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/sched.h> /* test_thread_flag(), ... */
7 #include <linux/kdebug.h> /* oops_begin/end, ... */
8 #include <linux/module.h> /* search_exception_table */
9 #include <linux/bootmem.h> /* max_low_pfn */
10 #include <linux/kprobes.h> /* NOKPROBE_SYMBOL, ... */
11 #include <linux/mmiotrace.h> /* kmmio_handler, ... */
12 #include <linux/perf_event.h> /* perf_sw_event */
13 #include <linux/hugetlb.h> /* hstate_index_to_shift */
14 #include <linux/prefetch.h> /* prefetchw */
15 #include <linux/context_tracking.h> /* exception_enter(), ... */
16 #include <linux/uaccess.h> /* faulthandler_disabled() */
18 #include <asm/traps.h> /* dotraplinkage, ... */
19 #include <asm/pgalloc.h> /* pgd_*(), ... */
20 #include <asm/kmemcheck.h> /* kmemcheck_*(), ... */
21 #include <asm/fixmap.h> /* VSYSCALL_ADDR */
22 #include <asm/vsyscall.h> /* emulate_vsyscall */
23 #include <asm/vm86.h> /* struct vm86 */
25 #define CREATE_TRACE_POINTS
26 #include <asm/trace/exceptions.h>
29 * Page fault error code bits:
31 * bit 0 == 0: no page found 1: protection fault
32 * bit 1 == 0: read access 1: write access
33 * bit 2 == 0: kernel-mode access 1: user-mode access
34 * bit 3 == 1: use of reserved bit detected
35 * bit 4 == 1: fault was an instruction fetch
37 enum x86_pf_error_code {
47 * Returns 0 if mmiotrace is disabled, or if the fault is not
48 * handled by mmiotrace:
50 static nokprobe_inline int
51 kmmio_fault(struct pt_regs *regs, unsigned long addr)
53 if (unlikely(is_kmmio_active()))
54 if (kmmio_handler(regs, addr) == 1)
59 static nokprobe_inline int kprobes_fault(struct pt_regs *regs)
63 /* kprobe_running() needs smp_processor_id() */
64 if (kprobes_built_in() && !user_mode(regs)) {
66 if (kprobe_running() && kprobe_fault_handler(regs, 14))
79 * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
80 * Check that here and ignore it.
84 * Sometimes the CPU reports invalid exceptions on prefetch.
85 * Check that here and ignore it.
87 * Opcode checker based on code by Richard Brunner.
90 check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr,
91 unsigned char opcode, int *prefetch)
93 unsigned char instr_hi = opcode & 0xf0;
94 unsigned char instr_lo = opcode & 0x0f;
100 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes.
101 * In X86_64 long mode, the CPU will signal invalid
102 * opcode if some of these prefixes are present so
103 * X86_64 will never get here anyway
105 return ((instr_lo & 7) == 0x6);
109 * In AMD64 long mode 0x40..0x4F are valid REX prefixes
110 * Need to figure out under what instruction mode the
111 * instruction was issued. Could check the LDT for lm,
112 * but for now it's good enough to assume that long
113 * mode only uses well known segments or kernel.
