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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/kfence.h> /* kfence_handle_page_fault */
13#include <linux/kprobes.h> /* NOKPROBE_SYMBOL, ... */
14#include <linux/mmiotrace.h> /* kmmio_handler, ... */
15#include <linux/perf_event.h> /* perf_sw_event */
16#include <linux/hugetlb.h> /* hstate_index_to_shift */
17#include <linux/prefetch.h> /* prefetchw */
18#include <linux/context_tracking.h> /* exception_enter(), ... */
19#include <linux/uaccess.h> /* faulthandler_disabled() */
20#include <linux/efi.h> /* efi_crash_gracefully_on_page_fault()*/
21#include <linux/mm_types.h>
22
23#include <asm/cpufeature.h> /* boot_cpu_has, ... */
24#include <asm/traps.h> /* dotraplinkage, ... */
25#include <asm/fixmap.h> /* VSYSCALL_ADDR */
26#include <asm/vsyscall.h> /* emulate_vsyscall */
27#include <asm/vm86.h> /* struct vm86 */
28#include <asm/mmu_context.h> /* vma_pkey() */
29#include <asm/efi.h> /* efi_crash_gracefully_on_page_fault()*/
30#include <asm/desc.h> /* store_idt(), ... */
31#include <asm/cpu_entry_area.h> /* exception stack */
32#include <asm/pgtable_areas.h> /* VMALLOC_START, ... */
33#include <asm/kvm_para.h> /* kvm_handle_async_pf */
34#include <asm/vdso.h> /* fixup_vdso_exception() */
35#include <asm/irq_stack.h>
36
37#define CREATE_TRACE_POINTS
38#include <asm/trace/exceptions.h>
39
40/*
41 * Returns 0 if mmiotrace is disabled, or if the fault is not
42 * handled by mmiotrace:
43 */
44static nokprobe_inline int
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
53/*
54 * Prefetch quirks:
55 *
56 * 32-bit mode:
57 *
58 * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
59 * Check that here and ignore it. This is AMD erratum #91.
60 *
61 * 64-bit mode:
62 *
63 * Sometimes the CPU reports invalid exceptions on prefetch.
64 * Check that here and ignore it.
65 *
66 * Opcode checker based on code by Richard Brunner.
67 */
68static inline int
69check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr,
70 unsigned char opcode, int *prefetch)
71{
72 unsigned char instr_hi = opcode & 0xf0;
73 unsigned char instr_lo = opcode & 0x0f;
74
75 switch (instr_hi) {
76 case 0x20:
77 case 0x30:
78 /*
79 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes.
80 * In X86_64 long mode, the CPU will signal invalid
81 * opcode if some of these prefixes are present so
82 * X86_64 will never get here anyway
83 */
84 return ((instr_lo & 7) == 0x6);
85#ifdef CONFIG_X86_64
86 case 0x40:
87 /*
88 * In 64-bit mode 0x40..0x4F are valid REX prefixes
89 */
90 return (!user_mode(regs) || user_64bit_mode(regs));
91#endif
92 case 0x60:
93 /* 0x64 thru 0x67 are valid prefixes in all modes. */
94 return (instr_lo & 0xC) == 0x4;
95 case 0xF0:
96 /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */
97 return !instr_lo || (instr_lo>>1) == 1;
98 case 0x00:
99 /* Prefetch instruction is 0x0F0D or 0x0F18 */
100 if (get_kernel_nofault(opcode, instr))
101 return 0;
102
103 *prefetch = (instr_lo == 0xF) &&
104 (opcode == 0x0D || opcode == 0x18);
105 return 0;
106 default:
107 return 0;
108 }
109}
110
111static bool is_amd_k8_pre_npt(void)
112{
113 struct cpuinfo_x86 *c = &boot_cpu_data;
114
115 return unlikely(IS_ENABLED(CONFIG_CPU_SUP_AMD) &&
116 c->x86_vendor == X86_VENDOR_AMD &&
117 c->x86 == 0xf && c->x86_model < 0x40);
118}
119
120static int
121is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
122{
123 unsigned char *max_instr;
124 unsigned char *instr;
125 int prefetch = 0;
126
127 /* Erratum #91 affects AMD K8, pre-NPT CPUs */
128 if (!is_amd_k8_pre_npt())
129 return 0;
130
131 /*
132 * If it was a exec (instruction fetch) fault on NX page, then
133 * do not ignore the fault:
134 */
135 if (error_code & X86_PF_INSTR)
136 return 0;
137
138 instr = (void *)convert_ip_to_linear(current, regs);
139 max_instr = instr + 15;
140
141 /*
142 * This code has historically always bailed out if IP points to a
143 * not-present page (e.g. due to a race). No one has ever
144 * complained about this.
145 */
146 pagefault_disable();
147
148 while (instr < max_instr) {
149 unsigned char opcode;
150
151 if (user_mode(regs)) {
152 if (get_user(opcode, (unsigned char __user *) instr))
153 break;
154 } else {
155 if (get_kernel_nofault(opcode, instr))
156 break;
157 }
158
159 instr++;
160
161 if (!check_prefetch_opcode(regs, instr, opcode, &prefetch))
162 break;
163 }
164
165 pagefault_enable();
166 return prefetch;
167}
168
169DEFINE_SPINLOCK(pgd_lock);
170LIST_HEAD(pgd_list);
171
172#ifdef CONFIG_X86_32
173static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
174{
175 unsigned index = pgd_index(address);
176 pgd_t *pgd_k;
177 p4d_t *p4d, *p4d_k;
178 pud_t *pud, *pud_k;
179 pmd_t *pmd, *pmd_k;
180
181 pgd += index;
182 pgd_k = init_mm.pgd + index;
183
184 if (!pgd_present(*pgd_k))
185 return NULL;
186
187 /*
188 * set_pgd(pgd, *pgd_k); here would be useless on PAE
189 * and redundant with the set_pmd() on non-PAE. As would
190 * set_p4d/set_pud.
191 */
192 p4d = p4d_offset(pgd, address);
193 p4d_k = p4d_offset(pgd_k, address);
194 if (!p4d_present(*p4d_k))
195 return NULL;
196
197 pud = pud_offset(p4d, address);
198 pud_k = pud_offset(p4d_k, address);
199 if (!pud_present(*pud_k))
200 return NULL;
201
202 pmd = pmd_offset(pud, address);
203 pmd_k = pmd_offset(pud_k, address);
204
205 if (pmd_present(*pmd) != pmd_present(*pmd_k))
206 set_pmd(pmd, *pmd_k);
207
208 if (!pmd_present(*pmd_k))
209 return NULL;
210 else
211 BUG_ON(pmd_pfn(*pmd) != pmd_pfn(*pmd_k));
212
213 return pmd_k;
214}
215
216/*
217 * Handle a fault on the vmalloc or module mapping area
218 *
219 * This is needed because there is a race condition between the time
220 * when the vmalloc mapping code updates the PMD to the point in time
221 * where it synchronizes this update with the other page-tables in the
222 * system.
