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/signal.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 <linux/mm_types.h>
  19 #include <asm/pgalloc.h>
  20 #include <asm/mmu.h>
  21
  22 /*
  23  * kernel virtual address is required to implement vmalloc/pkmap/fixmap
  24  * Refer to asm/processor.h for System Memory Map
  25  *
  26  * It simply copies the PMD entry (pointer to 2nd level page table or hugepage)
  27  * from swapper pgdir to task pgdir. The 2nd level table/page is thus shared
  28  */
  29 noinline static int handle_kernel_vaddr_fault(unsigned long address)
  30 {
  31         /*
  32          * Synchronize this task's top level page-table
  33          * with the 'reference' page table.
  34          */
  35         pgd_t *pgd, *pgd_k;
  36         pud_t *pud, *pud_k;
  37         pmd_t *pmd, *pmd_k;
  38
  39         pgd = pgd_offset_fast(current->active_mm, address);
  40         pgd_k = pgd_offset_k(address);
  41
  42         if (!pgd_present(*pgd_k))
  43                 goto bad_area;
  44
  45         pud = pud_offset(pgd, address);
  46         pud_k = pud_offset(pgd_k, address);
  47         if (!pud_present(*pud_k))
  48                 goto bad_area;
  49
  50         pmd = pmd_offset(pud, address);
  51         pmd_k = pmd_offset(pud_k, address);
  52         if (!pmd_present(*pmd_k))
  53                 goto bad_area;
  54
  55         set_pmd(pmd, *pmd_k);
  56
  57         /* XXX: create the TLB entry here */
  58         return 0;
  59
  60 bad_area:
  61         return 1;
  62 }
  63
  64 void do_page_fault(unsigned long address, struct pt_regs *regs)
  65 {
  66         struct vm_area_struct *vma = NULL;
  67         struct task_struct *tsk = current;
  68         struct mm_struct *mm = tsk->mm;
  69         int si_code = 0;
  70         int ret;
  71         vm_fault_t fault;
  72         int write = regs->ecr_cause & ECR_C_PROTV_STORE;  /* ST/EX */
  73         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
  74
  75         /*
  76          * We fault-in kernel-space virtual memory on-demand. The
  77          * 'reference' page table is init_mm.pgd.
  78          *
  79          * NOTE! We MUST NOT take any locks for this case. We may
  80          * be in an interrupt or a critical region, and should
  81          * only copy the information from the master page table,
  82          * nothing more.
  83          */
  84         if (address >= VMALLOC_START) {
  85                 ret = handle_kernel_vaddr_fault(address);
  86                 if (unlikely(ret))
  87                         goto bad_area_nosemaphore;
  88                 else
  89                         return;
  90         }
  91
  92         si_code = SEGV_MAPERR;
  93
  94         /*
  95          * If we're in an interrupt or have no user
  96          * context, we must not take the fault..
  97          */
  98         if (faulthandler_disabled() || !mm)
  99                 goto no_context;
 100
 101         if (user_mode(regs))
 102                 flags |= FAULT_FLAG_USER;
 103 retry:
 104         down_read(&mm->mmap_sem);
 105         vma = find_vma(mm, address);
 106         if (!vma)
 107                 goto bad_area;
 108         if (vma->vm_start <= address)
 109                 goto good_area;
 110         if (!(vma->vm_flags & VM_GROWSDOWN))
 111                 goto bad_area;
 112         if (expand_stack(vma, address))
 113                 goto bad_area;
 114
 115         /*
 116          * Ok, we have a good vm_area for this memory access, so
 117          * we can handle it..
 118          */
 119 good_area:
 120         si_code = SEGV_ACCERR;
 121
 122         /* Handle protection violation, execute on heap or stack */
 123
 124         if ((regs->ecr_vec == ECR_V_PROTV) &&
 125             (regs->ecr_cause == ECR_C_PROTV_INST_FETCH))
 126                 goto bad_area;
 127
 128         if (write) {
 129                 if (!(vma->vm_flags & VM_WRITE))
 130                         goto bad_area;
 131                 flags |= FAULT_FLAG_WRITE;
 132         } else {
 133                 if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
 134                         goto bad_area;
 135         }
 136
 137         /*
 138          * If for any reason at all we couldn't handle the fault,
 139          * make sure we exit gracefully rather than endlessly redo
 140          * the fault.
 141          */
 142         fault = handle_mm_fault(vma, address, flags);
 143
 144         if (fatal_signal_pending(current)) {
 145
 146                 /*
 147                  * if fault retry, mmap_sem already relinquished by core mm
 148                  * so OK to return to user mode (with signal handled first)
 149                  */
 150                 if (fault & VM_FAULT_RETRY) {
 151                         if (!user_mode(regs))
 152                                 goto no_context;
 153                         return;
 154                 }
 155         }
 156
 157         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 158
 159         if (likely(!(fault & VM_FAULT_ERROR))) {
 160                 if (flags & FAULT_FLAG_ALLOW_RETRY) {
 161                         /* To avoid updating stats twice for retry case */
 162                         if (fault & VM_FAULT_MAJOR) {
 163                                 tsk->maj_flt++;
 164                                 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
 165                                               regs, address);
 166                         } else {
 167                                 tsk->min_flt++;
 168                                 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
 169                                               regs, address);
 170                         }
 171
 172                         if (fault & VM_FAULT_RETRY) {
 173                                 flags &= ~FAULT_FLAG_ALLOW_RETRY;
 174                                 flags |= FAULT_FLAG_TRIED;
 175                                 goto retry;
 176                         }
 177                 }
 178
 179                 /* Fault Handled Gracefully */
 180                 up_read(&mm->mmap_sem);
 181                 return;
 182         }
 183
 184         if (fault & VM_FAULT_OOM)
 185                 goto out_of_memory;
 186         else if (fault & VM_FAULT_SIGSEGV)
 187                 goto bad_area;
 188         else if (fault & VM_FAULT_SIGBUS)
 189                 goto do_sigbus;
 190
 191         /* no man's land */
 192         BUG();
 193
 194         /*
 195          * Something tried to access memory that isn't in our memory map..
 196          * Fix it, but check if it's kernel or user first..
 197          */
 198 bad_area:
 199         up_read(&mm->mmap_sem);
 200
 201 bad_area_nosemaphore:
 202         /* User mode accesses just cause a SIGSEGV */
 203         if (user_mode(regs)) {
 204                 tsk->thread.fault_address = address;
 205                 force_sig_fault(SIGSEGV, si_code, (void __user *)address, tsk);
 206                 return;
 207         }
 208
 209 no_context:
 210         /* Are we prepared to handle this kernel fault?
 211          *
 212          * (The kernel has valid exception-points in the source
 213          *  when it accesses user-memory. When it fails in one
 214          *  of those points, we find it in a table and do a jump
 215          *  to some fixup code that loads an appropriate error
 216          *  code)
 217          */
 218         if (fixup_exception(regs))
 219                 return;
 220
 221         die("Oops", regs, address);
 222
 223 out_of_memory:
 224         up_read(&mm->mmap_sem);
 225
 226         if (user_mode(regs)) {
 227                 pagefault_out_of_memory();
 228                 return;
 229         }
 230
 231         goto no_context;
 232
 233 do_sigbus:
 234         up_read(&mm->mmap_sem);
 235
 236         if (!user_mode(regs))
 237                 goto no_context;
 238
 239         tsk->thread.fault_address = address;
 240         force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address, tsk);
 241 }