arch/arc/mm/fault.c

   1 /* Page Fault Handling for ARC (TLB Miss / ProtV)
   2  *
   3  * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License version 2 as
   7  * published by the Free Software Foundation.
   8  */
   9
  10 #include <linux/signal.h>
  11 #include <linux/interrupt.h>
  12 #include <linux/sched.h>
  13 #include <linux/errno.h>
  14 #include <linux/ptrace.h>
  15 #include <linux/uaccess.h>
  16 #include <linux/kdebug.h>
  17 #include <asm/pgalloc.h>
  18 #include <asm/mmu.h>
  19
  20 static int handle_vmalloc_fault(unsigned long address)
  21 {
  22         /*
  23          * Synchronize this task's top level page-table
  24          * with the 'reference' page table.
  25          */
  26         pgd_t *pgd, *pgd_k;
  27         pud_t *pud, *pud_k;
  28         pmd_t *pmd, *pmd_k;
  29
  30         pgd = pgd_offset_fast(current->active_mm, address);
  31         pgd_k = pgd_offset_k(address);
  32
  33         if (!pgd_present(*pgd_k))
  34                 goto bad_area;
  35
  36         pud = pud_offset(pgd, address);
  37         pud_k = pud_offset(pgd_k, address);
  38         if (!pud_present(*pud_k))
  39                 goto bad_area;
  40
  41         pmd = pmd_offset(pud, address);
  42         pmd_k = pmd_offset(pud_k, address);
  43         if (!pmd_present(*pmd_k))
  44                 goto bad_area;
  45
  46         set_pmd(pmd, *pmd_k);
  47
  48         /* XXX: create the TLB entry here */
  49         return 0;
  50
  51 bad_area:
  52         return 1;
  53 }
  54
  55 void do_page_fault(unsigned long address, struct pt_regs *regs)
  56 {
  57         struct vm_area_struct *vma = NULL;
  58         struct task_struct *tsk = current;
  59         struct mm_struct *mm = tsk->mm;
  60         siginfo_t info;
  61         int fault, ret;
  62         int write = regs->ecr_cause & ECR_C_PROTV_STORE;  /* ST/EX */
  63         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
  64
  65         /*
  66          * We fault-in kernel-space virtual memory on-demand. The
  67          * 'reference' page table is init_mm.pgd.
  68          *
  69          * NOTE! We MUST NOT take any locks for this case. We may
  70          * be in an interrupt or a critical region, and should
  71          * only copy the information from the master page table,
  72          * nothing more.
  73          */
  74         if (address >= VMALLOC_START && address <= VMALLOC_END) {
  75                 ret = handle_vmalloc_fault(address);
  76                 if (unlikely(ret))
  77                         goto bad_area_nosemaphore;
  78                 else
  79                         return;
  80         }
  81
  82         info.si_code = SEGV_MAPERR;
  83
  84         /*
  85          * If we're in an interrupt or have no user
  86          * context, we must not take the fault..
  87          */
  88         if (in_atomic() || !mm)
  89                 goto no_context;
  90
  91         if (user_mode(regs))
  92                 flags |= FAULT_FLAG_USER;
  93 retry:
  94         down_read(&mm->mmap_sem);
  95         vma = find_vma(mm, address);
  96         if (!vma)
  97                 goto bad_area;
  98         if (vma->vm_start <= address)
  99                 goto good_area;
 100         if (!(vma->vm_flags & VM_GROWSDOWN))
 101                 goto bad_area;
 102         if (expand_stack(vma, address))
 103                 goto bad_area;
 104
 105         /*
 106          * Ok, we have a good vm_area for this memory access, so
 107          * we can handle it..
