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(), ... */
17 #include <asm/traps.h> /* dotraplinkage, ... */
18 #include <asm/pgalloc.h> /* pgd_*(), ... */
19 #include <asm/kmemcheck.h> /* kmemcheck_*(), ... */
20 #include <asm/fixmap.h> /* VSYSCALL_ADDR */
21 #include <asm/vsyscall.h> /* emulate_vsyscall */
23 #define CREATE_TRACE_POINTS
24 #include <asm/trace/exceptions.h>
27 * Page fault error code bits:
29 * bit 0 == 0: no page found 1: protection fault
30 * bit 1 == 0: read access 1: write access
31 * bit 2 == 0: kernel-mode access 1: user-mode access
32 * bit 3 == 1: use of reserved bit detected
33 * bit 4 == 1: fault was an instruction fetch
35 enum x86_pf_error_code
{
45 * Returns 0 if mmiotrace is disabled, or if the fault is not
46 * handled by mmiotrace:
48 static nokprobe_inline
int
49 kmmio_fault(struct pt_regs
*regs
, unsigned long addr
)
51 if (unlikely(is_kmmio_active()))
52 if (kmmio_handler(regs
, addr
) == 1)
57 static nokprobe_inline
int kprobes_fault(struct pt_regs
*regs
)
61 /* kprobe_running() needs smp_processor_id() */
62 if (kprobes_built_in() && !user_mode_vm(regs
)) {
64 if (kprobe_running() && kprobe_fault_handler(regs
, 14))
77 * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
78 * Check that here and ignore it.
82 * Sometimes the CPU reports invalid exceptions on prefetch.
83 * Check that here and ignore it.
85 * Opcode checker based on code by Richard Brunner.
88 check_prefetch_opcode(struct pt_regs
*regs
, unsigned char *instr
,
89 unsigned char opcode
, int *prefetch
)
91 unsigned char instr_hi
= opcode
& 0xf0;
92 unsigned char instr_lo
= opcode
& 0x0f;
98 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes.
99 * In X86_64 long mode, the CPU will signal invalid
100 * opcode if some of these prefixes are present so
101 * X86_64 will never get here anyway
103 return ((instr_lo
& 7) == 0x6);
107 * In AMD64 long mode 0x40..0x4F are valid REX prefixes
108 * Need to figure out under what instruction mode the
109 * instruction was issued. Could check the LDT for lm,
110 * but for now it's good enough to assume that long
111 * mode only uses well known segments or kernel.
113 return (!user_mode(regs
) || user_64bit_mode(regs
));
116 /* 0x64 thru 0x67 are valid prefixes in all modes. */
117 return (instr_lo
& 0xC) == 0x4;
119 /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */
120 return !instr_lo
|| (instr_lo
>>1) == 1;
122 /* Prefetch instruction is 0x0F0D or 0x0F18 */
123 if (probe_kernel_address(instr
, opcode
))
126 *prefetch
= (instr_lo
== 0xF) &&
127 (opcode
== 0x0D || opcode
== 0x18);
135 is_prefetch(struct pt_regs
*regs
, unsigned long error_code
, unsigned long addr
)
137 unsigned char *max_instr
;
138 unsigned char *instr
;
142 * If it was a exec (instruction fetch) fault on NX page, then
143 * do not ignore the fault:
145 if (error_code
& PF_INSTR
)
148 instr
= (void *)convert_ip_to_linear(current
, regs
);
149 max_instr
= instr
+ 15;
151 if (user_mode(regs
) && instr
>= (unsigned char *)TASK_SIZE
)
154 while (instr
< max_instr
) {
155 unsigned char opcode
;
157 if (probe_kernel_address(instr
, opcode
))
162 if (!check_prefetch_opcode(regs
, instr
, opcode
, &prefetch
))
169 force_sig_info_fault(int si_signo
, int si_code
, unsigned long address
,
170 struct task_struct
*tsk
, int fault
)
175 info
.si_signo
= si_signo
;
177 info
.si_code
= si_code
;
178 info
.si_addr
= (void __user
*)address
;
179 if (fault
& VM_FAULT_HWPOISON_LARGE
