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 */
24 #define CREATE_TRACE_POINTS
25 #include <asm/trace/exceptions.h>
28 * Page fault error code bits:
30 * bit 0 == 0: no page found 1: protection fault
31 * bit 1 == 0: read access 1: write access
32 * bit 2 == 0: kernel-mode access 1: user-mode access
33 * bit 3 == 1: use of reserved bit detected
34 * bit 4 == 1: fault was an instruction fetch
36 enum x86_pf_error_code {
46 * Returns 0 if mmiotrace is disabled, or if the fault is not
47 * handled by mmiotrace:
49 static nokprobe_inline int
50 kmmio_fault(struct pt_regs *regs, unsigned long addr)
52 if (unlikely(is_kmmio_active()))
53 if (kmmio_handler(regs, addr) == 1)
58 static nokprobe_inline int kprobes_fault(struct pt_regs *regs)
62 /* kprobe_running() needs smp_processor_id() */
63 if (kprobes_built_in() && !user_mode(regs)) {
65 if (kprobe_running() && kprobe_fault_handler(regs, 14))
78 * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
79 * Check that here and ignore it.
83 * Sometimes the CPU reports invalid exceptions on prefetch.
84 * Check that here and ignore it.
86 * Opcode checker based on code by Richard Brunner.
89 check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr,
90 unsigned char opcode, int *prefetch)
92 unsigned char instr_hi = opcode & 0xf0;
93 unsigned char instr_lo = opcode & 0x0f;
99 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes.
100 * In X86_64 long mode, the CPU will signal invalid
101 * opcode if some of these prefixes are present so
102 * X86_64 will never get here anyway
104 return ((instr_lo & 7) == 0x6);
108 * In AMD64 long mode 0x40..0x4F are valid REX prefixes
109 * Need to figure out under what instruction mode the
110 * instruction was issued. Could check the LDT for lm,
111 * but for now it's good enough to assume that long
112 * mode only uses well known segments or kernel.
114 return (!user_mode(regs) || user_64bit_mode(regs));
117 /* 0x64 thru 0x67 are valid prefixes in all modes. */
118 return (instr_lo & 0xC) == 0x4;
120 /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */
121 return !instr_lo || (instr_lo>>1) == 1;
123 /* Prefetch instruction is 0x0F0D or 0x0F18 */
124 if (probe_kernel_address(instr, opcode))
127 *prefetch = (instr_lo == 0xF) &&
128 (opcode == 0x0D || opcode == 0x18);
136 is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
138 unsigned char *max_instr;
139 unsigned char *instr;
143 * If it was a exec (instruction fetch) fault on NX page, then
144 * do not ignore the fault:
146 if (error_code & PF_INSTR)
149 instr = (void *)convert_ip_to_linear(current, regs);
150 max_instr = instr + 15;
152 if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE_MAX)
155 while (instr < max_instr) {
156 unsigned char opcode;
158 if (probe_kernel_address(instr, opcode))
163 if (!check_prefetch_opcode(regs, instr, opcode, &prefetch))
170 force_sig_info_fault(int si_signo, int si_code, unsigned long address,
171 struct task_struct *tsk, int fault)
176 info.si_signo = si_signo;
178 info.si_code = si_code;
179 info.si_addr = (void __user *)address;
180 if (fault & VM_FAULT_HWPOISON_LARGE)
181 lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
182 if (fault & VM_FAULT_HWPOISON)
184 info.si_addr_lsb = lsb;
