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/cpufeature.h> /* boot_cpu_has, ... */
19 #include <asm/traps.h> /* dotraplinkage, ... */
20 #include <asm/pgalloc.h> /* pgd_*(), ... */
21 #include <asm/kmemcheck.h> /* kmemcheck_*(), ... */
22 #include <asm/fixmap.h> /* VSYSCALL_ADDR */
23 #include <asm/vsyscall.h> /* emulate_vsyscall */
24 #include <asm/vm86.h> /* struct vm86 */
25 #include <asm/mmu_context.h> /* vma_pkey() */
27 #define CREATE_TRACE_POINTS
28 #include <asm/trace/exceptions.h>
31 * Page fault error code bits:
33 * bit 0 == 0: no page found 1: protection fault
34 * bit 1 == 0: read access 1: write access
35 * bit 2 == 0: kernel-mode access 1: user-mode access
36 * bit 3 == 1: use of reserved bit detected
37 * bit 4 == 1: fault was an instruction fetch
38 * bit 5 == 1: protection keys block access
40 enum x86_pf_error_code
{
51 * Returns 0 if mmiotrace is disabled, or if the fault is not
52 * handled by mmiotrace:
54 static nokprobe_inline
int
55 kmmio_fault(struct pt_regs
*regs
, unsigned long addr
)
57 if (unlikely(is_kmmio_active()))
58 if (kmmio_handler(regs
, addr
) == 1)
63 static nokprobe_inline
int kprobes_fault(struct pt_regs
*regs
)
67 /* kprobe_running() needs smp_processor_id() */
68 if (kprobes_built_in() && !user_mode(regs
)) {
70 if (kprobe_running() && kprobe_fault_handler(regs
, 14))
83 * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
84 * Check that here and ignore it.
88 * Sometimes the CPU reports invalid exceptions on prefetch.
89 * Check that here and ignore it.
91 * Opcode checker based on code by Richard Brunner.
94 check_prefetch_opcode(struct pt_regs
*regs
, unsigned char *instr
,
95 unsigned char opcode
, int *prefetch
)
97 unsigned char instr_hi
= opcode
& 0xf0;
98 unsigned char instr_lo
= opcode
& 0x0f;
104 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes.
105 * In X86_64 long mode, the CPU will signal invalid
106 * opcode if some of these prefixes are present so
107 * X86_64 will never get here anyway
109 return ((instr_lo
& 7) == 0x6);
113 * In AMD64 long mode 0x40..0x4F are valid REX prefixes
114 * Need to figure out under what instruction mode the
115 * instruction was issued. Could check the LDT for lm,
116 * but for now it's good enough to assume that long
117 * mode only uses well known segments or kernel.
119 return (!user_mode(regs
) || user_64bit_mode(regs
));
122 /* 0x64 thru 0x67 are valid prefixes in all modes. */
123 return (instr_lo
& 0xC) == 0x4;
125 /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */
126 return !instr_lo
|| (instr_lo
>>1) == 1;
128 /* Prefetch instruction is 0x0F0D or 0x0F18 */
129 if (probe_kernel_address(instr
, opcode
))
132 *prefetch
= (instr_lo
== 0xF) &&
133 (opcode
== 0x0D || opcode
== 0x18);
141 is_prefetch(struct pt_regs
*regs
, unsigned long error_code
, unsigned long addr
)
143 unsigned char *max_instr
;
144 unsigned char *instr
;
148 * If it was a exec (instruction fetch) fault on NX page, then
149 * do not ignore the fault:
151 if (error_code
& PF_INSTR
)
154 instr
= (void *)convert_ip_to_linear(current
, regs
);
155 max_instr
= instr
+ 15;
157 if (user_mode(regs
) && instr
>= (unsigned char *)TASK_SIZE_MAX
)
160 while (instr
< max_instr
) {
161 unsigned char opcode
;
163 if (probe_kernel_address(instr
, opcode
))
168 if (!check_prefetch_opcode(regs
, instr
, opcode
, &prefetch
))
175 * A protection key fault means that the PKRU value did not allow
176 * access to some PTE. Userspace can figure out what PKRU was
177 * from the XSAVE state, and this function fills out a field in
178 * siginfo so userspace can discover which protection key was set
181 * If we get here, we know that the hardware signaled a PF_PK
182 * fault and that there was a VMA once we got in the fault
183 * handler. It does *not* guarantee that the VMA we find here
184 * was the one that we faulted on.
186 * 1. T1 : mprotect_key(foo, PAGE_SIZE, pkey=4);
187 * 2. T1 : set PKRU to deny access to pkey=4, touches page
189 * 4. T2: mprotect_key(foo, PAGE_SIZE, pkey=5);
190 * 5. T1 : enters fault handler, takes mmap_sem, etc...
191 * 6. T1 : reaches here, sees vma_pkey(vma)=5, when we really
192 * faulted on a pte with its pkey=4.