)
180 lsb
= hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault
));
181 if (fault
& VM_FAULT_HWPOISON
)
183 info
.si_addr_lsb
= lsb
;
185 force_sig_info(si_signo
, &info
, tsk
);
188 DEFINE_SPINLOCK(pgd_lock
);
192 static inline pmd_t
*vmalloc_sync_one(pgd_t
*pgd
, unsigned long address
)
194 unsigned index
= pgd_index(address
);
200 pgd_k
= init_mm
.pgd
+ index
;
202 if (!pgd_present(*pgd_k
))
206 * set_pgd(pgd, *pgd_k); here would be useless on PAE
207 * and redundant with the set_pmd() on non-PAE. As would
210 pud
= pud_offset(pgd
, address
);
211 pud_k
= pud_offset(pgd_k
, address
);
212 if (!pud_present(*pud_k
))
215 pmd
= pmd_offset(pud
, address
);
216 pmd_k
= pmd_offset(pud_k
, address
);
217 if (!pmd_present(*pmd_k
))
220 if (!pmd_present(*pmd
))
221 set_pmd(pmd
, *pmd_k
);
223 BUG_ON(pmd_page(*pmd
) != pmd_page(*pmd_k
));
228 void vmalloc_sync_all(void)
230 unsigned long address
;
232 if (SHARED_KERNEL_PMD
)
235 for (address
= VMALLOC_START
& PMD_MASK
;
236 address
>= TASK_SIZE
&& address
< FIXADDR_TOP
;
237 address
+= PMD_SIZE
) {
240 spin_lock(&pgd_lock
);
241 list_for_each_entry(page
, &pgd_list
, lru
) {
242 spinlock_t
*pgt_lock
;
245 /* the pgt_lock only for Xen */
246 pgt_lock
= &pgd_page_get_mm(page
)->page_table_lock
;
249 ret
= vmalloc_sync_one(page_address(page
), address
);
250 spin_unlock(pgt_lock
);
255 spin_unlock(&pgd_lock
);
262 * Handle a fault on the vmalloc or module mapping area
264 static noinline
int vmalloc_fault(unsigned long address
)
266 unsigned long pgd_paddr
;
270 /* Make sure we are in vmalloc area: */
271 if (!(address
>= VMALLOC_START
&& address
< VMALLOC_END
))
274 WARN_ON_ONCE(in_nmi());
277 * Synchronize this task's top level page-table
278 * with the 'reference' page table.
280 * Do _not_ use "current" here. We might be inside
281 * an interrupt in the middle of a task switch..
283 pgd_paddr
= read_cr3();
284 pmd_k
= vmalloc_sync_one(__va(pgd_paddr
), address
);
288 pte_k
= pte_offset_kernel(pmd_k
, address
);
289 if (!pte_present(*pte_k
))
294 NOKPROBE_SYMBOL(vmalloc_fault
);
297 * Did it hit the DOS screen memory VA from vm86 mode?
300 check_v8086_mode(struct pt_regs
*regs
, unsigned long address
,
301 struct task_struct
*tsk
)
305 if (!v8086_mode(regs
))
308 bit
= (address
- 0xA0000) >> PAGE_SHIFT
;
310 tsk
->thread
.screen_bitmap
|= 1 << bit
;
313 static bool low_pfn(unsigned long pfn
)
315 return pfn
< max_low_pfn
;
318 static void dump_pagetable(unsigned long address
)
320 pgd_t
*base
= __va(read_cr3());
321 pgd_t
*pgd
= &base
[pgd_index(address
)];
325 #ifdef CONFIG_X86_PAE
326 printk("*pdpt = %016Lx ", pgd_val(*pgd
));
327 if (!low_pfn(pgd_val(*pgd
) >> PAGE_SHIFT
) || !pgd_present(*pgd
))
330 pmd
= pmd_offset(pud_offset(pgd
, address
), address
);
331 printk(KERN_CONT
"*pde = %0*Lx ", sizeof(*pmd
) * 2, (u64
)pmd_val(*pmd
));
334 * We must not directly access the pte in the highpte
335 * case if the page table is located in highmem.
336 * And let's rather not kmap-atomic the pte, just in case
337 * it's allocated already:
339 if (!low_pfn(pmd_pfn(*pmd
)) || !pmd_present(*pmd
) || pmd_large(*pmd
))
342 pte
= pte_offset_kernel(pmd
, address
);
343 printk("*pte = %0*Lx ", sizeof(*pte
) * 2, (u64
)pte_val(*pte
));
348 #else /* CONFIG_X86_64: */
350 void vmalloc_sync_all(void)
352 sync_global_pgds(VMALLOC_START
& PGDIR_MASK
, VMALLOC_END
, 0);
358 * Handle a fault on the vmalloc area
360 * This assumes no large pages in there.
