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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// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (C) 1995 Linus Torvalds
4 * Copyright (C) 2001, 2002 Andi Kleen, SuSE Labs.
5 * Copyright (C) 2008-2009, Red Hat Inc., Ingo Molnar
6 */
7#include <linux/sched.h> /* test_thread_flag(), ... */
8#include <linux/sched/task_stack.h> /* task_stack_*(), ... */
9#include <linux/kdebug.h> /* oops_begin/end, ... */
10#include <linux/extable.h> /* search_exception_tables */
11#include <linux/memblock.h> /* max_low_pfn */
12#include <linux/kprobes.h> /* NOKPROBE_SYMBOL, ... */
13#include <linux/mmiotrace.h> /* kmmio_handler, ... */
14#include <linux/perf_event.h> /* perf_sw_event */
15#include <linux/hugetlb.h> /* hstate_index_to_shift */
16#include <linux/prefetch.h> /* prefetchw */
17#include <linux/context_tracking.h> /* exception_enter(), ... */
18#include <linux/uaccess.h> /* faulthandler_disabled() */
19#include <linux/efi.h> /* efi_recover_from_page_fault()*/
20#include <linux/mm_types.h>
21
22#include <asm/cpufeature.h> /* boot_cpu_has, ... */
23#include <asm/traps.h> /* dotraplinkage, ... */
24#include <asm/fixmap.h> /* VSYSCALL_ADDR */
25#include <asm/vsyscall.h> /* emulate_vsyscall */
26#include <asm/vm86.h> /* struct vm86 */
27#include <asm/mmu_context.h> /* vma_pkey() */
28#include <asm/efi.h> /* efi_recover_from_page_fault()*/
29#include <asm/desc.h> /* store_idt(), ... */
30#include <asm/cpu_entry_area.h> /* exception stack */
31#include <asm/pgtable_areas.h> /* VMALLOC_START, ... */
32#include <asm/kvm_para.h> /* kvm_handle_async_pf */
33
34#define CREATE_TRACE_POINTS
35#include <asm/trace/exceptions.h>
36
37/*
38 * Returns 0 if mmiotrace is disabled, or if the fault is not
39 * handled by mmiotrace:
40 */
41static nokprobe_inline int
42kmmio_fault(struct pt_regs *regs, unsigned long addr)
43{
44 if (unlikely(is_kmmio_active()))
45 if (kmmio_handler(regs, addr) == 1)
46 return -1;
47 return 0;
48}
49
50/*
51 * Prefetch quirks:
52 *
53 * 32-bit mode:
54 *
55 * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
56 * Check that here and ignore it.
57 *
58 * 64-bit mode:
59 *
60 * Sometimes the CPU reports invalid exceptions on prefetch.
61 * Check that here and ignore it.
62 *
63 * Opcode checker based on code by Richard Brunner.
64 */
65static inline int
66check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr,
67 unsigned char opcode, int *prefetch)
68{
69 unsigned char instr_hi = opcode & 0xf0;
70 unsigned char instr_lo = opcode & 0x0f;
71
72 switch (instr_hi) {
73 case 0x20:
74 case 0x30:
75 /*
76 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes.
77 * In X86_64 long mode, the CPU will signal invalid
78 * opcode if some of these prefixes are present so
79 * X86_64 will never get here anyway
80 */
81 return ((instr_lo & 7) == 0x6);
82#ifdef CONFIG_X86_64
83 case 0x40:
84 /*
85 * In AMD64 long mode 0x40..0x4F are valid REX prefixes
86 * Need to figure out under what instruction mode the
87 * instruction was issued. Could check the LDT for lm,
88 * but for now it's good enough to assume that long
89 * mode only uses well known segments or kernel.
90 */
91 return (!user_mode(regs) || user_64bit_mode(regs));
92#endif
93 case 0x60:
94 /* 0x64 thru 0x67 are valid prefixes in all modes. */
95 return (instr_lo & 0xC) == 0x4;
96 case 0xF0:
97 /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */
98 return !instr_lo || (instr_lo>>1) == 1;
99 case 0x00:
100 /* Prefetch instruction is 0x0F0D or 0x0F18 */
101 if (get_kernel_nofault(opcode, instr))
102 return 0;
103
104 *prefetch = (instr_lo == 0xF) &&
105 (opcode == 0x0D || opcode == 0x18);
106 return 0;
107 default:
108 return 0;
109 }
110}
111
112static int
113is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
114{
115 unsigned char *max_instr;
116 unsigned char *instr;
117 int prefetch = 0;
118
119 /*
120 * If it was a exec (instruction fetch) fault on NX page, then
121 * do not ignore the fault:
122 */
123 if (error_code & X86_PF_INSTR)
124 return 0;
125
126 instr = (void *)convert_ip_to_linear(current, regs);
127 max_instr = instr + 15;
128
129 if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE_MAX)
130 return 0;
131
132 while (instr < max_instr) {
133 unsigned char opcode;
134
135 if (get_kernel_nofault(opcode, instr))
136 break;
137
138 instr++;
139
140 if (!check_prefetch_opcode(regs, instr, opcode, &prefetch))
141 break;
142 }
143 return prefetch;
144}
145
146DEFINE_SPINLOCK(pgd_lock);
147LIST_HEAD(pgd_list);
148
149#ifdef CONFIG_X86_32
150static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
151{
152 unsigned index = pgd_index(address);
153 pgd_t *pgd_k;
154 p4d_t *p4d, *p4d_k;
155 pud_t *pud, *pud_k;
156 pmd_t *pmd, *pmd_k;
157
158 pgd += index;
159 pgd_k = init_mm.pgd + index;
160
161 if (!pgd_present(*pgd_k))
162 return NULL;
163
164 /*
165 * set_pgd(pgd, *pgd_k); here would be useless on PAE
166 * and redundant with the set_pmd() on non-PAE. As would
167 * set_p4d/set_pud.
