arch/ia64/mm/fault.c

   1 /*
   2  * MMU fault handling support.
   3  *
   4  * Copyright (C) 1998-2002 Hewlett-Packard Co
   5  *      David Mosberger-Tang <davidm@hpl.hp.com>
   6  */
   7 #include <linux/sched.h>
   8 #include <linux/kernel.h>
   9 #include <linux/mm.h>
  10 #include <linux/smp_lock.h>
  11 #include <linux/interrupt.h>
  12 #include <linux/kprobes.h>
  13 #include <linux/kdebug.h>
  14
  15 #include <asm/pgtable.h>
  16 #include <asm/processor.h>
  17 #include <asm/system.h>
  18 #include <asm/uaccess.h>
  19
  20 extern void die (char *, struct pt_regs *, long);
  21
  22 #ifdef CONFIG_KPROBES
  23 ATOMIC_NOTIFIER_HEAD(notify_page_fault_chain);
  24
  25 /* Hook to register for page fault notifications */
  26 int register_page_fault_notifier(struct notifier_block *nb)
  27 {
  28         return atomic_notifier_chain_register(&notify_page_fault_chain, nb);
  29 }
  30
  31 int unregister_page_fault_notifier(struct notifier_block *nb)
  32 {
  33         return atomic_notifier_chain_unregister(&notify_page_fault_chain, nb);
  34 }
  35
  36 static inline int notify_page_fault(enum die_val val, const char *str,
  37                         struct pt_regs *regs, long err, int trap, int sig)
  38 {
  39         struct die_args args = {
  40                 .regs = regs,
  41                 .str = str,
  42                 .err = err,
  43                 .trapnr = trap,
  44                 .signr = sig
  45         };
  46         return atomic_notifier_call_chain(&notify_page_fault_chain, val, &args);
  47 }
  48 #else
  49 static inline int notify_page_fault(enum die_val val, const char *str,
  50                         struct pt_regs *regs, long err, int trap, int sig)
  51 {
  52         return NOTIFY_DONE;
  53 }
  54 #endif
  55
  56 /*
  57  * Return TRUE if ADDRESS points at a page in the kernel's mapped segment
  58  * (inside region 5, on ia64) and that page is present.
  59  */
  60 static int
  61 mapped_kernel_page_is_present (unsigned long address)
  62 {
  63         pgd_t *pgd;
  64         pud_t *pud;
  65         pmd_t *pmd;
  66         pte_t *ptep, pte;
  67
  68         pgd = pgd_offset_k(address);
  69         if (pgd_none(*pgd) || pgd_bad(*pgd))
  70                 return 0;
  71
  72         pud = pud_offset(pgd, address);
  73         if (pud_none(*pud) || pud_bad(*pud))
  74                 return 0;
  75
  76         pmd = pmd_offset(pud, address);
  77         if (pmd_none(*pmd) || pmd_bad(*pmd))
  78                 return 0;
  79
  80         ptep = pte_offset_kernel(pmd, address);
  81         if (!ptep)
  82                 return 0;
  83
  84         pte = *ptep;
  85         return pte_present(pte);
  86 }
  87
  88 void __kprobes
  89 ia64_do_page_fault (unsigned long address, unsigned long isr, struct pt_regs *regs)
  90 {
  91         int signal = SIGSEGV, code = SEGV_MAPERR;
  92         struct vm_area_struct *vma, *prev_vma;
  93         struct mm_struct *mm = current->mm;
  94         struct siginfo si;
  95         unsigned long mask;
  96
  97         /* mmap_sem is performance critical.... */
  98         prefetchw(&mm->mmap_sem);
  99
 100         /*
 101          * If we're in an interrupt or have no user context, we must not take the fault..
 102          */
 103         if (in_atomic() || !mm)
 104                 goto no_context;
 105
 106 #ifdef CONFIG_VIRTUAL_MEM_MAP
 107         /*
 108          * If fault is in region 5 and we are in the kernel, we may already
 109          * have the mmap_sem (pfn_valid macro is called during mmap). There
 110          * is no vma for region 5 addr's anyway, so skip getting the semaphore
 111          * and go directly to the exception handling code.
 112          */
 113
 114         if ((REGION_NUMBER(address) == 5) && !user_mode(regs))
 115                 goto bad_area_no_up;
 116 #endif
 117
 118         /*
 119          * This is to handle the kprobes on user space access instructions
 120          */
 121         if (notify_page_fault(DIE_PAGE_FAULT, "page fault", regs, code, TRAP_BRKPT,
 122                                         SIGSEGV) == NOTIFY_STOP)
 123                 return;
 124
 125         down_read(&mm->mmap_sem);
 126
 127         vma = find_vma_prev(mm, address, &prev_vma);
 128         if (!vma)
 129                 goto bad_area;
 130
 131         /* find_vma_prev() returns vma such that address < vma->vm_end or NULL */
 132         if (address < vma->vm_start)
 133                 goto check_expansion;
 134
 135   good_area:
 136         code = SEGV_ACCERR;
 137
 138         /* OK, we've got a good vm_area for this memory area.  Check the access permissions: */
 139
 140 #       define VM_READ_BIT      0
 141 #       define VM_WRITE_BIT     1
 142 #       define VM_EXEC_BIT      2
 143
 144 #       if (((1 << VM_READ_BIT) != VM_READ || (1 << VM_WRITE_BIT) != VM_WRITE) \
 145             || (1 << VM_EXEC_BIT) != VM_EXEC)
 146 #               error File is out of sync with <linux/mm.h>.  Please update.
