2 * Copyright (C) 1995 Linus Torvalds
3 * Copyright (C) 2001, 2002 Andi Kleen, SuSE Labs.
4 * Copyright (C) 2008-2009, Red Hat Inc., Ingo Molnar
6 #include <linux/magic.h> /* STACK_END_MAGIC */
7 #include <linux/sched.h> /* test_thread_flag(), ... */
8 #include <linux/kdebug.h> /* oops_begin/end, ... */
9 #include <linux/module.h> /* search_exception_table */
10 #include <linux/bootmem.h> /* max_low_pfn */
11 #include <linux/kprobes.h> /* 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(), ... */
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_vm(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
)
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
;
652 unsigned long *stackend
;
656 /* Are we prepared to handle this kernel fault? */
657 if (fixup_exception(regs
)) {
659 * Any interrupt that takes a fault gets the fixup. This makes
660 * the below recursive fault logic only apply to a faults from
667 * Per the above we're !in_interrupt(), aka. task context.
669 * In this case we need to make sure we're not recursively
670 * faulting through the emulate_vsyscall() logic.
672 if (current_thread_info()->sig_on_uaccess_error
&& signal
) {
673 tsk
->thread
.trap_nr
= X86_TRAP_PF
;
674 tsk
->thread
.error_code
= error_code
| PF_USER
;
675 tsk
->thread
.cr2
= address
;
677 /* XXX: hwpoison faults will set the wrong code. */
678 force_sig_info_fault(signal
, si_code
, address
, tsk
, 0);
682 * Barring that, we can do the fixup and be happy.
690 * Valid to do another page fault here, because if this fault
691 * had been triggered by is_prefetch fixup_exception would have
696 * Hall of shame of CPU/BIOS bugs.
698 if (is_prefetch(regs
, error_code
, address
))
701 if (is_errata93(regs
, address
))
705 * Oops. The kernel tried to access some bad page. We'll have to
706 * terminate things with extreme prejudice:
708 flags
= oops_begin();
710 show_fault_oops(regs
, error_code
, address
);
712 stackend
= end_of_stack(tsk
);
713 if (tsk
!= &init_task
&& *stackend
!= STACK_END_MAGIC
)
714 printk(KERN_EMERG
"Thread overran stack, or stack corrupted\n");
716 tsk
->thread
.cr2
= address
;
717 tsk
->thread
.trap_nr
= X86_TRAP_PF
;
718 tsk
->thread
.error_code
= error_code
;
721 if (__die("Oops", regs
, error_code
))
724 /* Executive summary in case the body of the oops scrolled away */
725 printk(KERN_DEFAULT
"CR2: %016lx\n", address
);
727 oops_end(flags
, regs
, sig
);
731 * Print out info about fatal segfaults, if the show_unhandled_signals
735 show_signal_msg(struct pt_regs
*regs
, unsigned long error_code
,
736 unsigned long address
, struct task_struct
*tsk
)
738 if (!unhandled_signal(tsk
, SIGSEGV
))
741 if (!printk_ratelimit())
744 printk("%s%s[%d]: segfault at %lx ip %p sp %p error %lx",
745 task_pid_nr(tsk
) > 1 ? KERN_INFO
: KERN_EMERG
,
746 tsk
->comm
, task_pid_nr(tsk
), address
,
747 (void *)regs
->ip
, (void *)regs
->sp
, error_code
);
749 print_vma_addr(KERN_CONT
" in ", regs
->ip
);
751 printk(KERN_CONT
"\n");
755 __bad_area_nosemaphore(struct pt_regs
*regs
, unsigned long error_code
,
756 unsigned long address
, int si_code
)
758 struct task_struct
*tsk
= current
;
760 /* User mode accesses just cause a SIGSEGV */
761 if (error_code
& PF_USER
) {
763 * It's possible to have interrupts off here:
768 * Valid to do another page fault here because this one came
771 if (is_prefetch(regs
, error_code
, address
))
774 if (is_errata100(regs
, address
))
779 * Instruction fetch faults in the vsyscall page might need