223 *
224 * In this race window another thread/CPU can map an area on the same
225 * PMD, finds it already present and does not synchronize it with the
226 * rest of the system yet. As a result v[mz]alloc might return areas
227 * which are not mapped in every page-table in the system, causing an
228 * unhandled page-fault when they are accessed.
229 */
230static noinline int vmalloc_fault(unsigned long address)
231{
232 unsigned long pgd_paddr;
233 pmd_t *pmd_k;
234 pte_t *pte_k;
235
236 /* Make sure we are in vmalloc area: */
237 if (!(address >= VMALLOC_START && address < VMALLOC_END))
238 return -1;
239
240 /*
241 * Synchronize this task's top level page-table
242 * with the 'reference' page table.
243 *
244 * Do _not_ use "current" here. We might be inside
245 * an interrupt in the middle of a task switch..
246 */
247 pgd_paddr = read_cr3_pa();
248 pmd_k = vmalloc_sync_one(__va(pgd_paddr), address);
249 if (!pmd_k)
250 return -1;
251
252 if (pmd_large(*pmd_k))
253 return 0;
254
255 pte_k = pte_offset_kernel(pmd_k, address);
256 if (!pte_present(*pte_k))
257 return -1;
258
259 return 0;
260}
261NOKPROBE_SYMBOL(vmalloc_fault);
262
263static void __arch_sync_kernel_mappings(unsigned long start, unsigned long end)
264{
265 unsigned long addr;
266
267 for (addr = start & PMD_MASK;
268 addr >= TASK_SIZE_MAX && addr < VMALLOC_END;
269 addr += PMD_SIZE) {
270 struct page *page;
271
272 spin_lock(&pgd_lock);
273 list_for_each_entry(page, &pgd_list, lru) {
274 spinlock_t *pgt_lock;
275
276 /* the pgt_lock only for Xen */
277 pgt_lock = &pgd_page_get_mm(page)->page_table_lock;
278
279 spin_lock(pgt_lock);
280 vmalloc_sync_one(page_address(page), addr);
281 spin_unlock(pgt_lock);
282 }
283 spin_unlock(&pgd_lock);
284 }
285}
286
287void arch_sync_kernel_mappings(unsigned long start, unsigned long end)
288{
289 __arch_sync_kernel_mappings(start, end);
290#ifdef CONFIG_KMSAN
291 /*
292 * KMSAN maintains two additional metadata page mappings for the
293 * [VMALLOC_START, VMALLOC_END) range. These mappings start at
294 * KMSAN_VMALLOC_SHADOW_START and KMSAN_VMALLOC_ORIGIN_START and
295 * have to be synced together with the vmalloc memory mapping.
296 */
297 if (start >= VMALLOC_START && end < VMALLOC_END) {
298 __arch_sync_kernel_mappings(
299 start - VMALLOC_START + KMSAN_VMALLOC_SHADOW_START,
300 end - VMALLOC_START + KMSAN_VMALLOC_SHADOW_START);
301 __arch_sync_kernel_mappings(
302 start - VMALLOC_START + KMSAN_VMALLOC_ORIGIN_START,
303 end - VMALLOC_START + KMSAN_VMALLOC_ORIGIN_START);
304 }
305#endif
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_pa());
316 pgd_t *pgd = &base[pgd_index(address)];
317 p4d_t *p4d;
318 pud_t *pud;
319 pmd_t *pmd;
320 pte_t *pte;
321
322#ifdef CONFIG_X86_PAE
323 pr_info("*pdpt = %016Lx ", pgd_val(*pgd));
324 if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd))
325 goto out;
326#define pr_pde pr_cont
327#else
328#define pr_pde pr_info
329#endif
330 p4d = p4d_offset(pgd, address);
331 pud = pud_offset(p4d, address);
332 pmd = pmd_offset(pud, address);
333 pr_pde("*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd));
334#undef pr_pde
335
336 /*
337 * We must not directly access the pte in the highpte
338 * case if the page table is located in highmem.
339 * And let's rather not kmap-atomic the pte, just in case
340 * it's allocated already:
341 */
342 if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_large(*pmd))
343 goto out;
344
345 pte = pte_offset_kernel(pmd, address);
346 pr_cont("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte));
347out:
348 pr_cont("\n");
349}
350
351#else /* CONFIG_X86_64: */
352
353#ifdef CONFIG_CPU_SUP_AMD
354static const char errata93_warning[] =
355KERN_ERR
356"******* Your BIOS seems to not contain a fix for K8 errata #93\n"
357"******* Working around it, but it may cause SEGVs or burn power.\n"
358"******* Please consider a BIOS update.\n"
359"******* Disabling USB legacy in the BIOS may also help.\n";
360#endif
361
362static int bad_address(void *p)
363{
364 unsigned long dummy;
365
366 return get_kernel_nofault(dummy, (unsigned long *)p);
367}
368
369static void dump_pagetable(unsigned long address)
370{
371 pgd_t *base = __va(read_cr3_pa());
372 pgd_t *pgd = base + pgd_index(address);
373 p4d_t *p4d;
374 pud_t *pud;
375 pmd_t *pmd;
376 pte_t *pte;
377
378 if (bad_address(pgd))
379 goto bad;
380
381 pr_info("PGD %lx ", pgd_val(*pgd));
382
383 if (!pgd_present(*pgd))
384 goto out;
385
386 p4d = p4d_offset(pgd, address);
387 if (bad_address(p4d))
388 goto bad;
389
390 pr_cont("P4D %lx ", p4d_val(*p4d));
391 if (!p4d_present(*p4d) || p4d_large(*p4d))
392 goto out;
393
394 pud = pud_offset(p4d, address);
395 if (bad_address(pud))
396 goto bad;
397
398 pr_cont("PUD %lx ", pud_val(*pud));
399 if (!pud_present(*pud) || pud_large(*pud))
400 goto out;
401
402 pmd = pmd_offset(pud, address);
403 if (bad_address(pmd))
404 goto bad;
405
406 pr_cont("PMD %lx ", pmd_val(*pmd));
407 if (!pmd_present(*pmd) || pmd_large(*pmd))
408 goto out;
409
410 pte = pte_offset_kernel(pmd, address);
411 if (bad_address(pte))
412 goto bad;
413
414 pr_cont("PTE %lx", pte_val(*pte));
415out:
416 pr_cont("\n");
417 return;
418bad:
419 pr_info("BAD\n");
420}
421
422#endif /* CONFIG_X86_64 */
423
424/*
425 * Workaround for K8 erratum #93 & buggy BIOS.