194 static void fill_sig_info_pkey(int si_code
, siginfo_t
*info
,
195 struct vm_area_struct
*vma
)
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
= vma_pkey(vma
);
225 force_sig_info_fault(int si_signo
, int si_code
, unsigned long address
,
226 struct task_struct
*tsk
, struct vm_area_struct
*vma
,
232 info
.si_signo
= si_signo
;
234 info
.si_code
= si_code
;
235 info
.si_addr
= (void __user
*)address
;
236 if (fault
& VM_FAULT_HWPOISON_LARGE
)
237 lsb
= hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault
));
238 if (fault
& VM_FAULT_HWPOISON
)
240 info
.si_addr_lsb
= lsb
;
242 fill_sig_info_pkey(si_code
, &info
, vma
);
244 force_sig_info(si_signo
, &info
, tsk
);
247 DEFINE_SPINLOCK(pgd_lock
);
251 static inline pmd_t
*vmalloc_sync_one(pgd_t
*pgd
, unsigned long address
)
253 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 pud
= pud_offset(pgd
, address
);
270 pud_k
= pud_offset(pgd_k
, address
);
271 if (!pud_present(*pud_k
))
274 pmd
= pmd_offset(pud
, address
);
275 pmd_k
= pmd_offset(pud_k
, address
);
276 if (!pmd_present(*pmd_k
))
279 if (!pmd_present(*pmd
))
280 set_pmd(pmd
, *pmd_k
);
282 BUG_ON(pmd_page(*pmd
) != pmd_page(*pmd_k
));
287 void vmalloc_sync_all(void)
289 unsigned long address
;
291 if (SHARED_KERNEL_PMD
)
294 for (address
= VMALLOC_START
& PMD_MASK
;
295 address
>= TASK_SIZE
&& address
< FIXADDR_TOP
;
296 address
+= PMD_SIZE
) {
299 spin_lock(&pgd_lock
);
300 list_for_each_entry(page
, &pgd_list
, lru
) {
301 spinlock_t
*pgt_lock
;
304 /* the pgt_lock only for Xen */
305 pgt_lock
= &pgd_page_get_mm(page
)->page_table_lock
;
308 ret
= vmalloc_sync_one(page_address(page
), address
);
309 spin_unlock(pgt_lock
);
314 spin_unlock(&pgd_lock
);
321 * Handle a fault on the vmalloc or module mapping area
323 static noinline
int vmalloc_fault(unsigned long address
)
325 unsigned long pgd_paddr
;
329 /* Make sure we are in vmalloc area: */
330 if (!(address
>= VMALLOC_START
&& address
< VMALLOC_END
))
333 WARN_ON_ONCE(in_nmi());
336 * Synchronize this task's top level page-table
337 * with the 'reference' page table.
339 * Do _not_ use "current" here. We might be inside
340 * an interrupt in the middle of a task switch..
342 pgd_paddr
= read_cr3();
343 pmd_k
= vmalloc_sync_one(__va(pgd_paddr
), address
);
347 pte_k
= pte_offset_kernel(pmd_k
, address
);
348 if (!pte_present(*pte_k
))
353 NOKPROBE_SYMBOL(vmalloc_fault
);
356 * Did it hit the DOS screen memory VA from vm86 mode?
359 check_v8086_mode(struct pt_regs
*regs
, unsigned long address
,
360 struct task_struct
*tsk
)
365 if (!v8086_mode(regs
) || !tsk
->thread
.vm86
)
368 bit
= (address
- 0xA0000) >> PAGE_SHIFT
;
370 tsk
->thread
.vm86
->screen_bitmap
|= 1 << bit
;
374 static bool low_pfn(unsigned long pfn
)
376 return pfn
< max_low_pfn
;
379 static void dump_pagetable(unsigned long address
)
381 pgd_t
*base
= __va(read_cr3());
382 pgd_t
*pgd
= &base
[pgd_index(address
)];
386 #ifdef CONFIG_X86_PAE
387 printk("*pdpt = %016Lx ", pgd_val(*pgd
));
388 if (!low_pfn(pgd_val(*pgd
) >> PAGE_SHIFT
) || !pgd_present(*pgd
))
391 pmd
= pmd_offset(pud_offset(pgd
, address
), address
);
392 printk(KERN_CONT
"*pde = %0*Lx ", sizeof(*pmd
) * 2, (u64
)pmd_val(*pmd
));
395 * We must not directly access the pte in the highpte
396 * case if the page table is located in highmem.
397 * And let's rather not kmap-atomic the pte, just in case
398 * it's allocated already:
400 if (!low_pfn(pmd_pfn(*pmd
)) || !pmd_present(*pmd
) || pmd_large(*pmd
))
403 pte
= pte_offset_kernel(pmd
, address
);
404 printk("*pte = %0*Lx ", sizeof(*pte
) * 2, (u64
)pte_val(*pte
));
409 #else /* CONFIG_X86_64: */
411 void vmalloc_sync_all(void)
413 sync_global_pgds(VMALLOC_START
& PGDIR_MASK
, VMALLOC_END
, 0);
419 * Handle a fault on the vmalloc area
421 * This assumes no large pages in there.