362 static noinline
int vmalloc_fault(unsigned long address
)
364 pgd_t
*pgd
, *pgd_ref
;
365 pud_t
*pud
, *pud_ref
;
366 pmd_t
*pmd
, *pmd_ref
;
367 pte_t
*pte
, *pte_ref
;
369 /* Make sure we are in vmalloc area: */
370 if (!(address
>= VMALLOC_START
&& address
< VMALLOC_END
))
373 WARN_ON_ONCE(in_nmi());
376 * Copy kernel mappings over when needed. This can also
377 * happen within a race in page table update. In the later
380 pgd
= pgd_offset(current
->active_mm
, address
);
381 pgd_ref
= pgd_offset_k(address
);
382 if (pgd_none(*pgd_ref
))
385 if (pgd_none(*pgd
)) {
386 set_pgd(pgd
, *pgd_ref
);
387 arch_flush_lazy_mmu_mode();
389 BUG_ON(pgd_page_vaddr(*pgd
) != pgd_page_vaddr(*pgd_ref
));
393 * Below here mismatches are bugs because these lower tables
397 pud
= pud_offset(pgd
, address
);
398 pud_ref
= pud_offset(pgd_ref
, address
);
399 if (pud_none(*pud_ref
))
402 if (pud_none(*pud
) || pud_page_vaddr(*pud
) != pud_page_vaddr(*pud_ref
))
405 pmd
= pmd_offset(pud
, address
);
406 pmd_ref
= pmd_offset(pud_ref
, address
);
407 if (pmd_none(*pmd_ref
))
410 if (pmd_none(*pmd
) || pmd_page(*pmd
) != pmd_page(*pmd_ref
))
413 pte_ref
= pte_offset_kernel(pmd_ref
, address
);
414 if (!pte_present(*pte_ref
))
417 pte
= pte_offset_kernel(pmd
, address
);
420 * Don't use pte_page here, because the mappings can point
421 * outside mem_map, and the NUMA hash lookup cannot handle
424 if (!pte_present(*pte
) || pte_pfn(*pte
) != pte_pfn(*pte_ref
))
429 NOKPROBE_SYMBOL(vmalloc_fault
);
431 #ifdef CONFIG_CPU_SUP_AMD
432 static const char errata93_warning
[] =
434 "******* Your BIOS seems to not contain a fix for K8 errata #93\n"
435 "******* Working around it, but it may cause SEGVs or burn power.\n"
436 "******* Please consider a BIOS update.\n"
437 "******* Disabling USB legacy in the BIOS may also help.\n";
441 * No vm86 mode in 64-bit mode:
444 check_v8086_mode(struct pt_regs
*regs
, unsigned long address
,
445 struct task_struct
*tsk
)
449 static int bad_address(void *p
)
453 return probe_kernel_address((unsigned long *)p
, dummy
);
456 static void dump_pagetable(unsigned long address
)
458 pgd_t
*base
= __va(read_cr3() & PHYSICAL_PAGE_MASK
);
459 pgd_t
*pgd
= base
+ pgd_index(address
);
464 if (bad_address(pgd
))
467 printk("PGD %lx ", pgd_val(*pgd
));
469 if (!pgd_present(*pgd
))
472 pud
= pud_offset(pgd
, address
);
473 if (bad_address(pud
))
476 printk("PUD %lx ", pud_val(*pud
));
477 if (!pud_present(*pud
) || pud_large(*pud
))
480 pmd
= pmd_offset(pud
, address
);
481 if (bad_address(pmd
))
484 printk("PMD %lx ", pmd_val(*pmd
));
485 if (!pmd_present(*pmd
) || pmd_large(*pmd
))
488 pte
= pte_offset_kernel(pmd
, address
);
489 if (bad_address(pte
))
492 printk("PTE %lx", pte_val(*pte
));
500 #endif /* CONFIG_X86_64 */
503 * Workaround for K8 erratum #93 & buggy BIOS.
505 * BIOS SMM functions are required to use a specific workaround
506 * to avoid corruption of the 64bit RIP register on C stepping K8.
508 * A lot of BIOS that didn't get tested properly miss this.
510 * The OS sees this as a page fault with the upper 32bits of RIP cleared.
511 * Try to work around it here.
513 * Note we only handle faults in kernel here.
514 * Does nothing on 32-bit.
516 static int is_errata93(struct pt_regs
*regs
, unsigned long address
)
518 #if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD)
519 if (boot_cpu_data
.x86_vendor
!= X86_VENDOR_AMD
520 || boot_cpu_data
.x86
!= 0xf)
523 if (address
!= regs
->ip
)
526 if ((address
>> 32) != 0)
529 address
|= 0xffffffffUL
<< 32;
530 if ((address
>= (u64
)_stext
&& address
<= (u64
)_etext
) ||
531 (address
>= MODULES_VADDR
&& address
<= MODULES_END
)) {
532 printk_once(errata93_warning
);
541 * Work around K8 erratum #100 K8 in compat mode occasionally jumps
542 * to illegal addresses >4GB.
