release/src-rt-6.x.4708/linux/linux-2.6.36/arch/mips/mm/fault.c

   1 /*
   2  * This file is subject to the terms and conditions of the GNU General Public
   3  * License.  See the file "COPYING" in the main directory of this archive
   4  * for more details.
   5  *
   6  * Copyright (C) 1995 - 2000 by Ralf Baechle
   7  */
   8 #include <linux/signal.h>
   9 #include <linux/sched.h>
  10 #include <linux/interrupt.h>
  11 #include <linux/kernel.h>
  12 #include <linux/errno.h>
  13 #include <linux/string.h>
  14 #include <linux/types.h>
  15 #include <linux/ptrace.h>
  16 #include <linux/mman.h>
  17 #include <linux/mm.h>
  18 #include <linux/smp.h>
  19 #include <linux/module.h>
  20 #include <linux/kprobes.h>
  21
  22 #include <asm/branch.h>
  23 #include <asm/mmu_context.h>
  24 #include <asm/system.h>
  25 #include <asm/uaccess.h>
  26 #include <asm/ptrace.h>
  27 #include <asm/highmem.h>                /* For VMALLOC_END */
  28 #include <linux/kdebug.h>
  29
  30 /*
  31  * This routine handles page faults.  It determines the address,
  32  * and the problem, and then passes it off to one of the appropriate
  33  * routines.
  34  */
  35 asmlinkage void __kprobes do_page_fault(struct pt_regs *regs, unsigned long write,
  36                               unsigned long address)
  37 {
  38         struct vm_area_struct * vma = NULL;
  39         struct task_struct *tsk = current;
  40         struct mm_struct *mm = tsk->mm;
  41         const int field = sizeof(unsigned long) * 2;
  42         siginfo_t info;
  43         int fault;
  44
  45
  46 #ifdef CONFIG_KPROBES
  47         /*
  48          * This is to notify the fault handler of the kprobes.  The
  49          * exception code is redundant as it is also carried in REGS,
  50          * but we pass it anyhow.
  51          */
  52         if (notify_die(DIE_PAGE_FAULT, "page fault", regs, -1,
  53                        (regs->cp0_cause >> 2) & 0x1f, SIGSEGV) == NOTIFY_STOP)
  54                 return;
  55 #endif
  56
  57         info.si_code = SEGV_MAPERR;
  58
  59         /*
  60          * We fault-in kernel-space virtual memory on-demand. The
  61          * 'reference' page table is init_mm.pgd.
  62          *
  63          * NOTE! We MUST NOT take any locks for this case. We may
  64          * be in an interrupt or a critical region, and should
  65          * only copy the information from the master page table,
  66          * nothing more.
  67          */
  68 #ifdef CONFIG_64BIT
  69 # define VMALLOC_FAULT_TARGET no_context
  70 #else
  71 # define VMALLOC_FAULT_TARGET vmalloc_fault
  72 #endif
  73
  74         if (unlikely(address >= VMALLOC_START && address <= VMALLOC_END))
  75                 goto VMALLOC_FAULT_TARGET;
  76 #ifdef MODULE_START
  77         if (unlikely(address >= MODULE_START && address < MODULE_END))
  78                 goto VMALLOC_FAULT_TARGET;
  79 #endif
  80
  81         /*
  82          * If we're in an interrupt or have no user
  83          * context, we must not take the fault..
  84          */
  85         if (in_atomic() || !mm)
  86                 goto bad_area_nosemaphore;
  87
  88         down_read(&mm->mmap_sem);
  89         vma = find_vma(mm, address);
  90         if (!vma)
  91                 goto bad_area;
  92         if (vma->vm_start <= address)
  93                 goto good_area;
  94         if (!(vma->vm_flags & VM_GROWSDOWN))
  95                 goto bad_area;
  96         if (expand_stack(vma, address))
  97                 goto bad_area;
  98 /*
  99  * Ok, we have a good vm_area for this memory access, so
 100  * we can handle it..
 101  */
 102 good_area:
 103         info.si_code = SEGV_ACCERR;
 104
 105         if (write) {
 106                 if (!(vma->vm_flags & VM_WRITE))
 107                         goto bad_area;
 108         } else {
 109                 if (kernel_uses_smartmips_rixi) {
 110                         if (address == regs->cp0_epc && !(vma->vm_flags & VM_EXEC)) {
 111                                 goto bad_area;
 112                         }
 113                         if (!(vma->vm_flags & VM_READ)) {
 114                                 goto bad_area;
 115                         }
 116                 } else {
 117                         if (!(vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)))
 118                                 goto bad_area;
 119                 }
 120         }
 121
 122         /*
 123          * If for any reason at all we couldn't handle the fault,
 124          * make sure we exit gracefully rather than endlessly redo
 125          * the fault.
