2 * Copyright (C) 1995 Linus Torvalds
3 * Copyright (C) 2001, 2002 Andi Kleen, SuSE Labs.
4 * Copyright (C) 2008-2009, Red Hat Inc., Ingo Molnar
6 #include <linux/magic.h> /* STACK_END_MAGIC */
7 #include <linux/sched.h> /* test_thread_flag(), ... */
8 #include <linux/kdebug.h> /* oops_begin/end, ... */
9 #include <linux/module.h> /* search_exception_table */
10 #include <linux/bootmem.h> /* max_low_pfn */
11 #include <linux/kprobes.h> /* __kprobes, ... */
12 #include <linux/mmiotrace.h> /* kmmio_handler, ... */
13 #include <linux/perf_event.h> /* perf_sw_event */
14 #include <linux/hugetlb.h> /* hstate_index_to_shift */
15 #include <linux/prefetch.h> /* prefetchw */
16 #include <linux/context_tracking.h> /* exception_enter(), ... */
18 #include <asm/traps.h> /* dotraplinkage, ... */
19 #include <asm/pgalloc.h> /* pgd_*(), ... */
20 #include <asm/kmemcheck.h> /* kmemcheck_*(), ... */
21 #include <asm/fixmap.h> /* VSYSCALL_START */
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 inline int __kprobes
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 inline int __kprobes
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 __kprobes
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
))
296 * Did it hit the DOS screen memory VA from vm86 mode?
299 check_v8086_mode(struct pt_regs
*regs
, unsigned long address
,
300 struct task_struct
*tsk
)
304 if (!v8086_mode(regs
))
307 bit
= (address
- 0xA0000) >> PAGE_SHIFT
;
309 tsk
->thread
.screen_bitmap
|= 1 << bit
;
312 static bool low_pfn(unsigned long pfn
)
314 return pfn
< max_low_pfn
;
317 static void dump_pagetable(unsigned long address
)
319 pgd_t
*base
= __va(read_cr3());
320 pgd_t
*pgd
= &base
[pgd_index(address
)];
324 #ifdef CONFIG_X86_PAE
325 printk("*pdpt = %016Lx ", pgd_val(*pgd
));
326 if (!low_pfn(pgd_val(*pgd
) >> PAGE_SHIFT
) || !pgd_present(*pgd
))
329 pmd
= pmd_offset(pud_offset(pgd
, address
), address
);
330 printk(KERN_CONT
"*pde = %0*Lx ", sizeof(*pmd
) * 2, (u64
)pmd_val(*pmd
));
333 * We must not directly access the pte in the highpte
334 * case if the page table is located in highmem.
335 * And let's rather not kmap-atomic the pte, just in case
336 * it's allocated already:
338 if (!low_pfn(pmd_pfn(*pmd
)) || !pmd_present(*pmd
) || pmd_large(*pmd
))
341 pte
= pte_offset_kernel(pmd
, address
);
342 printk("*pte = %0*Lx ", sizeof(*pte
) * 2, (u64
)pte_val(*pte
));
347 #else /* CONFIG_X86_64: */
349 void vmalloc_sync_all(void)
351 sync_global_pgds(VMALLOC_START
& PGDIR_MASK
, VMALLOC_END
);
357 * Handle a fault on the vmalloc area
359 * This assumes no large pages in there.
