arch/nios2/mm/fault.c

   1 /*
   2  * Copyright (C) 2009 Wind River Systems Inc
   3  *   Implemented by fredrik.markstrom@gmail.com and ivarholmqvist@gmail.com
   4  *
   5  * based on arch/mips/mm/fault.c which is:
   6  *
   7  * Copyright (C) 1995-2000 Ralf Baechle
   8  *
   9  * This file is subject to the terms and conditions of the GNU General Public
  10  * License.  See the file "COPYING" in the main directory of this archive
  11  * for more details.
  12  */
  13
  14 #include <linux/signal.h>
  15 #include <linux/sched.h>
  16 #include <linux/interrupt.h>
  17 #include <linux/kernel.h>
  18 #include <linux/errno.h>
  19 #include <linux/string.h>
  20 #include <linux/types.h>
  21 #include <linux/ptrace.h>
  22 #include <linux/mman.h>
  23 #include <linux/mm.h>
  24 #include <linux/module.h>
  25 #include <linux/uaccess.h>
  26 #include <linux/ptrace.h>
  27
  28 #include <asm/mmu_context.h>
  29 #include <asm/traps.h>
  30
  31 #define EXC_SUPERV_INSN_ACCESS  9  /* Supervisor only instruction address */
  32 #define EXC_SUPERV_DATA_ACCESS  11 /* Supervisor only data address */
  33 #define EXC_X_PROTECTION_FAULT  13 /* TLB permission violation (x) */
  34 #define EXC_R_PROTECTION_FAULT  14 /* TLB permission violation (r) */
  35 #define EXC_W_PROTECTION_FAULT  15 /* TLB permission violation (w) */
  36
  37 /*
  38  * This routine handles page faults.  It determines the address,
  39  * and the problem, and then passes it off to one of the appropriate
  40  * routines.
  41  */
  42 asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long cause,
  43                                 unsigned long address)
  44 {
  45         struct vm_area_struct *vma = NULL;
  46         struct task_struct *tsk = current;
  47         struct mm_struct *mm = tsk->mm;
  48         int code = SEGV_MAPERR;
  49         int fault;
  50         unsigned int flags = 0;
  51
  52         cause >>= 2;
  53
  54         /* Restart the instruction */
  55         regs->ea -= 4;
  56
  57         /*
  58          * We fault-in kernel-space virtual memory on-demand. The
  59          * 'reference' page table is init_mm.pgd.
  60          *
  61          * NOTE! We MUST NOT take any locks for this case. We may
  62          * be in an interrupt or a critical region, and should
  63          * only copy the information from the master page table,
  64          * nothing more.
  65          */
  66         if (unlikely(address >= VMALLOC_START && address <= VMALLOC_END)) {
  67                 if (user_mode(regs))
  68                         goto bad_area_nosemaphore;
  69                 else
  70                         goto vmalloc_fault;
  71         }
  72
  73         if (unlikely(address >= TASK_SIZE))
  74                 goto bad_area_nosemaphore;
  75
  76         /*
  77          * If we're in an interrupt or have no user
  78          * context, we must not take the fault..
  79          */
  80         if (in_atomic() || !mm)
  81                 goto bad_area_nosemaphore;
  82
  83         if (user_mode(regs))
  84                 flags |= FAULT_FLAG_USER;
  85
  86         if (!down_read_trylock(&mm->mmap_sem)) {
  87                 if (!user_mode(regs) && !search_exception_tables(regs->ea))
  88                         goto bad_area_nosemaphore;
  89                 down_read(&mm->mmap_sem);
  90         }
  91
  92         vma = find_vma(mm, address);
  93         if (!vma)
  94                 goto bad_area;
  95         if (vma->vm_start <= address)
  96                 goto good_area;
  97         if (!(vma->vm_flags & VM_GROWSDOWN))
  98                 goto bad_area;
  99         if (expand_stack(vma, address))
 100                 goto bad_area;
 101 /*
 102  * Ok, we have a good vm_area for this memory access, so
 103  * we can handle it..
 104  */
 105 good_area:
 106         code = SEGV_ACCERR;
 107
 108         switch (cause) {
 109         case EXC_SUPERV_INSN_ACCESS:
 110                 goto bad_area;
 111         case EXC_SUPERV_DATA_ACCESS:
 112                 goto bad_area;
 113         case EXC_X_PROTECTION_FAULT:
 114                 if (!(vma->vm_flags & VM_EXEC))
 115                         goto bad_area;
 116                 break;
 117         case EXC_R_PROTECTION_FAULT:
 118                 if (!(vma->vm_flags & VM_READ))
 119                         goto bad_area;
 120                 break;
 121         case EXC_W_PROTECTION_FAULT:
 122                 if (!(vma->vm_flags & VM_WRITE))
 123                         goto bad_area;
 124                 flags = FAULT_FLAG_WRITE;
 125                 break;
 126         }
 127
 128 survive:
 129         /*
 130          * If for any reason at all we couldn't handle the fault,
 131          * make sure we exit gracefully rather than endlessly redo
 132          * the fault.
