arch/ia64/mm/fault.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * MMU fault handling support.
   4  *
   5  * Copyright (C) 1998-2002 Hewlett-Packard Co
   6  *      David Mosberger-Tang <davidm@hpl.hp.com>
   7  */
   8 #include <linux/sched/signal.h>
   9 #include <linux/kernel.h>
  10 #include <linux/mm.h>
  11 #include <linux/extable.h>
  12 #include <linux/interrupt.h>
  13 #include <linux/kprobes.h>
  14 #include <linux/kdebug.h>
  15 #include <linux/prefetch.h>
  16 #include <linux/uaccess.h>
  17
  18 #include <asm/pgtable.h>
  19 #include <asm/processor.h>
  20 #include <asm/exception.h>
  21
  22 extern int die(char *, struct pt_regs *, long);
  23
  24 /*
  25  * Return TRUE if ADDRESS points at a page in the kernel's mapped segment
  26  * (inside region 5, on ia64) and that page is present.
  27  */
  28 static int
  29 mapped_kernel_page_is_present (unsigned long address)
  30 {
  31         pgd_t *pgd;
  32         pud_t *pud;
  33         pmd_t *pmd;
  34         pte_t *ptep, pte;
  35
  36         pgd = pgd_offset_k(address);
  37         if (pgd_none(*pgd) || pgd_bad(*pgd))
  38                 return 0;
  39
  40         pud = pud_offset(pgd, address);
  41         if (pud_none(*pud) || pud_bad(*pud))
  42                 return 0;
  43
  44         pmd = pmd_offset(pud, address);
  45         if (pmd_none(*pmd) || pmd_bad(*pmd))
  46                 return 0;
  47
  48         ptep = pte_offset_kernel(pmd, address);
  49         if (!ptep)
  50                 return 0;
  51
  52         pte = *ptep;
  53         return pte_present(pte);
  54 }
  55
  56 #       define VM_READ_BIT      0
  57 #       define VM_WRITE_BIT     1
  58 #       define VM_EXEC_BIT      2
  59
  60 void __kprobes
  61 ia64_do_page_fault (unsigned long address, unsigned long isr, struct pt_regs *regs)
  62 {
  63         int signal = SIGSEGV, code = SEGV_MAPERR;
  64         struct vm_area_struct *vma, *prev_vma;
  65         struct mm_struct *mm = current->mm;
  66         unsigned long mask;
  67         vm_fault_t fault;
  68         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
  69
  70         mask = ((((isr >> IA64_ISR_X_BIT) & 1UL) << VM_EXEC_BIT)
  71                 | (((isr >> IA64_ISR_W_BIT) & 1UL) << VM_WRITE_BIT));
  72
  73         /* mmap_sem is performance critical.... */
  74         prefetchw(&mm->mmap_sem);
  75
  76         /*
  77          * If we're in an interrupt or have no user context, we must not take the fault..
  78          */
  79         if (faulthandler_disabled() || !mm)
  80                 goto no_context;
  81
  82 #ifdef CONFIG_VIRTUAL_MEM_MAP
  83         /*
  84          * If fault is in region 5 and we are in the kernel, we may already
  85          * have the mmap_sem (pfn_valid macro is called during mmap). There
  86          * is no vma for region 5 addr's anyway, so skip getting the semaphore
  87          * and go directly to the exception handling code.
  88          */
  89
  90         if ((REGION_NUMBER(address) == 5) && !user_mode(regs))
  91                 goto bad_area_no_up;
  92 #endif
  93
  94         /*
  95          * This is to handle the kprobes on user space access instructions
  96          */
  97         if (kprobe_page_fault(regs, TRAP_BRKPT))
  98                 return;
  99
 100         if (user_mode(regs))
 101                 flags |= FAULT_FLAG_USER;
 102         if (mask & VM_WRITE)
 103                 flags |= FAULT_FLAG_WRITE;
 104 retry:
 105         down_read(&mm->mmap_sem);
 106
 107         vma = find_vma_prev(mm, address, &prev_vma);
 108         if (!vma && !prev_vma )
 109                 goto bad_area;
 110
 111         /*
 112          * find_vma_prev() returns vma such that address < vma->vm_end or NULL
 113          *
 114          * May find no vma, but could be that the last vm area is the
 115          * register backing store that needs to expand upwards, in
 116          * this case vma will be null, but prev_vma will ne non-null
 117          */
 118         if (( !vma && prev_vma ) || (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 #       if (((1 << VM_READ_BIT) != VM_READ || (1 << VM_WRITE_BIT) != VM_WRITE) \
 127             || (1 << VM_EXEC_BIT) != VM_EXEC)
 128 #               error File is out of sync with <linux/mm.h>.  Please update.
