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
  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 (faulthandler_disabled() || !mm)
 109                 goto no_context;
 110
 111         if (user_mode(regs))
 112                 flags |= FAULT_FLAG_USER;
 113 retry:
 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
 121 good_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(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_SIGSEGV)
 145                         goto bad_area;
 146                 else if (fault & VM_FAULT_SIGBUS)
 147                         goto do_sigbus;
 148                 BUG();
 149         }
 150         if (flags & FAULT_FLAG_ALLOW_RETRY) {
 151                 if (fault & VM_FAULT_MAJOR)
 152                         tsk->maj_flt++;
 153                 else
 154                         tsk->min_flt++;
 155                 if (fault & VM_FAULT_RETRY) {
 156                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
 157                         flags |= FAULT_FLAG_TRIED;
 158
 159                         /*
 160                          * No need to up_read(&mm->mmap_sem) as we would
 161                          * have already released it in __lock_page_or_retry
 162                          * in mm/filemap.c.
 163                          */
 164
 165                         goto retry;
 166                 }
 167         }
 168
 169         up_read(&mm->mmap_sem);
 170         return 0;
 171
 172 check_expansion:
 173         vma = prev_vma;
 174         if (vma && (expand_stack(vma, address) == 0))
 175                 goto good_area;
 176
 177 bad_area:
 178         up_read(&mm->mmap_sem);
 179
 180 bad_area_nosemaphore:
 181         if (user_mode(regs)) {
 182                 info.si_signo = SIGSEGV;
 183                 info.si_errno = 0;
 184                 info.si_code = SEGV_MAPERR;
 185                 info.si_addr = (__force void __user *)address;
 186                 info.si_trapno = trapno;
 187
 188                 if (show_unhandled_signals && unhandled_signal(tsk, SIGSEGV) &&
 189                     printk_ratelimit()) {
 190                         pr_info("%s%s[%d]: segfault at %lx pc %08x sp %08x write %d trap %#x (%s)",
 191                                task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
 192                                tsk->comm, task_pid_nr(tsk), address,
 193                                regs->ctx.CurrPC, regs->ctx.AX[0].U0,
 194                                write_access, trapno, trap_name(trapno));
 195                         print_vma_addr(" in ", regs->ctx.CurrPC);
 196                         print_vma_addr(" rtp in ", regs->ctx.DX[4].U1);
 197                         printk("\n");
 198                         show_regs(regs);
 199                 }
 200                 force_sig_info(SIGSEGV, &info, tsk);
 201                 return 1;
 202         }
 203         goto no_context;
 204
 205 do_sigbus:
 206         up_read(&mm->mmap_sem);
 207
 208         /*
 209          * Send a sigbus, regardless of whether we were in kernel
 210          * or user mode.
 211          */
 212         info.si_signo = SIGBUS;
 213         info.si_errno = 0;
 214         info.si_code = BUS_ADRERR;
 215         info.si_addr = (__force void __user *)address;
 216         info.si_trapno = trapno;
 217         force_sig_info(SIGBUS, &info, tsk);
 218
 219         /* Kernel mode? Handle exceptions or die */
 220         if (!user_mode(regs))
 221                 goto no_context;
 222
 223         return 1;
 224
 225         /*
 226          * We ran out of memory, or some other thing happened to us that made
 227          * us unable to handle the page fault gracefully.
 228          */
 229 out_of_memory:
 230         up_read(&mm->mmap_sem);
 231         if (user_mode(regs)) {
 232                 pagefault_out_of_memory();
 233                 return 1;
 234         }
 235
 236 no_context:
 237         /* Are we prepared to handle this kernel fault?  */
 238         if (fixup_exception(regs)) {
 239                 clear_cbuf_entry(regs, address, trapno);
 240                 return 1;
 241         }
 242
 243         die("Oops", regs, (write_access << 15) | trapno, address);
 244         do_exit(SIGKILL);
 245 }