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/module.h>
  20 #include <linux/kprobes.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 #include <linux/kdebug.h>
  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 __kprobes 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         int fault;
  44
  45 #if 0
  46         printk("Cpu%d[%s:%d:%0*lx:%ld:%0*lx]\n", raw_smp_processor_id(),
  47                current->comm, current->pid, field, address, write,
  48                field, regs->cp0_epc);
  49 #endif
  50
  51 #ifdef CONFIG_KPROBES
  52         /*
  53          * This is to notify the fault handler of the kprobes.  The
  54          * exception code is redundant as it is also carried in REGS,
  55          * but we pass it anyhow.
  56          */
  57         if (notify_die(DIE_PAGE_FAULT, "page fault", regs, -1,
  58                        (regs->cp0_cause >> 2) & 0x1f, SIGSEGV) == NOTIFY_STOP)
  59                 return;
  60 #endif
  61
  62         info.si_code = SEGV_MAPERR;
  63
  64         /*
  65          * We fault-in kernel-space virtual memory on-demand. The
  66          * 'reference' page table is init_mm.pgd.
  67          *
  68          * NOTE! We MUST NOT take any locks for this case. We may
  69          * be in an interrupt or a critical region, and should
  70          * only copy the information from the master page table,
  71          * nothing more.
  72          */
  73 #ifdef CONFIG_64BIT
  74 # define VMALLOC_FAULT_TARGET no_context
  75 #else
  76 # define VMALLOC_FAULT_TARGET vmalloc_fault
  77 #endif
  78
  79         if (unlikely(address >= VMALLOC_START && address <= VMALLOC_END))
  80                 goto VMALLOC_FAULT_TARGET;
  81 #ifdef MODULE_START
  82         if (unlikely(address >= MODULE_START && address < MODULE_END))
  83                 goto VMALLOC_FAULT_TARGET;
  84 #endif
  85
  86         /*
  87          * If we're in an interrupt or have no user
  88          * context, we must not take the fault..
  89          */
  90         if (in_atomic() || !mm)
  91                 goto bad_area_nosemaphore;
  92
  93         down_read(&mm->mmap_sem);
  94         vma = find_vma(mm, address);
  95         if (!vma)
  96                 goto bad_area;
  97         if (vma->vm_start <= address)
  98                 goto good_area;
  99         if (!(vma->vm_flags & VM_GROWSDOWN))
 100                 goto bad_area;
 101         if (expand_stack(vma, address))
 102                 goto bad_area;
 103 /*
 104  * Ok, we have a good vm_area for this memory access, so
 105  * we can handle it..
 106  */
 107 good_area:
 108         info.si_code = SEGV_ACCERR;
 109
 110         if (write) {
 111                 if (!(vma->vm_flags & VM_WRITE))
 112                         goto bad_area;
 113         } else {
 114                 if (kernel_uses_smartmips_rixi) {
 115                         if (address == regs->cp0_epc && !(vma->vm_flags & VM_EXEC)) {
 116 #if 0
 117                                 pr_notice("Cpu%d[%s:%d:%0*lx:%ld:%0*lx] XI violation\n",
 118                                           raw_smp_processor_id(),
 119                                           current->comm, current->pid,
 120                                           field, address, write,
 121                                           field, regs->cp0_epc);
 122 #endif
 123                                 goto bad_area;
 124                         }
 125                         if (!(vma->vm_flags & VM_READ)) {
 126 #if 0
 127                                 pr_notice("Cpu%d[%s:%d:%0*lx:%ld:%0*lx] RI violation\n",
 128                                           raw_smp_processor_id(),
 129                                           current->comm, current->pid,
 130                                           field, address, write,
 131                                           field, regs->cp0_epc);
 132 #endif
 133                                 goto bad_area;
 134                         }
 135                 } else {
 136                         if (!(vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)))
 137                                 goto bad_area;
 138                 }
 139         }
 140
 141         /*
 142          * If for any reason at all we couldn't handle the fault,
 143          * make sure we exit gracefully rather than endlessly redo
 144          * the fault.
 145          */
 146         fault = handle_mm_fault(mm, vma, address, write ? FAULT_FLAG_WRITE : 0);
 147         if (unlikely(fault & VM_FAULT_ERROR)) {
 148                 if (fault & VM_FAULT_OOM)
 149                         goto out_of_memory;
 150                 else if (fault & VM_FAULT_SIGBUS)
 151                         goto do_sigbus;
 152                 BUG();
 153         }
 154         if (fault & VM_FAULT_MAJOR)
 155                 tsk->maj_flt++;
 156         else
 157                 tsk->min_flt++;
 158
 159         up_read(&mm->mmap_sem);
 160         return;
 161
 162 /*
 163  * Something tried to access memory that isn't in our memory map..
