arch/powerpc/mm/fault.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  *  PowerPC version
   4  *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
   5  *
   6  *  Derived from "arch/i386/mm/fault.c"
   7  *    Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
   8  *
   9  *  Modified by Cort Dougan and Paul Mackerras.
  10  *
  11  *  Modified for PPC64 by Dave Engebretsen (engebret@ibm.com)
  12  */
  13
  14 #include <linux/signal.h>
  15 #include <linux/sched.h>
  16 #include <linux/sched/task_stack.h>
  17 #include <linux/kernel.h>
  18 #include <linux/errno.h>
  19 #include <linux/string.h>
  20 #include <linux/types.h>
  21 #include <linux/pagemap.h>
  22 #include <linux/ptrace.h>
  23 #include <linux/mman.h>
  24 #include <linux/mm.h>
  25 #include <linux/interrupt.h>
  26 #include <linux/highmem.h>
  27 #include <linux/extable.h>
  28 #include <linux/kprobes.h>
  29 #include <linux/kdebug.h>
  30 #include <linux/perf_event.h>
  31 #include <linux/ratelimit.h>
  32 #include <linux/context_tracking.h>
  33 #include <linux/hugetlb.h>
  34 #include <linux/uaccess.h>
  35
  36 #include <asm/firmware.h>
  37 #include <asm/page.h>
  38 #include <asm/pgtable.h>
  39 #include <asm/mmu.h>
  40 #include <asm/mmu_context.h>
  41 #include <asm/siginfo.h>
  42 #include <asm/debug.h>
  43 #include <asm/kup.h>
  44
  45 static inline bool notify_page_fault(struct pt_regs *regs)
  46 {
  47         bool ret = false;
  48
  49 #ifdef CONFIG_KPROBES
  50         /* kprobe_running() needs smp_processor_id() */
  51         if (!user_mode(regs)) {
  52                 preempt_disable();
  53                 if (kprobe_running() && kprobe_fault_handler(regs, 11))
  54                         ret = true;
  55                 preempt_enable();
  56         }
  57 #endif /* CONFIG_KPROBES */
  58
  59         if (unlikely(debugger_fault_handler(regs)))
  60                 ret = true;
  61
  62         return ret;
  63 }
  64
  65 /*
  66  * Check whether the instruction inst is a store using
  67  * an update addressing form which will update r1.
  68  */
  69 static bool store_updates_sp(unsigned int inst)
  70 {
  71         /* check for 1 in the rA field */
  72         if (((inst >> 16) & 0x1f) != 1)
  73                 return false;
  74         /* check major opcode */
  75         switch (inst >> 26) {
  76         case OP_STWU:
  77         case OP_STBU:
  78         case OP_STHU:
  79         case OP_STFSU:
  80         case OP_STFDU:
  81                 return true;
  82         case OP_STD:    /* std or stdu */
  83                 return (inst & 3) == 1;
  84         case OP_31:
  85                 /* check minor opcode */
  86                 switch ((inst >> 1) & 0x3ff) {
  87                 case OP_31_XOP_STDUX:
  88                 case OP_31_XOP_STWUX:
  89                 case OP_31_XOP_STBUX:
  90                 case OP_31_XOP_STHUX:
  91                 case OP_31_XOP_STFSUX:
  92                 case OP_31_XOP_STFDUX:
  93                         return true;
  94                 }
  95         }
  96         return false;
  97 }
  98 /*
  99  * do_page_fault error handling helpers
 100  */
 101
 102 static int
 103 __bad_area_nosemaphore(struct pt_regs *regs, unsigned long address, int si_code)
 104 {
 105         /*
 106          * If we are in kernel mode, bail out with a SEGV, this will
 107          * be caught by the assembly which will restore the non-volatile
 108          * registers before calling bad_page_fault()
 109          */
 110         if (!user_mode(regs))
 111                 return SIGSEGV;
 112
 113         _exception(SIGSEGV, regs, si_code, address);
 114
 115         return 0;
 116 }
 117
 118 static noinline int bad_area_nosemaphore(struct pt_regs *regs, unsigned long address)
 119 {
 120         return __bad_area_nosemaphore(regs, address, SEGV_MAPERR);
 121 }
 122
 123 static int __bad_area(struct pt_regs *regs, unsigned long address, int si_code)
 124 {
 125         struct mm_struct *mm = current->mm;
 126
 127         /*
 128          * Something tried to access memory that isn't in our memory map..