782 if (unlikely((error_code
& PF_INSTR
) &&
783 ((address
& ~0xfff) == VSYSCALL_ADDR
))) {
784 if (emulate_vsyscall(regs
, address
))
788 /* Kernel addresses are always protection faults: */
789 if (address
>= TASK_SIZE
)
790 error_code
|= PF_PROT
;
792 if (likely(show_unhandled_signals
))
793 show_signal_msg(regs
, error_code
, address
, tsk
);
795 tsk
->thread
.cr2
= address
;
796 tsk
->thread
.error_code
= error_code
;
797 tsk
->thread
.trap_nr
= X86_TRAP_PF
;
799 force_sig_info_fault(SIGSEGV
, si_code
, address
, tsk
, 0);
804 if (is_f00f_bug(regs
, address
))
807 no_context(regs
, error_code
, address
, SIGSEGV
, si_code
);
811 bad_area_nosemaphore(struct pt_regs
*regs
, unsigned long error_code
,
812 unsigned long address
)
814 __bad_area_nosemaphore(regs
, error_code
, address
, SEGV_MAPERR
);
818 __bad_area(struct pt_regs
*regs
, unsigned long error_code
,
819 unsigned long address
, int si_code
)
821 struct mm_struct
*mm
= current
->mm
;
824 * Something tried to access memory that isn't in our memory map..
825 * Fix it, but check if it's kernel or user first..
827 up_read(&mm
->mmap_sem
);
829 __bad_area_nosemaphore(regs
, error_code
, address
, si_code
);
833 bad_area(struct pt_regs
*regs
, unsigned long error_code
, unsigned long address
)
835 __bad_area(regs
, error_code
, address
, SEGV_MAPERR
);
839 bad_area_access_error(struct pt_regs
*regs
, unsigned long error_code
,
840 unsigned long address
)
842 __bad_area(regs
, error_code
, address
, SEGV_ACCERR
);
846 do_sigbus(struct pt_regs
*regs
, unsigned long error_code
, unsigned long address
,
849 struct task_struct
*tsk
= current
;
850 struct mm_struct
*mm
= tsk
->mm
;
851 int code
= BUS_ADRERR
;
853 up_read(&mm
->mmap_sem
);
855 /* Kernel mode? Handle exceptions or die: */
856 if (!(error_code
& PF_USER
)) {
857 no_context(regs
, error_code
, address
, SIGBUS
, BUS_ADRERR
);
861 /* User-space => ok to do another page fault: */
862 if (is_prefetch(regs
, error_code
, address
))
865 tsk
->thread
.cr2
= address
;
866 tsk
->thread
.error_code
= error_code
;
867 tsk
->thread
.trap_nr
= X86_TRAP_PF
;
869 #ifdef CONFIG_MEMORY_FAILURE
870 if (fault
& (VM_FAULT_HWPOISON
|VM_FAULT_HWPOISON_LARGE
)) {
872 "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
873 tsk
->comm
, tsk
->pid
, address
);
874 code
= BUS_MCEERR_AR
;
877 force_sig_info_fault(SIGBUS
, code
, address
, tsk
, fault
);
881 mm_fault_error(struct pt_regs
*regs
, unsigned long error_code
,
882 unsigned long address
, unsigned int fault
)
884 if (fatal_signal_pending(current
) && !(error_code
& PF_USER
)) {
885 up_read(¤t
->mm
->mmap_sem
);
886 no_context(regs
, error_code
, address
, 0, 0);
890 if (fault
& VM_FAULT_OOM
) {
891 /* Kernel mode? Handle exceptions or die: */
892 if (!(error_code
& PF_USER
)) {
893 up_read(¤t
->mm
->mmap_sem
);
894 no_context(regs
, error_code
, address
,
895 SIGSEGV
, SEGV_MAPERR
);
899 up_read(¤t
->mm
->mmap_sem
);
902 * We ran out of memory, call the OOM killer, and return the
903 * userspace (which will retry the fault, or kill us if we got
906 pagefault_out_of_memory();
908 if (fault
& (VM_FAULT_SIGBUS
|VM_FAULT_HWPOISON
|
909 VM_FAULT_HWPOISON_LARGE
))
910 do_sigbus(regs
, error_code
, address
, fault
);
916 static int spurious_fault_check(unsigned long error_code
, pte_t
*pte
)
918 if ((error_code
& PF_WRITE
) && !pte_write(*pte
))
921 if ((error_code
& PF_INSTR
) && !pte_exec(*pte
))
928 * Handle a spurious fault caused by a stale TLB entry.
