2 * Copyright (C) 1995 Linus Torvalds
3 * Copyright (C) 2001, 2002 Andi Kleen, SuSE Labs.
4 * Copyright (C) 2008-2009, Red Hat Inc., Ingo Molnar
6 #include <linux/magic.h> /* STACK_END_MAGIC */
7 #include <linux/sched.h> /* test_thread_flag(), ... */
8 #include <linux/kdebug.h> /* oops_begin/end, ... */
9 #include <linux/module.h> /* search_exception_table */
10 #include <linux/bootmem.h> /* max_low_pfn */
11 #include <linux/kprobes.h> /* __kprobes, ... */
12 #include <linux/mmiotrace.h> /* kmmio_handler, ... */
13 #include <linux/perf_counter.h> /* perf_swcounter_event */
15 #include <asm/traps.h> /* dotraplinkage, ... */
16 #include <asm/pgalloc.h> /* pgd_*(), ... */
17 #include <asm/kmemcheck.h> /* kmemcheck_*(), ... */
20 * Page fault error code bits:
22 * bit 0 == 0: no page found 1: protection fault
23 * bit 1 == 0: read access 1: write access
24 * bit 2 == 0: kernel-mode access 1: user-mode access
25 * bit 3 == 1: use of reserved bit detected
26 * bit 4 == 1: fault was an instruction fetch
28 enum x86_pf_error_code {
38 * Returns 0 if mmiotrace is disabled, or if the fault is not
39 * handled by mmiotrace:
41 static inline int __kprobes
42 kmmio_fault(struct pt_regs *regs, unsigned long addr)
44 if (unlikely(is_kmmio_active()))
45 if (kmmio_handler(regs, addr) == 1)
50 static inline int __kprobes notify_page_fault(struct pt_regs *regs)
54 /* kprobe_running() needs smp_processor_id() */
55 if (kprobes_built_in() && !user_mode_vm(regs)) {
57 if (kprobe_running() && kprobe_fault_handler(regs, 14))
70 * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
71 * Check that here and ignore it.
75 * Sometimes the CPU reports invalid exceptions on prefetch.
76 * Check that here and ignore it.
78 * Opcode checker based on code by Richard Brunner.
81 check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr,
82 unsigned char opcode, int *prefetch)
84 unsigned char instr_hi = opcode & 0xf0;
85 unsigned char instr_lo = opcode & 0x0f;
91 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes.
92 * In X86_64 long mode, the CPU will signal invalid
93 * opcode if some of these prefixes are present so
94 * X86_64 will never get here anyway
96 return ((instr_lo & 7) == 0x6);
100 * In AMD64 long mode 0x40..0x4F are valid REX prefixes
101 * Need to figure out under what instruction mode the
102 * instruction was issued. Could check the LDT for lm,
103 * but for now it's good enough to assume that long
104 * mode only uses well known segments or kernel.
