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 void 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() && kprobes_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
  84         /* mmap_sem is performance critical.... */
  85         prefetchw(&mm->mmap_sem);
  86
  87         /*
  88          * If we're in an interrupt or have no user context, we must not take the fault..
  89          */
  90         if (in_atomic() || !mm)
  91                 goto no_context;
  92
  93 #ifdef CONFIG_VIRTUAL_MEM_MAP
  94         /*
  95          * If fault is in region 5 and we are in the kernel, we may already
  96          * have the mmap_sem (pfn_valid macro is called during mmap). There
  97          * is no vma for region 5 addr's anyway, so skip getting the semaphore
  98          * and go directly to the exception handling code.
  99          */
 100
 101         if ((REGION_NUMBER(address) == 5) && !user_mode(regs))
 102                 goto bad_area_no_up;
 103 #endif
 104
 105         /*
 106          * This is to handle the kprobes on user space access instructions
 107          */
 108         if (notify_page_fault(regs, TRAP_BRKPT))
 109                 return;
 110
 111         down_read(&mm->mmap_sem);
 112
 113         vma = find_vma_prev(mm, address, &prev_vma);
 114         if (!vma)
 115                 goto bad_area;
 116
 117         /* find_vma_prev() returns vma such that address < vma->vm_end or NULL */
 118         if (address < vma->vm_start)
 119                 goto check_expansion;
 120
 121   good_area:
 122         code = SEGV_ACCERR;
 123
 124         /* OK, we've got a good vm_area for this memory area.  Check the access permissions: */
 125
 126 #       define VM_READ_BIT      0
 127 #       define VM_WRITE_BIT     1
 128 #       define VM_EXEC_BIT      2
 129
 130 #       if (((1 << VM_READ_BIT) != VM_READ || (1 << VM_WRITE_BIT) != VM_WRITE) \
 131             || (1 << VM_EXEC_BIT) != VM_EXEC)
 132 #               error File is out of sync with <linux/mm.h>.  Please update.
 133 #       endif
 134
 135         if (((isr >> IA64_ISR_R_BIT) & 1UL) && (!(vma->vm_flags & (VM_READ | VM_WRITE))))
 136                 goto bad_area;
 137
 138         mask = (  (((isr >> IA64_ISR_X_BIT) & 1UL) << VM_EXEC_BIT)
 139                 | (((isr >> IA64_ISR_W_BIT) & 1UL) << VM_WRITE_BIT));
 140
 141         if ((vma->vm_flags & mask) != mask)
 142                 goto bad_area;
 143
 144   survive:
 145         /*
 146          * If for any reason at all we couldn't handle the fault, make
 147          * sure we exit gracefully rather than endlessly redo the
 148          * fault.
 149          */
 150         switch (handle_mm_fault(mm, vma, address, (mask & VM_WRITE) != 0)) {
 151               case VM_FAULT_MINOR:
 152                 ++current->min_flt;
 153                 break;
 154               case VM_FAULT_MAJOR:
 155                 ++current->maj_flt;
 156                 break;
 157               case VM_FAULT_SIGBUS:
 158                 /*
 159                  * We ran out of memory, or some other thing happened
 160                  * to us that made us unable to handle the page fault
 161                  * gracefully.
 162                  */
 163                 signal = SIGBUS;
 164                 goto bad_area;
 165               case VM_FAULT_OOM:
 166                 goto out_of_memory;
 167               default:
 168                 BUG();
 169         }
 170         up_read(&mm->mmap_sem);
 171         return;
 172
 173   check_expansion:
 174         if (!(prev_vma && (prev_vma->vm_flags & VM_GROWSUP) && (address == prev_vma->vm_end))) {
 175                 if (!(vma->vm_flags & VM_GROWSDOWN))
 176                         goto bad_area;
 177                 if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start)
 178                     || REGION_OFFSET(address) >= RGN_MAP_LIMIT)
 179                         goto bad_area;
 180                 if (expand_stack(vma, address))
 181                         goto bad_area;
 182         } else {
 183                 vma = prev_vma;
 184                 if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start)
 185                     || REGION_OFFSET(address) >= RGN_MAP_LIMIT)
 186                         goto bad_area;
 187                 /*
 188                  * Since the register backing store is accessed sequentially,
 189                  * we disallow growing it by more than a page at a time.
 190                  */
 191                 if (address > vma->vm_end + PAGE_SIZE - sizeof(long))
 192                         goto bad_area;
 193                 if (expand_upwards(vma, address))
 194                         goto bad_area;
 195         }
 196         goto good_area;
 197
 198   bad_area:
 199         up_read(&mm->mmap_sem);
 200 #ifdef CONFIG_VIRTUAL_MEM_MAP
 201   bad_area_no_up:
 202 #endif
 203         if ((isr & IA64_ISR_SP)
 204             || ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH))
 205         {
 206                 /*
 207                  * This fault was due to a speculative load or lfetch.fault, set the "ed"
 208                  * bit in the psr to ensure forward progress.  (Target register will get a
 209                  * NaT for ld.s, lfetch will be canceled.)
 210                  */
 211                 ia64_psr(regs)->ed = 1;
 212                 return;
 213         }
 214         if (user_mode(regs)) {
 215                 si.si_signo = signal;
 216                 si.si_errno = 0;
 217                 si.si_code = code;
 218                 si.si_addr = (void __user *) address;
 219                 si.si_isr = isr;
 220                 si.si_flags = __ISR_VALID;
 221                 force_sig_info(signal, &si, current);
 222                 return;
 223         }
 224
 225   no_context:
 226         if ((isr & IA64_ISR_SP)
 227             || ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH))
 228         {
 229                 /*
 230                  * This fault was due to a speculative load or lfetch.fault, set the "ed"
 231                  * bit in the psr to ensure forward progress.  (Target register will get a
 232                  * NaT for ld.s, lfetch will be canceled.)
 233                  */
 234                 ia64_psr(regs)->ed = 1;
 235                 return;
 236         }
 237
 238         /*
 239          * Since we have no vma's for region 5, we might get here even if the address is
 240          * valid, due to the VHPT walker inserting a non present translation that becomes
 241          * stale. If that happens, the non present fault handler already purged the stale
 242          * translation, which fixed the problem. So, we check to see if the translation is
 243          * valid, and return if it is.
 244          */
 245         if (REGION_NUMBER(address) == 5 && mapped_kernel_page_is_present(address))
 246                 return;
 247
 248         if (ia64_done_with_exception(regs))
 249                 return;
 250
 251         /*
 252          * Oops. The kernel tried to access some bad page. We'll have to terminate things
 253          * with extreme prejudice.
 254          */
 255         bust_spinlocks(1);
 256
 257         if (address < PAGE_SIZE)
 258                 printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference (address %016lx)\n", address);
 259         else
 260                 printk(KERN_ALERT "Unable to handle kernel paging request at "
 261                        "virtual address %016lx\n", address);
 262         die("Oops", regs, isr);
 263         bust_spinlocks(0);
 264         do_exit(SIGKILL);
 265         return;
 266
 267   out_of_memory:
 268         up_read(&mm->mmap_sem);
 269         if (is_init(current)) {
 270                 yield();
 271                 down_read(&mm->mmap_sem);
 272                 goto survive;
 273         }
 274         printk(KERN_CRIT "VM: killing process %s\n", current->comm);
 275         if (user_mode(regs))
 276                 do_exit(SIGKILL);
 277         goto no_context;
 278 }