168 */
169 p4d = p4d_offset(pgd, address);
170 p4d_k = p4d_offset(pgd_k, address);
171 if (!p4d_present(*p4d_k))
172 return NULL;
173
174 pud = pud_offset(p4d, address);
175 pud_k = pud_offset(p4d_k, address);
176 if (!pud_present(*pud_k))
177 return NULL;
178
179 pmd = pmd_offset(pud, address);
180 pmd_k = pmd_offset(pud_k, address);
181
182 if (pmd_present(*pmd) != pmd_present(*pmd_k))
183 set_pmd(pmd, *pmd_k);
184
185 if (!pmd_present(*pmd_k))
186 return NULL;
187 else
188 BUG_ON(pmd_pfn(*pmd) != pmd_pfn(*pmd_k));
189
190 return pmd_k;
191}
192
193/*
194 * Handle a fault on the vmalloc or module mapping area
195 *
196 * This is needed because there is a race condition between the time
197 * when the vmalloc mapping code updates the PMD to the point in time
198 * where it synchronizes this update with the other page-tables in the
199 * system.
200 *
201 * In this race window another thread/CPU can map an area on the same
202 * PMD, finds it already present and does not synchronize it with the
203 * rest of the system yet. As a result v[mz]alloc might return areas
204 * which are not mapped in every page-table in the system, causing an
205 * unhandled page-fault when they are accessed.
206 */
207static noinline int vmalloc_fault(unsigned long address)
208{
209 unsigned long pgd_paddr;
210 pmd_t *pmd_k;
211 pte_t *pte_k;
212
213 /* Make sure we are in vmalloc area: */
214 if (!(address >= VMALLOC_START && address < VMALLOC_END))
215 return -1;
216
217 /*
218 * Synchronize this task's top level page-table
219 * with the 'reference' page table.
220 *
221 * Do _not_ use "current" here. We might be inside
222 * an interrupt in the middle of a task switch..
223 */
224 pgd_paddr = read_cr3_pa();
225 pmd_k = vmalloc_sync_one(__va(pgd_paddr), address);
226 if (!pmd_k)
227 return -1;
228
229 if (pmd_large(*pmd_k))
230 return 0;
231
232 pte_k = pte_offset_kernel(pmd_k, address);
233 if (!pte_present(*pte_k))
234 return -1;
235
236 return 0;
237}
238NOKPROBE_SYMBOL(vmalloc_fault);
239
240void arch_sync_kernel_mappings(unsigned long start, unsigned long end)
241{
242 unsigned long addr;
243
244 for (addr = start & PMD_MASK;
245 addr >= TASK_SIZE_MAX && addr < VMALLOC_END;
246 addr += PMD_SIZE) {
247 struct page *page;
248
249 spin_lock(&pgd_lock);
250 list_for_each_entry(page, &pgd_list, lru) {
251 spinlock_t *pgt_lock;
252
253 /* the pgt_lock only for Xen */
254 pgt_lock = &pgd_page_get_mm(page)->page_table_lock;
255
256 spin_lock(pgt_lock);
257 vmalloc_sync_one(page_address(page), addr);
258 spin_unlock(pgt_lock);
259 }
260 spin_unlock(&pgd_lock);
261 }
262}
263
264/*
265 * Did it hit the DOS screen memory VA from vm86 mode?
266 */
267static inline void
268check_v8086_mode(struct pt_regs *regs, unsigned long address,
269 struct task_struct *tsk)
270{
271#ifdef CONFIG_VM86
272 unsigned long bit;
273
274 if (!v8086_mode(regs) || !tsk->thread.vm86)
275 return;
276
277 bit = (address - 0xA0000) >> PAGE_SHIFT;
278 if (bit < 32)
279 tsk->thread.vm86->screen_bitmap |= 1 << bit;
280#endif
281}
282
283static bool low_pfn(unsigned long pfn)
284{
285 return pfn < max_low_pfn;
286}
287
288static void dump_pagetable(unsigned long address)
289{
290 pgd_t *base = __va(read_cr3_pa());
291 pgd_t *pgd = &base[pgd_index(address)];
292 p4d_t *p4d;
293 pud_t *pud;
294 pmd_t *pmd;
295 pte_t *pte;
296
297#ifdef CONFIG_X86_PAE
298 pr_info("*pdpt = %016Lx ", pgd_val(*pgd));
299 if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd))
300 goto out;
301#define pr_pde pr_cont
302#else
303#define pr_pde pr_info
304#endif
305 p4d = p4d_offset(pgd, address);
306 pud = pud_offset(p4d, address);
307 pmd = pmd_offset(pud, address);
308 pr_pde("*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd));
309#undef pr_pde
310
311 /*
312 * We must not directly access the pte in the highpte
313 * case if the page table is located in highmem.
314 * And let's rather not kmap-atomic the pte, just in case
315 * it's allocated already:
316 */
317 if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_large(*pmd))
318 goto out;
319
320 pte = pte_offset_kernel(pmd, address);
321 pr_cont("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte));
322out:
323 pr_cont("\n");
324}
325
326#else /* CONFIG_X86_64: */
327
328#ifdef CONFIG_CPU_SUP_AMD
329static const char errata93_warning[] =
330KERN_ERR
331"******* Your BIOS seems to not contain a fix for K8 errata #93\n"
332"******* Working around it, but it may cause SEGVs or burn power.\n"
333"******* Please consider a BIOS update.\n"
334"******* Disabling USB legacy in the BIOS may also help.\n";
335#endif
336
337/*
338 * No vm86 mode in 64-bit mode:
339 */
340static inline void
341check_v8086_mode(struct pt_regs *regs, unsigned long address,
342 struct task_struct *tsk)
343{
344}
345
346static int bad_address(void *p)
347{
348 unsigned long dummy;
349
350 return get_kernel_nofault(dummy, (unsigned long *)p);
351}
352
353static void dump_pagetable(unsigned long address)
354{
355 pgd_t *base = __va(read_cr3_pa());
356 pgd_t *pgd = base + pgd_index(address);
357 p4d_t *p4d;
358 pud_t *pud;
359 pmd_t *pmd;
360 pte_t *pte;
361
362 if (bad_address(pgd))
363 goto bad;
364
365 pr_info("PGD %lx ", pgd_val(*pgd));
366
367 if (!pgd_present(*pgd))
368 goto out;
369
370 p4d = p4d_offset(pgd, address);
371 if (bad_address(p4d))
372 goto bad;
373
374 pr_cont("P4D %lx ", p4d_val(*p4d));
375 if (!p4d_present(*p4d) || p4d_large(*p4d))
376 goto out;
377
378 pud = pud_offset(p4d, address);
379 if (bad_address(pud))
380 goto bad;
381
382 pr_cont("PUD %lx ", pud_val(*pud));
383 if (!pud_present(*pud) || pud_large(*pud))
384 goto out;
385
386 pmd = pmd_offset(pud, address);
387 if (bad_address(pmd))
388 goto bad;
389
390 pr_cont("PMD %lx ", pmd_val(*pmd));
391 if (!pmd_present(*pmd) || pmd_large(*pmd))
392 goto out;
393
394 pte = pte_offset_kernel(pmd, address);
395 if (bad_address(pte))
396 goto bad;
397
398 pr_cont("PTE %lx", pte_val(*pte));
399out:
400 pr_cont("\n");
401 return;
402bad:
403 pr_info("BAD\n");
404}
405
406#endif /* CONFIG_X86_64 */
407
408/*
409 * Workaround for K8 erratum #93 & buggy BIOS.
