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