930 * This allows us to lazily refresh the TLB when increasing the
931 * permissions of a kernel page (RO -> RW or NX -> X). Doing it
932 * eagerly is very expensive since that implies doing a full
933 * cross-processor TLB flush, even if no stale TLB entries exist
934 * on other processors.
936 * There are no security implications to leaving a stale TLB when
937 * increasing the permissions on a page.
940 spurious_fault(unsigned long error_code
, unsigned long address
)
948 /* Reserved-bit violation or user access to kernel space? */
949 if (error_code
& (PF_USER
| PF_RSVD
))
952 pgd
= init_mm
.pgd
+ pgd_index(address
);
953 if (!pgd_present(*pgd
))
956 pud
= pud_offset(pgd
, address
);
957 if (!pud_present(*pud
))
961 return spurious_fault_check(error_code
, (pte_t
*) pud
);
963 pmd
= pmd_offset(pud
, address
);
964 if (!pmd_present(*pmd
))
968 return spurious_fault_check(error_code
, (pte_t
*) pmd
);
970 pte
= pte_offset_kernel(pmd
, address
);
971 if (!pte_present(*pte
))
974 ret
= spurious_fault_check(error_code
, pte
);
979 * Make sure we have permissions in PMD.
980 * If not, then there's a bug in the page tables:
982 ret
= spurious_fault_check(error_code
, (pte_t
*) pmd
);
983 WARN_ONCE(!ret
, "PMD has incorrect permission bits\n");
987 NOKPROBE_SYMBOL(spurious_fault
);
989 int show_unhandled_signals
= 1;
992 access_error(unsigned long error_code
, struct vm_area_struct
*vma
)
994 if (error_code
& PF_WRITE
) {
995 /* write, present and write, not present: */
996 if (unlikely(!(vma
->vm_flags
& VM_WRITE
)))
1001 /* read, present: */
1002 if (unlikely(error_code
& PF_PROT
))
1005 /* read, not present: */
1006 if (unlikely(!(vma
->vm_flags
& (VM_READ
| VM_EXEC
| VM_WRITE
))))
1012 static int fault_in_kernel_space(unsigned long address
)
1014 return address
>= TASK_SIZE_MAX
;
1017 static inline bool smap_violation(int error_code
, struct pt_regs
*regs
)
1019 if (!IS_ENABLED(CONFIG_X86_SMAP
))
1022 if (!static_cpu_has(X86_FEATURE_SMAP
))
1025 if (error_code
& PF_USER
)
1028 if (!user_mode_vm(regs
) && (regs
->flags
& X86_EFLAGS_AC
))
1035 * This routine handles page faults. It determines the address,
1036 * and the problem, and then passes it off to one of the appropriate
1039 * This function must have noinline because both callers
1040 * {,trace_}do_page_fault() have notrace on. Having this an actual function
1041 * guarantees there's a function trace entry.
1043 static noinline
void
1044 __do_page_fault(struct pt_regs
*regs
, unsigned long error_code
,
1045 unsigned long address
)
1047 struct vm_area_struct
*vma
;
1048 struct task_struct
*tsk
;
1049 struct mm_struct
*mm
;
1051 unsigned int flags
= FAULT_FLAG_ALLOW_RETRY
| FAULT_FLAG_KILLABLE
;
1057 * Detect and handle instructions that would cause a page fault for
1058 * both a tracked kernel page and a userspace page.
1060 if (kmemcheck_active(regs
))
1061 kmemcheck_hide(regs
);
1062 prefetchw(&mm
->mmap_sem
);
1064 if (unlikely(kmmio_fault(regs
, address
)))
1068 * We fault-in kernel-space virtual memory on-demand. The
1069 * 'reference' page table is init_mm.pgd.