115 return (!user_mode(regs) || user_64bit_mode(regs));
118 /* 0x64 thru 0x67 are valid prefixes in all modes. */
119 return (instr_lo & 0xC) == 0x4;
121 /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */
122 return !instr_lo || (instr_lo>>1) == 1;
124 /* Prefetch instruction is 0x0F0D or 0x0F18 */
125 if (probe_kernel_address(instr, opcode))
128 *prefetch = (instr_lo == 0xF) &&
129 (opcode == 0x0D || opcode == 0x18);
137 is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
139 unsigned char *max_instr;
140 unsigned char *instr;
144 * If it was a exec (instruction fetch) fault on NX page, then
145 * do not ignore the fault:
147 if (error_code & PF_INSTR)
150 instr = (void *)convert_ip_to_linear(current, regs);
151 max_instr = instr + 15;
153 if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE_MAX)
156 while (instr < max_instr) {
157 unsigned char opcode;
159 if (probe_kernel_address(instr, opcode))
164 if (!check_prefetch_opcode(regs, instr, opcode, &prefetch))
171 force_sig_info_fault(int si_signo, int si_code, unsigned long address,
172 struct task_struct *tsk, int fault)
177 info.si_signo = si_signo;
179 info.si_code = si_code;
180 info.si_addr = (void __user *)address;
181 if (fault & VM_FAULT_HWPOISON_LARGE)
182 lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
183 if (fault & VM_FAULT_HWPOISON)
185 info.si_addr_lsb = lsb;
187 force_sig_info(si_signo, &info, tsk);
190 DEFINE_SPINLOCK(pgd_lock);
194 static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
196 unsigned index = pgd_index(address);
202 pgd_k = init_mm.pgd + index;
204 if (!pgd_present(*pgd_k))
208 * set_pgd(pgd, *pgd_k); here would be useless on PAE
209 * and redundant with the set_pmd() on non-PAE. As would
212 pud = pud_offset(pgd, address);
213 pud_k = pud_offset(pgd_k, address);
214 if (!pud_present(*pud_k))
217 pmd = pmd_offset(pud, address);
218 pmd_k = pmd_offset(pud_k, address);
219 if (!pmd_present(*pmd_k))
222 if (!pmd_present(*pmd))
223 set_pmd(pmd, *pmd_k);
225 BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k));
230 void vmalloc_sync_all(void)
232 unsigned long address;
234 if (SHARED_KERNEL_PMD)
237 for (address = VMALLOC_START & PMD_MASK;
238 address >= TASK_SIZE && address < FIXADDR_TOP;
239 address += PMD_SIZE) {
242 spin_lock(&pgd_lock);
243 list_for_each_entry(page, &pgd_list, lru) {
244 spinlock_t *pgt_lock;
247 /* the pgt_lock only for Xen */
248 pgt_lock = &pgd_page_get_mm(page)->page_table_lock;
251 ret = vmalloc_sync_one(page_address(page), address);
252 spin_unlock(pgt_lock);
257 spin_unlock(&pgd_lock);
264 * Handle a fault on the vmalloc or module mapping area
266 static noinline int vmalloc_fault(unsigned long address)
268 unsigned long pgd_paddr;
272 /* Make sure we are in vmalloc area: */
273 if (!(address >= VMALLOC_START && address < VMALLOC_END))
276 WARN_ON_ONCE(in_nmi());
279 * Synchronize this task's top level page-table
280 * with the 'reference' page table.
282 * Do _not_ use "current" here. We might be inside
283 * an interrupt in the middle of a task switch..
285 pgd_paddr = read_cr3();
286 pmd_k = vmalloc_sync_one(__va(pgd_paddr), address);
290 if (pmd_huge(*pmd_k))
293 pte_k = pte_offset_kernel(pmd_k, address);
294 if (!pte_present(*pte_k))
299 NOKPROBE_SYMBOL(vmalloc_fault);
302 * Did it hit the DOS screen memory VA from vm86 mode?
305 check_v8086_mode(struct pt_regs *regs, unsigned long address,
306 struct task_struct *tsk)
311 if (!v8086_mode(regs) || !tsk->thread.vm86)
314 bit = (address - 0xA0000) >> PAGE_SHIFT;
316 tsk->thread.vm86->screen_bitmap |= 1 << bit;
320 static bool low_pfn(unsigned long pfn)
322 return pfn < max_low_pfn;
325 static void dump_pagetable(unsigned long address)
327 pgd_t *base = __va(read_cr3());
328 pgd_t *pgd = &base[pgd_index(address)];
332 #ifdef CONFIG_X86_PAE
333 printk("*pdpt = %016Lx ", pgd_val(*pgd));
334 if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd))
337 pmd = pmd_offset(pud_offset(pgd, address), address);
338 printk(KERN_CONT "*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd));
341 * We must not directly access the pte in the highpte
342 * case if the page table is located in highmem.