423 static noinline
int vmalloc_fault(unsigned long address
)
425 pgd_t
*pgd
, *pgd_ref
;
426 pud_t
*pud
, *pud_ref
;
427 pmd_t
*pmd
, *pmd_ref
;
428 pte_t
*pte
, *pte_ref
;
430 /* Make sure we are in vmalloc area: */
431 if (!(address
>= VMALLOC_START
&& address
< VMALLOC_END
))
434 WARN_ON_ONCE(in_nmi());
437 * Copy kernel mappings over when needed. This can also
438 * happen within a race in page table update. In the later
441 pgd
= pgd_offset(current
->active_mm
, address
);
442 pgd_ref
= pgd_offset_k(address
);
443 if (pgd_none(*pgd_ref
))
446 if (pgd_none(*pgd
)) {
447 set_pgd(pgd
, *pgd_ref
);
448 arch_flush_lazy_mmu_mode();
450 BUG_ON(pgd_page_vaddr(*pgd
) != pgd_page_vaddr(*pgd_ref
));
454 * Below here mismatches are bugs because these lower tables
458 pud
= pud_offset(pgd
, address
);
459 pud_ref
= pud_offset(pgd_ref
, address
);
460 if (pud_none(*pud_ref
))
463 if (pud_none(*pud
) || pud_page_vaddr(*pud
) != pud_page_vaddr(*pud_ref
))
466 pmd
= pmd_offset(pud
, address
);
467 pmd_ref
= pmd_offset(pud_ref
, address
);
468 if (pmd_none(*pmd_ref
))
471 if (pmd_none(*pmd
) || pmd_page(*pmd
) != pmd_page(*pmd_ref
))
474 pte_ref
= pte_offset_kernel(pmd_ref
, address
);
475 if (!pte_present(*pte_ref
))
478 pte
= pte_offset_kernel(pmd
, address
);
481 * Don't use pte_page here, because the mappings can point
482 * outside mem_map, and the NUMA hash lookup cannot handle
485 if (!pte_present(*pte
) || pte_pfn(*pte
) != pte_pfn(*pte_ref
))
490 NOKPROBE_SYMBOL(vmalloc_fault
);
492 #ifdef CONFIG_CPU_SUP_AMD
493 static const char errata93_warning
[] =
495 "******* Your BIOS seems to not contain a fix for K8 errata #93\n"
496 "******* Working around it, but it may cause SEGVs or burn power.\n"
497 "******* Please consider a BIOS update.\n"
498 "******* Disabling USB legacy in the BIOS may also help.\n";
502 * No vm86 mode in 64-bit mode:
505 check_v8086_mode(struct pt_regs
*regs
, unsigned long address
,
506 struct task_struct
*tsk
)
510 static int bad_address(void *p
)
514 return probe_kernel_address((unsigned long *)p
, dummy
);
517 static void dump_pagetable(unsigned long address
)
519 pgd_t
*base
= __va(read_cr3() & PHYSICAL_PAGE_MASK
);
520 pgd_t
*pgd
= base
+ pgd_index(address
);
525 if (bad_address(pgd
))
528 printk("PGD %lx ", pgd_val(*pgd
));
530 if (!pgd_present(*pgd
))
533 pud
= pud_offset(pgd
, address
);
534 if (bad_address(pud
))
537 printk("PUD %lx ", pud_val(*pud
));
538 if (!pud_present(*pud
) || pud_large(*pud
))
541 pmd
= pmd_offset(pud
, address
);
542 if (bad_address(pmd
))
545 printk("PMD %lx ", pmd_val(*pmd
));
546 if (!pmd_present(*pmd
) || pmd_large(*pmd
))
549 pte
= pte_offset_kernel(pmd
, address
);
550 if (bad_address(pte
))
553 printk("PTE %lx", pte_val(*pte
));
561 #endif /* CONFIG_X86_64 */
564 * Workaround for K8 erratum #93 & buggy BIOS.
566 * BIOS SMM functions are required to use a specific workaround
567 * to avoid corruption of the 64bit RIP register on C stepping K8.
569 * A lot of BIOS that didn't get tested properly miss this.
571 * The OS sees this as a page fault with the upper 32bits of RIP cleared.
572 * Try to work around it here.
574 * Note we only handle faults in kernel here.
575 * Does nothing on 32-bit.
577 static int is_errata93(struct pt_regs
*regs
, unsigned long address
)
579 #if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD)
580 if (boot_cpu_data
.x86_vendor
!= X86_VENDOR_AMD
581 || boot_cpu_data
.x86
!= 0xf)
584 if (address
!= regs
->ip
)
587 if ((address
>> 32) != 0)
590 address
|= 0xffffffffUL
<< 32;
591 if ((address
>= (u64
)_stext
&& address
<= (u64
)_etext
) ||
592 (address
>= MODULES_VADDR
&& address
<= MODULES_END
)) {
593 printk_once(errata93_warning
);
602 * Work around K8 erratum #100 K8 in compat mode occasionally jumps
603 * to illegal addresses >4GB.