186 force_sig_info(si_signo, &info, tsk);
189 DEFINE_SPINLOCK(pgd_lock);
193 static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
195 unsigned index = pgd_index(address);
201 pgd_k = init_mm.pgd + index;
203 if (!pgd_present(*pgd_k))
207 * set_pgd(pgd, *pgd_k); here would be useless on PAE
208 * and redundant with the set_pmd() on non-PAE. As would
211 pud = pud_offset(pgd, address);
212 pud_k = pud_offset(pgd_k, address);
213 if (!pud_present(*pud_k))
216 pmd = pmd_offset(pud, address);
217 pmd_k = pmd_offset(pud_k, address);
218 if (!pmd_present(*pmd_k))
221 if (!pmd_present(*pmd))
222 set_pmd(pmd, *pmd_k);
224 BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k));
229 void vmalloc_sync_all(void)
231 unsigned long address;
233 if (SHARED_KERNEL_PMD)
236 for (address = VMALLOC_START & PMD_MASK;
237 address >= TASK_SIZE && address < FIXADDR_TOP;
238 address += PMD_SIZE) {
241 spin_lock(&pgd_lock);
242 list_for_each_entry(page, &pgd_list, lru) {
243 spinlock_t *pgt_lock;
246 /* the pgt_lock only for Xen */
247 pgt_lock = &pgd_page_get_mm(page)->page_table_lock;
250 ret = vmalloc_sync_one(page_address(page), address);
251 spin_unlock(pgt_lock);
256 spin_unlock(&pgd_lock);
263 * Handle a fault on the vmalloc or module mapping area
265 static noinline int vmalloc_fault(unsigned long address)
267 unsigned long pgd_paddr;
271 /* Make sure we are in vmalloc area: */
272 if (!(address >= VMALLOC_START && address < VMALLOC_END))
275 WARN_ON_ONCE(in_nmi());
278 * Synchronize this task's top level page-table
279 * with the 'reference' page table.
281 * Do _not_ use "current" here. We might be inside
282 * an interrupt in the middle of a task switch..
284 pgd_paddr = read_cr3();
285 pmd_k = vmalloc_sync_one(__va(pgd_paddr), address);
289 pte_k = pte_offset_kernel(pmd_k, address);
290 if (!pte_present(*pte_k))
295 NOKPROBE_SYMBOL(vmalloc_fault);
298 * Did it hit the DOS screen memory VA from vm86 mode?
301 check_v8086_mode(struct pt_regs *regs, unsigned long address,
302 struct task_struct *tsk)
306 if (!v8086_mode(regs))
309 bit = (address - 0xA0000) >> PAGE_SHIFT;
311 tsk->thread.screen_bitmap |= 1 << bit;
314 static bool low_pfn(unsigned long pfn)
316 return pfn < max_low_pfn;
319 static void dump_pagetable(unsigned long address)
321 pgd_t *base = __va(read_cr3());
322 pgd_t *pgd = &base[pgd_index(address)];
326 #ifdef CONFIG_X86_PAE
327 printk("*pdpt = %016Lx ", pgd_val(*pgd));
328 if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd))
331 pmd = pmd_offset(pud_offset(pgd, address), address);
332 printk(KERN_CONT "*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd));
335 * We must not directly access the pte in the highpte
336 * case if the page table is located in highmem.
337 * And let's rather not kmap-atomic the pte, just in case
338 * it's allocated already:
340 if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_large(*pmd))
343 pte = pte_offset_kernel(pmd, address);
344 printk("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte));
349 #else /* CONFIG_X86_64: */
351 void vmalloc_sync_all(void)
353 sync_global_pgds(VMALLOC_START & PGDIR_MASK, VMALLOC_END, 0);
359 * Handle a fault on the vmalloc area
361 * This assumes no large pages in there.