426 *
427 * BIOS SMM functions are required to use a specific workaround
428 * to avoid corruption of the 64bit RIP register on C stepping K8.
429 *
430 * A lot of BIOS that didn't get tested properly miss this.
431 *
432 * The OS sees this as a page fault with the upper 32bits of RIP cleared.
433 * Try to work around it here.
434 *
435 * Note we only handle faults in kernel here.
436 * Does nothing on 32-bit.
437 */
438static int is_errata93(struct pt_regs *regs, unsigned long address)
439{
440#if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD)
441 if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD
442 || boot_cpu_data.x86 != 0xf)
443 return 0;
444
445 if (user_mode(regs))
446 return 0;
447
448 if (address != regs->ip)
449 return 0;
450
451 if ((address >> 32) != 0)
452 return 0;
453
454 address |= 0xffffffffUL << 32;
455 if ((address >= (u64)_stext && address <= (u64)_etext) ||
456 (address >= MODULES_VADDR && address <= MODULES_END)) {
457 printk_once(errata93_warning);
458 regs->ip = address;
459 return 1;
460 }
461#endif
462 return 0;
463}
464
465/*
466 * Work around K8 erratum #100 K8 in compat mode occasionally jumps
467 * to illegal addresses >4GB.
468 *
469 * We catch this in the page fault handler because these addresses
470 * are not reachable. Just detect this case and return. Any code
471 * segment in LDT is compatibility mode.
472 */
473static int is_errata100(struct pt_regs *regs, unsigned long address)
474{
475#ifdef CONFIG_X86_64
476 if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32))
477 return 1;
478#endif
479 return 0;
480}
481
482/* Pentium F0 0F C7 C8 bug workaround: */
483static int is_f00f_bug(struct pt_regs *regs, unsigned long error_code,
484 unsigned long address)
485{
486#ifdef CONFIG_X86_F00F_BUG
487 if (boot_cpu_has_bug(X86_BUG_F00F) && !(error_code & X86_PF_USER) &&
488 idt_is_f00f_address(address)) {
489 handle_invalid_op(regs);
490 return 1;
491 }
492#endif
493 return 0;
494}
495
496static void show_ldttss(const struct desc_ptr *gdt, const char *name, u16 index)
497{
498 u32 offset = (index >> 3) * sizeof(struct desc_struct);
499 unsigned long addr;
500 struct ldttss_desc desc;
501
502 if (index == 0) {
503 pr_alert("%s: NULL\n", name);
504 return;
505 }
506
507 if (offset + sizeof(struct ldttss_desc) >= gdt->size) {
508 pr_alert("%s: 0x%hx -- out of bounds\n", name, index);
509 return;
510 }
511
512 if (copy_from_kernel_nofault(&desc, (void *)(gdt->address + offset),
513 sizeof(struct ldttss_desc))) {
514 pr_alert("%s: 0x%hx -- GDT entry is not readable\n",
515 name, index);
516 return;
517 }
518
519 addr = desc.base0 | (desc.base1 << 16) | ((unsigned long)desc.base2 << 24);
520#ifdef CONFIG_X86_64
521 addr |= ((u64)desc.base3 << 32);
522#endif
523 pr_alert("%s: 0x%hx -- base=0x%lx limit=0x%x\n",
524 name, index, addr, (desc.limit0 | (desc.limit1 << 16)));
525}
526
527static void
528show_fault_oops(struct pt_regs *regs, unsigned long error_code, unsigned long address)
529{
530 if (!oops_may_print())
531 return;
532
533 if (error_code & X86_PF_INSTR) {
534 unsigned int level;
535 pgd_t *pgd;
536 pte_t *pte;
537
538 pgd = __va(read_cr3_pa());
539 pgd += pgd_index(address);
540
541 pte = lookup_address_in_pgd(pgd, address, &level);
542
543 if (pte && pte_present(*pte) && !pte_exec(*pte))
544 pr_crit("kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n",
545 from_kuid(&init_user_ns, current_uid()));
546 if (pte && pte_present(*pte) && pte_exec(*pte) &&
547 (pgd_flags(*pgd) & _PAGE_USER) &&
548 (__read_cr4() & X86_CR4_SMEP))
549 pr_crit("unable to execute userspace code (SMEP?) (uid: %d)\n",
550 from_kuid(&init_user_ns, current_uid()));
551 }
552
553 if (address < PAGE_SIZE && !user_mode(regs))
554 pr_alert("BUG: kernel NULL pointer dereference, address: %px\n",
555 (void *)address);
556 else
557 pr_alert("BUG: unable to handle page fault for address: %px\n",
558 (void *)address);
559
560 pr_alert("#PF: %s %s in %s mode\n",
561 (error_code & X86_PF_USER) ? "user" : "supervisor",
562 (error_code & X86_PF_INSTR) ? "instruction fetch" :
563 (error_code & X86_PF_WRITE) ? "write access" :
564 "read access",
565 user_mode(regs) ? "user" : "kernel");
566 pr_alert("#PF: error_code(0x%04lx) - %s\n", error_code,
567 !(error_code & X86_PF_PROT) ? "not-present page" :
568 (error_code & X86_PF_RSVD) ? "reserved bit violation" :
569 (error_code & X86_PF_PK) ? "protection keys violation" :
570 "permissions violation");
571
572 if (!(error_code & X86_PF_USER) && user_mode(regs)) {
573 struct desc_ptr idt, gdt;
574 u16 ldtr, tr;
575
576 /*
577 * This can happen for quite a few reasons. The more obvious
578 * ones are faults accessing the GDT, or LDT. Perhaps
579 * surprisingly, if the CPU tries to deliver a benign or
580 * contributory exception from user code and gets a page fault
581 * during delivery, the page fault can be delivered as though
582 * it originated directly from user code. This could happen
583 * due to wrong permissions on the IDT, GDT, LDT, TSS, or
584 * kernel or IST stack.
585 */
586 store_idt(&idt);
587
588 /* Usable even on Xen PV -- it's just slow. */
589 native_store_gdt(&gdt);
590
591 pr_alert("IDT: 0x%lx (limit=0x%hx) GDT: 0x%lx (limit=0x%hx)\n",
592 idt.address, idt.size, gdt.address, gdt.size);
593
594 store_ldt(ldtr);
595 show_ldttss(&gdt, "LDTR", ldtr);
596
597 store_tr(tr);
598 show_ldttss(&gdt, "TR", tr);
599 }
600
601 dump_pagetable(address);
602}
603
604static noinline void
605pgtable_bad(struct pt_regs *regs, unsigned long error_code,
606 unsigned long address)
607{
608 struct task_struct *tsk;
609 unsigned long flags;
610 int sig;
611
612 flags = oops_begin();
613 tsk = current;
614 sig = SIGKILL;
615
616 printk(KERN_ALERT "%s: Corrupted page table at address %lx\n",
617 tsk->comm, address);
618 dump_pagetable(address);
619
620 if (__die("Bad pagetable", regs, error_code))
621 sig = 0;
622
623 oops_end(flags, regs, sig);
624}
625
626static void sanitize_error_code(unsigned long address,
627 unsigned long *error_code)
628{
629 /*
630 * To avoid leaking information about the kernel page
631 * table layout, pretend that user-mode accesses to
632 * kernel addresses are always protection faults.
