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(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(current->active_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
  64         /*
  65          * We fault-in kernel-space virtual memory on-demand. The
  66          * 'reference' page table is init_mm.pgd.
  67          *
  68          * NOTE! We MUST NOT take any locks for this case. We may
  69          * be in an interrupt or a critical region, and should
  70          * only copy the information from the master page table,
  71          * nothing more.
  72          */
  73         if (address >= VMALLOC_START && address <= VMALLOC_END) {
  74                 ret = handle_vmalloc_fault(address);
  75                 if (unlikely(ret))
  76                         goto bad_area_nosemaphore;
  77                 else
  78                         return;
  79         }
  80
  81         info.si_code = SEGV_MAPERR;
  82
  83         /*
  84          * If we're in an interrupt or have no user
  85          * context, we must not take the fault..
  86          */
  87         if (in_atomic() || !mm)
  88                 goto no_context;
  89
  90         if (user_mode(regs))
  91                 flags |= FAULT_FLAG_USER;
  92 retry:
  93         down_read(&mm->mmap_sem);
  94         vma = find_vma(mm, address);
  95         if (!vma)
  96                 goto bad_area;
  97         if (vma->vm_start <= address)
  98                 goto good_area;
  99         if (!(vma->vm_flags & VM_GROWSDOWN))
 100                 goto bad_area;
 101         if (expand_stack(vma, address))
 102                 goto bad_area;
 103
 104         /*
 105          * Ok, we have a good vm_area for this memory access, so
 106          * we can handle it..
 107          */
 108 good_area:
 109         info.si_code = SEGV_ACCERR;
 110
 111         /* Handle protection violation, execute on heap or stack */
 112
 113         if (cause_code == ((ECR_V_PROTV << 16) | ECR_C_PROTV_INST_FETCH))
 114                 goto bad_area;
 115
 116         if (write) {
 117                 if (!(vma->vm_flags & VM_WRITE))
 118                         goto bad_area;
 119                 flags |= FAULT_FLAG_WRITE;
 120         } else {
 121                 if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
 122                         goto bad_area;
 123         }
 124
 125         /*
 126          * If for any reason at all we couldn't handle the fault,
 127          * make sure we exit gracefully rather than endlessly redo
 128          * the fault.
 129          */
 130         fault = handle_mm_fault(mm, vma, address, flags);
 131
 132         /* If Pagefault was interrupted by SIGKILL, exit page fault "early" */
 133         if (unlikely(fatal_signal_pending(current))) {
 134                 if ((fault & VM_FAULT_ERROR) && !(fault & VM_FAULT_RETRY))
 135                         up_read(&mm->mmap_sem);
 136                 if (user_mode(regs))
 137                         return;
 138         }
 139
 140         if (likely(!(fault & VM_FAULT_ERROR))) {
 141                 if (flags & FAULT_FLAG_ALLOW_RETRY) {
 142                         /* To avoid updating stats twice for retry case */
 143                         if (fault & VM_FAULT_MAJOR)
 144                                 tsk->maj_flt++;
 145                         else
 146                                 tsk->min_flt++;
 147
 148                         if (fault & VM_FAULT_RETRY) {
 149                                 flags &= ~FAULT_FLAG_ALLOW_RETRY;
 150                                 flags |= FAULT_FLAG_TRIED;
 151                                 goto retry;
 152                         }
 153                 }
 154
 155                 /* Fault Handled Gracefully */
 156                 up_read(&mm->mmap_sem);
 157                 return;
 158         }
 159
 160         /* TBD: switch to pagefault_out_of_memory() */
 161         if (fault & VM_FAULT_OOM)
 162                 goto out_of_memory;
 163         else if (fault & VM_FAULT_SIGBUS)
 164                 goto do_sigbus;
 165
 166         /* no man's land */
 167         BUG();
 168
 169         /*
 170          * Something tried to access memory that isn't in our memory map..
 171          * Fix it, but check if it's kernel or user first..
 172          */
 173 bad_area:
 174         up_read(&mm->mmap_sem);
 175
 176 bad_area_nosemaphore:
 177         /* User mode accesses just cause a SIGSEGV */
 178         if (user_mode(regs)) {
 179                 tsk->thread.fault_address = address;
 180                 tsk->thread.cause_code = cause_code;
 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, cause_code);
 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         tsk->thread.cause_code = cause_code;
 221         info.si_signo = SIGBUS;
 222         info.si_errno = 0;
 223         info.si_code = BUS_ADRERR;
 224         info.si_addr = (void __user *)address;
 225         force_sig_info(SIGBUS, &info, tsk);
 226 }