 129          * Fix it, but check if it's kernel or user first..
 130          */
 131         up_read(&mm->mmap_sem);
 132
 133         return __bad_area_nosemaphore(regs, address, si_code);
 134 }
 135
 136 static noinline int bad_area(struct pt_regs *regs, unsigned long address)
 137 {
 138         return __bad_area(regs, address, SEGV_MAPERR);
 139 }
 140
 141 static int bad_key_fault_exception(struct pt_regs *regs, unsigned long address,
 142                                     int pkey)
 143 {
 144         /*
 145          * If we are in kernel mode, bail out with a SEGV, this will
 146          * be caught by the assembly which will restore the non-volatile
 147          * registers before calling bad_page_fault()
 148          */
 149         if (!user_mode(regs))
 150                 return SIGSEGV;
 151
 152         _exception_pkey(regs, address, pkey);
 153
 154         return 0;
 155 }
 156
 157 static noinline int bad_access(struct pt_regs *regs, unsigned long address)
 158 {
 159         return __bad_area(regs, address, SEGV_ACCERR);
 160 }
 161
 162 static int do_sigbus(struct pt_regs *regs, unsigned long address,
 163                      vm_fault_t fault)
 164 {
 165         if (!user_mode(regs))
 166                 return SIGBUS;
 167
 168         current->thread.trap_nr = BUS_ADRERR;
 169 #ifdef CONFIG_MEMORY_FAILURE
 170         if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
 171                 unsigned int lsb = 0; /* shutup gcc */
 172
 173                 pr_err("MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
 174                         current->comm, current->pid, address);
 175
 176                 if (fault & VM_FAULT_HWPOISON_LARGE)
 177                         lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
 178                 if (fault & VM_FAULT_HWPOISON)
 179                         lsb = PAGE_SHIFT;
 180
 181                 force_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb,
 182                                  current);
 183                 return 0;
 184         }
 185
 186 #endif
 187         force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address, current);
 188         return 0;
 189 }
 190
 191 static int mm_fault_error(struct pt_regs *regs, unsigned long addr,
 192                                 vm_fault_t fault)
 193 {
 194         /*
 195          * Kernel page fault interrupted by SIGKILL. We have no reason to
 196          * continue processing.
 197          */
 198         if (fatal_signal_pending(current) && !user_mode(regs))
 199                 return SIGKILL;
 200
 201         /* Out of memory */
 202         if (fault & VM_FAULT_OOM) {
 203                 /*
 204                  * We ran out of memory, or some other thing happened to us that
 205                  * made us unable to handle the page fault gracefully.
