1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Copyright (C) 1995 Linus Torvalds 4 * Copyright (C) 2001, 2002 Andi Kleen, SuSE Labs. 5 * Copyright (C) 2008-2009, Red Hat Inc., Ingo Molnar 6 */ 7 #include <linux/sched.h> /* test_thread_flag(), ... */ 8 #include <linux/sched/task_stack.h> /* task_stack_*(), ... */ 9 #include <linux/kdebug.h> /* oops_begin/end, ... */ 10 #include <linux/extable.h> /* search_exception_tables */ 11 #include <linux/memblock.h> /* max_low_pfn */ 12 #include <linux/kprobes.h> /* NOKPROBE_SYMBOL, ... */ 13 #include <linux/mmiotrace.h> /* kmmio_handler, ... */ 14 #include <linux/perf_event.h> /* perf_sw_event */ 15 #include <linux/hugetlb.h> /* hstate_index_to_shift */ 16 #include <linux/prefetch.h> /* prefetchw */ 17 #include <linux/context_tracking.h> /* exception_enter(), ... */ 18 #include <linux/uaccess.h> /* faulthandler_disabled() */ 19 #include <linux/efi.h> /* efi_recover_from_page_fault()*/ 20 #include <linux/mm_types.h> 21 22 #include <asm/cpufeature.h> /* boot_cpu_has, ... */ 23 #include <asm/traps.h> /* dotraplinkage, ... */ 24 #include <asm/fixmap.h> /* VSYSCALL_ADDR */ 25 #include <asm/vsyscall.h> /* emulate_vsyscall */ 26 #include <asm/vm86.h> /* struct vm86 */ 27 #include <asm/mmu_context.h> /* vma_pkey() */ 28 #include <asm/efi.h> /* efi_recover_from_page_fault()*/ 29 #include <asm/desc.h> /* store_idt(), ... */ 30 #include <asm/cpu_entry_area.h> /* exception stack */ 31 #include <asm/pgtable_areas.h> /* VMALLOC_START, ... */ 32 #include <asm/kvm_para.h> /* kvm_handle_async_pf */ 33 #include <asm/vdso.h> /* fixup_vdso_exception() */ 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 /* 195 * Handle a fault on the vmalloc or module mapping area 196 * 197 * This is needed because there is a race condition between the time 198 * when the vmalloc mapping code updates the PMD to the point in time 199 * where it synchronizes this update with the other page-tables in the 200 * system. 201 * 202 * In this race window another thread/CPU can map an area on the same 203 * PMD, finds it already present and does not synchronize it with the 204 * rest of the system yet. As a result v[mz]alloc might return areas 205 * which are not mapped in every page-table in the system, causing an 206 * unhandled page-fault when they are accessed. 207 */ 208 static noinline int vmalloc_fault(unsigned long address) 209 { 210 unsigned long pgd_paddr; 211 pmd_t *pmd_k; 212 pte_t *pte_k; 213 214 /* Make sure we are in vmalloc area: */ 215 if (!(address >= VMALLOC_START && address < VMALLOC_END)) 216 return -1; 217 218 /* 219 * Synchronize this task's top level page-table 220 * with the 'reference' page table. 221 * 222 * Do _not_ use "current" here. We might be inside 223 * an interrupt in the middle of a task switch.. 224 */ 225 pgd_paddr = read_cr3_pa(); 226 pmd_k = vmalloc_sync_one(__va(pgd_paddr), address); 227 if (!pmd_k) 228 return -1; 229 230 if (pmd_large(*pmd_k)) 231 return 0; 232 233 pte_k = pte_offset_kernel(pmd_k, address); 234 if (!pte_present(*pte_k)) 235 return -1; 236 237 return 0; 238 } 239 NOKPROBE_SYMBOL(vmalloc_fault); 240 241 void arch_sync_kernel_mappings(unsigned long start, unsigned long end) 242 { 243 unsigned long addr; 244 245 for (addr = start & PMD_MASK; 246 addr >= TASK_SIZE_MAX && addr < VMALLOC_END; 247 addr += PMD_SIZE) { 248 struct page *page; 249 250 spin_lock(&pgd_lock); 251 list_for_each_entry(page, &pgd_list, lru) { 252 spinlock_t *pgt_lock; 