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/config.h>
   8 #include <linux/sched.h>
   9 #include <linux/kernel.h>
  10 #include <linux/mm.h>
  11 #include <asm/io.h>
  12
  13 #define __EXTERN_INLINE inline
  14 #include <asm/mmu_context.h>
  15 #include <asm/tlbflush.h>
  16 #undef  __EXTERN_INLINE
  17
  18 #include <linux/signal.h>
  19 #include <linux/errno.h>
  20 #include <linux/string.h>
  21 #include <linux/types.h>
  22 #include <linux/ptrace.h>
  23 #include <linux/mman.h>
  24 #include <linux/smp.h>
  25 #include <linux/smp_lock.h>
  26 #include <linux/interrupt.h>
  27 #include <linux/module.h>
  28
  29 #include <asm/system.h>
  30 #include <asm/uaccess.h>
  31
  32 extern void die_if_kernel(char *,struct pt_regs *,long, unsigned long *);
  33
  34
  35 /*
  36  * Force a new ASN for a task.
  37  */
  38
  39 #ifndef CONFIG_SMP
  40 unsigned long last_asn = ASN_FIRST_VERSION;
  41 #endif
  42
  43 void
  44 __load_new_mm_context(struct mm_struct *next_mm)
  45 {
  46         unsigned long mmc;
  47         struct pcb_struct *pcb;
  48
  49         mmc = __get_new_mm_context(next_mm, smp_processor_id());
  50         next_mm->context[smp_processor_id()] = mmc;
  51
  52         pcb = &current_thread_info()->pcb;
  53         pcb->asn = mmc & HARDWARE_ASN_MASK;
  54         pcb->ptbr = ((unsigned long) next_mm->pgd - IDENT_ADDR) >> PAGE_SHIFT;
  55
  56         __reload_thread(pcb);
  57 }
  58
  59
  60 /*
  61  * This routine handles page faults.  It determines the address,
  62  * and the problem, and then passes it off to handle_mm_fault().
  63  *
  64  * mmcsr:
  65  *      0 = translation not valid
  66  *      1 = access violation
  67  *      2 = fault-on-read
  68  *      3 = fault-on-execute
  69  *      4 = fault-on-write
  70  *
  71  * cause:
  72  *      -1 = instruction fetch
  73  *      0 = load
  74  *      1 = store
  75  *
  76  * Registers $9 through $15 are saved in a block just prior to `regs' and
  77  * are saved and restored around the call to allow exception code to
  78  * modify them.
  79  */
  80
  81 /* Macro for exception fixup code to access integer registers.  */
  82 #define dpf_reg(r)                                                      \
  83         (((unsigned long *)regs)[(r) <= 8 ? (r) : (r) <= 15 ? (r)-16 :  \
  84                                  (r) <= 18 ? (r)+8 : (r)-10])
  85
  86 asmlinkage void
  87 do_page_fault(unsigned long address, unsigned long mmcsr,
  88               long cause, struct pt_regs *regs)
  89 {
  90         struct vm_area_struct * vma;
  91         struct mm_struct *mm = current->mm;
  92         const struct exception_table_entry *fixup;
  93         int fault, si_code = SEGV_MAPERR;
  94         siginfo_t info;
  95
  96         /* As of EV6, a load into $31/$f31 is a prefetch, and never faults
  97            (or is suppressed by the PALcode).  Support that for older CPUs
  98            by ignoring such an instruction.  */
  99         if (cause == 0) {
 100                 unsigned int insn;
 101                 __get_user(insn, (unsigned int __user *)regs->pc);
 102                 if ((insn >> 21 & 0x1f) == 0x1f &&
 103                     /* ldq ldl ldt lds ldg ldf ldwu ldbu */
 104                     (1ul << (insn >> 26) & 0x30f00001400ul)) {
 105                         regs->pc += 4;
 106                         return;
 107                 }
 108         }
 109
 110         /* If we're in an interrupt context, or have no user context,
 111            we must not take the fault.  */
 112         if (!mm || in_interrupt())
 113                 goto no_context;
 114
 115 #ifdef CONFIG_ALPHA_LARGE_VMALLOC
 116         if (address >= TASK_SIZE)
 117                 goto vmalloc_fault;
 118 #endif
 119
 120         down_read(&mm->mmap_sem);
 121         vma = find_vma(mm, address);
 122         if (!vma)
 123                 goto bad_area;
 124         if (vma->vm_start <= address)
 125                 goto good_area;
 126         if (!(vma->vm_flags & VM_GROWSDOWN))
 127                 goto bad_area;
 128         if (expand_stack(vma, address))
 129                 goto bad_area;
 130
 131         /* Ok, we have a good vm_area for this memory access, so
 132            we can handle it.  */
 133  good_area:
 134         si_code = SEGV_ACCERR;