361 static noinline __kprobes
int vmalloc_fault(unsigned long address
)
363 pgd_t
*pgd
, *pgd_ref
;
364 pud_t
*pud
, *pud_ref
;
365 pmd_t
*pmd
, *pmd_ref
;
366 pte_t
*pte
, *pte_ref
;
368 /* Make sure we are in vmalloc area: */
369 if (!(address
>= VMALLOC_START
&& address
< VMALLOC_END
))
372 WARN_ON_ONCE(in_nmi());
375 * Copy kernel mappings over when needed. This can also
376 * happen within a race in page table update. In the later
379 pgd
= pgd_offset(current
->active_mm
, address
);
380 pgd_ref
= pgd_offset_k(address
);
381 if (pgd_none(*pgd_ref
))
384 if (pgd_none(*pgd
)) {
385 set_pgd(pgd
, *pgd_ref
);
386 arch_flush_lazy_mmu_mode();
388 BUG_ON(pgd_page_vaddr(*pgd
) != pgd_page_vaddr(*pgd_ref
));
392 * Below here mismatches are bugs because these lower tables
396 pud
= pud_offset(pgd
, address
);
397 pud_ref
= pud_offset(pgd_ref
, address
);
398 if (pud_none(*pud_ref
))
401 if (pud_none(*pud
) || pud_page_vaddr(*pud
) != pud_page_vaddr(*pud_ref
))
404 pmd
= pmd_offset(pud
, address
);
405 pmd_ref
= pmd_offset(pud_ref
, address
);
406 if (pmd_none(*pmd_ref
))
409 if (pmd_none(*pmd
) || pmd_page(*pmd
) != pmd_page(*pmd_ref
))
412 pte_ref
= pte_offset_kernel(pmd_ref
, address
);
413 if (!pte_present(*pte_ref
))
416 pte
= pte_offset_kernel(pmd
, address
);
419 * Don't use pte_page here, because the mappings can point
420 * outside mem_map, and the NUMA hash lookup cannot handle
423 if (!pte_present(*pte
) || pte_pfn(*pte
) != pte_pfn(*pte_ref
))
429 #ifdef CONFIG_CPU_SUP_AMD
430 static const char errata93_warning
[] =
432 "******* Your BIOS seems to not contain a fix for K8 errata #93\n"
433 "******* Working around it, but it may cause SEGVs or burn power.\n"
434 "******* Please consider a BIOS update.\n"
435 "******* Disabling USB legacy in the BIOS may also help.\n";
439 * No vm86 mode in 64-bit mode:
442 check_v8086_mode(struct pt_regs
*regs
, unsigned long address
,
443 struct task_struct
*tsk
)
447 static int bad_address(void *p
)
451 return probe_kernel_address((unsigned long *)p
, dummy
);
454 static void dump_pagetable(unsigned long address
)
456 pgd_t
*base
= __va(read_cr3() & PHYSICAL_PAGE_MASK
);
457 pgd_t
*pgd
= base
+ pgd_index(address
);
462 if (bad_address(pgd
))
465 printk("PGD %lx ", pgd_val(*pgd
));
467 if (!pgd_present(*pgd
))
470 pud
= pud_offset(pgd
, address
);
471 if (bad_address(pud
))
474 printk("PUD %lx ", pud_val(*pud
));
475 if (!pud_present(*pud
) || pud_large(*pud
))
478 pmd
= pmd_offset(pud
, address
);
479 if (bad_address(pmd
))
482 printk("PMD %lx ", pmd_val(*pmd
));
483 if (!pmd_present(*pmd
) || pmd_large(*pmd
))
486 pte
= pte_offset_kernel(pmd
, address
);
487 if (bad_address(pte
))
490 printk("PTE %lx", pte_val(*pte
));
498 #endif /* CONFIG_X86_64 */
501 * Workaround for K8 erratum #93 & buggy BIOS.
503 * BIOS SMM functions are required to use a specific workaround
504 * to avoid corruption of the 64bit RIP register on C stepping K8.
506 * A lot of BIOS that didn't get tested properly miss this.
508 * The OS sees this as a page fault with the upper 32bits of RIP cleared.
509 * Try to work around it here.
511 * Note we only handle faults in kernel here.
512 * Does nothing on 32-bit.
514 static int is_errata93(struct pt_regs
*regs
, unsigned long address
)
516 #if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD)
517 if (boot_cpu_data
.x86_vendor
!= X86_VENDOR_AMD
518 || boot_cpu_data
.x86
!= 0xf)
521 if (address
!= regs
->ip
)
524 if ((address
>> 32) != 0)
527 address
|= 0xffffffffUL
<< 32;
528 if ((address
>= (u64
)_stext
&& address
<= (u64
)_etext
) ||
529 (address
>= MODULES_VADDR
&& address
<= MODULES_END
)) {
530 printk_once(errata93_warning
);
539 * Work around K8 erratum #100 K8 in compat mode occasionally jumps
540 * to illegal addresses >4GB.