 126          */
 127         fault = handle_mm_fault(mm, vma, address, write ? FAULT_FLAG_WRITE : 0);
 128         if (unlikely(fault & VM_FAULT_ERROR)) {
 129                 if (fault & VM_FAULT_OOM)
 130                         goto out_of_memory;
 131                 else if (fault & VM_FAULT_SIGBUS)
 132                         goto do_sigbus;
 133                 BUG();
 134         }
 135         if (fault & VM_FAULT_MAJOR)
 136                 tsk->maj_flt++;
 137         else
 138                 tsk->min_flt++;
 139
 140         up_read(&mm->mmap_sem);
 141         return;
 142
 143 /*
 144  * Something tried to access memory that isn't in our memory map..
 145  * Fix it, but check if it's kernel or user first..
 146  */
 147 bad_area:
 148         up_read(&mm->mmap_sem);
 149
 150 bad_area_nosemaphore:
 151         /* User mode accesses just cause a SIGSEGV */
 152         if (user_mode(regs)) {
 153                 tsk->thread.cp0_badvaddr = address;
 154                 tsk->thread.error_code = write;
 155                 info.si_signo = SIGSEGV;
 156                 info.si_errno = 0;
 157                 /* info.si_code has been set above */
 158                 info.si_addr = (void __user *) address;
 159                 force_sig_info(SIGSEGV, &info, tsk);
 160                 return;
 161         }
 162
 163 no_context:
 164         /* Are we prepared to handle this kernel fault?  */
 165         if (fixup_exception(regs)) {
 166                 current->thread.cp0_baduaddr = address;
 167                 return;
 168         }
 169
 170         /*
 171          * Oops. The kernel tried to access some bad page. We'll have to
 172          * terminate things with extreme prejudice.
 173          */
 174         bust_spinlocks(1);
 175
 176         printk(KERN_ALERT "CPU %d Unable to handle kernel paging request at "
 177                "virtual address %0*lx, epc == %0*lx, ra == %0*lx\n",
 178                raw_smp_processor_id(), field, address, field, regs->cp0_epc,
 179                field,  regs->regs[31]);
 180         die("Oops", regs);
 181
 182 out_of_memory:
 183         /*
 184          * We ran out of memory, call the OOM killer, and return the userspace
 185          * (which will retry the fault, or kill us if we got oom-killed).
 186          */
 187         up_read(&mm->mmap_sem);
 188         pagefault_out_of_memory();
 189         return;
 190
 191 do_sigbus:
 192         up_read(&mm->mmap_sem);
 193
 194         /* Kernel mode? Handle exceptions or die */
 195         if (!user_mode(regs))
 196                 goto no_context;
 197         else
 198         /*
 199          * Send a sigbus, regardless of whether we were in kernel
 200          * or user mode.
 201          */
 202         tsk->thread.cp0_badvaddr = address;
 203         info.si_signo = SIGBUS;
 204         info.si_errno = 0;
 205         info.si_code = BUS_ADRERR;
 206         info.si_addr = (void __user *) address;
 207         force_sig_info(SIGBUS, &info, tsk);
 208
 209         return;
 210 #ifndef CONFIG_64BIT
 211 vmalloc_fault:
 212         {
 213                 /*
 214                  * Synchronize this task's top level page-table
 215                  * with the 'reference' page table.
 216                  *
 217                  * Do _not_ use "tsk" here. We might be inside
 218                  * an interrupt in the middle of a task switch..
 219                  */
 220                 int offset = __pgd_offset(address);
 221                 pgd_t *pgd, *pgd_k;
 222                 pud_t *pud, *pud_k;
 223                 pmd_t *pmd, *pmd_k;
 224                 pte_t *pte_k;
 225
 226                 pgd = (pgd_t *) pgd_current[raw_smp_processor_id()] + offset;
 227                 pgd_k = init_mm.pgd + offset;
 228
 229                 if (!pgd_present(*pgd_k))
 230                         goto no_context;
 231                 set_pgd(pgd, *pgd_k);
 232
 233                 pud = pud_offset(pgd, address);
 234                 pud_k = pud_offset(pgd_k, address);
 235                 if (!pud_present(*pud_k))
 236                         goto no_context;
 237
 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                 return;
 248         }
 249 #endif
 250 }