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/smp_lock.h>
  20 #include <linux/vt_kern.h>              /* For unblank_screen() */
  21 #include <linux/module.h>
  22
  23 #include <asm/branch.h>
  24 #include <asm/mmu_context.h>
  25 #include <asm/system.h>
  26 #include <asm/uaccess.h>
  27 #include <asm/ptrace.h>
  28
  29 /*
  30  * This routine handles page faults.  It determines the address,
  31  * and the problem, and then passes it off to one of the appropriate
  32  * routines.
  33  */
  34 asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long write,
  35                               unsigned long address)
  36 {
  37         struct vm_area_struct * vma = NULL;
  38         struct task_struct *tsk = current;
  39         struct mm_struct *mm = tsk->mm;
  40         const int field = sizeof(unsigned long) * 2;
  41         siginfo_t info;
  42
  43 #if 0
  44         printk("Cpu%d[%s:%d:%0*lx:%ld:%0*lx]\n", smp_processor_id(),
  45                current->comm, current->pid, field, address, write,
  46                field, regs->cp0_epc);
  47 #endif
  48
  49         info.si_code = SEGV_MAPERR;
  50
  51         /*
  52          * We fault-in kernel-space virtual memory on-demand. The
  53          * 'reference' page table is init_mm.pgd.
  54          *
  55          * NOTE! We MUST NOT take any locks for this case. We may
  56          * be in an interrupt or a critical region, and should
  57          * only copy the information from the master page table,
  58          * nothing more.
  59          */
  60         if (unlikely(address >= VMALLOC_START))
  61                 goto vmalloc_fault;
  62
  63         /*
  64          * If we're in an interrupt or have no user
  65          * context, we must not take the fault..
  66          */
  67         if (in_atomic() || !mm)
  68                 goto bad_area_nosemaphore;
  69
  70         down_read(&mm->mmap_sem);
  71         vma = find_vma(mm, address);
  72         if (!vma)
  73                 goto bad_area;
  74         if (vma->vm_start <= address)
  75                 goto good_area;
  76         if (!(vma->vm_flags & VM_GROWSDOWN))
  77                 goto bad_area;
  78         if (expand_stack(vma, address))
  79                 goto bad_area;
  80 /*
  81  * Ok, we have a good vm_area for this memory access, so
  82  * we can handle it..
  83  */
  84 good_area:
  85         info.si_code = SEGV_ACCERR;
  86
  87         if (write) {
  88                 if (!(vma->vm_flags & VM_WRITE))
  89                         goto bad_area;
  90         } else {
  91                 if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
  92                         goto bad_area;
  93         }
  94
  95 survive:
  96         /*
  97          * If for any reason at all we couldn't handle the fault,
  98          * make sure we exit gracefully rather than endlessly redo
  99          * the fault.
 100          */
 101         switch (handle_mm_fault(mm, vma, address, write)) {
 102         case VM_FAULT_MINOR:
 103                 tsk->min_flt++;
 104                 break;
 105         case VM_FAULT_MAJOR:
 106                 tsk->maj_flt++;
 107                 break;
 108         case VM_FAULT_SIGBUS:
 109                 goto do_sigbus;
 110         case VM_FAULT_OOM:
 111                 goto out_of_memory;
 112         default:
 113                 BUG();
 114         }
 115
 116         up_read(&mm->mmap_sem);
 117         return;
 118
 119 /*
 120  * Something tried to access memory that isn't in our memory map..
 121  * Fix it, but check if it's kernel or user first..
 122  */
 123 bad_area:
 124         up_read(&mm->mmap_sem);
 125
 126 bad_area_nosemaphore:
 127         /* User mode accesses just cause a SIGSEGV */
 128         if (user_mode(regs)) {
 129                 tsk->thread.cp0_badvaddr = address;
 130                 tsk->thread.error_code = write;
 131 #if 0
 132                 printk("do_page_fault() #2: sending SIGSEGV to %s for "
 133                        "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n",
 134                        tsk->comm,
 135                        write ? "write access to" : "read access from",
 136                        field, address,
 137                        field, (unsigned long) regs->cp0_epc,
 138                        field, (unsigned long) regs->regs[31]);
 139 #endif
 140                 info.si_signo = SIGSEGV;
 141                 info.si_errno = 0;
 142                 /* info.si_code has been set above */
 143                 info.si_addr = (void *) address;
 144                 force_sig_info(SIGSEGV, &info, tsk);
 145                 return;
 146         }
 147
 148 no_context:
 149         /* Are we prepared to handle this kernel fault?  */
 150         if (fixup_exception(regs)) {
 151                 current->thread.cp0_baduaddr = address;
 152                 return;
 153         }
 154
 155         /*
 156          * Oops. The kernel tried to access some bad page. We'll have to
 157          * terminate things with extreme prejudice.
 158          */
 159
 160         bust_spinlocks(1);
 161
 162         printk(KERN_ALERT "CPU %d Unable to handle kernel paging request at "
 163                "virtual address %0*lx, epc == %0*lx, ra == %0*lx\n",
 164                smp_processor_id(), field, address, field, regs->cp0_epc,
 165                field,  regs->regs[31]);
 166         die("Oops", regs);
 167
 168 /*
 169  * We ran out of memory, or some other thing happened to us that made
 170  * us unable to handle the page fault gracefully.
 171  */
 172 out_of_memory:
 173         up_read(&mm->mmap_sem);
 174         if (tsk->pid == 1) {
 175                 yield();
 176                 down_read(&mm->mmap_sem);
 177                 goto survive;
 178         }
 179         printk("VM: killing process %s\n", tsk->comm);
 180         if (user_mode(regs))
 181                 do_exit(SIGKILL);
 182         goto no_context;
 183
 184 do_sigbus:
 185         up_read(&mm->mmap_sem);
 186
 187         /* Kernel mode? Handle exceptions or die */
 188         if (!user_mode(regs))
 189                 goto no_context;
 190
 191         /*
 192          * Send a sigbus, regardless of whether we were in kernel
 193          * or user mode.
 194          */
 195         tsk->thread.cp0_badvaddr = address;
 196         info.si_signo = SIGBUS;
 197         info.si_errno = 0;
 198         info.si_code = BUS_ADRERR;
 199         info.si_addr = (void *) address;
 200         force_sig_info(SIGBUS, &info, tsk);
 201
 202         return;
 203
 204 vmalloc_fault:
 205         {
 206                 /*
 207                  * Synchronize this task's top level page-table
 208                  * with the 'reference' page table.
 209                  *
 210                  * Do _not_ use "tsk" here. We might be inside
 211                  * an interrupt in the middle of a task switch..
 212                  */
 213                 int offset = __pgd_offset(address);
 214                 pgd_t *pgd, *pgd_k;
 215                 pmd_t *pmd, *pmd_k;
 216                 pte_t *pte_k;
 217
 218                 pgd = (pgd_t *) pgd_current[smp_processor_id()] + offset;
 219                 pgd_k = init_mm.pgd + offset;
 220
 221                 if (!pgd_present(*pgd_k))
 222                         goto no_context;
 223                 set_pgd(pgd, *pgd_k);
 224
 225                 pmd = pmd_offset(pgd, address);
 226                 pmd_k = pmd_offset(pgd_k, address);
 227                 if (!pmd_present(*pmd_k))
 228                         goto no_context;
 229                 set_pmd(pmd, *pmd_k);
 230
 231                 pte_k = pte_offset_kernel(pmd_k, address);
 232                 if (!pte_present(*pte_k))
 233                         goto no_context;
 234                 return;
 235         }
 236 }