343 * And let's rather not kmap-atomic the pte, just in case
344 * it's allocated already:
346 if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_large(*pmd))
349 pte = pte_offset_kernel(pmd, address);
350 printk("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte));
355 #else /* CONFIG_X86_64: */
357 void vmalloc_sync_all(void)
359 sync_global_pgds(VMALLOC_START & PGDIR_MASK, VMALLOC_END, 0);
365 * Handle a fault on the vmalloc area
367 static noinline int vmalloc_fault(unsigned long address)
369 pgd_t *pgd, *pgd_ref;
370 pud_t *pud, *pud_ref;
371 pmd_t *pmd, *pmd_ref;
372 pte_t *pte, *pte_ref;
374 /* Make sure we are in vmalloc area: */
375 if (!(address >= VMALLOC_START && address < VMALLOC_END))
378 WARN_ON_ONCE(in_nmi());
381 * Copy kernel mappings over when needed. This can also
382 * happen within a race in page table update. In the later
385 pgd = pgd_offset(current->active_mm, address);
386 pgd_ref = pgd_offset_k(address);
387 if (pgd_none(*pgd_ref))
390 if (pgd_none(*pgd)) {
391 set_pgd(pgd, *pgd_ref);
392 arch_flush_lazy_mmu_mode();
394 BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref));
398 * Below here mismatches are bugs because these lower tables
402 pud = pud_offset(pgd, address);
403 pud_ref = pud_offset(pgd_ref, address);
404 if (pud_none(*pud_ref))
407 if (pud_none(*pud) || pud_pfn(*pud) != pud_pfn(*pud_ref))
413 pmd = pmd_offset(pud, address);
414 pmd_ref = pmd_offset(pud_ref, address);
415 if (pmd_none(*pmd_ref))
418 if (pmd_none(*pmd) || pmd_pfn(*pmd) != pmd_pfn(*pmd_ref))
424 pte_ref = pte_offset_kernel(pmd_ref, address);
425 if (!pte_present(*pte_ref))
428 pte = pte_offset_kernel(pmd, address);
431 * Don't use pte_page here, because the mappings can point
432 * outside mem_map, and the NUMA hash lookup cannot handle
435 if (!pte_present(*pte) || pte_pfn(*pte) != pte_pfn(*pte_ref))
440 NOKPROBE_SYMBOL(vmalloc_fault);
442 #ifdef CONFIG_CPU_SUP_AMD
443 static const char errata93_warning[] =
445 "******* Your BIOS seems to not contain a fix for K8 errata #93\n"
446 "******* Working around it, but it may cause SEGVs or burn power.\n"
447 "******* Please consider a BIOS update.\n"
448 "******* Disabling USB legacy in the BIOS may also help.\n";
452 * No vm86 mode in 64-bit mode:
455 check_v8086_mode(struct pt_regs *regs, unsigned long address,
456 struct task_struct *tsk)
460 static int bad_address(void *p)
464 return probe_kernel_address((unsigned long *)p, dummy);
467 static void dump_pagetable(unsigned long address)
469 pgd_t *base = __va(read_cr3() & PHYSICAL_PAGE_MASK);
470 pgd_t *pgd = base + pgd_index(address);
475 if (bad_address(pgd))
478 printk("PGD %lx ", pgd_val(*pgd));
480 if (!pgd_present(*pgd))
483 pud = pud_offset(pgd, address);
484 if (bad_address(pud))
487 printk("PUD %lx ", pud_val(*pud));
488 if (!pud_present(*pud) || pud_large(*pud))
491 pmd = pmd_offset(pud, address);
492 if (bad_address(pmd))
495 printk("PMD %lx ", pmd_val(*pmd));
496 if (!pmd_present(*pmd) || pmd_large(*pmd))
499 pte = pte_offset_kernel(pmd, address);
500 if (bad_address(pte))
503 printk("PTE %lx", pte_val(*pte));
511 #endif /* CONFIG_X86_64 */
514 * Workaround for K8 erratum #93 & buggy BIOS.
516 * BIOS SMM functions are required to use a specific workaround
517 * to avoid corruption of the 64bit RIP register on C stepping K8.
519 * A lot of BIOS that didn't get tested properly miss this.
521 * The OS sees this as a page fault with the upper 32bits of RIP cleared.
522 * Try to work around it here.
524 * Note we only handle faults in kernel here.
525 * Does nothing on 32-bit.
