2 * Copyright (C) 1995 Linus Torvalds
3 * Copyright (C) 2001, 2002 Andi Kleen, SuSE Labs.
4 * Copyright (C) 2008-2009, Red Hat Inc., Ingo Molnar
6 #include <linux/sched.h> /* test_thread_flag(), ... */
7 #include <linux/sched/task_stack.h> /* task_stack_*(), ... */
8 #include <linux/kdebug.h> /* oops_begin/end, ... */
9 #include <linux/extable.h> /* search_exception_tables */
10 #include <linux/bootmem.h> /* max_low_pfn */
11 #include <linux/kprobes.h> /* NOKPROBE_SYMBOL, ... */
12 #include <linux/mmiotrace.h> /* kmmio_handler, ... */
13 #include <linux/perf_event.h> /* perf_sw_event */
14 #include <linux/hugetlb.h> /* hstate_index_to_shift */
15 #include <linux/prefetch.h> /* prefetchw */
16 #include <linux/context_tracking.h> /* exception_enter(), ... */
17 #include <linux/uaccess.h> /* faulthandler_disabled() */
19 #include <asm/cpufeature.h> /* boot_cpu_has, ... */
20 #include <asm/traps.h> /* dotraplinkage, ... */
21 #include <asm/pgalloc.h> /* pgd_*(), ... */
22 #include <asm/kmemcheck.h> /* kmemcheck_*(), ... */
23 #include <asm/fixmap.h> /* VSYSCALL_ADDR */
24 #include <asm/vsyscall.h> /* emulate_vsyscall */
25 #include <asm/vm86.h> /* struct vm86 */
26 #include <asm/mmu_context.h> /* vma_pkey() */
28 #define CREATE_TRACE_POINTS
29 #include <asm/trace/exceptions.h>
32 * Page fault error code bits:
34 * bit 0 == 0: no page found 1: protection fault
35 * bit 1 == 0: read access 1: write access
36 * bit 2 == 0: kernel-mode access 1: user-mode access
37 * bit 3 == 1: use of reserved bit detected
38 * bit 4 == 1: fault was an instruction fetch
39 * bit 5 == 1: protection keys block access
41 enum x86_pf_error_code
{
52 * Returns 0 if mmiotrace is disabled, or if the fault is not
53 * handled by mmiotrace:
55 static nokprobe_inline
int
56 kmmio_fault(struct pt_regs
*regs
, unsigned long addr
)
58 if (unlikely(is_kmmio_active()))
59 if (kmmio_handler(regs
, addr
) == 1)
64 static nokprobe_inline
int kprobes_fault(struct pt_regs
*regs
)
68 /* kprobe_running() needs smp_processor_id() */
69 if (kprobes_built_in() && !user_mode(regs
)) {
71 if (kprobe_running() && kprobe_fault_handler(regs
, 14))
84 * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
85 * Check that here and ignore it.
89 * Sometimes the CPU reports invalid exceptions on prefetch.
90 * Check that here and ignore it.
92 * Opcode checker based on code by Richard Brunner.
95 check_prefetch_opcode(struct pt_regs
*regs
, unsigned char *instr
,
96 unsigned char opcode
, int *prefetch
)
98 unsigned char instr_hi
= opcode
& 0xf0;
99 unsigned char instr_lo
= opcode
& 0x0f;
105 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes.
106 * In X86_64 long mode, the CPU will signal invalid
107 * opcode if some of these prefixes are present so
108 * X86_64 will never get here anyway
110 return ((instr_lo
& 7) == 0x6);
114 * In AMD64 long mode 0x40..0x4F are valid REX prefixes
115 * Need to figure out under what instruction mode the
116 * instruction was issued. Could check the LDT for lm,
117 * but for now it's good enough to assume that long
118 * mode only uses well known segments or kernel.
120 return (!user_mode(regs
) || user_64bit_mode(regs
));
123 /* 0x64 thru 0x67 are valid prefixes in all modes. */
124 return (instr_lo
& 0xC) == 0x4;
126 /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */
127 return !instr_lo
|| (instr_lo
>>1) == 1;
129 /* Prefetch instruction is 0x0F0D or 0x0F18 */
130 if (probe_kernel_address(instr
, opcode
))
133 *prefetch
= (instr_lo
== 0xF) &&
134 (opcode
== 0x0D || opcode
== 0x18);
142 is_prefetch(struct pt_regs
*regs
, unsigned long error_code
, unsigned long addr
)
144 unsigned char *max_instr
;
145 unsigned char *instr
;
149 * If it was a exec (instruction fetch) fault on NX page, then
150 * do not ignore the fault:
152 if (error_code
& PF_INSTR
)
155 instr
= (void *)convert_ip_to_linear(current
, regs
);
156 max_instr
= instr
+ 15;
158 if (user_mode(regs
) && instr
>= (unsigned char *)TASK_SIZE_MAX
)
161 while (instr
< max_instr
) {
162 unsigned char opcode
;
164 if (probe_kernel_address(instr
, opcode
))
169 if (!check_prefetch_opcode(regs
, instr
, opcode
, &prefetch
))
176 * A protection key fault means that the PKRU value did not allow
177 * access to some PTE. Userspace can figure out what PKRU was
178 * from the XSAVE state, and this function fills out a field in
179 * siginfo so userspace can discover which protection key was set
182 * If we get here, we know that the hardware signaled a PF_PK
183 * fault and that there was a VMA once we got in the fault
184 * handler. It does *not* guarantee that the VMA we find here
185 * was the one that we faulted on.