605 * We catch this in the page fault handler because these addresses
606 * are not reachable. Just detect this case and return. Any code
607 * segment in LDT is compatibility mode.
609 static int is_errata100(struct pt_regs
*regs
, unsigned long address
)
612 if ((regs
->cs
== __USER32_CS
|| (regs
->cs
& (1<<2))) && (address
>> 32))
618 static int is_f00f_bug(struct pt_regs
*regs
, unsigned long address
)
620 #ifdef CONFIG_X86_F00F_BUG
624 * Pentium F0 0F C7 C8 bug workaround:
626 if (boot_cpu_has_bug(X86_BUG_F00F
)) {
627 nr
= (address
- idt_descr
.address
) >> 3;
630 do_invalid_op(regs
, 0);
638 static const char nx_warning
[] = KERN_CRIT
639 "kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n";
640 static const char smep_warning
[] = KERN_CRIT
641 "unable to execute userspace code (SMEP?) (uid: %d)\n";
644 show_fault_oops(struct pt_regs
*regs
, unsigned long error_code
,
645 unsigned long address
)
647 if (!oops_may_print())
650 if (error_code
& PF_INSTR
) {
655 pgd
= __va(read_cr3() & PHYSICAL_PAGE_MASK
);
656 pgd
+= pgd_index(address
);
658 pte
= lookup_address_in_pgd(pgd
, address
, &level
);
660 if (pte
&& pte_present(*pte
) && !pte_exec(*pte
))
661 printk(nx_warning
, from_kuid(&init_user_ns
, current_uid()));
662 if (pte
&& pte_present(*pte
) && pte_exec(*pte
) &&
663 (pgd_flags(*pgd
) & _PAGE_USER
) &&
664 (__read_cr4() & X86_CR4_SMEP
))
665 printk(smep_warning
, from_kuid(&init_user_ns
, current_uid()));
668 printk(KERN_ALERT
"BUG: unable to handle kernel ");
669 if (address
< PAGE_SIZE
)
670 printk(KERN_CONT
"NULL pointer dereference");
672 printk(KERN_CONT
"paging request");
674 printk(KERN_CONT
" at %p\n", (void *) address
);
675 printk(KERN_ALERT
"IP:");
676 printk_address(regs
->ip
);
678 dump_pagetable(address
);
682 pgtable_bad(struct pt_regs
*regs
, unsigned long error_code
,
683 unsigned long address
)
685 struct task_struct
*tsk
;
689 flags
= oops_begin();
693 printk(KERN_ALERT
"%s: Corrupted page table at address %lx\n",
695 dump_pagetable(address
);
697 tsk
->thread
.cr2
= address
;
698 tsk
->thread
.trap_nr
= X86_TRAP_PF
;
699 tsk
->thread
.error_code
= error_code
;
701 if (__die("Bad pagetable", regs
, error_code
))
704 oops_end(flags
, regs
, sig
);
708 no_context(struct pt_regs
*regs
, unsigned long error_code
,
709 unsigned long address
, int signal
, int si_code
)
711 struct task_struct
*tsk
= current
;
714 /* No context means no VMA to pass down */
715 struct vm_area_struct
*vma
= NULL
;
717 /* Are we prepared to handle this kernel fault? */
718 if (fixup_exception(regs
)) {
720 * Any interrupt that takes a fault gets the fixup. This makes
721 * the below recursive fault logic only apply to a faults from
728 * Per the above we're !in_interrupt(), aka. task context.
730 * In this case we need to make sure we're not recursively
731 * faulting through the emulate_vsyscall() logic.
733 if (current_thread_info()->sig_on_uaccess_error
&& signal
) {
734 tsk
->thread
.trap_nr
= X86_TRAP_PF
;
735 tsk
->thread
.error_code
= error_code
| PF_USER
;
736 tsk
->thread
.cr2
= address
;
738 /* XXX: hwpoison faults will set the wrong code. */
739 force_sig_info_fault(signal
, si_code
, address
,
744 * Barring that, we can do the fixup and be happy.
752 * Valid to do another page fault here, because if this fault
753 * had been triggered by is_prefetch fixup_exception would have
758 * Hall of shame of CPU/BIOS bugs.
