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/sched/task_stack.h> /* task_stack_*(), ... */
8 #include <linux/kdebug.h> /* oops_begin/end, ... */
9 #include <linux/extable.h> /* search_exception_tables */
10 #include <linux/bootmem.h> /* max_low_pfn */
11 #include <linux/kprobes.h> /* NOKPROBE_SYMBOL, ... */
12 #include <linux/mmiotrace.h> /* kmmio_handler, ... */
13 #include <linux/perf_event.h> /* perf_sw_event */
14 #include <linux/hugetlb.h> /* hstate_index_to_shift */
15 #include <linux/prefetch.h> /* prefetchw */
16 #include <linux/context_tracking.h> /* exception_enter(), ... */
17 #include <linux/uaccess.h> /* faulthandler_disabled() */
19 #include <asm/cpufeature.h> /* boot_cpu_has, ... */
20 #include <asm/traps.h> /* dotraplinkage, ... */
21 #include <asm/pgalloc.h> /* pgd_*(), ... */
22 #include <asm/kmemcheck.h> /* kmemcheck_*(), ... */
23 #include <asm/fixmap.h> /* VSYSCALL_ADDR */
24 #include <asm/vsyscall.h> /* emulate_vsyscall */
25 #include <asm/vm86.h> /* struct vm86 */
26 #include <asm/mmu_context.h> /* vma_pkey() */
28 #define CREATE_TRACE_POINTS
29 #include <asm/trace/exceptions.h>
32 * Page fault error code bits:
34 * bit 0 == 0: no page found 1: protection fault
35 * bit 1 == 0: read access 1: write access
36 * bit 2 == 0: kernel-mode access 1: user-mode access
37 * bit 3 == 1: use of reserved bit detected
38 * bit 4 == 1: fault was an instruction fetch
39 * bit 5 == 1: protection keys block access
41 enum x86_pf_error_code {
52 * Returns 0 if mmiotrace is disabled, or if the fault is not
53 * handled by mmiotrace:
55 static nokprobe_inline int
56 kmmio_fault(struct pt_regs *regs, unsigned long addr)
58 if (unlikely(is_kmmio_active()))
59 if (kmmio_handler(regs, addr) == 1)
64 static nokprobe_inline int kprobes_fault(struct pt_regs *regs)
68 /* kprobe_running() needs smp_processor_id() */
69 if (kprobes_built_in() && !user_mode(regs)) {
71 if (kprobe_running() && kprobe_fault_handler(regs, 14))
84 * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
85 * Check that here and ignore it.
89 * Sometimes the CPU reports invalid exceptions on prefetch.
90 * Check that here and ignore it.
92 * Opcode checker based on code by Richard Brunner.
95 check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr,
96 unsigned char opcode, int *prefetch)
98 unsigned char instr_hi = opcode & 0xf0;
99 unsigned char instr_lo = opcode & 0x0f;
105 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes.
106 * In X86_64 long mode, the CPU will signal invalid
107 * opcode if some of these prefixes are present so
108 * X86_64 will never get here anyway
110 return ((instr_lo & 7) == 0x6);
114 * In AMD64 long mode 0x40..0x4F are valid REX prefixes
115 * Need to figure out under what instruction mode the
116 * instruction was issued. Could check the LDT for lm,
117 * but for now it's good enough to assume that long
118 * mode only uses well known segments or kernel.
120 return (!user_mode(regs) || user_64bit_mode(regs));
123 /* 0x64 thru 0x67 are valid prefixes in all modes. */
124 return (instr_lo & 0xC) == 0x4;
126 /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */
127 return !instr_lo || (instr_lo>>1) == 1;
129 /* Prefetch instruction is 0x0F0D or 0x0F18 */
130 if (probe_kernel_address(instr, opcode))
133 *prefetch = (instr_lo == 0xF) &&
134 (opcode == 0x0D || opcode == 0x18);
142 is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
144 unsigned char *max_instr;
145 unsigned char *instr;
149 * If it was a exec (instruction fetch) fault on NX page, then
150 * do not ignore the fault:
152 if (error_code & PF_INSTR)
155 instr = (void *)convert_ip_to_linear(current, regs);
156 max_instr = instr + 15;
158 if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE_MAX)
161 while (instr < max_instr) {
162 unsigned char opcode;
164 if (probe_kernel_address(instr, opcode))
169 if (!check_prefetch_opcode(regs, instr, opcode, &prefetch))
176 * A protection key fault means that the PKRU value did not allow
177 * access to some PTE. Userspace can figure out what PKRU was
178 * from the XSAVE state, and this function fills out a field in
179 * siginfo so userspace can discover which protection key was set
182 * If we get here, we know that the hardware signaled a PF_PK
183 * fault and that there was a VMA once we got in the fault
184 * handler. It does *not* guarantee that the VMA we find here
185 * was the one that we faulted on.