633 *
634 * NB: This means that failed vsyscalls with vsyscall=none
635 * will have the PROT bit. This doesn't leak any
636 * information and does not appear to cause any problems.
637 */
638 if (address >= TASK_SIZE_MAX)
639 *error_code |= X86_PF_PROT;
640}
641
642static void set_signal_archinfo(unsigned long address,
643 unsigned long error_code)
644{
645 struct task_struct *tsk = current;
646
647 tsk->thread.trap_nr = X86_TRAP_PF;
648 tsk->thread.error_code = error_code | X86_PF_USER;
649 tsk->thread.cr2 = address;
650}
651
652static noinline void
653page_fault_oops(struct pt_regs *regs, unsigned long error_code,
654 unsigned long address)
655{
656#ifdef CONFIG_VMAP_STACK
657 struct stack_info info;
658#endif
659 unsigned long flags;
660 int sig;
661
662 if (user_mode(regs)) {
663 /*
664 * Implicit kernel access from user mode? Skip the stack
665 * overflow and EFI special cases.
666 */
667 goto oops;
668 }
669
670#ifdef CONFIG_VMAP_STACK
671 /*
672 * Stack overflow? During boot, we can fault near the initial
673 * stack in the direct map, but that's not an overflow -- check
674 * that we're in vmalloc space to avoid this.
675 */
676 if (is_vmalloc_addr((void *)address) &&
677 get_stack_guard_info((void *)address, &info)) {
678 /*
679 * We're likely to be running with very little stack space
680 * left. It's plausible that we'd hit this condition but
681 * double-fault even before we get this far, in which case
682 * we're fine: the double-fault handler will deal with it.
683 *
684 * We don't want to make it all the way into the oops code
685 * and then double-fault, though, because we're likely to
686 * break the console driver and lose most of the stack dump.
687 */
688 call_on_stack(__this_cpu_ist_top_va(DF) - sizeof(void*),
689 handle_stack_overflow,
690 ASM_CALL_ARG3,
691 , [arg1] "r" (regs), [arg2] "r" (address), [arg3] "r" (&info));
692
693 unreachable();
694 }
695#endif
696
697 /*
698 * Buggy firmware could access regions which might page fault. If
699 * this happens, EFI has a special OOPS path that will try to
700 * avoid hanging the system.
701 */
702 if (IS_ENABLED(CONFIG_EFI))
703 efi_crash_gracefully_on_page_fault(address);
704
705 /* Only not-present faults should be handled by KFENCE. */
706 if (!(error_code & X86_PF_PROT) &&
707 kfence_handle_page_fault(address, error_code & X86_PF_WRITE, regs))
708 return;
709
710oops:
711 /*
712 * Oops. The kernel tried to access some bad page. We'll have to
713 * terminate things with extreme prejudice:
714 */
715 flags = oops_begin();
716
717 show_fault_oops(regs, error_code, address);
718
719 if (task_stack_end_corrupted(current))
720 printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");
721
722 sig = SIGKILL;
723 if (__die("Oops", regs, error_code))
724 sig = 0;
725
726 /* Executive summary in case the body of the oops scrolled away */
727 printk(KERN_DEFAULT "CR2: %016lx\n", address);
728
729 oops_end(flags, regs, sig);
730}
731
732static noinline void
733kernelmode_fixup_or_oops(struct pt_regs *regs, unsigned long error_code,
734 unsigned long address, int signal, int si_code,
735 u32 pkey)
736{
737 WARN_ON_ONCE(user_mode(regs));
738
739 /* Are we prepared to handle this kernel fault? */
740 if (fixup_exception(regs, X86_TRAP_PF, error_code, address)) {
741 /*
742 * Any interrupt that takes a fault gets the fixup. This makes
743 * the below recursive fault logic only apply to a faults from
744 * task context.
745 */
746 if (in_interrupt())
747 return;
748
749 /*
750 * Per the above we're !in_interrupt(), aka. task context.
751 *
752 * In this case we need to make sure we're not recursively
753 * faulting through the emulate_vsyscall() logic.
754 */
755 if (current->thread.sig_on_uaccess_err && signal) {
756 sanitize_error_code(address, &error_code);
757
758 set_signal_archinfo(address, error_code);
759
760 if (si_code == SEGV_PKUERR) {
761 force_sig_pkuerr((void __user *)address, pkey);
762 } else {
763 /* XXX: hwpoison faults will set the wrong code. */
764 force_sig_fault(signal, si_code, (void __user *)address);
765 }
766 }
767
768 /*
769 * Barring that, we can do the fixup and be happy.
770 */
771 return;
772 }
773
774 /*
775 * AMD erratum #91 manifests as a spurious page fault on a PREFETCH
776 * instruction.
777 */
778 if (is_prefetch(regs, error_code, address))
779 return;
780
781 page_fault_oops(regs, error_code, address);
782}
783
784/*
785 * Print out info about fatal segfaults, if the show_unhandled_signals
786 * sysctl is set:
787 */
788static inline void
789show_signal_msg(struct pt_regs *regs, unsigned long error_code,
790 unsigned long address, struct task_struct *tsk)
791{
792 const char *loglvl = task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG;
793 /* This is a racy snapshot, but it's better than nothing. */
794 int cpu = raw_smp_processor_id();
795
796 if (!unhandled_signal(tsk, SIGSEGV))
797 return;
798
799 if (!printk_ratelimit())
800 return;
801
802 printk("%s%s[%d]: segfault at %lx ip %px sp %px error %lx",
803 loglvl, tsk->comm, task_pid_nr(tsk), address,
804 (void *)regs->ip, (void *)regs->sp, error_code);
805
806 print_vma_addr(KERN_CONT " in ", regs->ip);
807
808 /*
809 * Dump the likely CPU where the fatal segfault happened.
810 * This can help identify faulty hardware.
811 */
812 printk(KERN_CONT " likely on CPU %d (core %d, socket %d)", cpu,
813 topology_core_id(cpu), topology_physical_package_id(cpu));
814
815
816 printk(KERN_CONT "\n");
817
818 show_opcodes(regs, loglvl);
819}
820
821/*
822 * The (legacy) vsyscall page is the long page in the kernel portion
823 * of the address space that has user-accessible permissions.
