Loading...
1/*
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
5 */
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
17#include <asm/traps.h> /* dotraplinkage, ... */
18#include <asm/pgalloc.h> /* pgd_*(), ... */
19#include <asm/kmemcheck.h> /* kmemcheck_*(), ... */
20#include <asm/vsyscall.h>
21
22/*
23 * Page fault error code bits:
24 *
25 * bit 0 == 0: no page found 1: protection fault
26 * bit 1 == 0: read access 1: write access
27 * bit 2 == 0: kernel-mode access 1: user-mode access
28 * bit 3 == 1: use of reserved bit detected
29 * bit 4 == 1: fault was an instruction fetch
30 */
31enum x86_pf_error_code {
32
33 PF_PROT = 1 << 0,
34 PF_WRITE = 1 << 1,
35 PF_USER = 1 << 2,
36 PF_RSVD = 1 << 3,
37 PF_INSTR = 1 << 4,
38};
39
40/*
41 * Returns 0 if mmiotrace is disabled, or if the fault is not
42 * handled by mmiotrace:
43 */
44static inline int __kprobes
45kmmio_fault(struct pt_regs *regs, unsigned long addr)
46{
47 if (unlikely(is_kmmio_active()))
48 if (kmmio_handler(regs, addr) == 1)
49 return -1;
50 return 0;
51}
52
53static inline int __kprobes notify_page_fault(struct pt_regs *regs)
54{
55 int ret = 0;
56
57 /* kprobe_running() needs smp_processor_id() */
58 if (kprobes_built_in() && !user_mode_vm(regs)) {
59 preempt_disable();
60 if (kprobe_running() && kprobe_fault_handler(regs, 14))
61 ret = 1;
62 preempt_enable();
63 }
64
65 return ret;
66}
67
68/*
69 * Prefetch quirks:
70 *
71 * 32-bit mode:
72 *
73 * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
74 * Check that here and ignore it.
75 *
76 * 64-bit mode:
77 *
78 * Sometimes the CPU reports invalid exceptions on prefetch.
79 * Check that here and ignore it.
80 *
81 * Opcode checker based on code by Richard Brunner.
82 */
83static inline int
84check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr,
85 unsigned char opcode, int *prefetch)
86{
87 unsigned char instr_hi = opcode & 0xf0;
88 unsigned char instr_lo = opcode & 0x0f;
89
90 switch (instr_hi) {
91 case 0x20:
92 case 0x30:
93 /*
94 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes.
95 * In X86_64 long mode, the CPU will signal invalid
96 * opcode if some of these prefixes are present so
97 * X86_64 will never get here anyway
98 */
99 return ((instr_lo & 7) == 0x6);
100#ifdef CONFIG_X86_64
101 case 0x40:
102 /*
103 * In AMD64 long mode 0x40..0x4F are valid REX prefixes
104 * Need to figure out under what instruction mode the
105 * instruction was issued. Could check the LDT for lm,
106 * but for now it's good enough to assume that long
107 * mode only uses well known segments or kernel.
108 */
109 return (!user_mode(regs) || user_64bit_mode(regs));
110#endif
111 case 0x60:
112 /* 0x64 thru 0x67 are valid prefixes in all modes. */
113 return (instr_lo & 0xC) == 0x4;
114 case 0xF0:
115 /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */
116 return !instr_lo || (instr_lo>>1) == 1;
117 case 0x00:
118 /* Prefetch instruction is 0x0F0D or 0x0F18 */
119 if (probe_kernel_address(instr, opcode))
120 return 0;
121
122 *prefetch = (instr_lo == 0xF) &&
123 (opcode == 0x0D || opcode == 0x18);
124 return 0;
125 default:
126 return 0;
127 }
128}
129
130static int
131is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
132{
133 unsigned char *max_instr;
134 unsigned char *instr;
135 int prefetch = 0;
136
137 /*
138 * If it was a exec (instruction fetch) fault on NX page, then
139 * do not ignore the fault:
140 */
141 if (error_code & PF_INSTR)
142 return 0;
143
144 instr = (void *)convert_ip_to_linear(current, regs);
145 max_instr = instr + 15;
146
147 if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE)
148 return 0;
149
150 while (instr < max_instr) {
151 unsigned char opcode;
152
153 if (probe_kernel_address(instr, opcode))
154 break;
155
156 instr++;
157
158 if (!check_prefetch_opcode(regs, instr, opcode, &prefetch))
159 break;
160 }
161 return prefetch;
162}
163
164static void
165force_sig_info_fault(int si_signo, int si_code, unsigned long address,
166 struct task_struct *tsk, int fault)
167{
168 unsigned lsb = 0;
169 siginfo_t info;
170
171 info.si_signo = si_signo;
172 info.si_errno = 0;
173 info.si_code = si_code;
174 info.si_addr = (void __user *)address;
175 if (fault & VM_FAULT_HWPOISON_LARGE)
176 lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
177 if (fault & VM_FAULT_HWPOISON)
178 lsb = PAGE_SHIFT;
179 info.si_addr_lsb = lsb;
180
181 force_sig_info(si_signo, &info, tsk);
182}
183
184DEFINE_SPINLOCK(pgd_lock);
185LIST_HEAD(pgd_list);
186
187#ifdef CONFIG_X86_32
188static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
189{
190 unsigned index = pgd_index(address);
191 pgd_t *pgd_k;
192 pud_t *pud, *pud_k;
193 pmd_t *pmd, *pmd_k;
194
195 pgd += index;
196 pgd_k = init_mm.pgd + index;
197
198 if (!pgd_present(*pgd_k))
199 return NULL;
200
201 /*
202 * set_pgd(pgd, *pgd_k); here would be useless on PAE
203 * and redundant with the set_pmd() on non-PAE. As would
204 * set_pud.
205 */
206 pud = pud_offset(pgd, address);
207 pud_k = pud_offset(pgd_k, address);
208 if (!pud_present(*pud_k))
209 return NULL;
210
211 pmd = pmd_offset(pud, address);
212 pmd_k = pmd_offset(pud_k, address);
213 if (!pmd_present(*pmd_k))
214 return NULL;
215
216 if (!pmd_present(*pmd))
217 set_pmd(pmd, *pmd_k);
218 else
219 BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k));
220
221 return pmd_k;
222}
223
224void vmalloc_sync_all(void)
225{
226 unsigned long address;
227
228 if (SHARED_KERNEL_PMD)
229 return;
230
231 for (address = VMALLOC_START & PMD_MASK;
232 address >= TASK_SIZE && address < FIXADDR_TOP;
233 address += PMD_SIZE) {
234 struct page *page;
235
236 spin_lock(&pgd_lock);
237 list_for_each_entry(page, &pgd_list, lru) {
238 spinlock_t *pgt_lock;
239 pmd_t *ret;
240
241 /* the pgt_lock only for Xen */
242 pgt_lock = &pgd_page_get_mm(page)->page_table_lock;
243
244 spin_lock(pgt_lock);
245 ret = vmalloc_sync_one(page_address(page), address);
246 spin_unlock(pgt_lock);
247
248 if (!ret)
249 break;
250 }
251 spin_unlock(&pgd_lock);
252 }
253}
254
255/*
256 * 32-bit:
257 *
258 * Handle a fault on the vmalloc or module mapping area
259 */
260static noinline __kprobes int vmalloc_fault(unsigned long address)
261{
262 unsigned long pgd_paddr;
263 pmd_t *pmd_k;
264 pte_t *pte_k;
265
266 /* Make sure we are in vmalloc area: */
267 if (!(address >= VMALLOC_START && address < VMALLOC_END))
268 return -1;
269
270 WARN_ON_ONCE(in_nmi());
271
272 /*
273 * Synchronize this task's top level page-table
274 * with the 'reference' page table.
275 *
276 * Do _not_ use "current" here. We might be inside
277 * an interrupt in the middle of a task switch..
278 */
279 pgd_paddr = read_cr3();
280 pmd_k = vmalloc_sync_one(__va(pgd_paddr), address);
281 if (!pmd_k)
282 return -1;
283
284 pte_k = pte_offset_kernel(pmd_k, address);
285 if (!pte_present(*pte_k))
286 return -1;
287
288 return 0;
289}
290
291/*
292 * Did it hit the DOS screen memory VA from vm86 mode?
293 */
294static inline void
295check_v8086_mode(struct pt_regs *regs, unsigned long address,
296 struct task_struct *tsk)
297{
298 unsigned long bit;
299
300 if (!v8086_mode(regs))
301 return;
302
303 bit = (address - 0xA0000) >> PAGE_SHIFT;
304 if (bit < 32)
305 tsk->thread.screen_bitmap |= 1 << bit;
306}
307
308static bool low_pfn(unsigned long pfn)
309{
310 return pfn < max_low_pfn;
311}
312
313static void dump_pagetable(unsigned long address)
314{
315 pgd_t *base = __va(read_cr3());
316 pgd_t *pgd = &base[pgd_index(address)];
317 pmd_t *pmd;
318 pte_t *pte;
319
320#ifdef CONFIG_X86_PAE
321 printk("*pdpt = %016Lx ", pgd_val(*pgd));
322 if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd))
323 goto out;
324#endif
325 pmd = pmd_offset(pud_offset(pgd, address), address);
326 printk(KERN_CONT "*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd));
327
328 /*
329 * We must not directly access the pte in the highpte
330 * case if the page table is located in highmem.
331 * And let's rather not kmap-atomic the pte, just in case
332 * it's allocated already:
333 */
334 if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_large(*pmd))
335 goto out;
336
337 pte = pte_offset_kernel(pmd, address);
338 printk("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte));
339out:
340 printk("\n");
341}
342
343#else /* CONFIG_X86_64: */
344
345void vmalloc_sync_all(void)
346{
347 sync_global_pgds(VMALLOC_START & PGDIR_MASK, VMALLOC_END);
348}
349
350/*
351 * 64-bit:
352 *
353 * Handle a fault on the vmalloc area
354 *
355 * This assumes no large pages in there.