187 * 1. T1 : mprotect_key(foo, PAGE_SIZE, pkey=4);
188 * 2. T1 : set PKRU to deny access to pkey=4, touches page
190 * 4. T2: mprotect_key(foo, PAGE_SIZE, pkey=5);
191 * 5. T1 : enters fault handler, takes mmap_sem, etc...
192 * 6. T1 : reaches here, sees vma_pkey(vma)=5, when we really
193 * faulted on a pte with its pkey=4.
195 static void fill_sig_info_pkey(int si_code, siginfo_t *info, u32 *pkey)
197 /* This is effectively an #ifdef */
198 if (!boot_cpu_has(X86_FEATURE_OSPKE))
201 /* Fault not from Protection Keys: nothing to do */
202 if (si_code != SEGV_PKUERR)
205 * force_sig_info_fault() is called from a number of
206 * contexts, some of which have a VMA and some of which
207 * do not. The PF_PK handing happens after we have a
208 * valid VMA, so we should never reach this without a
212 WARN_ONCE(1, "PKU fault with no VMA passed in");
217 * si_pkey should be thought of as a strong hint, but not
218 * absolutely guranteed to be 100% accurate because of
219 * the race explained above.
221 info->si_pkey = *pkey;
225 force_sig_info_fault(int si_signo, int si_code, unsigned long address,
226 struct task_struct *tsk, u32 *pkey, int fault)
231 info.si_signo = si_signo;
233 info.si_code = si_code;
234 info.si_addr = (void __user *)address;
235 if (fault & VM_FAULT_HWPOISON_LARGE)
236 lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
237 if (fault & VM_FAULT_HWPOISON)
239 info.si_addr_lsb = lsb;
241 fill_sig_info_pkey(si_code, &info, pkey);
243 force_sig_info(si_signo, &info, tsk);
246 DEFINE_SPINLOCK(pgd_lock);
250 static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
252 unsigned index = pgd_index(address);
259 pgd_k = init_mm.pgd + index;
261 if (!pgd_present(*pgd_k))
265 * set_pgd(pgd, *pgd_k); here would be useless on PAE
266 * and redundant with the set_pmd() on non-PAE. As would
269 p4d = p4d_offset(pgd, address);
270 p4d_k = p4d_offset(pgd_k, address);
271 if (!p4d_present(*p4d_k))
274 pud = pud_offset(p4d, address);
275 pud_k = pud_offset(p4d_k, address);
276 if (!pud_present(*pud_k))
279 pmd = pmd_offset(pud, address);
280 pmd_k = pmd_offset(pud_k, address);
281 if (!pmd_present(*pmd_k))
284 if (!pmd_present(*pmd))
285 set_pmd(pmd, *pmd_k);
287 BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k));
292 void vmalloc_sync_all(void)
294 unsigned long address;
296 if (SHARED_KERNEL_PMD)
299 for (address = VMALLOC_START & PMD_MASK;
300 address >= TASK_SIZE_MAX && address < FIXADDR_TOP;
301 address += PMD_SIZE) {
304 spin_lock(&pgd_lock);
305 list_for_each_entry(page, &pgd_list, lru) {
306 spinlock_t *pgt_lock;
309 /* the pgt_lock only for Xen */
310 pgt_lock = &pgd_page_get_mm(page)->page_table_lock;
313 ret = vmalloc_sync_one(page_address(page), address);
314 spin_unlock(pgt_lock);
319 spin_unlock(&pgd_lock);
326 * Handle a fault on the vmalloc or module mapping area
328 static noinline int vmalloc_fault(unsigned long address)
330 unsigned long pgd_paddr;
334 /* Make sure we are in vmalloc area: */
335 if (!(address >= VMALLOC_START && address < VMALLOC_END))
338 WARN_ON_ONCE(in_nmi());
341 * Synchronize this task's top level page-table
342 * with the 'reference' page table.
344 * Do _not_ use "current" here. We might be inside
345 * an interrupt in the middle of a task switch..
347 pgd_paddr = read_cr3_pa();
348 pmd_k = vmalloc_sync_one(__va(pgd_paddr), address);
352 if (pmd_huge(*pmd_k))
355 pte_k = pte_offset_kernel(pmd_k, address);
356 if (!pte_present(*pte_k))
361 NOKPROBE_SYMBOL(vmalloc_fault);
364 * Did it hit the DOS screen memory VA from vm86 mode?
367 check_v8086_mode(struct pt_regs *regs, unsigned long address,
368 struct task_struct *tsk)
373 if (!v8086_mode(regs) || !tsk->thread.vm86)
376 bit = (address - 0xA0000) >> PAGE_SHIFT;
378 tsk->thread.vm86->screen_bitmap |= 1 << bit;
382 static bool low_pfn(unsigned long pfn)
384 return pfn < max_low_pfn;
387 static void dump_pagetable(unsigned long address)
389 pgd_t *base = __va(read_cr3_pa());
390 pgd_t *pgd = &base[pgd_index(address)];
396 #ifdef CONFIG_X86_PAE
397 pr_info("*pdpt = %016Lx ", pgd_val(*pgd));
398 if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd))
400 #define pr_pde pr_cont
402 #define pr_pde pr_info
404 p4d = p4d_offset(pgd, address);
405 pud = pud_offset(p4d, address);
406 pmd = pmd_offset(pud, address);
407 pr_pde("*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd));
411 * We must not directly access the pte in the highpte
412 * case if the page table is located in highmem.