527 static int is_errata93(struct pt_regs *regs, unsigned long address)
529 #if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD)
530 if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD
531 || boot_cpu_data.x86 != 0xf)
534 if (address != regs->ip)
537 if ((address >> 32) != 0)
540 address |= 0xffffffffUL << 32;
541 if ((address >= (u64)_stext && address <= (u64)_etext) ||
542 (address >= MODULES_VADDR && address <= MODULES_END)) {
543 printk_once(errata93_warning);
552 * Work around K8 erratum #100 K8 in compat mode occasionally jumps
553 * to illegal addresses >4GB.
555 * We catch this in the page fault handler because these addresses
556 * are not reachable. Just detect this case and return. Any code
557 * segment in LDT is compatibility mode.
559 static int is_errata100(struct pt_regs *regs, unsigned long address)
562 if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32))
568 static int is_f00f_bug(struct pt_regs *regs, unsigned long address)
570 #ifdef CONFIG_X86_F00F_BUG
574 * Pentium F0 0F C7 C8 bug workaround:
576 if (boot_cpu_has_bug(X86_BUG_F00F)) {
577 nr = (address - idt_descr.address) >> 3;
580 do_invalid_op(regs, 0);
588 static const char nx_warning[] = KERN_CRIT
589 "kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n";
590 static const char smep_warning[] = KERN_CRIT
591 "unable to execute userspace code (SMEP?) (uid: %d)\n";
594 show_fault_oops(struct pt_regs *regs, unsigned long error_code,
595 unsigned long address)
597 if (!oops_may_print())
600 if (error_code & PF_INSTR) {
605 pgd = __va(read_cr3() & PHYSICAL_PAGE_MASK);
606 pgd += pgd_index(address);
608 pte = lookup_address_in_pgd(pgd, address, &level);
610 if (pte && pte_present(*pte) && !pte_exec(*pte))
611 printk(nx_warning, from_kuid(&init_user_ns, current_uid()));
612 if (pte && pte_present(*pte) && pte_exec(*pte) &&
613 (pgd_flags(*pgd) & _PAGE_USER) &&
614 (__read_cr4() & X86_CR4_SMEP))
615 printk(smep_warning, from_kuid(&init_user_ns, current_uid()));
618 printk(KERN_ALERT "BUG: unable to handle kernel ");
619 if (address < PAGE_SIZE)
620 printk(KERN_CONT "NULL pointer dereference");
622 printk(KERN_CONT "paging request");
624 printk(KERN_CONT " at %p\n", (void *) address);
625 printk(KERN_ALERT "IP:");
626 printk_address(regs->ip);
628 dump_pagetable(address);
632 pgtable_bad(struct pt_regs *regs, unsigned long error_code,
633 unsigned long address)
635 struct task_struct *tsk;
639 flags = oops_begin();
643 printk(KERN_ALERT "%s: Corrupted page table at address %lx\n",
645 dump_pagetable(address);
647 tsk->thread.cr2 = address;
648 tsk->thread.trap_nr = X86_TRAP_PF;
649 tsk->thread.error_code = error_code;
651 if (__die("Bad pagetable", regs, error_code))
654 oops_end(flags, regs, sig);
658 no_context(struct pt_regs *regs, unsigned long error_code,
659 unsigned long address, int signal, int si_code)
661 struct task_struct *tsk = current;
665 /* Are we prepared to handle this kernel fault? */
666 if (fixup_exception(regs)) {
668 * Any interrupt that takes a fault gets the fixup. This makes
669 * the below recursive fault logic only apply to a faults from
676 * Per the above we're !in_interrupt(), aka. task context.
678 * In this case we need to make sure we're not recursively
679 * faulting through the emulate_vsyscall() logic.
681 if (current_thread_info()->sig_on_uaccess_error && signal) {
682 tsk->thread.trap_nr = X86_TRAP_PF;
683 tsk->thread.error_code = error_code | PF_USER;
684 tsk->thread.cr2 = address;
686 /* XXX: hwpoison faults will set the wrong code. */
687 force_sig_info_fault(signal, si_code, address, tsk, 0);
691 * Barring that, we can do the fixup and be happy.
699 * Valid to do another page fault here, because if this fault
700 * had been triggered by is_prefetch fixup_exception would have
705 * Hall of shame of CPU/BIOS bugs.