356 */
357static noinline __kprobes int vmalloc_fault(unsigned long address)
358{
359 pgd_t *pgd, *pgd_ref;
360 pud_t *pud, *pud_ref;
361 pmd_t *pmd, *pmd_ref;
362 pte_t *pte, *pte_ref;
363
364 /* Make sure we are in vmalloc area: */
365 if (!(address >= VMALLOC_START && address < VMALLOC_END))
366 return -1;
367
368 WARN_ON_ONCE(in_nmi());
369
370 /*
371 * Copy kernel mappings over when needed. This can also
372 * happen within a race in page table update. In the later
373 * case just flush:
374 */
375 pgd = pgd_offset(current->active_mm, address);
376 pgd_ref = pgd_offset_k(address);
377 if (pgd_none(*pgd_ref))
378 return -1;
379
380 if (pgd_none(*pgd))
381 set_pgd(pgd, *pgd_ref);
382 else
383 BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref));
384
385 /*
386 * Below here mismatches are bugs because these lower tables
387 * are shared:
388 */
389
390 pud = pud_offset(pgd, address);
391 pud_ref = pud_offset(pgd_ref, address);
392 if (pud_none(*pud_ref))
393 return -1;
394
395 if (pud_none(*pud) || pud_page_vaddr(*pud) != pud_page_vaddr(*pud_ref))
396 BUG();
397
398 pmd = pmd_offset(pud, address);
399 pmd_ref = pmd_offset(pud_ref, address);
400 if (pmd_none(*pmd_ref))
401 return -1;
402
403 if (pmd_none(*pmd) || pmd_page(*pmd) != pmd_page(*pmd_ref))
404 BUG();
405
406 pte_ref = pte_offset_kernel(pmd_ref, address);
407 if (!pte_present(*pte_ref))
408 return -1;
409
410 pte = pte_offset_kernel(pmd, address);
411
412 /*
413 * Don't use pte_page here, because the mappings can point
414 * outside mem_map, and the NUMA hash lookup cannot handle
415 * that:
416 */
417 if (!pte_present(*pte) || pte_pfn(*pte) != pte_pfn(*pte_ref))
418 BUG();
419
420 return 0;
421}
422
423static const char errata93_warning[] =
424KERN_ERR
425"******* Your BIOS seems to not contain a fix for K8 errata #93\n"
426"******* Working around it, but it may cause SEGVs or burn power.\n"
427"******* Please consider a BIOS update.\n"
428"******* Disabling USB legacy in the BIOS may also help.\n";
429
430/*
431 * No vm86 mode in 64-bit mode:
432 */
433static inline void
434check_v8086_mode(struct pt_regs *regs, unsigned long address,
435 struct task_struct *tsk)
436{
437}
438
439static int bad_address(void *p)
440{
441 unsigned long dummy;
442
443 return probe_kernel_address((unsigned long *)p, dummy);
444}
445
446static void dump_pagetable(unsigned long address)
447{
448 pgd_t *base = __va(read_cr3() & PHYSICAL_PAGE_MASK);
449 pgd_t *pgd = base + pgd_index(address);
450 pud_t *pud;
451 pmd_t *pmd;
452 pte_t *pte;
453
454 if (bad_address(pgd))
455 goto bad;
456
457 printk("PGD %lx ", pgd_val(*pgd));
458
459 if (!pgd_present(*pgd))
460 goto out;
461
462 pud = pud_offset(pgd, address);
463 if (bad_address(pud))
464 goto bad;
465
466 printk("PUD %lx ", pud_val(*pud));
467 if (!pud_present(*pud) || pud_large(*pud))
468 goto out;
469
470 pmd = pmd_offset(pud, address);
471 if (bad_address(pmd))
472 goto bad;
473
474 printk("PMD %lx ", pmd_val(*pmd));
475 if (!pmd_present(*pmd) || pmd_large(*pmd))
476 goto out;
477
478 pte = pte_offset_kernel(pmd, address);
479 if (bad_address(pte))
480 goto bad;
481
482 printk("PTE %lx", pte_val(*pte));
483out:
484 printk("\n");
485 return;
486bad:
487 printk("BAD\n");
488}
489
490#endif /* CONFIG_X86_64 */
491
492/*
493 * Workaround for K8 erratum #93 & buggy BIOS.
494 *
495 * BIOS SMM functions are required to use a specific workaround
496 * to avoid corruption of the 64bit RIP register on C stepping K8.
497 *
498 * A lot of BIOS that didn't get tested properly miss this.
499 *
500 * The OS sees this as a page fault with the upper 32bits of RIP cleared.
501 * Try to work around it here.
502 *
503 * Note we only handle faults in kernel here.
504 * Does nothing on 32-bit.
505 */
506static int is_errata93(struct pt_regs *regs, unsigned long address)
507{
508#ifdef CONFIG_X86_64
509 if (address != regs->ip)
510 return 0;
511
512 if ((address >> 32) != 0)
513 return 0;
514
515 address |= 0xffffffffUL << 32;
516 if ((address >= (u64)_stext && address <= (u64)_etext) ||
517 (address >= MODULES_VADDR && address <= MODULES_END)) {
518 printk_once(errata93_warning);
519 regs->ip = address;
520 return 1;
521 }
522#endif
523 return 0;
524}
525
526/*
527 * Work around K8 erratum #100 K8 in compat mode occasionally jumps
528 * to illegal addresses >4GB.
529 *
530 * We catch this in the page fault handler because these addresses
531 * are not reachable. Just detect this case and return. Any code
532 * segment in LDT is compatibility mode.
533 */
534static int is_errata100(struct pt_regs *regs, unsigned long address)
535{
536#ifdef CONFIG_X86_64
537 if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32))
538 return 1;
539#endif
540 return 0;
541}
542
543static int is_f00f_bug(struct pt_regs *regs, unsigned long address)
544{
545#ifdef CONFIG_X86_F00F_BUG
546 unsigned long nr;
547
548 /*
549 * Pentium F0 0F C7 C8 bug workaround:
550 */
551 if (boot_cpu_data.f00f_bug) {
552 nr = (address - idt_descr.address) >> 3;
553
554 if (nr == 6) {
555 do_invalid_op(regs, 0);
556 return 1;
557 }
558 }
559#endif
560 return 0;
561}
562
563static const char nx_warning[] = KERN_CRIT
564"kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n";
565
566static void
567show_fault_oops(struct pt_regs *regs, unsigned long error_code,
568 unsigned long address)
569{
570 if (!oops_may_print())
571 return;
572
573 if (error_code & PF_INSTR) {
574 unsigned int level;
575
576 pte_t *pte = lookup_address(address, &level);
577
578 if (pte && pte_present(*pte) && !pte_exec(*pte))
579 printk(nx_warning, current_uid());
580 }
581
582 printk(KERN_ALERT "BUG: unable to handle kernel ");
583 if (address < PAGE_SIZE)
584 printk(KERN_CONT "NULL pointer dereference");
585 else
586 printk(KERN_CONT "paging request");
587
588 printk(KERN_CONT " at %p\n", (void *) address);
589 printk(KERN_ALERT "IP:");
590 printk_address(regs->ip, 1);
591
592 dump_pagetable(address);
593}
594
595static noinline void
596pgtable_bad(struct pt_regs *regs, unsigned long error_code,
597 unsigned long address)
598{
599 struct task_struct *tsk;
600 unsigned long flags;
601 int sig;
602
603 flags = oops_begin();
604 tsk = current;
605 sig = SIGKILL;
606
607 printk(KERN_ALERT "%s: Corrupted page table at address %lx\n",
608 tsk->comm, address);
609 dump_pagetable(address);
610
611 tsk->thread.cr2 = address;
612 tsk->thread.trap_no = 14;
613 tsk->thread.error_code = error_code;
614
615 if (__die("Bad pagetable", regs, error_code))
616 sig = 0;
617
618 oops_end(flags, regs, sig);
619}
620
621static noinline void
622no_context(struct pt_regs *regs, unsigned long error_code,
623 unsigned long address)
624{
625 struct task_struct *tsk = current;
626 unsigned long *stackend;
627 unsigned long flags;
628 int sig;
629
630 /* Are we prepared to handle this kernel fault? */
631 if (fixup_exception(regs))
632 return;
633
634 /*
635 * 32-bit:
636 *
637 * Valid to do another page fault here, because if this fault
638 * had been triggered by is_prefetch fixup_exception would have
639 * handled it.
640 *
641 * 64-bit:
642 *
643 * Hall of shame of CPU/BIOS bugs.
644 */
645 if (is_prefetch(regs, error_code, address))
646 return;
647
648 if (is_errata93(regs, address))
649 return;
650
651 /*
652 * Oops. The kernel tried to access some bad page. We'll have to
653 * terminate things with extreme prejudice:
654 */
655 flags = oops_begin();
656
657 show_fault_oops(regs, error_code, address);
658
659 stackend = end_of_stack(tsk);
660 if (tsk != &init_task && *stackend != STACK_END_MAGIC)
661 printk(KERN_ALERT "Thread overran stack, or stack corrupted\n");
662
663 tsk->thread.cr2 = address;
664 tsk->thread.trap_no = 14;
665 tsk->thread.error_code = error_code;
666
667 sig = SIGKILL;
668 if (__die("Oops", regs, error_code))
669 sig = 0;
670
671 /* Executive summary in case the body of the oops scrolled away */
672 printk(KERN_EMERG "CR2: %016lx\n", address);
673
674 oops_end(flags, regs, sig);
675}
676
677/*
678 * Print out info about fatal segfaults, if the show_unhandled_signals
679 * sysctl is set:
680 */
681static inline void
682show_signal_msg(struct pt_regs *regs, unsigned long error_code,
683 unsigned long address, struct task_struct *tsk)
684{
685 if (!unhandled_signal(tsk, SIGSEGV))
686 return;
687
688 if (!printk_ratelimit())
689 return;
690
691 printk("%s%s[%d]: segfault at %lx ip %p sp %p error %lx",
692 task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
693 tsk->comm, task_pid_nr(tsk), address,
694 (void *)regs->ip, (void *)regs->sp, error_code);
695
696 print_vma_addr(KERN_CONT " in ", regs->ip);
697
698 printk(KERN_CONT "\n");
699}
700
701static void
702__bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
703 unsigned long address, int si_code)
704{
705 struct task_struct *tsk = current;
706
707 /* User mode accesses just cause a SIGSEGV */
708 if (error_code & PF_USER) {
709 /*
710 * It's possible to have interrupts off here:
711 */
712 local_irq_enable();
713
714 /*
715 * Valid to do another page fault here because this one came
716 * from user space:
717 */
718 if (is_prefetch(regs, error_code, address))
719 return;
720
721 if (is_errata100(regs, address))
722 return;
723
724#ifdef CONFIG_X86_64
725 /*
726 * Instruction fetch faults in the vsyscall page might need
727 * emulation.