187 * 1. T1 : mprotect_key(foo, PAGE_SIZE, pkey=4);
188 * 2. T1 : set PKRU to deny access to pkey=4, touches page
190 * 4. T2: mprotect_key(foo, PAGE_SIZE, pkey=5);
191 * 5. T1 : enters fault handler, takes mmap_sem, etc...
192 * 6. T1 : reaches here, sees vma_pkey(vma)=5, when we really
193 * faulted on a pte with its pkey=4.
195 static void fill_sig_info_pkey(int si_code
, siginfo_t
*info
, u32
*pkey
)
197 /* This is effectively an #ifdef */
198 if (!boot_cpu_has(X86_FEATURE_OSPKE
))
201 /* Fault not from Protection Keys: nothing to do */
202 if (si_code
!= SEGV_PKUERR
)
205 * force_sig_info_fault() is called from a number of
206 * contexts, some of which have a VMA and some of which
207 * do not. The PF_PK handing happens after we have a
208 * valid VMA, so we should never reach this without a
212 WARN_ONCE(1, "PKU fault with no VMA passed in");
217 * si_pkey should be thought of as a strong hint, but not
218 * absolutely guranteed to be 100% accurate because of
219 * the race explained above.
221 info
->si_pkey
= *pkey
;
225 force_sig_info_fault(int si_signo
, int si_code
, unsigned long address
,
226 struct task_struct
*tsk
, u32
*pkey
, int fault
)
231 info
.si_signo
= si_signo
;
233 info
.si_code
= si_code
;
234 info
.si_addr
= (void __user
*)address
;
235 if (fault
& VM_FAULT_HWPOISON_LARGE
)
236 lsb
= hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault
));
237 if (fault
& VM_FAULT_HWPOISON
)
239 info
.si_addr_lsb
= lsb
;
241 fill_sig_info_pkey(si_code
, &info
, pkey
);
243 force_sig_info(si_signo
, &info
, tsk
);
246 DEFINE_SPINLOCK(pgd_lock
);
250 static inline pmd_t
*vmalloc_sync_one(pgd_t
*pgd
, unsigned long address
)
252 unsigned index
= pgd_index(address
);
259 pgd_k
= init_mm
.pgd
+ index
;
261 if (!pgd_present(*pgd_k
))
265 * set_pgd(pgd, *pgd_k); here would be useless on PAE
266 * and redundant with the set_pmd() on non-PAE. As would
269 p4d
= p4d_offset(pgd
, address
);
270 p4d_k
= p4d_offset(pgd_k
, address
);
271 if (!p4d_present(*p4d_k
))
274 pud
= pud_offset(p4d
, address
);
275 pud_k
= pud_offset(p4d_k
, address
);
276 if (!pud_present(*pud_k
))
279 pmd
= pmd_offset(pud
, address
);
280 pmd_k
= pmd_offset(pud_k
, address
);
281 if (!pmd_present(*pmd_k
))
284 if (!pmd_present(*pmd
))
285 set_pmd(pmd
, *pmd_k
);
287 BUG_ON(pmd_page(*pmd
) != pmd_page(*pmd_k
));
292 void vmalloc_sync_all(void)
294 unsigned long address
;
296 if (SHARED_KERNEL_PMD
)
299 for (address
= VMALLOC_START
& PMD_MASK
;
300 address
>= TASK_SIZE_MAX
&& address
< FIXADDR_TOP
;
301 address
+= PMD_SIZE
) {
304 spin_lock(&pgd_lock
);
305 list_for_each_entry(page
, &pgd_list
, lru
) {
306 spinlock_t
*pgt_lock
;
309 /* the pgt_lock only for Xen */
310 pgt_lock
= &pgd_page_get_mm(page
)->page_table_lock
;
313 ret
= vmalloc_sync_one(page_address(page
), address
);
314 spin_unlock(pgt_lock
);
319 spin_unlock(&pgd_lock
);
326 * Handle a fault on the vmalloc or module mapping area
328 static noinline
int vmalloc_fault(unsigned long address
)
330 unsigned long pgd_paddr
;
334 /* Make sure we are in vmalloc area: */
335 if (!(address
>= VMALLOC_START
&& address
< VMALLOC_END
))
338 WARN_ON_ONCE(in_nmi());
341 * Synchronize this task's top level page-table
342 * with the 'reference' page table.
344 * Do _not_ use "current" here. We might be inside
345 * an interrupt in the middle of a task switch..
347 pgd_paddr
= read_cr3_pa();
348 pmd_k
= vmalloc_sync_one(__va(pgd_paddr
), address
);
352 if (pmd_huge(*pmd_k
))
355 pte_k
= pte_offset_kernel(pmd_k
, address
);
356 if (!pte_present(*pte_k
))
361 NOKPROBE_SYMBOL(vmalloc_fault
);
364 * Did it hit the DOS screen memory VA from vm86 mode?
367 check_v8086_mode(struct pt_regs
*regs
, unsigned long address
,
368 struct task_struct
*tsk
)
373 if (!v8086_mode(regs
) || !tsk
->thread
.vm86
)
376 bit
= (address
- 0xA0000) >> PAGE_SHIFT
;
378 tsk
->thread
.vm86
->screen_bitmap
|= 1 << bit
;
382 static bool low_pfn(unsigned long pfn
)
384 return pfn
< max_low_pfn
;
387 static void dump_pagetable(unsigned long address
)
389 pgd_t
*base
= __va(read_cr3_pa());
390 pgd_t
*pgd
= &base
[pgd_index(address
)];
396 #ifdef CONFIG_X86_PAE
397 pr_info("*pdpt = %016Lx ", pgd_val(*pgd
));
398 if (!low_pfn(pgd_val(*pgd
) >> PAGE_SHIFT
) || !pgd_present(*pgd
))
400 #define pr_pde pr_cont
402 #define pr_pde pr_info
404 p4d
= p4d_offset(pgd
, address
);
405 pud
= pud_offset(p4d
, address
);
406 pmd
= pmd_offset(pud
, address
);
407 pr_pde("*pde = %0*Lx ", sizeof(*pmd
) * 2, (u64
)pmd_val(*pmd
));
411 * We must not directly access the pte in the highpte
412 * case if the page table is located in highmem.