542 * We catch this in the page fault handler because these addresses
543 * are not reachable. Just detect this case and return. Any code
544 * segment in LDT is compatibility mode.
546 static int is_errata100(struct pt_regs
*regs
, unsigned long address
)
549 if ((regs
->cs
== __USER32_CS
|| (regs
->cs
& (1<<2))) && (address
>> 32))
555 static int is_f00f_bug(struct pt_regs
*regs
, unsigned long address
)
557 #ifdef CONFIG_X86_F00F_BUG
561 * Pentium F0 0F C7 C8 bug workaround:
563 if (boot_cpu_has_bug(X86_BUG_F00F
)) {
564 nr
= (address
- idt_descr
.address
) >> 3;
567 do_invalid_op(regs
, 0);
575 static const char nx_warning
[] = KERN_CRIT
576 "kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n";
579 show_fault_oops(struct pt_regs
*regs
, unsigned long error_code
,
580 unsigned long address
)
582 if (!oops_may_print())
585 if (error_code
& PF_INSTR
) {
588 pte_t
*pte
= lookup_address(address
, &level
);
590 if (pte
&& pte_present(*pte
) && !pte_exec(*pte
))
591 printk(nx_warning
, from_kuid(&init_user_ns
, current_uid()));
594 printk(KERN_ALERT
"BUG: unable to handle kernel ");
595 if (address
< PAGE_SIZE
)
596 printk(KERN_CONT
"NULL pointer dereference");
598 printk(KERN_CONT
"paging request");
600 printk(KERN_CONT
" at %p\n", (void *) address
);
601 printk(KERN_ALERT
"IP:");
602 printk_address(regs
->ip
);
604 dump_pagetable(address
);
608 pgtable_bad(struct pt_regs
*regs
, unsigned long error_code
,
609 unsigned long address
)
611 struct task_struct
*tsk
;
615 flags
= oops_begin();
619 printk(KERN_ALERT
"%s: Corrupted page table at address %lx\n",
621 dump_pagetable(address
);
623 tsk
->thread
.cr2
= address
;
624 tsk
->thread
.trap_nr
= X86_TRAP_PF
;
625 tsk
->thread
.error_code
= error_code
;
627 if (__die("Bad pagetable", regs
, error_code
))
630 oops_end(flags
, regs
, sig
);
634 no_context(struct pt_regs
*regs
, unsigned long error_code
,
635 unsigned long address
, int signal
, int si_code
)
637 struct task_struct
*tsk
= current
;
638 unsigned long *stackend
;
642 /* Are we prepared to handle this kernel fault? */
643 if (fixup_exception(regs
)) {
645 * Any interrupt that takes a fault gets the fixup. This makes
646 * the below recursive fault logic only apply to a faults from
653 * Per the above we're !in_interrupt(), aka. task context.
655 * In this case we need to make sure we're not recursively
656 * faulting through the emulate_vsyscall() logic.
658 if (current_thread_info()->sig_on_uaccess_error
&& signal
) {
659 tsk
->thread
.trap_nr
= X86_TRAP_PF
;
660 tsk
->thread
.error_code
= error_code
| PF_USER
;
661 tsk
->thread
.cr2
= address
;
663 /* XXX: hwpoison faults will set the wrong code. */
664 force_sig_info_fault(signal
, si_code
, address
, tsk
, 0);
668 * Barring that, we can do the fixup and be happy.
676 * Valid to do another page fault here, because if this fault
677 * had been triggered by is_prefetch fixup_exception would have
682 * Hall of shame of CPU/BIOS bugs.