363 static noinline int vmalloc_fault(unsigned long address)
365 pgd_t *pgd, *pgd_ref;
366 pud_t *pud, *pud_ref;
367 pmd_t *pmd, *pmd_ref;
368 pte_t *pte, *pte_ref;
370 /* Make sure we are in vmalloc area: */
371 if (!(address >= VMALLOC_START && address < VMALLOC_END))
374 WARN_ON_ONCE(in_nmi());
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))
386 if (pgd_none(*pgd)) {
387 set_pgd(pgd, *pgd_ref);
388 arch_flush_lazy_mmu_mode();
390 BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref));
394 * Below here mismatches are bugs because these lower tables
398 pud = pud_offset(pgd, address);
399 pud_ref = pud_offset(pgd_ref, address);
400 if (pud_none(*pud_ref))
403 if (pud_none(*pud) || pud_page_vaddr(*pud) != pud_page_vaddr(*pud_ref))
406 pmd = pmd_offset(pud, address);
407 pmd_ref = pmd_offset(pud_ref, address);
408 if (pmd_none(*pmd_ref))
411 if (pmd_none(*pmd) || pmd_page(*pmd) != pmd_page(*pmd_ref))
414 pte_ref = pte_offset_kernel(pmd_ref, address);
415 if (!pte_present(*pte_ref))
418 pte = pte_offset_kernel(pmd, address);
421 * Don't use pte_page here, because the mappings can point
422 * outside mem_map, and the NUMA hash lookup cannot handle
425 if (!pte_present(*pte) || pte_pfn(*pte) != pte_pfn(*pte_ref))
430 NOKPROBE_SYMBOL(vmalloc_fault);
432 #ifdef CONFIG_CPU_SUP_AMD
433 static const char errata93_warning[] =
435 "******* Your BIOS seems to not contain a fix for K8 errata #93\n"
436 "******* Working around it, but it may cause SEGVs or burn power.\n"
437 "******* Please consider a BIOS update.\n"
438 "******* Disabling USB legacy in the BIOS may also help.\n";
442 * No vm86 mode in 64-bit mode:
445 check_v8086_mode(struct pt_regs *regs, unsigned long address,
446 struct task_struct *tsk)
450 static int bad_address(void *p)
454 return probe_kernel_address((unsigned long *)p, dummy);
457 static void dump_pagetable(unsigned long address)
459 pgd_t *base = __va(read_cr3() & PHYSICAL_PAGE_MASK);
460 pgd_t *pgd = base + pgd_index(address);
465 if (bad_address(pgd))
468 printk("PGD %lx ", pgd_val(*pgd));
470 if (!pgd_present(*pgd))
473 pud = pud_offset(pgd, address);
474 if (bad_address(pud))
477 printk("PUD %lx ", pud_val(*pud));
478 if (!pud_present(*pud) || pud_large(*pud))
481 pmd = pmd_offset(pud, address);
482 if (bad_address(pmd))
485 printk("PMD %lx ", pmd_val(*pmd));
486 if (!pmd_present(*pmd) || pmd_large(*pmd))
489 pte = pte_offset_kernel(pmd, address);
490 if (bad_address(pte))
493 printk("PTE %lx", pte_val(*pte));
501 #endif /* CONFIG_X86_64 */
504 * Workaround for K8 erratum #93 & buggy BIOS.
506 * BIOS SMM functions are required to use a specific workaround
507 * to avoid corruption of the 64bit RIP register on C stepping K8.
509 * A lot of BIOS that didn't get tested properly miss this.
511 * The OS sees this as a page fault with the upper 32bits of RIP cleared.
512 * Try to work around it here.
514 * Note we only handle faults in kernel here.
515 * Does nothing on 32-bit.
517 static int is_errata93(struct pt_regs *regs, unsigned long address)
519 #if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD)
520 if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD
521 || boot_cpu_data.x86 != 0xf)
524 if (address != regs->ip)
527 if ((address >> 32) != 0)
530 address |= 0xffffffffUL << 32;
531 if ((address >= (u64)_stext && address <= (u64)_etext) ||
532 (address >= MODULES_VADDR && address <= MODULES_END)) {
533 printk_once(errata93_warning);
542 * Work around K8 erratum #100 K8 in compat mode occasionally jumps
543 * to illegal addresses >4GB.
545 * We catch this in the page fault handler because these addresses
546 * are not reachable. Just detect this case and return. Any code
547 * segment in LDT is compatibility mode.