413 * And let's rather not kmap-atomic the pte, just in case
414 * it's allocated already:
416 if (!low_pfn(pmd_pfn(*pmd
)) || !pmd_present(*pmd
) || pmd_large(*pmd
))
419 pte
= pte_offset_kernel(pmd
, address
);
420 pr_cont("*pte = %0*Lx ", sizeof(*pte
) * 2, (u64
)pte_val(*pte
));
425 #else /* CONFIG_X86_64: */
427 void vmalloc_sync_all(void)
429 sync_global_pgds(VMALLOC_START
& PGDIR_MASK
, VMALLOC_END
);
435 * Handle a fault on the vmalloc area
437 static noinline
int vmalloc_fault(unsigned long address
)
439 pgd_t
*pgd
, *pgd_ref
;
440 p4d_t
*p4d
, *p4d_ref
;
441 pud_t
*pud
, *pud_ref
;
442 pmd_t
*pmd
, *pmd_ref
;
443 pte_t
*pte
, *pte_ref
;
445 /* Make sure we are in vmalloc area: */
446 if (!(address
>= VMALLOC_START
&& address
< VMALLOC_END
))
449 WARN_ON_ONCE(in_nmi());
452 * Copy kernel mappings over when needed. This can also
453 * happen within a race in page table update. In the later
456 pgd
= (pgd_t
*)__va(read_cr3_pa()) + pgd_index(address
);
457 pgd_ref
= pgd_offset_k(address
);
458 if (pgd_none(*pgd_ref
))
461 if (pgd_none(*pgd
)) {
462 set_pgd(pgd
, *pgd_ref
);
463 arch_flush_lazy_mmu_mode();
464 } else if (CONFIG_PGTABLE_LEVELS
> 4) {
466 * With folded p4d, pgd_none() is always false, so the pgd may
467 * point to an empty page table entry and pgd_page_vaddr()
468 * will return garbage.
470 * We will do the correct sanity check on the p4d level.
472 BUG_ON(pgd_page_vaddr(*pgd
) != pgd_page_vaddr(*pgd_ref
));
475 /* With 4-level paging, copying happens on the p4d level. */
476 p4d
= p4d_offset(pgd
, address
);
477 p4d_ref
= p4d_offset(pgd_ref
, address
);
478 if (p4d_none(*p4d_ref
))
481 if (p4d_none(*p4d
)) {
482 set_p4d(p4d
, *p4d_ref
);
483 arch_flush_lazy_mmu_mode();
485 BUG_ON(p4d_pfn(*p4d
) != p4d_pfn(*p4d_ref
));
489 * Below here mismatches are bugs because these lower tables
493 pud
= pud_offset(p4d
, address
);
494 pud_ref
= pud_offset(p4d_ref
, address
);
495 if (pud_none(*pud_ref
))
498 if (pud_none(*pud
) || pud_pfn(*pud
) != pud_pfn(*pud_ref
))
504 pmd
= pmd_offset(pud
, address
);
505 pmd_ref
= pmd_offset(pud_ref
, address
);
506 if (pmd_none(*pmd_ref
))
509 if (pmd_none(*pmd
) || pmd_pfn(*pmd
) != pmd_pfn(*pmd_ref
))
515 pte_ref
= pte_offset_kernel(pmd_ref
, address
);
516 if (!pte_present(*pte_ref
))
519 pte
= pte_offset_kernel(pmd
, address
);
522 * Don't use pte_page here, because the mappings can point
523 * outside mem_map, and the NUMA hash lookup cannot handle
526 if (!pte_present(*pte
) || pte_pfn(*pte
) != pte_pfn(*pte_ref
))
531 NOKPROBE_SYMBOL(vmalloc_fault
);
533 #ifdef CONFIG_CPU_SUP_AMD
534 static const char errata93_warning
[] =
536 "******* Your BIOS seems to not contain a fix for K8 errata #93\n"
537 "******* Working around it, but it may cause SEGVs or burn power.\n"
538 "******* Please consider a BIOS update.\n"
539 "******* Disabling USB legacy in the BIOS may also help.\n";
543 * No vm86 mode in 64-bit mode:
546 check_v8086_mode(struct pt_regs
*regs
, unsigned long address
,
547 struct task_struct
*tsk
)
551 static int bad_address(void *p
)
555 return probe_kernel_address((unsigned long *)p
, dummy
);
558 static void dump_pagetable(unsigned long address
)
560 pgd_t
*base
= __va(read_cr3_pa());
561 pgd_t
*pgd
= base
+ pgd_index(address
);
567 if (bad_address(pgd
))
570 pr_info("PGD %lx ", pgd_val(*pgd
));
572 if (!pgd_present(*pgd
))
575 p4d
= p4d_offset(pgd
, address
);
576 if (bad_address(p4d
))
579 pr_cont("P4D %lx ", p4d_val(*p4d
));
580 if (!p4d_present(*p4d
) || p4d_large(*p4d
))
583 pud
= pud_offset(p4d
, address
);
584 if (bad_address(pud
))
587 pr_cont("PUD %lx ", pud_val(*pud
));
588 if (!pud_present(*pud
) || pud_large(*pud
))
591 pmd
= pmd_offset(pud
, address
);
592 if (bad_address(pmd
))
595 pr_cont("PMD %lx ", pmd_val(*pmd
));
596 if (!pmd_present(*pmd
) || pmd_large(*pmd
))
599 pte
= pte_offset_kernel(pmd
, address
);
600 if (bad_address(pte
))
603 pr_cont("PTE %lx", pte_val(*pte
));
611 #endif /* CONFIG_X86_64 */
614 * Workaround for K8 erratum #93 & buggy BIOS.