413 * And let's rather not kmap-atomic the pte, just in case
414 * it's allocated already:
416 if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_large(*pmd))
419 pte = pte_offset_kernel(pmd, address);
420 pr_cont("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte));
425 #else /* CONFIG_X86_64: */
427 void vmalloc_sync_all(void)
429 sync_global_pgds(VMALLOC_START & PGDIR_MASK, VMALLOC_END);
435 * Handle a fault on the vmalloc area
437 static noinline int vmalloc_fault(unsigned long address)
439 pgd_t *pgd, *pgd_ref;
440 p4d_t *p4d, *p4d_ref;
441 pud_t *pud, *pud_ref;
442 pmd_t *pmd, *pmd_ref;
443 pte_t *pte, *pte_ref;
445 /* Make sure we are in vmalloc area: */
446 if (!(address >= VMALLOC_START && address < VMALLOC_END))
449 WARN_ON_ONCE(in_nmi());
452 * Copy kernel mappings over when needed. This can also
453 * happen within a race in page table update. In the later
456 pgd = (pgd_t *)__va(read_cr3_pa()) + pgd_index(address);
457 pgd_ref = pgd_offset_k(address);
458 if (pgd_none(*pgd_ref))
461 if (pgd_none(*pgd)) {
462 set_pgd(pgd, *pgd_ref);
463 arch_flush_lazy_mmu_mode();
464 } else if (CONFIG_PGTABLE_LEVELS > 4) {
466 * With folded p4d, pgd_none() is always false, so the pgd may
467 * point to an empty page table entry and pgd_page_vaddr()
468 * will return garbage.
470 * We will do the correct sanity check on the p4d level.
472 BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref));
475 /* With 4-level paging, copying happens on the p4d level. */
476 p4d = p4d_offset(pgd, address);
477 p4d_ref = p4d_offset(pgd_ref, address);
478 if (p4d_none(*p4d_ref))
481 if (p4d_none(*p4d)) {
482 set_p4d(p4d, *p4d_ref);
483 arch_flush_lazy_mmu_mode();
485 BUG_ON(p4d_pfn(*p4d) != p4d_pfn(*p4d_ref));
489 * Below here mismatches are bugs because these lower tables
493 pud = pud_offset(p4d, address);
494 pud_ref = pud_offset(p4d_ref, address);
495 if (pud_none(*pud_ref))
498 if (pud_none(*pud) || pud_pfn(*pud) != pud_pfn(*pud_ref))
504 pmd = pmd_offset(pud, address);
505 pmd_ref = pmd_offset(pud_ref, address);
506 if (pmd_none(*pmd_ref))
509 if (pmd_none(*pmd) || pmd_pfn(*pmd) != pmd_pfn(*pmd_ref))
515 pte_ref = pte_offset_kernel(pmd_ref, address);
516 if (!pte_present(*pte_ref))
519 pte = pte_offset_kernel(pmd, address);
522 * Don't use pte_page here, because the mappings can point
523 * outside mem_map, and the NUMA hash lookup cannot handle
526 if (!pte_present(*pte) || pte_pfn(*pte) != pte_pfn(*pte_ref))
531 NOKPROBE_SYMBOL(vmalloc_fault);
533 #ifdef CONFIG_CPU_SUP_AMD
534 static const char errata93_warning[] =
536 "******* Your BIOS seems to not contain a fix for K8 errata #93\n"
537 "******* Working around it, but it may cause SEGVs or burn power.\n"
538 "******* Please consider a BIOS update.\n"
539 "******* Disabling USB legacy in the BIOS may also help.\n";
543 * No vm86 mode in 64-bit mode:
546 check_v8086_mode(struct pt_regs *regs, unsigned long address,
547 struct task_struct *tsk)
551 static int bad_address(void *p)
555 return probe_kernel_address((unsigned long *)p, dummy);
558 static void dump_pagetable(unsigned long address)
560 pgd_t *base = __va(read_cr3_pa());
561 pgd_t *pgd = base + pgd_index(address);
567 if (bad_address(pgd))
570 pr_info("PGD %lx ", pgd_val(*pgd));
572 if (!pgd_present(*pgd))
575 p4d = p4d_offset(pgd, address);
576 if (bad_address(p4d))
579 pr_cont("P4D %lx ", p4d_val(*p4d));
580 if (!p4d_present(*p4d) || p4d_large(*p4d))
583 pud = pud_offset(p4d, address);
584 if (bad_address(pud))
587 pr_cont("PUD %lx ", pud_val(*pud));
588 if (!pud_present(*pud) || pud_large(*pud))
591 pmd = pmd_offset(pud, address);
592 if (bad_address(pmd))
595 pr_cont("PMD %lx ", pmd_val(*pmd));
596 if (!pmd_present(*pmd) || pmd_large(*pmd))
599 pte = pte_offset_kernel(pmd, address);
600 if (bad_address(pte))
603 pr_cont("PTE %lx", pte_val(*pte));
611 #endif /* CONFIG_X86_64 */
614 * Workaround for K8 erratum #93 & buggy BIOS.