549 static int is_errata100(struct pt_regs *regs, unsigned long address)
552 if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32))
558 static int is_f00f_bug(struct pt_regs *regs, unsigned long address)
560 #ifdef CONFIG_X86_F00F_BUG
564 * Pentium F0 0F C7 C8 bug workaround:
566 if (boot_cpu_has_bug(X86_BUG_F00F)) {
567 nr = (address - idt_descr.address) >> 3;
570 do_invalid_op(regs, 0);
578 static const char nx_warning[] = KERN_CRIT
579 "kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n";
580 static const char smep_warning[] = KERN_CRIT
581 "unable to execute userspace code (SMEP?) (uid: %d)\n";
584 show_fault_oops(struct pt_regs *regs, unsigned long error_code,
585 unsigned long address)
587 if (!oops_may_print())
590 if (error_code & PF_INSTR) {
595 pgd = __va(read_cr3() & PHYSICAL_PAGE_MASK);
596 pgd += pgd_index(address);
598 pte = lookup_address_in_pgd(pgd, address, &level);
600 if (pte && pte_present(*pte) && !pte_exec(*pte))
601 printk(nx_warning, from_kuid(&init_user_ns, current_uid()));
602 if (pte && pte_present(*pte) && pte_exec(*pte) &&
603 (pgd_flags(*pgd) & _PAGE_USER) &&
604 (__read_cr4() & X86_CR4_SMEP))
605 printk(smep_warning, from_kuid(&init_user_ns, current_uid()));
608 printk(KERN_ALERT "BUG: unable to handle kernel ");
609 if (address < PAGE_SIZE)
610 printk(KERN_CONT "NULL pointer dereference");
612 printk(KERN_CONT "paging request");
614 printk(KERN_CONT " at %p\n", (void *) address);
615 printk(KERN_ALERT "IP:");
616 printk_address(regs->ip);
618 dump_pagetable(address);
622 pgtable_bad(struct pt_regs *regs, unsigned long error_code,
623 unsigned long address)
625 struct task_struct *tsk;
629 flags = oops_begin();
633 printk(KERN_ALERT "%s: Corrupted page table at address %lx\n",
635 dump_pagetable(address);
637 tsk->thread.cr2 = address;
638 tsk->thread.trap_nr = X86_TRAP_PF;
639 tsk->thread.error_code = error_code;
641 if (__die("Bad pagetable", regs, error_code))
644 oops_end(flags, regs, sig);
648 no_context(struct pt_regs *regs, unsigned long error_code,
649 unsigned long address, int signal, int si_code)
651 struct task_struct *tsk = current;
655 /* Are we prepared to handle this kernel fault? */
656 if (fixup_exception(regs)) {
658 * Any interrupt that takes a fault gets the fixup. This makes
659 * the below recursive fault logic only apply to a faults from
666 * Per the above we're !in_interrupt(), aka. task context.
668 * In this case we need to make sure we're not recursively
669 * faulting through the emulate_vsyscall() logic.
671 if (current_thread_info()->sig_on_uaccess_error && signal) {
672 tsk->thread.trap_nr = X86_TRAP_PF;
673 tsk->thread.error_code = error_code | PF_USER;
674 tsk->thread.cr2 = address;
676 /* XXX: hwpoison faults will set the wrong code. */
677 force_sig_info_fault(signal, si_code, address, tsk, 0);
681 * Barring that, we can do the fixup and be happy.
689 * Valid to do another page fault here, because if this fault
690 * had been triggered by is_prefetch fixup_exception would have
695 * Hall of shame of CPU/BIOS bugs.