106 return (!user_mode(regs)) || (regs->cs == __USER_CS);
109 /* 0x64 thru 0x67 are valid prefixes in all modes. */
110 return (instr_lo & 0xC) == 0x4;
112 /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */
113 return !instr_lo || (instr_lo>>1) == 1;
115 /* Prefetch instruction is 0x0F0D or 0x0F18 */
116 if (probe_kernel_address(instr, opcode))
119 *prefetch = (instr_lo == 0xF) &&
120 (opcode == 0x0D || opcode == 0x18);
128 is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
130 unsigned char *max_instr;
131 unsigned char *instr;
135 * If it was a exec (instruction fetch) fault on NX page, then
136 * do not ignore the fault:
138 if (error_code & PF_INSTR)
141 instr = (void *)convert_ip_to_linear(current, regs);
142 max_instr = instr + 15;
144 if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE)
147 while (instr < max_instr) {
148 unsigned char opcode;
150 if (probe_kernel_address(instr, opcode))
155 if (!check_prefetch_opcode(regs, instr, opcode, &prefetch))
162 force_sig_info_fault(int si_signo, int si_code, unsigned long address,
163 struct task_struct *tsk)
167 info.si_signo = si_signo;
169 info.si_code = si_code;
170 info.si_addr = (void __user *)address;
172 force_sig_info(si_signo, &info, tsk);
175 DEFINE_SPINLOCK(pgd_lock);
179 static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
181 unsigned index = pgd_index(address);
187 pgd_k = init_mm.pgd + index;
189 if (!pgd_present(*pgd_k))
193 * set_pgd(pgd, *pgd_k); here would be useless on PAE
194 * and redundant with the set_pmd() on non-PAE. As would
197 pud = pud_offset(pgd, address);
198 pud_k = pud_offset(pgd_k, address);
199 if (!pud_present(*pud_k))
202 pmd = pmd_offset(pud, address);
203 pmd_k = pmd_offset(pud_k, address);
204 if (!pmd_present(*pmd_k))
207 if (!pmd_present(*pmd))
208 set_pmd(pmd, *pmd_k);
210 BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k));
215 void vmalloc_sync_all(void)
217 unsigned long address;
219 if (SHARED_KERNEL_PMD)
222 for (address = VMALLOC_START & PMD_MASK;
223 address >= TASK_SIZE && address < FIXADDR_TOP;
224 address += PMD_SIZE) {
229 spin_lock_irqsave(&pgd_lock, flags);
230 list_for_each_entry(page, &pgd_list, lru) {
231 if (!vmalloc_sync_one(page_address(page), address))
234 spin_unlock_irqrestore(&pgd_lock, flags);
241 * Handle a fault on the vmalloc or module mapping area
243 static noinline __kprobes int vmalloc_fault(unsigned long address)
245 unsigned long pgd_paddr;
249 /* Make sure we are in vmalloc area: */
250 if (!(address >= VMALLOC_START && address < VMALLOC_END))
254 * Synchronize this task's top level page-table
255 * with the 'reference' page table.
257 * Do _not_ use "current" here. We might be inside
258 * an interrupt in the middle of a task switch..
260 pgd_paddr = read_cr3();
261 pmd_k = vmalloc_sync_one(__va(pgd_paddr), address);
265 pte_k = pte_offset_kernel(pmd_k, address);
266 if (!pte_present(*pte_k))
273 * Did it hit the DOS screen memory VA from vm86 mode?
276 check_v8086_mode(struct pt_regs *regs, unsigned long address,
277 struct task_struct *tsk)
281 if (!v8086_mode(regs))
284 bit = (address - 0xA0000) >> PAGE_SHIFT;
286 tsk->thread.screen_bitmap |= 1 << bit;
289 static void dump_pagetable(unsigned long address)
291 __typeof__(pte_val(__pte(0))) page;
294 page = ((__typeof__(page) *) __va(page))[address >> PGDIR_SHIFT];
296 #ifdef CONFIG_X86_PAE
297 printk("*pdpt = %016Lx ", page);
298 if ((page >> PAGE_SHIFT) < max_low_pfn
299 && page & _PAGE_PRESENT) {
301 page = ((__typeof__(page) *) __va(page))[(address >> PMD_SHIFT)
302 & (PTRS_PER_PMD - 1)];
303 printk(KERN_CONT "*pde = %016Lx ", page);
307 printk("*pde = %08lx ", page);
311 * We must not directly access the pte in the highpte
312 * case if the page table is located in highmem.
