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/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
  19 extern int die(char *, struct pt_regs *, long);
  20
  21 #ifdef CONFIG_KPROBES
  22 static 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
  37 static 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  */
  47 static int
  48 mapped_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
  75 void __kprobes
  76 ia64_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) ? FAULT_FLAG_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 }