 147 #       endif
 148
 149         if (((isr >> IA64_ISR_R_BIT) & 1UL) && (!(vma->vm_flags & (VM_READ | VM_WRITE))))
 150                 goto bad_area;
 151
 152         mask = (  (((isr >> IA64_ISR_X_BIT) & 1UL) << VM_EXEC_BIT)
 153                 | (((isr >> IA64_ISR_W_BIT) & 1UL) << VM_WRITE_BIT));
 154
 155         if ((vma->vm_flags & mask) != mask)
 156                 goto bad_area;
 157
 158   survive:
 159         /*
 160          * If for any reason at all we couldn't handle the fault, make
 161          * sure we exit gracefully rather than endlessly redo the
 162          * fault.
 163          */
 164         switch (handle_mm_fault(mm, vma, address, (mask & VM_WRITE) != 0)) {
 165               case VM_FAULT_MINOR:
 166                 ++current->min_flt;
 167                 break;
 168               case VM_FAULT_MAJOR:
 169                 ++current->maj_flt;
 170                 break;
 171               case VM_FAULT_SIGBUS:
 172                 /*
 173                  * We ran out of memory, or some other thing happened
 174                  * to us that made us unable to handle the page fault
 175                  * gracefully.
 176                  */
 177                 signal = SIGBUS;
 178                 goto bad_area;
 179               case VM_FAULT_OOM:
 180                 goto out_of_memory;
 181               default:
 182                 BUG();
 183         }
 184         up_read(&mm->mmap_sem);
 185         return;
 186
 187   check_expansion:
 188         if (!(prev_vma && (prev_vma->vm_flags & VM_GROWSUP) && (address == prev_vma->vm_end))) {
 189                 if (!(vma->vm_flags & VM_GROWSDOWN))
 190                         goto bad_area;
 191                 if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start)
 192                     || REGION_OFFSET(address) >= RGN_MAP_LIMIT)
 193                         goto bad_area;
 194                 if (expand_stack(vma, address))
 195                         goto bad_area;
 196         } else {
 197                 vma = prev_vma;
 198                 if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start)
 199                     || REGION_OFFSET(address) >= RGN_MAP_LIMIT)
 200                         goto bad_area;
 201                 /*
 202                  * Since the register backing store is accessed sequentially,
 203                  * we disallow growing it by more than a page at a time.
 204                  */
 205                 if (address > vma->vm_end + PAGE_SIZE - sizeof(long))
 206                         goto bad_area;
 207                 if (expand_upwards(vma, address))
 208                         goto bad_area;
 209         }
 210         goto good_area;
 211
 212   bad_area:
 213         up_read(&mm->mmap_sem);
 214 #ifdef CONFIG_VIRTUAL_MEM_MAP
 215   bad_area_no_up:
 216 #endif
 217         if ((isr & IA64_ISR_SP)
 218             || ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH))
 219         {
 220                 /*
 221                  * This fault was due to a speculative load or lfetch.fault, set the "ed"
 222                  * bit in the psr to ensure forward progress.  (Target register will get a
 223                  * NaT for ld.s, lfetch will be canceled.)
 224                  */
 225                 ia64_psr(regs)->ed = 1;
 226                 return;
 227         }
 228         if (user_mode(regs)) {
 229                 si.si_signo = signal;
 230                 si.si_errno = 0;
 231                 si.si_code = code;
 232                 si.si_addr = (void __user *) address;
 233                 si.si_isr = isr;
 234                 si.si_flags = __ISR_VALID;
 235                 force_sig_info(signal, &si, current);
 236                 return;
 237         }
 238
 239   no_context:
 240         if ((isr & IA64_ISR_SP)
 241             || ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH))
 242         {
 243                 /*
 244                  * This fault was due to a speculative load or lfetch.fault, set the "ed"
 245                  * bit in the psr to ensure forward progress.  (Target register will get a
 246                  * NaT for ld.s, lfetch will be canceled.)
 247                  */
 248                 ia64_psr(regs)->ed = 1;
 249                 return;
 250         }
 251
 252         /*
 253          * Since we have no vma's for region 5, we might get here even if the address is
 254          * valid, due to the VHPT walker inserting a non present translation that becomes
 255          * stale. If that happens, the non present fault handler already purged the stale
 256          * translation, which fixed the problem. So, we check to see if the translation is
 257          * valid, and return if it is.
 258          */
 259         if (REGION_NUMBER(address) == 5 && mapped_kernel_page_is_present(address))
 260                 return;
 261
 262         if (ia64_done_with_exception(regs))
 263                 return;
 264
 265         /*
 266          * Oops. The kernel tried to access some bad page. We'll have to terminate things
 267          * with extreme prejudice.
 268          */
 269         bust_spinlocks(1);
 270
 271         if (address < PAGE_SIZE)
 272                 printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference (address %016lx)\n", address);
 273         else
 274                 printk(KERN_ALERT "Unable to handle kernel paging request at "
 275                        "virtual address %016lx\n", address);
 276         die("Oops", regs, isr);
 277         bust_spinlocks(0);
 278         do_exit(SIGKILL);
 279         return;
 280
 281   out_of_memory:
 282         up_read(&mm->mmap_sem);
 283         if (is_init(current)) {
 284                 yield();
 285                 down_read(&mm->mmap_sem);
 286                 goto survive;
 287         }
 288         printk(KERN_CRIT "VM: killing process %s\n", current->comm);
 289         if (user_mode(regs))
 290                 do_exit(SIGKILL);
 291         goto no_context;
 292 }