253 254 /* the pgt_lock only for Xen */ 255 pgt_lock = &pgd_page_get_mm(page)->page_table_lock; 256 257 spin_lock(pgt_lock); 258 vmalloc_sync_one(page_address(page), addr); 259 spin_unlock(pgt_lock); 260 } 261 spin_unlock(&pgd_lock); 262 } 263 } 264 265 /* 266 * Did it hit the DOS screen memory VA from vm86 mode? 267 */ 268 static inline void 269 check_v8086_mode(struct pt_regs *regs, unsigned long address, 270 struct task_struct *tsk) 271 { 272 #ifdef CONFIG_VM86 273 unsigned long bit; 274 275 if (!v8086_mode(regs) || !tsk->thread.vm86) 276 return; 277 278 bit = (address - 0xA0000) >> PAGE_SHIFT; 279 if (bit < 32) 280 tsk->thread.vm86->screen_bitmap |= 1 << bit; 281 #endif 282 } 283 284 static bool low_pfn(unsigned long pfn) 285 { 286 return pfn < max_low_pfn; 287 } 288 289 static void dump_pagetable(unsigned long address) 290 { 291 pgd_t *base = __va(read_cr3_pa()); 292 pgd_t *pgd = &base[pgd_index(address)]; 293 p4d_t *p4d; 294 pud_t *pud; 295 pmd_t *pmd; 296 pte_t *pte; 297 298 #ifdef CONFIG_X86_PAE 299 pr_info("*pdpt = %016Lx ", pgd_val(*pgd)); 300 if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd)) 301 goto out; 302 #define pr_pde pr_cont 303 #else 304 #define pr_pde pr_info 305 #endif 306 p4d = p4d_offset(pgd, address); 307 pud = pud_offset(p4d, address); 308 pmd = pmd_offset(pud, address); 309 pr_pde("*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd)); 310 #undef pr_pde 311 312 /* 313 * We must not directly access the pte in the highpte 314 * case if the page table is located in highmem. 315 * And let's rather not kmap-atomic the pte, just in case 316 * it's allocated already: 317 */ 318 if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_large(*pmd)) 319 goto out; 320 321 pte = pte_offset_kernel(pmd, address); 322 pr_cont("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte)); 323 out: 324 pr_cont("\n"); 325 } 326 327 #else /* CONFIG_X86_64: */ 328 329 #ifdef CONFIG_CPU_SUP_AMD 330 static const char errata93_warning[] = 331 KERN_ERR 332 "******* Your BIOS seems to not contain a fix for K8 errata #93\n" 333 "******* Working around it, but it may cause SEGVs or burn power.\n" 334 "******* Please consider a BIOS update.\n" 335 "******* Disabling USB legacy in the BIOS may also help.\n"; 336 #endif 337 338 /* 339 * No vm86 mode in 64-bit mode: 340 */ 341 static inline void 342 check_v8086_mode(struct pt_regs *regs, unsigned long address, 343 struct task_struct *tsk) 344 { 345 } 346 347 static int bad_address(void *p) 348 { 349 unsigned long dummy; 350 351 return get_kernel_nofault(dummy, (unsigned long *)p); 352 } 353 354 static void dump_pagetable(unsigned long address) 355 { 356 pgd_t *base = __va(read_cr3_pa()); 357 pgd_t *pgd = base + pgd_index(address); 358 p4d_t *p4d; 359 pud_t *pud; 360 pmd_t *pmd; 361 pte_t *pte; 362 363 if (bad_address(pgd)) 364 goto bad; 365 366 pr_info("PGD %lx ", pgd_val(*pgd)); 367 368 if (!pgd_present(*pgd)) 369 goto out; 370 371 p4d = p4d_offset(pgd, address); 372 if (bad_address(p4d)) 373 goto bad; 374 375 pr_cont("P4D %lx ", p4d_val(*p4d)); 376 if (!p4d_present(*p4d) || p4d_large(*p4d)) 377 goto out; 378 379 pud = pud_offset(p4d, address); 380 if (bad_address(pud)) 381 goto bad; 382 383 pr_cont("PUD %lx ", pud_val(*pud)); 384 if (!pud_present(*pud) || pud_large(*pud)) 385 goto out; 386 387 pmd = pmd_offset(pud, address); 388 if (bad_address(pmd)) 389 goto bad; 390 391 pr_cont("PMD %lx ", pmd_val(*pmd)); 392 if (!pmd_present(*pmd) || pmd_large(*pmd)) 393 goto out; 394 395 pte = pte_offset_kernel(pmd, address); 396 if (bad_address(pte)) 397 goto bad; 398 399 pr_cont("PTE %lx", pte_val(*pte)); 400 out: 401 pr_cont("\n"); 402 return; 403 bad: 404 pr_info("BAD\n"); 405 } 406 407 #endif /* CONFIG_X86_64 */ 408 409 /* 410 * Workaround for K8 erratum #93 & buggy BIOS. 411 * 412 * BIOS SMM functions are required to use a specific workaround 413 * to avoid corruption of the 64bit RIP register on C stepping K8. 