760 if (is_prefetch(regs
, error_code
, address
))
763 if (is_errata93(regs
, address
))
767 * Oops. The kernel tried to access some bad page. We'll have to
768 * terminate things with extreme prejudice:
770 flags
= oops_begin();
772 show_fault_oops(regs
, error_code
, address
);
774 if (task_stack_end_corrupted(tsk
))
775 printk(KERN_EMERG
"Thread overran stack, or stack corrupted\n");
777 tsk
->thread
.cr2
= address
;
778 tsk
->thread
.trap_nr
= X86_TRAP_PF
;
779 tsk
->thread
.error_code
= error_code
;
782 if (__die("Oops", regs
, error_code
))
785 /* Executive summary in case the body of the oops scrolled away */
786 printk(KERN_DEFAULT
"CR2: %016lx\n", address
);
788 oops_end(flags
, regs
, sig
);
792 * Print out info about fatal segfaults, if the show_unhandled_signals
796 show_signal_msg(struct pt_regs
*regs
, unsigned long error_code
,
797 unsigned long address
, struct task_struct
*tsk
)
799 if (!unhandled_signal(tsk
, SIGSEGV
))
802 if (!printk_ratelimit())
805 printk("%s%s[%d]: segfault at %lx ip %p sp %p error %lx",
806 task_pid_nr(tsk
) > 1 ? KERN_INFO
: KERN_EMERG
,
807 tsk
->comm
, task_pid_nr(tsk
), address
,
808 (void *)regs
->ip
, (void *)regs
->sp
, error_code
);
810 print_vma_addr(KERN_CONT
" in ", regs
->ip
);
812 printk(KERN_CONT
"\n");
816 __bad_area_nosemaphore(struct pt_regs
*regs
, unsigned long error_code
,
817 unsigned long address
, struct vm_area_struct
*vma
,
820 struct task_struct
*tsk
= current
;
822 /* User mode accesses just cause a SIGSEGV */
823 if (error_code
& PF_USER
) {
825 * It's possible to have interrupts off here:
830 * Valid to do another page fault here because this one came
833 if (is_prefetch(regs
, error_code
, address
))
836 if (is_errata100(regs
, address
))
841 * Instruction fetch faults in the vsyscall page might need
844 if (unlikely((error_code
& PF_INSTR
) &&
845 ((address
& ~0xfff) == VSYSCALL_ADDR
))) {
846 if (emulate_vsyscall(regs
, address
))
850 /* Kernel addresses are always protection faults: */
851 if (address
>= TASK_SIZE
)
852 error_code
|= PF_PROT
;
854 if (likely(show_unhandled_signals
))
855 show_signal_msg(regs
, error_code
, address
, tsk
);
857 tsk
->thread
.cr2
= address
;
858 tsk
->thread
.error_code
= error_code
;
859 tsk
->thread
.trap_nr
= X86_TRAP_PF
;
861 force_sig_info_fault(SIGSEGV
, si_code
, address
, tsk
, vma
, 0);
866 if (is_f00f_bug(regs
, address
))
869 no_context(regs
, error_code
, address
, SIGSEGV
, si_code
);
873 bad_area_nosemaphore(struct pt_regs
*regs
, unsigned long error_code
,
874 unsigned long address
, struct vm_area_struct
*vma
)
876 __bad_area_nosemaphore(regs
, error_code
, address
, vma
, SEGV_MAPERR
);
880 __bad_area(struct pt_regs
*regs
, unsigned long error_code
,
881 unsigned long address
, struct vm_area_struct
*vma
, int si_code
)
883 struct mm_struct
*mm
= current
->mm
;
886 * Something tried to access memory that isn't in our memory map..
887 * Fix it, but check if it's kernel or user first..
889 up_read(&mm
->mmap_sem
);
891 __bad_area_nosemaphore(regs
, error_code
, address
, vma
, si_code
);
895 bad_area(struct pt_regs
*regs
, unsigned long error_code
, unsigned long address
)
897 __bad_area(regs
, error_code
, address
, NULL
, SEGV_MAPERR
);
900 static inline bool bad_area_access_from_pkeys(unsigned long error_code
,
901 struct vm_area_struct
*vma
)
903 if (!boot_cpu_has(X86_FEATURE_OSPKE
))
905 if (error_code
& PF_PK
)
911 bad_area_access_error(struct pt_regs
*regs
, unsigned long error_code
,
912 unsigned long address
, struct vm_area_struct
*vma
)
915 * This OSPKE check is not strictly necessary at runtime.
916 * But, doing it this way allows compiler optimizations
917 * if pkeys are compiled out.