1071 * NOTE! We MUST NOT take any locks for this case. We may
1072 * be in an interrupt or a critical region, and should
1073 * only copy the information from the master page table,
1076 * This verifies that the fault happens in kernel space
1077 * (error_code & 4) == 0, and that the fault was not a
1078 * protection error (error_code & 9) == 0.
1080 if (unlikely(fault_in_kernel_space(address
))) {
1081 if (!(error_code
& (PF_RSVD
| PF_USER
| PF_PROT
))) {
1082 if (vmalloc_fault(address
) >= 0)
1085 if (kmemcheck_fault(regs
, address
, error_code
))
1089 /* Can handle a stale RO->RW TLB: */
1090 if (spurious_fault(error_code
, address
))
1093 /* kprobes don't want to hook the spurious faults: */
1094 if (kprobes_fault(regs
))
1097 * Don't take the mm semaphore here. If we fixup a prefetch
1098 * fault we could otherwise deadlock:
1100 bad_area_nosemaphore(regs
, error_code
, address
);
1105 /* kprobes don't want to hook the spurious faults: */
1106 if (unlikely(kprobes_fault(regs
)))
1109 if (unlikely(error_code
& PF_RSVD
))
1110 pgtable_bad(regs
, error_code
, address
);
1112 if (unlikely(smap_violation(error_code
, regs
))) {
1113 bad_area_nosemaphore(regs
, error_code
, address
);
1118 * If we're in an interrupt, have no user context or are running
1119 * in an atomic region then we must not take the fault:
1121 if (unlikely(in_atomic() || !mm
)) {
1122 bad_area_nosemaphore(regs
, error_code
, address
);
1127 * It's safe to allow irq's after cr2 has been saved and the
1128 * vmalloc fault has been handled.
1130 * User-mode registers count as a user access even for any
1131 * potential system fault or CPU buglet:
1133 if (user_mode_vm(regs
)) {
1135 error_code
|= PF_USER
;
1136 flags
|= FAULT_FLAG_USER
;
1138 if (regs
->flags
& X86_EFLAGS_IF
)
1142 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS
, 1, regs
, address
);
1144 if (error_code
& PF_WRITE
)
1145 flags
|= FAULT_FLAG_WRITE
;
1148 * When running in the kernel we expect faults to occur only to
1149 * addresses in user space. All other faults represent errors in
1150 * the kernel and should generate an OOPS. Unfortunately, in the
1151 * case of an erroneous fault occurring in a code path which already
1152 * holds mmap_sem we will deadlock attempting to validate the fault
1153 * against the address space. Luckily the kernel only validly
1154 * references user space from well defined areas of code, which are
1155 * listed in the exceptions table.
1157 * As the vast majority of faults will be valid we will only perform
1158 * the source reference check when there is a possibility of a
1159 * deadlock. Attempt to lock the address space, if we cannot we then
1160 * validate the source. If this is invalid we can skip the address
1161 * space check, thus avoiding the deadlock:
1163 if (unlikely(!down_read_trylock(&mm
->mmap_sem
))) {
1164 if ((error_code
& PF_USER
) == 0 &&
1165 !search_exception_tables(regs
->ip
)) {
1166 bad_area_nosemaphore(regs
, error_code
, address
);
1170 down_read(&mm
->mmap_sem
);
1173 * The above down_read_trylock() might have succeeded in
1174 * which case we'll have missed the might_sleep() from
1180 vma
= find_vma(mm
, address
);
1181 if (unlikely(!vma
)) {
1182 bad_area(regs
, error_code
, address
);
1185 if (likely(vma
->vm_start
<= address
))
1187 if (unlikely(!(vma
->vm_flags
& VM_GROWSDOWN
))) {
1188 bad_area(regs
, error_code
, address
);
1191 if (error_code
& PF_USER
) {
1193 * Accessing the stack below %sp is always a bug.