414 * 415 * A lot of BIOS that didn't get tested properly miss this. 416 * 417 * The OS sees this as a page fault with the upper 32bits of RIP cleared. 418 * Try to work around it here. 419 * 420 * Note we only handle faults in kernel here. 421 * Does nothing on 32-bit. 422 */ 423 static int is_errata93(struct pt_regs *regs, unsigned long address) 424 { 425 #if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD) 426 if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD 427 || boot_cpu_data.x86 != 0xf) 428 return 0; 429 430 if (address != regs->ip) 431 return 0; 432 433 if ((address >> 32) != 0) 434 return 0; 435 436 address |= 0xffffffffUL << 32; 437 if ((address >= (u64)_stext && address <= (u64)_etext) || 438 (address >= MODULES_VADDR && address <= MODULES_END)) { 439 printk_once(errata93_warning); 440 regs->ip = address; 441 return 1; 442 } 443 #endif 444 return 0; 445 } 446 447 /* 448 * Work around K8 erratum #100 K8 in compat mode occasionally jumps 449 * to illegal addresses >4GB. 450 * 451 * We catch this in the page fault handler because these addresses 452 * are not reachable. Just detect this case and return. Any code 453 * segment in LDT is compatibility mode. 454 */ 455 static int is_errata100(struct pt_regs *regs, unsigned long address) 456 { 457 #ifdef CONFIG_X86_64 458 if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32)) 459 return 1; 460 #endif 461 return 0; 462 } 463 464 /* Pentium F0 0F C7 C8 bug workaround: */ 465 static int is_f00f_bug(struct pt_regs *regs, unsigned long address) 466 { 467 #ifdef CONFIG_X86_F00F_BUG 468 if (boot_cpu_has_bug(X86_BUG_F00F) && idt_is_f00f_address(address)) { 469 handle_invalid_op(regs); 470 return 1; 471 } 472 #endif 473 return 0; 474 } 475 476 static void show_ldttss(const struct desc_ptr *gdt, const char *name, u16 index) 477 { 478 u32 offset = (index >> 3) * sizeof(struct desc_struct); 479 unsigned long addr; 480 struct ldttss_desc desc; 481 482 if (index == 0) { 483 pr_alert("%s: NULL\n", name); 484 return; 485 } 486 487 if (offset + sizeof(struct ldttss_desc) >= gdt->size) { 488 pr_alert("%s: 0x%hx -- out of bounds\n", name, index); 489 return; 490 } 491 492 if (copy_from_kernel_nofault(&desc, (void *)(gdt->address + offset), 493 sizeof(struct ldttss_desc))) { 494 pr_alert("%s: 0x%hx -- GDT entry is not readable\n", 495 name, index); 496 return; 497 } 498 499 addr = desc.base0 | (desc.base1 << 16) | ((unsigned long)desc.base2 << 24); 500 #ifdef CONFIG_X86_64 501 addr |= ((u64)desc.base3 << 32); 502 #endif 503 pr_alert("%s: 0x%hx -- base=0x%lx limit=0x%x\n", 504 name, index, addr, (desc.limit0 | (desc.limit1 << 16))); 505 } 506 507 static void 508 show_fault_oops(struct pt_regs *regs, unsigned long error_code, unsigned long address) 509 { 510 if (!oops_may_print()) 511 return; 512 513 if (error_code & X86_PF_INSTR) { 514 unsigned int level; 515 pgd_t *pgd; 516 pte_t *pte; 517 518 pgd = __va(read_cr3_pa()); 519 pgd += pgd_index(address); 520 521 pte = lookup_address_in_pgd(pgd, address, &level); 