697 if (is_prefetch(regs, error_code, address))
700 if (is_errata93(regs, address))
704 * Oops. The kernel tried to access some bad page. We'll have to
705 * terminate things with extreme prejudice:
707 flags = oops_begin();
709 show_fault_oops(regs, error_code, address);
711 if (task_stack_end_corrupted(tsk))
712 printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");
714 tsk->thread.cr2 = address;
715 tsk->thread.trap_nr = X86_TRAP_PF;
716 tsk->thread.error_code = error_code;
719 if (__die("Oops", regs, error_code))
722 /* Executive summary in case the body of the oops scrolled away */
723 printk(KERN_DEFAULT "CR2: %016lx\n", address);
725 oops_end(flags, regs, sig);
729 * Print out info about fatal segfaults, if the show_unhandled_signals
733 show_signal_msg(struct pt_regs *regs, unsigned long error_code,
734 unsigned long address, struct task_struct *tsk)
736 if (!unhandled_signal(tsk, SIGSEGV))
739 if (!printk_ratelimit())
742 printk("%s%s[%d]: segfault at %lx ip %p sp %p error %lx",
743 task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
744 tsk->comm, task_pid_nr(tsk), address,
745 (void *)regs->ip, (void *)regs->sp, error_code);
747 print_vma_addr(KERN_CONT " in ", regs->ip);
749 printk(KERN_CONT "\n");
753 __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
754 unsigned long address, int si_code)
756 struct task_struct *tsk = current;
758 /* User mode accesses just cause a SIGSEGV */
759 if (error_code & PF_USER) {
761 * It's possible to have interrupts off here:
766 * Valid to do another page fault here because this one came
769 if (is_prefetch(regs, error_code, address))
772 if (is_errata100(regs, address))
777 * Instruction fetch faults in the vsyscall page might need
780 if (unlikely((error_code & PF_INSTR) &&
781 ((address & ~0xfff) == VSYSCALL_ADDR))) {
782 if (emulate_vsyscall(regs, address))
786 /* Kernel addresses are always protection faults: */
787 if (address >= TASK_SIZE)
788 error_code |= PF_PROT;
790 if (likely(show_unhandled_signals))
791 show_signal_msg(regs, error_code, address, tsk);
793 tsk->thread.cr2 = address;
794 tsk->thread.error_code = error_code;
795 tsk->thread.trap_nr = X86_TRAP_PF;
797 force_sig_info_fault(SIGSEGV, si_code, address, tsk, 0);
802 if (is_f00f_bug(regs, address))
805 no_context(regs, error_code, address, SIGSEGV, si_code);
809 bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
810 unsigned long address)
812 __bad_area_nosemaphore(regs, error_code, address, SEGV_MAPERR);
816 __bad_area(struct pt_regs *regs, unsigned long error_code,
817 unsigned long address, int si_code)
819 struct mm_struct *mm = current->mm;
822 * Something tried to access memory that isn't in our memory map..
823 * Fix it, but check if it's kernel or user first..
825 up_read(&mm->mmap_sem);
827 __bad_area_nosemaphore(regs, error_code, address, si_code);
831 bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address)
833 __bad_area(regs, error_code, address, SEGV_MAPERR);
837 bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
838 unsigned long address)
840 __bad_area(regs, error_code, address, SEGV_ACCERR);
844 do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
847 struct task_struct *tsk = current;
848 int code = BUS_ADRERR;
850 /* Kernel mode? Handle exceptions or die: */
851 if (!(error_code & PF_USER)) {
852 no_context(regs, error_code, address, SIGBUS, BUS_ADRERR);
856 /* User-space => ok to do another page fault: */
857 if (is_prefetch(regs, error_code, address))
860 tsk->thread.cr2 = address;
861 tsk->thread.error_code = error_code;
862 tsk->thread.trap_nr = X86_TRAP_PF;
864 #ifdef CONFIG_MEMORY_FAILURE
865 if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
867 "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
868 tsk->comm, tsk->pid, address);
869 code = BUS_MCEERR_AR;
872 force_sig_info_fault(SIGBUS, code, address, tsk, fault);
876 mm_fault_error(struct pt_regs *regs, unsigned long error_code,
877 unsigned long address, unsigned int fault)
879 if (fatal_signal_pending(current) && !(error_code & PF_USER)) {
880 no_context(regs, error_code, address, 0, 0);
884 if (fault & VM_FAULT_OOM) {
885 /* Kernel mode? Handle exceptions or die: */
886 if (!(error_code & PF_USER)) {
887 no_context(regs, error_code, address,
888 SIGSEGV, SEGV_MAPERR);
893 * We ran out of memory, call the OOM killer, and return the
894 * userspace (which will retry the fault, or kill us if we got
897 pagefault_out_of_memory();
899 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
900 VM_FAULT_HWPOISON_LARGE))
901 do_sigbus(regs, error_code, address, fault);
902 else if (fault & VM_FAULT_SIGSEGV)
903 bad_area_nosemaphore(regs, error_code, address);
909 static int spurious_fault_check(unsigned long error_code, pte_t *pte)
911 if ((error_code & PF_WRITE) && !pte_write(*pte))
914 if ((error_code & PF_INSTR) && !pte_exec(*pte))
921 * Handle a spurious fault caused by a stale TLB entry.