544 * We catch this in the page fault handler because these addresses
545 * are not reachable. Just detect this case and return. Any code
546 * segment in LDT is compatibility mode.
548 static int is_errata100(struct pt_regs
*regs
, unsigned long address
)
551 if ((regs
->cs
== __USER32_CS
|| (regs
->cs
& (1<<2))) && (address
>> 32))
557 static int is_f00f_bug(struct pt_regs
*regs
, unsigned long address
)
559 #ifdef CONFIG_X86_F00F_BUG
563 * Pentium F0 0F C7 C8 bug workaround:
565 if (boot_cpu_has_bug(X86_BUG_F00F
)) {
566 nr
= (address
- idt_descr
.address
) >> 3;
569 do_invalid_op(regs
, 0);
577 static const char nx_warning
[] = KERN_CRIT
578 "kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n";
579 static const char smep_warning
[] = KERN_CRIT
580 "unable to execute userspace code (SMEP?) (uid: %d)\n";
583 show_fault_oops(struct pt_regs
*regs
, unsigned long error_code
,
584 unsigned long address
)
586 if (!oops_may_print())
589 if (error_code
& PF_INSTR
) {
594 pgd
= __va(read_cr3() & PHYSICAL_PAGE_MASK
);
595 pgd
+= pgd_index(address
);
597 pte
= lookup_address_in_pgd(pgd
, address
, &level
);
599 if (pte
&& pte_present(*pte
) && !pte_exec(*pte
))
600 printk(nx_warning
, from_kuid(&init_user_ns
, current_uid()));
601 if (pte
&& pte_present(*pte
) && pte_exec(*pte
) &&
602 (pgd_flags(*pgd
) & _PAGE_USER
) &&
603 (__read_cr4() & X86_CR4_SMEP
))
604 printk(smep_warning
, from_kuid(&init_user_ns
, current_uid()));
607 printk(KERN_ALERT
"BUG: unable to handle kernel ");
608 if (address
< PAGE_SIZE
)
609 printk(KERN_CONT
"NULL pointer dereference");
611 printk(KERN_CONT
"paging request");
613 printk(KERN_CONT
" at %p\n", (void *) address
);
614 printk(KERN_ALERT
"IP:");
615 printk_address(regs
->ip
);
617 dump_pagetable(address
);
621 pgtable_bad(struct pt_regs
*regs
, unsigned long error_code
,
622 unsigned long address
)
624 struct task_struct
*tsk
;
628 flags
= oops_begin();
632 printk(KERN_ALERT
"%s: Corrupted page table at address %lx\n",
634 dump_pagetable(address
);
636 tsk
->thread
.cr2
= address
;
637 tsk
->thread
.trap_nr
= X86_TRAP_PF
;
638 tsk
->thread
.error_code
= error_code
;
640 if (__die("Bad pagetable", regs
, error_code
))
643 oops_end(flags
, regs
, sig
);
647 no_context(struct pt_regs
*regs
, unsigned long error_code
,
648 unsigned long address
, int signal
, int si_code
)
650 struct task_struct
*tsk
= current
;
654 /* Are we prepared to handle this kernel fault? */
655 if (fixup_exception(regs
)) {
657 * Any interrupt that takes a fault gets the fixup. This makes
658 * the below recursive fault logic only apply to a faults from
665 * Per the above we're !in_interrupt(), aka. task context.
667 * In this case we need to make sure we're not recursively
668 * faulting through the emulate_vsyscall() logic.
670 if (current_thread_info()->sig_on_uaccess_error
&& signal
) {
671 tsk
->thread
.trap_nr
= X86_TRAP_PF
;
672 tsk
->thread
.error_code
= error_code
| PF_USER
;
673 tsk
->thread
.cr2
= address
;
675 /* XXX: hwpoison faults will set the wrong code. */
676 force_sig_info_fault(signal
, si_code
, address
, tsk
, 0);
680 * Barring that, we can do the fixup and be happy.
688 * Valid to do another page fault here, because if this fault
689 * had been triggered by is_prefetch fixup_exception would have
694 * Hall of shame of CPU/BIOS bugs.