522 523 if (pte && pte_present(*pte) && !pte_exec(*pte)) 524 pr_crit("kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n", 525 from_kuid(&init_user_ns, current_uid())); 526 if (pte && pte_present(*pte) && pte_exec(*pte) && 527 (pgd_flags(*pgd) & _PAGE_USER) && 528 (__read_cr4() & X86_CR4_SMEP)) 529 pr_crit("unable to execute userspace code (SMEP?) (uid: %d)\n", 530 from_kuid(&init_user_ns, current_uid())); 531 } 532 533 if (address < PAGE_SIZE && !user_mode(regs)) 534 pr_alert("BUG: kernel NULL pointer dereference, address: %px\n", 535 (void *)address); 536 else 537 pr_alert("BUG: unable to handle page fault for address: %px\n", 538 (void *)address); 539 540 pr_alert("#PF: %s %s in %s mode\n", 541 (error_code & X86_PF_USER) ? "user" : "supervisor", 542 (error_code & X86_PF_INSTR) ? "instruction fetch" : 543 (error_code & X86_PF_WRITE) ? "write access" : 544 "read access", 545 user_mode(regs) ? "user" : "kernel"); 546 pr_alert("#PF: error_code(0x%04lx) - %s\n", error_code, 547 !(error_code & X86_PF_PROT) ? "not-present page" : 548 (error_code & X86_PF_RSVD) ? "reserved bit violation" : 549 (error_code & X86_PF_PK) ? "protection keys violation" : 550 "permissions violation"); 551 552 if (!(error_code & X86_PF_USER) && user_mode(regs)) { 553 struct desc_ptr idt, gdt; 554 u16 ldtr, tr; 555 556 /* 557 * This can happen for quite a few reasons. The more obvious 558 * ones are faults accessing the GDT, or LDT. Perhaps 559 * surprisingly, if the CPU tries to deliver a benign or 560 * contributory exception from user code and gets a page fault 561 * during delivery, the page fault can be delivered as though 562 * it originated directly from user code. This could happen 563 * due to wrong permissions on the IDT, GDT, LDT, TSS, or 564 * kernel or IST stack. 565 */ 566 store_idt(&idt); 567 568 /* Usable even on Xen PV -- it's just slow. */ 569 native_store_gdt(&gdt); 570 571 pr_alert("IDT: 0x%lx (limit=0x%hx) GDT: 0x%lx (limit=0x%hx)\n", 572 idt.address, idt.size, gdt.address, gdt.size); 573 574 store_ldt(ldtr); 575 show_ldttss(&gdt, "LDTR", ldtr); 576 577 store_tr(tr); 578 show_ldttss(&gdt, "TR", tr); 579 } 580 581 dump_pagetable(address); 582 } 583 584 static noinline void 585 pgtable_bad(struct pt_regs *regs, unsigned long error_code, 586 unsigned long address) 587 { 588 struct task_struct *tsk; 589 unsigned long flags; 590 int sig; 591 592 flags = oops_begin(); 593 tsk = current; 594 sig = SIGKILL; 595 596 printk(KERN_ALERT "%s: Corrupted page table at address %lx\n", 597 tsk->comm, address); 598 dump_pagetable(address); 599 600 if (__die("Bad pagetable", regs, error_code)) 601 sig = 0; 602 603 oops_end(flags, regs, sig); 604 } 605 606 static void sanitize_error_code(unsigned long address, 607 unsigned long *error_code) 608 { 609 /* 610 * To avoid leaking information about the kernel page 611 * table layout, pretend that user-mode accesses to 612 * kernel addresses are always protection faults. 613 * 614 * NB: This means that failed vsyscalls with vsyscall=none 615 * will have the PROT bit. This doesn't leak any 616 * information and does not appear to cause any problems. 