707 if (is_prefetch(regs, error_code, address))
710 if (is_errata93(regs, address))
714 * Oops. The kernel tried to access some bad page. We'll have to
715 * terminate things with extreme prejudice:
717 flags = oops_begin();
719 show_fault_oops(regs, error_code, address);
721 if (task_stack_end_corrupted(tsk))
722 printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");
724 tsk->thread.cr2 = address;
725 tsk->thread.trap_nr = X86_TRAP_PF;
726 tsk->thread.error_code = error_code;
729 if (__die("Oops", regs, error_code))
732 /* Executive summary in case the body of the oops scrolled away */
733 printk(KERN_DEFAULT "CR2: %016lx\n", address);
735 oops_end(flags, regs, sig);
739 * Print out info about fatal segfaults, if the show_unhandled_signals
743 show_signal_msg(struct pt_regs *regs, unsigned long error_code,
744 unsigned long address, struct task_struct *tsk)
746 if (!unhandled_signal(tsk, SIGSEGV))
749 if (!printk_ratelimit())
752 printk("%s%s[%d]: segfault at %lx ip %p sp %p error %lx",
753 task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
754 tsk->comm, task_pid_nr(tsk), address,
755 (void *)regs->ip, (void *)regs->sp, error_code);
757 print_vma_addr(KERN_CONT " in ", regs->ip);
759 printk(KERN_CONT "\n");
763 __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
764 unsigned long address, int si_code)
766 struct task_struct *tsk = current;
768 /* User mode accesses just cause a SIGSEGV */
769 if (error_code & PF_USER) {
771 * It's possible to have interrupts off here:
776 * Valid to do another page fault here because this one came
779 if (is_prefetch(regs, error_code, address))
782 if (is_errata100(regs, address))
787 * Instruction fetch faults in the vsyscall page might need
790 if (unlikely((error_code & PF_INSTR) &&
791 ((address & ~0xfff) == VSYSCALL_ADDR))) {
792 if (emulate_vsyscall(regs, address))
796 /* Kernel addresses are always protection faults: */
797 if (address >= TASK_SIZE)
798 error_code |= PF_PROT;
800 if (likely(show_unhandled_signals))
801 show_signal_msg(regs, error_code, address, tsk);
803 tsk->thread.cr2 = address;
804 tsk->thread.error_code = error_code;
805 tsk->thread.trap_nr = X86_TRAP_PF;
807 force_sig_info_fault(SIGSEGV, si_code, address, tsk, 0);
812 if (is_f00f_bug(regs, address))
815 no_context(regs, error_code, address, SIGSEGV, si_code);
819 bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
820 unsigned long address)
822 __bad_area_nosemaphore(regs, error_code, address, SEGV_MAPERR);
826 __bad_area(struct pt_regs *regs, unsigned long error_code,
827 unsigned long address, int si_code)
829 struct mm_struct *mm = current->mm;
832 * Something tried to access memory that isn't in our memory map..
833 * Fix it, but check if it's kernel or user first..
835 up_read(&mm->mmap_sem);
837 __bad_area_nosemaphore(regs, error_code, address, si_code);
841 bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address)
843 __bad_area(regs, error_code, address, SEGV_MAPERR);
847 bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
848 unsigned long address)
850 __bad_area(regs, error_code, address, SEGV_ACCERR);
854 do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
857 struct task_struct *tsk = current;
858 int code = BUS_ADRERR;
860 /* Kernel mode? Handle exceptions or die: */
861 if (!(error_code & PF_USER)) {
862 no_context(regs, error_code, address, SIGBUS, BUS_ADRERR);
866 /* User-space => ok to do another page fault: */
867 if (is_prefetch(regs, error_code, address))
870 tsk->thread.cr2 = address;
871 tsk->thread.error_code = error_code;
872 tsk->thread.trap_nr = X86_TRAP_PF;
874 #ifdef CONFIG_MEMORY_FAILURE
875 if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
877 "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
878 tsk->comm, tsk->pid, address);
879 code = BUS_MCEERR_AR;
882 force_sig_info_fault(SIGBUS, code, address, tsk, fault);
886 mm_fault_error(struct pt_regs *regs, unsigned long error_code,
887 unsigned long address, unsigned int fault)
889 if (fatal_signal_pending(current) && !(error_code & PF_USER)) {
890 no_context(regs, error_code, address, 0, 0);
894 if (fault & VM_FAULT_OOM) {
895 /* Kernel mode? Handle exceptions or die: */
896 if (!(error_code & PF_USER)) {
897 no_context(regs, error_code, address,
898 SIGSEGV, SEGV_MAPERR);
903 * We ran out of memory, call the OOM killer, and return the
904 * userspace (which will retry the fault, or kill us if we got
907 pagefault_out_of_memory();
909 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
910 VM_FAULT_HWPOISON_LARGE))
911 do_sigbus(regs, error_code, address, fault);
912 else if (fault & VM_FAULT_SIGSEGV)
913 bad_area_nosemaphore(regs, error_code, address);
919 static int spurious_fault_check(unsigned long error_code, pte_t *pte)
921 if ((error_code & PF_WRITE) && !pte_write(*pte))
924 if ((error_code & PF_INSTR) && !pte_exec(*pte))
931 * Handle a spurious fault caused by a stale TLB entry.
