * No need to up_read(&mm->mmap_sem) as we would
 157                          * have already released it in __lock_page_or_retry
 158                          * in mm/filemap.c.
 159                          */
 160
 161                         goto retry;
 162                 }
 163         }
 164
 165         up_read(&mm->mmap_sem);
 166         return 0;
 167
 168 check_expansion:
 169         vma = prev_vma;
 170         if (vma && (expand_stack(vma, address) == 0))
 171                 goto good_area;
 172
 173 bad_area:
 174         up_read(&mm->mmap_sem);
 175
 176 bad_area_nosemaphore:
 177         if (user_mode(regs)) {
 178                 info.si_signo = SIGSEGV;
 179                 info.si_errno = 0;
 180                 info.si_code = SEGV_MAPERR;
 181                 info.si_addr = (__force void __user *)address;
 182                 info.si_trapno = trapno;
 183
 184                 if (show_unhandled_signals && unhandled_signal(tsk, SIGSEGV) &&
 185                     printk_ratelimit()) {
 186                         pr_info("%s%s[%d]: segfault at %lx pc %08x sp %08x write %d trap %#x (%s)",
 187                                task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
 188                                tsk->comm, task_pid_nr(tsk), address,
 189                                regs->ctx.CurrPC, regs->ctx.AX[0].U0,
 190                                write_access, trapno, trap_name(trapno));
 191                         print_vma_addr(" in ", regs->ctx.CurrPC);
 192                         print_vma_addr(" rtp in ", regs->ctx.DX[4].U1);
 193                         printk("\n");
 194                         show_regs(regs);
 195                 }
 196                 force_sig_info(SIGSEGV, &info, tsk);
 197                 return 1;
 198         }
 199         goto no_context;
 200
 201 do_sigbus:
 202         up_read(&mm->mmap_sem);
 203
 204         /*
 205          * Send a sigbus, regardless of whether we were in kernel
 206          * or user mode.
 207          */
 208         info.si_signo = SIGBUS;
 209         info.si_errno = 0;
 210         info.si_code = BUS_ADRERR;
 211         info.si_addr = (__force void __user *)address;
 212         info.si_trapno = trapno;
 213         force_sig_info(SIGBUS, &info, tsk);
 214
 215         /* Kernel mode? Handle exceptions or die */
 216         if (!user_mode(regs))
 217                 goto no_context;
 218
 219         return 1;
 220
 221         /*
 222          * We ran out of memory, or some other thing happened to us that made
 223          * us unable to handle the page fault gracefully.
 224          */
 225 out_of_memory:
 226         up_read(&mm->mmap_sem);
 227         if (user_mode(regs))
 228                 do_group_exit(SIGKILL);
 229
 230 no_context:
 231         /* Are we prepared to handle this kernel fault?  */
 232         if (fixup_exception(regs)) {
 233                 clear_cbuf_entry(regs, address, trapno);
 234                 return 1;
 235         }
 236
 237         die("Oops", regs, (write_access << 15) | trapno, address);
 238         do_exit(SIGKILL);
 239 }