728 */
729 if (unlikely((error_code & PF_INSTR) &&
730 ((address & ~0xfff) == VSYSCALL_START))) {
731 if (emulate_vsyscall(regs, address))
732 return;
733 }
734#endif
735
736 if (unlikely(show_unhandled_signals))
737 show_signal_msg(regs, error_code, address, tsk);
738
739 /* Kernel addresses are always protection faults: */
740 tsk->thread.cr2 = address;
741 tsk->thread.error_code = error_code | (address >= TASK_SIZE);
742 tsk->thread.trap_no = 14;
743
744 force_sig_info_fault(SIGSEGV, si_code, address, tsk, 0);
745
746 return;
747 }
748
749 if (is_f00f_bug(regs, address))
750 return;
751
752 no_context(regs, error_code, address);
753}
754
755static noinline void
756bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
757 unsigned long address)
758{
759 __bad_area_nosemaphore(regs, error_code, address, SEGV_MAPERR);
760}
761
762static void
763__bad_area(struct pt_regs *regs, unsigned long error_code,
764 unsigned long address, int si_code)
765{
766 struct mm_struct *mm = current->mm;
767
768 /*
769 * Something tried to access memory that isn't in our memory map..
770 * Fix it, but check if it's kernel or user first..
771 */
772 up_read(&mm->mmap_sem);
773
774 __bad_area_nosemaphore(regs, error_code, address, si_code);
775}
776
777static noinline void
778bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address)
779{
780 __bad_area(regs, error_code, address, SEGV_MAPERR);
781}
782
783static noinline void
784bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
785 unsigned long address)
786{
787 __bad_area(regs, error_code, address, SEGV_ACCERR);
788}
789
790/* TODO: fixup for "mm-invoke-oom-killer-from-page-fault.patch" */
791static void
792out_of_memory(struct pt_regs *regs, unsigned long error_code,
793 unsigned long address)
794{
795 /*
796 * We ran out of memory, call the OOM killer, and return the userspace
797 * (which will retry the fault, or kill us if we got oom-killed):
798 */
799 up_read(¤t->mm->mmap_sem);
800
801 pagefault_out_of_memory();
802}
803
804static void
805do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
806 unsigned int fault)
807{
808 struct task_struct *tsk = current;
809 struct mm_struct *mm = tsk->mm;
810 int code = BUS_ADRERR;
811
812 up_read(&mm->mmap_sem);
813
814 /* Kernel mode? Handle exceptions or die: */
815 if (!(error_code & PF_USER)) {
816 no_context(regs, error_code, address);
817 return;
818 }
819
820 /* User-space => ok to do another page fault: */
821 if (is_prefetch(regs, error_code, address))
822 return;
823
824 tsk->thread.cr2 = address;
825 tsk->thread.error_code = error_code;
826 tsk->thread.trap_no = 14;
827
828#ifdef CONFIG_MEMORY_FAILURE
829 if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
830 printk(KERN_ERR
831 "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
832 tsk->comm, tsk->pid, address);
833 code = BUS_MCEERR_AR;
834 }
835#endif
836 force_sig_info_fault(SIGBUS, code, address, tsk, fault);
837}
838
839static noinline int
840mm_fault_error(struct pt_regs *regs, unsigned long error_code,
841 unsigned long address, unsigned int fault)
842{
843 /*
844 * Pagefault was interrupted by SIGKILL. We have no reason to
845 * continue pagefault.
846 */
847 if (fatal_signal_pending(current)) {
848 if (!(fault & VM_FAULT_RETRY))
849 up_read(¤t->mm->mmap_sem);
850 if (!(error_code & PF_USER))
851 no_context(regs, error_code, address);
852 return 1;
853 }
854 if (!(fault & VM_FAULT_ERROR))
855 return 0;
856
857 if (fault & VM_FAULT_OOM) {
858 /* Kernel mode? Handle exceptions or die: */
859 if (!(error_code & PF_USER)) {
860 up_read(¤t->mm->mmap_sem);
861 no_context(regs, error_code, address);
862 return 1;
863 }
864
865 out_of_memory(regs, error_code, address);
866 } else {
867 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
868 VM_FAULT_HWPOISON_LARGE))
869 do_sigbus(regs, error_code, address, fault);
870 else
871 BUG();
872 }
873 return 1;
874}
875
876static int spurious_fault_check(unsigned long error_code, pte_t *pte)
877{
878 if ((error_code & PF_WRITE) && !pte_write(*pte))
879 return 0;
880
881 if ((error_code & PF_INSTR) && !pte_exec(*pte))
882 return 0;
883
884 return 1;
885}
886
887/*
888 * Handle a spurious fault caused by a stale TLB entry.
889 *
890 * This allows us to lazily refresh the TLB when increasing the
891 * permissions of a kernel page (RO -> RW or NX -> X). Doing it
892 * eagerly is very expensive since that implies doing a full
893 * cross-processor TLB flush, even if no stale TLB entries exist
894 * on other processors.
895 *
896 * There are no security implications to leaving a stale TLB when
897 * increasing the permissions on a page.
898 */
899static noinline __kprobes int
900spurious_fault(unsigned long error_code, unsigned long address)
901{
902 pgd_t *pgd;
903 pud_t *pud;
904 pmd_t *pmd;
905 pte_t *pte;
906 int ret;
907
908 /* Reserved-bit violation or user access to kernel space? */
909 if (error_code & (PF_USER | PF_RSVD))
910 return 0;
911
912 pgd = init_mm.pgd + pgd_index(address);
913 if (!pgd_present(*pgd))
914 return 0;
915
916 pud = pud_offset(pgd, address);
917 if (!pud_present(*pud))
918 return 0;
919
920 if (pud_large(*pud))
921 return spurious_fault_check(error_code, (pte_t *) pud);
922
923 pmd = pmd_offset(pud, address);
924 if (!pmd_present(*pmd))
925 return 0;
926
927 if (pmd_large(*pmd))
928 return spurious_fault_check(error_code, (pte_t *) pmd);
929
930 /*
931 * Note: don't use pte_present() here, since it returns true
932 * if the _PAGE_PROTNONE bit is set. However, this aliases the
933 * _PAGE_GLOBAL bit, which for kernel pages give false positives
934 * when CONFIG_DEBUG_PAGEALLOC is used.
935 */
936 pte = pte_offset_kernel(pmd, address);
937 if (!(pte_flags(*pte) & _PAGE_PRESENT))
938 return 0;
939
940 ret = spurious_fault_check(error_code, pte);
941 if (!ret)
942 return 0;
943
944 /*
945 * Make sure we have permissions in PMD.
946 * If not, then there's a bug in the page tables:
947 */
948 ret = spurious_fault_check(error_code, (pte_t *) pmd);
949 WARN_ONCE(!ret, "PMD has incorrect permission bits\n");
950
951 return ret;
952}
953
954int show_unhandled_signals = 1;
955
956static inline int
957access_error(unsigned long error_code, struct vm_area_struct *vma)
958{
959 if (error_code & PF_WRITE) {
960 /* write, present and write, not present: */
961 if (unlikely(!(vma->vm_flags & VM_WRITE)))
962 return 1;
963 return 0;
964 }
965
966 /* read, present: */
967 if (unlikely(error_code & PF_PROT))
968 return 1;
969
970 /* read, not present: */
971 if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))))
972 return 1;
973
974 return 0;
975}
976
977static int fault_in_kernel_space(unsigned long address)
978{
979 return address >= TASK_SIZE_MAX;
980}
981
982/*
983 * This routine handles page faults. It determines the address,
984 * and the problem, and then passes it off to one of the appropriate
985 * routines.
986 */
987dotraplinkage void __kprobes
988do_page_fault(struct pt_regs *regs, unsigned long error_code)
989{
990 struct vm_area_struct *vma;
991 struct task_struct *tsk;
992 unsigned long address;
993 struct mm_struct *mm;
994 int fault;
995 int write = error_code & PF_WRITE;
996 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE |
997 (write ? FAULT_FLAG_WRITE : 0);
998
999 tsk = current;
1000 mm = tsk->mm;
1001
1002 /* Get the faulting address: */
1003 address = read_cr2();
1004
1005 /*
1006 * Detect and handle instructions that would cause a page fault for
1007 * both a tracked kernel page and a userspace page.
1008 */
1009 if (kmemcheck_active(regs))
1010 kmemcheck_hide(regs);
1011 prefetchw(&mm->mmap_sem);
1012
1013 if (unlikely(kmmio_fault(regs, address)))
1014 return;
1015
1016 /*
1017 * We fault-in kernel-space virtual memory on-demand. The
1018 * 'reference' page table is init_mm.pgd.
1019 *
1020 * NOTE! We MUST NOT take any locks for this case. We may
1021 * be in an interrupt or a critical region, and should
1022 * only copy the information from the master page table,
1023 * nothing more.
