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 <linux/perf_event.h>
  18 #include <asm/pgalloc.h>
  19 #include <asm/mmu.h>
  20
  21 static int handle_vmalloc_fault(unsigned long address)
  22 {
  23         /*
  24          * Synchronize this task's top level page-table
  25          * with the 'reference' page table.
  26          */
  27         pgd_t *pgd, *pgd_k;
  28         pud_t *pud, *pud_k;
  29         pmd_t *pmd, *pmd_k;
  30
  31         pgd = pgd_offset_fast(current->active_mm, address);
  32         pgd_k = pgd_offset_k(address);
  33
  34         if (!pgd_present(*pgd_k))
  35                 goto bad_area;
  36
  37         pud = pud_offset(pgd, address);
  38         pud_k = pud_offset(pgd_k, address);
  39         if (!pud_present(*pud_k))
  40                 goto bad_area;
  41
  42         pmd = pmd_offset(pud, address);
  43         pmd_k = pmd_offset(pud_k, address);
  44         if (!pmd_present(*pmd_k))
  45                 goto bad_area;
  46
  47         set_pmd(pmd, *pmd_k);
  48
  49         /* XXX: create the TLB entry here */
  50         return 0;
  51
  52 bad_area:
  53         return 1;
  54 }
  55
  56 void do_page_fault(unsigned long address, struct pt_regs *regs)
  57 {
  58         struct vm_area_struct *vma = NULL;
  59         struct task_struct *tsk = current;
  60         struct mm_struct *mm = tsk->mm;
  61         siginfo_t info;
  62         int fault, ret;
  63         int write = regs->ecr_cause & ECR_C_PROTV_STORE;  /* ST/EX */
  64         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
  65
  66         /*
  67          * We fault-in kernel-space virtual memory on-demand. The
  68          * 'reference' page table is init_mm.pgd.
  69          *
  70          * NOTE! We MUST NOT take any locks for this case. We may
  71          * be in an interrupt or a critical region, and should
  72          * only copy the information from the master page table,
  73          * nothing more.
  74          */
  75         if (address >= VMALLOC_START && address <= VMALLOC_END) {
  76                 ret = handle_vmalloc_fault(address);
  77                 if (unlikely(ret))
  78                         goto bad_area_nosemaphore;
  79                 else
  80                         return;
  81         }
  82
  83         info.si_code = SEGV_MAPERR;
  84
  85         /*
  86          * If we're in an interrupt or have no user
  87          * context, we must not take the fault..
  88          */
  89         if (faulthandler_disabled() || !mm)
  90                 goto no_context;
  91
  92         if (user_mode(regs))
  93                 flags |= FAULT_FLAG_USER;
  94 retry:
  95         down_read(&mm->mmap_sem);
  96         vma = find_vma(mm, address);
  97         if (!vma)
  98                 goto bad_area;
  99         if (vma->vm_start <= address)
 100                 goto good_area;
 101         if (!(vma->vm_flags & VM_GROWSDOWN))
 102                 goto bad_area;
 103         if (expand_stack(vma, address))
 104                 goto bad_area;
 105
 106         /*
 107          * Ok, we have a good vm_area for this memory access, so
 108          * we can handle it..
 109          */
 110 good_area:
 111         info.si_code = SEGV_ACCERR;
 112
 113         /* Handle protection violation, execute on heap or stack */
 114
 115         if ((regs->ecr_vec == ECR_V_PROTV) &&
 116             (regs->ecr_cause == ECR_C_PROTV_INST_FETCH))
 117                 goto bad_area;
 118
 119         if (write) {
 120                 if (!(vma->vm_flags & VM_WRITE))
 121                         goto bad_area;
 122                 flags |= FAULT_FLAG_WRITE;
 123         } else {
 124                 if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
 125                         goto bad_area;
 126         }
 127
 128         /*
 129          * If for any reason at all we couldn't handle the fault,
 130          * make sure we exit gracefully rather than endlessly redo
 131          * the fault.
 132          */
 133         fault = handle_mm_fault(mm, vma, address, flags);
 134
 135         /* If Pagefault was interrupted by SIGKILL, exit page fault "early" */
 136         if (unlikely(fatal_signal_pending(current))) {
 137                 if ((fault & VM_FAULT_ERROR) && !(fault & VM_FAULT_RETRY))
 138                         up_read(&mm->mmap_sem);
 139                 if (user_mode(regs))
 140                         return;
 141         }
 142
 143         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 144
 145         if (likely(!(fault & VM_FAULT_ERROR))) {
 146                 if (flags & FAULT_FLAG_ALLOW_RETRY) {
 147                         /* To avoid updating stats twice for retry case */
 148                         if (fault & VM_FAULT_MAJOR) {
 149                                 tsk->maj_flt++;
 150                                 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
 151                                               regs, address);
 152                         } else {
 153                                 tsk->min_flt++;
 154                                 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
 155                                               regs, address);
 156                         }
 157
 158                         if (fault & VM_FAULT_RETRY) {
 159                                 flags &= ~FAULT_FLAG_ALLOW_RETRY;
 160                                 flags |= FAULT_FLAG_TRIED;
 161                                 goto retry;
 162                         }
 163                 }
 164
 165                 /* Fault Handled Gracefully */
 166                 up_read(&mm->mmap_sem);
 167                 return;
 168         }
 169
 170         if (fault & VM_FAULT_OOM)
 171                 goto out_of_memory;
 172         else if (fault & VM_FAULT_SIGSEGV)
 173                 goto bad_area;
 174         else if (fault & VM_FAULT_SIGBUS)
 175                 goto do_sigbus;
 176
 177         /* no man's land */
 178         BUG();
 179
 180         /*
 181          * Something tried to access memory that isn't in our memory map..
 182          * Fix it, but check if it's kernel or user first..
 183          */
 184 bad_area:
 185         up_read(&mm->mmap_sem);
 186
 187 bad_area_nosemaphore:
 188         /* User mode accesses just cause a SIGSEGV */
 189         if (user_mode(regs)) {
 190                 tsk->thread.fault_address = address;
 191                 info.si_signo = SIGSEGV;
 192                 info.si_errno = 0;
 193                 /* info.si_code has been set above */
 194                 info.si_addr = (void __user *)address;
 195                 force_sig_info(SIGSEGV, &info, tsk);
 196                 return;
 197         }
 198
 199 no_context:
 200         /* Are we prepared to handle this kernel fault?
 201          *
 202          * (The kernel has valid exception-points in the source
 203          *  when it acesses user-memory. When it fails in one
 204          *  of those points, we find it in a table and do a jump
 205          *  to some fixup code that loads an appropriate error
 206          *  code)
 207          */
 208         if (fixup_exception(regs))
 209                 return;
 210
 211         die("Oops", regs, address);
 212
 213 out_of_memory:
 214         up_read(&mm->mmap_sem);
 215
 216         if (user_mode(regs)) {
 217                 pagefault_out_of_memory();
 218                 return;
 219         }
 220
 221         goto no_context;
 222
 223 do_sigbus:
 224         up_read(&mm->mmap_sem);
 225
 226         if (!user_mode(regs))
 227                 goto no_context;
 228
 229         tsk->thread.fault_address = address;
 230         info.si_signo = SIGBUS;
 231         info.si_errno = 0;
 232         info.si_code = BUS_ADRERR;
 233         info.si_addr = (void __user *)address;
 234         force_sig_info(SIGBUS, &info, tsk);
 235 }