919 if (bad_area_access_from_pkeys(error_code
, vma
))
920 __bad_area(regs
, error_code
, address
, vma
, SEGV_PKUERR
);
922 __bad_area(regs
, error_code
, address
, vma
, SEGV_ACCERR
);
926 do_sigbus(struct pt_regs
*regs
, unsigned long error_code
, unsigned long address
,
927 struct vm_area_struct
*vma
, unsigned int fault
)
929 struct task_struct
*tsk
= current
;
930 int code
= BUS_ADRERR
;
932 /* Kernel mode? Handle exceptions or die: */
933 if (!(error_code
& PF_USER
)) {
934 no_context(regs
, error_code
, address
, SIGBUS
, BUS_ADRERR
);
938 /* User-space => ok to do another page fault: */
939 if (is_prefetch(regs
, error_code
, address
))
942 tsk
->thread
.cr2
= address
;
943 tsk
->thread
.error_code
= error_code
;
944 tsk
->thread
.trap_nr
= X86_TRAP_PF
;
946 #ifdef CONFIG_MEMORY_FAILURE
947 if (fault
& (VM_FAULT_HWPOISON
|VM_FAULT_HWPOISON_LARGE
)) {
949 "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
950 tsk
->comm
, tsk
->pid
, address
);
951 code
= BUS_MCEERR_AR
;
954 force_sig_info_fault(SIGBUS
, code
, address
, tsk
, vma
, fault
);
958 mm_fault_error(struct pt_regs
*regs
, unsigned long error_code
,
959 unsigned long address
, struct vm_area_struct
*vma
,
962 if (fatal_signal_pending(current
) && !(error_code
& PF_USER
)) {
963 no_context(regs
, error_code
, address
, 0, 0);
967 if (fault
& VM_FAULT_OOM
) {
968 /* Kernel mode? Handle exceptions or die: */
969 if (!(error_code
& PF_USER
)) {
970 no_context(regs
, error_code
, address
,
971 SIGSEGV
, SEGV_MAPERR
);
976 * We ran out of memory, call the OOM killer, and return the
977 * userspace (which will retry the fault, or kill us if we got
980 pagefault_out_of_memory();
982 if (fault
& (VM_FAULT_SIGBUS
|VM_FAULT_HWPOISON
|
983 VM_FAULT_HWPOISON_LARGE
))
984 do_sigbus(regs
, error_code
, address
, vma
, fault
);
985 else if (fault
& VM_FAULT_SIGSEGV
)
986 bad_area_nosemaphore(regs
, error_code
, address
, vma
);
992 static int spurious_fault_check(unsigned long error_code
, pte_t
*pte
)
994 if ((error_code
& PF_WRITE
) && !pte_write(*pte
))
997 if ((error_code
& PF_INSTR
) && !pte_exec(*pte
))
1000 * Note: We do not do lazy flushing on protection key
1001 * changes, so no spurious fault will ever set PF_PK.
1003 if ((error_code
& PF_PK
))
1010 * Handle a spurious fault caused by a stale TLB entry.
1012 * This allows us to lazily refresh the TLB when increasing the
1013 * permissions of a kernel page (RO -> RW or NX -> X). Doing it
1014 * eagerly is very expensive since that implies doing a full
1015 * cross-processor TLB flush, even if no stale TLB entries exist
1016 * on other processors.
1018 * Spurious faults may only occur if the TLB contains an entry with
1019 * fewer permission than the page table entry. Non-present (P = 0)
1020 * and reserved bit (R = 1) faults are never spurious.
1022 * There are no security implications to leaving a stale TLB when
1023 * increasing the permissions on a page.
1025 * Returns non-zero if a spurious fault was handled, zero otherwise.
1027 * See Intel Developer's Manual Vol 3 Section 4.10.4.3, bullet 3
1028 * (Optional Invalidation).
1031 spurious_fault(unsigned long error_code
, unsigned long address
)
1040 * Only writes to RO or instruction fetches from NX may cause
1043 * These could be from user or supervisor accesses but the TLB
1044 * is only lazily flushed after a kernel mapping protection
1045 * change, so user accesses are not expected to cause spurious
1048 if (error_code
!= (PF_WRITE
| PF_PROT
)
1049 && error_code
!= (PF_INSTR
| PF_PROT
))
1052 pgd
= init_mm
.pgd
+ pgd_index(address
);
1053 if (!pgd_present(*pgd
))
1056 pud
= pud_offset(pgd
, address
);
1057 if (!pud_present(*pud
))
1060 if (pud_large(*pud
))
1061 return spurious_fault_check(error_code
, (pte_t
*) pud
);
1063 pmd
= pmd_offset(pud
, address
);
1064 if (!pmd_present(*pmd
))
1067 if (pmd_large(*pmd
))
1068 return spurious_fault_check(error_code
, (pte_t
*) pmd
);
1070 pte
= pte_offset_kernel(pmd
, address
);
1071 if (!pte_present(*pte
))
1074 ret
= spurious_fault_check(error_code
, pte
);
1079 * Make sure we have permissions in PMD.
1080 * If not, then there's a bug in the page tables:
1082 ret
= spurious_fault_check(error_code
, (pte_t
*) pmd
);
1083 WARN_ONCE(!ret
, "PMD has incorrect permission bits\n");
1087 NOKPROBE_SYMBOL(spurious_fault
);
1089 int show_unhandled_signals
= 1;
1092 access_error(unsigned long error_code
, struct vm_area_struct
*vma
)
1095 * Access or read was blocked by protection keys. We do
1096 * this check before any others because we do not want
1097 * to, for instance, confuse a protection-key-denied
1098 * write with one for which we should do a COW.