696 if (is_prefetch(regs
, error_code
, address
))
699 if (is_errata93(regs
, address
))
703 * Oops. The kernel tried to access some bad page. We'll have to
704 * terminate things with extreme prejudice:
706 flags
= oops_begin();
708 show_fault_oops(regs
, error_code
, address
);
710 if (task_stack_end_corrupted(tsk
))
711 printk(KERN_EMERG
"Thread overran stack, or stack corrupted\n");
713 tsk
->thread
.cr2
= address
;
714 tsk
->thread
.trap_nr
= X86_TRAP_PF
;
715 tsk
->thread
.error_code
= error_code
;
718 if (__die("Oops", regs
, error_code
))
721 /* Executive summary in case the body of the oops scrolled away */
722 printk(KERN_DEFAULT
"CR2: %016lx\n", address
);
724 oops_end(flags
, regs
, sig
);
728 * Print out info about fatal segfaults, if the show_unhandled_signals
732 show_signal_msg(struct pt_regs
*regs
, unsigned long error_code
,
733 unsigned long address
, struct task_struct
*tsk
)
735 if (!unhandled_signal(tsk
, SIGSEGV
))
738 if (!printk_ratelimit())
741 printk("%s%s[%d]: segfault at %lx ip %p sp %p error %lx",
742 task_pid_nr(tsk
) > 1 ? KERN_INFO
: KERN_EMERG
,
743 tsk
->comm
, task_pid_nr(tsk
), address
,
744 (void *)regs
->ip
, (void *)regs
->sp
, error_code
);
746 print_vma_addr(KERN_CONT
" in ", regs
->ip
);
748 printk(KERN_CONT
"\n");
752 __bad_area_nosemaphore(struct pt_regs
*regs
, unsigned long error_code
,
753 unsigned long address
, int si_code
)
755 struct task_struct
*tsk
= current
;
757 /* User mode accesses just cause a SIGSEGV */
758 if (error_code
& PF_USER
) {
760 * It's possible to have interrupts off here:
765 * Valid to do another page fault here because this one came
768 if (is_prefetch(regs
, error_code
, address
))
771 if (is_errata100(regs
, address
))
776 * Instruction fetch faults in the vsyscall page might need
779 if (unlikely((error_code
& PF_INSTR
) &&
780 ((address
& ~0xfff) == VSYSCALL_ADDR
))) {
781 if (emulate_vsyscall(regs
, address
))
785 /* Kernel addresses are always protection faults: */
786 if (address
>= TASK_SIZE
)
787 error_code
|= PF_PROT
;
789 if (likely(show_unhandled_signals
))
790 show_signal_msg(regs
, error_code
, address
, tsk
);
792 tsk
->thread
.cr2
= address
;
793 tsk
->thread
.error_code
= error_code
;
794 tsk
->thread
.trap_nr
= X86_TRAP_PF
;
796 force_sig_info_fault(SIGSEGV
, si_code
, address
, tsk
, 0);
801 if (is_f00f_bug(regs
, address
))
804 no_context(regs
, error_code
, address
, SIGSEGV
, si_code
);
808 bad_area_nosemaphore(struct pt_regs
*regs
, unsigned long error_code
,
809 unsigned long address
)
811 __bad_area_nosemaphore(regs
, error_code
, address
, SEGV_MAPERR
);
815 __bad_area(struct pt_regs
*regs
, unsigned long error_code
,
816 unsigned long address
, int si_code
)
818 struct mm_struct
*mm
= current
->mm
;
821 * Something tried to access memory that isn't in our memory map..
822 * Fix it, but check if it's kernel or user first..
824 up_read(&mm
->mmap_sem
);
826 __bad_area_nosemaphore(regs
, error_code
, address
, si_code
);
830 bad_area(struct pt_regs
*regs
, unsigned long error_code
, unsigned long address
)
832 __bad_area(regs
, error_code
, address
, SEGV_MAPERR
);
836 bad_area_access_error(struct pt_regs
*regs
, unsigned long error_code
,
837 unsigned long address
)
839 __bad_area(regs
, error_code
, address
, SEGV_ACCERR
);
843 do_sigbus(struct pt_regs
*regs
, unsigned long error_code
, unsigned long address
,
846 struct task_struct
*tsk
= current
;
847 int code
= BUS_ADRERR
;
849 /* Kernel mode? Handle exceptions or die: */
850 if (!(error_code
& PF_USER
)) {
851 no_context(regs
, error_code
, address
, SIGBUS
, BUS_ADRERR
);
855 /* User-space => ok to do another page fault: */
856 if (is_prefetch(regs
, error_code
, address
))
859 tsk
->thread
.cr2
= address
;
860 tsk
->thread
.error_code
= error_code
;
861 tsk
->thread
.trap_nr
= X86_TRAP_PF
;
863 #ifdef CONFIG_MEMORY_FAILURE
864 if (fault
& (VM_FAULT_HWPOISON
|VM_FAULT_HWPOISON_LARGE
)) {
866 "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
867 tsk
->comm
, tsk
->pid
, address
);
868 code
= BUS_MCEERR_AR
;
871 force_sig_info_fault(SIGBUS
, code
, address
, tsk
, fault
);
875 mm_fault_error(struct pt_regs
*regs
, unsigned long error_code
,
876 unsigned long address
, unsigned int fault
)
878 if (fatal_signal_pending(current
) && !(error_code
& PF_USER
)) {
879 no_context(regs
, error_code
, address
, 0, 0);
883 if (fault
& VM_FAULT_OOM
) {
884 /* Kernel mode? Handle exceptions or die: */
885 if (!(error_code
& PF_USER
)) {
886 no_context(regs
, error_code
, address
,
887 SIGSEGV
, SEGV_MAPERR
);
892 * We ran out of memory, call the OOM killer, and return the
893 * userspace (which will retry the fault, or kill us if we got
896 pagefault_out_of_memory();
898 if (fault
& (VM_FAULT_SIGBUS
|VM_FAULT_HWPOISON
|
899 VM_FAULT_HWPOISON_LARGE
))
900 do_sigbus(regs
, error_code
, address
, fault
);
901 else if (fault
& VM_FAULT_SIGSEGV
)
902 bad_area_nosemaphore(regs
, error_code
, address
);
908 static int spurious_fault_check(unsigned long error_code
, pte_t
*pte
)
910 if ((error_code
& PF_WRITE
) && !pte_write(*pte
))
913 if ((error_code
& PF_INSTR
) && !pte_exec(*pte
))
920 * Handle a spurious fault caused by a stale TLB entry.