313 * And let's rather not kmap-atomic the pte, just in case
314 * it's allocated already:
316 if ((page >> PAGE_SHIFT) < max_low_pfn
317 && (page & _PAGE_PRESENT)
318 && !(page & _PAGE_PSE)) {
321 page = ((__typeof__(page) *) __va(page))[(address >> PAGE_SHIFT)
322 & (PTRS_PER_PTE - 1)];
323 printk("*pte = %0*Lx ", sizeof(page)*2, (u64)page);
329 #else /* CONFIG_X86_64: */
331 void vmalloc_sync_all(void)
333 unsigned long address;
335 for (address = VMALLOC_START & PGDIR_MASK; address <= VMALLOC_END;
336 address += PGDIR_SIZE) {
338 const pgd_t *pgd_ref = pgd_offset_k(address);
342 if (pgd_none(*pgd_ref))
345 spin_lock_irqsave(&pgd_lock, flags);
346 list_for_each_entry(page, &pgd_list, lru) {
348 pgd = (pgd_t *)page_address(page) + pgd_index(address);
350 set_pgd(pgd, *pgd_ref);
352 BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref));
354 spin_unlock_irqrestore(&pgd_lock, flags);
361 * Handle a fault on the vmalloc area
363 * This assumes no large pages in there.
365 static noinline __kprobes int vmalloc_fault(unsigned long address)
367 pgd_t *pgd, *pgd_ref;
368 pud_t *pud, *pud_ref;
369 pmd_t *pmd, *pmd_ref;
370 pte_t *pte, *pte_ref;
372 /* Make sure we are in vmalloc area: */
373 if (!(address >= VMALLOC_START && address < VMALLOC_END))
377 * Copy kernel mappings over when needed. This can also
378 * happen within a race in page table update. In the later
381 pgd = pgd_offset(current->active_mm, address);
382 pgd_ref = pgd_offset_k(address);
383 if (pgd_none(*pgd_ref))
387 set_pgd(pgd, *pgd_ref);
389 BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref));
392 * Below here mismatches are bugs because these lower tables
396 pud = pud_offset(pgd, address);
397 pud_ref = pud_offset(pgd_ref, address);
398 if (pud_none(*pud_ref))
401 if (pud_none(*pud) || pud_page_vaddr(*pud) != pud_page_vaddr(*pud_ref))
404 pmd = pmd_offset(pud, address);
405 pmd_ref = pmd_offset(pud_ref, address);
406 if (pmd_none(*pmd_ref))
409 if (pmd_none(*pmd) || pmd_page(*pmd) != pmd_page(*pmd_ref))
412 pte_ref = pte_offset_kernel(pmd_ref, address);
413 if (!pte_present(*pte_ref))
416 pte = pte_offset_kernel(pmd, address);
419 * Don't use pte_page here, because the mappings can point
420 * outside mem_map, and the NUMA hash lookup cannot handle
423 if (!pte_present(*pte) || pte_pfn(*pte) != pte_pfn(*pte_ref))
429 static const char errata93_warning[] =
431 "******* Your BIOS seems to not contain a fix for K8 errata #93\n"
432 "******* Working around it, but it may cause SEGVs or burn power.\n"
433 "******* Please consider a BIOS update.\n"
434 "******* Disabling USB legacy in the BIOS may also help.\n";
437 * No vm86 mode in 64-bit mode:
440 check_v8086_mode(struct pt_regs *regs, unsigned long address,
441 struct task_struct *tsk)
445 static int bad_address(void *p)
449 return probe_kernel_address((unsigned long *)p, dummy);
452 static void dump_pagetable(unsigned long address)
459 pgd = (pgd_t *)read_cr3();
461 pgd = __va((unsigned long)pgd & PHYSICAL_PAGE_MASK);
463 pgd += pgd_index(address);
464 if (bad_address(pgd))
467 printk("PGD %lx ", pgd_val(*pgd));
469 if (!pgd_present(*pgd))
472 pud = pud_offset(pgd, address);
473 if (bad_address(pud))
476 printk("PUD %lx ", pud_val(*pud));
477 if (!pud_present(*pud) || pud_large(*pud))
480 pmd = pmd_offset(pud, address);
481 if (bad_address(pmd))
484 printk("PMD %lx ", pmd_val(*pmd));
485 if (!pmd_present(*pmd) || pmd_large(*pmd))
488 pte = pte_offset_kernel(pmd, address);
489 if (bad_address(pte))
492 printk("PTE %lx", pte_val(*pte));
500 #endif /* CONFIG_X86_64 */
503 * Workaround for K8 erratum #93 & buggy BIOS.