1100 if (error_code
& PF_PK
)
1103 if (error_code
& PF_WRITE
) {
1104 /* write, present and write, not present: */
1105 if (unlikely(!(vma
->vm_flags
& VM_WRITE
)))
1110 /* read, present: */
1111 if (unlikely(error_code
& PF_PROT
))
1114 /* read, not present: */
1115 if (unlikely(!(vma
->vm_flags
& (VM_READ
| VM_EXEC
| VM_WRITE
))))
1121 static int fault_in_kernel_space(unsigned long address
)
1123 return address
>= TASK_SIZE_MAX
;
1126 static inline bool smap_violation(int error_code
, struct pt_regs
*regs
)
1128 if (!IS_ENABLED(CONFIG_X86_SMAP
))
1131 if (!static_cpu_has(X86_FEATURE_SMAP
))
1134 if (error_code
& PF_USER
)
1137 if (!user_mode(regs
) && (regs
->flags
& X86_EFLAGS_AC
))
1144 * This routine handles page faults. It determines the address,
1145 * and the problem, and then passes it off to one of the appropriate
1148 * This function must have noinline because both callers
1149 * {,trace_}do_page_fault() have notrace on. Having this an actual function
1150 * guarantees there's a function trace entry.
1152 static noinline
void
1153 __do_page_fault(struct pt_regs
*regs
, unsigned long error_code
,
1154 unsigned long address
)
1156 struct vm_area_struct
*vma
;
1157 struct task_struct
*tsk
;
1158 struct mm_struct
*mm
;
1159 int fault
, major
= 0;
1160 unsigned int flags
= FAULT_FLAG_ALLOW_RETRY
| FAULT_FLAG_KILLABLE
;
1166 * Detect and handle instructions that would cause a page fault for
1167 * both a tracked kernel page and a userspace page.
1169 if (kmemcheck_active(regs
))
1170 kmemcheck_hide(regs
);
1171 prefetchw(&mm
->mmap_sem
);
1173 if (unlikely(kmmio_fault(regs
, address
)))
1177 * We fault-in kernel-space virtual memory on-demand. The
1178 * 'reference' page table is init_mm.pgd.
1180 * NOTE! We MUST NOT take any locks for this case. We may
1181 * be in an interrupt or a critical region, and should
1182 * only copy the information from the master page table,
1185 * This verifies that the fault happens in kernel space
1186 * (error_code & 4) == 0, and that the fault was not a
1187 * protection error (error_code & 9) == 0.
1189 if (unlikely(fault_in_kernel_space(address
))) {
1190 if (!(error_code
& (PF_RSVD
| PF_USER
| PF_PROT
))) {
1191 if (vmalloc_fault(address
) >= 0)
1194 if (kmemcheck_fault(regs
, address
, error_code
))
1198 /* Can handle a stale RO->RW TLB: */
1199 if (spurious_fault(error_code
, address
))
1202 /* kprobes don't want to hook the spurious faults: */
1203 if (kprobes_fault(regs
))
1206 * Don't take the mm semaphore here. If we fixup a prefetch
1207 * fault we could otherwise deadlock:
1209 bad_area_nosemaphore(regs
, error_code
, address
, NULL
);
1214 /* kprobes don't want to hook the spurious faults: */
1215 if (unlikely(kprobes_fault(regs
)))
1218 if (unlikely(error_code
& PF_RSVD
))
1219 pgtable_bad(regs
, error_code
, address
);
1221 if (unlikely(smap_violation(error_code
, regs
))) {
1222 bad_area_nosemaphore(regs
, error_code
, address
, NULL
);
1227 * If we're in an interrupt, have no user context or are running
1228 * in a region with pagefaults disabled then we must not take the fault
1230 if (unlikely(faulthandler_disabled() || !mm
)) {
1231 bad_area_nosemaphore(regs
, error_code
, address
, NULL
);
1236 * It's safe to allow irq's after cr2 has been saved and the
1237 * vmalloc fault has been handled.
1239 * User-mode registers count as a user access even for any
1240 * potential system fault or CPU buglet:
1242 if (user_mode(regs
)) {
1244 error_code
|= PF_USER
;
1245 flags
|= FAULT_FLAG_USER
;
1247 if (regs
->flags
& X86_EFLAGS_IF
)
1251 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS
, 1, regs
, address
);
1253 if (error_code
& PF_WRITE
)
1254 flags
|= FAULT_FLAG_WRITE
;
1257 * When running in the kernel we expect faults to occur only to
1258 * addresses in user space. All other faults represent errors in
1259 * the kernel and should generate an OOPS. Unfortunately, in the
1260 * case of an erroneous fault occurring in a code path which already
1261 * holds mmap_sem we will deadlock attempting to validate the fault
1262 * against the address space. Luckily the kernel only validly
1263 * references user space from well defined areas of code, which are
1264 * listed in the exceptions table.