1024 *
1025 * This verifies that the fault happens in kernel space
1026 * (error_code & 4) == 0, and that the fault was not a
1027 * protection error (error_code & 9) == 0.
1028 */
1029 if (unlikely(fault_in_kernel_space(address))) {
1030 if (!(error_code & (PF_RSVD | PF_USER | PF_PROT))) {
1031 if (vmalloc_fault(address) >= 0)
1032 return;
1033
1034 if (kmemcheck_fault(regs, address, error_code))
1035 return;
1036 }
1037
1038 /* Can handle a stale RO->RW TLB: */
1039 if (spurious_fault(error_code, address))
1040 return;
1041
1042 /* kprobes don't want to hook the spurious faults: */
1043 if (notify_page_fault(regs))
1044 return;
1045 /*
1046 * Don't take the mm semaphore here. If we fixup a prefetch
1047 * fault we could otherwise deadlock:
1048 */
1049 bad_area_nosemaphore(regs, error_code, address);
1050
1051 return;
1052 }
1053
1054 /* kprobes don't want to hook the spurious faults: */
1055 if (unlikely(notify_page_fault(regs)))
1056 return;
1057 /*
1058 * It's safe to allow irq's after cr2 has been saved and the
1059 * vmalloc fault has been handled.
1060 *
1061 * User-mode registers count as a user access even for any
1062 * potential system fault or CPU buglet:
1063 */
1064 if (user_mode_vm(regs)) {
1065 local_irq_enable();
1066 error_code |= PF_USER;
1067 } else {
1068 if (regs->flags & X86_EFLAGS_IF)
1069 local_irq_enable();
1070 }
1071
1072 if (unlikely(error_code & PF_RSVD))
1073 pgtable_bad(regs, error_code, address);
1074
1075 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
1076
1077 /*
1078 * If we're in an interrupt, have no user context or are running
1079 * in an atomic region then we must not take the fault:
1080 */
1081 if (unlikely(in_atomic() || !mm)) {
1082 bad_area_nosemaphore(regs, error_code, address);
1083 return;
1084 }
1085
1086 /*
1087 * When running in the kernel we expect faults to occur only to
1088 * addresses in user space. All other faults represent errors in
1089 * the kernel and should generate an OOPS. Unfortunately, in the
1090 * case of an erroneous fault occurring in a code path which already
1091 * holds mmap_sem we will deadlock attempting to validate the fault
1092 * against the address space. Luckily the kernel only validly
1093 * references user space from well defined areas of code, which are
1094 * listed in the exceptions table.
1095 *
1096 * As the vast majority of faults will be valid we will only perform
1097 * the source reference check when there is a possibility of a
1098 * deadlock. Attempt to lock the address space, if we cannot we then
1099 * validate the source. If this is invalid we can skip the address
1100 * space check, thus avoiding the deadlock:
1101 */
1102 if (unlikely(!down_read_trylock(&mm->mmap_sem))) {
1103 if ((error_code & PF_USER) == 0 &&
1104 !search_exception_tables(regs->ip)) {
1105 bad_area_nosemaphore(regs, error_code, address);
1106 return;
1107 }
1108retry:
1109 down_read(&mm->mmap_sem);
1110 } else {
1111 /*
1112 * The above down_read_trylock() might have succeeded in
1113 * which case we'll have missed the might_sleep() from
1114 * down_read():
1115 */
1116 might_sleep();
1117 }
1118
1119 vma = find_vma(mm, address);
1120 if (unlikely(!vma)) {
1121 bad_area(regs, error_code, address);
1122 return;
1123 }
1124 if (likely(vma->vm_start <= address))
1125 goto good_area;
1126 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
1127 bad_area(regs, error_code, address);
1128 return;
1129 }
1130 if (error_code & PF_USER) {
1131 /*
1132 * Accessing the stack below %sp is always a bug.
1133 * The large cushion allows instructions like enter
1134 * and pusha to work. ("enter $65535, $31" pushes
1135 * 32 pointers and then decrements %sp by 65535.)
1136 */
1137 if (unlikely(address + 65536 + 32 * sizeof(unsigned long) < regs->sp)) {
1138 bad_area(regs, error_code, address);
1139 return;
1140 }
1141 }
1142 if (unlikely(expand_stack(vma, address))) {
1143 bad_area(regs, error_code, address);
1144 return;
1145 }
1146
1147 /*
1148 * Ok, we have a good vm_area for this memory access, so
1149 * we can handle it..
1150 */
1151good_area:
1152 if (unlikely(access_error(error_code, vma))) {
1153 bad_area_access_error(regs, error_code, address);
1154 return;
1155 }
1156
1157 /*
1158 * If for any reason at all we couldn't handle the fault,
1159 * make sure we exit gracefully rather than endlessly redo
1160 * the fault:
1161 */
1162 fault = handle_mm_fault(mm, vma, address, flags);
1163
1164 if (unlikely(fault & (VM_FAULT_RETRY|VM_FAULT_ERROR))) {
1165 if (mm_fault_error(regs, error_code, address, fault))
1166 return;
1167 }
1168
1169 /*
1170 * Major/minor page fault accounting is only done on the
1171 * initial attempt. If we go through a retry, it is extremely
1172 * likely that the page will be found in page cache at that point.
1173 */
1174 if (flags & FAULT_FLAG_ALLOW_RETRY) {
1175 if (fault & VM_FAULT_MAJOR) {
1176 tsk->maj_flt++;
1177 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
1178 regs, address);
1179 } else {
1180 tsk->min_flt++;
1181 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
1182 regs, address);
1183 }
1184 if (fault & VM_FAULT_RETRY) {
1185 /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
1186 * of starvation. */
1187 flags &= ~FAULT_FLAG_ALLOW_RETRY;
1188 goto retry;
1189 }
1190 }
1191
1192 check_v8086_mode(regs, address, tsk);
1193
1194 up_read(&mm->mmap_sem);
1195}
1/*
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
5 */
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() */
17
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() */
26
27#define CREATE_TRACE_POINTS
28#include <asm/trace/exceptions.h>
29
30/*
31 * Page fault error code bits:
32 *
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
39 */
40enum x86_pf_error_code {
41
42 PF_PROT = 1 << 0,
43 PF_WRITE = 1 << 1,
44 PF_USER = 1 << 2,
45 PF_RSVD = 1 << 3,
46 PF_INSTR = 1 << 4,
47 PF_PK = 1 << 5,
48};
49
50/*
51 * Returns 0 if mmiotrace is disabled, or if the fault is not
52 * handled by mmiotrace:
53 */
54static nokprobe_inline int
55kmmio_fault(struct pt_regs *regs, unsigned long addr)
56{
57 if (unlikely(is_kmmio_active()))
58 if (kmmio_handler(regs, addr) == 1)
59 return -1;
60 return 0;
61}
62
63static nokprobe_inline int kprobes_fault(struct pt_regs *regs)
64{
65 int ret = 0;
66
67 /* kprobe_running() needs smp_processor_id() */
68 if (kprobes_built_in() && !user_mode(regs)) {
69 preempt_disable();
70 if (kprobe_running() && kprobe_fault_handler(regs, 14))
71 ret = 1;
72 preempt_enable();
73 }
74
75 return ret;
76}
77
78/*
79 * Prefetch quirks:
80 *
81 * 32-bit mode:
82 *
83 * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
84 * Check that here and ignore it.
85 *
86 * 64-bit mode:
87 *
88 * Sometimes the CPU reports invalid exceptions on prefetch.
89 * Check that here and ignore it.
90 *
91 * Opcode checker based on code by Richard Brunner.
92 */
93static inline int
94check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr,
95 unsigned char opcode, int *prefetch)
96{
97 unsigned char instr_hi = opcode & 0xf0;
98 unsigned char instr_lo = opcode & 0x0f;
99
100 switch (instr_hi) {
101 case 0x20:
102 case 0x30:
103 /*
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
108 */
109 return ((instr_lo & 7) == 0x6);
110#ifdef CONFIG_X86_64
111 case 0x40:
112 /*
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.
118 */
119 return (!user_mode(regs) || user_64bit_mode(regs));
120#endif
121 case 0x60:
122 /* 0x64 thru 0x67 are valid prefixes in all modes. */
123 return (instr_lo & 0xC) == 0x4;
124 case 0xF0:
125 /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */
126 return !instr_lo || (instr_lo>>1) == 1;
127 case 0x00:
128 /* Prefetch instruction is 0x0F0D or 0x0F18 */
129 if (probe_kernel_address(instr, opcode))
130 return 0;
131
132 *prefetch = (instr_lo == 0xF) &&
133 (opcode == 0x0D || opcode == 0x18);
134 return 0;
135 default:
136 return 0;
137 }
138}
139
140static int
141is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
142{
143 unsigned char *max_instr;
144 unsigned char *instr;
145 int prefetch = 0;
146
147 /*
148 * If it was a exec (instruction fetch) fault on NX page, then
149 * do not ignore the fault:
150 */
151 if (error_code & PF_INSTR)
152 return 0;
153
154 instr = (void *)convert_ip_to_linear(current, regs);
155 max_instr = instr + 15;
156
157 if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE_MAX)
158 return 0;
159
160 while (instr < max_instr) {
161 unsigned char opcode;
162
163 if (probe_kernel_address(instr, opcode))
164 break;
165
166 instr++;
167
168 if (!check_prefetch_opcode(regs, instr, opcode, &prefetch))
169 break;
170 }
171 return prefetch;
172}
173
174/*
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
179 * on the PTE.
180 *
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.
185 *
186 * 1. T1 : mprotect_key(foo, PAGE_SIZE, pkey=4);
187 * 2. T1 : set PKRU to deny access to pkey=4, touches page
188 * 3. T1 : faults...
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.