617 */ 618 if (address >= TASK_SIZE_MAX) 619 *error_code |= X86_PF_PROT; 620 } 621 622 static void set_signal_archinfo(unsigned long address, 623 unsigned long error_code) 624 { 625 struct task_struct *tsk = current; 626 627 tsk->thread.trap_nr = X86_TRAP_PF; 628 tsk->thread.error_code = error_code | X86_PF_USER; 629 tsk->thread.cr2 = address; 630 } 631 632 static noinline void 633 no_context(struct pt_regs *regs, unsigned long error_code, 634 unsigned long address, int signal, int si_code) 635 { 636 struct task_struct *tsk = current; 637 unsigned long flags; 638 int sig; 639 640 if (user_mode(regs)) { 641 /* 642 * This is an implicit supervisor-mode access from user 643 * mode. Bypass all the kernel-mode recovery code and just 644 * OOPS. 645 */ 646 goto oops; 647 } 648 649 /* Are we prepared to handle this kernel fault? */ 650 if (fixup_exception(regs, X86_TRAP_PF, error_code, address)) { 651 /* 652 * Any interrupt that takes a fault gets the fixup. This makes 653 * the below recursive fault logic only apply to a faults from 654 * task context. 655 */ 656 if (in_interrupt()) 657 return; 658 659 /* 660 * Per the above we're !in_interrupt(), aka. task context. 661 * 662 * In this case we need to make sure we're not recursively 663 * faulting through the emulate_vsyscall() logic. 664 */ 665 if (current->thread.sig_on_uaccess_err && signal) { 666 sanitize_error_code(address, &error_code); 667 668 set_signal_archinfo(address, error_code); 669 670 /* XXX: hwpoison faults will set the wrong code. */ 671 force_sig_fault(signal, si_code, (void __user *)address); 672 } 673 674 /* 675 * Barring that, we can do the fixup and be happy. 676 */ 677 return; 678 } 679 680 #ifdef CONFIG_VMAP_STACK 681 /* 682 * Stack overflow? During boot, we can fault near the initial 683 * stack in the direct map, but that's not an overflow -- check 684 * that we're in vmalloc space to avoid this. 685 */ 686 if (is_vmalloc_addr((void *)address) && 687 (((unsigned long)tsk->stack - 1 - address < PAGE_SIZE) || 688 address - ((unsigned long)tsk->stack + THREAD_SIZE) < PAGE_SIZE)) { 689 unsigned long stack = __this_cpu_ist_top_va(DF) - sizeof(void *); 690 /* 691 * We're likely to be running with very little stack space 692 * left. It's plausible that we'd hit this condition but 693 * double-fault even before we get this far, in which case 694 * we're fine: the double-fault handler will deal with it. 695 * 696 * We don't want to make it all the way into the oops code 697 * and then double-fault, though, because we're likely to 698 * break the console driver and lose most of the stack dump. 699 */ 700 asm volatile ("movq %[stack], %%rsp\n\t" 701 "call handle_stack_overflow\n\t" 702 "1: jmp 1b" 703 : ASM_CALL_CONSTRAINT 704 : "D" ("kernel stack overflow (page fault)"), 705 "S" (regs), "d" (address), 706 [stack] "rm" (stack)); 707 unreachable(); 708 } 709 #endif 710 711 /* 712 * 32-bit: 713 * 714 * Valid to do another page fault here, because if this fault 715 * had been triggered by is_prefetch fixup_exception would have 716 * handled it. 717 * 718 * 64-bit: 719 * 720 * Hall of shame of CPU/BIOS bugs. 721 */ 722 if (is_prefetch(regs, error_code, address)) 723 return; 724 725 if (is_errata93(regs, address)) 726 return; 727 728 /* 729 * Buggy firmware could access regions which might page fault, try to 730 * recover from such faults. 