 206                  */
 207                 if (!user_mode(regs))
 208                         return SIGSEGV;
 209                 pagefault_out_of_memory();
 210         } else {
 211                 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
 212                              VM_FAULT_HWPOISON_LARGE))
 213                         return do_sigbus(regs, addr, fault);
 214                 else if (fault & VM_FAULT_SIGSEGV)
 215                         return bad_area_nosemaphore(regs, addr);
 216                 else
 217                         BUG();
 218         }
 219         return 0;
 220 }
 221
 222 /* Is this a bad kernel fault ? */
 223 static bool bad_kernel_fault(struct pt_regs *regs, unsigned long error_code,
 224                              unsigned long address, bool is_write)
 225 {
 226         int is_exec = TRAP(regs) == 0x400;
 227
 228         /* NX faults set DSISR_PROTFAULT on the 8xx, DSISR_NOEXEC_OR_G on others */
 229         if (is_exec && (error_code & (DSISR_NOEXEC_OR_G | DSISR_KEYFAULT |
 230                                       DSISR_PROTFAULT))) {
 231                 pr_crit_ratelimited("kernel tried to execute %s page (%lx) - exploit attempt? (uid: %d)\n",
 232                                     address >= TASK_SIZE ? "exec-protected" : "user",
 233                                     address,
 234                                     from_kuid(&init_user_ns, current_uid()));
 235
 236                 // Kernel exec fault is always bad
 237                 return true;
 238         }
 239
 240         if (!is_exec && address < TASK_SIZE && (error_code & DSISR_PROTFAULT) &&
 241             !search_exception_tables(regs->nip)) {
 242                 pr_crit_ratelimited("Kernel attempted to access user page (%lx) - exploit attempt? (uid: %d)\n",
 243                                     address,
 244                                     from_kuid(&init_user_ns, current_uid()));
 245         }
 246
 247         // Kernel fault on kernel address is bad
 248         if (address >= TASK_SIZE)
 249                 return true;
 250
 251         // Fault on user outside of certain regions (eg. copy_tofrom_user()) is bad
 252         if (!search_exception_tables(regs->nip))
 253                 return true;
 254
 255         // Read/write fault in a valid region (the exception table search passed
 256         // above), but blocked by KUAP is bad, it can never succeed.
 257         if (bad_kuap_fault(regs, is_write))
 258                 return true;
 259
 260         // What's left? Kernel fault on user in well defined regions (extable
 261         // matched), and allowed by KUAP in the faulting context.
 262         return false;
 263 }
 264
 265 static bool bad_stack_expansion(struct pt_regs *regs, unsigned long address,
 266                                 struct vm_area_struct *vma, unsigned int flags,
 267                                 bool *must_retry)
 268 {
 269         /*
 270          * N.B. The POWER/Open ABI allows programs to access up to
 271          * 288 bytes below the stack pointer.
 272          * The kernel signal delivery code writes up to about 1.5kB
 273          * below the stack pointer (r1) before decrementing it.
 274          * The exec code can write slightly over 640kB to the stack
 275          * before setting the user r1.  Thus we allow the stack to
 276          * expand to 1MB without further checks.
 277          */
 278         if (address + 0x100000 < vma->vm_end) {
 279                 unsigned int __user *nip = (unsigned int __user *)regs->nip;
 280                 /* get user regs even if this fault is in kernel mode */
 281                 struct pt_regs *uregs = current->thread.regs;
 282                 if (uregs == NULL)
 283                         return true;
 284
 285                 /*
 286                  * A user-mode access to an address a long way below
 287                  * the stack pointer is only valid if the instruction
 288                  * is one which would update the stack pointer to the
 289                  * address accessed if the instruction completed,
 290                  * i.e. either stwu rs,n(r1) or stwux rs,r1,rb
 291                  * (or the byte, halfword, float or double forms).
 292                  *
 293                  * If we don't check this then any write to the area
 294                  * between the last mapped region and the stack will
 295                  * expand the stack rather than segfaulting.
 296                  */
 297                 if (address + 2048 >= uregs->gpr[1])
 298                         return false;
 299
 300                 if ((flags & FAULT_FLAG_WRITE) && (flags & FAULT_FLAG_USER) &&
 301                     access_ok(nip, sizeof(*nip))) {
 302                         unsigned int inst;
 303                         int res;
 304
 305                         pagefault_disable();
 306                         res = __get_user_inatomic(inst, nip);
 307                         pagefault_enable();
 308                         if (!res)
 309                                 return !store_updates_sp(inst);
 310                         *must_retry = true;
 311                 }
 312                 return true;
 313         }
 314         return false;
 315 }
 316
 317 static bool access_error(bool is_write, bool is_exec,
 318                          struct vm_area_struct *vma)
 319 {
 320         /*
 321          * Allow execution from readable areas if the MMU does not
 322          * provide separate controls over reading and executing.