193 */
194static void fill_sig_info_pkey(int si_code, siginfo_t *info,
195 struct vm_area_struct *vma)
196{
197 /* This is effectively an #ifdef */
198 if (!boot_cpu_has(X86_FEATURE_OSPKE))
199 return;
200
201 /* Fault not from Protection Keys: nothing to do */
202 if (si_code != SEGV_PKUERR)
203 return;
204 /*
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
209 * valid VMA.
210 */
211 if (!vma) {
212 WARN_ONCE(1, "PKU fault with no VMA passed in");
213 info->si_pkey = 0;
214 return;
215 }
216 /*
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.
220 */
221 info->si_pkey = vma_pkey(vma);
222}
223
224static void
225force_sig_info_fault(int si_signo, int si_code, unsigned long address,
226 struct task_struct *tsk, struct vm_area_struct *vma,
227 int fault)
228{
229 unsigned lsb = 0;
230 siginfo_t info;
231
232 info.si_signo = si_signo;
233 info.si_errno = 0;
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)
239 lsb = PAGE_SHIFT;
240 info.si_addr_lsb = lsb;
241
242 fill_sig_info_pkey(si_code, &info, vma);
243
244 force_sig_info(si_signo, &info, tsk);
245}
246
247DEFINE_SPINLOCK(pgd_lock);
248LIST_HEAD(pgd_list);
249
250#ifdef CONFIG_X86_32
251static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
252{
253 unsigned index = pgd_index(address);
254 pgd_t *pgd_k;
255 pud_t *pud, *pud_k;
256 pmd_t *pmd, *pmd_k;
257
258 pgd += index;
259 pgd_k = init_mm.pgd + index;
260
261 if (!pgd_present(*pgd_k))
262 return NULL;
263
264 /*
265 * set_pgd(pgd, *pgd_k); here would be useless on PAE
266 * and redundant with the set_pmd() on non-PAE. As would
267 * set_pud.
268 */
269 pud = pud_offset(pgd, address);
270 pud_k = pud_offset(pgd_k, address);
271 if (!pud_present(*pud_k))
272 return NULL;
273
274 pmd = pmd_offset(pud, address);
275 pmd_k = pmd_offset(pud_k, address);
276 if (!pmd_present(*pmd_k))
277 return NULL;
278
279 if (!pmd_present(*pmd))
280 set_pmd(pmd, *pmd_k);
281 else
282 BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k));
283
284 return pmd_k;
285}
286
287void vmalloc_sync_all(void)
288{
289 unsigned long address;
290
291 if (SHARED_KERNEL_PMD)
292 return;
293
294 for (address = VMALLOC_START & PMD_MASK;
295 address >= TASK_SIZE && address < FIXADDR_TOP;
296 address += PMD_SIZE) {
297 struct page *page;
298
299 spin_lock(&pgd_lock);
300 list_for_each_entry(page, &pgd_list, lru) {
301 spinlock_t *pgt_lock;
302 pmd_t *ret;
303
304 /* the pgt_lock only for Xen */
305 pgt_lock = &pgd_page_get_mm(page)->page_table_lock;
306
307 spin_lock(pgt_lock);
308 ret = vmalloc_sync_one(page_address(page), address);
309 spin_unlock(pgt_lock);
310
311 if (!ret)
312 break;
313 }
314 spin_unlock(&pgd_lock);
315 }
316}
317
318/*
319 * 32-bit:
320 *
321 * Handle a fault on the vmalloc or module mapping area
322 */
323static noinline int vmalloc_fault(unsigned long address)
324{
325 unsigned long pgd_paddr;
326 pmd_t *pmd_k;
327 pte_t *pte_k;
328
329 /* Make sure we are in vmalloc area: */
330 if (!(address >= VMALLOC_START && address < VMALLOC_END))
331 return -1;
332
333 WARN_ON_ONCE(in_nmi());
334
335 /*
336 * Synchronize this task's top level page-table
337 * with the 'reference' page table.
338 *
339 * Do _not_ use "current" here. We might be inside
340 * an interrupt in the middle of a task switch..
341 */
342 pgd_paddr = read_cr3();
343 pmd_k = vmalloc_sync_one(__va(pgd_paddr), address);
344 if (!pmd_k)
345 return -1;
346
347 if (pmd_huge(*pmd_k))
348 return 0;
349
350 pte_k = pte_offset_kernel(pmd_k, address);
351 if (!pte_present(*pte_k))
352 return -1;
353
354 return 0;
355}
356NOKPROBE_SYMBOL(vmalloc_fault);
357
358/*
359 * Did it hit the DOS screen memory VA from vm86 mode?
360 */
361static inline void
362check_v8086_mode(struct pt_regs *regs, unsigned long address,
363 struct task_struct *tsk)
364{
365#ifdef CONFIG_VM86
366 unsigned long bit;
367
368 if (!v8086_mode(regs) || !tsk->thread.vm86)
369 return;
370
371 bit = (address - 0xA0000) >> PAGE_SHIFT;
372 if (bit < 32)
373 tsk->thread.vm86->screen_bitmap |= 1 << bit;
374#endif
375}
376
377static bool low_pfn(unsigned long pfn)
378{
379 return pfn < max_low_pfn;
380}
381
382static void dump_pagetable(unsigned long address)
383{
384 pgd_t *base = __va(read_cr3());
385 pgd_t *pgd = &base[pgd_index(address)];
386 pmd_t *pmd;
387 pte_t *pte;
388
389#ifdef CONFIG_X86_PAE
390 printk("*pdpt = %016Lx ", pgd_val(*pgd));
391 if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd))
392 goto out;
393#endif
394 pmd = pmd_offset(pud_offset(pgd, address), address);
395 printk(KERN_CONT "*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd));
396
397 /*
398 * We must not directly access the pte in the highpte
399 * case if the page table is located in highmem.
400 * And let's rather not kmap-atomic the pte, just in case
401 * it's allocated already:
402 */
403 if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_large(*pmd))
404 goto out;
405
406 pte = pte_offset_kernel(pmd, address);
407 printk("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte));
408out:
409 printk("\n");
410}
411
412#else /* CONFIG_X86_64: */
413
414void vmalloc_sync_all(void)
415{
416 sync_global_pgds(VMALLOC_START & PGDIR_MASK, VMALLOC_END, 0);
417}
418
419/*
420 * 64-bit:
421 *
422 * Handle a fault on the vmalloc area
423 */
424static noinline int vmalloc_fault(unsigned long address)
425{
426 pgd_t *pgd, *pgd_ref;
427 pud_t *pud, *pud_ref;
428 pmd_t *pmd, *pmd_ref;
429 pte_t *pte, *pte_ref;
430
431 /* Make sure we are in vmalloc area: */
432 if (!(address >= VMALLOC_START && address < VMALLOC_END))
433 return -1;
434
435 WARN_ON_ONCE(in_nmi());
436
437 /*
438 * Copy kernel mappings over when needed. This can also
439 * happen within a race in page table update. In the later
440 * case just flush:
441 */
442 pgd = pgd_offset(current->active_mm, address);
443 pgd_ref = pgd_offset_k(address);
444 if (pgd_none(*pgd_ref))
445 return -1;
446
447 if (pgd_none(*pgd)) {
448 set_pgd(pgd, *pgd_ref);
449 arch_flush_lazy_mmu_mode();
450 } else {
451 BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref));
452 }
453
454 /*
455 * Below here mismatches are bugs because these lower tables
456 * are shared:
457 */
458
459 pud = pud_offset(pgd, address);
460 pud_ref = pud_offset(pgd_ref, address);
461 if (pud_none(*pud_ref))
462 return -1;
463
464 if (pud_none(*pud) || pud_pfn(*pud) != pud_pfn(*pud_ref))
465 BUG();
466
467 if (pud_huge(*pud))
468 return 0;
469
470 pmd = pmd_offset(pud, address);
471 pmd_ref = pmd_offset(pud_ref, address);
472 if (pmd_none(*pmd_ref))
473 return -1;
474
475 if (pmd_none(*pmd) || pmd_pfn(*pmd) != pmd_pfn(*pmd_ref))
476 BUG();
477
478 if (pmd_huge(*pmd))
479 return 0;
480
481 pte_ref = pte_offset_kernel(pmd_ref, address);
482 if (!pte_present(*pte_ref))
483 return -1;
484
485 pte = pte_offset_kernel(pmd, address);
486
487 /*
488 * Don't use pte_page here, because the mappings can point
489 * outside mem_map, and the NUMA hash lookup cannot handle
490 * that:
491 */
492 if (!pte_present(*pte) || pte_pfn(*pte) != pte_pfn(*pte_ref))
493 BUG();
494
495 return 0;
496}
497NOKPROBE_SYMBOL(vmalloc_fault);
498
499#ifdef CONFIG_CPU_SUP_AMD
500static const char errata93_warning[] =
501KERN_ERR
502"******* Your BIOS seems to not contain a fix for K8 errata #93\n"
503"******* Working around it, but it may cause SEGVs or burn power.\n"
504"******* Please consider a BIOS update.\n"
505"******* Disabling USB legacy in the BIOS may also help.\n";
506#endif
507
508/*
509 * No vm86 mode in 64-bit mode:
510 */
511static inline void
512check_v8086_mode(struct pt_regs *regs, unsigned long address,
513 struct task_struct *tsk)
514{
515}
516
517static int bad_address(void *p)
518{
519 unsigned long dummy;
520
521 return probe_kernel_address((unsigned long *)p, dummy);
522}
523
524static void dump_pagetable(unsigned long address)
525{
526 pgd_t *base = __va(read_cr3() & PHYSICAL_PAGE_MASK);
527 pgd_t *pgd = base + pgd_index(address);
528 pud_t *pud;
529 pmd_t *pmd;
530 pte_t *pte;
531
532 if (bad_address(pgd))
533 goto bad;
534
535 printk("PGD %lx ", pgd_val(*pgd));
536
537 if (!pgd_present(*pgd))
538 goto out;
539
540 pud = pud_offset(pgd, address);
541 if (bad_address(pud))
542 goto bad;
543
544 printk("PUD %lx ", pud_val(*pud));
545 if (!pud_present(*pud) || pud_large(*pud))
546 goto out;
547
548 pmd = pmd_offset(pud, address);
549 if (bad_address(pmd))
550 goto bad;
551
552 printk("PMD %lx ", pmd_val(*pmd));
553 if (!pmd_present(*pmd) || pmd_large(*pmd))
554 goto out;
555
556 pte = pte_offset_kernel(pmd, address);
557 if (bad_address(pte))
558 goto bad;
559
560 printk("PTE %lx", pte_val(*pte));
561out:
562 printk("\n");
563 return;
564bad:
565 printk("BAD\n");
566}
567
568#endif /* CONFIG_X86_64 */
569
570/*
571 * Workaround for K8 erratum #93 & buggy BIOS.