505 * BIOS SMM functions are required to use a specific workaround
506 * to avoid corruption of the 64bit RIP register on C stepping K8.
508 * A lot of BIOS that didn't get tested properly miss this.
510 * The OS sees this as a page fault with the upper 32bits of RIP cleared.
511 * Try to work around it here.
513 * Note we only handle faults in kernel here.
514 * Does nothing on 32-bit.
516 static int is_errata93(struct pt_regs *regs, unsigned long address)
519 if (address != regs->ip)
522 if ((address >> 32) != 0)
525 address |= 0xffffffffUL << 32;
526 if ((address >= (u64)_stext && address <= (u64)_etext) ||
527 (address >= MODULES_VADDR && address <= MODULES_END)) {
528 printk_once(errata93_warning);
537 * Work around K8 erratum #100 K8 in compat mode occasionally jumps
538 * to illegal addresses >4GB.
540 * We catch this in the page fault handler because these addresses
541 * are not reachable. Just detect this case and return. Any code
542 * segment in LDT is compatibility mode.
544 static int is_errata100(struct pt_regs *regs, unsigned long address)
547 if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32))
553 static int is_f00f_bug(struct pt_regs *regs, unsigned long address)
555 #ifdef CONFIG_X86_F00F_BUG
559 * Pentium F0 0F C7 C8 bug workaround:
561 if (boot_cpu_data.f00f_bug) {
562 nr = (address - idt_descr.address) >> 3;
565 do_invalid_op(regs, 0);
573 static const char nx_warning[] = KERN_CRIT
574 "kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n";
577 show_fault_oops(struct pt_regs *regs, unsigned long error_code,
578 unsigned long address)
580 if (!oops_may_print())
583 if (error_code & PF_INSTR) {
586 pte_t *pte = lookup_address(address, &level);
588 if (pte && pte_present(*pte) && !pte_exec(*pte))
589 printk(nx_warning, current_uid());
592 printk(KERN_ALERT "BUG: unable to handle kernel ");
593 if (address < PAGE_SIZE)
594 printk(KERN_CONT "NULL pointer dereference");
596 printk(KERN_CONT "paging request");
598 printk(KERN_CONT " at %p\n", (void *) address);
599 printk(KERN_ALERT "IP:");
600 printk_address(regs->ip, 1);
602 dump_pagetable(address);
606 pgtable_bad(struct pt_regs *regs, unsigned long error_code,
607 unsigned long address)
609 struct task_struct *tsk;
613 flags = oops_begin();
617 printk(KERN_ALERT "%s: Corrupted page table at address %lx\n",
619 dump_pagetable(address);
621 tsk->thread.cr2 = address;
622 tsk->thread.trap_no = 14;
623 tsk->thread.error_code = error_code;
625 if (__die("Bad pagetable", regs, error_code))
628 oops_end(flags, regs, sig);
632 no_context(struct pt_regs *regs, unsigned long error_code,
633 unsigned long address)
635 struct task_struct *tsk = current;
636 unsigned long *stackend;
640 /* Are we prepared to handle this kernel fault? */
641 if (fixup_exception(regs))
647 * Valid to do another page fault here, because if this fault
648 * had been triggered by is_prefetch fixup_exception would have
653 * Hall of shame of CPU/BIOS bugs.
