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
  19 static int handle_vmalloc_fault(struct mm_struct *mm, unsigned long address)
  20 {
  21         /*
  22          * Synchronize this task's top level page-table
  23          * with the 'reference' page table.
  24          */
  25         pgd_t *pgd, *pgd_k;
  26         pud_t *pud, *pud_k;
  27         pmd_t *pmd, *pmd_k;
  28
  29         pgd = pgd_offset_fast(mm, address);
  30         pgd_k = pgd_offset_k(address);
  31
  32         if (!pgd_present(*pgd_k))
  33                 goto bad_area;
  34
  35         pud = pud_offset(pgd, address);
  36         pud_k = pud_offset(pgd_k, address);
  37         if (!pud_present(*pud_k))
  38                 goto bad_area;
  39
  40         pmd = pmd_offset(pud, address);
  41         pmd_k = pmd_offset(pud_k, address);
  42         if (!pmd_present(*pmd_k))
  43                 goto bad_area;
  44
  45         set_pmd(pmd, *pmd_k);
  46
  47         /* XXX: create the TLB entry here */
  48         return 0;
  49
  50 bad_area:
  51         return 1;
  52 }
  53
  54 void do_page_fault(struct pt_regs *regs, int write, unsigned long address,
  55                    unsigned long cause_code)
  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         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE |
  63                                 (write ? FAULT_FLAG_WRITE : 0);
  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(mm, 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 retry:
  92         down_read(&mm->mmap_sem);
  93         vma = find_vma(mm, address);
  94         if (!vma)
  95                 goto bad_area;
  96         if (vma->vm_start <= address)
  97                 goto good_area;
  98         if (!(vma->vm_flags & VM_GROWSDOWN))
  99                 goto bad_area;
 100         if (expand_stack(vma, address))
 101                 goto bad_area;
 102
 103         /*
 104          * Ok, we have a good vm_area for this memory access, so
 105          * we can handle it..
 106          */
 107 good_area:
 108         info.si_code = SEGV_ACCERR;
 109
 110         /* Handle protection violation, execute on heap or stack */
 111
 112         if (cause_code == ((ECR_V_PROTV << 16) | ECR_C_PROTV_INST_FETCH))
 113                 goto bad_area;
 114
 115         if (write) {
 116                 if (!(vma->vm_flags & VM_WRITE))
 117                         goto bad_area;
 118         } else {
 119                 if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
 120                         goto bad_area;
 121         }
 122
 123 survive:
 124         /*
 125          * If for any reason at all we couldn't handle the fault,
 126          * make sure we exit gracefully rather than endlessly redo
 127          * the fault.
 128          */
 129         fault = handle_mm_fault(mm, vma, address, flags);
 130
 131         /* If Pagefault was interrupted by SIGKILL, exit page fault "early" */
 132         if (unlikely(fatal_signal_pending(current))) {
 133                 if ((fault & VM_FAULT_ERROR) && !(fault & VM_FAULT_RETRY))
 134                         up_read(&mm->mmap_sem);
 135                 if (user_mode(regs))
 136                         return;
 137         }
 138
 139         if (likely(!(fault & VM_FAULT_ERROR))) {
 140                 if (flags & FAULT_FLAG_ALLOW_RETRY) {
 141                         /* To avoid updating stats twice for retry case */
 142                         if (fault & VM_FAULT_MAJOR)
 143                                 tsk->maj_flt++;
 144                         else
 145                                 tsk->min_flt++;
 146
 147                         if (fault & VM_FAULT_RETRY) {
 148                                 flags &= ~FAULT_FLAG_ALLOW_RETRY;
 149                                 flags |= FAULT_FLAG_TRIED;
 150                                 goto retry;
 151                         }
 152                 }
 153
 154                 /* Fault Handled Gracefully */
 155                 up_read(&mm->mmap_sem);
 156                 return;
 157         }
 158
 159         /* TBD: switch to pagefault_out_of_memory() */
 160         if (fault & VM_FAULT_OOM)
 161                 goto out_of_memory;
 162         else if (fault & VM_FAULT_SIGBUS)
 163                 goto do_sigbus;
 164
 165         /* no man's land */
 166         BUG();
 167
 168         /*
 169          * Something tried to access memory that isn't in our memory map..
 170          * Fix it, but check if it's kernel or user first..
 171          */
 172 bad_area:
 173         up_read(&mm->mmap_sem);
 174
 175 bad_area_nosemaphore:
 176         /* User mode accesses just cause a SIGSEGV */
 177         if (user_mode(regs)) {
 178                 tsk->thread.fault_address = address;
 179                 tsk->thread.cause_code = cause_code;
 180                 info.si_signo = SIGSEGV;
 181                 info.si_errno = 0;
 182                 /* info.si_code has been set above */
 183                 info.si_addr = (void __user *)address;
 184                 force_sig_info(SIGSEGV, &info, tsk);
 185                 return;
 186         }
 187
 188 no_context:
 189         /* Are we prepared to handle this kernel fault?
 190          *
 191          * (The kernel has valid exception-points in the source
 192          *  when it acesses user-memory. When it fails in one
 193          *  of those points, we find it in a table and do a jump
 194          *  to some fixup code that loads an appropriate error
 195          *  code)
 196          */
 197         if (fixup_exception(regs))
 198                 return;
 199
 200         die("Oops", regs, address, cause_code);
 201
 202 out_of_memory:
 203         if (is_global_init(tsk)) {
 204                 yield();
 205                 goto survive;
 206         }
 207         up_read(&mm->mmap_sem);
 208
 209         if (user_mode(regs))
 210                 do_group_exit(SIGKILL); /* This will never return */
 211
 212         goto no_context;
 213
 214 do_sigbus:
 215         up_read(&mm->mmap_sem);
 216
 217         if (!user_mode(regs))
 218                 goto no_context;
 219
 220         tsk->thread.fault_address = address;
 221         tsk->thread.cause_code = cause_code;
 222         info.si_signo = SIGBUS;
 223         info.si_errno = 0;
 224         info.si_code = BUS_ADRERR;
 225         info.si_addr = (void __user *)address;
 226         force_sig_info(SIGBUS, &info, tsk);
 227 }