572 *
573 * BIOS SMM functions are required to use a specific workaround
574 * to avoid corruption of the 64bit RIP register on C stepping K8.
575 *
576 * A lot of BIOS that didn't get tested properly miss this.
577 *
578 * The OS sees this as a page fault with the upper 32bits of RIP cleared.
579 * Try to work around it here.
580 *
581 * Note we only handle faults in kernel here.
582 * Does nothing on 32-bit.
583 */
584static int is_errata93(struct pt_regs *regs, unsigned long address)
585{
586#if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD)
587 if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD
588 || boot_cpu_data.x86 != 0xf)
589 return 0;
590
591 if (address != regs->ip)
592 return 0;
593
594 if ((address >> 32) != 0)
595 return 0;
596
597 address |= 0xffffffffUL << 32;
598 if ((address >= (u64)_stext && address <= (u64)_etext) ||
599 (address >= MODULES_VADDR && address <= MODULES_END)) {
600 printk_once(errata93_warning);
601 regs->ip = address;
602 return 1;
603 }
604#endif
605 return 0;
606}
607
608/*
609 * Work around K8 erratum #100 K8 in compat mode occasionally jumps
610 * to illegal addresses >4GB.
611 *
612 * We catch this in the page fault handler because these addresses
613 * are not reachable. Just detect this case and return. Any code
614 * segment in LDT is compatibility mode.
615 */
616static int is_errata100(struct pt_regs *regs, unsigned long address)
617{
618#ifdef CONFIG_X86_64
619 if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32))
620 return 1;
621#endif
622 return 0;
623}
624
625static int is_f00f_bug(struct pt_regs *regs, unsigned long address)
626{
627#ifdef CONFIG_X86_F00F_BUG
628 unsigned long nr;
629
630 /*
631 * Pentium F0 0F C7 C8 bug workaround:
632 */
633 if (boot_cpu_has_bug(X86_BUG_F00F)) {
634 nr = (address - idt_descr.address) >> 3;
635
636 if (nr == 6) {
637 do_invalid_op(regs, 0);
638 return 1;
639 }
640 }
641#endif
642 return 0;
643}
644
645static const char nx_warning[] = KERN_CRIT
646"kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n";
647static const char smep_warning[] = KERN_CRIT
648"unable to execute userspace code (SMEP?) (uid: %d)\n";
649
650static void
651show_fault_oops(struct pt_regs *regs, unsigned long error_code,
652 unsigned long address)
653{
654 if (!oops_may_print())
655 return;
656
657 if (error_code & PF_INSTR) {
658 unsigned int level;
659 pgd_t *pgd;
660 pte_t *pte;
661
662 pgd = __va(read_cr3() & PHYSICAL_PAGE_MASK);
663 pgd += pgd_index(address);
664
665 pte = lookup_address_in_pgd(pgd, address, &level);
666
667 if (pte && pte_present(*pte) && !pte_exec(*pte))
668 printk(nx_warning, from_kuid(&init_user_ns, current_uid()));
669 if (pte && pte_present(*pte) && pte_exec(*pte) &&
670 (pgd_flags(*pgd) & _PAGE_USER) &&
671 (__read_cr4() & X86_CR4_SMEP))
672 printk(smep_warning, from_kuid(&init_user_ns, current_uid()));
673 }
674
675 printk(KERN_ALERT "BUG: unable to handle kernel ");
676 if (address < PAGE_SIZE)
677 printk(KERN_CONT "NULL pointer dereference");
678 else
679 printk(KERN_CONT "paging request");
680
681 printk(KERN_CONT " at %p\n", (void *) address);
682 printk(KERN_ALERT "IP:");
683 printk_address(regs->ip);
684
685 dump_pagetable(address);
686}
687
688static noinline void
689pgtable_bad(struct pt_regs *regs, unsigned long error_code,
690 unsigned long address)
691{
692 struct task_struct *tsk;
693 unsigned long flags;
694 int sig;
695
696 flags = oops_begin();
697 tsk = current;
698 sig = SIGKILL;
699
700 printk(KERN_ALERT "%s: Corrupted page table at address %lx\n",
701 tsk->comm, address);
702 dump_pagetable(address);
703
704 tsk->thread.cr2 = address;
705 tsk->thread.trap_nr = X86_TRAP_PF;
706 tsk->thread.error_code = error_code;
707
708 if (__die("Bad pagetable", regs, error_code))
709 sig = 0;
710
711 oops_end(flags, regs, sig);
712}
713
714static noinline void
715no_context(struct pt_regs *regs, unsigned long error_code,
716 unsigned long address, int signal, int si_code)
717{
718 struct task_struct *tsk = current;
719 unsigned long flags;
720 int sig;
721 /* No context means no VMA to pass down */
722 struct vm_area_struct *vma = NULL;
723
724 /* Are we prepared to handle this kernel fault? */
725 if (fixup_exception(regs, X86_TRAP_PF)) {
726 /*
727 * Any interrupt that takes a fault gets the fixup. This makes
728 * the below recursive fault logic only apply to a faults from
729 * task context.
730 */
731 if (in_interrupt())
732 return;
733
734 /*
735 * Per the above we're !in_interrupt(), aka. task context.
736 *
737 * In this case we need to make sure we're not recursively
738 * faulting through the emulate_vsyscall() logic.
739 */
740 if (current_thread_info()->sig_on_uaccess_error && signal) {
741 tsk->thread.trap_nr = X86_TRAP_PF;
742 tsk->thread.error_code = error_code | PF_USER;
743 tsk->thread.cr2 = address;
744
745 /* XXX: hwpoison faults will set the wrong code. */
746 force_sig_info_fault(signal, si_code, address,
747 tsk, vma, 0);
748 }
749
750 /*
751 * Barring that, we can do the fixup and be happy.
752 */
753 return;
754 }
755
756 /*
757 * 32-bit:
758 *
759 * Valid to do another page fault here, because if this fault
760 * had been triggered by is_prefetch fixup_exception would have
761 * handled it.
762 *
763 * 64-bit:
764 *
765 * Hall of shame of CPU/BIOS bugs.
766 */
767 if (is_prefetch(regs, error_code, address))
768 return;
769
770 if (is_errata93(regs, address))
771 return;
772
773 /*
774 * Oops. The kernel tried to access some bad page. We'll have to
775 * terminate things with extreme prejudice:
776 */
777 flags = oops_begin();
778
779 show_fault_oops(regs, error_code, address);
780
781 if (task_stack_end_corrupted(tsk))
782 printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");
783
784 tsk->thread.cr2 = address;
785 tsk->thread.trap_nr = X86_TRAP_PF;
786 tsk->thread.error_code = error_code;
787
788 sig = SIGKILL;
789 if (__die("Oops", regs, error_code))
790 sig = 0;
791
792 /* Executive summary in case the body of the oops scrolled away */
793 printk(KERN_DEFAULT "CR2: %016lx\n", address);
794
795 oops_end(flags, regs, sig);
796}
797
798/*
799 * Print out info about fatal segfaults, if the show_unhandled_signals
800 * sysctl is set:
801 */
802static inline void
803show_signal_msg(struct pt_regs *regs, unsigned long error_code,
804 unsigned long address, struct task_struct *tsk)
805{
806 if (!unhandled_signal(tsk, SIGSEGV))
807 return;
808
809 if (!printk_ratelimit())
810 return;
811
812 printk("%s%s[%d]: segfault at %lx ip %p sp %p error %lx",
813 task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
814 tsk->comm, task_pid_nr(tsk), address,
815 (void *)regs->ip, (void *)regs->sp, error_code);
816
817 print_vma_addr(KERN_CONT " in ", regs->ip);
818
819 printk(KERN_CONT "\n");
820}
821
822static void
823__bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
824 unsigned long address, struct vm_area_struct *vma,
825 int si_code)
826{
827 struct task_struct *tsk = current;
828
829 /* User mode accesses just cause a SIGSEGV */
830 if (error_code & PF_USER) {
831 /*
832 * It's possible to have interrupts off here:
833 */
834 local_irq_enable();
835
836 /*
837 * Valid to do another page fault here because this one came
838 * from user space:
839 */
840 if (is_prefetch(regs, error_code, address))
841 return;
842
843 if (is_errata100(regs, address))
844 return;
845
846#ifdef CONFIG_X86_64
847 /*
848 * Instruction fetch faults in the vsyscall page might need
849 * emulation.