616 * BIOS SMM functions are required to use a specific workaround
617 * to avoid corruption of the 64bit RIP register on C stepping K8.
619 * A lot of BIOS that didn't get tested properly miss this.
621 * The OS sees this as a page fault with the upper 32bits of RIP cleared.
622 * Try to work around it here.
624 * Note we only handle faults in kernel here.
625 * Does nothing on 32-bit.
627 static int is_errata93(struct pt_regs *regs, unsigned long address)
629 #if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD)
630 if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD
631 || boot_cpu_data.x86 != 0xf)
634 if (address != regs->ip)
637 if ((address >> 32) != 0)
640 address |= 0xffffffffUL << 32;
641 if ((address >= (u64)_stext && address <= (u64)_etext) ||
642 (address >= MODULES_VADDR && address <= MODULES_END)) {
643 printk_once(errata93_warning);
652 * Work around K8 erratum #100 K8 in compat mode occasionally jumps
653 * to illegal addresses >4GB.
655 * We catch this in the page fault handler because these addresses
656 * are not reachable. Just detect this case and return. Any code
657 * segment in LDT is compatibility mode.
659 static int is_errata100(struct pt_regs *regs, unsigned long address)
662 if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32))
668 static int is_f00f_bug(struct pt_regs *regs, unsigned long address)
670 #ifdef CONFIG_X86_F00F_BUG
674 * Pentium F0 0F C7 C8 bug workaround:
676 if (boot_cpu_has_bug(X86_BUG_F00F)) {
677 nr = (address - idt_descr.address) >> 3;
680 do_invalid_op(regs, 0);
688 static const char nx_warning[] = KERN_CRIT
689 "kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n";
690 static const char smep_warning[] = KERN_CRIT
691 "unable to execute userspace code (SMEP?) (uid: %d)\n";
694 show_fault_oops(struct pt_regs *regs, unsigned long error_code,
695 unsigned long address)
697 if (!oops_may_print())
700 if (error_code & PF_INSTR) {
705 pgd = __va(read_cr3_pa());
706 pgd += pgd_index(address);
708 pte = lookup_address_in_pgd(pgd, address, &level);
710 if (pte && pte_present(*pte) && !pte_exec(*pte))
711 printk(nx_warning, from_kuid(&init_user_ns, current_uid()));
712 if (pte && pte_present(*pte) && pte_exec(*pte) &&
713 (pgd_flags(*pgd) & _PAGE_USER) &&
714 (__read_cr4() & X86_CR4_SMEP))
715 printk(smep_warning, from_kuid(&init_user_ns, current_uid()));
718 printk(KERN_ALERT "BUG: unable to handle kernel ");
719 if (address < PAGE_SIZE)
720 printk(KERN_CONT "NULL pointer dereference");
722 printk(KERN_CONT "paging request");
724 printk(KERN_CONT " at %p\n", (void *) address);
725 printk(KERN_ALERT "IP: %pS\n", (void *)regs->ip);
727 dump_pagetable(address);
731 pgtable_bad(struct pt_regs *regs, unsigned long error_code,
732 unsigned long address)
734 struct task_struct *tsk;
738 flags = oops_begin();
742 printk(KERN_ALERT "%s: Corrupted page table at address %lx\n",
744 dump_pagetable(address);
746 tsk->thread.cr2 = address;
747 tsk->thread.trap_nr = X86_TRAP_PF;
748 tsk->thread.error_code = error_code;
750 if (__die("Bad pagetable", regs, error_code))
753 oops_end(flags, regs, sig);
757 no_context(struct pt_regs *regs, unsigned long error_code,
758 unsigned long address, int signal, int si_code)
760 struct task_struct *tsk = current;
764 /* Are we prepared to handle this kernel fault? */
765 if (fixup_exception(regs, X86_TRAP_PF)) {
767 * Any interrupt that takes a fault gets the fixup. This makes
768 * the below recursive fault logic only apply to a faults from
775 * Per the above we're !in_interrupt(), aka. task context.
777 * In this case we need to make sure we're not recursively
778 * faulting through the emulate_vsyscall() logic.
780 if (current->thread.sig_on_uaccess_err && signal) {
781 tsk->thread.trap_nr = X86_TRAP_PF;
782 tsk->thread.error_code = error_code | PF_USER;
783 tsk->thread.cr2 = address;
785 /* XXX: hwpoison faults will set the wrong code. */
786 force_sig_info_fault(signal, si_code, address,
791 * Barring that, we can do the fixup and be happy.
796 #ifdef CONFIG_VMAP_STACK
798 * Stack overflow? During boot, we can fault near the initial
799 * stack in the direct map, but that's not an overflow -- check
800 * that we're in vmalloc space to avoid this.