731 */ 732 if (IS_ENABLED(CONFIG_EFI)) 733 efi_recover_from_page_fault(address); 734 735 oops: 736 /* 737 * Oops. The kernel tried to access some bad page. We'll have to 738 * terminate things with extreme prejudice: 739 */ 740 flags = oops_begin(); 741 742 show_fault_oops(regs, error_code, address); 743 744 if (task_stack_end_corrupted(tsk)) 745 printk(KERN_EMERG "Thread overran stack, or stack corrupted\n"); 746 747 sig = SIGKILL; 748 if (__die("Oops", regs, error_code)) 749 sig = 0; 750 751 /* Executive summary in case the body of the oops scrolled away */ 752 printk(KERN_DEFAULT "CR2: %016lx\n", address); 753 754 oops_end(flags, regs, sig); 755 } 756 757 /* 758 * Print out info about fatal segfaults, if the show_unhandled_signals 759 * sysctl is set: 760 */ 761 static inline void 762 show_signal_msg(struct pt_regs *regs, unsigned long error_code, 763 unsigned long address, struct task_struct *tsk) 764 { 765 const char *loglvl = task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG; 766 767 if (!unhandled_signal(tsk, SIGSEGV)) 768 return; 769 770 if (!printk_ratelimit()) 771 return; 772 773 printk("%s%s[%d]: segfault at %lx ip %px sp %px error %lx", 774 loglvl, tsk->comm, task_pid_nr(tsk), address, 775 (void *)regs->ip, (void *)regs->sp, error_code); 776 777 print_vma_addr(KERN_CONT " in ", regs->ip); 778 779 printk(KERN_CONT "\n"); 780 781 show_opcodes(regs, loglvl); 782 } 783 784 /* 785 * The (legacy) vsyscall page is the long page in the kernel portion 786 * of the address space that has user-accessible permissions. 787 */ 788 static bool is_vsyscall_vaddr(unsigned long vaddr) 789 { 790 return unlikely((vaddr & PAGE_MASK) == VSYSCALL_ADDR); 791 } 792 793 static void 794 __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code, 795 unsigned long address, u32 pkey, int si_code) 796 { 797 struct task_struct *tsk = current; 798 799 /* User mode accesses just cause a SIGSEGV */ 800 if (user_mode(regs) && (error_code & X86_PF_USER)) { 801 /* 802 * It's possible to have interrupts off here: 803 */ 804 local_irq_enable(); 805 806 /* 807 * Valid to do another page fault here because this one came 808 * from user space: 809 */ 810 if (is_prefetch(regs, error_code, address)) 811 return; 812 813 if (is_errata100(regs, address)) 814 return; 815 816 sanitize_error_code(address, &error_code); 817 818 if (fixup_vdso_exception(regs, X86_TRAP_PF, error_code, address)) 819 return; 820 821 if (likely(show_unhandled_signals)) 822 show_signal_msg(regs, error_code, address, tsk); 823 824 set_signal_archinfo(address, error_code); 825 826 if (si_code == SEGV_PKUERR) 827 force_sig_pkuerr((void __user *)address, pkey); 828 829 force_sig_fault(SIGSEGV, si_code, (void __user *)address); 830 831 local_irq_disable(); 832 833 return; 834 } 835 836 if (is_f00f_bug(regs, address)) 837 return; 838 839 no_context(regs, error_code, address, SIGSEGV, si_code); 840 } 841 842 static noinline void 843 bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code, 844 unsigned long address) 845 { 846 __bad_area_nosemaphore(regs, error_code, address, 0, SEGV_MAPERR); 847 } 848 849 static void 850 __bad_area(struct pt_regs *regs, unsigned long error_code, 851 unsigned long address, u32 pkey, int si_code) 852 { 853 struct mm_struct *mm = current->mm; 854 /* 855 * Something tried to access memory that isn't in our memory map.. 856 * Fix it, but check if it's kernel or user first.. 