 133          */
 134         fault = handle_mm_fault(mm, vma, address, flags);
 135         if (unlikely(fault & VM_FAULT_ERROR)) {
 136                 if (fault & VM_FAULT_OOM)
 137                         goto out_of_memory;
 138                 else if (fault & VM_FAULT_SIGBUS)
 139                         goto do_sigbus;
 140                 BUG();
 141         }
 142         if (fault & VM_FAULT_MAJOR)
 143                 tsk->maj_flt++;
 144         else
 145                 tsk->min_flt++;
 146
 147         up_read(&mm->mmap_sem);
 148         return;
 149
 150 /*
 151  * Something tried to access memory that isn't in our memory map..
 152  * Fix it, but check if it's kernel or user first..
 153  */
 154 bad_area:
 155         up_read(&mm->mmap_sem);
 156
 157 bad_area_nosemaphore:
 158         /* User mode accesses just cause a SIGSEGV */
 159         if (user_mode(regs)) {
 160                 pr_alert("%s: unhandled page fault (%d) at 0x%08lx, "
 161                         "cause %ld\n", current->comm, SIGSEGV, address, cause);
 162                 show_regs(regs);
 163                 _exception(SIGSEGV, regs, code, address);
 164                 return;
 165         }
 166
 167 no_context:
 168         /* Are we prepared to handle this kernel fault? */
 169         if (fixup_exception(regs))
 170                 return;
 171
 172         /*
 173          * Oops. The kernel tried to access some bad page. We'll have to
 174          * terminate things with extreme prejudice.
 175          */
 176         bust_spinlocks(1);
 177
 178         pr_alert("Unable to handle kernel %s at virtual address %08lx",
 179                 address < PAGE_SIZE ? "NULL pointer dereference" :
 180                 "paging request", address);
 181         pr_alert("ea = %08lx, ra = %08lx, cause = %ld\n", regs->ea, regs->ra,
 182                 cause);
 183         panic("Oops");
 184         return;
 185
 186 /*
 187  * We ran out of memory, or some other thing happened to us that made
 188  * us unable to handle the page fault gracefully.
 189  */
 190 out_of_memory:
 191         up_read(&mm->mmap_sem);
 192         if (is_global_init(tsk)) {
 193                 yield();
 194                 down_read(&mm->mmap_sem);
 195                 goto survive;
 196         }
 197         if (!user_mode(regs))
 198                 goto no_context;
 199         pagefault_out_of_memory();
 200         return;
 201
 202 do_sigbus:
 203         up_read(&mm->mmap_sem);
 204
 205         /* Kernel mode? Handle exceptions or die */
 206         if (!user_mode(regs))
 207                 goto no_context;
 208
 209         _exception(SIGBUS, regs, BUS_ADRERR, address);
 210         return;
 211
 212 vmalloc_fault:
 213         {
 214                 /*
 215                  * Synchronize this task's top level page-table
 216                  * with the 'reference' page table.
 217                  *
 218                  * Do _not_ use "tsk" here. We might be inside
 219                  * an interrupt in the middle of a task switch..
 220                  */
 221                 int offset = pgd_index(address);
 222                 pgd_t *pgd, *pgd_k;
 223                 pud_t *pud, *pud_k;
 224                 pmd_t *pmd, *pmd_k;
 225                 pte_t *pte_k;
 226
 227                 pgd = pgd_current + offset;
 228                 pgd_k = init_mm.pgd + offset;
 229
 230                 if (!pgd_present(*pgd_k))
 231                         goto no_context;
 232                 set_pgd(pgd, *pgd_k);
 233
 234                 pud = pud_offset(pgd, address);
 235                 pud_k = pud_offset(pgd_k, address);
 236                 if (!pud_present(*pud_k))
 237                         goto no_context;
 238                 pmd = pmd_offset(pud, address);
 239                 pmd_k = pmd_offset(pud_k, address);
 240                 if (!pmd_present(*pmd_k))
 241                         goto no_context;
 242                 set_pmd(pmd, *pmd_k);
 243
 244                 pte_k = pte_offset_kernel(pmd_k, address);
 245                 if (!pte_present(*pte_k))
 246                         goto no_context;
 247
 248                 flush_tlb_one(address);
 249                 return;
 250         }
 251 }