684 if (is_prefetch(regs
, error_code
, address
))
687 if (is_errata93(regs
, address
))
691 * Oops. The kernel tried to access some bad page. We'll have to
692 * terminate things with extreme prejudice:
694 flags
= oops_begin();
696 show_fault_oops(regs
, error_code
, address
);
698 stackend
= end_of_stack(tsk
);
699 if (tsk
!= &init_task
&& *stackend
!= STACK_END_MAGIC
)
700 printk(KERN_EMERG
"Thread overran stack, or stack corrupted\n");
702 tsk
->thread
.cr2
= address
;
703 tsk
->thread
.trap_nr
= X86_TRAP_PF
;
704 tsk
->thread
.error_code
= error_code
;
707 if (__die("Oops", regs
, error_code
))
710 /* Executive summary in case the body of the oops scrolled away */
711 printk(KERN_DEFAULT
"CR2: %016lx\n", address
);
713 oops_end(flags
, regs
, sig
);
717 * Print out info about fatal segfaults, if the show_unhandled_signals
721 show_signal_msg(struct pt_regs
*regs
, unsigned long error_code
,
722 unsigned long address
, struct task_struct
*tsk
)
724 if (!unhandled_signal(tsk
, SIGSEGV
))
727 if (!printk_ratelimit())
730 printk("%s%s[%d]: segfault at %lx ip %p sp %p error %lx",
731 task_pid_nr(tsk
) > 1 ? KERN_INFO
: KERN_EMERG
,
732 tsk
->comm
, task_pid_nr(tsk
), address
,
733 (void *)regs
->ip
, (void *)regs
->sp
, error_code
);
735 print_vma_addr(KERN_CONT
" in ", regs
->ip
);
737 printk(KERN_CONT
"\n");
741 __bad_area_nosemaphore(struct pt_regs
*regs
, unsigned long error_code
,
742 unsigned long address
, int si_code
)
744 struct task_struct
*tsk
= current
;
746 /* User mode accesses just cause a SIGSEGV */
747 if (error_code
& PF_USER
) {
749 * It's possible to have interrupts off here:
754 * Valid to do another page fault here because this one came
757 if (is_prefetch(regs
, error_code
, address
))
760 if (is_errata100(regs
, address
))
765 * Instruction fetch faults in the vsyscall page might need
768 if (unlikely((error_code
& PF_INSTR
) &&
769 ((address
& ~0xfff) == VSYSCALL_START
))) {
770 if (emulate_vsyscall(regs
, address
))
774 /* Kernel addresses are always protection faults: */
775 if (address
>= TASK_SIZE
)
776 error_code
|= PF_PROT
;
778 if (likely(show_unhandled_signals
))
779 show_signal_msg(regs
, error_code
, address
, tsk
);
781 tsk
->thread
.cr2
= address
;
782 tsk
->thread
.error_code
= error_code
;
783 tsk
->thread
.trap_nr
= X86_TRAP_PF
;
785 force_sig_info_fault(SIGSEGV
, si_code
, address
, tsk
, 0);
790 if (is_f00f_bug(regs
, address
))
793 no_context(regs
, error_code
, address
, SIGSEGV
, si_code
);
797 bad_area_nosemaphore(struct pt_regs
*regs
, unsigned long error_code
,
798 unsigned long address
)
800 __bad_area_nosemaphore(regs
, error_code
, address
, SEGV_MAPERR
);
804 __bad_area(struct pt_regs
*regs
, unsigned long error_code
,
805 unsigned long address
, int si_code
)
807 struct mm_struct
*mm
= current
->mm
;
810 * Something tried to access memory that isn't in our memory map..
811 * Fix it, but check if it's kernel or user first..
