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         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         fault = handle_mm_fault(mm, vma, address, write);
 107         if (unlikely(fault & VM_FAULT_ERROR)) {
 108                 if (fault & VM_FAULT_OOM)
 109                         goto out_of_memory;
 110                 else if (fault & VM_FAULT_SIGBUS)
 111                         goto do_sigbus;
 112                 BUG();
 113         }
 114         if (fault & VM_FAULT_MAJOR)
 115                 tsk->maj_flt++;
 116         else
 117                 tsk->min_flt++;
 118
 119         up_read(&mm->mmap_sem);
 120         return;
 121
 122 /*
 123  * Something tried to access memory that isn't in our memory map..
 124  * Fix it, but check if it's kernel or user first..
 125  */
 126 bad_area:
 127         up_read(&mm->mmap_sem);
 128
 129 bad_area_nosemaphore:
 130         /* User mode accesses just cause a SIGSEGV */
 131         if (user_mode(regs)) {
 132                 tsk->thread.cp0_badvaddr = address;
 133                 tsk->thread.error_code = write;
 134 #if 0
 135                 printk("do_page_fault() #2: sending SIGSEGV to %s for "
 136                        "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n",
 137                        tsk->comm,
 138                        write ? "write access to" : "read access from",
 139                        field, address,
 140                        field, (unsigned long) regs->cp0_epc,
 141                        field, (unsigned long) regs->regs[31]);
 142 #endif
 143                 info.si_signo = SIGSEGV;
 144                 info.si_errno = 0;
 145                 /* info.si_code has been set above */
 146                 info.si_addr = (void __user *) address;
 147                 force_sig_info(SIGSEGV, &info, tsk);
 148                 return;
 149         }
 150
 151 no_context:
 152         /* Are we prepared to handle this kernel fault?  */
 153         if (fixup_exception(regs)) {
 154                 current->thread.cp0_baduaddr = address;
 155                 return;
 156         }
 157
 158         /*
 159          * Oops. The kernel tried to access some bad page. We'll have to
 160          * terminate things with extreme prejudice.
 161          */
 162         bust_spinlocks(1);
 163
 164         printk(KERN_ALERT "CPU %d Unable to handle kernel paging request at "
 165                "virtual address %0*lx, epc == %0*lx, ra == %0*lx\n",
 166                raw_smp_processor_id(), field, address, field, regs->cp0_epc,
 167                field,  regs->regs[31]);
 168         die("Oops", regs);
 169
 170 /*
 171  * We ran out of memory, or some other thing happened to us that made
 172  * us unable to handle the page fault gracefully.
 173  */
 174 out_of_memory:
 175         up_read(&mm->mmap_sem);
 176         if (is_global_init(tsk)) {
 177                 yield();
 178                 down_read(&mm->mmap_sem);
 179                 goto survive;
 180         }
 181         printk("VM: killing process %s\n", tsk->comm);
 182         if (user_mode(regs))
 183                 do_group_exit(SIGKILL);
 184         goto no_context;
 185
 186 do_sigbus:
 187         up_read(&mm->mmap_sem);
 188
 189         /* Kernel mode? Handle exceptions or die */
 190         if (!user_mode(regs))
 191                 goto no_context;
 192         else
 193         /*
 194          * Send a sigbus, regardless of whether we were in kernel
 195          * or user mode.
 196          */
 197 #if 0
 198                 printk("do_page_fault() #3: sending SIGBUS to %s for "
 199                        "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n",
 200                        tsk->comm,
 201                        write ? "write access to" : "read access from",
 202                        field, address,
 203                        field, (unsigned long) regs->cp0_epc,
 204                        field, (unsigned long) regs->regs[31]);
 205 #endif
 206         tsk->thread.cp0_badvaddr = address;
 207         info.si_signo = SIGBUS;
 208         info.si_errno = 0;
 209         info.si_code = BUS_ADRERR;
 210         info.si_addr = (void __user *) address;
 211         force_sig_info(SIGBUS, &info, tsk);
 212
 213         return;
 214 vmalloc_fault:
 215         {
 216                 /*
 217                  * Synchronize this task's top level page-table
 218                  * with the 'reference' page table.
 219                  *
 220                  * Do _not_ use "tsk" here. We might be inside
 221                  * an interrupt in the middle of a task switch..
 222                  */
 223                 int offset = __pgd_offset(address);
 224                 pgd_t *pgd, *pgd_k;
 225                 pud_t *pud, *pud_k;
 226                 pmd_t *pmd, *pmd_k;
 227                 pte_t *pte_k;
 228
 229                 pgd = (pgd_t *) pgd_current[raw_smp_processor_id()] + offset;
 230                 pgd_k = init_mm.pgd + offset;
 231
 232                 if (!pgd_present(*pgd_k))
 233                         goto no_context;
 234                 set_pgd(pgd, *pgd_k);
 235
 236                 pud = pud_offset(pgd, address);
 237                 pud_k = pud_offset(pgd_k, address);
 238                 if (!pud_present(*pud_k))
 239                         goto no_context;
 240
 241                 pmd = pmd_offset(pud, address);
 242                 pmd_k = pmd_offset(pud_k, address);
 243                 if (!pmd_present(*pmd_k))
 244                         goto no_context;
 245                 set_pmd(pmd, *pmd_k);
 246
 247                 pte_k = pte_offset_kernel(pmd_k, address);
 248                 if (!pte_present(*pte_k))
 249                         goto no_context;
 250                 return;
 251         }
 252 }