850 */
851 if (unlikely((error_code & PF_INSTR) &&
852 ((address & ~0xfff) == VSYSCALL_ADDR))) {
853 if (emulate_vsyscall(regs, address))
854 return;
855 }
856#endif
857 /* Kernel addresses are always protection faults: */
858 if (address >= TASK_SIZE)
859 error_code |= PF_PROT;
860
861 if (likely(show_unhandled_signals))
862 show_signal_msg(regs, error_code, address, tsk);
863
864 tsk->thread.cr2 = address;
865 tsk->thread.error_code = error_code;
866 tsk->thread.trap_nr = X86_TRAP_PF;
867
868 force_sig_info_fault(SIGSEGV, si_code, address, tsk, vma, 0);
869
870 return;
871 }
872
873 if (is_f00f_bug(regs, address))
874 return;
875
876 no_context(regs, error_code, address, SIGSEGV, si_code);
877}
878
879static noinline void
880bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
881 unsigned long address, struct vm_area_struct *vma)
882{
883 __bad_area_nosemaphore(regs, error_code, address, vma, SEGV_MAPERR);
884}
885
886static void
887__bad_area(struct pt_regs *regs, unsigned long error_code,
888 unsigned long address, struct vm_area_struct *vma, int si_code)
889{
890 struct mm_struct *mm = current->mm;
891
892 /*
893 * Something tried to access memory that isn't in our memory map..
894 * Fix it, but check if it's kernel or user first..
895 */
896 up_read(&mm->mmap_sem);
897
898 __bad_area_nosemaphore(regs, error_code, address, vma, si_code);
899}
900
901static noinline void
902bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address)
903{
904 __bad_area(regs, error_code, address, NULL, SEGV_MAPERR);
905}
906
907static inline bool bad_area_access_from_pkeys(unsigned long error_code,
908 struct vm_area_struct *vma)
909{
910 /* This code is always called on the current mm */
911 bool foreign = false;
912
913 if (!boot_cpu_has(X86_FEATURE_OSPKE))
914 return false;
915 if (error_code & PF_PK)
916 return true;
917 /* this checks permission keys on the VMA: */
918 if (!arch_vma_access_permitted(vma, (error_code & PF_WRITE),
919 (error_code & PF_INSTR), foreign))
920 return true;
921 return false;
922}
923
924static noinline void
925bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
926 unsigned long address, struct vm_area_struct *vma)
927{
928 /*
929 * This OSPKE check is not strictly necessary at runtime.
930 * But, doing it this way allows compiler optimizations
931 * if pkeys are compiled out.
932 */
933 if (bad_area_access_from_pkeys(error_code, vma))
934 __bad_area(regs, error_code, address, vma, SEGV_PKUERR);
935 else
936 __bad_area(regs, error_code, address, vma, SEGV_ACCERR);
937}
938
939static void
940do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
941 struct vm_area_struct *vma, unsigned int fault)
942{
943 struct task_struct *tsk = current;
944 int code = BUS_ADRERR;
945
946 /* Kernel mode? Handle exceptions or die: */
947 if (!(error_code & PF_USER)) {
948 no_context(regs, error_code, address, SIGBUS, BUS_ADRERR);
949 return;
950 }
951
952 /* User-space => ok to do another page fault: */
953 if (is_prefetch(regs, error_code, address))
954 return;
955
956 tsk->thread.cr2 = address;
957 tsk->thread.error_code = error_code;
958 tsk->thread.trap_nr = X86_TRAP_PF;
959
960#ifdef CONFIG_MEMORY_FAILURE
961 if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
962 printk(KERN_ERR
963 "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
964 tsk->comm, tsk->pid, address);
965 code = BUS_MCEERR_AR;
966 }
967#endif
968 force_sig_info_fault(SIGBUS, code, address, tsk, vma, fault);
969}
970
971static noinline void
972mm_fault_error(struct pt_regs *regs, unsigned long error_code,
973 unsigned long address, struct vm_area_struct *vma,
974 unsigned int fault)
975{
976 if (fatal_signal_pending(current) && !(error_code & PF_USER)) {
977 no_context(regs, error_code, address, 0, 0);
978 return;
979 }
980
981 if (fault & VM_FAULT_OOM) {
982 /* Kernel mode? Handle exceptions or die: */
983 if (!(error_code & PF_USER)) {
984 no_context(regs, error_code, address,
985 SIGSEGV, SEGV_MAPERR);
986 return;
987 }
988
989 /*
990 * We ran out of memory, call the OOM killer, and return the
991 * userspace (which will retry the fault, or kill us if we got
992 * oom-killed):
993 */
994 pagefault_out_of_memory();
995 } else {
996 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
997 VM_FAULT_HWPOISON_LARGE))
998 do_sigbus(regs, error_code, address, vma, fault);
999 else if (fault & VM_FAULT_SIGSEGV)
1000 bad_area_nosemaphore(regs, error_code, address, vma);
1001 else
1002 BUG();
1003 }
1004}
1005
1006static int spurious_fault_check(unsigned long error_code, pte_t *pte)
1007{
1008 if ((error_code & PF_WRITE) && !pte_write(*pte))
1009 return 0;
1010
1011 if ((error_code & PF_INSTR) && !pte_exec(*pte))
1012 return 0;
1013 /*
1014 * Note: We do not do lazy flushing on protection key
1015 * changes, so no spurious fault will ever set PF_PK.
1016 */
1017 if ((error_code & PF_PK))
1018 return 1;
1019
1020 return 1;
1021}
1022
1023/*
1024 * Handle a spurious fault caused by a stale TLB entry.
1025 *
1026 * This allows us to lazily refresh the TLB when increasing the
1027 * permissions of a kernel page (RO -> RW or NX -> X). Doing it
1028 * eagerly is very expensive since that implies doing a full
1029 * cross-processor TLB flush, even if no stale TLB entries exist
1030 * on other processors.
1031 *
1032 * Spurious faults may only occur if the TLB contains an entry with
1033 * fewer permission than the page table entry. Non-present (P = 0)
1034 * and reserved bit (R = 1) faults are never spurious.
1035 *
1036 * There are no security implications to leaving a stale TLB when
1037 * increasing the permissions on a page.
1038 *
1039 * Returns non-zero if a spurious fault was handled, zero otherwise.
1040 *
1041 * See Intel Developer's Manual Vol 3 Section 4.10.4.3, bullet 3
1042 * (Optional Invalidation).
1043 */
1044static noinline int
1045spurious_fault(unsigned long error_code, unsigned long address)
1046{
1047 pgd_t *pgd;
1048 pud_t *pud;
1049 pmd_t *pmd;
1050 pte_t *pte;
1051 int ret;
1052
1053 /*
1054 * Only writes to RO or instruction fetches from NX may cause
1055 * spurious faults.
1056 *
1057 * These could be from user or supervisor accesses but the TLB
1058 * is only lazily flushed after a kernel mapping protection
1059 * change, so user accesses are not expected to cause spurious
1060 * faults.
1061 */
1062 if (error_code != (PF_WRITE | PF_PROT)
1063 && error_code != (PF_INSTR | PF_PROT))
1064 return 0;
1065
1066 pgd = init_mm.pgd + pgd_index(address);
1067 if (!pgd_present(*pgd))
1068 return 0;
1069
1070 pud = pud_offset(pgd, address);
1071 if (!pud_present(*pud))
1072 return 0;
1073
1074 if (pud_large(*pud))
1075 return spurious_fault_check(error_code, (pte_t *) pud);
1076
1077 pmd = pmd_offset(pud, address);
1078 if (!pmd_present(*pmd))
1079 return 0;
1080
1081 if (pmd_large(*pmd))
1082 return spurious_fault_check(error_code, (pte_t *) pmd);
1083
1084 pte = pte_offset_kernel(pmd, address);
1085 if (!pte_present(*pte))
1086 return 0;
1087
1088 ret = spurious_fault_check(error_code, pte);
1089 if (!ret)
1090 return 0;
1091
1092 /*
1093 * Make sure we have permissions in PMD.
1094 * If not, then there's a bug in the page tables:
1095 */
1096 ret = spurious_fault_check(error_code, (pte_t *) pmd);
1097 WARN_ONCE(!ret, "PMD has incorrect permission bits\n");
1098
1099 return ret;
1100}
1101NOKPROBE_SYMBOL(spurious_fault);
1102
1103int show_unhandled_signals = 1;
1104
1105static inline int
1106access_error(unsigned long error_code, struct vm_area_struct *vma)
1107{
1108 /* This is only called for the current mm, so: */
1109 bool foreign = false;
1110 /*
1111 * Make sure to check the VMA so that we do not perform
1112 * faults just to hit a PF_PK as soon as we fill in a
1113 * page.
1114 */
1115 if (!arch_vma_access_permitted(vma, (error_code & PF_WRITE),
1116 (error_code & PF_INSTR), foreign))
1117 return 1;
1118
1119 if (error_code & PF_WRITE) {
1120 /* write, present and write, not present: */
1121 if (unlikely(!(vma->vm_flags & VM_WRITE)))
1122 return 1;
1123 return 0;
1124 }
1125
1126 /* read, present: */
1127 if (unlikely(error_code & PF_PROT))
1128 return 1;
1129
1130 /* read, not present: */
1131 if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))))
1132 return 1;
1133
1134 return 0;
1135}
1136
1137static int fault_in_kernel_space(unsigned long address)
1138{
1139 return address >= TASK_SIZE_MAX;
1140}
1141
1142static inline bool smap_violation(int error_code, struct pt_regs *regs)
1143{
1144 if (!IS_ENABLED(CONFIG_X86_SMAP))
1145 return false;
1146
1147 if (!static_cpu_has(X86_FEATURE_SMAP))
1148 return false;
1149
1150 if (error_code & PF_USER)
1151 return false;
1152
1153 if (!user_mode(regs) && (regs->flags & X86_EFLAGS_AC))
1154 return false;
1155
1156 return true;
1157}
1158
1159/*
1160 * This routine handles page faults. It determines the address,
1161 * and the problem, and then passes it off to one of the appropriate
1162 * routines.
1163 *
1164 * This function must have noinline because both callers
1165 * {,trace_}do_page_fault() have notrace on. Having this an actual function
1166 * guarantees there's a function trace entry.