813 up_read(&mm
->mmap_sem
);
815 __bad_area_nosemaphore(regs
, error_code
, address
, si_code
);
819 bad_area(struct pt_regs
*regs
, unsigned long error_code
, unsigned long address
)
821 __bad_area(regs
, error_code
, address
, SEGV_MAPERR
);
825 bad_area_access_error(struct pt_regs
*regs
, unsigned long error_code
,
826 unsigned long address
)
828 __bad_area(regs
, error_code
, address
, SEGV_ACCERR
);
832 do_sigbus(struct pt_regs
*regs
, unsigned long error_code
, unsigned long address
,
835 struct task_struct
*tsk
= current
;
836 struct mm_struct
*mm
= tsk
->mm
;
837 int code
= BUS_ADRERR
;
839 up_read(&mm
->mmap_sem
);
841 /* Kernel mode? Handle exceptions or die: */
842 if (!(error_code
& PF_USER
)) {
843 no_context(regs
, error_code
, address
, SIGBUS
, BUS_ADRERR
);
847 /* User-space => ok to do another page fault: */
848 if (is_prefetch(regs
, error_code
, address
))
851 tsk
->thread
.cr2
= address
;
852 tsk
->thread
.error_code
= error_code
;
853 tsk
->thread
.trap_nr
= X86_TRAP_PF
;
855 #ifdef CONFIG_MEMORY_FAILURE
856 if (fault
& (VM_FAULT_HWPOISON
|VM_FAULT_HWPOISON_LARGE
)) {
858 "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
859 tsk
->comm
, tsk
->pid
, address
);
860 code
= BUS_MCEERR_AR
;
863 force_sig_info_fault(SIGBUS
, code
, address
, tsk
, fault
);
867 mm_fault_error(struct pt_regs
*regs
, unsigned long error_code
,
868 unsigned long address
, unsigned int fault
)
870 if (fatal_signal_pending(current
) && !(error_code
& PF_USER
)) {
871 up_read(¤t
->mm
->mmap_sem
);
872 no_context(regs
, error_code
, address
, 0, 0);
876 if (fault
& VM_FAULT_OOM
) {
877 /* Kernel mode? Handle exceptions or die: */
878 if (!(error_code
& PF_USER
)) {
879 up_read(¤t
->mm
->mmap_sem
);
880 no_context(regs
, error_code
, address
,
881 SIGSEGV
, SEGV_MAPERR
);
885 up_read(¤t
->mm
->mmap_sem
);
888 * We ran out of memory, call the OOM killer, and return the
889 * userspace (which will retry the fault, or kill us if we got
892 pagefault_out_of_memory();
894 if (fault
& (VM_FAULT_SIGBUS
|VM_FAULT_HWPOISON
|
895 VM_FAULT_HWPOISON_LARGE
))
896 do_sigbus(regs
, error_code
, address
, fault
);
902 static int spurious_fault_check(unsigned long error_code
, pte_t
*pte
)
904 if ((error_code
& PF_WRITE
) && !pte_write(*pte
))
907 if ((error_code
& PF_INSTR
) && !pte_exec(*pte
))
914 * Handle a spurious fault caused by a stale TLB entry.
916 * This allows us to lazily refresh the TLB when increasing the
917 * permissions of a kernel page (RO -> RW or NX -> X). Doing it
918 * eagerly is very expensive since that implies doing a full
919 * cross-processor TLB flush, even if no stale TLB entries exist
920 * on other processors.
922 * There are no security implications to leaving a stale TLB when
923 * increasing the permissions on a page.
925 static noinline __kprobes
int
926 spurious_fault(unsigned long error_code
, unsigned long address
)
934 /* Reserved-bit violation or user access to kernel space? */
935 if (error_code
& (PF_USER
| PF_RSVD
))
938 pgd
= init_mm
.pgd
+ pgd_index(address
);
939 if (!pgd_present(*pgd
))
942 pud
= pud_offset(pgd
, address
);
943 if (!pud_present(*pud
))
947 return spurious_fault_check(error_code
, (pte_t
*) pud
);
949 pmd
= pmd_offset(pud
, address
);
950 if (!pmd_present(*pmd
))
954 return spurious_fault_check(error_code
, (pte_t
*) pmd
);
956 pte
= pte_offset_kernel(pmd
, address
);
957 if (!pte_present(*pte
))
960 ret
= spurious_fault_check(error_code
, pte
);
965 * Make sure we have permissions in PMD.