923 * This allows us to lazily refresh the TLB when increasing the
924 * permissions of a kernel page (RO -> RW or NX -> X). Doing it
925 * eagerly is very expensive since that implies doing a full
926 * cross-processor TLB flush, even if no stale TLB entries exist
927 * on other processors.
929 * Spurious faults may only occur if the TLB contains an entry with
930 * fewer permission than the page table entry. Non-present (P = 0)
931 * and reserved bit (R = 1) faults are never spurious.
933 * There are no security implications to leaving a stale TLB when
934 * increasing the permissions on a page.
936 * Returns non-zero if a spurious fault was handled, zero otherwise.
938 * See Intel Developer's Manual Vol 3 Section 4.10.4.3, bullet 3
939 * (Optional Invalidation).
942 spurious_fault(unsigned long error_code, unsigned long address)
951 * Only writes to RO or instruction fetches from NX may cause
954 * These could be from user or supervisor accesses but the TLB
955 * is only lazily flushed after a kernel mapping protection
956 * change, so user accesses are not expected to cause spurious
959 if (error_code != (PF_WRITE | PF_PROT)
960 && error_code != (PF_INSTR | PF_PROT))
963 pgd = init_mm.pgd + pgd_index(address);
964 if (!pgd_present(*pgd))
967 pud = pud_offset(pgd, address);
968 if (!pud_present(*pud))
972 return spurious_fault_check(error_code, (pte_t *) pud);
974 pmd = pmd_offset(pud, address);
975 if (!pmd_present(*pmd))
979 return spurious_fault_check(error_code, (pte_t *) pmd);
981 pte = pte_offset_kernel(pmd, address);
982 if (!pte_present(*pte))
985 ret = spurious_fault_check(error_code, pte);
990 * Make sure we have permissions in PMD.
991 * If not, then there's a bug in the page tables:
993 ret = spurious_fault_check(error_code, (pte_t *) pmd);
994 WARN_ONCE(!ret, "PMD has incorrect permission bits\n");
998 NOKPROBE_SYMBOL(spurious_fault);
1000 int show_unhandled_signals = 1;
1003 access_error(unsigned long error_code, struct vm_area_struct *vma)
1005 if (error_code & PF_WRITE) {
1006 /* write, present and write, not present: */
1007 if (unlikely(!(vma->vm_flags & VM_WRITE)))
1012 /* read, present: */
1013 if (unlikely(error_code & PF_PROT))
1016 /* read, not present: */
1017 if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))))
1023 static int fault_in_kernel_space(unsigned long address)
1025 return address >= TASK_SIZE_MAX;
1028 static inline bool smap_violation(int error_code, struct pt_regs *regs)
1030 if (!IS_ENABLED(CONFIG_X86_SMAP))
1033 if (!static_cpu_has(X86_FEATURE_SMAP))
1036 if (error_code & PF_USER)
1039 if (!user_mode(regs) && (regs->flags & X86_EFLAGS_AC))
1046 * This routine handles page faults. It determines the address,
1047 * and the problem, and then passes it off to one of the appropriate
1050 * This function must have noinline because both callers
1051 * {,trace_}do_page_fault() have notrace on. Having this an actual function
1052 * guarantees there's a function trace entry.
1054 static noinline void
1055 __do_page_fault(struct pt_regs *regs, unsigned long error_code,
1056 unsigned long address)
1058 struct vm_area_struct *vma;
1059 struct task_struct *tsk;
1060 struct mm_struct *mm;
1061 int fault, major = 0;
1062 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
1068 * Detect and handle instructions that would cause a page fault for
1069 * both a tracked kernel page and a userspace page.