922 * This allows us to lazily refresh the TLB when increasing the
923 * permissions of a kernel page (RO -> RW or NX -> X). Doing it
924 * eagerly is very expensive since that implies doing a full
925 * cross-processor TLB flush, even if no stale TLB entries exist
926 * on other processors.
928 * Spurious faults may only occur if the TLB contains an entry with
929 * fewer permission than the page table entry. Non-present (P = 0)
930 * and reserved bit (R = 1) faults are never spurious.
932 * There are no security implications to leaving a stale TLB when
933 * increasing the permissions on a page.
935 * Returns non-zero if a spurious fault was handled, zero otherwise.
937 * See Intel Developer's Manual Vol 3 Section 4.10.4.3, bullet 3
938 * (Optional Invalidation).
941 spurious_fault(unsigned long error_code
, unsigned long address
)
950 * Only writes to RO or instruction fetches from NX may cause
953 * These could be from user or supervisor accesses but the TLB
954 * is only lazily flushed after a kernel mapping protection
955 * change, so user accesses are not expected to cause spurious
958 if (error_code
!= (PF_WRITE
| PF_PROT
)
959 && error_code
!= (PF_INSTR
| PF_PROT
))
962 pgd
= init_mm
.pgd
+ pgd_index(address
);
963 if (!pgd_present(*pgd
))
966 pud
= pud_offset(pgd
, address
);
967 if (!pud_present(*pud
))
971 return spurious_fault_check(error_code
, (pte_t
*) pud
);
973 pmd
= pmd_offset(pud
, address
);
974 if (!pmd_present(*pmd
))
978 return spurious_fault_check(error_code
, (pte_t
*) pmd
);
980 pte
= pte_offset_kernel(pmd
, address
);
981 if (!pte_present(*pte
))
984 ret
= spurious_fault_check(error_code
, pte
);
989 * Make sure we have permissions in PMD.
990 * If not, then there's a bug in the page tables:
992 ret
= spurious_fault_check(error_code
, (pte_t
*) pmd
);
993 WARN_ONCE(!ret
, "PMD has incorrect permission bits\n");
997 NOKPROBE_SYMBOL(spurious_fault
);
999 int show_unhandled_signals
= 1;
1002 access_error(unsigned long error_code
, struct vm_area_struct
*vma
)
1004 if (error_code
& PF_WRITE
) {
1005 /* write, present and write, not present: */
1006 if (unlikely(!(vma
->vm_flags
& VM_WRITE
)))
1011 /* read, present: */
1012 if (unlikely(error_code
& PF_PROT
))
1015 /* read, not present: */
1016 if (unlikely(!(vma
->vm_flags
& (VM_READ
| VM_EXEC
| VM_WRITE
))))
1022 static int fault_in_kernel_space(unsigned long address
)
1024 return address
>= TASK_SIZE_MAX
;
1027 static inline bool smap_violation(int error_code
, struct pt_regs
*regs
)
1029 if (!IS_ENABLED(CONFIG_X86_SMAP
))
1032 if (!static_cpu_has(X86_FEATURE_SMAP
))
1035 if (error_code
& PF_USER
)
1038 if (!user_mode_vm(regs
) && (regs
->flags
& X86_EFLAGS_AC
))
1045 * This routine handles page faults. It determines the address,
1046 * and the problem, and then passes it off to one of the appropriate
1049 * This function must have noinline because both callers
1050 * {,trace_}do_page_fault() have notrace on. Having this an actual function
1051 * guarantees there's a function trace entry.