966 * If not, then there's a bug in the page tables:
968 ret
= spurious_fault_check(error_code
, (pte_t
*) pmd
);
969 WARN_ONCE(!ret
, "PMD has incorrect permission bits\n");
974 int show_unhandled_signals
= 1;
977 access_error(unsigned long error_code
, struct vm_area_struct
*vma
)
979 if (error_code
& PF_WRITE
) {
980 /* write, present and write, not present: */
981 if (unlikely(!(vma
->vm_flags
& VM_WRITE
)))
987 if (unlikely(error_code
& PF_PROT
))
990 /* read, not present: */
991 if (unlikely(!(vma
->vm_flags
& (VM_READ
| VM_EXEC
| VM_WRITE
))))
997 static int fault_in_kernel_space(unsigned long address
)
999 return address
>= TASK_SIZE_MAX
;
1002 static inline bool smap_violation(int error_code
, struct pt_regs
*regs
)
1004 if (error_code
& PF_USER
)
1007 if (!user_mode_vm(regs
) && (regs
->flags
& X86_EFLAGS_AC
))
1014 * This routine handles page faults. It determines the address,
1015 * and the problem, and then passes it off to one of the appropriate
1018 static void __kprobes
1019 __do_page_fault(struct pt_regs
*regs
, unsigned long error_code
)
1021 struct vm_area_struct
*vma
;
1022 struct task_struct
*tsk
;
1023 unsigned long address
;
1024 struct mm_struct
*mm
;
1026 unsigned int flags
= FAULT_FLAG_ALLOW_RETRY
| FAULT_FLAG_KILLABLE
;
1031 /* Get the faulting address: */
1032 address
= read_cr2();
1035 * Detect and handle instructions that would cause a page fault for
1036 * both a tracked kernel page and a userspace page.
1038 if (kmemcheck_active(regs
))
1039 kmemcheck_hide(regs
);
1040 prefetchw(&mm
->mmap_sem
);
1042 if (unlikely(kmmio_fault(regs
, address
)))
1046 * We fault-in kernel-space virtual memory on-demand. The
1047 * 'reference' page table is init_mm.pgd.
1049 * NOTE! We MUST NOT take any locks for this case. We may
1050 * be in an interrupt or a critical region, and should
1051 * only copy the information from the master page table,
1054 * This verifies that the fault happens in kernel space
1055 * (error_code & 4) == 0, and that the fault was not a
1056 * protection error (error_code & 9) == 0.
1058 if (unlikely(fault_in_kernel_space(address
))) {
1059 if (!(error_code
& (PF_RSVD
| PF_USER
| PF_PROT
))) {
1060 if (vmalloc_fault(address
) >= 0)
1063 if (kmemcheck_fault(regs
, address
, error_code
))
1067 /* Can handle a stale RO->RW TLB: */
1068 if (spurious_fault(error_code
, address
))
1071 /* kprobes don't want to hook the spurious faults: */
1072 if (kprobes_fault(regs
))
1075 * Don't take the mm semaphore here. If we fixup a prefetch
1076 * fault we could otherwise deadlock:
1078 bad_area_nosemaphore(regs
, error_code
, address
);
1083 /* kprobes don't want to hook the spurious faults: */
1084 if (unlikely(kprobes_fault(regs
)))
1087 if (unlikely(error_code
& PF_RSVD
))
1088 pgtable_bad(regs
, error_code
, address
);
1090 if (static_cpu_has(X86_FEATURE_SMAP
)) {
1091 if (unlikely(smap_violation(error_code
, regs
))) {
1092 bad_area_nosemaphore(regs
, error_code
, address
);
1098 * If we're in an interrupt, have no user context or are running
1099 * in an atomic region then we must not take the fault:
1101 if (unlikely(in_atomic() || !mm
)) {
1102 bad_area_nosemaphore(regs
, error_code
, address
);
1107 * It's safe to allow irq's after cr2 has been saved and the
1108 * vmalloc fault has been handled.
1110 * User-mode registers count as a user access even for any
1111 * potential system fault or CPU buglet:
1113 if (user_mode_vm(regs
)) {
1115 error_code
|= PF_USER
;
1116 flags
|= FAULT_FLAG_USER
;
1118 if (regs
->flags
& X86_EFLAGS_IF
)
1122 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS
, 1, regs
, address
);
1124 if (error_code
& PF_WRITE
)
1125 flags
|= FAULT_FLAG_WRITE
;
1128 * When running in the kernel we expect faults to occur only to
1129 * addresses in user space. All other faults represent errors in
1130 * the kernel and should generate an OOPS. Unfortunately, in the
1131 * case of an erroneous fault occurring in a code path which already
1132 * holds mmap_sem we will deadlock attempting to validate the fault
1133 * against the address space. Luckily the kernel only validly
1134 * references user space from well defined areas of code, which are
1135 * listed in the exceptions table.
