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