1053 static noinline
void
1054 __do_page_fault(struct pt_regs
*regs
, unsigned long error_code
,
1055 unsigned long address
)
1057 struct vm_area_struct
*vma
;
1058 struct task_struct
*tsk
;
1059 struct mm_struct
*mm
;
1060 int fault
, major
= 0;
1061 unsigned int flags
= FAULT_FLAG_ALLOW_RETRY
| FAULT_FLAG_KILLABLE
;
1067 * Detect and handle instructions that would cause a page fault for
1068 * both a tracked kernel page and a userspace page.
1070 if (kmemcheck_active(regs
))
1071 kmemcheck_hide(regs
);
1072 prefetchw(&mm
->mmap_sem
);
1074 if (unlikely(kmmio_fault(regs
, address
)))
1078 * We fault-in kernel-space virtual memory on-demand. The
1079 * 'reference' page table is init_mm.pgd.
1081 * NOTE! We MUST NOT take any locks for this case. We may
1082 * be in an interrupt or a critical region, and should
1083 * only copy the information from the master page table,
1086 * This verifies that the fault happens in kernel space
1087 * (error_code & 4) == 0, and that the fault was not a
1088 * protection error (error_code & 9) == 0.
1090 if (unlikely(fault_in_kernel_space(address
))) {
1091 if (!(error_code
& (PF_RSVD
| PF_USER
| PF_PROT
))) {
1092 if (vmalloc_fault(address
) >= 0)
1095 if (kmemcheck_fault(regs
, address
, error_code
))
1099 /* Can handle a stale RO->RW TLB: */
1100 if (spurious_fault(error_code
, address
))
1103 /* kprobes don't want to hook the spurious faults: */
1104 if (kprobes_fault(regs
))
1107 * Don't take the mm semaphore here. If we fixup a prefetch
1108 * fault we could otherwise deadlock:
1110 bad_area_nosemaphore(regs
, error_code
, address
);
1115 /* kprobes don't want to hook the spurious faults: */
1116 if (unlikely(kprobes_fault(regs
)))
1119 if (unlikely(error_code
& PF_RSVD
))
1120 pgtable_bad(regs
, error_code
, address
);
1122 if (unlikely(smap_violation(error_code
, regs
))) {
1123 bad_area_nosemaphore(regs
, error_code
, address
);
1128 * If we're in an interrupt, have no user context or are running
1129 * in an atomic region then we must not take the fault:
1131 if (unlikely(in_atomic() || !mm
)) {
1132 bad_area_nosemaphore(regs
, error_code
, address
);
1137 * It's safe to allow irq's after cr2 has been saved and the
1138 * vmalloc fault has been handled.
1140 * User-mode registers count as a user access even for any
1141 * potential system fault or CPU buglet:
1143 if (user_mode_vm(regs
)) {
1145 error_code
|= PF_USER
;
1146 flags
|= FAULT_FLAG_USER
;
1148 if (regs
->flags
& X86_EFLAGS_IF
)
1152 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS
, 1, regs
, address
);
1154 if (error_code
& PF_WRITE
)
1155 flags
|= FAULT_FLAG_WRITE
;
1158 * When running in the kernel we expect faults to occur only to
1159 * addresses in user space. All other faults represent errors in
1160 * the kernel and should generate an OOPS. Unfortunately, in the
1161 * case of an erroneous fault occurring in a code path which already
1162 * holds mmap_sem we will deadlock attempting to validate the fault
1163 * against the address space. Luckily the kernel only validly
1164 * references user space from well defined areas of code, which are
1165 * listed in the exceptions table.
1167 * As the vast majority of faults will be valid we will only perform
1168 * the source reference check when there is a possibility of a
1169 * deadlock. Attempt to lock the address space, if we cannot we then
1170 * validate the source. If this is invalid we can skip the address
1171 * space check, thus avoiding the deadlock:
1173 if (unlikely(!down_read_trylock(&mm
->mmap_sem
))) {
1174 if ((error_code
& PF_USER
) == 0 &&
1175 !search_exception_tables(regs
->ip
)) {
1176 bad_area_nosemaphore(regs
, error_code
, address
);
1180 down_read(&mm
->mmap_sem
);
1183 * The above down_read_trylock() might have succeeded in
1184 * which case we'll have missed the might_sleep() from
1190 vma
= find_vma(mm
, address
);
1191 if (unlikely(!vma
)) {
1192 bad_area(regs
, error_code
, address
);
1195 if (likely(vma
->vm_start
<= address
))
1197 if (unlikely(!(vma
->vm_flags
& VM_GROWSDOWN
))) {
1198 bad_area(regs
, error_code
, address
);
1201 if (error_code
& PF_USER
) {
1203 * Accessing the stack below %sp is always a bug.