410 *
411 * BIOS SMM functions are required to use a specific workaround
412 * to avoid corruption of the 64bit RIP register on C stepping K8.
413 *
414 * A lot of BIOS that didn't get tested properly miss this.
415 *
416 * The OS sees this as a page fault with the upper 32bits of RIP cleared.
417 * Try to work around it here.
418 *
419 * Note we only handle faults in kernel here.
420 * Does nothing on 32-bit.
421 */
422static int is_errata93(struct pt_regs *regs, unsigned long address)
423{
424#if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD)
425 if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD
426 || boot_cpu_data.x86 != 0xf)
427 return 0;
428
429 if (address != regs->ip)
430 return 0;
431
432 if ((address >> 32) != 0)
433 return 0;
434
435 address |= 0xffffffffUL << 32;
436 if ((address >= (u64)_stext && address <= (u64)_etext) ||
437 (address >= MODULES_VADDR && address <= MODULES_END)) {
438 printk_once(errata93_warning);
439 regs->ip = address;
440 return 1;
441 }
442#endif
443 return 0;
444}
445
446/*
447 * Work around K8 erratum #100 K8 in compat mode occasionally jumps
448 * to illegal addresses >4GB.
449 *
450 * We catch this in the page fault handler because these addresses
451 * are not reachable. Just detect this case and return. Any code
452 * segment in LDT is compatibility mode.
453 */
454static int is_errata100(struct pt_regs *regs, unsigned long address)
455{
456#ifdef CONFIG_X86_64
457 if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32))
458 return 1;
459#endif
460 return 0;
461}
462
463/* Pentium F0 0F C7 C8 bug workaround: */
464static int is_f00f_bug(struct pt_regs *regs, unsigned long address)
465{
466#ifdef CONFIG_X86_F00F_BUG
467 if (boot_cpu_has_bug(X86_BUG_F00F) && idt_is_f00f_address(address)) {
468 handle_invalid_op(regs);
469 return 1;
470 }
471#endif
472 return 0;
473}
474
475static void show_ldttss(const struct desc_ptr *gdt, const char *name, u16 index)
476{
477 u32 offset = (index >> 3) * sizeof(struct desc_struct);
478 unsigned long addr;
479 struct ldttss_desc desc;
480
481 if (index == 0) {
482 pr_alert("%s: NULL\n", name);
483 return;
484 }
485
486 if (offset + sizeof(struct ldttss_desc) >= gdt->size) {
487 pr_alert("%s: 0x%hx -- out of bounds\n", name, index);
488 return;
489 }
490
491 if (copy_from_kernel_nofault(&desc, (void *)(gdt->address + offset),
492 sizeof(struct ldttss_desc))) {
493 pr_alert("%s: 0x%hx -- GDT entry is not readable\n",
494 name, index);
495 return;
496 }
497
498 addr = desc.base0 | (desc.base1 << 16) | ((unsigned long)desc.base2 << 24);
499#ifdef CONFIG_X86_64
500 addr |= ((u64)desc.base3 << 32);
501#endif
502 pr_alert("%s: 0x%hx -- base=0x%lx limit=0x%x\n",
503 name, index, addr, (desc.limit0 | (desc.limit1 << 16)));
504}
505
506static void
507show_fault_oops(struct pt_regs *regs, unsigned long error_code, unsigned long address)
508{
509 if (!oops_may_print())
510 return;
511
512 if (error_code & X86_PF_INSTR) {
513 unsigned int level;
514 pgd_t *pgd;
515 pte_t *pte;
516
517 pgd = __va(read_cr3_pa());
518 pgd += pgd_index(address);
519
520 pte = lookup_address_in_pgd(pgd, address, &level);
521
522 if (pte && pte_present(*pte) && !pte_exec(*pte))
523 pr_crit("kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n",
524 from_kuid(&init_user_ns, current_uid()));
525 if (pte && pte_present(*pte) && pte_exec(*pte) &&
526 (pgd_flags(*pgd) & _PAGE_USER) &&
527 (__read_cr4() & X86_CR4_SMEP))
528 pr_crit("unable to execute userspace code (SMEP?) (uid: %d)\n",
529 from_kuid(&init_user_ns, current_uid()));
530 }
531
532 if (address < PAGE_SIZE && !user_mode(regs))
533 pr_alert("BUG: kernel NULL pointer dereference, address: %px\n",
534 (void *)address);
535 else
536 pr_alert("BUG: unable to handle page fault for address: %px\n",
537 (void *)address);
538
539 pr_alert("#PF: %s %s in %s mode\n",
540 (error_code & X86_PF_USER) ? "user" : "supervisor",
541 (error_code & X86_PF_INSTR) ? "instruction fetch" :
542 (error_code & X86_PF_WRITE) ? "write access" :
543 "read access",
544 user_mode(regs) ? "user" : "kernel");
545 pr_alert("#PF: error_code(0x%04lx) - %s\n", error_code,
546 !(error_code & X86_PF_PROT) ? "not-present page" :
547 (error_code & X86_PF_RSVD) ? "reserved bit violation" :
548 (error_code & X86_PF_PK) ? "protection keys violation" :
549 "permissions violation");
550
551 if (!(error_code & X86_PF_USER) && user_mode(regs)) {
552 struct desc_ptr idt, gdt;
553 u16 ldtr, tr;
554
555 /*
556 * This can happen for quite a few reasons. The more obvious
557 * ones are faults accessing the GDT, or LDT. Perhaps
558 * surprisingly, if the CPU tries to deliver a benign or
559 * contributory exception from user code and gets a page fault
560 * during delivery, the page fault can be delivered as though
561 * it originated directly from user code. This could happen
562 * due to wrong permissions on the IDT, GDT, LDT, TSS, or
563 * kernel or IST stack.