616 * BIOS SMM functions are required to use a specific workaround
617 * to avoid corruption of the 64bit RIP register on C stepping K8.
619 * A lot of BIOS that didn't get tested properly miss this.
621 * The OS sees this as a page fault with the upper 32bits of RIP cleared.
622 * Try to work around it here.
624 * Note we only handle faults in kernel here.
625 * Does nothing on 32-bit.
627 static int is_errata93(struct pt_regs
*regs
, unsigned long address
)
629 #if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD)
630 if (boot_cpu_data
.x86_vendor
!= X86_VENDOR_AMD
631 || boot_cpu_data
.x86
!= 0xf)
634 if (address
!= regs
->ip
)
637 if ((address
>> 32) != 0)
640 address
|= 0xffffffffUL
<< 32;
641 if ((address
>= (u64
)_stext
&& address
<= (u64
)_etext
) ||
642 (address
>= MODULES_VADDR
&& address
<= MODULES_END
)) {
643 printk_once(errata93_warning
);
652 * Work around K8 erratum #100 K8 in compat mode occasionally jumps
653 * to illegal addresses >4GB.
655 * We catch this in the page fault handler because these addresses
656 * are not reachable. Just detect this case and return. Any code
657 * segment in LDT is compatibility mode.
659 static int is_errata100(struct pt_regs
*regs
, unsigned long address
)
662 if ((regs
->cs
== __USER32_CS
|| (regs
->cs
& (1<<2))) && (address
>> 32))
668 static int is_f00f_bug(struct pt_regs
*regs
, unsigned long address
)
670 #ifdef CONFIG_X86_F00F_BUG
674 * Pentium F0 0F C7 C8 bug workaround:
676 if (boot_cpu_has_bug(X86_BUG_F00F
)) {
677 nr
= (address
- idt_descr
.address
) >> 3;
680 do_invalid_op(regs
, 0);
688 static const char nx_warning
[] = KERN_CRIT
689 "kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n";
690 static const char smep_warning
[] = KERN_CRIT
691 "unable to execute userspace code (SMEP?) (uid: %d)\n";
694 show_fault_oops(struct pt_regs
*regs
, unsigned long error_code
,
695 unsigned long address
)
697 if (!oops_may_print())
700 if (error_code
& PF_INSTR
) {
705 pgd
= __va(read_cr3_pa());
706 pgd
+= pgd_index(address
);
708 pte
= lookup_address_in_pgd(pgd
, address
, &level
);
710 if (pte
&& pte_present(*pte
) && !pte_exec(*pte
))
711 printk(nx_warning
, from_kuid(&init_user_ns
, current_uid()));
712 if (pte
&& pte_present(*pte
) && pte_exec(*pte
) &&
713 (pgd_flags(*pgd
) & _PAGE_USER
) &&
714 (__read_cr4() & X86_CR4_SMEP
))
715 printk(smep_warning
, from_kuid(&init_user_ns
, current_uid()));
718 printk(KERN_ALERT
"BUG: unable to handle kernel ");
719 if (address
< PAGE_SIZE
)
720 printk(KERN_CONT
"NULL pointer dereference");
722 printk(KERN_CONT
"paging request");
724 printk(KERN_CONT
" at %p\n", (void *) address
);
725 printk(KERN_ALERT
"IP: %pS\n", (void *)regs
->ip
);
727 dump_pagetable(address
);
731 pgtable_bad(struct pt_regs
*regs
, unsigned long error_code
,
732 unsigned long address
)
734 struct task_struct
*tsk
;
738 flags
= oops_begin();
742 printk(KERN_ALERT
"%s: Corrupted page table at address %lx\n",
744 dump_pagetable(address
);
746 tsk
->thread
.cr2
= address
;
747 tsk
->thread
.trap_nr
= X86_TRAP_PF
;
748 tsk
->thread
.error_code
= error_code
;
750 if (__die("Bad pagetable", regs
, error_code
))
753 oops_end(flags
, regs
, sig
);
757 no_context(struct pt_regs
*regs
, unsigned long error_code
,
758 unsigned long address
, int signal
, int si_code
)
760 struct task_struct
*tsk
= current
;
764 /* Are we prepared to handle this kernel fault? */
765 if (fixup_exception(regs
, X86_TRAP_PF
)) {
767 * Any interrupt that takes a fault gets the fixup. This makes
768 * the below recursive fault logic only apply to a faults from
775 * Per the above we're !in_interrupt(), aka. task context.
777 * In this case we need to make sure we're not recursively
778 * faulting through the emulate_vsyscall() logic.
780 if (current
->thread
.sig_on_uaccess_err
&& signal
) {
781 tsk
->thread
.trap_nr
= X86_TRAP_PF
;
782 tsk
->thread
.error_code
= error_code
| PF_USER
;
783 tsk
->thread
.cr2
= address
;
785 /* XXX: hwpoison faults will set the wrong code. */
786 force_sig_info_fault(signal
, si_code
, address
,
791 * Barring that, we can do the fixup and be happy.