933 * This allows us to lazily refresh the TLB when increasing the
934 * permissions of a kernel page (RO -> RW or NX -> X). Doing it
935 * eagerly is very expensive since that implies doing a full
936 * cross-processor TLB flush, even if no stale TLB entries exist
937 * on other processors.
939 * Spurious faults may only occur if the TLB contains an entry with
940 * fewer permission than the page table entry. Non-present (P = 0)
941 * and reserved bit (R = 1) faults are never spurious.
943 * There are no security implications to leaving a stale TLB when
944 * increasing the permissions on a page.
946 * Returns non-zero if a spurious fault was handled, zero otherwise.
948 * See Intel Developer's Manual Vol 3 Section 4.10.4.3, bullet 3
949 * (Optional Invalidation).
952 spurious_fault(unsigned long error_code, unsigned long address)
961 * Only writes to RO or instruction fetches from NX may cause
964 * These could be from user or supervisor accesses but the TLB
965 * is only lazily flushed after a kernel mapping protection
966 * change, so user accesses are not expected to cause spurious
969 if (error_code != (PF_WRITE | PF_PROT)
970 && error_code != (PF_INSTR | PF_PROT))
973 pgd = init_mm.pgd + pgd_index(address);
974 if (!pgd_present(*pgd))
977 pud = pud_offset(pgd, address);
978 if (!pud_present(*pud))
982 return spurious_fault_check(error_code, (pte_t *) pud);
984 pmd = pmd_offset(pud, address);
985 if (!pmd_present(*pmd))
989 return spurious_fault_check(error_code, (pte_t *) pmd);
991 pte = pte_offset_kernel(pmd, address);
992 if (!pte_present(*pte))
995 ret = spurious_fault_check(error_code, pte);
1000 * Make sure we have permissions in PMD.
1001 * If not, then there's a bug in the page tables:
1003 ret = spurious_fault_check(error_code, (pte_t *) pmd);
1004 WARN_ONCE(!ret, "PMD has incorrect permission bits\n");
1008 NOKPROBE_SYMBOL(spurious_fault);
1010 int show_unhandled_signals = 1;
1013 access_error(unsigned long error_code, struct vm_area_struct *vma)
1015 if (error_code & PF_WRITE) {
1016 /* write, present and write, not present: */
1017 if (unlikely(!(vma->vm_flags & VM_WRITE)))
1022 /* read, present: */
1023 if (unlikely(error_code & PF_PROT))
1026 /* read, not present: */
1027 if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))))
1033 static int fault_in_kernel_space(unsigned long address)
1035 return address >= TASK_SIZE_MAX;
1038 static inline bool smap_violation(int error_code, struct pt_regs *regs)
1040 if (!IS_ENABLED(CONFIG_X86_SMAP))
1043 if (!static_cpu_has(X86_FEATURE_SMAP))
1046 if (error_code & PF_USER)
1049 if (!user_mode(regs) && (regs->flags & X86_EFLAGS_AC))
1056 * This routine handles page faults. It determines the address,
1057 * and the problem, and then passes it off to one of the appropriate
1060 * This function must have noinline because both callers
1061 * {,trace_}do_page_fault() have notrace on. Having this an actual function
1062 * guarantees there's a function trace entry.