1071 if (kmemcheck_active(regs))
1072 kmemcheck_hide(regs);
1073 prefetchw(&mm->mmap_sem);
1075 if (unlikely(kmmio_fault(regs, address)))
1079 * We fault-in kernel-space virtual memory on-demand. The
1080 * 'reference' page table is init_mm.pgd.
1082 * NOTE! We MUST NOT take any locks for this case. We may
1083 * be in an interrupt or a critical region, and should
1084 * only copy the information from the master page table,
1087 * This verifies that the fault happens in kernel space
1088 * (error_code & 4) == 0, and that the fault was not a
1089 * protection error (error_code & 9) == 0.
1091 if (unlikely(fault_in_kernel_space(address))) {
1092 if (!(error_code & (PF_RSVD | PF_USER | PF_PROT))) {
1093 if (vmalloc_fault(address) >= 0)
1096 if (kmemcheck_fault(regs, address, error_code))
1100 /* Can handle a stale RO->RW TLB: */
1101 if (spurious_fault(error_code, address))
1104 /* kprobes don't want to hook the spurious faults: */
1105 if (kprobes_fault(regs))
1108 * Don't take the mm semaphore here. If we fixup a prefetch
1109 * fault we could otherwise deadlock:
1111 bad_area_nosemaphore(regs, error_code, address);
1116 /* kprobes don't want to hook the spurious faults: */
1117 if (unlikely(kprobes_fault(regs)))
1120 if (unlikely(error_code & PF_RSVD))
1121 pgtable_bad(regs, error_code, address);
1123 if (unlikely(smap_violation(error_code, regs))) {
1124 bad_area_nosemaphore(regs, error_code, address);
1129 * If we're in an interrupt, have no user context or are running
1130 * in a region with pagefaults disabled then we must not take the fault
1132 if (unlikely(faulthandler_disabled() || !mm)) {
1133 bad_area_nosemaphore(regs, error_code, address);
1138 * It's safe to allow irq's after cr2 has been saved and the
1139 * vmalloc fault has been handled.
1141 * User-mode registers count as a user access even for any
1142 * potential system fault or CPU buglet:
1144 if (user_mode(regs)) {
1146 error_code |= PF_USER;
1147 flags |= FAULT_FLAG_USER;
1149 if (regs->flags & X86_EFLAGS_IF)
1153 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
1155 if (error_code & PF_WRITE)
1156 flags |= FAULT_FLAG_WRITE;
1159 * When running in the kernel we expect faults to occur only to
1160 * addresses in user space. All other faults represent errors in
1161 * the kernel and should generate an OOPS. Unfortunately, in the
1162 * case of an erroneous fault occurring in a code path which already
1163 * holds mmap_sem we will deadlock attempting to validate the fault
1164 * against the address space. Luckily the kernel only validly
1165 * references user space from well defined areas of code, which are
1166 * listed in the exceptions table.
1168 * As the vast majority of faults will be valid we will only perform
1169 * the source reference check when there is a possibility of a
1170 * deadlock. Attempt to lock the address space, if we cannot we then
1171 * validate the source. If this is invalid we can skip the address
1172 * space check, thus avoiding the deadlock:
1174 if (unlikely(!down_read_trylock(&mm->mmap_sem))) {
1175 if ((error_code & PF_USER) == 0 &&
1176 !search_exception_tables(regs->ip)) {
1177 bad_area_nosemaphore(regs, error_code, address);
1181 down_read(&mm->mmap_sem);
1184 * The above down_read_trylock() might have succeeded in
1185 * which case we'll have missed the might_sleep() from
1191 vma = find_vma(mm, address);
1192 if (unlikely(!vma)) {
1193 bad_area(regs, error_code, address);
1196 if (likely(vma->vm_start <= address))
1198 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
1199 bad_area(regs, error_code, address);
1202 if (error_code & PF_USER) {
1204 * Accessing the stack below %sp is always a bug.
