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 */