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", raw_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 #ifdef MODULE_START
  64         if (unlikely(address >= MODULE_START && address < MODULE_END))
  65                 goto vmalloc_fault;
  66 #endif
  67
  68         /*
  69          * If we're in an interrupt or have no user
  70          * context, we must not take the fault..
  71          */
  72         if (in_atomic() || !mm)
  73                 goto bad_area_nosemaphore;
  74
  75         down_read(&mm->mmap_sem);
  76         vma = find_vma(mm, address);
  77         if (!vma)
  78                 goto bad_area;
  79         if (vma->vm_start <= address)
  80                 goto good_area;
  81         if (!(vma->vm_flags & VM_GROWSDOWN))
  82                 goto bad_area;
  83         if (expand_stack(vma, address))
  84                 goto bad_area;
  85 /*
  86  * Ok, we have a good vm_area for this memory access, so
  87  * we can handle it..
  88  */
  89 good_area:
  90         info.si_code = SEGV_ACCERR;
  91
  92         if (write) {
  93                 if (!(vma->vm_flags & VM_WRITE))
  94                         goto bad_area;
  95         } else {
  96                 if (!(vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)))
  97                         goto bad_area;
  98         }
  99
 100 survive:
 101         /*
 102          * If for any reason at all we couldn't handle the fault,
 103          * make sure we exit gracefully rather than endlessly redo
 104          * the fault.
 105          */
 106         switch (handle_mm_fault(mm, vma, address, write)) {
 107         case VM_FAULT_MINOR:
 108                 tsk->min_flt++;
 109                 break;
 110         case VM_FAULT_MAJOR:
 111                 tsk->maj_flt++;
 112                 break;
 113         case VM_FAULT_SIGBUS:
 114                 goto do_sigbus;
 115         case VM_FAULT_OOM:
 116                 goto out_of_memory;
 117         default:
 118                 BUG();
 119         }
 120
 121         up_read(&mm->mmap_sem);
 122         return;
 123
 124 /*
 125  * Something tried to access memory that isn't in our memory map..
 126  * Fix it, but check if it's kernel or user first..
 127  */
 128 bad_area:
 129         up_read(&mm->mmap_sem);
 130
 131 bad_area_nosemaphore:
 132         /* User mode accesses just cause a SIGSEGV */
 133         if (user_mode(regs)) {
 134                 tsk->thread.cp0_badvaddr = address;
 135                 tsk->thread.error_code = write;
 136 #if 0
 137                 printk("do_page_fault() #2: sending SIGSEGV to %s for "
 138                        "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n",
 139                        tsk->comm,
 140                        write ? "write access to" : "read access from",
 141                        field, address,
 142                        field, (unsigned long) regs->cp0_epc,
 143                        field, (unsigned long) regs->regs[31]);
 144 #endif
 145                 info.si_signo = SIGSEGV;
 146                 info.si_errno = 0;
 147                 /* info.si_code has been set above */
 148                 info.si_addr = (void __user *) address;
 149                 force_sig_info(SIGSEGV, &info, tsk);
 150                 return;
 151         }
 152
 153 no_context:
 154         /* Are we prepared to handle this kernel fault?  */
 155         if (fixup_exception(regs)) {
 156                 current->thread.cp0_baduaddr = address;
 157                 return;
 158         }
 159
 160         /*
 161          * Oops. The kernel tried to access some bad page. We'll have to
 162          * terminate things with extreme prejudice.
 163          */
 164         bust_spinlocks(1);
 165
 166         printk(KERN_ALERT "CPU %d Unable to handle kernel paging request at "
 167                "virtual address %0*lx, epc == %0*lx, ra == %0*lx\n",
 168                raw_smp_processor_id(), field, address, field, regs->cp0_epc,
 169                field,  regs->regs[31]);
 170         die("Oops", regs);
 171
 172 /*
 173  * We ran out of memory, or some other thing happened to us that made
 174  * us unable to handle the page fault gracefully.
 175  */
 176 out_of_memory:
 177         up_read(&mm->mmap_sem);
 178         if (is_init(tsk)) {
 179                 yield();
 180                 down_read(&mm->mmap_sem);
 181                 goto survive;
 182         }
 183         printk("VM: killing process %s\n", tsk->comm);
 184         if (user_mode(regs))
 185                 do_exit(SIGKILL);
 186         goto no_context;
 187
 188 do_sigbus:
 189         up_read(&mm->mmap_sem);
 190
 191         /* Kernel mode? Handle exceptions or die */
 192         if (!user_mode(regs))
 193                 goto no_context;
 194         else
 195         /*
 196          * Send a sigbus, regardless of whether we were in kernel
 197          * or user mode.
 198          */
 199 #if 0
 200                 printk("do_page_fault() #3: sending SIGBUS to %s for "
 201                        "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n",
 202                        tsk->comm,
 203                        write ? "write access to" : "read access from",
 204                        field, address,
 205                        field, (unsigned long) regs->cp0_epc,
 206                        field, (unsigned long) regs->regs[31]);
 207 #endif
 208         tsk->thread.cp0_badvaddr = address;
 209         info.si_signo = SIGBUS;
 210         info.si_errno = 0;
 211         info.si_code = BUS_ADRERR;
 212         info.si_addr = (void __user *) address;
 213         force_sig_info(SIGBUS, &info, tsk);
 214
 215         return;
 216 vmalloc_fault:
 217         {
 218                 /*
 219                  * Synchronize this task's top level page-table
 220                  * with the 'reference' page table.
 221                  *
 222                  * Do _not_ use "tsk" here. We might be inside
 223                  * an interrupt in the middle of a task switch..
 224                  */
 225                 int offset = __pgd_offset(address);
 226                 pgd_t *pgd, *pgd_k;
 227                 pud_t *pud, *pud_k;
 228                 pmd_t *pmd, *pmd_k;
 229                 pte_t *pte_k;
 230
 231                 pgd = (pgd_t *) pgd_current[raw_smp_processor_id()] + offset;
 232                 pgd_k = init_mm.pgd + offset;
 233
 234                 if (!pgd_present(*pgd_k))
 235                         goto no_context;
 236                 set_pgd(pgd, *pgd_k);
 237
 238                 pud = pud_offset(pgd, address);
 239                 pud_k = pud_offset(pgd_k, address);
 240                 if (!pud_present(*pud_k))
 241                         goto no_context;
 242
 243                 pmd = pmd_offset(pud, address);
 244                 pmd_k = pmd_offset(pud_k, address);
 245                 if (!pmd_present(*pmd_k))
 246                         goto no_context;
 247                 set_pmd(pmd, *pmd_k);
 248
 249                 pte_k = pte_offset_kernel(pmd_k, address);
 250                 if (!pte_present(*pte_k))
 251                         goto no_context;
 252                 return;
 253         }
 254 }