796 #ifdef CONFIG_VMAP_STACK
798 * Stack overflow? During boot, we can fault near the initial
799 * stack in the direct map, but that's not an overflow -- check
800 * that we're in vmalloc space to avoid this.
802 if (is_vmalloc_addr((void *)address
) &&
803 (((unsigned long)tsk
->stack
- 1 - address
< PAGE_SIZE
) ||
804 address
- ((unsigned long)tsk
->stack
+ THREAD_SIZE
) < PAGE_SIZE
)) {
805 unsigned long stack
= this_cpu_read(orig_ist
.ist
[DOUBLEFAULT_STACK
]) - sizeof(void *);
807 * We're likely to be running with very little stack space
808 * left. It's plausible that we'd hit this condition but
809 * double-fault even before we get this far, in which case
810 * we're fine: the double-fault handler will deal with it.
812 * We don't want to make it all the way into the oops code
813 * and then double-fault, though, because we're likely to
814 * break the console driver and lose most of the stack dump.
816 asm volatile ("movq %[stack], %%rsp\n\t"
817 "call handle_stack_overflow\n\t"
819 : ASM_CALL_CONSTRAINT
820 : "D" ("kernel stack overflow (page fault)"),
821 "S" (regs
), "d" (address
),
822 [stack
] "rm" (stack
));
830 * Valid to do another page fault here, because if this fault
831 * had been triggered by is_prefetch fixup_exception would have
836 * Hall of shame of CPU/BIOS bugs.
838 if (is_prefetch(regs
, error_code
, address
))
841 if (is_errata93(regs
, address
))
845 * Oops. The kernel tried to access some bad page. We'll have to
846 * terminate things with extreme prejudice:
848 flags
= oops_begin();
850 show_fault_oops(regs
, error_code
, address
);
852 if (task_stack_end_corrupted(tsk
))
853 printk(KERN_EMERG
"Thread overran stack, or stack corrupted\n");
855 tsk
->thread
.cr2
= address
;
856 tsk
->thread
.trap_nr
= X86_TRAP_PF
;
857 tsk
->thread
.error_code
= error_code
;
860 if (__die("Oops", regs
, error_code
))
863 /* Executive summary in case the body of the oops scrolled away */
864 printk(KERN_DEFAULT
"CR2: %016lx\n", address
);
866 oops_end(flags
, regs
, sig
);
870 * Print out info about fatal segfaults, if the show_unhandled_signals
874 show_signal_msg(struct pt_regs
*regs
, unsigned long error_code
,
875 unsigned long address
, struct task_struct
*tsk
)
877 if (!unhandled_signal(tsk
, SIGSEGV
))
880 if (!printk_ratelimit())
883 printk("%s%s[%d]: segfault at %lx ip %p sp %p error %lx",
884 task_pid_nr(tsk
) > 1 ? KERN_INFO
: KERN_EMERG
,
885 tsk
->comm
, task_pid_nr(tsk
), address
,
886 (void *)regs
->ip
, (void *)regs
->sp
, error_code
);
888 print_vma_addr(KERN_CONT
" in ", regs
->ip
);
890 printk(KERN_CONT
"\n");
894 __bad_area_nosemaphore(struct pt_regs
*regs
, unsigned long error_code
,
895 unsigned long address
, u32
*pkey
, int si_code
)
897 struct task_struct
*tsk
= current
;
899 /* User mode accesses just cause a SIGSEGV */
900 if (error_code
& PF_USER
) {
902 * It's possible to have interrupts off here:
907 * Valid to do another page fault here because this one came
910 if (is_prefetch(regs
, error_code
, address
))
913 if (is_errata100(regs
, address
))
918 * Instruction fetch faults in the vsyscall page might need
921 if (unlikely((error_code
& PF_INSTR
) &&
922 ((address
& ~0xfff) == VSYSCALL_ADDR
))) {
923 if (emulate_vsyscall(regs
, address
))
929 * To avoid leaking information about the kernel page table
930 * layout, pretend that user-mode accesses to kernel addresses
931 * are always protection faults.
933 if (address
>= TASK_SIZE_MAX
)
934 error_code
|= PF_PROT
;
936 if (likely(show_unhandled_signals
))
937 show_signal_msg(regs
, error_code
, address
, tsk
);
939 tsk
->thread
.cr2
= address
;
940 tsk
->thread
.error_code
= error_code
;
941 tsk
->thread
.trap_nr
= X86_TRAP_PF
;
943 force_sig_info_fault(SIGSEGV
, si_code
, address
, tsk
, pkey
, 0);
948 if (is_f00f_bug(regs
, address
))
951 no_context(regs
, error_code
, address
, SIGSEGV
, si_code
);
955 bad_area_nosemaphore(struct pt_regs
*regs
, unsigned long error_code
,
956 unsigned long address
, u32
*pkey
)
958 __bad_area_nosemaphore(regs
, error_code
, address
, pkey
, SEGV_MAPERR
);
962 __bad_area(struct pt_regs
*regs
, unsigned long error_code
,
963 unsigned long address
, struct vm_area_struct
*vma
, int si_code
)
965 struct mm_struct
*mm
= current
->mm
;
969 pkey
= vma_pkey(vma
);
972 * Something tried to access memory that isn't in our memory map..
973 * Fix it, but check if it's kernel or user first..
