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/signal.h>
   8 #include <linux/kernel.h>
   9 #include <linux/mm.h>
  10 #include <linux/extable.h>
  11 #include <linux/interrupt.h>
  12 #include <linux/kprobes.h>
  13 #include <linux/kdebug.h>
  14 #include <linux/prefetch.h>
  15 #include <linux/uaccess.h>
  16
  17 #include <asm/pgtable.h>
  18 #include <asm/processor.h>
  19 #include <asm/exception.h>
  20
  21 extern int die(char *, struct pt_regs *, long);
  22
  23 #ifdef CONFIG_KPROBES
  24 static inline int notify_page_fault(struct pt_regs *regs, int trap)
  25 {
  26         int ret = 0;
  27
  28         if (!user_mode(regs)) {
  29                 /* kprobe_running() needs smp_processor_id() */
  30                 preempt_disable();
  31                 if (kprobe_running() && kprobe_fault_handler(regs, trap))
  32                         ret = 1;
  33                 preempt_enable();
  34         }
  35
  36         return ret;
  37 }
  38 #else
  39 static inline int notify_page_fault(struct pt_regs *regs, int trap)
  40 {
  41         return 0;
  42 }
  43 #endif
  44
  45 /*
  46  * Return TRUE if ADDRESS points at a page in the kernel's mapped segment
  47  * (inside region 5, on ia64) and that page is present.
  48  */
  49 static int
  50 mapped_kernel_page_is_present (unsigned long address)
  51 {
  52         pgd_t *pgd;
  53         pud_t *pud;
  54         pmd_t *pmd;
  55         pte_t *ptep, pte;
  56
  57         pgd = pgd_offset_k(address);
  58         if (pgd_none(*pgd) || pgd_bad(*pgd))
  59                 return 0;
  60
  61         pud = pud_offset(pgd, address);
  62         if (pud_none(*pud) || pud_bad(*pud))
  63                 return 0;
  64
  65         pmd = pmd_offset(pud, address);
  66         if (pmd_none(*pmd) || pmd_bad(*pmd))
  67                 return 0;
  68
  69         ptep = pte_offset_kernel(pmd, address);
  70         if (!ptep)
  71                 return 0;
  72
  73         pte = *ptep;
  74         return pte_present(pte);
  75 }
  76
  77 #       define VM_READ_BIT      0
  78 #       define VM_WRITE_BIT     1
  79 #       define VM_EXEC_BIT      2
  80
  81 void __kprobes
  82 ia64_do_page_fault (unsigned long address, unsigned long isr, struct pt_regs *regs)
  83 {
  84         int signal = SIGSEGV, code = SEGV_MAPERR;
  85         struct vm_area_struct *vma, *prev_vma;
  86         struct mm_struct *mm = current->mm;
  87         struct siginfo si;
  88         unsigned long mask;
  89         int fault;
  90         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
  91
  92         mask = ((((isr >> IA64_ISR_X_BIT) & 1UL) << VM_EXEC_BIT)
  93                 | (((isr >> IA64_ISR_W_BIT) & 1UL) << VM_WRITE_BIT));
  94
  95         /* mmap_sem is performance critical.... */
  96         prefetchw(&mm->mmap_sem);
  97
  98         /*
  99          * If we're in an interrupt or have no user context, we must not take the fault..
 100          */
 101         if (faulthandler_disabled() || !mm)
 102                 goto no_context;
 103
 104 #ifdef CONFIG_VIRTUAL_MEM_MAP
 105         /*
 106          * If fault is in region 5 and we are in the kernel, we may already
 107          * have the mmap_sem (pfn_valid macro is called during mmap). There
 108          * is no vma for region 5 addr's anyway, so skip getting the semaphore
 109          * and go directly to the exception handling code.
 110          */
 111
 112         if ((REGION_NUMBER(address) == 5) && !user_mode(regs))
 113                 goto bad_area_no_up;
 114 #endif
 115
 116         /*
 117          * This is to handle the kprobes on user space access instructions
 118          */
 119         if (notify_page_fault(regs, TRAP_BRKPT))
 120                 return;
 121
 122         if (user_mode(regs))
 123                 flags |= FAULT_FLAG_USER;
 124         if (mask & VM_WRITE)
 125                 flags |= FAULT_FLAG_WRITE;
 126 retry:
 127         down_read(&mm->mmap_sem);
 128
 129         vma = find_vma_prev(mm, address, &prev_vma);
 130         if (!vma && !prev_vma )
 131                 goto bad_area;
 132
 133         /*
 134          * find_vma_prev() returns vma such that address < vma->vm_end or NULL
 135          *
 136          * May find no vma, but could be that the last vm area is the
 137          * register backing store that needs to expand upwards, in
 138          * this case vma will be null, but prev_vma will ne non-null
 139          */
 140         if (( !vma && prev_vma ) || (address < vma->vm_start) )
 141                 goto check_expansion;
 142
 143   good_area:
 144         code = SEGV_ACCERR;
 145
 146         /* OK, we've got a good vm_area for this memory area.  Check the access permissions: */
 147
 148 #       if (((1 << VM_READ_BIT) != VM_READ || (1 << VM_WRITE_BIT) != VM_WRITE) \
 149             || (1 << VM_EXEC_BIT) != VM_EXEC)
 150 #               error File is out of sync with <linux/mm.h>.  Please update.