802 if (is_vmalloc_addr((void *)address) &&
803 (((unsigned long)tsk->stack - 1 - address < PAGE_SIZE) ||
804 address - ((unsigned long)tsk->stack + THREAD_SIZE) < PAGE_SIZE)) {
805 unsigned long stack = this_cpu_read(orig_ist.ist[DOUBLEFAULT_STACK]) - sizeof(void *);
807 * We're likely to be running with very little stack space
808 * left. It's plausible that we'd hit this condition but
809 * double-fault even before we get this far, in which case
810 * we're fine: the double-fault handler will deal with it.
812 * We don't want to make it all the way into the oops code
813 * and then double-fault, though, because we're likely to
814 * break the console driver and lose most of the stack dump.
816 asm volatile ("movq %[stack], %%rsp\n\t"
817 "call handle_stack_overflow\n\t"
819 : ASM_CALL_CONSTRAINT
820 : "D" ("kernel stack overflow (page fault)"),
821 "S" (regs), "d" (address),
822 [stack] "rm" (stack));
830 * Valid to do another page fault here, because if this fault
831 * had been triggered by is_prefetch fixup_exception would have
836 * Hall of shame of CPU/BIOS bugs.
838 if (is_prefetch(regs, error_code, address))
841 if (is_errata93(regs, address))
845 * Oops. The kernel tried to access some bad page. We'll have to
846 * terminate things with extreme prejudice:
848 flags = oops_begin();
850 show_fault_oops(regs, error_code, address);
852 if (task_stack_end_corrupted(tsk))
853 printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");
855 tsk->thread.cr2 = address;
856 tsk->thread.trap_nr = X86_TRAP_PF;
857 tsk->thread.error_code = error_code;
860 if (__die("Oops", regs, error_code))
863 /* Executive summary in case the body of the oops scrolled away */
864 printk(KERN_DEFAULT "CR2: %016lx\n", address);
866 oops_end(flags, regs, sig);
870 * Print out info about fatal segfaults, if the show_unhandled_signals
874 show_signal_msg(struct pt_regs *regs, unsigned long error_code,
875 unsigned long address, struct task_struct *tsk)
877 if (!unhandled_signal(tsk, SIGSEGV))
880 if (!printk_ratelimit())
883 printk("%s%s[%d]: segfault at %lx ip %p sp %p error %lx",
884 task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
885 tsk->comm, task_pid_nr(tsk), address,
886 (void *)regs->ip, (void *)regs->sp, error_code);
888 print_vma_addr(KERN_CONT " in ", regs->ip);
890 printk(KERN_CONT "\n");
894 __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
895 unsigned long address, u32 *pkey, int si_code)
897 struct task_struct *tsk = current;
899 /* User mode accesses just cause a SIGSEGV */
900 if (error_code & PF_USER) {
902 * It's possible to have interrupts off here:
907 * Valid to do another page fault here because this one came
910 if (is_prefetch(regs, error_code, address))
913 if (is_errata100(regs, address))
918 * Instruction fetch faults in the vsyscall page might need
921 if (unlikely((error_code & PF_INSTR) &&
922 ((address & ~0xfff) == VSYSCALL_ADDR))) {
923 if (emulate_vsyscall(regs, address))
929 * To avoid leaking information about the kernel page table
930 * layout, pretend that user-mode accesses to kernel addresses
931 * are always protection faults.
933 if (address >= TASK_SIZE_MAX)
934 error_code |= PF_PROT;
936 if (likely(show_unhandled_signals))
937 show_signal_msg(regs, error_code, address, tsk);
939 tsk->thread.cr2 = address;
940 tsk->thread.error_code = error_code;
941 tsk->thread.trap_nr = X86_TRAP_PF;
943 force_sig_info_fault(SIGSEGV, si_code, address, tsk, pkey, 0);
948 if (is_f00f_bug(regs, address))
951 no_context(regs, error_code, address, SIGSEGV, si_code);
955 bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
956 unsigned long address, u32 *pkey)
958 __bad_area_nosemaphore(regs, error_code, address, pkey, SEGV_MAPERR);
962 __bad_area(struct pt_regs *regs, unsigned long error_code,
963 unsigned long address, struct vm_area_struct *vma, int si_code)
965 struct mm_struct *mm = current->mm;
969 pkey = vma_pkey(vma);
972 * Something tried to access memory that isn't in our memory map..
973 * Fix it, but check if it's kernel or user first..
975 up_read(&mm->mmap_sem);
977 __bad_area_nosemaphore(regs, error_code, address,
978 (vma) ? &pkey : NULL, si_code);
982 bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address)
984 __bad_area(regs, error_code, address, NULL, SEGV_MAPERR);
987 static inline bool bad_area_access_from_pkeys(unsigned long error_code,
988 struct vm_area_struct *vma)
990 /* This code is always called on the current mm */
991 bool foreign = false;
993 if (!boot_cpu_has(X86_FEATURE_OSPKE))
995 if (error_code & PF_PK)
997 /* this checks permission keys on the VMA: */
998 if (!arch_vma_access_permitted(vma, (error_code & PF_WRITE),
999 (error_code & PF_INSTR), foreign))
1004 static noinline void
1005 bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
1006 unsigned long address, struct vm_area_struct *vma)
1009 * This OSPKE check is not strictly necessary at runtime.