564 */
565 store_idt(&idt);
566
567 /* Usable even on Xen PV -- it's just slow. */
568 native_store_gdt(&gdt);
569
570 pr_alert("IDT: 0x%lx (limit=0x%hx) GDT: 0x%lx (limit=0x%hx)\n",
571 idt.address, idt.size, gdt.address, gdt.size);
572
573 store_ldt(ldtr);
574 show_ldttss(&gdt, "LDTR", ldtr);
575
576 store_tr(tr);
577 show_ldttss(&gdt, "TR", tr);
578 }
579
580 dump_pagetable(address);
581}
582
583static noinline void
584pgtable_bad(struct pt_regs *regs, unsigned long error_code,
585 unsigned long address)
586{
587 struct task_struct *tsk;
588 unsigned long flags;
589 int sig;
590
591 flags = oops_begin();
592 tsk = current;
593 sig = SIGKILL;
594
595 printk(KERN_ALERT "%s: Corrupted page table at address %lx\n",
596 tsk->comm, address);
597 dump_pagetable(address);
598
599 if (__die("Bad pagetable", regs, error_code))
600 sig = 0;
601
602 oops_end(flags, regs, sig);
603}
604
605static void set_signal_archinfo(unsigned long address,
606 unsigned long error_code)
607{
608 struct task_struct *tsk = current;
609
610 /*
611 * To avoid leaking information about the kernel page
612 * table layout, pretend that user-mode accesses to
613 * kernel addresses are always protection faults.
614 *
615 * NB: This means that failed vsyscalls with vsyscall=none
616 * will have the PROT bit. This doesn't leak any
617 * information and does not appear to cause any problems.
618 */
619 if (address >= TASK_SIZE_MAX)
620 error_code |= X86_PF_PROT;
621
622 tsk->thread.trap_nr = X86_TRAP_PF;
623 tsk->thread.error_code = error_code | X86_PF_USER;
624 tsk->thread.cr2 = address;
625}
626
627static noinline void
628no_context(struct pt_regs *regs, unsigned long error_code,
629 unsigned long address, int signal, int si_code)
630{
631 struct task_struct *tsk = current;
632 unsigned long flags;
633 int sig;
634
635 if (user_mode(regs)) {
636 /*
637 * This is an implicit supervisor-mode access from user
638 * mode. Bypass all the kernel-mode recovery code and just
639 * OOPS.
640 */
641 goto oops;
642 }
643
644 /* Are we prepared to handle this kernel fault? */
645 if (fixup_exception(regs, X86_TRAP_PF, error_code, address)) {
646 /*
647 * Any interrupt that takes a fault gets the fixup. This makes
648 * the below recursive fault logic only apply to a faults from
649 * task context.
650 */
651 if (in_interrupt())
652 return;
653
654 /*
655 * Per the above we're !in_interrupt(), aka. task context.
656 *
657 * In this case we need to make sure we're not recursively
658 * faulting through the emulate_vsyscall() logic.
659 */
660 if (current->thread.sig_on_uaccess_err && signal) {
661 set_signal_archinfo(address, error_code);
662
663 /* XXX: hwpoison faults will set the wrong code. */
664 force_sig_fault(signal, si_code, (void __user *)address);
665 }
666
667 /*
668 * Barring that, we can do the fixup and be happy.
669 */
670 return;
671 }
672
673#ifdef CONFIG_VMAP_STACK
674 /*
675 * Stack overflow? During boot, we can fault near the initial
676 * stack in the direct map, but that's not an overflow -- check
677 * that we're in vmalloc space to avoid this.
678 */
679 if (is_vmalloc_addr((void *)address) &&
680 (((unsigned long)tsk->stack - 1 - address < PAGE_SIZE) ||
681 address - ((unsigned long)tsk->stack + THREAD_SIZE) < PAGE_SIZE)) {
682 unsigned long stack = __this_cpu_ist_top_va(DF) - sizeof(void *);
683 /*
684 * We're likely to be running with very little stack space
685 * left. It's plausible that we'd hit this condition but
686 * double-fault even before we get this far, in which case
687 * we're fine: the double-fault handler will deal with it.
688 *
689 * We don't want to make it all the way into the oops code
690 * and then double-fault, though, because we're likely to
691 * break the console driver and lose most of the stack dump.
692 */
693 asm volatile ("movq %[stack], %%rsp\n\t"
694 "call handle_stack_overflow\n\t"
695 "1: jmp 1b"
696 : ASM_CALL_CONSTRAINT
697 : "D" ("kernel stack overflow (page fault)"),
698 "S" (regs), "d" (address),
699 [stack] "rm" (stack));
700 unreachable();
701 }
702#endif
703
704 /*
705 * 32-bit:
706 *
707 * Valid to do another page fault here, because if this fault
708 * had been triggered by is_prefetch fixup_exception would have
709 * handled it.
710 *
711 * 64-bit:
712 *
713 * Hall of shame of CPU/BIOS bugs.
714 */
715 if (is_prefetch(regs, error_code, address))
716 return;
717
718 if (is_errata93(regs, address))
719 return;
720
721 /*
722 * Buggy firmware could access regions which might page fault, try to
723 * recover from such faults.
724 */
725 if (IS_ENABLED(CONFIG_EFI))
726 efi_recover_from_page_fault(address);
727
728oops:
729 /*
730 * Oops. The kernel tried to access some bad page. We'll have to
731 * terminate things with extreme prejudice:
732 */
733 flags = oops_begin();
734
735 show_fault_oops(regs, error_code, address);
736
737 if (task_stack_end_corrupted(tsk))
738 printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");
739
740 sig = SIGKILL;
741 if (__die("Oops", regs, error_code))
742 sig = 0;
743
744 /* Executive summary in case the body of the oops scrolled away */
745 printk(KERN_DEFAULT "CR2: %016lx\n", address);
746
747 oops_end(flags, regs, sig);
748}
749
750/*
751 * Print out info about fatal segfaults, if the show_unhandled_signals
752 * sysctl is set:
753 */
754static inline void
755show_signal_msg(struct pt_regs *regs, unsigned long error_code,
756 unsigned long address, struct task_struct *tsk)
757{
758 const char *loglvl = task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG;
759
760 if (!unhandled_signal(tsk, SIGSEGV))
761 return;
762
763 if (!printk_ratelimit())
764 return;
765
766 printk("%s%s[%d]: segfault at %lx ip %px sp %px error %lx",
767 loglvl, tsk->comm, task_pid_nr(tsk), address,
768 (void *)regs->ip, (void *)regs->sp, error_code);
769
770 print_vma_addr(KERN_CONT " in ", regs->ip);
771
772 printk(KERN_CONT "\n");
773
774 show_opcodes(regs, loglvl);
775}
776
777/*
778 * The (legacy) vsyscall page is the long page in the kernel portion
779 * of the address space that has user-accessible permissions.