975 up_read(&mm
->mmap_sem
);
977 __bad_area_nosemaphore(regs
, error_code
, address
,
978 (vma
) ? &pkey
: NULL
, si_code
);
982 bad_area(struct pt_regs
*regs
, unsigned long error_code
, unsigned long address
)
984 __bad_area(regs
, error_code
, address
, NULL
, SEGV_MAPERR
);
987 static inline bool bad_area_access_from_pkeys(unsigned long error_code
,
988 struct vm_area_struct
*vma
)
990 /* This code is always called on the current mm */
991 bool foreign
= false;
993 if (!boot_cpu_has(X86_FEATURE_OSPKE
))
995 if (error_code
& PF_PK
)
997 /* this checks permission keys on the VMA: */
998 if (!arch_vma_access_permitted(vma
, (error_code
& PF_WRITE
),
999 (error_code
& PF_INSTR
), foreign
))
1004 static noinline
void
1005 bad_area_access_error(struct pt_regs
*regs
, unsigned long error_code
,
1006 unsigned long address
, struct vm_area_struct
*vma
)
1009 * This OSPKE check is not strictly necessary at runtime.
1010 * But, doing it this way allows compiler optimizations
1011 * if pkeys are compiled out.
1013 if (bad_area_access_from_pkeys(error_code
, vma
))
1014 __bad_area(regs
, error_code
, address
, vma
, SEGV_PKUERR
);
1016 __bad_area(regs
, error_code
, address
, vma
, SEGV_ACCERR
);
1020 do_sigbus(struct pt_regs
*regs
, unsigned long error_code
, unsigned long address
,
1021 u32
*pkey
, unsigned int fault
)
1023 struct task_struct
*tsk
= current
;
1024 int code
= BUS_ADRERR
;
1026 /* Kernel mode? Handle exceptions or die: */
1027 if (!(error_code
& PF_USER
)) {
1028 no_context(regs
, error_code
, address
, SIGBUS
, BUS_ADRERR
);
1032 /* User-space => ok to do another page fault: */
1033 if (is_prefetch(regs
, error_code
, address
))
1036 tsk
->thread
.cr2
= address
;
1037 tsk
->thread
.error_code
= error_code
;
1038 tsk
->thread
.trap_nr
= X86_TRAP_PF
;
1040 #ifdef CONFIG_MEMORY_FAILURE
1041 if (fault
& (VM_FAULT_HWPOISON
|VM_FAULT_HWPOISON_LARGE
)) {
1043 "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
1044 tsk
->comm
, tsk
->pid
, address
);
1045 code
= BUS_MCEERR_AR
;
1048 force_sig_info_fault(SIGBUS
, code
, address
, tsk
, pkey
, fault
);
1051 static noinline
void
1052 mm_fault_error(struct pt_regs
*regs
, unsigned long error_code
,
1053 unsigned long address
, u32
*pkey
, unsigned int fault
)
1055 if (fatal_signal_pending(current
) && !(error_code
& PF_USER
)) {
1056 no_context(regs
, error_code
, address
, 0, 0);
1060 if (fault
& VM_FAULT_OOM
) {
1061 /* Kernel mode? Handle exceptions or die: */
1062 if (!(error_code
& PF_USER
)) {
1063 no_context(regs
, error_code
, address
,
1064 SIGSEGV
, SEGV_MAPERR
);
1069 * We ran out of memory, call the OOM killer, and return the
1070 * userspace (which will retry the fault, or kill us if we got
1073 pagefault_out_of_memory();
1075 if (fault
& (VM_FAULT_SIGBUS
|VM_FAULT_HWPOISON
|
1076 VM_FAULT_HWPOISON_LARGE
))
1077 do_sigbus(regs
, error_code
, address
, pkey
, fault
);
1078 else if (fault
& VM_FAULT_SIGSEGV
)
1079 bad_area_nosemaphore(regs
, error_code
, address
, pkey
);
1085 static int spurious_fault_check(unsigned long error_code
, pte_t
*pte
)
1087 if ((error_code
& PF_WRITE
) && !pte_write(*pte
))
1090 if ((error_code
& PF_INSTR
) && !pte_exec(*pte
))
1093 * Note: We do not do lazy flushing on protection key
1094 * changes, so no spurious fault will ever set PF_PK.
1096 if ((error_code
& PF_PK
))
1103 * Handle a spurious fault caused by a stale TLB entry.
1105 * This allows us to lazily refresh the TLB when increasing the
1106 * permissions of a kernel page (RO -> RW or NX -> X). Doing it
1107 * eagerly is very expensive since that implies doing a full
1108 * cross-processor TLB flush, even if no stale TLB entries exist
1109 * on other processors.
1111 * Spurious faults may only occur if the TLB contains an entry with
1112 * fewer permission than the page table entry. Non-present (P = 0)
1113 * and reserved bit (R = 1) faults are never spurious.
1115 * There are no security implications to leaving a stale TLB when
1116 * increasing the permissions on a page.
1118 * Returns non-zero if a spurious fault was handled, zero otherwise.
1120 * See Intel Developer's Manual Vol 3 Section 4.10.4.3, bullet 3
1121 * (Optional Invalidation).
1124 spurious_fault(unsigned long error_code
, unsigned long address
)
1134 * Only writes to RO or instruction fetches from NX may cause
1137 * These could be from user or supervisor accesses but the TLB
1138 * is only lazily flushed after a kernel mapping protection
1139 * change, so user accesses are not expected to cause spurious
1142 if (error_code
!= (PF_WRITE
| PF_PROT
)
1143 && error_code
!= (PF_INSTR
| PF_PROT
))
1146 pgd
= init_mm
.pgd
+ pgd_index(address
);
1147 if (!pgd_present(*pgd
))
1150 p4d
= p4d_offset(pgd
, address
);
1151 if (!p4d_present(*p4d
))
1154 if (p4d_large(*p4d
))
1155 return spurious_fault_check(error_code
, (pte_t
*) p4d
);
1157 pud
= pud_offset(p4d
, address
);
1158 if (!pud_present(*pud
))
1161 if (pud_large(*pud
))
1162 return spurious_fault_check(error_code
, (pte_t
*) pud
);
1164 pmd
= pmd_offset(pud
, address
);
1165 if (!pmd_present(*pmd
))
1168 if (pmd_large(*pmd
))
1169 return spurious_fault_check(error_code
, (pte_t
*) pmd
);
1171 pte
= pte_offset_kernel(pmd
, address
);
1172 if (!pte_present(*pte
))
1175 ret
= spurious_fault_check(error_code
, pte
);
1180 * Make sure we have permissions in PMD.