 323          *
 324          * Note: That code used to not be enabled for 4xx/BookE.
 325          * It is now as I/D cache coherency for these is done at
 326          * set_pte_at() time and I see no reason why the test
 327          * below wouldn't be valid on those processors. This -may-
 328          * break programs compiled with a really old ABI though.
 329          */
 330         if (is_exec) {
 331                 return !(vma->vm_flags & VM_EXEC) &&
 332                         (cpu_has_feature(CPU_FTR_NOEXECUTE) ||
 333                          !(vma->vm_flags & (VM_READ | VM_WRITE)));
 334         }
 335
 336         if (is_write) {
 337                 if (unlikely(!(vma->vm_flags & VM_WRITE)))
 338                         return true;
 339                 return false;
 340         }
 341
 342         if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))))
 343                 return true;
 344         /*
 345          * We should ideally do the vma pkey access check here. But in the
 346          * fault path, handle_mm_fault() also does the same check. To avoid
 347          * these multiple checks, we skip it here and handle access error due
 348          * to pkeys later.
 349          */
 350         return false;
 351 }
 352
 353 #ifdef CONFIG_PPC_SMLPAR
 354 static inline void cmo_account_page_fault(void)
 355 {
 356         if (firmware_has_feature(FW_FEATURE_CMO)) {
 357                 u32 page_ins;
 358
 359                 preempt_disable();
 360                 page_ins = be32_to_cpu(get_lppaca()->page_ins);
 361                 page_ins += 1 << PAGE_FACTOR;
 362                 get_lppaca()->page_ins = cpu_to_be32(page_ins);
 363                 preempt_enable();
 364         }
 365 }
 366 #else
 367 static inline void cmo_account_page_fault(void) { }
 368 #endif /* CONFIG_PPC_SMLPAR */
 369
 370 #ifdef CONFIG_PPC_BOOK3S
 371 static void sanity_check_fault(bool is_write, bool is_user,
 372                                unsigned long error_code, unsigned long address)
 373 {
 374         /*
 375          * Userspace trying to access kernel address, we get PROTFAULT for that.
 376          */
 377         if (is_user && address >= TASK_SIZE) {
 378                 pr_crit_ratelimited("%s[%d]: User access of kernel address (%lx) - exploit attempt? (uid: %d)\n",
 379                                    current->comm, current->pid, address,
 380                                    from_kuid(&init_user_ns, current_uid()));
 381                 return;
 382         }
 383
 384         /*
 385          * For hash translation mode, we should never get a
 386          * PROTFAULT. Any update to pte to reduce access will result in us
 387          * removing the hash page table entry, thus resulting in a DSISR_NOHPTE
 388          * fault instead of DSISR_PROTFAULT.
 389          *
 390          * A pte update to relax the access will not result in a hash page table
 391          * entry invalidate and hence can result in DSISR_PROTFAULT.
 392          * ptep_set_access_flags() doesn't do a hpte flush. This is why we have
 393          * the special !is_write in the below conditional.
 394          *
 395          * For platforms that doesn't supports coherent icache and do support
 396          * per page noexec bit, we do setup things such that we do the
 397          * sync between D/I cache via fault. But that is handled via low level
 398          * hash fault code (hash_page_do_lazy_icache()) and we should not reach
 399          * here in such case.
 400          *
 401          * For wrong access that can result in PROTFAULT, the above vma->vm_flags
 402          * check should handle those and hence we should fall to the bad_area
 403          * handling correctly.
 404          *
 405          * For embedded with per page exec support that doesn't support coherent
 406          * icache we do get PROTFAULT and we handle that D/I cache sync in
 407          * set_pte_at while taking the noexec/prot fault. Hence this is WARN_ON
 408          * is conditional for server MMU.