780 */
781static bool is_vsyscall_vaddr(unsigned long vaddr)
782{
783 return unlikely((vaddr & PAGE_MASK) == VSYSCALL_ADDR);
784}
785
786static void
787__bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
788 unsigned long address, u32 pkey, int si_code)
789{
790 struct task_struct *tsk = current;
791
792 /* User mode accesses just cause a SIGSEGV */
793 if (user_mode(regs) && (error_code & X86_PF_USER)) {
794 /*
795 * It's possible to have interrupts off here:
796 */
797 local_irq_enable();
798
799 /*
800 * Valid to do another page fault here because this one came
801 * from user space:
802 */
803 if (is_prefetch(regs, error_code, address))
804 return;
805
806 if (is_errata100(regs, address))
807 return;
808
809 /*
810 * To avoid leaking information about the kernel page table
811 * layout, pretend that user-mode accesses to kernel addresses
812 * are always protection faults.
813 */
814 if (address >= TASK_SIZE_MAX)
815 error_code |= X86_PF_PROT;
816
817 if (likely(show_unhandled_signals))
818 show_signal_msg(regs, error_code, address, tsk);
819
820 set_signal_archinfo(address, error_code);
821
822 if (si_code == SEGV_PKUERR)
823 force_sig_pkuerr((void __user *)address, pkey);
824
825 force_sig_fault(SIGSEGV, si_code, (void __user *)address);
826
827 local_irq_disable();
828
829 return;
830 }
831
832 if (is_f00f_bug(regs, address))
833 return;
834
835 no_context(regs, error_code, address, SIGSEGV, si_code);
836}
837
838static noinline void
839bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
840 unsigned long address)
841{
842 __bad_area_nosemaphore(regs, error_code, address, 0, SEGV_MAPERR);
843}
844
845static void
846__bad_area(struct pt_regs *regs, unsigned long error_code,
847 unsigned long address, u32 pkey, int si_code)
848{
849 struct mm_struct *mm = current->mm;
850 /*
851 * Something tried to access memory that isn't in our memory map..
852 * Fix it, but check if it's kernel or user first..
853 */
854 mmap_read_unlock(mm);
855
856 __bad_area_nosemaphore(regs, error_code, address, pkey, si_code);
857}
858
859static noinline void
860bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address)
861{
862 __bad_area(regs, error_code, address, 0, SEGV_MAPERR);
863}
864
865static inline bool bad_area_access_from_pkeys(unsigned long error_code,
866 struct vm_area_struct *vma)
867{
868 /* This code is always called on the current mm */
869 bool foreign = false;
870
871 if (!boot_cpu_has(X86_FEATURE_OSPKE))
872 return false;
873 if (error_code & X86_PF_PK)
874 return true;
875 /* this checks permission keys on the VMA: */
876 if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE),
877 (error_code & X86_PF_INSTR), foreign))
878 return true;
879 return false;
880}
881
882static noinline void
883bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
884 unsigned long address, struct vm_area_struct *vma)
885{
886 /*
887 * This OSPKE check is not strictly necessary at runtime.
888 * But, doing it this way allows compiler optimizations
889 * if pkeys are compiled out.
890 */
891 if (bad_area_access_from_pkeys(error_code, vma)) {
892 /*
893 * A protection key fault means that the PKRU value did not allow
894 * access to some PTE. Userspace can figure out what PKRU was
895 * from the XSAVE state. This function captures the pkey from
896 * the vma and passes it to userspace so userspace can discover
897 * which protection key was set on the PTE.
898 *
899 * If we get here, we know that the hardware signaled a X86_PF_PK
900 * fault and that there was a VMA once we got in the fault
901 * handler. It does *not* guarantee that the VMA we find here
902 * was the one that we faulted on.
903 *
904 * 1. T1 : mprotect_key(foo, PAGE_SIZE, pkey=4);
905 * 2. T1 : set PKRU to deny access to pkey=4, touches page
906 * 3. T1 : faults...
907 * 4. T2: mprotect_key(foo, PAGE_SIZE, pkey=5);
908 * 5. T1 : enters fault handler, takes mmap_lock, etc...
909 * 6. T1 : reaches here, sees vma_pkey(vma)=5, when we really
910 * faulted on a pte with its pkey=4.
911 */
912 u32 pkey = vma_pkey(vma);
913
914 __bad_area(regs, error_code, address, pkey, SEGV_PKUERR);
915 } else {
916 __bad_area(regs, error_code, address, 0, SEGV_ACCERR);
917 }
918}
919
920static void
921do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
922 vm_fault_t fault)
923{
924 /* Kernel mode? Handle exceptions or die: */
925 if (!(error_code & X86_PF_USER)) {
926 no_context(regs, error_code, address, SIGBUS, BUS_ADRERR);
927 return;
928 }
929
930 /* User-space => ok to do another page fault: */
931 if (is_prefetch(regs, error_code, address))
932 return;
933
934 set_signal_archinfo(address, error_code);
935
936#ifdef CONFIG_MEMORY_FAILURE
937 if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
938 struct task_struct *tsk = current;
939 unsigned lsb = 0;
940
941 pr_err(
942 "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
943 tsk->comm, tsk->pid, address);
944 if (fault & VM_FAULT_HWPOISON_LARGE)
945 lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
946 if (fault & VM_FAULT_HWPOISON)
947 lsb = PAGE_SHIFT;
948 force_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb);
949 return;
950 }
951#endif
952 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
953}
954
955static noinline void
956mm_fault_error(struct pt_regs *regs, unsigned long error_code,
957 unsigned long address, vm_fault_t fault)
958{
959 if (fatal_signal_pending(current) && !(error_code & X86_PF_USER)) {
960 no_context(regs, error_code, address, 0, 0);
961 return;
962 }
963
964 if (fault & VM_FAULT_OOM) {
965 /* Kernel mode? Handle exceptions or die: */
966 if (!(error_code & X86_PF_USER)) {
967 no_context(regs, error_code, address,
968 SIGSEGV, SEGV_MAPERR);
969 return;
970 }
971
972 /*
973 * We ran out of memory, call the OOM killer, and return the
974 * userspace (which will retry the fault, or kill us if we got
975 * oom-killed):
976 */
977 pagefault_out_of_memory();
978 } else {
979 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
980 VM_FAULT_HWPOISON_LARGE))
981 do_sigbus(regs, error_code, address, fault);
982 else if (fault & VM_FAULT_SIGSEGV)
983 bad_area_nosemaphore(regs, error_code, address);
984 else
985 BUG();
986 }
987}
988
989static int spurious_kernel_fault_check(unsigned long error_code, pte_t *pte)
990{
991 if ((error_code & X86_PF_WRITE) && !pte_write(*pte))
992 return 0;
993
994 if ((error_code & X86_PF_INSTR) && !pte_exec(*pte))
995 return 0;
996
997 return 1;
998}
999
1000/*
1001 * Handle a spurious fault caused by a stale TLB entry.