1064 static noinline void
1065 __do_page_fault(struct pt_regs *regs, unsigned long error_code,
1066 unsigned long address)
1068 struct vm_area_struct *vma;
1069 struct task_struct *tsk;
1070 struct mm_struct *mm;
1071 int fault, major = 0;
1072 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
1078 * Detect and handle instructions that would cause a page fault for
1079 * both a tracked kernel page and a userspace page.
1081 if (kmemcheck_active(regs))
1082 kmemcheck_hide(regs);
1083 prefetchw(&mm->mmap_sem);
1085 if (unlikely(kmmio_fault(regs, address)))
1089 * We fault-in kernel-space virtual memory on-demand. The
1090 * 'reference' page table is init_mm.pgd.
1092 * NOTE! We MUST NOT take any locks for this case. We may
1093 * be in an interrupt or a critical region, and should
1094 * only copy the information from the master page table,
1097 * This verifies that the fault happens in kernel space
1098 * (error_code & 4) == 0, and that the fault was not a
1099 * protection error (error_code & 9) == 0.
1101 if (unlikely(fault_in_kernel_space(address))) {
1102 if (!(error_code & (PF_RSVD | PF_USER | PF_PROT))) {
1103 if (vmalloc_fault(address) >= 0)
1106 if (kmemcheck_fault(regs, address, error_code))
1110 /* Can handle a stale RO->RW TLB: */
1111 if (spurious_fault(error_code, address))
1114 /* kprobes don't want to hook the spurious faults: */
1115 if (kprobes_fault(regs))
1118 * Don't take the mm semaphore here. If we fixup a prefetch
1119 * fault we could otherwise deadlock:
1121 bad_area_nosemaphore(regs, error_code, address);
1126 /* kprobes don't want to hook the spurious faults: */
1127 if (unlikely(kprobes_fault(regs)))
1130 if (unlikely(error_code & PF_RSVD))
1131 pgtable_bad(regs, error_code, address);
1133 if (unlikely(smap_violation(error_code, regs))) {
1134 bad_area_nosemaphore(regs, error_code, address);
1139 * If we're in an interrupt, have no user context or are running
1140 * in a region with pagefaults disabled then we must not take the fault
1142 if (unlikely(faulthandler_disabled() || !mm)) {
1143 bad_area_nosemaphore(regs, error_code, address);
1148 * It's safe to allow irq's after cr2 has been saved and the
1149 * vmalloc fault has been handled.
1151 * User-mode registers count as a user access even for any
1152 * potential system fault or CPU buglet:
1154 if (user_mode(regs)) {
1156 error_code |= PF_USER;
1157 flags |= FAULT_FLAG_USER;
1159 if (regs->flags & X86_EFLAGS_IF)
1163 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
1165 if (error_code & PF_WRITE)
1166 flags |= FAULT_FLAG_WRITE;
1169 * When running in the kernel we expect faults to occur only to
1170 * addresses in user space. All other faults represent errors in
1171 * the kernel and should generate an OOPS. Unfortunately, in the
1172 * case of an erroneous fault occurring in a code path which already
1173 * holds mmap_sem we will deadlock attempting to validate the fault
1174 * against the address space. Luckily the kernel only validly
1175 * references user space from well defined areas of code, which are
1176 * listed in the exceptions table.
1178 * As the vast majority of faults will be valid we will only perform
1179 * the source reference check when there is a possibility of a
1180 * deadlock. Attempt to lock the address space, if we cannot we then
1181 * validate the source. If this is invalid we can skip the address
1182 * space check, thus avoiding the deadlock:
1184 if (unlikely(!down_read_trylock(&mm->mmap_sem))) {
1185 if ((error_code & PF_USER) == 0 &&
1186 !search_exception_tables(regs->ip)) {
1187 bad_area_nosemaphore(regs, error_code, address);
1191 down_read(&mm->mmap_sem);
1194 * The above down_read_trylock() might have succeeded in
1195 * which case we'll have missed the might_sleep() from
1201 vma = find_vma(mm, address);
1202 if (unlikely(!vma)) {
1203 bad_area(regs, error_code, address);
1206 if (likely(vma->vm_start <= address))
1208 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
1209 bad_area(regs, error_code, address);
1212 if (error_code & PF_USER) {
1214 * Accessing the stack below %sp is always a bug.