 151 #       endif
 152
 153         if (((isr >> IA64_ISR_R_BIT) & 1UL) && (!(vma->vm_flags & (VM_READ | VM_WRITE))))
 154                 goto bad_area;
 155
 156         if ((vma->vm_flags & mask) != mask)
 157                 goto bad_area;
 158
 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         fault = handle_mm_fault(vma, address, flags);
 165
 166         if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
 167                 return;
 168
 169         if (unlikely(fault & VM_FAULT_ERROR)) {
 170                 /*
 171                  * We ran out of memory, or some other thing happened
 172                  * to us that made us unable to handle the page fault
 173                  * gracefully.
 174                  */
 175                 if (fault & VM_FAULT_OOM) {
 176                         goto out_of_memory;
 177                 } else if (fault & VM_FAULT_SIGSEGV) {
 178                         goto bad_area;
 179                 } else if (fault & VM_FAULT_SIGBUS) {
 180                         signal = SIGBUS;
 181                         goto bad_area;
 182                 }
 183                 BUG();
 184         }
 185
 186         if (flags & FAULT_FLAG_ALLOW_RETRY) {
 187                 if (fault & VM_FAULT_MAJOR)
 188                         current->maj_flt++;
 189                 else
 190                         current->min_flt++;
 191                 if (fault & VM_FAULT_RETRY) {
 192                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
 193                         flags |= FAULT_FLAG_TRIED;
 194
 195                          /* No need to up_read(&mm->mmap_sem) as we would
 196                          * have already released it in __lock_page_or_retry
 197                          * in mm/filemap.c.
 198                          */
 199
 200                         goto retry;
 201                 }
 202         }
 203
 204         up_read(&mm->mmap_sem);
 205         return;
 206
 207   check_expansion:
 208         if (!(prev_vma && (prev_vma->vm_flags & VM_GROWSUP) && (address == prev_vma->vm_end))) {
 209                 if (!vma)
 210                         goto bad_area;
 211                 if (!(vma->vm_flags & VM_GROWSDOWN))
 212                         goto bad_area;
 213                 if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start)
 214                     || REGION_OFFSET(address) >= RGN_MAP_LIMIT)
 215                         goto bad_area;
 216                 if (expand_stack(vma, address))
 217                         goto bad_area;
 218         } else {
 219                 vma = prev_vma;
 220                 if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start)
 221                     || REGION_OFFSET(address) >= RGN_MAP_LIMIT)
 222                         goto bad_area;
 223                 /*
 224                  * Since the register backing store is accessed sequentially,
 225                  * we disallow growing it by more than a page at a time.
 226                  */
 227                 if (address > vma->vm_end + PAGE_SIZE - sizeof(long))
 228                         goto bad_area;
 229                 if (expand_upwards(vma, address))
 230                         goto bad_area;
 231         }
 232         goto good_area;
 233
 234   bad_area:
 235         up_read(&mm->mmap_sem);
 236 #ifdef CONFIG_VIRTUAL_MEM_MAP
 237   bad_area_no_up:
 238 #endif
 239         if ((isr & IA64_ISR_SP)
 240             || ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH))
 241         {
 242                 /*
 243                  * This fault was due to a speculative load or lfetch.fault, set the "ed"
 244                  * bit in the psr to ensure forward progress.  (Target register will get a
 245                  * NaT for ld.s, lfetch will be canceled.)
 246                  */
 247                 ia64_psr(regs)->ed = 1;
 248                 return;
 249         }
 250         if (user_mode(regs)) {
 251                 si.si_signo = signal;
 252                 si.si_errno = 0;
 253                 si.si_code = code;
 254                 si.si_addr = (void __user *) address;
 255                 si.si_isr = isr;
 256                 si.si_flags = __ISR_VALID;
 257                 force_sig_info(signal, &si, current);
 258                 return;
 259         }
 260
 261   no_context:
 262         if ((isr & IA64_ISR_SP)
 263             || ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH))
 264         {
 265                 /*
 266                  * This fault was due to a speculative load or lfetch.fault, set the "ed"
 267                  * bit in the psr to ensure forward progress.  (Target register will get a
 268                  * NaT for ld.s, lfetch will be canceled.)
 269                  */
 270                 ia64_psr(regs)->ed = 1;
 271                 return;
 272         }
 273
 274         /*
 275          * Since we have no vma's for region 5, we might get here even if the address is
 276          * valid, due to the VHPT walker inserting a non present translation that becomes
 277          * stale. If that happens, the non present fault handler already purged the stale
 278          * translation, which fixed the problem. So, we check to see if the translation is
 279          * valid, and return if it is.
 280          */
 281         if (REGION_NUMBER(address) == 5 && mapped_kernel_page_is_present(address))
 282                 return;
 283
 284         if (ia64_done_with_exception(regs))
 285                 return;
 286
 287         /*
 288          * Oops. The kernel tried to access some bad page. We'll have to terminate things
 289          * with extreme prejudice.
 290          */
 291         bust_spinlocks(1);
 292
 293         if (address < PAGE_SIZE)
 294                 printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference (address %016lx)\n", address);
 295         else
 296                 printk(KERN_ALERT "Unable to handle kernel paging request at "
 297                        "virtual address %016lx\n", address);
 298         if (die("Oops", regs, isr))
 299                 regs = NULL;
 300         bust_spinlocks(0);
 301         if (regs)
 302                 do_exit(SIGKILL);
 303         return;
 304
 305   out_of_memory:
 306         up_read(&mm->mmap_sem);
 307         if (!user_mode(regs))
 308                 goto no_context;
 309         pagefault_out_of_memory();
 310 }