857 */ 858 mmap_read_unlock(mm); 859 860 __bad_area_nosemaphore(regs, error_code, address, pkey, si_code); 861 } 862 863 static noinline void 864 bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address) 865 { 866 __bad_area(regs, error_code, address, 0, SEGV_MAPERR); 867 } 868 869 static inline bool bad_area_access_from_pkeys(unsigned long error_code, 870 struct vm_area_struct *vma) 871 { 872 /* This code is always called on the current mm */ 873 bool foreign = false; 874 875 if (!boot_cpu_has(X86_FEATURE_OSPKE)) 876 return false; 877 if (error_code & X86_PF_PK) 878 return true; 879 /* this checks permission keys on the VMA: */ 880 if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE), 881 (error_code & X86_PF_INSTR), foreign)) 882 return true; 883 return false; 884 } 885 886 static noinline void 887 bad_area_access_error(struct pt_regs *regs, unsigned long error_code, 888 unsigned long address, struct vm_area_struct *vma) 889 { 890 /* 891 * This OSPKE check is not strictly necessary at runtime. 892 * But, doing it this way allows compiler optimizations 893 * if pkeys are compiled out. 894 */ 895 if (bad_area_access_from_pkeys(error_code, vma)) { 896 /* 897 * A protection key fault means that the PKRU value did not allow 898 * access to some PTE. Userspace can figure out what PKRU was 899 * from the XSAVE state. This function captures the pkey from 900 * the vma and passes it to userspace so userspace can discover 901 * which protection key was set on the PTE. 902 * 903 * If we get here, we know that the hardware signaled a X86_PF_PK 904 * fault and that there was a VMA once we got in the fault 905 * handler. It does *not* guarantee that the VMA we find here 906 * was the one that we faulted on. 907 * 908 * 1. T1 : mprotect_key(foo, PAGE_SIZE, pkey=4); 909 * 2. T1 : set PKRU to deny access to pkey=4, touches page 910 * 3. T1 : faults... 911 * 4. T2: mprotect_key(foo, PAGE_SIZE, pkey=5); 912 * 5. T1 : enters fault handler, takes mmap_lock, etc... 913 * 6. T1 : reaches here, sees vma_pkey(vma)=5, when we really 914 * faulted on a pte with its pkey=4. 915 */ 916 u32 pkey = vma_pkey(vma); 917 918 __bad_area(regs, error_code, address, pkey, SEGV_PKUERR); 919 } else { 920 __bad_area(regs, error_code, address, 0, SEGV_ACCERR); 921 } 922 } 923 924 static void 925 do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address, 926 vm_fault_t fault) 927 { 928 /* Kernel mode? Handle exceptions or die: */ 929 if (!(error_code & X86_PF_USER)) { 930 no_context(regs, error_code, address, SIGBUS, BUS_ADRERR); 931 return; 932 } 933 934 /* User-space => ok to do another page fault: */ 935 if (is_prefetch(regs, error_code, address)) 936 return; 937 938 sanitize_error_code(address, &error_code); 939 940 if (fixup_vdso_exception(regs, X86_TRAP_PF, error_code, address)) 941 return; 942 943 set_signal_archinfo(address, error_code); 944 945 #ifdef CONFIG_MEMORY_FAILURE 946 if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) { 947 struct task_struct *tsk = current; 948 unsigned lsb = 0; 949 950 pr_err( 951 "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n", 952 tsk->comm, tsk->pid, address); 953 if (fault & VM_FAULT_HWPOISON_LARGE) 954 lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault)); 955 if (fault & VM_FAULT_HWPOISON) 956 lsb = PAGE_SHIFT; 957 force_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb); 958 return; 959 } 960 #endif 961 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address); 962 } 963 964 static noinline void 965 mm_fault_error(struct pt_regs *regs, unsigned long error_code, 966 unsigned long address, vm_fault_t fault) 967 { 968 if (fatal_signal_pending(current) && !(error_code & X86_PF_USER)) { 969 no_context(regs, error_code, address, 0, 0); 970 return; 971 } 972 973 if (fault & VM_FAULT_OOM) { 974 /* Kernel mode? Handle exceptions or die: */ 975 if (!