1194 * The large cushion allows instructions like enter
1195 * and pusha to work. ("enter $65535, $31" pushes
1196 * 32 pointers and then decrements %sp by 65535.)
1198 if (unlikely(address
+ 65536 + 32 * sizeof(unsigned long) < regs
->sp
)) {
1199 bad_area(regs
, error_code
, address
);
1203 if (unlikely(expand_stack(vma
, address
))) {
1204 bad_area(regs
, error_code
, address
);
1209 * Ok, we have a good vm_area for this memory access, so
1210 * we can handle it..
1213 if (unlikely(access_error(error_code
, vma
))) {
1214 bad_area_access_error(regs
, error_code
, address
);
1219 * If for any reason at all we couldn't handle the fault,
1220 * make sure we exit gracefully rather than endlessly redo
1221 * the fault. Since we never set FAULT_FLAG_RETRY_NOWAIT, if
1222 * we get VM_FAULT_RETRY back, the mmap_sem has been unlocked.
1224 fault
= handle_mm_fault(mm
, vma
, address
, flags
);
1227 * If we need to retry but a fatal signal is pending, handle the
1228 * signal first. We do not need to release the mmap_sem because it
1229 * would already be released in __lock_page_or_retry in mm/filemap.c.
1231 if (unlikely((fault
& VM_FAULT_RETRY
) && fatal_signal_pending(current
)))
1234 if (unlikely(fault
& VM_FAULT_ERROR
)) {
1235 mm_fault_error(regs
, error_code
, address
, fault
);
1240 * Major/minor page fault accounting is only done on the
1241 * initial attempt. If we go through a retry, it is extremely
1242 * likely that the page will be found in page cache at that point.
1244 if (flags
& FAULT_FLAG_ALLOW_RETRY
) {
1245 if (fault
& VM_FAULT_MAJOR
) {
1247 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ
, 1,
1251 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN
, 1,
1254 if (fault
& VM_FAULT_RETRY
) {
1255 /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
1257 flags
&= ~FAULT_FLAG_ALLOW_RETRY
;
1258 flags
|= FAULT_FLAG_TRIED
;
1263 check_v8086_mode(regs
, address
, tsk
);
1265 up_read(&mm
->mmap_sem
);
1267 NOKPROBE_SYMBOL(__do_page_fault
);
1269 dotraplinkage
void notrace
1270 do_page_fault(struct pt_regs
*regs
, unsigned long error_code
)
1272 unsigned long address
= read_cr2(); /* Get the faulting address */
1273 enum ctx_state prev_state
;
1276 * We must have this function tagged with __kprobes, notrace and call
1277 * read_cr2() before calling anything else. To avoid calling any kind
1278 * of tracing machinery before we've observed the CR2 value.
1280 * exception_{enter,exit}() contain all sorts of tracepoints.
1283 prev_state
= exception_enter();
1284 __do_page_fault(regs
, error_code
, address
);
1285 exception_exit(prev_state
);
1287 NOKPROBE_SYMBOL(do_page_fault
);
1289 #ifdef CONFIG_TRACING
1290 static nokprobe_inline
void
1291 trace_page_fault_entries(unsigned long address
, struct pt_regs
*regs
,
1292 unsigned long error_code
)
1294 if (user_mode(regs
))
1295 trace_page_fault_user(address
, regs
, error_code
);
1297 trace_page_fault_kernel(address
, regs
, error_code
);
1300 dotraplinkage
void notrace
1301 trace_do_page_fault(struct pt_regs
*regs
, unsigned long error_code
)
1304 * The exception_enter and tracepoint processing could
1305 * trigger another page faults (user space callchain
1306 * reading) and destroy the original cr2 value, so read
1307 * the faulting address now.
1309 unsigned long address
= read_cr2();
1310 enum ctx_state prev_state
;
1312 prev_state
= exception_enter();
1313 trace_page_fault_entries(address
, regs
, error_code
);
1314 __do_page_fault(regs
, error_code
, address
);
1315 exception_exit(prev_state
);
1317 NOKPROBE_SYMBOL(trace_do_page_fault
);
1318 #endif /* CONFIG_TRACING */