1181 * If not, then there's a bug in the page tables:
1183 ret
= spurious_fault_check(error_code
, (pte_t
*) pmd
);
1184 WARN_ONCE(!ret
, "PMD has incorrect permission bits\n");
1188 NOKPROBE_SYMBOL(spurious_fault
);
1190 int show_unhandled_signals
= 1;
1193 access_error(unsigned long error_code
, struct vm_area_struct
*vma
)
1195 /* This is only called for the current mm, so: */
1196 bool foreign
= false;
1199 * Read or write was blocked by protection keys. This is
1200 * always an unconditional error and can never result in
1201 * a follow-up action to resolve the fault, like a COW.
1203 if (error_code
& PF_PK
)
1207 * Make sure to check the VMA so that we do not perform
1208 * faults just to hit a PF_PK as soon as we fill in a
1211 if (!arch_vma_access_permitted(vma
, (error_code
& PF_WRITE
),
1212 (error_code
& PF_INSTR
), foreign
))
1215 if (error_code
& PF_WRITE
) {
1216 /* write, present and write, not present: */
1217 if (unlikely(!(vma
->vm_flags
& VM_WRITE
)))
1222 /* read, present: */
1223 if (unlikely(error_code
& PF_PROT
))
1226 /* read, not present: */
1227 if (unlikely(!(vma
->vm_flags
& (VM_READ
| VM_EXEC
| VM_WRITE
))))
1233 static int fault_in_kernel_space(unsigned long address
)
1235 return address
>= TASK_SIZE_MAX
;
1238 static inline bool smap_violation(int error_code
, struct pt_regs
*regs
)
1240 if (!IS_ENABLED(CONFIG_X86_SMAP
))
1243 if (!static_cpu_has(X86_FEATURE_SMAP
))
1246 if (error_code
& PF_USER
)
1249 if (!user_mode(regs
) && (regs
->flags
& X86_EFLAGS_AC
))
1256 * This routine handles page faults. It determines the address,
1257 * and the problem, and then passes it off to one of the appropriate
1260 static noinline
void
1261 __do_page_fault(struct pt_regs
*regs
, unsigned long error_code
,
1262 unsigned long address
)
1264 struct vm_area_struct
*vma
;
1265 struct task_struct
*tsk
;
1266 struct mm_struct
*mm
;
1267 int fault
, major
= 0;
1268 unsigned int flags
= FAULT_FLAG_ALLOW_RETRY
| FAULT_FLAG_KILLABLE
;
1275 * Detect and handle instructions that would cause a page fault for
1276 * both a tracked kernel page and a userspace page.
1278 if (kmemcheck_active(regs
))
1279 kmemcheck_hide(regs
);
1280 prefetchw(&mm
->mmap_sem
);
1282 if (unlikely(kmmio_fault(regs
, address
)))
1286 * We fault-in kernel-space virtual memory on-demand. The
1287 * 'reference' page table is init_mm.pgd.
1289 * NOTE! We MUST NOT take any locks for this case. We may
1290 * be in an interrupt or a critical region, and should
1291 * only copy the information from the master page table,
1294 * This verifies that the fault happens in kernel space
1295 * (error_code & 4) == 0, and that the fault was not a
1296 * protection error (error_code & 9) == 0.
1298 if (unlikely(fault_in_kernel_space(address
))) {
1299 if (!(error_code
& (PF_RSVD
| PF_USER
| PF_PROT
))) {
1300 if (vmalloc_fault(address
) >= 0)
1303 if (kmemcheck_fault(regs
, address
, error_code
))
1307 /* Can handle a stale RO->RW TLB: */
1308 if (spurious_fault(error_code
, address
))
1311 /* kprobes don't want to hook the spurious faults: */
1312 if (kprobes_fault(regs
))
1315 * Don't take the mm semaphore here. If we fixup a prefetch
1316 * fault we could otherwise deadlock:
1318 bad_area_nosemaphore(regs
, error_code
, address
, NULL
);
1323 /* kprobes don't want to hook the spurious faults: */
1324 if (unlikely(kprobes_fault(regs
)))
1327 if (unlikely(error_code
& PF_RSVD
))
1328 pgtable_bad(regs
, error_code
, address
);
1330 if (unlikely(smap_violation(error_code
, regs
))) {
1331 bad_area_nosemaphore(regs
, error_code
, address
, NULL
);
1336 * If we're in an interrupt, have no user context or are running
1337 * in a region with pagefaults disabled then we must not take the fault
1339 if (unlikely(faulthandler_disabled() || !mm
)) {
1340 bad_area_nosemaphore(regs
, error_code
, address
, NULL
);
1345 * It's safe to allow irq's after cr2 has been saved and the
1346 * vmalloc fault has been handled.
