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 #ifdef CONFIG_KPROBES
  25 static inline int notify_page_fault(struct pt_regs *regs, int trap)
  26 {
  27         int ret = 0;
  28
  29         if (!user_mode(regs)) {
  30                 /* kprobe_running() needs smp_processor_id() */
  31                 preempt_disable();
  32                 if (kprobe_running() && kprobe_fault_handler(regs, trap))
  33                         ret = 1;
  34                 preempt_enable();
  35         }
  36
  37         return ret;
  38 }
  39 #else
  40 static inline int notify_page_fault(struct pt_regs *regs, int trap)
  41 {
  42         return 0;
  43 }
  44 #endif
  45
  46 /*
  47  * Return TRUE if ADDRESS points at a page in the kernel's mapped segment
  48  * (inside region 5, on ia64) and that page is present.
  49  */
  50 static int
  51 mapped_kernel_page_is_present (unsigned long address)
  52 {
  53         pgd_t *pgd;
  54         pud_t *pud;
  55         pmd_t *pmd;
  56         pte_t *ptep, pte;
  57
  58         pgd = pgd_offset_k(address);
  59         if (pgd_none(*pgd) || pgd_bad(*pgd))
  60                 return 0;
  61
  62         pud = pud_offset(pgd, address);
  63         if (pud_none(*pud) || pud_bad(*pud))
  64                 return 0;
  65
  66         pmd = pmd_offset(pud, address);
  67         if (pmd_none(*pmd) || pmd_bad(*pmd))
  68                 return 0;
  69
  70         ptep = pte_offset_kernel(pmd, address);
  71         if (!ptep)
  72                 return 0;
  73
  74         pte = *ptep;
  75         return pte_present(pte);
  76 }
  77
  78 #       define VM_READ_BIT      0
  79 #       define VM_WRITE_BIT     1
  80 #       define VM_EXEC_BIT      2
  81
  82 void __kprobes
  83 ia64_do_page_fault (unsigned long address, unsigned long isr, struct pt_regs *regs)
  84 {
  85         int signal = SIGSEGV, code = SEGV_MAPERR;
  86         struct vm_area_struct *vma, *prev_vma;
  87         struct mm_struct *mm = current->mm;
  88         struct siginfo si;
  89         unsigned long mask;
  90         int fault;
  91         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
  92
  93         mask = ((((isr >> IA64_ISR_X_BIT) & 1UL) << VM_EXEC_BIT)
  94                 | (((isr >> IA64_ISR_W_BIT) & 1UL) << VM_WRITE_BIT));
  95
  96         /* mmap_sem is performance critical.... */
  97         prefetchw(&mm->mmap_sem);
  98
  99         /*
 100          * If we're in an interrupt or have no user context, we must not take the fault..
 101          */
 102         if (faulthandler_disabled() || !mm)
 103                 goto no_context;
 104
 105 #ifdef CONFIG_VIRTUAL_MEM_MAP
 106         /*
 107          * If fault is in region 5 and we are in the kernel, we may already
 108          * have the mmap_sem (pfn_valid macro is called during mmap). There
 109          * is no vma for region 5 addr's anyway, so skip getting the semaphore
 110          * and go directly to the exception handling code.
 111          */
 112
 113         if ((REGION_NUMBER(address) == 5) && !user_mode(regs))
 114                 goto bad_area_no_up;
 115 #endif
 116
 117         /*
 118          * This is to handle the kprobes on user space access instructions
 119          */
 120         if (notify_page_fault(regs, TRAP_BRKPT))
 121                 return;
 122
 123         if (user_mode(regs))
 124                 flags |= FAULT_FLAG_USER;
 125         if (mask & VM_WRITE)
 126                 flags |= FAULT_FLAG_WRITE;
 127 retry:
 128         down_read(&mm->mmap_sem);
 129
 130         vma = find_vma_prev(mm, address, &prev_vma);
 131         if (!vma && !prev_vma )
 132                 goto bad_area;
 133
 134         /*
 135          * find_vma_prev() returns vma such that address < vma->vm_end or NULL
 136          *
 137          * May find no vma, but could be that the last vm area is the
 138          * register backing store that needs to expand upwards, in
 139          * this case vma will be null, but prev_vma will ne non-null
 140          */
 141         if (( !vma && prev_vma ) || (address < vma->vm_start) )
 142                 goto check_expansion;
 143
 144   good_area:
 145         code = SEGV_ACCERR;
 146
 147         /* OK, we've got a good vm_area for this memory area.  Check the access permissions: */
 148
 149 #       if (((1 << VM_READ_BIT) != VM_READ || (1 << VM_WRITE_BIT) != VM_WRITE) \
 150             || (1 << VM_EXEC_BIT) != VM_EXEC)
 151 #               error File is out of sync with <linux/mm.h>.  Please update.
 152 #       endif
 153
 154         if (((isr >> IA64_ISR_R_BIT) & 1UL) && (!(vma->vm_flags & (VM_READ | VM_WRITE))))
 155                 goto bad_area;
 156
 157         if ((vma->vm_flags & mask) != mask)
 158                 goto bad_area;
 159
 160         /*
 161          * If for any reason at all we couldn't handle the fault, make
 162          * sure we exit gracefully rather than endlessly redo the
 163          * fault.