1215 * The large cushion allows instructions like enter
1216 * and pusha to work. ("enter $65535, $31" pushes
1217 * 32 pointers and then decrements %sp by 65535.)
1219 if (unlikely(address + 65536 + 32 * sizeof(unsigned long) < regs->sp)) {
1220 bad_area(regs, error_code, address);
1224 if (unlikely(expand_stack(vma, address))) {
1225 bad_area(regs, error_code, address);
1230 * Ok, we have a good vm_area for this memory access, so
1231 * we can handle it..
1234 if (unlikely(access_error(error_code, vma))) {
1235 bad_area_access_error(regs, error_code, address);
1240 * If for any reason at all we couldn't handle the fault,
1241 * make sure we exit gracefully rather than endlessly redo
1242 * the fault. Since we never set FAULT_FLAG_RETRY_NOWAIT, if
1243 * we get VM_FAULT_RETRY back, the mmap_sem has been unlocked.
1245 fault = handle_mm_fault(mm, vma, address, flags);
1246 major |= fault & VM_FAULT_MAJOR;
1249 * If we need to retry the mmap_sem has already been released,
1250 * and if there is a fatal signal pending there is no guarantee
1251 * that we made any progress. Handle this case first.
1253 if (unlikely(fault & VM_FAULT_RETRY)) {
1254 /* Retry at most once */
1255 if (flags & FAULT_FLAG_ALLOW_RETRY) {
1256 flags &= ~FAULT_FLAG_ALLOW_RETRY;
1257 flags |= FAULT_FLAG_TRIED;
1258 if (!fatal_signal_pending(tsk))
1262 /* User mode? Just return to handle the fatal exception */
1263 if (flags & FAULT_FLAG_USER)
1266 /* Not returning to user mode? Handle exceptions or die: */
1267 no_context(regs, error_code, address, SIGBUS, BUS_ADRERR);
1271 up_read(&mm->mmap_sem);
1272 if (unlikely(fault & VM_FAULT_ERROR)) {
1273 mm_fault_error(regs, error_code, address, fault);
1278 * Major/minor page fault accounting. If any of the events
1279 * returned VM_FAULT_MAJOR, we account it as a major fault.
1283 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address);
1286 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address);
1289 check_v8086_mode(regs, address, tsk);
1291 NOKPROBE_SYMBOL(__do_page_fault);
1293 dotraplinkage void notrace
1294 do_page_fault(struct pt_regs *regs, unsigned long error_code)
1296 unsigned long address = read_cr2(); /* Get the faulting address */
1297 enum ctx_state prev_state;
1300 * We must have this function tagged with __kprobes, notrace and call
1301 * read_cr2() before calling anything else. To avoid calling any kind
1302 * of tracing machinery before we've observed the CR2 value.
1304 * exception_{enter,exit}() contain all sorts of tracepoints.
1307 prev_state = exception_enter();
1308 __do_page_fault(regs, error_code, address);
1309 exception_exit(prev_state);
1311 NOKPROBE_SYMBOL(do_page_fault);
1313 #ifdef CONFIG_TRACING
1314 static nokprobe_inline void
1315 trace_page_fault_entries(unsigned long address, struct pt_regs *regs,
1316 unsigned long error_code)
1318 if (user_mode(regs))
1319 trace_page_fault_user(address, regs, error_code);
1321 trace_page_fault_kernel(address, regs, error_code);
1324 dotraplinkage void notrace
1325 trace_do_page_fault(struct pt_regs *regs, unsigned long error_code)
1328 * The exception_enter and tracepoint processing could
1329 * trigger another page faults (user space callchain
1330 * reading) and destroy the original cr2 value, so read
1331 * the faulting address now.
1333 unsigned long address = read_cr2();
1334 enum ctx_state prev_state;
1336 prev_state = exception_enter();
1337 trace_page_fault_entries(address, regs, error_code);
1338 __do_page_fault(regs, error_code, address);
1339 exception_exit(prev_state);
1341 NOKPROBE_SYMBOL(trace_do_page_fault);
1342 #endif /* CONFIG_TRACING */