1348 * User-mode registers count as a user access even for any
1349 * potential system fault or CPU buglet:
1351 if (user_mode(regs
)) {
1353 error_code
|= PF_USER
;
1354 flags
|= FAULT_FLAG_USER
;
1356 if (regs
->flags
& X86_EFLAGS_IF
)
1360 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS
, 1, regs
, address
);
1362 if (error_code
& PF_WRITE
)
1363 flags
|= FAULT_FLAG_WRITE
;
1364 if (error_code
& PF_INSTR
)
1365 flags
|= FAULT_FLAG_INSTRUCTION
;
1368 * When running in the kernel we expect faults to occur only to
1369 * addresses in user space. All other faults represent errors in
1370 * the kernel and should generate an OOPS. Unfortunately, in the
1371 * case of an erroneous fault occurring in a code path which already
1372 * holds mmap_sem we will deadlock attempting to validate the fault
1373 * against the address space. Luckily the kernel only validly
1374 * references user space from well defined areas of code, which are
1375 * listed in the exceptions table.
1377 * As the vast majority of faults will be valid we will only perform
1378 * the source reference check when there is a possibility of a
1379 * deadlock. Attempt to lock the address space, if we cannot we then
1380 * validate the source. If this is invalid we can skip the address
1381 * space check, thus avoiding the deadlock:
1383 if (unlikely(!down_read_trylock(&mm
->mmap_sem
))) {
1384 if ((error_code
& PF_USER
) == 0 &&
1385 !search_exception_tables(regs
->ip
)) {
1386 bad_area_nosemaphore(regs
, error_code
, address
, NULL
);
1390 down_read(&mm
->mmap_sem
);
1393 * The above down_read_trylock() might have succeeded in
1394 * which case we'll have missed the might_sleep() from
1400 vma
= find_vma(mm
, address
);
1401 if (unlikely(!vma
)) {
1402 bad_area(regs
, error_code
, address
);
1405 if (likely(vma
->vm_start
<= address
))
1407 if (unlikely(!(vma
->vm_flags
& VM_GROWSDOWN
))) {
1408 bad_area(regs
, error_code
, address
);
1411 if (error_code
& PF_USER
) {
1413 * Accessing the stack below %sp is always a bug.
1414 * The large cushion allows instructions like enter
1415 * and pusha to work. ("enter $65535, $31" pushes
1416 * 32 pointers and then decrements %sp by 65535.)
1418 if (unlikely(address
+ 65536 + 32 * sizeof(unsigned long) < regs
->sp
)) {
1419 bad_area(regs
, error_code
, address
);
1423 if (unlikely(expand_stack(vma
, address
))) {
1424 bad_area(regs
, error_code
, address
);
1429 * Ok, we have a good vm_area for this memory access, so
1430 * we can handle it..
1433 if (unlikely(access_error(error_code
, vma
))) {
1434 bad_area_access_error(regs
, error_code
, address
, vma
);
1439 * If for any reason at all we couldn't handle the fault,
1440 * make sure we exit gracefully rather than endlessly redo
1441 * the fault. Since we never set FAULT_FLAG_RETRY_NOWAIT, if
1442 * we get VM_FAULT_RETRY back, the mmap_sem has been unlocked.
1444 fault
= handle_mm_fault(vma
, address
, flags
);
1445 major
|= fault
& VM_FAULT_MAJOR
;
1448 * If we need to retry the mmap_sem has already been released,
1449 * and if there is a fatal signal pending there is no guarantee
1450 * that we made any progress. Handle this case first.
1452 if (unlikely(fault
& VM_FAULT_RETRY
)) {
1453 /* Retry at most once */
1454 if (flags
& FAULT_FLAG_ALLOW_RETRY
) {
1455 flags
&= ~FAULT_FLAG_ALLOW_RETRY
;
1456 flags
|= FAULT_FLAG_TRIED
;
1457 if (!fatal_signal_pending(tsk
))
1461 /* User mode? Just return to handle the fatal exception */
1462 if (flags
& FAULT_FLAG_USER
)
1465 /* Not returning to user mode? Handle exceptions or die: */
1466 no_context(regs
, error_code
, address
, SIGBUS
, BUS_ADRERR
);
1470 pkey
= vma_pkey(vma
);
1471 up_read(&mm
->mmap_sem
);
1472 if (unlikely(fault
& VM_FAULT_ERROR
)) {
1473 mm_fault_error(regs
, error_code
, address
, &pkey
, fault
);
1478 * Major/minor page fault accounting. If any of the events
1479 * returned VM_FAULT_MAJOR, we account it as a major fault.
1483 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ
, 1, regs
, address
);
1486 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN
, 1, regs
, address
);
1489 check_v8086_mode(regs
, address
, tsk
);
1491 NOKPROBE_SYMBOL(__do_page_fault
);
1493 static nokprobe_inline
void
1494 trace_page_fault_entries(unsigned long address
, struct pt_regs
*regs
,
1495 unsigned long error_code
)
1497 if (user_mode(regs
))
1498 trace_page_fault_user(address
, regs
, error_code
);
1500 trace_page_fault_kernel(address
, regs
, error_code
);
1504 * We must have this function blacklisted from kprobes, tagged with notrace
1505 * and call read_cr2() before calling anything else. To avoid calling any
1506 * kind of tracing machinery before we've observed the CR2 value.
1508 * exception_{enter,exit}() contains all sorts of tracepoints.
1510 dotraplinkage
void notrace
1511 do_page_fault(struct pt_regs
*regs
, unsigned long error_code
)
1513 unsigned long address
= read_cr2(); /* Get the faulting address */
1514 enum ctx_state prev_state
;
1516 prev_state
= exception_enter();
1517 if (trace_pagefault_enabled())
1518 trace_page_fault_entries(address
, regs
, error_code
);
1520 __do_page_fault(regs
, error_code
, address
);
1521 exception_exit(prev_state
);
1523 NOKPROBE_SYMBOL(do_page_fault
);