 409          *
 410          * For radix, we can get prot fault for autonuma case, because radix
 411          * page table will have them marked noaccess for user.
 412          */
 413         if (radix_enabled() || is_write)
 414                 return;
 415
 416         WARN_ON_ONCE(error_code & DSISR_PROTFAULT);
 417 }
 418 #else
 419 static void sanity_check_fault(bool is_write, bool is_user,
 420                                unsigned long error_code, unsigned long address) { }
 421 #endif /* CONFIG_PPC_BOOK3S */
 422
 423 /*
 424  * Define the correct "is_write" bit in error_code based
 425  * on the processor family
 426  */
 427 #if (defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
 428 #define page_fault_is_write(__err)      ((__err) & ESR_DST)
 429 #define page_fault_is_bad(__err)        (0)
 430 #else
 431 #define page_fault_is_write(__err)      ((__err) & DSISR_ISSTORE)
 432 #if defined(CONFIG_PPC_8xx)
 433 #define page_fault_is_bad(__err)        ((__err) & DSISR_NOEXEC_OR_G)
 434 #elif defined(CONFIG_PPC64)
 435 #define page_fault_is_bad(__err)        ((__err) & DSISR_BAD_FAULT_64S)
 436 #else
 437 #define page_fault_is_bad(__err)        ((__err) & DSISR_BAD_FAULT_32S)
 438 #endif
 439 #endif
 440
 441 /*
 442  * For 600- and 800-family processors, the error_code parameter is DSISR
 443  * for a data fault, SRR1 for an instruction fault. For 400-family processors
 444  * the error_code parameter is ESR for a data fault, 0 for an instruction
 445  * fault.
 446  * For 64-bit processors, the error_code parameter is
 447  *  - DSISR for a non-SLB data access fault,
 448  *  - SRR1 & 0x08000000 for a non-SLB instruction access fault
 449  *  - 0 any SLB fault.
 450  *
 451  * The return value is 0 if the fault was handled, or the signal
 452  * number if this is a kernel fault that can't be handled here.
 453  */
 454 static int __do_page_fault(struct pt_regs *regs, unsigned long address,
 455                            unsigned long error_code)
 456 {
 457         struct vm_area_struct * vma;
 458         struct mm_struct *mm = current->mm;
 459         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
 460         int is_exec = TRAP(regs) == 0x400;
 461         int is_user = user_mode(regs);
 462         int is_write = page_fault_is_write(error_code);
 463         vm_fault_t fault, major = 0;
 464         bool must_retry = false;
 465
 466         if (notify_page_fault(regs))
 467                 return 0;
 468
 469         if (unlikely(page_fault_is_bad(error_code))) {
 470                 if (is_user) {
 471                         _exception(SIGBUS, regs, BUS_OBJERR, address);
 472                         return 0;
 473                 }
 474                 return SIGBUS;
 475         }
 476
 477         /* Additional sanity check(s) */
 478         sanity_check_fault(is_write, is_user, error_code, address);
 479
 480         /*
 481          * The kernel should never take an execute fault nor should it
 482          * take a page fault to a kernel address or a page fault to a user
 483          * address outside of dedicated places
 484          */
 485         if (unlikely(!is_user && bad_kernel_fault(regs, error_code, address, is_write)))
 486                 return SIGSEGV;
 487
 488         /*
 489          * If we're in an interrupt, have no user context or are running
 490          * in a region with pagefaults disabled then we must not take the fault
 491          */
 492         if (unlikely(faulthandler_disabled() || !mm)) {
 493                 if (is_user)
 494                         printk_ratelimited(KERN_ERR "Page fault in user mode"
 495                                            " with faulthandler_disabled()=%d"
 496                                            " mm=%p\n",
 497                                            faulthandler_disabled(), mm);
 498                 return bad_area_nosemaphore(regs, address);
 499         }
 500
 501         /* We restore the interrupt state now */
 502         if (!arch_irq_disabled_regs(regs))