1010 * But, doing it this way allows compiler optimizations
1011 * if pkeys are compiled out.
1013 if (bad_area_access_from_pkeys(error_code, vma))
1014 __bad_area(regs, error_code, address, vma, SEGV_PKUERR);
1016 __bad_area(regs, error_code, address, vma, SEGV_ACCERR);
1020 do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
1021 u32 *pkey, unsigned int fault)
1023 struct task_struct *tsk = current;
1024 int code = BUS_ADRERR;
1026 /* Kernel mode? Handle exceptions or die: */
1027 if (!(error_code & PF_USER)) {
1028 no_context(regs, error_code, address, SIGBUS, BUS_ADRERR);
1032 /* User-space => ok to do another page fault: */
1033 if (is_prefetch(regs, error_code, address))
1036 tsk->thread.cr2 = address;
1037 tsk->thread.error_code = error_code;
1038 tsk->thread.trap_nr = X86_TRAP_PF;
1040 #ifdef CONFIG_MEMORY_FAILURE
1041 if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
1043 "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
1044 tsk->comm, tsk->pid, address);
1045 code = BUS_MCEERR_AR;
1048 force_sig_info_fault(SIGBUS, code, address, tsk, pkey, fault);
1051 static noinline void
1052 mm_fault_error(struct pt_regs *regs, unsigned long error_code,
1053 unsigned long address, u32 *pkey, unsigned int fault)
1055 if (fatal_signal_pending(current) && !(error_code & PF_USER)) {
1056 no_context(regs, error_code, address, 0, 0);
1060 if (fault & VM_FAULT_OOM) {
1061 /* Kernel mode? Handle exceptions or die: */
1062 if (!(error_code & PF_USER)) {
1063 no_context(regs, error_code, address,
1064 SIGSEGV, SEGV_MAPERR);
1069 * We ran out of memory, call the OOM killer, and return the
1070 * userspace (which will retry the fault, or kill us if we got
1073 pagefault_out_of_memory();
1075 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
1076 VM_FAULT_HWPOISON_LARGE))
1077 do_sigbus(regs, error_code, address, pkey, fault);
1078 else if (fault & VM_FAULT_SIGSEGV)
1079 bad_area_nosemaphore(regs, error_code, address, pkey);
1085 static int spurious_fault_check(unsigned long error_code, pte_t *pte)
1087 if ((error_code & PF_WRITE) && !pte_write(*pte))
1090 if ((error_code & PF_INSTR) && !pte_exec(*pte))
1093 * Note: We do not do lazy flushing on protection key
1094 * changes, so no spurious fault will ever set PF_PK.
1096 if ((error_code & PF_PK))
1103 * Handle a spurious fault caused by a stale TLB entry.
1105 * This allows us to lazily refresh the TLB when increasing the
1106 * permissions of a kernel page (RO -> RW or NX -> X). Doing it
1107 * eagerly is very expensive since that implies doing a full
1108 * cross-processor TLB flush, even if no stale TLB entries exist
1109 * on other processors.
1111 * Spurious faults may only occur if the TLB contains an entry with
1112 * fewer permission than the page table entry. Non-present (P = 0)
1113 * and reserved bit (R = 1) faults are never spurious.
1115 * There are no security implications to leaving a stale TLB when
1116 * increasing the permissions on a page.
1118 * Returns non-zero if a spurious fault was handled, zero otherwise.
1120 * See Intel Developer's Manual Vol 3 Section 4.10.4.3, bullet 3
1121 * (Optional Invalidation).
1124 spurious_fault(unsigned long error_code, unsigned long address)
1134 * Only writes to RO or instruction fetches from NX may cause
1137 * These could be from user or supervisor accesses but the TLB
1138 * is only lazily flushed after a kernel mapping protection
1139 * change, so user accesses are not expected to cause spurious
1142 if (error_code != (PF_WRITE | PF_PROT)
1143 && error_code != (PF_INSTR | PF_PROT))
1146 pgd = init_mm.pgd + pgd_index(address);
1147 if (!pgd_present(*pgd))
1150 p4d = p4d_offset(pgd, address);
1151 if (!p4d_present(*p4d))
1154 if (p4d_large(*p4d))
1155 return spurious_fault_check(error_code, (pte_t *) p4d);
1157 pud = pud_offset(p4d, address);
1158 if (!pud_present(*pud))
1161 if (pud_large(*pud))
1162 return spurious_fault_check(error_code, (pte_t *) pud);
1164 pmd = pmd_offset(pud, address);
1165 if (!pmd_present(*pmd))
1168 if (pmd_large(*pmd))
1169 return spurious_fault_check(error_code, (pte_t *) pmd);
1171 pte = pte_offset_kernel(pmd, address);
1172 if (!pte_present(*pte))
1175 ret = spurious_fault_check(error_code, pte);
1180 * Make sure we have permissions in PMD.