1204 * The large cushion allows instructions like enter
1205 * and pusha to work. ("enter $65535, $31" pushes
1206 * 32 pointers and then decrements %sp by 65535.)
1208 if (unlikely(address
+ 65536 + 32 * sizeof(unsigned long) < regs
->sp
)) {
1209 bad_area(regs
, error_code
, address
);
1213 if (unlikely(expand_stack(vma
, address
))) {
1214 bad_area(regs
, error_code
, address
);
1219 * Ok, we have a good vm_area for this memory access, so
1220 * we can handle it..
1223 if (unlikely(access_error(error_code
, vma
))) {
1224 bad_area_access_error(regs
, error_code
, address
);
1229 * If for any reason at all we couldn't handle the fault,
1230 * make sure we exit gracefully rather than endlessly redo
1231 * the fault. Since we never set FAULT_FLAG_RETRY_NOWAIT, if
1232 * we get VM_FAULT_RETRY back, the mmap_sem has been unlocked.
1234 fault
= handle_mm_fault(mm
, vma
, address
, flags
);
1235 major
|= fault
& VM_FAULT_MAJOR
;
1238 * If we need to retry the mmap_sem has already been released,
1239 * and if there is a fatal signal pending there is no guarantee
1240 * that we made any progress. Handle this case first.
1242 if (unlikely(fault
& VM_FAULT_RETRY
)) {
1243 /* Retry at most once */
1244 if (flags
& FAULT_FLAG_ALLOW_RETRY
) {
1245 flags
&= ~FAULT_FLAG_ALLOW_RETRY
;
1246 flags
|= FAULT_FLAG_TRIED
;
1247 if (!fatal_signal_pending(tsk
))
1251 /* User mode? Just return to handle the fatal exception */
1252 if (flags
& FAULT_FLAG_USER
)
1255 /* Not returning to user mode? Handle exceptions or die: */
1256 no_context(regs
, error_code
, address
, SIGBUS
, BUS_ADRERR
);
1260 up_read(&mm
->mmap_sem
);
1261 if (unlikely(fault
& VM_FAULT_ERROR
)) {
1262 mm_fault_error(regs
, error_code
, address
, fault
);
1267 * Major/minor page fault accounting. If any of the events
1268 * returned VM_FAULT_MAJOR, we account it as a major fault.
1272 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ
, 1, regs
, address
);
1275 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN
, 1, regs
, address
);
1278 check_v8086_mode(regs
, address
, tsk
);
1280 NOKPROBE_SYMBOL(__do_page_fault
);
1282 dotraplinkage
void notrace
1283 do_page_fault(struct pt_regs
*regs
, unsigned long error_code
)
1285 unsigned long address
= read_cr2(); /* Get the faulting address */
1286 enum ctx_state prev_state
;
1289 * We must have this function tagged with __kprobes, notrace and call
1290 * read_cr2() before calling anything else. To avoid calling any kind
1291 * of tracing machinery before we've observed the CR2 value.
1293 * exception_{enter,exit}() contain all sorts of tracepoints.
1296 prev_state
= exception_enter();
1297 __do_page_fault(regs
, error_code
, address
);
1298 exception_exit(prev_state
);
1300 NOKPROBE_SYMBOL(do_page_fault
);
1302 #ifdef CONFIG_TRACING
1303 static nokprobe_inline
void
1304 trace_page_fault_entries(unsigned long address
, struct pt_regs
*regs
,
1305 unsigned long error_code
)
1307 if (user_mode(regs
))
1308 trace_page_fault_user(address
, regs
, error_code
);
1310 trace_page_fault_kernel(address
, regs
, error_code
);
1313 dotraplinkage
void notrace
1314 trace_do_page_fault(struct pt_regs
*regs
, unsigned long error_code
)
1317 * The exception_enter and tracepoint processing could
1318 * trigger another page faults (user space callchain
1319 * reading) and destroy the original cr2 value, so read
1320 * the faulting address now.
1322 unsigned long address
= read_cr2();
1323 enum ctx_state prev_state
;
1325 prev_state
= exception_enter();
1326 trace_page_fault_entries(address
, regs
, error_code
);
1327 __do_page_fault(regs
, error_code
, address
);
1328 exception_exit(prev_state
);
1330 NOKPROBE_SYMBOL(trace_do_page_fault
);
1331 #endif /* CONFIG_TRACING */