 503                 local_irq_enable();
 504
 505         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 506
 507         if (error_code & DSISR_KEYFAULT)
 508                 return bad_key_fault_exception(regs, address,
 509                                                get_mm_addr_key(mm, address));
 510
 511         /*
 512          * We want to do this outside mmap_sem, because reading code around nip
 513          * can result in fault, which will cause a deadlock when called with
 514          * mmap_sem held
 515          */
 516         if (is_user)
 517                 flags |= FAULT_FLAG_USER;
 518         if (is_write)
 519                 flags |= FAULT_FLAG_WRITE;
 520         if (is_exec)
 521                 flags |= FAULT_FLAG_INSTRUCTION;
 522
 523         /* When running in the kernel we expect faults to occur only to
 524          * addresses in user space.  All other faults represent errors in the
 525          * kernel and should generate an OOPS.  Unfortunately, in the case of an
 526          * erroneous fault occurring in a code path which already holds mmap_sem
 527          * we will deadlock attempting to validate the fault against the
 528          * address space.  Luckily the kernel only validly references user
 529          * space from well defined areas of code, which are listed in the
 530          * exceptions table.
 531          *
 532          * As the vast majority of faults will be valid we will only perform
 533          * the source reference check when there is a possibility of a deadlock.
 534          * Attempt to lock the address space, if we cannot we then validate the
 535          * source.  If this is invalid we can skip the address space check,
 536          * thus avoiding the deadlock.
 537          */
 538         if (unlikely(!down_read_trylock(&mm->mmap_sem))) {
 539                 if (!is_user && !search_exception_tables(regs->nip))
 540                         return bad_area_nosemaphore(regs, address);
 541
 542 retry:
 543                 down_read(&mm->mmap_sem);
 544         } else {
 545                 /*
 546                  * The above down_read_trylock() might have succeeded in
 547                  * which case we'll have missed the might_sleep() from
 548                  * down_read():
 549                  */
 550                 might_sleep();
 551         }
 552
 553         vma = find_vma(mm, address);
 554         if (unlikely(!vma))
 555                 return bad_area(regs, address);
 556         if (likely(vma->vm_start <= address))
 557                 goto good_area;
 558         if (unlikely(!(vma->vm_flags & VM_GROWSDOWN)))
 559                 return bad_area(regs, address);
 560
 561         /* The stack is being expanded, check if it's valid */
 562         if (unlikely(bad_stack_expansion(regs, address, vma, flags,
 563                                          &must_retry))) {
 564                 if (!must_retry)
 565                         return bad_area(regs, address);
 566
 567                 up_read(&mm->mmap_sem);
 568                 if (fault_in_pages_readable((const char __user *)regs->nip,
 569                                             sizeof(unsigned int)))
 570                         return bad_area_nosemaphore(regs, address);
 571                 goto retry;
 572         }
 573
 574         /* Try to expand it */
 575         if (unlikely(expand_stack(vma, address)))
 576                 return bad_area(regs, address);
 577
 578 good_area:
 579         if (unlikely(access_error(is_write, is_exec, vma)))
 580                 return bad_access(regs, address);
 581
 582         /*
 583          * If for any reason at all we couldn't handle the fault,
 584          * make sure we exit gracefully rather than endlessly redo
 585          * the fault.
 586          */
 587         fault = handle_mm_fault(vma, address, flags);
 588
 589 #ifdef CONFIG_PPC_MEM_KEYS
 590         /*
 591          * we skipped checking for access error due to key earlier.
 592          * Check that using handle_mm_fault error return.