1266 * As the vast majority of faults will be valid we will only perform
1267 * the source reference check when there is a possibility of a
1268 * deadlock. Attempt to lock the address space, if we cannot we then
1269 * validate the source. If this is invalid we can skip the address
1270 * space check, thus avoiding the deadlock:
1272 if (unlikely(!down_read_trylock(&mm
->mmap_sem
))) {
1273 if ((error_code
& PF_USER
) == 0 &&
1274 !search_exception_tables(regs
->ip
)) {
1275 bad_area_nosemaphore(regs
, error_code
, address
, NULL
);
1279 down_read(&mm
->mmap_sem
);
1282 * The above down_read_trylock() might have succeeded in
1283 * which case we'll have missed the might_sleep() from
1289 vma
= find_vma(mm
, address
);
1290 if (unlikely(!vma
)) {
1291 bad_area(regs
, error_code
, address
);
1294 if (likely(vma
->vm_start
<= address
))
1296 if (unlikely(!(vma
->vm_flags
& VM_GROWSDOWN
))) {
1297 bad_area(regs
, error_code
, address
);
1300 if (error_code
& PF_USER
) {
1302 * Accessing the stack below %sp is always a bug.
1303 * The large cushion allows instructions like enter
1304 * and pusha to work. ("enter $65535, $31" pushes
1305 * 32 pointers and then decrements %sp by 65535.)
1307 if (unlikely(address
+ 65536 + 32 * sizeof(unsigned long) < regs
->sp
)) {
1308 bad_area(regs
, error_code
, address
);
1312 if (unlikely(expand_stack(vma
, address
))) {
1313 bad_area(regs
, error_code
, address
);
1318 * Ok, we have a good vm_area for this memory access, so
1319 * we can handle it..
1322 if (unlikely(access_error(error_code
, vma
))) {
1323 bad_area_access_error(regs
, error_code
, address
, vma
);
1328 * If for any reason at all we couldn't handle the fault,
1329 * make sure we exit gracefully rather than endlessly redo
1330 * the fault. Since we never set FAULT_FLAG_RETRY_NOWAIT, if
1331 * we get VM_FAULT_RETRY back, the mmap_sem has been unlocked.
1333 fault
= handle_mm_fault(mm
, vma
, address
, flags
);
1334 major
|= fault
& VM_FAULT_MAJOR
;
1337 * If we need to retry the mmap_sem has already been released,
1338 * and if there is a fatal signal pending there is no guarantee
1339 * that we made any progress. Handle this case first.
1341 if (unlikely(fault
& VM_FAULT_RETRY
)) {
1342 /* Retry at most once */
1343 if (flags
& FAULT_FLAG_ALLOW_RETRY
) {
1344 flags
&= ~FAULT_FLAG_ALLOW_RETRY
;
1345 flags
|= FAULT_FLAG_TRIED
;
1346 if (!fatal_signal_pending(tsk
))
1350 /* User mode? Just return to handle the fatal exception */
1351 if (flags
& FAULT_FLAG_USER
)
1354 /* Not returning to user mode? Handle exceptions or die: */
1355 no_context(regs
, error_code
, address
, SIGBUS
, BUS_ADRERR
);
1359 up_read(&mm
->mmap_sem
);
1360 if (unlikely(fault
& VM_FAULT_ERROR
)) {
1361 mm_fault_error(regs
, error_code
, address
, vma
, fault
);
1366 * Major/minor page fault accounting. If any of the events
1367 * returned VM_FAULT_MAJOR, we account it as a major fault.
1371 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ
, 1, regs
, address
);
1374 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN
, 1, regs
, address
);
1377 check_v8086_mode(regs
, address
, tsk
);
1379 NOKPROBE_SYMBOL(__do_page_fault
);
1381 dotraplinkage
void notrace
1382 do_page_fault(struct pt_regs
*regs
, unsigned long error_code
)
1384 unsigned long address
= read_cr2(); /* Get the faulting address */
1385 enum ctx_state prev_state
;
1388 * We must have this function tagged with __kprobes, notrace and call
1389 * read_cr2() before calling anything else. To avoid calling any kind
1390 * of tracing machinery before we've observed the CR2 value.
1392 * exception_{enter,exit}() contain all sorts of tracepoints.
1395 prev_state
= exception_enter();
1396 __do_page_fault(regs
, error_code
, address
);
1397 exception_exit(prev_state
);
1399 NOKPROBE_SYMBOL(do_page_fault
);
1401 #ifdef CONFIG_TRACING
1402 static nokprobe_inline
void
1403 trace_page_fault_entries(unsigned long address
, struct pt_regs
*regs
,
1404 unsigned long error_code
)
1406 if (user_mode(regs
))
1407 trace_page_fault_user(address
, regs
, error_code
);
1409 trace_page_fault_kernel(address
, regs
, error_code
);
1412 dotraplinkage
void notrace
1413 trace_do_page_fault(struct pt_regs
*regs
, unsigned long error_code
)
1416 * The exception_enter and tracepoint processing could
1417 * trigger another page faults (user space callchain
1418 * reading) and destroy the original cr2 value, so read
1419 * the faulting address now.
1421 unsigned long address
= read_cr2();
1422 enum ctx_state prev_state
;
1424 prev_state
= exception_enter();
1425 trace_page_fault_entries(address
, regs
, error_code
);
1426 __do_page_fault(regs
, error_code
, address
);
1427 exception_exit(prev_state
);
1429 NOKPROBE_SYMBOL(trace_do_page_fault
);
1430 #endif /* CONFIG_TRACING */