1002 *
1003 * This allows us to lazily refresh the TLB when increasing the
1004 * permissions of a kernel page (RO -> RW or NX -> X). Doing it
1005 * eagerly is very expensive since that implies doing a full
1006 * cross-processor TLB flush, even if no stale TLB entries exist
1007 * on other processors.
1008 *
1009 * Spurious faults may only occur if the TLB contains an entry with
1010 * fewer permission than the page table entry. Non-present (P = 0)
1011 * and reserved bit (R = 1) faults are never spurious.
1012 *
1013 * There are no security implications to leaving a stale TLB when
1014 * increasing the permissions on a page.
1015 *
1016 * Returns non-zero if a spurious fault was handled, zero otherwise.
1017 *
1018 * See Intel Developer's Manual Vol 3 Section 4.10.4.3, bullet 3
1019 * (Optional Invalidation).
1020 */
1021static noinline int
1022spurious_kernel_fault(unsigned long error_code, unsigned long address)
1023{
1024 pgd_t *pgd;
1025 p4d_t *p4d;
1026 pud_t *pud;
1027 pmd_t *pmd;
1028 pte_t *pte;
1029 int ret;
1030
1031 /*
1032 * Only writes to RO or instruction fetches from NX may cause
1033 * spurious faults.
1034 *
1035 * These could be from user or supervisor accesses but the TLB
1036 * is only lazily flushed after a kernel mapping protection
1037 * change, so user accesses are not expected to cause spurious
1038 * faults.
1039 */
1040 if (error_code != (X86_PF_WRITE | X86_PF_PROT) &&
1041 error_code != (X86_PF_INSTR | X86_PF_PROT))
1042 return 0;
1043
1044 pgd = init_mm.pgd + pgd_index(address);
1045 if (!pgd_present(*pgd))
1046 return 0;
1047
1048 p4d = p4d_offset(pgd, address);
1049 if (!p4d_present(*p4d))
1050 return 0;
1051
1052 if (p4d_large(*p4d))
1053 return spurious_kernel_fault_check(error_code, (pte_t *) p4d);
1054
1055 pud = pud_offset(p4d, address);
1056 if (!pud_present(*pud))
1057 return 0;
1058
1059 if (pud_large(*pud))
1060 return spurious_kernel_fault_check(error_code, (pte_t *) pud);
1061
1062 pmd = pmd_offset(pud, address);
1063 if (!pmd_present(*pmd))
1064 return 0;
1065
1066 if (pmd_large(*pmd))
1067 return spurious_kernel_fault_check(error_code, (pte_t *) pmd);
1068
1069 pte = pte_offset_kernel(pmd, address);
1070 if (!pte_present(*pte))
1071 return 0;
1072
1073 ret = spurious_kernel_fault_check(error_code, pte);
1074 if (!ret)
1075 return 0;
1076
1077 /*
1078 * Make sure we have permissions in PMD.
1079 * If not, then there's a bug in the page tables:
1080 */
1081 ret = spurious_kernel_fault_check(error_code, (pte_t *) pmd);
1082 WARN_ONCE(!ret, "PMD has incorrect permission bits\n");
1083
1084 return ret;
1085}
1086NOKPROBE_SYMBOL(spurious_kernel_fault);
1087
1088int show_unhandled_signals = 1;
1089
1090static inline int
1091access_error(unsigned long error_code, struct vm_area_struct *vma)
1092{
1093 /* This is only called for the current mm, so: */
1094 bool foreign = false;
1095
1096 /*
1097 * Read or write was blocked by protection keys. This is
1098 * always an unconditional error and can never result in
1099 * a follow-up action to resolve the fault, like a COW.
1100 */
1101 if (error_code & X86_PF_PK)
1102 return 1;
1103
1104 /*
1105 * Make sure to check the VMA so that we do not perform
1106 * faults just to hit a X86_PF_PK as soon as we fill in a
1107 * page.
1108 */
1109 if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE),
1110 (error_code & X86_PF_INSTR), foreign))
1111 return 1;
1112
1113 if (error_code & X86_PF_WRITE) {
1114 /* write, present and write, not present: */
1115 if (unlikely(!(vma->vm_flags & VM_WRITE)))
1116 return 1;
1117 return 0;
1118 }
1119
1120 /* read, present: */
1121 if (unlikely(error_code & X86_PF_PROT))
1122 return 1;
1123
1124 /* read, not present: */
1125 if (unlikely(!vma_is_accessible(vma)))
1126 return 1;
1127
1128 return 0;
1129}
1130
1131static int fault_in_kernel_space(unsigned long address)
1132{
1133 /*
1134 * On 64-bit systems, the vsyscall page is at an address above
1135 * TASK_SIZE_MAX, but is not considered part of the kernel
1136 * address space.
1137 */
1138 if (IS_ENABLED(CONFIG_X86_64) && is_vsyscall_vaddr(address))
1139 return false;
1140
1141 return address >= TASK_SIZE_MAX;
1142}
1143
1144/*
1145 * Called for all faults where 'address' is part of the kernel address
1146 * space. Might get called for faults that originate from *code* that
1147 * ran in userspace or the kernel.