 164  * Fix it, but check if it's kernel or user first..
 165  */
 166 bad_area:
 167         up_read(&mm->mmap_sem);
 168
 169 bad_area_nosemaphore:
 170         /* User mode accesses just cause a SIGSEGV */
 171         if (user_mode(regs)) {
 172                 tsk->thread.cp0_badvaddr = address;
 173                 tsk->thread.error_code = write;
 174 #if 0
 175                 printk("do_page_fault() #2: sending SIGSEGV to %s for "
 176                        "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n",
 177                        tsk->comm,
 178                        write ? "write access to" : "read access from",
 179                        field, address,
 180                        field, (unsigned long) regs->cp0_epc,
 181                        field, (unsigned long) regs->regs[31]);
 182 #endif
 183                 info.si_signo = SIGSEGV;
 184                 info.si_errno = 0;
 185                 /* info.si_code has been set above */
 186                 info.si_addr = (void __user *) address;
 187                 force_sig_info(SIGSEGV, &info, tsk);
 188                 return;
 189         }
 190
 191 no_context:
 192         /* Are we prepared to handle this kernel fault?  */
 193         if (fixup_exception(regs)) {
 194                 current->thread.cp0_baduaddr = address;
 195                 return;
 196         }
 197
 198         /*
 199          * Oops. The kernel tried to access some bad page. We'll have to
 200          * terminate things with extreme prejudice.
 201          */
 202         bust_spinlocks(1);
 203
 204         printk(KERN_ALERT "CPU %d Unable to handle kernel paging request at "
 205                "virtual address %0*lx, epc == %0*lx, ra == %0*lx\n",
 206                raw_smp_processor_id(), field, address, field, regs->cp0_epc,
 207                field,  regs->regs[31]);
 208         die("Oops", regs);
 209
 210 out_of_memory:
 211         /*
 212          * We ran out of memory, call the OOM killer, and return the userspace
 213          * (which will retry the fault, or kill us if we got oom-killed).
 214          */
 215         up_read(&mm->mmap_sem);
 216         pagefault_out_of_memory();
 217         return;
 218
 219 do_sigbus:
 220         up_read(&mm->mmap_sem);
 221
 222         /* Kernel mode? Handle exceptions or die */
 223         if (!user_mode(regs))
 224                 goto no_context;
 225         else
 226         /*
 227          * Send a sigbus, regardless of whether we were in kernel
 228          * or user mode.
 229          */
 230 #if 0
 231                 printk("do_page_fault() #3: sending SIGBUS to %s for "
 232                        "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n",
 233                        tsk->comm,
 234                        write ? "write access to" : "read access from",
 235                        field, address,
 236                        field, (unsigned long) regs->cp0_epc,
 237                        field, (unsigned long) regs->regs[31]);
 238 #endif
 239         tsk->thread.cp0_badvaddr = address;
 240         info.si_signo = SIGBUS;
 241         info.si_errno = 0;
 242         info.si_code = BUS_ADRERR;
 243         info.si_addr = (void __user *) address;
 244         force_sig_info(SIGBUS, &info, tsk);
 245
 246         return;
 247 #ifndef CONFIG_64BIT
 248 vmalloc_fault:
 249         {
 250                 /*
 251                  * Synchronize this task's top level page-table
 252                  * with the 'reference' page table.
 253                  *
 254                  * Do _not_ use "tsk" here. We might be inside
 255                  * an interrupt in the middle of a task switch..
 256                  */
 257                 int offset = __pgd_offset(address);
 258                 pgd_t *pgd, *pgd_k;
 259                 pud_t *pud, *pud_k;
 260                 pmd_t *pmd, *pmd_k;
 261                 pte_t *pte_k;
 262
 263                 pgd = (pgd_t *) pgd_current[raw_smp_processor_id()] + offset;
 264                 pgd_k = init_mm.pgd + offset;
 265
 266                 if (!pgd_present(*pgd_k))
 267                         goto no_context;
 268                 set_pgd(pgd, *pgd_k);
 269
 270                 pud = pud_offset(pgd, address);
 271                 pud_k = pud_offset(pgd_k, address);
 272                 if (!pud_present(*pud_k))
 273                         goto no_context;
 274
 275                 pmd = pmd_offset(pud, address);
 276                 pmd_k = pmd_offset(pud_k, address);
 277                 if (!pmd_present(*pmd_k))
 278                         goto no_context;
 279                 set_pmd(pmd, *pmd_k);
 280
 281                 pte_k = pte_offset_kernel(pmd_k, address);
 282                 if (!pte_present(*pte_k))
 283                         goto no_context;
 284                 return;
 285         }
 286 #endif
 287 }