1167 */
1168static noinline void
1169__do_page_fault(struct pt_regs *regs, unsigned long error_code,
1170 unsigned long address)
1171{
1172 struct vm_area_struct *vma;
1173 struct task_struct *tsk;
1174 struct mm_struct *mm;
1175 int fault, major = 0;
1176 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
1177
1178 tsk = current;
1179 mm = tsk->mm;
1180
1181 /*
1182 * Detect and handle instructions that would cause a page fault for
1183 * both a tracked kernel page and a userspace page.
1184 */
1185 if (kmemcheck_active(regs))
1186 kmemcheck_hide(regs);
1187 prefetchw(&mm->mmap_sem);
1188
1189 if (unlikely(kmmio_fault(regs, address)))
1190 return;
1191
1192 /*
1193 * We fault-in kernel-space virtual memory on-demand. The
1194 * 'reference' page table is init_mm.pgd.
1195 *
1196 * NOTE! We MUST NOT take any locks for this case. We may
1197 * be in an interrupt or a critical region, and should
1198 * only copy the information from the master page table,
1199 * nothing more.
1200 *
1201 * This verifies that the fault happens in kernel space
1202 * (error_code & 4) == 0, and that the fault was not a
1203 * protection error (error_code & 9) == 0.
1204 */
1205 if (unlikely(fault_in_kernel_space(address))) {
1206 if (!(error_code & (PF_RSVD | PF_USER | PF_PROT))) {
1207 if (vmalloc_fault(address) >= 0)
1208 return;
1209
1210 if (kmemcheck_fault(regs, address, error_code))
1211 return;
1212 }
1213
1214 /* Can handle a stale RO->RW TLB: */
1215 if (spurious_fault(error_code, address))
1216 return;
1217
1218 /* kprobes don't want to hook the spurious faults: */
1219 if (kprobes_fault(regs))
1220 return;
1221 /*
1222 * Don't take the mm semaphore here. If we fixup a prefetch
1223 * fault we could otherwise deadlock:
1224 */
1225 bad_area_nosemaphore(regs, error_code, address, NULL);
1226
1227 return;
1228 }
1229
1230 /* kprobes don't want to hook the spurious faults: */
1231 if (unlikely(kprobes_fault(regs)))
1232 return;
1233
1234 if (unlikely(error_code & PF_RSVD))
1235 pgtable_bad(regs, error_code, address);
1236
1237 if (unlikely(smap_violation(error_code, regs))) {
1238 bad_area_nosemaphore(regs, error_code, address, NULL);
1239 return;
1240 }
1241
1242 /*
1243 * If we're in an interrupt, have no user context or are running
1244 * in a region with pagefaults disabled then we must not take the fault
1245 */
1246 if (unlikely(faulthandler_disabled() || !mm)) {
1247 bad_area_nosemaphore(regs, error_code, address, NULL);
1248 return;
1249 }
1250
1251 /*
1252 * It's safe to allow irq's after cr2 has been saved and the
1253 * vmalloc fault has been handled.
1254 *
1255 * User-mode registers count as a user access even for any
1256 * potential system fault or CPU buglet:
1257 */
1258 if (user_mode(regs)) {
1259 local_irq_enable();
1260 error_code |= PF_USER;
1261 flags |= FAULT_FLAG_USER;
1262 } else {
1263 if (regs->flags & X86_EFLAGS_IF)
1264 local_irq_enable();
1265 }
1266
1267 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
1268
1269 if (error_code & PF_WRITE)
1270 flags |= FAULT_FLAG_WRITE;
1271 if (error_code & PF_INSTR)
1272 flags |= FAULT_FLAG_INSTRUCTION;
1273
1274 /*
1275 * When running in the kernel we expect faults to occur only to
1276 * addresses in user space. All other faults represent errors in
1277 * the kernel and should generate an OOPS. Unfortunately, in the
1278 * case of an erroneous fault occurring in a code path which already
1279 * holds mmap_sem we will deadlock attempting to validate the fault
1280 * against the address space. Luckily the kernel only validly
1281 * references user space from well defined areas of code, which are
1282 * listed in the exceptions table.
1283 *
1284 * As the vast majority of faults will be valid we will only perform
1285 * the source reference check when there is a possibility of a
1286 * deadlock. Attempt to lock the address space, if we cannot we then
1287 * validate the source. If this is invalid we can skip the address
1288 * space check, thus avoiding the deadlock:
1289 */
1290 if (unlikely(!down_read_trylock(&mm->mmap_sem))) {
1291 if ((error_code & PF_USER) == 0 &&
1292 !search_exception_tables(regs->ip)) {
1293 bad_area_nosemaphore(regs, error_code, address, NULL);
1294 return;
1295 }
1296retry:
1297 down_read(&mm->mmap_sem);
1298 } else {
1299 /*
1300 * The above down_read_trylock() might have succeeded in
1301 * which case we'll have missed the might_sleep() from
1302 * down_read():
1303 */
1304 might_sleep();
1305 }
1306
1307 vma = find_vma(mm, address);
1308 if (unlikely(!vma)) {
1309 bad_area(regs, error_code, address);
1310 return;
1311 }
1312 if (likely(vma->vm_start <= address))
1313 goto good_area;
1314 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
1315 bad_area(regs, error_code, address);
1316 return;
1317 }
1318 if (error_code & PF_USER) {
1319 /*
1320 * Accessing the stack below %sp is always a bug.
1321 * The large cushion allows instructions like enter
1322 * and pusha to work. ("enter $65535, $31" pushes
1323 * 32 pointers and then decrements %sp by 65535.)
1324 */
1325 if (unlikely(address + 65536 + 32 * sizeof(unsigned long) < regs->sp)) {
1326 bad_area(regs, error_code, address);
1327 return;
1328 }
1329 }
1330 if (unlikely(expand_stack(vma, address))) {
1331 bad_area(regs, error_code, address);
1332 return;
1333 }
1334
1335 /*
1336 * Ok, we have a good vm_area for this memory access, so
1337 * we can handle it..
1338 */
1339good_area:
1340 if (unlikely(access_error(error_code, vma))) {
1341 bad_area_access_error(regs, error_code, address, vma);
1342 return;
1343 }
1344
1345 /*
1346 * If for any reason at all we couldn't handle the fault,
1347 * make sure we exit gracefully rather than endlessly redo
1348 * the fault. Since we never set FAULT_FLAG_RETRY_NOWAIT, if
1349 * we get VM_FAULT_RETRY back, the mmap_sem has been unlocked.
1350 */
1351 fault = handle_mm_fault(mm, vma, address, flags);
1352 major |= fault & VM_FAULT_MAJOR;
1353
1354 /*
1355 * If we need to retry the mmap_sem has already been released,
1356 * and if there is a fatal signal pending there is no guarantee
1357 * that we made any progress. Handle this case first.
1358 */
1359 if (unlikely(fault & VM_FAULT_RETRY)) {
1360 /* Retry at most once */
1361 if (flags & FAULT_FLAG_ALLOW_RETRY) {
1362 flags &= ~FAULT_FLAG_ALLOW_RETRY;
1363 flags |= FAULT_FLAG_TRIED;
1364 if (!fatal_signal_pending(tsk))
1365 goto retry;
1366 }
1367
1368 /* User mode? Just return to handle the fatal exception */
1369 if (flags & FAULT_FLAG_USER)
1370 return;
1371
1372 /* Not returning to user mode? Handle exceptions or die: */
1373 no_context(regs, error_code, address, SIGBUS, BUS_ADRERR);
1374 return;
1375 }
1376
1377 up_read(&mm->mmap_sem);
1378 if (unlikely(fault & VM_FAULT_ERROR)) {
1379 mm_fault_error(regs, error_code, address, vma, fault);
1380 return;
1381 }
1382
1383 /*
1384 * Major/minor page fault accounting. If any of the events
1385 * returned VM_FAULT_MAJOR, we account it as a major fault.
1386 */
1387 if (major) {
1388 tsk->maj_flt++;
1389 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address);
1390 } else {
1391 tsk->min_flt++;
1392 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address);
1393 }
1394
1395 check_v8086_mode(regs, address, tsk);
1396}
1397NOKPROBE_SYMBOL(__do_page_fault);
1398
1399dotraplinkage void notrace
1400do_page_fault(struct pt_regs *regs, unsigned long error_code)
1401{
1402 unsigned long address = read_cr2(); /* Get the faulting address */
1403 enum ctx_state prev_state;
1404
1405 /*
1406 * We must have this function tagged with __kprobes, notrace and call
1407 * read_cr2() before calling anything else. To avoid calling any kind
1408 * of tracing machinery before we've observed the CR2 value.
1409 *
1410 * exception_{enter,exit}() contain all sorts of tracepoints.
1411 */
1412
1413 prev_state = exception_enter();
1414 __do_page_fault(regs, error_code, address);
1415 exception_exit(prev_state);
1416}
1417NOKPROBE_SYMBOL(do_page_fault);
1418
1419#ifdef CONFIG_TRACING
1420static nokprobe_inline void
1421trace_page_fault_entries(unsigned long address, struct pt_regs *regs,
1422 unsigned long error_code)
1423{
1424 if (user_mode(regs))
1425 trace_page_fault_user(address, regs, error_code);
1426 else
1427 trace_page_fault_kernel(address, regs, error_code);
1428}
1429
1430dotraplinkage void notrace
1431trace_do_page_fault(struct pt_regs *regs, unsigned long error_code)
1432{
1433 /*
1434 * The exception_enter and tracepoint processing could
1435 * trigger another page faults (user space callchain
1436 * reading) and destroy the original cr2 value, so read
1437 * the faulting address now.
1438 */
1439 unsigned long address = read_cr2();
1440 enum ctx_state prev_state;
1441
1442 prev_state = exception_enter();
1443 trace_page_fault_entries(address, regs, error_code);
1444 __do_page_fault(regs, error_code, address);
1445 exception_exit(prev_state);
1446}
1447NOKPROBE_SYMBOL(trace_do_page_fault);
1448#endif /* CONFIG_TRACING */