655 if (is_prefetch(regs, error_code, address))
658 if (is_errata93(regs, address))
662 * Oops. The kernel tried to access some bad page. We'll have to
663 * terminate things with extreme prejudice:
665 flags = oops_begin();
667 show_fault_oops(regs, error_code, address);
669 stackend = end_of_stack(tsk);
670 if (*stackend != STACK_END_MAGIC)
671 printk(KERN_ALERT "Thread overran stack, or stack corrupted\n");
673 tsk->thread.cr2 = address;
674 tsk->thread.trap_no = 14;
675 tsk->thread.error_code = error_code;
678 if (__die("Oops", regs, error_code))
681 /* Executive summary in case the body of the oops scrolled away */
682 printk(KERN_EMERG "CR2: %016lx\n", address);
684 oops_end(flags, regs, sig);
688 * Print out info about fatal segfaults, if the show_unhandled_signals
692 show_signal_msg(struct pt_regs *regs, unsigned long error_code,
693 unsigned long address, struct task_struct *tsk)
695 if (!unhandled_signal(tsk, SIGSEGV))
698 if (!printk_ratelimit())
701 printk("%s%s[%d]: segfault at %lx ip %p sp %p error %lx",
702 task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
703 tsk->comm, task_pid_nr(tsk), address,
704 (void *)regs->ip, (void *)regs->sp, error_code);
706 print_vma_addr(KERN_CONT " in ", regs->ip);
708 printk(KERN_CONT "\n");
712 __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
713 unsigned long address, int si_code)
715 struct task_struct *tsk = current;
717 /* User mode accesses just cause a SIGSEGV */
718 if (error_code & PF_USER) {
720 * It's possible to have interrupts off here:
725 * Valid to do another page fault here because this one came
728 if (is_prefetch(regs, error_code, address))
731 if (is_errata100(regs, address))
734 if (unlikely(show_unhandled_signals))
735 show_signal_msg(regs, error_code, address, tsk);
737 /* Kernel addresses are always protection faults: */
738 tsk->thread.cr2 = address;
739 tsk->thread.error_code = error_code | (address >= TASK_SIZE);
740 tsk->thread.trap_no = 14;
742 force_sig_info_fault(SIGSEGV, si_code, address, tsk);
747 if (is_f00f_bug(regs, address))
750 no_context(regs, error_code, address);
754 bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
755 unsigned long address)
757 __bad_area_nosemaphore(regs, error_code, address, SEGV_MAPERR);
761 __bad_area(struct pt_regs *regs, unsigned long error_code,
762 unsigned long address, int si_code)
764 struct mm_struct *mm = current->mm;
767 * Something tried to access memory that isn't in our memory map..
768 * Fix it, but check if it's kernel or user first..
770 up_read(&mm->mmap_sem);
772 __bad_area_nosemaphore(regs, error_code, address, si_code);
776 bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address)
778 __bad_area(regs, error_code, address, SEGV_MAPERR);
782 bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
783 unsigned long address)
785 __bad_area(regs, error_code, address, SEGV_ACCERR);
788 /* TODO: fixup for "mm-invoke-oom-killer-from-page-fault.patch" */
790 out_of_memory(struct pt_regs *regs, unsigned long error_code,
791 unsigned long address)
794 * We ran out of memory, call the OOM killer, and return the userspace
795 * (which will retry the fault, or kill us if we got oom-killed):
797 up_read(¤t->mm->mmap_sem);
799 pagefault_out_of_memory();
803 do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address)
805 struct task_struct *tsk = current;
806 struct mm_struct *mm = tsk->mm;
808 up_read(&mm->mmap_sem);
810 /* Kernel mode? Handle exceptions or die: */
811 if (!(error_code & PF_USER))
812 no_context(regs, error_code, address);
814 /* User-space => ok to do another page fault: */
815 if (is_prefetch(regs, error_code, address))
818 tsk->thread.cr2 = address;
819 tsk->thread.error_code = error_code;
820 tsk->thread.trap_no = 14;
822 force_sig_info_fault(SIGBUS, BUS_ADRERR, address, tsk);
826 mm_fault_error(struct pt_regs *regs, unsigned long error_code,
827 unsigned long address, unsigned int fault)
829 if (fault & VM_FAULT_OOM) {
830 out_of_memory(regs, error_code, address);
832 if (fault & VM_FAULT_SIGBUS)
833 do_sigbus(regs, error_code, address);
839 static int spurious_fault_check(unsigned long error_code, pte_t *pte)
841 if ((error_code & PF_WRITE) && !pte_write(*pte))
844 if ((error_code & PF_INSTR) && !pte_exec(*pte))
851 * Handle a spurious fault caused by a stale TLB entry.
