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 = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
  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 retry:
  90                 down_read(&mm->mmap_sem);
  91         }
  92
  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  * Ok, we have a good vm_area for this memory access, so
 104  * we can handle it..
 105  */
 106 good_area:
 107         code = SEGV_ACCERR;
 108
 109         switch (cause) {
 110         case EXC_SUPERV_INSN_ACCESS:
 111                 goto bad_area;
 112         case EXC_SUPERV_DATA_ACCESS:
 113                 goto bad_area;
 114         case EXC_X_PROTECTION_FAULT:
 115                 if (!(vma->vm_flags & VM_EXEC))
 116                         goto bad_area;
 117                 break;
 118         case EXC_R_PROTECTION_FAULT:
 119                 if (!(vma->vm_flags & VM_READ))
 120                         goto bad_area;
 121                 break;
 122         case EXC_W_PROTECTION_FAULT:
 123                 if (!(vma->vm_flags & VM_WRITE))
 124                         goto bad_area;
 125                 flags = FAULT_FLAG_WRITE;
 126                 break;
 127         }
 128
 129 survive:
 130         /*
 131          * If for any reason at all we couldn't handle the fault,
 132          * make sure we exit gracefully rather than endlessly redo
 133          * the fault.
 134          */
 135         fault = handle_mm_fault(mm, vma, address, flags);
 136
 137         if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
 138                 return;
 139
 140         if (unlikely(fault & VM_FAULT_ERROR)) {
 141                 if (fault & VM_FAULT_OOM)
 142                         goto out_of_memory;
 143                 else if (fault & VM_FAULT_SIGSEGV)
 144                         goto bad_area;
 145                 else if (fault & VM_FAULT_SIGBUS)
 146                         goto do_sigbus;
 147                 BUG();
 148         }
 149
 150         /*
 151          * Major/minor page fault accounting is only done on the
 152          * initial attempt. If we go through a retry, it is extremely
 153          * likely that the page will be found in page cache at that point.
 154          */
 155         if (flags & FAULT_FLAG_ALLOW_RETRY) {
 156                 if (fault & VM_FAULT_MAJOR)
 157                         current->maj_flt++;
 158                 else
 159                         current->min_flt++;
 160                 if (fault & VM_FAULT_RETRY) {
 161                         /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
 162                          * of starvation. */
 163                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
 164                         flags |= FAULT_FLAG_TRIED;
 165
 166                         /*
 167                          * No need to up_read(&mm->mmap_sem) as we would
 168                          * have already released it in __lock_page_or_retry
 169                          * in mm/filemap.c.
 170                          */
 171
 172                         goto retry;
 173                 }
 174         }
 175
 176         up_read(&mm->mmap_sem);
 177         return;
 178
 179 /*
 180  * Something tried to access memory that isn't in our memory map..
 181  * Fix it, but check if it's kernel or user first..
 182  */
 183 bad_area:
 184         up_read(&mm->mmap_sem);
 185
 186 bad_area_nosemaphore:
 187         /* User mode accesses just cause a SIGSEGV */
 188         if (user_mode(regs)) {
 189                 if (unhandled_signal(current, SIGSEGV) && printk_ratelimit()) {
 190                         pr_info("%s: unhandled page fault (%d) at 0x%08lx, "
 191                                 "cause %ld\n", current->comm, SIGSEGV, address, cause);
 192                         show_regs(regs);
 193                 }
 194                 _exception(SIGSEGV, regs, code, address);
 195                 return;
 196         }
 197
 198 no_context:
 199         /* Are we prepared to handle this kernel fault? */
 200         if (fixup_exception(regs))
 201                 return;
 202
 203         /*
 204          * Oops. The kernel tried to access some bad page. We'll have to
 205          * terminate things with extreme prejudice.
 206          */
 207         bust_spinlocks(1);
 208
 209         pr_alert("Unable to handle kernel %s at virtual address %08lx",
 210                 address < PAGE_SIZE ? "NULL pointer dereference" :
 211                 "paging request", address);
 212         pr_alert("ea = %08lx, ra = %08lx, cause = %ld\n", regs->ea, regs->ra,
 213                 cause);
 214         panic("Oops");
 215         return;
 216
 217 /*
 218  * We ran out of memory, or some other thing happened to us that made
 219  * us unable to handle the page fault gracefully.
 220  */
 221 out_of_memory:
 222         up_read(&mm->mmap_sem);
 223         if (is_global_init(tsk)) {
 224                 yield();
 225                 down_read(&mm->mmap_sem);
 226                 goto survive;
 227         }
 228         if (!user_mode(regs))
 229                 goto no_context;
 230         pagefault_out_of_memory();
 231         return;
 232
 233 do_sigbus:
 234         up_read(&mm->mmap_sem);
 235
 236         /* Kernel mode? Handle exceptions or die */
 237         if (!user_mode(regs))
 238                 goto no_context;
 239
 240         _exception(SIGBUS, regs, BUS_ADRERR, address);
 241         return;
 242
 243 vmalloc_fault:
 244         {
 245                 /*
 246                  * Synchronize this task's top level page-table
 247                  * with the 'reference' page table.
 248                  *
 249                  * Do _not_ use "tsk" here. We might be inside
 250                  * an interrupt in the middle of a task switch..
 251                  */
 252                 int offset = pgd_index(address);
 253                 pgd_t *pgd, *pgd_k;
 254                 pud_t *pud, *pud_k;
 255                 pmd_t *pmd, *pmd_k;
 256                 pte_t *pte_k;
 257
 258                 pgd = pgd_current + offset;
 259                 pgd_k = init_mm.pgd + offset;
 260
 261                 if (!pgd_present(*pgd_k))
 262                         goto no_context;
 263                 set_pgd(pgd, *pgd_k);
 264
 265                 pud = pud_offset(pgd, address);
 266                 pud_k = pud_offset(pgd_k, address);
 267                 if (!pud_present(*pud_k))
 268                         goto no_context;
 269                 pmd = pmd_offset(pud, address);
 270                 pmd_k = pmd_offset(pud_k, address);
 271                 if (!pmd_present(*pmd_k))
 272                         goto no_context;
 273                 set_pmd(pmd, *pmd_k);
 274
 275                 pte_k = pte_offset_kernel(pmd_k, address);
 276                 if (!pte_present(*pte_k))
 277                         goto no_context;
 278
 279                 flush_tlb_one(address);
 280                 return;
 281         }
 282 }