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