1181 * If not, then there's a bug in the page tables:
1183 ret = spurious_fault_check(error_code, (pte_t *) pmd);
1184 WARN_ONCE(!ret, "PMD has incorrect permission bits\n");
1188 NOKPROBE_SYMBOL(spurious_fault);
1190 int show_unhandled_signals = 1;
1193 access_error(unsigned long error_code, struct vm_area_struct *vma)
1195 /* This is only called for the current mm, so: */
1196 bool foreign = false;
1199 * Read or write was blocked by protection keys. This is
1200 * always an unconditional error and can never result in
1201 * a follow-up action to resolve the fault, like a COW.
1203 if (error_code & PF_PK)
1207 * Make sure to check the VMA so that we do not perform
1208 * faults just to hit a PF_PK as soon as we fill in a
1211 if (!arch_vma_access_permitted(vma, (error_code & PF_WRITE),
1212 (error_code & PF_INSTR), foreign))
1215 if (error_code & PF_WRITE) {
1216 /* write, present and write, not present: */
1217 if (unlikely(!(vma->vm_flags & VM_WRITE)))
1222 /* read, present: */
1223 if (unlikely(error_code & PF_PROT))
1226 /* read, not present: */
1227 if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))))
1233 static int fault_in_kernel_space(unsigned long address)
1235 return address >= TASK_SIZE_MAX;
1238 static inline bool smap_violation(int error_code, struct pt_regs *regs)
1240 if (!IS_ENABLED(CONFIG_X86_SMAP))
1243 if (!static_cpu_has(X86_FEATURE_SMAP))
1246 if (error_code & PF_USER)
1249 if (!user_mode(regs) && (regs->flags & X86_EFLAGS_AC))
1256 * This routine handles page faults. It determines the address,
1257 * and the problem, and then passes it off to one of the appropriate
1260 static noinline void
1261 __do_page_fault(struct pt_regs *regs, unsigned long error_code,
1262 unsigned long address)
1264 struct vm_area_struct *vma;
1265 struct task_struct *tsk;
1266 struct mm_struct *mm;
1267 int fault, major = 0;
1268 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
1275 * Detect and handle instructions that would cause a page fault for
1276 * both a tracked kernel page and a userspace page.
1278 if (kmemcheck_active(regs))
1279 kmemcheck_hide(regs);
1280 prefetchw(&mm->mmap_sem);
1282 if (unlikely(kmmio_fault(regs, address)))
1286 * We fault-in kernel-space virtual memory on-demand. The
1287 * 'reference' page table is init_mm.pgd.
1289 * NOTE! We MUST NOT take any locks for this case. We may
1290 * be in an interrupt or a critical region, and should
1291 * only copy the information from the master page table,
1294 * This verifies that the fault happens in kernel space
1295 * (error_code & 4) == 0, and that the fault was not a
1296 * protection error (error_code & 9) == 0.
1298 if (unlikely(fault_in_kernel_space(address))) {
1299 if (!(error_code & (PF_RSVD | PF_USER | PF_PROT))) {
1300 if (vmalloc_fault(address) >= 0)
1303 if (kmemcheck_fault(regs, address, error_code))
1307 /* Can handle a stale RO->RW TLB: */
1308 if (spurious_fault(error_code, address))
1311 /* kprobes don't want to hook the spurious faults: */
1312 if (kprobes_fault(regs))
1315 * Don't take the mm semaphore here. If we fixup a prefetch
1316 * fault we could otherwise deadlock:
1318 bad_area_nosemaphore(regs, error_code, address, NULL);
1323 /* kprobes don't want to hook the spurious faults: */
1324 if (unlikely(kprobes_fault(regs)))
1327 if (unlikely(error_code & PF_RSVD))
1328 pgtable_bad(regs, error_code, address);
1330 if (unlikely(smap_violation(error_code, regs))) {
1331 bad_area_nosemaphore(regs, error_code, address, NULL);
1336 * If we're in an interrupt, have no user context or are running
1337 * in a region with pagefaults disabled then we must not take the fault
1339 if (unlikely(faulthandler_disabled() || !mm)) {
1340 bad_area_nosemaphore(regs, error_code, address, NULL);
1345 * It's safe to allow irq's after cr2 has been saved and the
1346 * vmalloc fault has been handled.
1348 * User-mode registers count as a user access even for any
1349 * potential system fault or CPU buglet:
1351 if (user_mode(regs)) {
1353 error_code |= PF_USER;
1354 flags |= FAULT_FLAG_USER;
1356 if (regs->flags & X86_EFLAGS_IF)
1360 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
1362 if (error_code & PF_WRITE)
1363 flags |= FAULT_FLAG_WRITE;
1364 if (error_code & PF_INSTR)
1365 flags |= FAULT_FLAG_INSTRUCTION;
1368 * When running in the kernel we expect faults to occur only to
1369 * addresses in user space. All other faults represent errors in
1370 * the kernel and should generate an OOPS. Unfortunately, in the
1371 * case of an erroneous fault occurring in a code path which already
1372 * holds mmap_sem we will deadlock attempting to validate the fault
1373 * against the address space. Luckily the kernel only validly
1374 * references user space from well defined areas of code, which are
1375 * listed in the exceptions table.