1137 * As the vast majority of faults will be valid we will only perform
1138 * the source reference check when there is a possibility of a
1139 * deadlock. Attempt to lock the address space, if we cannot we then
1140 * validate the source. If this is invalid we can skip the address
1141 * space check, thus avoiding the deadlock:
1143 if (unlikely(!down_read_trylock(&mm
->mmap_sem
))) {
1144 if ((error_code
& PF_USER
) == 0 &&
1145 !search_exception_tables(regs
->ip
)) {
1146 bad_area_nosemaphore(regs
, error_code
, address
);
1150 down_read(&mm
->mmap_sem
);
1153 * The above down_read_trylock() might have succeeded in
1154 * which case we'll have missed the might_sleep() from
1160 vma
= find_vma(mm
, address
);
1161 if (unlikely(!vma
)) {
1162 bad_area(regs
, error_code
, address
);
1165 if (likely(vma
->vm_start
<= address
))
1167 if (unlikely(!(vma
->vm_flags
& VM_GROWSDOWN
))) {
1168 bad_area(regs
, error_code
, address
);
1171 if (error_code
& PF_USER
) {
1173 * Accessing the stack below %sp is always a bug.
1174 * The large cushion allows instructions like enter
1175 * and pusha to work. ("enter $65535, $31" pushes
1176 * 32 pointers and then decrements %sp by 65535.)
1178 if (unlikely(address
+ 65536 + 32 * sizeof(unsigned long) < regs
->sp
)) {
1179 bad_area(regs
, error_code
, address
);
1183 if (unlikely(expand_stack(vma
, address
))) {
1184 bad_area(regs
, error_code
, address
);
1189 * Ok, we have a good vm_area for this memory access, so
1190 * we can handle it..
1193 if (unlikely(access_error(error_code
, vma
))) {
1194 bad_area_access_error(regs
, error_code
, address
);
1199 * If for any reason at all we couldn't handle the fault,
1200 * make sure we exit gracefully rather than endlessly redo
1203 fault
= handle_mm_fault(mm
, vma
, address
, flags
);
1206 * If we need to retry but a fatal signal is pending, handle the
1207 * signal first. We do not need to release the mmap_sem because it
1208 * would already be released in __lock_page_or_retry in mm/filemap.c.
1210 if (unlikely((fault
& VM_FAULT_RETRY
) && fatal_signal_pending(current
)))
1213 if (unlikely(fault
& VM_FAULT_ERROR
)) {
1214 mm_fault_error(regs
, error_code
, address
, fault
);
1219 * Major/minor page fault accounting is only done on the
1220 * initial attempt. If we go through a retry, it is extremely
1221 * likely that the page will be found in page cache at that point.
1223 if (flags
& FAULT_FLAG_ALLOW_RETRY
) {
1224 if (fault
& VM_FAULT_MAJOR
) {
1226 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ
, 1,
1230 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN
, 1,
1233 if (fault
& VM_FAULT_RETRY
) {
1234 /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
1236 flags
&= ~FAULT_FLAG_ALLOW_RETRY
;
1237 flags
|= FAULT_FLAG_TRIED
;
1242 check_v8086_mode(regs
, address
, tsk
);
1244 up_read(&mm
->mmap_sem
);
1247 dotraplinkage
void __kprobes
1248 do_page_fault(struct pt_regs
*regs
, unsigned long error_code
)
1250 enum ctx_state prev_state
;
1252 prev_state
= exception_enter();
1253 __do_page_fault(regs
, error_code
);
1254 exception_exit(prev_state
);
1257 static void trace_page_fault_entries(struct pt_regs
*regs
,
1258 unsigned long error_code
)
1260 if (user_mode(regs
))
1261 trace_page_fault_user(read_cr2(), regs
, error_code
);
1263 trace_page_fault_kernel(read_cr2(), regs
, error_code
);
1266 dotraplinkage
void __kprobes
1267 trace_do_page_fault(struct pt_regs
*regs
, unsigned long error_code
)
1269 enum ctx_state prev_state
;
1271 prev_state
= exception_enter();
1272 trace_page_fault_entries(regs
, error_code
);
1273 __do_page_fault(regs
, error_code
);
1274 exception_exit(prev_state
);