824 */
825static bool is_vsyscall_vaddr(unsigned long vaddr)
826{
827 return unlikely((vaddr & PAGE_MASK) == VSYSCALL_ADDR);
828}
829
830static void
831__bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
832 unsigned long address, u32 pkey, int si_code)
833{
834 struct task_struct *tsk = current;
835
836 if (!user_mode(regs)) {
837 kernelmode_fixup_or_oops(regs, error_code, address,
838 SIGSEGV, si_code, pkey);
839 return;
840 }
841
842 if (!(error_code & X86_PF_USER)) {
843 /* Implicit user access to kernel memory -- just oops */
844 page_fault_oops(regs, error_code, address);
845 return;
846 }
847
848 /*
849 * User mode accesses just cause a SIGSEGV.
850 * It's possible to have interrupts off here:
851 */
852 local_irq_enable();
853
854 /*
855 * Valid to do another page fault here because this one came
856 * from user space:
857 */
858 if (is_prefetch(regs, error_code, address))
859 return;
860
861 if (is_errata100(regs, address))
862 return;
863
864 sanitize_error_code(address, &error_code);
865
866 if (fixup_vdso_exception(regs, X86_TRAP_PF, error_code, address))
867 return;
868
869 if (likely(show_unhandled_signals))
870 show_signal_msg(regs, error_code, address, tsk);
871
872 set_signal_archinfo(address, error_code);
873
874 if (si_code == SEGV_PKUERR)
875 force_sig_pkuerr((void __user *)address, pkey);
876 else
877 force_sig_fault(SIGSEGV, si_code, (void __user *)address);
878
879 local_irq_disable();
880}
881
882static noinline void
883bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
884 unsigned long address)
885{
886 __bad_area_nosemaphore(regs, error_code, address, 0, SEGV_MAPERR);
887}
888
889static void
890__bad_area(struct pt_regs *regs, unsigned long error_code,
891 unsigned long address, u32 pkey, int si_code)
892{
893 struct mm_struct *mm = current->mm;
894 /*
895 * Something tried to access memory that isn't in our memory map..
896 * Fix it, but check if it's kernel or user first..
897 */
898 mmap_read_unlock(mm);
899
900 __bad_area_nosemaphore(regs, error_code, address, pkey, si_code);
901}
902
903static noinline void
904bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address)
905{
906 __bad_area(regs, error_code, address, 0, SEGV_MAPERR);
907}
908
909static inline bool bad_area_access_from_pkeys(unsigned long error_code,
910 struct vm_area_struct *vma)
911{
912 /* This code is always called on the current mm */
913 bool foreign = false;
914
915 if (!cpu_feature_enabled(X86_FEATURE_OSPKE))
916 return false;
917 if (error_code & X86_PF_PK)
918 return true;
919 /* this checks permission keys on the VMA: */
920 if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE),
921 (error_code & X86_PF_INSTR), foreign))
922 return true;
923 return false;
924}
925
926static noinline void
927bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
928 unsigned long address, struct vm_area_struct *vma)
929{
930 /*
931 * This OSPKE check is not strictly necessary at runtime.
932 * But, doing it this way allows compiler optimizations
933 * if pkeys are compiled out.
934 */
935 if (bad_area_access_from_pkeys(error_code, vma)) {
936 /*
937 * A protection key fault means that the PKRU value did not allow
938 * access to some PTE. Userspace can figure out what PKRU was
939 * from the XSAVE state. This function captures the pkey from
940 * the vma and passes it to userspace so userspace can discover
941 * which protection key was set on the PTE.
942 *
943 * If we get here, we know that the hardware signaled a X86_PF_PK
944 * fault and that there was a VMA once we got in the fault
945 * handler. It does *not* guarantee that the VMA we find here
946 * was the one that we faulted on.
947 *
948 * 1. T1 : mprotect_key(foo, PAGE_SIZE, pkey=4);
949 * 2. T1 : set PKRU to deny access to pkey=4, touches page
950 * 3. T1 : faults...
951 * 4. T2: mprotect_key(foo, PAGE_SIZE, pkey=5);
952 * 5. T1 : enters fault handler, takes mmap_lock, etc...
953 * 6. T1 : reaches here, sees vma_pkey(vma)=5, when we really
954 * faulted on a pte with its pkey=4.
955 */
956 u32 pkey = vma_pkey(vma);
957
958 __bad_area(regs, error_code, address, pkey, SEGV_PKUERR);
959 } else {
960 __bad_area(regs, error_code, address, 0, SEGV_ACCERR);
961 }
962}
963
964static void
965do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
966 vm_fault_t fault)
967{
968 /* Kernel mode? Handle exceptions or die: */
969 if (!user_mode(regs)) {
970 kernelmode_fixup_or_oops(regs, error_code, address,
971 SIGBUS, BUS_ADRERR, ARCH_DEFAULT_PKEY);
972 return;
973 }
974
975 /* User-space => ok to do another page fault: */
976 if (is_prefetch(regs, error_code, address))
977 return;
978
979 sanitize_error_code(address, &error_code);
980
981 if (fixup_vdso_exception(regs, X86_TRAP_PF, error_code, address))
982 return;
983
984 set_signal_archinfo(address, error_code);
985
986#ifdef CONFIG_MEMORY_FAILURE
987 if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
988 struct task_struct *tsk = current;
989 unsigned lsb = 0;
990
991 pr_err(
992 "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
993 tsk->comm, tsk->pid, address);
994 if (fault & VM_FAULT_HWPOISON_LARGE)
995 lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
996 if (fault & VM_FAULT_HWPOISON)
997 lsb = PAGE_SHIFT;
998 force_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb);
999 return;
1000 }
1001#endif
1002 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
1003}
1004
1005static int spurious_kernel_fault_check(unsigned long error_code, pte_t *pte)
1006{
1007 if ((error_code & X86_PF_WRITE) && !pte_write(*pte))
1008 return 0;
1009
1010 if ((error_code & X86_PF_INSTR) && !pte_exec(*pte))
1011 return 0;
1012
1013 return 1;
1014}
1015
1016/*
1017 * Handle a spurious fault caused by a stale TLB entry.
1018 *
1019 * This allows us to lazily refresh the TLB when increasing the
1020 * permissions of a kernel page (RO -> RW or NX -> X). Doing it
1021 * eagerly is very expensive since that implies doing a full
1022 * cross-processor TLB flush, even if no stale TLB entries exist
1023 * on other processors.
1024 *
1025 * Spurious faults may only occur if the TLB contains an entry with
1026 * fewer permission than the page table entry. Non-present (P = 0)
1027 * and reserved bit (R = 1) faults are never spurious.
1028 *
1029 * There are no security implications to leaving a stale TLB when
1030 * increasing the permissions on a page.
1031 *
1032 * Returns non-zero if a spurious fault was handled, zero otherwise.