1377 * As the vast majority of faults will be valid we will only perform
1378 * the source reference check when there is a possibility of a
1379 * deadlock. Attempt to lock the address space, if we cannot we then
1380 * validate the source. If this is invalid we can skip the address
1381 * space check, thus avoiding the deadlock:
1383 if (unlikely(!down_read_trylock(&mm->mmap_sem))) {
1384 if ((error_code & PF_USER) == 0 &&
1385 !search_exception_tables(regs->ip)) {
1386 bad_area_nosemaphore(regs, error_code, address, NULL);
1390 down_read(&mm->mmap_sem);
1393 * The above down_read_trylock() might have succeeded in
1394 * which case we'll have missed the might_sleep() from
1400 vma = find_vma(mm, address);
1401 if (unlikely(!vma)) {
1402 bad_area(regs, error_code, address);
1405 if (likely(vma->vm_start <= address))
1407 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
1408 bad_area(regs, error_code, address);
1411 if (error_code & PF_USER) {
1413 * Accessing the stack below %sp is always a bug.
1414 * The large cushion allows instructions like enter
1415 * and pusha to work. ("enter $65535, $31" pushes
1416 * 32 pointers and then decrements %sp by 65535.)
1418 if (unlikely(address + 65536 + 32 * sizeof(unsigned long) < regs->sp)) {
1419 bad_area(regs, error_code, address);
1423 if (unlikely(expand_stack(vma, address))) {
1424 bad_area(regs, error_code, address);
1429 * Ok, we have a good vm_area for this memory access, so
1430 * we can handle it..
1433 if (unlikely(access_error(error_code, vma))) {
1434 bad_area_access_error(regs, error_code, address, vma);
1439 * If for any reason at all we couldn't handle the fault,
1440 * make sure we exit gracefully rather than endlessly redo
1441 * the fault. Since we never set FAULT_FLAG_RETRY_NOWAIT, if
1442 * we get VM_FAULT_RETRY back, the mmap_sem has been unlocked.
1444 fault = handle_mm_fault(vma, address, flags);
1445 major |= fault & VM_FAULT_MAJOR;
1448 * If we need to retry the mmap_sem has already been released,
1449 * and if there is a fatal signal pending there is no guarantee
1450 * that we made any progress. Handle this case first.
1452 if (unlikely(fault & VM_FAULT_RETRY)) {
1453 /* Retry at most once */
1454 if (flags & FAULT_FLAG_ALLOW_RETRY) {
1455 flags &= ~FAULT_FLAG_ALLOW_RETRY;
1456 flags |= FAULT_FLAG_TRIED;
1457 if (!fatal_signal_pending(tsk))
1461 /* User mode? Just return to handle the fatal exception */
1462 if (flags & FAULT_FLAG_USER)
1465 /* Not returning to user mode? Handle exceptions or die: */
1466 no_context(regs, error_code, address, SIGBUS, BUS_ADRERR);
1470 pkey = vma_pkey(vma);
1471 up_read(&mm->mmap_sem);
1472 if (unlikely(fault & VM_FAULT_ERROR)) {
1473 mm_fault_error(regs, error_code, address, &pkey, fault);
1478 * Major/minor page fault accounting. If any of the events
1479 * returned VM_FAULT_MAJOR, we account it as a major fault.
1483 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address);
1486 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address);
1489 check_v8086_mode(regs, address, tsk);
1491 NOKPROBE_SYMBOL(__do_page_fault);
1493 static nokprobe_inline void
1494 trace_page_fault_entries(unsigned long address, struct pt_regs *regs,
1495 unsigned long error_code)
1497 if (user_mode(regs))
1498 trace_page_fault_user(address, regs, error_code);
1500 trace_page_fault_kernel(address, regs, error_code);
1504 * We must have this function blacklisted from kprobes, tagged with notrace
1505 * and call read_cr2() before calling anything else. To avoid calling any
1506 * kind of tracing machinery before we've observed the CR2 value.
1508 * exception_{enter,exit}() contains all sorts of tracepoints.
1510 dotraplinkage void notrace
1511 do_page_fault(struct pt_regs *regs, unsigned long error_code)
1513 unsigned long address = read_cr2(); /* Get the faulting address */
1514 enum ctx_state prev_state;
1516 prev_state = exception_enter();
1517 if (trace_pagefault_enabled())
1518 trace_page_fault_entries(address, regs, error_code);
1520 __do_page_fault(regs, error_code, address);
1521 exception_exit(prev_state);
1523 NOKPROBE_SYMBOL(do_page_fault);