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