1033 *
1034 * See Intel Developer's Manual Vol 3 Section 4.10.4.3, bullet 3
1035 * (Optional Invalidation).
1036 */
1037static noinline int
1038spurious_kernel_fault(unsigned long error_code, unsigned long address)
1039{
1040 pgd_t *pgd;
1041 p4d_t *p4d;
1042 pud_t *pud;
1043 pmd_t *pmd;
1044 pte_t *pte;
1045 int ret;
1046
1047 /*
1048 * Only writes to RO or instruction fetches from NX may cause
1049 * spurious faults.
1050 *
1051 * These could be from user or supervisor accesses but the TLB
1052 * is only lazily flushed after a kernel mapping protection
1053 * change, so user accesses are not expected to cause spurious
1054 * faults.
1055 */
1056 if (error_code != (X86_PF_WRITE | X86_PF_PROT) &&
1057 error_code != (X86_PF_INSTR | X86_PF_PROT))
1058 return 0;
1059
1060 pgd = init_mm.pgd + pgd_index(address);
1061 if (!pgd_present(*pgd))
1062 return 0;
1063
1064 p4d = p4d_offset(pgd, address);
1065 if (!p4d_present(*p4d))
1066 return 0;
1067
1068 if (p4d_large(*p4d))
1069 return spurious_kernel_fault_check(error_code, (pte_t *) p4d);
1070
1071 pud = pud_offset(p4d, address);
1072 if (!pud_present(*pud))
1073 return 0;
1074
1075 if (pud_large(*pud))
1076 return spurious_kernel_fault_check(error_code, (pte_t *) pud);
1077
1078 pmd = pmd_offset(pud, address);
1079 if (!pmd_present(*pmd))
1080 return 0;
1081
1082 if (pmd_large(*pmd))
1083 return spurious_kernel_fault_check(error_code, (pte_t *) pmd);
1084
1085 pte = pte_offset_kernel(pmd, address);
1086 if (!pte_present(*pte))
1087 return 0;
1088
1089 ret = spurious_kernel_fault_check(error_code, pte);
1090 if (!ret)
1091 return 0;
1092
1093 /*
1094 * Make sure we have permissions in PMD.
1095 * If not, then there's a bug in the page tables:
1096 */
1097 ret = spurious_kernel_fault_check(error_code, (pte_t *) pmd);
1098 WARN_ONCE(!ret, "PMD has incorrect permission bits\n");
1099
1100 return ret;
1101}
1102NOKPROBE_SYMBOL(spurious_kernel_fault);
1103
1104int show_unhandled_signals = 1;
1105
1106static inline int
1107access_error(unsigned long error_code, struct vm_area_struct *vma)
1108{
1109 /* This is only called for the current mm, so: */
1110 bool foreign = false;
1111
1112 /*
1113 * Read or write was blocked by protection keys. This is
1114 * always an unconditional error and can never result in
1115 * a follow-up action to resolve the fault, like a COW.
1116 */
1117 if (error_code & X86_PF_PK)
1118 return 1;
1119
1120 /*
1121 * SGX hardware blocked the access. This usually happens
1122 * when the enclave memory contents have been destroyed, like
1123 * after a suspend/resume cycle. In any case, the kernel can't
1124 * fix the cause of the fault. Handle the fault as an access
1125 * error even in cases where no actual access violation
1126 * occurred. This allows userspace to rebuild the enclave in
1127 * response to the signal.
1128 */
1129 if (unlikely(error_code & X86_PF_SGX))
1130 return 1;
1131
1132 /*
1133 * Make sure to check the VMA so that we do not perform
1134 * faults just to hit a X86_PF_PK as soon as we fill in a
1135 * page.
1136 */
1137 if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE),
1138 (error_code & X86_PF_INSTR), foreign))
1139 return 1;
1140
1141 if (error_code & X86_PF_WRITE) {
1142 /* write, present and write, not present: */
1143 if (unlikely(!(vma->vm_flags & VM_WRITE)))
1144 return 1;
1145 return 0;
1146 }
1147
1148 /* read, present: */
1149 if (unlikely(error_code & X86_PF_PROT))
1150 return 1;
1151
1152 /* read, not present: */
1153 if (unlikely(!vma_is_accessible(vma)))
1154 return 1;
1155
1156 return 0;
1157}
1158
1159bool fault_in_kernel_space(unsigned long address)
1160{
1161 /*
1162 * On 64-bit systems, the vsyscall page is at an address above
1163 * TASK_SIZE_MAX, but is not considered part of the kernel
1164 * address space.
1165 */
1166 if (IS_ENABLED(CONFIG_X86_64) && is_vsyscall_vaddr(address))
1167 return false;
1168
1169 return address >= TASK_SIZE_MAX;
1170}
1171
1172/*
1173 * Called for all faults where 'address' is part of the kernel address
1174 * space. Might get called for faults that originate from *code* that
1175 * ran in userspace or the kernel.
1176 */
1177static void
1178do_kern_addr_fault(struct pt_regs *regs, unsigned long hw_error_code,
1179 unsigned long address)
1180{
1181 /*
1182 * Protection keys exceptions only happen on user pages. We
1183 * have no user pages in the kernel portion of the address
1184 * space, so do not expect them here.
1185 */
1186 WARN_ON_ONCE(hw_error_code & X86_PF_PK);
1187
1188#ifdef CONFIG_X86_32
1189 /*
1190 * We can fault-in kernel-space virtual memory on-demand. The
1191 * 'reference' page table is init_mm.pgd.
1192 *
1193 * NOTE! We MUST NOT take any locks for this case. We may
1194 * be in an interrupt or a critical region, and should
1195 * only copy the information from the master page table,
1196 * nothing more.
1197 *
1198 * Before doing this on-demand faulting, ensure that the
1199 * fault is not any of the following:
1200 * 1. A fault on a PTE with a reserved bit set.
1201 * 2. A fault caused by a user-mode access. (Do not demand-
1202 * fault kernel memory due to user-mode accesses).
1203 * 3. A fault caused by a page-level protection violation.
1204 * (A demand fault would be on a non-present page which
1205 * would have X86_PF_PROT==0).
1206 *
1207 * This is only needed to close a race condition on x86-32 in
1208 * the vmalloc mapping/unmapping code. See the comment above
1209 * vmalloc_fault() for details. On x86-64 the race does not
1210 * exist as the vmalloc mappings don't need to be synchronized
1211 * there.
