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 #include <asm/highmem.h>                /* For VMALLOC_END */
  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 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
  44 #if 0
  45         printk("Cpu%d[%s:%d:%0*lx:%ld:%0*lx]\n", smp_processor_id(),
  46                current->comm, current->pid, field, address, write,
  47                field, regs->cp0_epc);
  48 #endif
  49
  50         info.si_code = SEGV_MAPERR;
  51
  52         /*
  53          * We fault-in kernel-space virtual memory on-demand. The
  54          * 'reference' page table is init_mm.pgd.
  55          *
  56          * NOTE! We MUST NOT take any locks for this case. We may
  57          * be in an interrupt or a critical region, and should
  58          * only copy the information from the master page table,
  59          * nothing more.
  60          */
  61         if (unlikely(address >= VMALLOC_START && address <= VMALLOC_END))
  62                 goto vmalloc_fault;
  63
  64         /*
  65          * If we're in an interrupt or have no user
  66          * context, we must not take the fault..
  67          */
  68         if (in_atomic() || !mm)
  69                 goto bad_area_nosemaphore;
  70
  71         down_read(&mm->mmap_sem);
  72         vma = find_vma(mm, address);
  73         if (!vma)
  74                 goto bad_area;
  75         if (vma->vm_start <= address)
  76                 goto good_area;
  77         if (!(vma->vm_flags & VM_GROWSDOWN))
  78                 goto bad_area;
  79         if (expand_stack(vma, address))
  80                 goto bad_area;
  81 /*
  82  * Ok, we have a good vm_area for this memory access, so
  83  * we can handle it..
  84  */
  85 good_area:
  86         info.si_code = SEGV_ACCERR;
  87
  88         if (write) {
  89                 if (!(vma->vm_flags & VM_WRITE))
  90                         goto bad_area;
  91         } else {
  92                 if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
  93                         goto bad_area;
  94         }
  95
  96 survive:
  97         /*
  98          * If for any reason at all we couldn't handle the fault,
  99          * make sure we exit gracefully rather than endlessly redo
 100          * the fault.
 101          */
 102         switch (handle_mm_fault(mm, vma, address, write)) {
 103         case VM_FAULT_MINOR:
 104                 tsk->min_flt++;
 105                 break;
 106         case VM_FAULT_MAJOR:
 107                 tsk->maj_flt++;
 108                 break;
 109         case VM_FAULT_SIGBUS:
 110                 goto do_sigbus;
 111         case VM_FAULT_OOM:
 112                 goto out_of_memory;
 113         default:
 114                 BUG();
 115         }
 116
 117         up_read(&mm->mmap_sem);
 118         return;
 119
 120 /*
 121  * Something tried to access memory that isn't in our memory map..
 122  * Fix it, but check if it's kernel or user first..
 123  */
 124 bad_area:
 125         up_read(&mm->mmap_sem);
 126
 127 bad_area_nosemaphore:
 128         /* User mode accesses just cause a SIGSEGV */
 129         if (user_mode(regs)) {
 130                 tsk->thread.cp0_badvaddr = address;
 131                 tsk->thread.error_code = write;
 132 #if 0
 133                 printk("do_page_fault() #2: sending SIGSEGV to %s for "
 134                        "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n",
 135                        tsk->comm,
 136                        write ? "write access to" : "read access from",
 137                        field, address,
 138                        field, (unsigned long) regs->cp0_epc,
 139                        field, (unsigned long) regs->regs[31]);
 140 #endif
 141                 info.si_signo = SIGSEGV;
 142                 info.si_errno = 0;
 143                 /* info.si_code has been set above */
 144                 info.si_addr = (void __user *) address;
 145                 force_sig_info(SIGSEGV, &info, tsk);
 146                 return;
 147         }
 148
 149 no_context:
 150         /* Are we prepared to handle this kernel fault?  */
 151         if (fixup_exception(regs)) {
 152                 current->thread.cp0_baduaddr = address;
 153                 return;
 154         }
 155
 156         /*
 157          * Oops. The kernel tried to access some bad page. We'll have to
 158          * terminate things with extreme prejudice.
 159          */
 160
 161         bust_spinlocks(1);
 162
 163         printk(KERN_ALERT "CPU %d Unable to handle kernel paging request at "
 164                "virtual address %0*lx, epc == %0*lx, ra == %0*lx\n",
 165                smp_processor_id(), field, address, field, regs->cp0_epc,
 166                field,  regs->regs[31]);
 167         die("Oops", regs);
 168
 169 /*
 170  * We ran out of memory, or some other thing happened to us that made
 171  * us unable to handle the page fault gracefully.
 172  */
 173 out_of_memory:
 174         up_read(&mm->mmap_sem);
 175         if (tsk->pid == 1) {
 176                 yield();
 177                 down_read(&mm->mmap_sem);
 178                 goto survive;
 179         }
 180         printk("VM: killing process %s\n", tsk->comm);
 181         if (user_mode(regs))
 182                 do_exit(SIGKILL);
 183         goto no_context;
 184
 185 do_sigbus:
 186         up_read(&mm->mmap_sem);
 187
 188         /* Kernel mode? Handle exceptions or die */
 189         if (!user_mode(regs))
 190                 goto no_context;
 191
 192         /*
 193          * Send a sigbus, regardless of whether we were in kernel
 194          * or user mode.
 195          */
 196         tsk->thread.cp0_badvaddr = address;
 197         info.si_signo = SIGBUS;
 198         info.si_errno = 0;
 199         info.si_code = BUS_ADRERR;
 200         info.si_addr = (void __user *) address;
 201         force_sig_info(SIGBUS, &info, tsk);
 202
 203         return;
 204
 205 vmalloc_fault:
 206         {
 207                 /*
 208                  * Synchronize this task's top level page-table
 209                  * with the 'reference' page table.
 210                  *
 211                  * Do _not_ use "tsk" here. We might be inside
 212                  * an interrupt in the middle of a task switch..
 213                  */
 214                 int offset = __pgd_offset(address);
 215                 pgd_t *pgd, *pgd_k;
 216                 pud_t *pud, *pud_k;
 217                 pmd_t *pmd, *pmd_k;
 218                 pte_t *pte_k;
 219
 220                 pgd = (pgd_t *) pgd_current[smp_processor_id()] + offset;
 221                 pgd_k = init_mm.pgd + offset;
 222
 223                 if (!pgd_present(*pgd_k))
 224                         goto no_context;
 225                 set_pgd(pgd, *pgd_k);
 226
 227                 pud = pud_offset(pgd, address);
 228                 pud_k = pud_offset(pgd_k, address);
 229                 if (!pud_present(*pud_k))
 230                         goto no_context;
 231
 232                 pmd = pmd_offset(pud, address);
 233                 pmd_k = pmd_offset(pud_k, address);
 234                 if (!pmd_present(*pmd_k))
 235                         goto no_context;
 236                 set_pmd(pmd, *pmd_k);
 237
 238                 pte_k = pte_offset_kernel(pmd_k, address);
 239                 if (!pte_present(*pte_k))
 240                         goto no_context;
 241                 return;
 242         }
 243 }