1148 */
1149static void
1150do_kern_addr_fault(struct pt_regs *regs, unsigned long hw_error_code,
1151 unsigned long address)
1152{
1153 /*
1154 * Protection keys exceptions only happen on user pages. We
1155 * have no user pages in the kernel portion of the address
1156 * space, so do not expect them here.
1157 */
1158 WARN_ON_ONCE(hw_error_code & X86_PF_PK);
1159
1160#ifdef CONFIG_X86_32
1161 /*
1162 * We can fault-in kernel-space virtual memory on-demand. The
1163 * 'reference' page table is init_mm.pgd.
1164 *
1165 * NOTE! We MUST NOT take any locks for this case. We may
1166 * be in an interrupt or a critical region, and should
1167 * only copy the information from the master page table,
1168 * nothing more.
1169 *
1170 * Before doing this on-demand faulting, ensure that the
1171 * fault is not any of the following:
1172 * 1. A fault on a PTE with a reserved bit set.
1173 * 2. A fault caused by a user-mode access. (Do not demand-
1174 * fault kernel memory due to user-mode accesses).
1175 * 3. A fault caused by a page-level protection violation.
1176 * (A demand fault would be on a non-present page which
1177 * would have X86_PF_PROT==0).
1178 *
1179 * This is only needed to close a race condition on x86-32 in
1180 * the vmalloc mapping/unmapping code. See the comment above
1181 * vmalloc_fault() for details. On x86-64 the race does not
1182 * exist as the vmalloc mappings don't need to be synchronized
1183 * there.
1184 */
1185 if (!(hw_error_code & (X86_PF_RSVD | X86_PF_USER | X86_PF_PROT))) {
1186 if (vmalloc_fault(address) >= 0)
1187 return;
1188 }
1189#endif
1190
1191 /* Was the fault spurious, caused by lazy TLB invalidation? */
1192 if (spurious_kernel_fault(hw_error_code, address))
1193 return;
1194
1195 /* kprobes don't want to hook the spurious faults: */
1196 if (kprobe_page_fault(regs, X86_TRAP_PF))
1197 return;
1198
1199 /*
1200 * Note, despite being a "bad area", there are quite a few
1201 * acceptable reasons to get here, such as erratum fixups
1202 * and handling kernel code that can fault, like get_user().
1203 *
1204 * Don't take the mm semaphore here. If we fixup a prefetch
1205 * fault we could otherwise deadlock:
1206 */
1207 bad_area_nosemaphore(regs, hw_error_code, address);
1208}
1209NOKPROBE_SYMBOL(do_kern_addr_fault);
1210
1211/* Handle faults in the user portion of the address space */
1212static inline
1213void do_user_addr_fault(struct pt_regs *regs,
1214 unsigned long hw_error_code,
1215 unsigned long address)
1216{
1217 struct vm_area_struct *vma;
1218 struct task_struct *tsk;
1219 struct mm_struct *mm;
1220 vm_fault_t fault;
1221 unsigned int flags = FAULT_FLAG_DEFAULT;
1222
1223 tsk = current;
1224 mm = tsk->mm;
1225
1226 /* kprobes don't want to hook the spurious faults: */
1227 if (unlikely(kprobe_page_fault(regs, X86_TRAP_PF)))
1228 return;
1229
1230 /*
1231 * Reserved bits are never expected to be set on
1232 * entries in the user portion of the page tables.
1233 */
1234 if (unlikely(hw_error_code & X86_PF_RSVD))
1235 pgtable_bad(regs, hw_error_code, address);
1236
1237 /*
1238 * If SMAP is on, check for invalid kernel (supervisor) access to user
1239 * pages in the user address space. The odd case here is WRUSS,
1240 * which, according to the preliminary documentation, does not respect
1241 * SMAP and will have the USER bit set so, in all cases, SMAP
1242 * enforcement appears to be consistent with the USER bit.
1243 */
1244 if (unlikely(cpu_feature_enabled(X86_FEATURE_SMAP) &&
1245 !(hw_error_code & X86_PF_USER) &&
1246 !(regs->flags & X86_EFLAGS_AC)))
1247 {
1248 bad_area_nosemaphore(regs, hw_error_code, address);
1249 return;
1250 }
1251
1252 /*
1253 * If we're in an interrupt, have no user context or are running
1254 * in a region with pagefaults disabled then we must not take the fault
1255 */
1256 if (unlikely(faulthandler_disabled() || !mm)) {
1257 bad_area_nosemaphore(regs, hw_error_code, address);
1258 return;
1259 }
1260
1261 /*
1262 * It's safe to allow irq's after cr2 has been saved and the
1263 * vmalloc fault has been handled.
1264 *
1265 * User-mode registers count as a user access even for any
1266 * potential system fault or CPU buglet:
1267 */
1268 if (user_mode(regs)) {
1269 local_irq_enable();
1270 flags |= FAULT_FLAG_USER;
1271 } else {
1272 if (regs->flags & X86_EFLAGS_IF)
1273 local_irq_enable();
1274 }
1275
1276 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
1277
1278 if (hw_error_code & X86_PF_WRITE)
1279 flags |= FAULT_FLAG_WRITE;
1280 if (hw_error_code & X86_PF_INSTR)
1281 flags |= FAULT_FLAG_INSTRUCTION;
1282
1283#ifdef CONFIG_X86_64
1284 /*
1285 * Faults in the vsyscall page might need emulation. The
1286 * vsyscall page is at a high address (>PAGE_OFFSET), but is
1287 * considered to be part of the user address space.
1288 *
1289 * The vsyscall page does not have a "real" VMA, so do this
1290 * emulation before we go searching for VMAs.
1291 *
1292 * PKRU never rejects instruction fetches, so we don't need
1293 * to consider the PF_PK bit.
1294 */
1295 if (is_vsyscall_vaddr(address)) {
1296 if (emulate_vsyscall(hw_error_code, regs, address))
1297 return;
1298 }
1299#endif
1300
1301 /*
1302 * Kernel-mode access to the user address space should only occur
1303 * on well-defined single instructions listed in the exception
1304 * tables. But, an erroneous kernel fault occurring outside one of
1305 * those areas which also holds mmap_lock might deadlock attempting
1306 * to validate the fault against the address space.
1307 *
1308 * Only do the expensive exception table search when we might be at
1309 * risk of a deadlock. This happens if we
1310 * 1. Failed to acquire mmap_lock, and
1311 * 2. The access did not originate in userspace.