 593          */
 594         if (unlikely(fault & VM_FAULT_SIGSEGV) &&
 595                 !arch_vma_access_permitted(vma, is_write, is_exec, 0)) {
 596
 597                 int pkey = vma_pkey(vma);
 598
 599                 up_read(&mm->mmap_sem);
 600                 return bad_key_fault_exception(regs, address, pkey);
 601         }
 602 #endif /* CONFIG_PPC_MEM_KEYS */
 603
 604         major |= fault & VM_FAULT_MAJOR;
 605
 606         /*
 607          * Handle the retry right now, the mmap_sem has been released in that
 608          * case.
 609          */
 610         if (unlikely(fault & VM_FAULT_RETRY)) {
 611                 /* We retry only once */
 612                 if (flags & FAULT_FLAG_ALLOW_RETRY) {
 613                         /*
 614                          * Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
 615                          * of starvation.
 616                          */
 617                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
 618                         flags |= FAULT_FLAG_TRIED;
 619                         if (!fatal_signal_pending(current))
 620                                 goto retry;
 621                 }
 622
 623                 /*
 624                  * User mode? Just return to handle the fatal exception otherwise
 625                  * return to bad_page_fault
 626                  */
 627                 return is_user ? 0 : SIGBUS;
 628         }
 629
 630         up_read(&current->mm->mmap_sem);
 631
 632         if (unlikely(fault & VM_FAULT_ERROR))
 633                 return mm_fault_error(regs, address, fault);
 634
 635         /*
 636          * Major/minor page fault accounting.
 637          */
 638         if (major) {
 639                 current->maj_flt++;
 640                 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address);
 641                 cmo_account_page_fault();
 642         } else {
 643                 current->min_flt++;
 644                 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address);
 645         }
 646         return 0;
 647 }
 648 NOKPROBE_SYMBOL(__do_page_fault);
 649
 650 int do_page_fault(struct pt_regs *regs, unsigned long address,
 651                   unsigned long error_code)
 652 {
 653         enum ctx_state prev_state = exception_enter();
 654         int rc = __do_page_fault(regs, address, error_code);
 655         exception_exit(prev_state);
 656         return rc;
 657 }
 658 NOKPROBE_SYMBOL(do_page_fault);
 659
 660 /*
 661  * bad_page_fault is called when we have a bad access from the kernel.
 662  * It is called from the DSI and ISI handlers in head.S and from some
 663  * of the procedures in traps.c.
 664  */
 665 void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
 666 {
 667         const struct exception_table_entry *entry;
 668
 669         /* Are we prepared to handle this fault?  */
 670         if ((entry = search_exception_tables(regs->nip)) != NULL) {
 671                 regs->nip = extable_fixup(entry);
 672                 return;
 673         }
 674
 675         /* kernel has accessed a bad area */
 676
 677         switch (TRAP(regs)) {
 678         case 0x300:
 679         case 0x380:
 680         case 0xe00:
 681                 pr_alert("BUG: %s at 0x%08lx\n",
 682                          regs->dar < PAGE_SIZE ? "Kernel NULL pointer dereference" :
 683                          "Unable to handle kernel data access", regs->dar);
 684                 break;
 685         case 0x400:
 686         case 0x480:
 687                 pr_alert("BUG: Unable to handle kernel instruction fetch%s",
 688                          regs->nip < PAGE_SIZE ? " (NULL pointer?)\n" : "\n");
 689                 break;
 690         case 0x600:
 691                 pr_alert("BUG: Unable to handle kernel unaligned access at 0x%08lx\n",
 692                          regs->dar);
 693                 break;
 694         default:
 695                 pr_alert("BUG: Unable to handle unknown paging fault at 0x%08lx\n",
 696                          regs->dar);
 697                 break;
 698         }
 699         printk(KERN_ALERT "Faulting instruction address: 0x%08lx\n",
 700                 regs->nip);
 701
 702         if (task_stack_end_corrupted(current))
 703                 printk(KERN_ALERT "Thread overran stack, or stack corrupted\n");
 704
 705         die("Kernel access of bad area", regs, sig);
 706 }