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/vt_kern.h>              /* For unblank_screen() */
  20 #include <linux/module.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
  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         int fault;
  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 #ifdef CONFIG_64BIT
  62 # define VMALLOC_FAULT_TARGET no_context
  63 #else
  64 # define VMALLOC_FAULT_TARGET vmalloc_fault
  65 #endif
  66
  67         if (unlikely(address >= VMALLOC_START && address <= VMALLOC_END))
  68                 goto VMALLOC_FAULT_TARGET;
  69 #ifdef MODULE_START
  70         if (unlikely(address >= MODULE_START && address < MODULE_END))
  71                 goto VMALLOC_FAULT_TARGET;
  72 #endif
  73
  74         /*
  75          * If we're in an interrupt or have no user
  76          * context, we must not take the fault..
  77          */
  78         if (in_atomic() || !mm)
  79                 goto bad_area_nosemaphore;
  80
  81         down_read(&mm->mmap_sem);
  82         vma = find_vma(mm, address);
  83         if (!vma)
  84                 goto bad_area;
  85         if (vma->vm_start <= address)
  86                 goto good_area;
  87         if (!(vma->vm_flags & VM_GROWSDOWN))
  88                 goto bad_area;
  89         if (expand_stack(vma, address))
  90                 goto bad_area;
  91 /*
  92  * Ok, we have a good vm_area for this memory access, so
  93  * we can handle it..
  94  */
  95 good_area:
  96         info.si_code = SEGV_ACCERR;
  97
  98         if (write) {
  99                 if (!(vma->vm_flags & VM_WRITE))
 100                         goto bad_area;
 101         } else {
 102                 if (!(vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)))
 103                         goto bad_area;
 104         }
 105
 106         /*
 107          * If for any reason at all we couldn't handle the fault,
 108          * make sure we exit gracefully rather than endlessly redo
 109          * the fault.
 110          */
 111         fault = handle_mm_fault(mm, vma, address, write ? FAULT_FLAG_WRITE : 0);
 112         if (unlikely(fault & VM_FAULT_ERROR)) {
 113                 if (fault & VM_FAULT_OOM)
 114                         goto out_of_memory;
 115                 else if (fault & VM_FAULT_SIGBUS)
 116                         goto do_sigbus;
 117                 BUG();
 118         }
 119         if (fault & VM_FAULT_MAJOR)
 120                 tsk->maj_flt++;
 121         else
 122                 tsk->min_flt++;
 123
 124         up_read(&mm->mmap_sem);
 125         return;
 126
 127 /*
 128  * Something tried to access memory that isn't in our memory map..
 129  * Fix it, but check if it's kernel or user first..
 130  */
 131 bad_area:
 132         up_read(&mm->mmap_sem);
 133
 134 bad_area_nosemaphore:
 135         /* User mode accesses just cause a SIGSEGV */
 136         if (user_mode(regs)) {
 137                 tsk->thread.cp0_badvaddr = address;
 138                 tsk->thread.error_code = write;
 139 #if 0
 140                 printk("do_page_fault() #2: sending SIGSEGV to %s for "
 141                        "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n",
 142                        tsk->comm,
 143                        write ? "write access to" : "read access from",
 144                        field, address,
 145                        field, (unsigned long) regs->cp0_epc,
 146                        field, (unsigned long) regs->regs[31]);
 147 #endif
 148                 info.si_signo = SIGSEGV;
 149                 info.si_errno = 0;
 150                 /* info.si_code has been set above */
 151                 info.si_addr = (void __user *) address;
 152                 force_sig_info(SIGSEGV, &info, tsk);
 153                 return;
 154         }
 155
 156 no_context:
 157         /* Are we prepared to handle this kernel fault?  */
 158         if (fixup_exception(regs)) {
 159                 current->thread.cp0_baduaddr = address;
 160                 return;
 161         }
 162
 163         /*
 164          * Oops. The kernel tried to access some bad page. We'll have to
 165          * terminate things with extreme prejudice.
 166          */
 167         bust_spinlocks(1);
 168
 169         printk(KERN_ALERT "CPU %d Unable to handle kernel paging request at "
 170                "virtual address %0*lx, epc == %0*lx, ra == %0*lx\n",
 171                raw_smp_processor_id(), field, address, field, regs->cp0_epc,
 172                field,  regs->regs[31]);
 173         die("Oops", regs);
 174
 175 out_of_memory:
 176         /*
 177          * We ran out of memory, call the OOM killer, and return the userspace
 178          * (which will retry the fault, or kill us if we got oom-killed).
 179          */
 180         up_read(&mm->mmap_sem);
 181         pagefault_out_of_memory();
 182         return;
 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         else
 191         /*
 192          * Send a sigbus, regardless of whether we were in kernel
 193          * or user mode.
 194          */
 195 #if 0
 196                 printk("do_page_fault() #3: sending SIGBUS to %s for "
 197                        "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n",
 198                        tsk->comm,
 199                        write ? "write access to" : "read access from",
 200                        field, address,
 201                        field, (unsigned long) regs->cp0_epc,
 202                        field, (unsigned long) regs->regs[31]);
 203 #endif
 204         tsk->thread.cp0_badvaddr = address;
 205         info.si_signo = SIGBUS;
 206         info.si_errno = 0;
 207         info.si_code = BUS_ADRERR;
 208         info.si_addr = (void __user *) address;
 209         force_sig_info(SIGBUS, &info, tsk);
 210
 211         return;
 212 #ifndef CONFIG_64BIT
 213 vmalloc_fault:
 214         {
 215                 /*
 216                  * Synchronize this task's top level page-table
 217                  * with the 'reference' page table.
 218                  *
 219                  * Do _not_ use "tsk" here. We might be inside
 220                  * an interrupt in the middle of a task switch..
 221                  */
 222                 int offset = __pgd_offset(address);
 223                 pgd_t *pgd, *pgd_k;
 224                 pud_t *pud, *pud_k;
 225                 pmd_t *pmd, *pmd_k;
 226                 pte_t *pte_k;
 227
 228                 pgd = (pgd_t *) pgd_current[raw_smp_processor_id()] + offset;
 229                 pgd_k = init_mm.pgd + offset;
 230
 231                 if (!pgd_present(*pgd_k))
 232                         goto no_context;
 233                 set_pgd(pgd, *pgd_k);
 234
 235                 pud = pud_offset(pgd, address);
 236                 pud_k = pud_offset(pgd_k, address);
 237                 if (!pud_present(*pud_k))
 238                         goto no_context;
 239
 240                 pmd = pmd_offset(pud, address);
 241                 pmd_k = pmd_offset(pud_k, address);
 242                 if (!pmd_present(*pmd_k))
 243                         goto no_context;
 244                 set_pmd(pmd, *pmd_k);
 245
 246                 pte_k = pte_offset_kernel(pmd_k, address);
 247                 if (!pte_present(*pte_k))
 248                         goto no_context;
 249                 return;
 250         }
 251 #endif
 252 }