 135         if (cause < 0) {
 136                 if (!(vma->vm_flags & VM_EXEC))
 137                         goto bad_area;
 138         } else if (!cause) {
 139                 /* Allow reads even for write-only mappings */
 140                 if (!(vma->vm_flags & (VM_READ | VM_WRITE)))
 141                         goto bad_area;
 142         } else {
 143                 if (!(vma->vm_flags & VM_WRITE))
 144                         goto bad_area;
 145         }
 146
 147  survive:
 148         /* If for any reason at all we couldn't handle the fault,
 149            make sure we exit gracefully rather than endlessly redo
 150            the fault.  */
 151         fault = handle_mm_fault(mm, vma, address, cause > 0);
 152         up_read(&mm->mmap_sem);
 153
 154         switch (fault) {
 155               case VM_FAULT_MINOR:
 156                 current->min_flt++;
 157                 break;
 158               case VM_FAULT_MAJOR:
 159                 current->maj_flt++;
 160                 break;
 161               case VM_FAULT_SIGBUS:
 162                 goto do_sigbus;
 163               case VM_FAULT_OOM:
 164                 goto out_of_memory;
 165               default:
 166                 BUG();
 167         }
 168         return;
 169
 170         /* Something tried to access memory that isn't in our memory map.
 171            Fix it, but check if it's kernel or user first.  */
 172  bad_area:
 173         up_read(&mm->mmap_sem);
 174
 175         if (user_mode(regs))
 176                 goto do_sigsegv;
 177
 178  no_context:
 179         /* Are we prepared to handle this fault as an exception?  */
 180         if ((fixup = search_exception_tables(regs->pc)) != 0) {
 181                 unsigned long newpc;
 182                 newpc = fixup_exception(dpf_reg, fixup, regs->pc);
 183                 regs->pc = newpc;
 184                 return;
 185         }
 186
 187         /* Oops. The kernel tried to access some bad page. We'll have to
 188            terminate things with extreme prejudice.  */
 189         printk(KERN_ALERT "Unable to handle kernel paging request at "
 190                "virtual address %016lx\n", address);
 191         die_if_kernel("Oops", regs, cause, (unsigned long*)regs - 16);
 192         do_exit(SIGKILL);
 193
 194         /* We ran out of memory, or some other thing happened to us that
 195            made us unable to handle the page fault gracefully.  */
 196  out_of_memory:
 197         if (current->pid == 1) {
 198                 yield();
 199                 down_read(&mm->mmap_sem);
 200                 goto survive;
 201         }
 202         printk(KERN_ALERT "VM: killing process %s(%d)\n",
 203                current->comm, current->pid);
 204         if (!user_mode(regs))
 205                 goto no_context;
 206         do_exit(SIGKILL);
 207
 208  do_sigbus:
 209         /* Send a sigbus, regardless of whether we were in kernel
 210            or user mode.  */
 211         info.si_signo = SIGBUS;
 212         info.si_errno = 0;
 213         info.si_code = BUS_ADRERR;
 214         info.si_addr = (void __user *) address;
 215         force_sig_info(SIGBUS, &info, current);
 216         if (!user_mode(regs))
 217                 goto no_context;
 218         return;
 219
 220  do_sigsegv:
 221         info.si_signo = SIGSEGV;
 222         info.si_errno = 0;
 223         info.si_code = si_code;
 224         info.si_addr = (void __user *) address;
 225         force_sig_info(SIGSEGV, &info, current);
 226         return;
 227
 228 #ifdef CONFIG_ALPHA_LARGE_VMALLOC
 229  vmalloc_fault:
 230         if (user_mode(regs))
 231                 goto do_sigsegv;
 232         else {
 233                 /* Synchronize this task's top level page-table
 234                    with the "reference" page table from init.  */
 235                 long index = pgd_index(address);
 236                 pgd_t *pgd, *pgd_k;
 237
 238                 pgd = current->active_mm->pgd + index;
 239                 pgd_k = swapper_pg_dir + index;
 240                 if (!pgd_present(*pgd) && pgd_present(*pgd_k)) {
 241                         pgd_val(*pgd) = pgd_val(*pgd_k);
 242                         return;
 243                 }
 244                 goto no_context;
 245         }
 246 #endif
 247 }