1212 */
1213 if (!(hw_error_code & (X86_PF_RSVD | X86_PF_USER | X86_PF_PROT))) {
1214 if (vmalloc_fault(address) >= 0)
1215 return;
1216 }
1217#endif
1218
1219 if (is_f00f_bug(regs, hw_error_code, address))
1220 return;
1221
1222 /* Was the fault spurious, caused by lazy TLB invalidation? */
1223 if (spurious_kernel_fault(hw_error_code, address))
1224 return;
1225
1226 /* kprobes don't want to hook the spurious faults: */
1227 if (WARN_ON_ONCE(kprobe_page_fault(regs, X86_TRAP_PF)))
1228 return;
1229
1230 /*
1231 * Note, despite being a "bad area", there are quite a few
1232 * acceptable reasons to get here, such as erratum fixups
1233 * and handling kernel code that can fault, like get_user().
1234 *
1235 * Don't take the mm semaphore here. If we fixup a prefetch
1236 * fault we could otherwise deadlock:
1237 */
1238 bad_area_nosemaphore(regs, hw_error_code, address);
1239}
1240NOKPROBE_SYMBOL(do_kern_addr_fault);
1241
1242/*
1243 * Handle faults in the user portion of the address space. Nothing in here
1244 * should check X86_PF_USER without a specific justification: for almost
1245 * all purposes, we should treat a normal kernel access to user memory
1246 * (e.g. get_user(), put_user(), etc.) the same as the WRUSS instruction.
1247 * The one exception is AC flag handling, which is, per the x86
1248 * architecture, special for WRUSS.
1249 */
1250static inline
1251void do_user_addr_fault(struct pt_regs *regs,
1252 unsigned long error_code,
1253 unsigned long address)
1254{
1255 struct vm_area_struct *vma;
1256 struct task_struct *tsk;
1257 struct mm_struct *mm;
1258 vm_fault_t fault;
1259 unsigned int flags = FAULT_FLAG_DEFAULT;
1260
1261 tsk = current;
1262 mm = tsk->mm;
1263
1264 if (unlikely((error_code & (X86_PF_USER | X86_PF_INSTR)) == X86_PF_INSTR)) {
1265 /*
1266 * Whoops, this is kernel mode code trying to execute from
1267 * user memory. Unless this is AMD erratum #93, which
1268 * corrupts RIP such that it looks like a user address,
1269 * this is unrecoverable. Don't even try to look up the
1270 * VMA or look for extable entries.
1271 */
1272 if (is_errata93(regs, address))
1273 return;
1274
1275 page_fault_oops(regs, error_code, address);
1276 return;
1277 }
1278
1279 /* kprobes don't want to hook the spurious faults: */
1280 if (WARN_ON_ONCE(kprobe_page_fault(regs, X86_TRAP_PF)))
1281 return;
1282
1283 /*
1284 * Reserved bits are never expected to be set on
1285 * entries in the user portion of the page tables.
1286 */
1287 if (unlikely(error_code & X86_PF_RSVD))
1288 pgtable_bad(regs, error_code, address);
1289
1290 /*
1291 * If SMAP is on, check for invalid kernel (supervisor) access to user
1292 * pages in the user address space. The odd case here is WRUSS,
1293 * which, according to the preliminary documentation, does not respect
1294 * SMAP and will have the USER bit set so, in all cases, SMAP
1295 * enforcement appears to be consistent with the USER bit.
1296 */
1297 if (unlikely(cpu_feature_enabled(X86_FEATURE_SMAP) &&
1298 !(error_code & X86_PF_USER) &&
1299 !(regs->flags & X86_EFLAGS_AC))) {
1300 /*
1301 * No extable entry here. This was a kernel access to an
1302 * invalid pointer. get_kernel_nofault() will not get here.
1303 */
1304 page_fault_oops(regs, error_code, address);
1305 return;
1306 }
1307
1308 /*
1309 * If we're in an interrupt, have no user context or are running
1310 * in a region with pagefaults disabled then we must not take the fault
1311 */
1312 if (unlikely(faulthandler_disabled() || !mm)) {
1313 bad_area_nosemaphore(regs, error_code, address);
1314 return;
1315 }
1316
1317 /*
1318 * It's safe to allow irq's after cr2 has been saved and the
1319 * vmalloc fault has been handled.
1320 *
1321 * User-mode registers count as a user access even for any
1322 * potential system fault or CPU buglet:
1323 */
1324 if (user_mode(regs)) {
1325 local_irq_enable();
1326 flags |= FAULT_FLAG_USER;
1327 } else {
1328 if (regs->flags & X86_EFLAGS_IF)
1329 local_irq_enable();
1330 }
1331
1332 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
1333
1334 if (error_code & X86_PF_WRITE)
1335 flags |= FAULT_FLAG_WRITE;
1336 if (error_code & X86_PF_INSTR)
1337 flags |= FAULT_FLAG_INSTRUCTION;
1338
1339#ifdef CONFIG_X86_64
1340 /*
1341 * Faults in the vsyscall page might need emulation. The
1342 * vsyscall page is at a high address (>PAGE_OFFSET), but is
1343 * considered to be part of the user address space.
1344 *
1345 * The vsyscall page does not have a "real" VMA, so do this
1346 * emulation before we go searching for VMAs.
1347 *
1348 * PKRU never rejects instruction fetches, so we don't need
1349 * to consider the PF_PK bit.
1350 */
1351 if (is_vsyscall_vaddr(address)) {
1352 if (emulate_vsyscall(error_code, regs, address))
1353 return;
1354 }
1355#endif
1356
1357 /*
1358 * Kernel-mode access to the user address space should only occur
1359 * on well-defined single instructions listed in the exception
1360 * tables. But, an erroneous kernel fault occurring outside one of
1361 * those areas which also holds mmap_lock might deadlock attempting
1362 * to validate the fault against the address space.
1363 *
1364 * Only do the expensive exception table search when we might be at
1365 * risk of a deadlock. This happens if we
1366 * 1. Failed to acquire mmap_lock, and
1367 * 2. The access did not originate in userspace.
1368 */
1369 if (unlikely(!mmap_read_trylock(mm))) {
1370 if (!user_mode(regs) && !search_exception_tables(regs->ip)) {
1371 /*
1372 * Fault from code in kernel from
1373 * which we do not expect faults.
1374 */
1375 bad_area_nosemaphore(regs, error_code, address);
1376 return;
1377 }
1378retry:
1379 mmap_read_lock(mm);
1380 } else {
1381 /*
1382 * The above down_read_trylock() might have succeeded in
1383 * which case we'll have missed the might_sleep() from
1384 * down_read():
1385 */
1386 might_sleep();
1387 }
1388
1389 vma = find_vma(mm, address);
1390 if (unlikely(!vma)) {
1391 bad_area(regs, error_code, address);
1392 return;
1393 }
1394 if (likely(vma->vm_start <= address))
1395 goto good_area;
1396 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
1397 bad_area(regs, error_code, address);
1398 return;
1399 }
1400 if (unlikely(expand_stack(vma, address))) {
1401 bad_area(regs, error_code, address);
1402 return;
1403 }
1404
1405 /*
1406 * Ok, we have a good vm_area for this memory access, so
1407 * we can handle it..