1205 * The large cushion allows instructions like enter
1206 * and pusha to work. ("enter $65535, $31" pushes
1207 * 32 pointers and then decrements %sp by 65535.)
1209 if (unlikely(address + 65536 + 32 * sizeof(unsigned long) < regs->sp)) {
1210 bad_area(regs, error_code, address);
1214 if (unlikely(expand_stack(vma, address))) {
1215 bad_area(regs, error_code, address);
1220 * Ok, we have a good vm_area for this memory access, so
1221 * we can handle it..
1224 if (unlikely(access_error(error_code, vma))) {
1225 bad_area_access_error(regs, error_code, address);
1230 * If for any reason at all we couldn't handle the fault,
1231 * make sure we exit gracefully rather than endlessly redo
1232 * the fault. Since we never set FAULT_FLAG_RETRY_NOWAIT, if
1233 * we get VM_FAULT_RETRY back, the mmap_sem has been unlocked.
1235 fault = handle_mm_fault(mm, vma, address, flags);
1236 major |= fault & VM_FAULT_MAJOR;
1239 * If we need to retry the mmap_sem has already been released,
1240 * and if there is a fatal signal pending there is no guarantee
1241 * that we made any progress. Handle this case first.
1243 if (unlikely(fault & VM_FAULT_RETRY)) {
1244 /* Retry at most once */
1245 if (flags & FAULT_FLAG_ALLOW_RETRY) {
1246 flags &= ~FAULT_FLAG_ALLOW_RETRY;
1247 flags |= FAULT_FLAG_TRIED;
1248 if (!fatal_signal_pending(tsk))
1252 /* User mode? Just return to handle the fatal exception */
1253 if (flags & FAULT_FLAG_USER)
1256 /* Not returning to user mode? Handle exceptions or die: */
1257 no_context(regs, error_code, address, SIGBUS, BUS_ADRERR);
1261 up_read(&mm->mmap_sem);
1262 if (unlikely(fault & VM_FAULT_ERROR)) {
1263 mm_fault_error(regs, error_code, address, fault);
1268 * Major/minor page fault accounting. If any of the events
1269 * returned VM_FAULT_MAJOR, we account it as a major fault.
1273 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address);
1276 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address);
1279 check_v8086_mode(regs, address, tsk);
1281 NOKPROBE_SYMBOL(__do_page_fault);
1283 dotraplinkage void notrace
1284 do_page_fault(struct pt_regs *regs, unsigned long error_code)
1286 unsigned long address = read_cr2(); /* Get the faulting address */
1287 enum ctx_state prev_state;
1290 * We must have this function tagged with __kprobes, notrace and call
1291 * read_cr2() before calling anything else. To avoid calling any kind
1292 * of tracing machinery before we've observed the CR2 value.
1294 * exception_{enter,exit}() contain all sorts of tracepoints.
1297 prev_state = exception_enter();
1298 __do_page_fault(regs, error_code, address);
1299 exception_exit(prev_state);
1301 NOKPROBE_SYMBOL(do_page_fault);
1303 #ifdef CONFIG_TRACING
1304 static nokprobe_inline void
1305 trace_page_fault_entries(unsigned long address, struct pt_regs *regs,
1306 unsigned long error_code)
1308 if (user_mode(regs))
1309 trace_page_fault_user(address, regs, error_code);
1311 trace_page_fault_kernel(address, regs, error_code);
1314 dotraplinkage void notrace
1315 trace_do_page_fault(struct pt_regs *regs, unsigned long error_code)
1318 * The exception_enter and tracepoint processing could
1319 * trigger another page faults (user space callchain
1320 * reading) and destroy the original cr2 value, so read
1321 * the faulting address now.
1323 unsigned long address = read_cr2();
1324 enum ctx_state prev_state;
1326 prev_state = exception_enter();
1327 trace_page_fault_entries(address, regs, error_code);
1328 __do_page_fault(regs, error_code, address);
1329 exception_exit(prev_state);
1331 NOKPROBE_SYMBOL(trace_do_page_fault);
1332 #endif /* CONFIG_TRACING */