 164          */
 165         fault = handle_mm_fault(vma, address, flags);
 166
 167         if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
 168                 return;
 169
 170         if (unlikely(fault & VM_FAULT_ERROR)) {
 171                 /*
 172                  * We ran out of memory, or some other thing happened
 173                  * to us that made us unable to handle the page fault
 174                  * gracefully.
 175                  */
 176                 if (fault & VM_FAULT_OOM) {
 177                         goto out_of_memory;
 178                 } else if (fault & VM_FAULT_SIGSEGV) {
 179                         goto bad_area;
 180                 } else if (fault & VM_FAULT_SIGBUS) {
 181                         signal = SIGBUS;
 182                         goto bad_area;
 183                 }
 184                 BUG();
 185         }
 186
 187         if (flags & FAULT_FLAG_ALLOW_RETRY) {
 188                 if (fault & VM_FAULT_MAJOR)
 189                         current->maj_flt++;
 190                 else
 191                         current->min_flt++;
 192                 if (fault & VM_FAULT_RETRY) {
 193                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
 194                         flags |= FAULT_FLAG_TRIED;
 195
 196                          /* No need to up_read(&mm->mmap_sem) as we would
 197                          * have already released it in __lock_page_or_retry
 198                          * in mm/filemap.c.
 199                          */
 200
 201                         goto retry;
 202                 }
 203         }
 204
 205         up_read(&mm->mmap_sem);
 206         return;
 207
 208   check_expansion:
 209         if (!(prev_vma && (prev_vma->vm_flags & VM_GROWSUP) && (address == prev_vma->vm_end))) {
 210                 if (!vma)
 211                         goto bad_area;
 212                 if (!(vma->vm_flags & VM_GROWSDOWN))
 213                         goto bad_area;
 214                 if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start)
 215                     || REGION_OFFSET(address) >= RGN_MAP_LIMIT)
 216                         goto bad_area;
 217                 if (expand_stack(vma, address))
 218                         goto bad_area;
 219         } else {
 220                 vma = prev_vma;
 221                 if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start)
 222                     || REGION_OFFSET(address) >= RGN_MAP_LIMIT)
 223                         goto bad_area;
 224                 /*
 225                  * Since the register backing store is accessed sequentially,
 226                  * we disallow growing it by more than a page at a time.
 227                  */
 228                 if (address > vma->vm_end + PAGE_SIZE - sizeof(long))
 229                         goto bad_area;
 230                 if (expand_upwards(vma, address))
 231                         goto bad_area;
 232         }
 233         goto good_area;
 234
 235   bad_area:
 236         up_read(&mm->mmap_sem);
 237 #ifdef CONFIG_VIRTUAL_MEM_MAP
 238   bad_area_no_up:
 239 #endif
 240         if ((isr & IA64_ISR_SP)
 241             || ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH))
 242         {
 243                 /*
 244                  * This fault was due to a speculative load or lfetch.fault, set the "ed"
 245                  * bit in the psr to ensure forward progress.  (Target register will get a
 246                  * NaT for ld.s, lfetch will be canceled.)
 247                  */
 248                 ia64_psr(regs)->ed = 1;
 249                 return;
 250         }
 251         if (user_mode(regs)) {
 252                 si.si_signo = signal;
 253                 si.si_errno = 0;
 254                 si.si_code = code;
 255                 si.si_addr = (void __user *) address;
 256                 si.si_isr = isr;
 257                 si.si_flags = __ISR_VALID;
 258                 force_sig_info(signal, &si, current);
 259                 return;
 260         }
 261
 262   no_context:
 263         if ((isr & IA64_ISR_SP)
 264             || ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH))
 265         {
 266                 /*
 267                  * This fault was due to a speculative load or lfetch.fault, set the "ed"
 268                  * bit in the psr to ensure forward progress.  (Target register will get a
 269                  * NaT for ld.s, lfetch will be canceled.)
 270                  */
 271                 ia64_psr(regs)->ed = 1;
 272                 return;
 273         }
 274
 275         /*
 276          * Since we have no vma's for region 5, we might get here even if the address is
 277          * valid, due to the VHPT walker inserting a non present translation that becomes
 278          * stale. If that happens, the non present fault handler already purged the stale
 279          * translation, which fixed the problem. So, we check to see if the translation is
 280          * valid, and return if it is.
 281          */
 282         if (REGION_NUMBER(address) == 5 && mapped_kernel_page_is_present(address))
 283                 return;
 284
 285         if (ia64_done_with_exception(regs))
 286                 return;
 287
 288         /*
 289          * Oops. The kernel tried to access some bad page. We'll have to terminate things
 290          * with extreme prejudice.
 291          */
 292         bust_spinlocks(1);
 293
 294         if (address < PAGE_SIZE)
 295                 printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference (address %016lx)\n", address);
 296         else
 297                 printk(KERN_ALERT "Unable to handle kernel paging request at "
 298                        "virtual address %016lx\n", address);
 299         if (die("Oops", regs, isr))
 300                 regs = NULL;
 301         bust_spinlocks(0);
 302         if (regs)
 303                 do_exit(SIGKILL);
 304         return;
 305
 306   out_of_memory:
 307         up_read(&mm->mmap_sem);
 308         if (!user_mode(regs))
 309                 goto no_context;
 310         pagefault_out_of_memory();
 311 }