 108          */
 109 good_area:
 110         info.si_code = SEGV_ACCERR;
 111
 112         /* Handle protection violation, execute on heap or stack */
 113
 114         if ((regs->ecr_vec == ECR_V_PROTV) &&
 115             (regs->ecr_cause == ECR_C_PROTV_INST_FETCH))
 116                 goto bad_area;
 117
 118         if (write) {
 119                 if (!(vma->vm_flags & VM_WRITE))
 120                         goto bad_area;
 121                 flags |= FAULT_FLAG_WRITE;
 122         } else {
 123                 if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
 124                         goto bad_area;
 125         }
 126
 127         /*
 128          * If for any reason at all we couldn't handle the fault,
 129          * make sure we exit gracefully rather than endlessly redo
 130          * the fault.
 131          */
 132         fault = handle_mm_fault(mm, vma, address, flags);
 133
 134         /* If Pagefault was interrupted by SIGKILL, exit page fault "early" */
 135         if (unlikely(fatal_signal_pending(current))) {
 136                 if ((fault & VM_FAULT_ERROR) && !(fault & VM_FAULT_RETRY))
 137                         up_read(&mm->mmap_sem);
 138                 if (user_mode(regs))
 139                         return;
 140         }
 141
 142         if (likely(!(fault & VM_FAULT_ERROR))) {
 143                 if (flags & FAULT_FLAG_ALLOW_RETRY) {
 144                         /* To avoid updating stats twice for retry case */
 145                         if (fault & VM_FAULT_MAJOR)
 146                                 tsk->maj_flt++;
 147                         else
 148                                 tsk->min_flt++;
 149
 150                         if (fault & VM_FAULT_RETRY) {
 151                                 flags &= ~FAULT_FLAG_ALLOW_RETRY;
 152                                 flags |= FAULT_FLAG_TRIED;
 153                                 goto retry;
 154                         }
 155                 }
 156
 157                 /* Fault Handled Gracefully */
 158                 up_read(&mm->mmap_sem);
 159                 return;
 160         }
 161
 162         if (fault & VM_FAULT_OOM)
 163                 goto out_of_memory;
 164         else if (fault & VM_FAULT_SIGBUS)
 165                 goto do_sigbus;
 166
 167         /* no man's land */
 168         BUG();
 169
 170         /*
 171          * Something tried to access memory that isn't in our memory map..
 172          * Fix it, but check if it's kernel or user first..
 173          */
 174 bad_area:
 175         up_read(&mm->mmap_sem);
 176
 177 bad_area_nosemaphore:
 178         /* User mode accesses just cause a SIGSEGV */
 179         if (user_mode(regs)) {
 180                 tsk->thread.fault_address = address;
 181                 info.si_signo = SIGSEGV;
 182                 info.si_errno = 0;
 183                 /* info.si_code has been set above */
 184                 info.si_addr = (void __user *)address;
 185                 force_sig_info(SIGSEGV, &info, tsk);
 186                 return;
 187         }
 188
 189 no_context:
 190         /* Are we prepared to handle this kernel fault?
 191          *
 192          * (The kernel has valid exception-points in the source
 193          *  when it acesses user-memory. When it fails in one
 194          *  of those points, we find it in a table and do a jump
 195          *  to some fixup code that loads an appropriate error
 196          *  code)
 197          */
 198         if (fixup_exception(regs))
 199                 return;
 200
 201         die("Oops", regs, address);
 202
 203 out_of_memory:
 204         up_read(&mm->mmap_sem);
 205
 206         if (user_mode(regs)) {
 207                 pagefault_out_of_memory();
 208                 return;
 209         }
 210
 211         goto no_context;
 212
 213 do_sigbus:
 214         up_read(&mm->mmap_sem);
 215
 216         if (!user_mode(regs))
 217                 goto no_context;
 218
 219         tsk->thread.fault_address = address;
 220         info.si_signo = SIGBUS;
 221         info.si_errno = 0;
 222         info.si_code = BUS_ADRERR;
 223         info.si_addr = (void __user *)address;
 224         force_sig_info(SIGBUS, &info, tsk);
 225 }