853 * This allows us to lazily refresh the TLB when increasing the
854 * permissions of a kernel page (RO -> RW or NX -> X). Doing it
855 * eagerly is very expensive since that implies doing a full
856 * cross-processor TLB flush, even if no stale TLB entries exist
857 * on other processors.
859 * There are no security implications to leaving a stale TLB when
860 * increasing the permissions on a page.
862 static noinline __kprobes int
863 spurious_fault(unsigned long error_code, unsigned long address)
871 /* Reserved-bit violation or user access to kernel space? */
872 if (error_code & (PF_USER | PF_RSVD))
875 pgd = init_mm.pgd + pgd_index(address);
876 if (!pgd_present(*pgd))
879 pud = pud_offset(pgd, address);
880 if (!pud_present(*pud))
884 return spurious_fault_check(error_code, (pte_t *) pud);
886 pmd = pmd_offset(pud, address);
887 if (!pmd_present(*pmd))
891 return spurious_fault_check(error_code, (pte_t *) pmd);
893 pte = pte_offset_kernel(pmd, address);
894 if (!pte_present(*pte))
897 ret = spurious_fault_check(error_code, pte);
902 * Make sure we have permissions in PMD.
903 * If not, then there's a bug in the page tables:
905 ret = spurious_fault_check(error_code, (pte_t *) pmd);
906 WARN_ONCE(!ret, "PMD has incorrect permission bits\n");
911 int show_unhandled_signals = 1;
914 access_error(unsigned long error_code, int write, struct vm_area_struct *vma)
917 /* write, present and write, not present: */
918 if (unlikely(!(vma->vm_flags & VM_WRITE)))
924 if (unlikely(error_code & PF_PROT))
927 /* read, not present: */
928 if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))))
934 static int fault_in_kernel_space(unsigned long address)
936 return address >= TASK_SIZE_MAX;
940 * This routine handles page faults. It determines the address,
941 * and the problem, and then passes it off to one of the appropriate
944 dotraplinkage void __kprobes
945 do_page_fault(struct pt_regs *regs, unsigned long error_code)
947 struct vm_area_struct *vma;
948 struct task_struct *tsk;
949 unsigned long address;
950 struct mm_struct *mm;
957 /* Get the faulting address: */
958 address = read_cr2();
961 * Detect and handle instructions that would cause a page fault for
962 * both a tracked kernel page and a userspace page.
964 if (kmemcheck_active(regs))
965 kmemcheck_hide(regs);
966 prefetchw(&mm->mmap_sem);
968 if (unlikely(kmmio_fault(regs, address)))
972 * We fault-in kernel-space virtual memory on-demand. The
973 * 'reference' page table is init_mm.pgd.
975 * NOTE! We MUST NOT take any locks for this case. We may
976 * be in an interrupt or a critical region, and should
977 * only copy the information from the master page table,
980 * This verifies that the fault happens in kernel space
981 * (error_code & 4) == 0, and that the fault was not a
982 * protection error (error_code & 9) == 0.
984 if (unlikely(fault_in_kernel_space(address))) {
985 if (!(error_code & (PF_RSVD | PF_USER | PF_PROT))) {
986 if (vmalloc_fault(address) >= 0)
989 if (kmemcheck_fault(regs, address, error_code))
993 /* Can handle a stale RO->RW TLB: */
994 if (spurious_fault(error_code, address))
997 /* kprobes don't want to hook the spurious faults: */
998 if (notify_page_fault(regs))
1001 * Don't take the mm semaphore here. If we fixup a prefetch
1002 * fault we could otherwise deadlock:
1004 bad_area_nosemaphore(regs, error_code, address);
1009 /* kprobes don't want to hook the spurious faults: */
1010 if (unlikely(notify_page_fault(regs)))
1013 * It's safe to allow irq's after cr2 has been saved and the
1014 * vmalloc fault has been handled.