1408 */
1409good_area:
1410 if (unlikely(access_error(error_code, vma))) {
1411 bad_area_access_error(regs, error_code, address, vma);
1412 return;
1413 }
1414
1415 /*
1416 * If for any reason at all we couldn't handle the fault,
1417 * make sure we exit gracefully rather than endlessly redo
1418 * the fault. Since we never set FAULT_FLAG_RETRY_NOWAIT, if
1419 * we get VM_FAULT_RETRY back, the mmap_lock has been unlocked.
1420 *
1421 * Note that handle_userfault() may also release and reacquire mmap_lock
1422 * (and not return with VM_FAULT_RETRY), when returning to userland to
1423 * repeat the page fault later with a VM_FAULT_NOPAGE retval
1424 * (potentially after handling any pending signal during the return to
1425 * userland). The return to userland is identified whenever
1426 * FAULT_FLAG_USER|FAULT_FLAG_KILLABLE are both set in flags.
1427 */
1428 fault = handle_mm_fault(vma, address, flags, regs);
1429
1430 if (fault_signal_pending(fault, regs)) {
1431 /*
1432 * Quick path to respond to signals. The core mm code
1433 * has unlocked the mm for us if we get here.
1434 */
1435 if (!user_mode(regs))
1436 kernelmode_fixup_or_oops(regs, error_code, address,
1437 SIGBUS, BUS_ADRERR,
1438 ARCH_DEFAULT_PKEY);
1439 return;
1440 }
1441
1442 /* The fault is fully completed (including releasing mmap lock) */
1443 if (fault & VM_FAULT_COMPLETED)
1444 return;
1445
1446 /*
1447 * If we need to retry the mmap_lock has already been released,
1448 * and if there is a fatal signal pending there is no guarantee
1449 * that we made any progress. Handle this case first.
1450 */
1451 if (unlikely(fault & VM_FAULT_RETRY)) {
1452 flags |= FAULT_FLAG_TRIED;
1453 goto retry;
1454 }
1455
1456 mmap_read_unlock(mm);
1457 if (likely(!(fault & VM_FAULT_ERROR)))
1458 return;
1459
1460 if (fatal_signal_pending(current) && !user_mode(regs)) {
1461 kernelmode_fixup_or_oops(regs, error_code, address,
1462 0, 0, ARCH_DEFAULT_PKEY);
1463 return;
1464 }
1465
1466 if (fault & VM_FAULT_OOM) {
1467 /* Kernel mode? Handle exceptions or die: */
1468 if (!user_mode(regs)) {
1469 kernelmode_fixup_or_oops(regs, error_code, address,
1470 SIGSEGV, SEGV_MAPERR,
1471 ARCH_DEFAULT_PKEY);
1472 return;
1473 }
1474
1475 /*
1476 * We ran out of memory, call the OOM killer, and return the
1477 * userspace (which will retry the fault, or kill us if we got
1478 * oom-killed):
1479 */
1480 pagefault_out_of_memory();
1481 } else {
1482 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
1483 VM_FAULT_HWPOISON_LARGE))
1484 do_sigbus(regs, error_code, address, fault);
1485 else if (fault & VM_FAULT_SIGSEGV)
1486 bad_area_nosemaphore(regs, error_code, address);
1487 else
1488 BUG();
1489 }
1490}
1491NOKPROBE_SYMBOL(do_user_addr_fault);
1492
1493static __always_inline void
1494trace_page_fault_entries(struct pt_regs *regs, unsigned long error_code,
1495 unsigned long address)
1496{
1497 if (!trace_pagefault_enabled())
1498 return;
1499
1500 if (user_mode(regs))
1501 trace_page_fault_user(address, regs, error_code);
1502 else
1503 trace_page_fault_kernel(address, regs, error_code);
1504}
1505
1506static __always_inline void
1507handle_page_fault(struct pt_regs *regs, unsigned long error_code,
1508 unsigned long address)
1509{
1510 trace_page_fault_entries(regs, error_code, address);
1511
1512 if (unlikely(kmmio_fault(regs, address)))
1513 return;
1514
1515 /* Was the fault on kernel-controlled part of the address space? */
1516 if (unlikely(fault_in_kernel_space(address))) {
1517 do_kern_addr_fault(regs, error_code, address);
1518 } else {
1519 do_user_addr_fault(regs, error_code, address);
1520 /*
1521 * User address page fault handling might have reenabled
1522 * interrupts. Fixing up all potential exit points of
1523 * do_user_addr_fault() and its leaf functions is just not
1524 * doable w/o creating an unholy mess or turning the code
1525 * upside down.
1526 */
1527 local_irq_disable();
1528 }
1529}
1530
1531DEFINE_IDTENTRY_RAW_ERRORCODE(exc_page_fault)
1532{
1533 unsigned long address = read_cr2();
1534 irqentry_state_t state;
1535
1536 prefetchw(¤t->mm->mmap_lock);
1537
1538 /*
1539 * KVM uses #PF vector to deliver 'page not present' events to guests
1540 * (asynchronous page fault mechanism). The event happens when a
1541 * userspace task is trying to access some valid (from guest's point of
1542 * view) memory which is not currently mapped by the host (e.g. the
1543 * memory is swapped out). Note, the corresponding "page ready" event
1544 * which is injected when the memory becomes available, is delivered via
1545 * an interrupt mechanism and not a #PF exception
1546 * (see arch/x86/kernel/kvm.c: sysvec_kvm_asyncpf_interrupt()).
1547 *
1548 * We are relying on the interrupted context being sane (valid RSP,
1549 * relevant locks not held, etc.), which is fine as long as the
1550 * interrupted context had IF=1. We are also relying on the KVM
1551 * async pf type field and CR2 being read consistently instead of
1552 * getting values from real and async page faults mixed up.
1553 *
1554 * Fingers crossed.
1555 *
1556 * The async #PF handling code takes care of idtentry handling
1557 * itself.
1558 */
1559 if (kvm_handle_async_pf(regs, (u32)address))
1560 return;
1561
1562 /*
1563 * Entry handling for valid #PF from kernel mode is slightly
1564 * different: RCU is already watching and ct_irq_enter() must not
1565 * be invoked because a kernel fault on a user space address might
1566 * sleep.
1567 *
1568 * In case the fault hit a RCU idle region the conditional entry
1569 * code reenabled RCU to avoid subsequent wreckage which helps
1570 * debuggability.
1571 */
1572 state = irqentry_enter(regs);
1573
1574 instrumentation_begin();
1575 handle_page_fault(regs, error_code, address);
1576 instrumentation_end();
1577
1578 irqentry_exit(regs, state);
1579}
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 */