arch/alpha/mm/fault.c

   1 /*
   2  *  linux/arch/alpha/mm/fault.c
   3  *
   4  *  Copyright (C) 1995  Linus Torvalds
   5  */
   6
   7 #include <linux/sched.h>
   8 #include <linux/kernel.h>
   9 #include <linux/mm.h>
  10 #include <asm/io.h>
  11
  12 #define __EXTERN_INLINE inline
  13 #include <asm/mmu_context.h>
  14 #include <asm/tlbflush.h>
  15 #undef  __EXTERN_INLINE
  16
  17 #include <linux/signal.h>
  18 #include <linux/errno.h>
  19 #include <linux/string.h>
  20 #include <linux/types.h>
  21 #include <linux/ptrace.h>
  22 #include <linux/mman.h>
  23 #include <linux/smp.h>
  24 #include <linux/interrupt.h>
  25 #include <linux/module.h>
  26
  27 #include <asm/system.h>
  28 #include <asm/uaccess.h>
  29
  30 extern void die_if_kernel(char *,struct pt_regs *,long, unsigned long *);
  31
  32
  33 /*
  34  * Force a new ASN for a task.
  35  */
  36
  37 #ifndef CONFIG_SMP
  38 unsigned long last_asn = ASN_FIRST_VERSION;
  39 #endif
  40
  41 void
  42 __load_new_mm_context(struct mm_struct *next_mm)
  43 {
  44         unsigned long mmc;
  45         struct pcb_struct *pcb;
  46
  47         mmc = __get_new_mm_context(next_mm, smp_processor_id());
  48         next_mm->context[smp_processor_id()] = mmc;
  49
  50         pcb = &current_thread_info()->pcb;
  51         pcb->asn = mmc & HARDWARE_ASN_MASK;
  52         pcb->ptbr = ((unsigned long) next_mm->pgd - IDENT_ADDR) >> PAGE_SHIFT;
  53
  54         __reload_thread(pcb);
  55 }
  56
  57
  58 /*
  59  * This routine handles page faults.  It determines the address,
  60  * and the problem, and then passes it off to handle_mm_fault().
  61  *
  62  * mmcsr:
  63  *      0 = translation not valid
  64  *      1 = access violation
  65  *      2 = fault-on-read
  66  *      3 = fault-on-execute
  67  *      4 = fault-on-write
  68  *
  69  * cause:
  70  *      -1 = instruction fetch
  71  *      0 = load
  72  *      1 = store
  73  *
  74  * Registers $9 through $15 are saved in a block just prior to `regs' and
  75  * are saved and restored around the call to allow exception code to
  76  * modify them.
  77  */
  78
  79 /* Macro for exception fixup code to access integer registers.  */
  80 #define dpf_reg(r)                                                      \
  81         (((unsigned long *)regs)[(r) <= 8 ? (r) : (r) <= 15 ? (r)-16 :  \
  82                                  (r) <= 18 ? (r)+8 : (r)-10])
  83
  84 asmlinkage void
  85 do_page_fault(unsigned long address, unsigned long mmcsr,
  86               long cause, struct pt_regs *regs)
  87 {
  88         struct vm_area_struct * vma;
  89         struct mm_struct *mm = current->mm;
  90         const struct exception_table_entry *fixup;
  91         int fault, si_code = SEGV_MAPERR;
  92         siginfo_t info;
  93
  94         /* As of EV6, a load into $31/$f31 is a prefetch, and never faults
  95            (or is suppressed by the PALcode).  Support that for older CPUs
  96            by ignoring such an instruction.  */
  97         if (cause == 0) {
  98                 unsigned int insn;
  99                 __get_user(insn, (unsigned int __user *)regs->pc);
 100                 if ((insn >> 21 & 0x1f) == 0x1f &&
 101                     /* ldq ldl ldt lds ldg ldf ldwu ldbu */
 102                     (1ul << (insn >> 26) & 0x30f00001400ul)) {
 103                         regs->pc += 4;
 104                         return;
 105                 }
 106         }
 107
 108         /* If we're in an interrupt context, or have no user context,
 109            we must not take the fault.  */
 110         if (!mm || in_atomic())
 111                 goto no_context;
 112
 113 #ifdef CONFIG_ALPHA_LARGE_VMALLOC
 114         if (address >= TASK_SIZE)
 115                 goto vmalloc_fault;
 116 #endif
 117
 118         down_read(&mm->mmap_sem);
 119         vma = find_vma(mm, address);
 120         if (!vma)
 121                 goto bad_area;
 122         if (vma->vm_start <= address)
 123                 goto good_area;
 124         if (!(vma->vm_flags & VM_GROWSDOWN))
 125                 goto bad_area;
 126         if (expand_stack(vma, address))
 127                 goto bad_area;
 128
 129         /* Ok, we have a good vm_area for this memory access, so