1312 */
1313 if (unlikely(!mmap_read_trylock(mm))) {
1314 if (!user_mode(regs) && !search_exception_tables(regs->ip)) {
1315 /*
1316 * Fault from code in kernel from
1317 * which we do not expect faults.
1318 */
1319 bad_area_nosemaphore(regs, hw_error_code, address);
1320 return;
1321 }
1322retry:
1323 mmap_read_lock(mm);
1324 } else {
1325 /*
1326 * The above down_read_trylock() might have succeeded in
1327 * which case we'll have missed the might_sleep() from
1328 * down_read():
1329 */
1330 might_sleep();
1331 }
1332
1333 vma = find_vma(mm, address);
1334 if (unlikely(!vma)) {
1335 bad_area(regs, hw_error_code, address);
1336 return;
1337 }
1338 if (likely(vma->vm_start <= address))
1339 goto good_area;
1340 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
1341 bad_area(regs, hw_error_code, address);
1342 return;
1343 }
1344 if (unlikely(expand_stack(vma, address))) {
1345 bad_area(regs, hw_error_code, address);
1346 return;
1347 }
1348
1349 /*
1350 * Ok, we have a good vm_area for this memory access, so
1351 * we can handle it..
1352 */
1353good_area:
1354 if (unlikely(access_error(hw_error_code, vma))) {
1355 bad_area_access_error(regs, hw_error_code, address, vma);
1356 return;
1357 }
1358
1359 /*
1360 * If for any reason at all we couldn't handle the fault,
1361 * make sure we exit gracefully rather than endlessly redo
1362 * the fault. Since we never set FAULT_FLAG_RETRY_NOWAIT, if
1363 * we get VM_FAULT_RETRY back, the mmap_lock has been unlocked.
1364 *
1365 * Note that handle_userfault() may also release and reacquire mmap_lock
1366 * (and not return with VM_FAULT_RETRY), when returning to userland to
1367 * repeat the page fault later with a VM_FAULT_NOPAGE retval
1368 * (potentially after handling any pending signal during the return to
1369 * userland). The return to userland is identified whenever
1370 * FAULT_FLAG_USER|FAULT_FLAG_KILLABLE are both set in flags.
1371 */
1372 fault = handle_mm_fault(vma, address, flags, regs);
1373
1374 /* Quick path to respond to signals */
1375 if (fault_signal_pending(fault, regs)) {
1376 if (!user_mode(regs))
1377 no_context(regs, hw_error_code, address, SIGBUS,
1378 BUS_ADRERR);
1379 return;
1380 }
1381
1382 /*
1383 * If we need to retry the mmap_lock has already been released,
1384 * and if there is a fatal signal pending there is no guarantee
1385 * that we made any progress. Handle this case first.
1386 */
1387 if (unlikely((fault & VM_FAULT_RETRY) &&
1388 (flags & FAULT_FLAG_ALLOW_RETRY))) {
1389 flags |= FAULT_FLAG_TRIED;
1390 goto retry;
1391 }
1392
1393 mmap_read_unlock(mm);
1394 if (unlikely(fault & VM_FAULT_ERROR)) {
1395 mm_fault_error(regs, hw_error_code, address, fault);
1396 return;
1397 }
1398
1399 check_v8086_mode(regs, address, tsk);
1400}
1401NOKPROBE_SYMBOL(do_user_addr_fault);
1402
1403static __always_inline void
1404trace_page_fault_entries(struct pt_regs *regs, unsigned long error_code,
1405 unsigned long address)
1406{
1407 if (!trace_pagefault_enabled())
1408 return;
1409
1410 if (user_mode(regs))
1411 trace_page_fault_user(address, regs, error_code);
1412 else
1413 trace_page_fault_kernel(address, regs, error_code);
1414}
1415
1416static __always_inline void
1417handle_page_fault(struct pt_regs *regs, unsigned long error_code,
1418 unsigned long address)
1419{
1420 trace_page_fault_entries(regs, error_code, address);
1421
1422 if (unlikely(kmmio_fault(regs, address)))
1423 return;
1424
1425 /* Was the fault on kernel-controlled part of the address space? */
1426 if (unlikely(fault_in_kernel_space(address))) {
1427 do_kern_addr_fault(regs, error_code, address);
1428 } else {
1429 do_user_addr_fault(regs, error_code, address);
1430 /*
1431 * User address page fault handling might have reenabled
1432 * interrupts. Fixing up all potential exit points of
1433 * do_user_addr_fault() and its leaf functions is just not
1434 * doable w/o creating an unholy mess or turning the code
1435 * upside down.
1436 */
1437 local_irq_disable();
1438 }
1439}
1440
1441DEFINE_IDTENTRY_RAW_ERRORCODE(exc_page_fault)
1442{
1443 unsigned long address = read_cr2();
1444 irqentry_state_t state;
1445
1446 prefetchw(¤t->mm->mmap_lock);
1447
1448 /*
1449 * KVM has two types of events that are, logically, interrupts, but
1450 * are unfortunately delivered using the #PF vector. These events are
1451 * "you just accessed valid memory, but the host doesn't have it right
1452 * now, so I'll put you to sleep if you continue" and "that memory
1453 * you tried to access earlier is available now."
1454 *
1455 * We are relying on the interrupted context being sane (valid RSP,
1456 * relevant locks not held, etc.), which is fine as long as the
1457 * interrupted context had IF=1. We are also relying on the KVM
1458 * async pf type field and CR2 being read consistently instead of
1459 * getting values from real and async page faults mixed up.
1460 *
1461 * Fingers crossed.
1462 *
1463 * The async #PF handling code takes care of idtentry handling
1464 * itself.
1465 */
1466 if (kvm_handle_async_pf(regs, (u32)address))
1467 return;
1468
1469 /*
1470 * Entry handling for valid #PF from kernel mode is slightly
1471 * different: RCU is already watching and rcu_irq_enter() must not
1472 * be invoked because a kernel fault on a user space address might
1473 * sleep.
1474 *
1475 * In case the fault hit a RCU idle region the conditional entry
1476 * code reenabled RCU to avoid subsequent wreckage which helps
1477 * debugability.
1478 */
1479 state = irqentry_enter(regs);
1480
1481 instrumentation_begin();
1482 handle_page_fault(regs, error_code, address);
1483 instrumentation_end();
1484
1485 irqentry_exit(regs, state);
1486}