1016 * User-mode registers count as a user access even for any
1017 * potential system fault or CPU buglet:
1019 if (user_mode_vm(regs)) {
1021 error_code |= PF_USER;
1023 if (regs->flags & X86_EFLAGS_IF)
1027 if (unlikely(error_code & PF_RSVD))
1028 pgtable_bad(regs, error_code, address);
1030 perf_swcounter_event(PERF_COUNT_SW_PAGE_FAULTS, 1, 0, regs, address);
1033 * If we're in an interrupt, have no user context or are running
1034 * in an atomic region then we must not take the fault:
1036 if (unlikely(in_atomic() || !mm)) {
1037 bad_area_nosemaphore(regs, error_code, address);
1042 * When running in the kernel we expect faults to occur only to
1043 * addresses in user space. All other faults represent errors in
1044 * the kernel and should generate an OOPS. Unfortunately, in the
1045 * case of an erroneous fault occurring in a code path which already
1046 * holds mmap_sem we will deadlock attempting to validate the fault
1047 * against the address space. Luckily the kernel only validly
1048 * references user space from well defined areas of code, which are
1049 * listed in the exceptions table.
1051 * As the vast majority of faults will be valid we will only perform
1052 * the source reference check when there is a possibility of a
1053 * deadlock. Attempt to lock the address space, if we cannot we then
1054 * validate the source. If this is invalid we can skip the address
1055 * space check, thus avoiding the deadlock:
1057 if (unlikely(!down_read_trylock(&mm->mmap_sem))) {
1058 if ((error_code & PF_USER) == 0 &&
1059 !search_exception_tables(regs->ip)) {
1060 bad_area_nosemaphore(regs, error_code, address);
1063 down_read(&mm->mmap_sem);
1066 * The above down_read_trylock() might have succeeded in
1067 * which case we'll have missed the might_sleep() from
1073 vma = find_vma(mm, address);
1074 if (unlikely(!vma)) {
1075 bad_area(regs, error_code, address);
1078 if (likely(vma->vm_start <= address))
1080 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
1081 bad_area(regs, error_code, address);
1084 if (error_code & PF_USER) {
1086 * Accessing the stack below %sp is always a bug.
1087 * The large cushion allows instructions like enter
1088 * and pusha to work. ("enter $65535, $31" pushes
1089 * 32 pointers and then decrements %sp by 65535.)
1091 if (unlikely(address + 65536 + 32 * sizeof(unsigned long) < regs->sp)) {
1092 bad_area(regs, error_code, address);
1096 if (unlikely(expand_stack(vma, address))) {
1097 bad_area(regs, error_code, address);
1102 * Ok, we have a good vm_area for this memory access, so
1103 * we can handle it..
1106 write = error_code & PF_WRITE;
1108 if (unlikely(access_error(error_code, write, vma))) {
1109 bad_area_access_error(regs, error_code, address);
1114 * If for any reason at all we couldn't handle the fault,
1115 * make sure we exit gracefully rather than endlessly redo
1118 fault = handle_mm_fault(mm, vma, address, write ? FAULT_FLAG_WRITE : 0);
1120 if (unlikely(fault & VM_FAULT_ERROR)) {
1121 mm_fault_error(regs, error_code, address, fault);
1125 if (fault & VM_FAULT_MAJOR) {
1127 perf_swcounter_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, 0,
1131 perf_swcounter_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, 0,
1135 check_v8086_mode(regs, address, tsk);
1137 up_read(&mm->mmap_sem);