 129 #       endif
 130
 131         if (((isr >> IA64_ISR_R_BIT) & 1UL) && (!(vma->vm_flags & (VM_READ | VM_WRITE))))
 132                 goto bad_area;
 133
 134         if ((vma->vm_flags & mask) != mask)
 135                 goto bad_area;
 136
 137         /*
 138          * If for any reason at all we couldn't handle the fault, make
 139          * sure we exit gracefully rather than endlessly redo the
 140          * fault.
 141          */
 142         fault = handle_mm_fault(vma, address, flags);
 143
 144         if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
 145                 return;
 146
 147         if (unlikely(fault & VM_FAULT_ERROR)) {
 148                 /*
 149                  * We ran out of memory, or some other thing happened
 150                  * to us that made us unable to handle the page fault
 151                  * gracefully.
 152                  */
 153                 if (fault & VM_FAULT_OOM) {
 154                         goto out_of_memory;
 155                 } else if (fault & VM_FAULT_SIGSEGV) {
 156                         goto bad_area;
 157                 } else if (fault & VM_FAULT_SIGBUS) {
 158                         signal = SIGBUS;
 159                         goto bad_area;
 160                 }
 161                 BUG();
 162         }
 163
 164         if (flags & FAULT_FLAG_ALLOW_RETRY) {
 165                 if (fault & VM_FAULT_MAJOR)
 166                         current->maj_flt++;
 167                 else
 168                         current->min_flt++;
 169                 if (fault & VM_FAULT_RETRY) {
 170                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
 171                         flags |= FAULT_FLAG_TRIED;
 172
 173                          /* No need to up_read(&mm->mmap_sem) as we would
 174                          * have already released it in __lock_page_or_retry
 175                          * in mm/filemap.c.
 176                          */
 177
 178                         goto retry;
 179                 }
 180         }
 181
 182         up_read(&mm->mmap_sem);
 183         return;
 184
 185   check_expansion:
 186         if (!(prev_vma && (prev_vma->vm_flags & VM_GROWSUP) && (address == prev_vma->vm_end))) {
 187                 if (!vma)
 188                         goto bad_area;
 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                 force_sig_fault(signal, code, (void __user *) address,
 230                                 0, __ISR_VALID, isr);
 231                 return;
 232         }
 233
 234   no_context:
 235         if ((isr & IA64_ISR_SP)
 236             || ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH))
 237         {
 238                 /*
 239                  * This fault was due to a speculative load or lfetch.fault, set the "ed"
 240                  * bit in the psr to ensure forward progress.  (Target register will get a
 241                  * NaT for ld.s, lfetch will be canceled.)
 242                  */
 243                 ia64_psr(regs)->ed = 1;
 244                 return;
 245         }
 246
 247         /*
 248          * Since we have no vma's for region 5, we might get here even if the address is
 249          * valid, due to the VHPT walker inserting a non present translation that becomes
 250          * stale. If that happens, the non present fault handler already purged the stale
 251          * translation, which fixed the problem. So, we check to see if the translation is
 252          * valid, and return if it is.
 253          */
 254         if (REGION_NUMBER(address) == 5 && mapped_kernel_page_is_present(address))
 255                 return;
 256
 257         if (ia64_done_with_exception(regs))
 258                 return;
 259
 260         /*
 261          * Oops. The kernel tried to access some bad page. We'll have to terminate things
 262          * with extreme prejudice.
 263          */
 264         bust_spinlocks(1);
 265
 266         if (address < PAGE_SIZE)
 267                 printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference (address %016lx)\n", address);
 268         else
 269                 printk(KERN_ALERT "Unable to handle kernel paging request at "
 270                        "virtual address %016lx\n", address);
 271         if (die("Oops", regs, isr))
 272                 regs = NULL;
 273         bust_spinlocks(0);
 274         if (regs)
 275                 do_exit(SIGKILL);
 276         return;
 277
 278   out_of_memory:
 279         up_read(&mm->mmap_sem);
 280         if (!user_mode(regs))
 281                 goto no_context;
 282         pagefault_out_of_memory();
 283 }