 130            we can handle it.  */
 131  good_area:
 132         si_code = SEGV_ACCERR;
 133         if (cause < 0) {
 134                 if (!(vma->vm_flags & VM_EXEC))
 135                         goto bad_area;
 136         } else if (!cause) {
 137                 /* Allow reads even for write-only mappings */
 138                 if (!(vma->vm_flags & (VM_READ | VM_WRITE)))
 139                         goto bad_area;
 140         } else {
 141                 if (!(vma->vm_flags & VM_WRITE))
 142                         goto bad_area;
 143         }
 144
 145  survive:
 146         /* If for any reason at all we couldn't handle the fault,
 147            make sure we exit gracefully rather than endlessly redo
 148            the fault.  */
 149         fault = handle_mm_fault(mm, vma, address, cause > 0 ? FAULT_FLAG_WRITE : 0);
 150         up_read(&mm->mmap_sem);
 151         if (unlikely(fault & VM_FAULT_ERROR)) {
 152                 if (fault & VM_FAULT_OOM)
 153                         goto out_of_memory;
 154                 else if (fault & VM_FAULT_SIGBUS)
 155                         goto do_sigbus;
 156                 BUG();
 157         }
 158         if (fault & VM_FAULT_MAJOR)
 159                 current->maj_flt++;
 160         else
 161                 current->min_flt++;
 162         return;
 163
 164         /* Something tried to access memory that isn't in our memory map.
 165            Fix it, but check if it's kernel or user first.  */
 166  bad_area:
 167         up_read(&mm->mmap_sem);
 168
 169         if (user_mode(regs))
 170                 goto do_sigsegv;
 171
 172  no_context:
 173         /* Are we prepared to handle this fault as an exception?  */
 174         if ((fixup = search_exception_tables(regs->pc)) != 0) {
 175                 unsigned long newpc;
 176                 newpc = fixup_exception(dpf_reg, fixup, regs->pc);
 177                 regs->pc = newpc;
 178                 return;
 179         }
 180
 181         /* Oops. The kernel tried to access some bad page. We'll have to
 182            terminate things with extreme prejudice.  */
 183         printk(KERN_ALERT "Unable to handle kernel paging request at "
 184                "virtual address %016lx\n", address);
 185         die_if_kernel("Oops", regs, cause, (unsigned long*)regs - 16);
 186         do_exit(SIGKILL);
 187
 188         /* We ran out of memory, or some other thing happened to us that
 189            made us unable to handle the page fault gracefully.  */
 190  out_of_memory:
 191         if (is_global_init(current)) {
 192                 yield();
 193                 down_read(&mm->mmap_sem);
 194                 goto survive;
 195         }
 196         printk(KERN_ALERT "VM: killing process %s(%d)\n",
 197                current->comm, task_pid_nr(current));
 198         if (!user_mode(regs))
 199                 goto no_context;
 200         do_group_exit(SIGKILL);
 201
 202  do_sigbus:
 203         /* Send a sigbus, regardless of whether we were in kernel
 204            or user mode.  */
 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, current);
 210         if (!user_mode(regs))
 211                 goto no_context;
 212         return;
 213
 214  do_sigsegv:
 215         info.si_signo = SIGSEGV;
 216         info.si_errno = 0;
 217         info.si_code = si_code;
 218         info.si_addr = (void __user *) address;
 219         force_sig_info(SIGSEGV, &info, current);
 220         return;
 221
 222 #ifdef CONFIG_ALPHA_LARGE_VMALLOC
 223  vmalloc_fault:
 224         if (user_mode(regs))
 225                 goto do_sigsegv;
 226         else {
 227                 /* Synchronize this task's top level page-table
 228                    with the "reference" page table from init.  */
 229                 long index = pgd_index(address);
 230                 pgd_t *pgd, *pgd_k;
 231
 232                 pgd = current->active_mm->pgd + index;
 233                 pgd_k = swapper_pg_dir + index;
 234                 if (!pgd_present(*pgd) && pgd_present(*pgd_k)) {
 235                         pgd_val(*pgd) = pgd_val(*pgd_k);
 236                         return;
 237                 }
 238                 goto no_context;
 239         }
 240 #endif
 241 }