(error_code & X86_PF_USER)) { 976 no_context(regs, error_code, address, 977 SIGSEGV, SEGV_MAPERR); 978 return; 979 } 980 981 /* 982 * We ran out of memory, call the OOM killer, and return the 983 * userspace (which will retry the fault, or kill us if we got 984 * oom-killed): 985 */ 986 pagefault_out_of_memory(); 987 } else { 988 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON| 989 VM_FAULT_HWPOISON_LARGE)) 990 do_sigbus(regs, error_code, address, fault); 991 else if (fault & VM_FAULT_SIGSEGV) 992 bad_area_nosemaphore(regs, error_code, address); 993 else 994 BUG(); 995 } 996 } 997 998 static int spurious_kernel_fault_check(unsigned long error_code, pte_t *pte) 999 { 1000 if ((error_code & X86_PF_WRITE) && !pte_write(*pte)) 1001 return 0; 1002 1003 if ((error_code & X86_PF_INSTR) && !pte_exec(*pte)) 1004 return 0; 1005 1006 return 1; 1007 } 1008 1009 /* 1010 * Handle a spurious fault caused by a stale TLB entry. 1011 * 1012 * This allows us to lazily refresh the TLB when increasing the 1013 * permissions of a kernel page (RO -> RW or NX -> X). Doing it 1014 * eagerly is very expensive since that implies doing a full 1015 * cross-processor TLB flush, even if no stale TLB entries exist 1016 * on other processors. 1017 * 1018 * Spurious faults may only occur if the TLB contains an entry with 1019 * fewer permission than the page table entry. Non-present (P = 0) 1020 * and reserved bit (R = 1) faults are never spurious. 1021 * 1022 * There are no security implications to leaving a stale TLB when 1023 * increasing the permissions on a page. 1024 * 1025 * Returns non-zero if a spurious fault was handled, zero otherwise. 1026 * 1027 * See Intel Developer's Manual Vol 3 Section 4.10.4.3, bullet 3 1028 * (Optional Invalidation). 1029 */ 1030 static noinline int 1031 spurious_kernel_fault(unsigned long error_code, unsigned long address) 1032 { 1033 pgd_t *pgd; 1034 p4d_t *p4d; 1035 pud_t *pud; 1036 pmd_t *pmd; 1037 pte_t *pte; 1038 int ret; 1039 1040 /* 1041 * Only writes to RO or instruction fetches from NX may cause 1042 * spurious faults. 1043 * 1044 * These could be from user or supervisor accesses but the TLB 1045 * is only lazily flushed after a kernel mapping protection 1046 * change, so user accesses are not expected to cause spurious 1047 * faults. 1048 */ 1049 if (error_code != (X86_PF_WRITE | X86_PF_PROT) && 1050 error_code != (X86_PF_INSTR | X86_PF_PROT)) 1051 return 0; 1052 1053 pgd = init_mm.pgd + pgd_index(address); 1054 if (!pgd_present(*pgd)) 1055 return 0; 1056 1057 p4d = p4d_offset(pgd, address); 1058 if (!p4d_present(*p4d)) 1059 return 0; 1060 1061 if (p4d_large(*p4d)) 1062 return spurious_kernel_fault_check(error_code, (pte_t *) p4d); 1063 1064 pud = pud_offset(p4d, address); 1065 if (!pud_present(*pud)) 1066 return 0; 1067 1068 if (pud_large(*pud)) 1069 return spurious_kernel_fault_check(error_code, (pte_t *) pud); 1070 1071 pmd = pmd_offset(pud, address); 1072 if (!pmd_present(*pmd)) 1073 return 0; 1074 1075 if (pmd_large(*pmd)) 1076 return spurious_kernel_fault_check(error_code, (pte_t *) pmd); 1077 1078 pte = pte_offset_kernel(pmd, address); 1079 if (!pte_present(*pte)) 1080 return 0; 1081 1082 ret = spurious_kernel_fault_check(error_code, pte); 1083 if (!ret) 1084 return 0; 1085 1086 /* 1087 * Make sure we have permissions in PMD. 1088 * If not, then there's a bug in the page tables: 1089 */ 1090 ret = spurious_kernel_fault_check(error_code, (pte_t *) pmd); 1091 WARN_ONCE(!ret, "PMD has incorrect permission bits\n"); 1092 1093 return ret; 1094 } 1095 NOKPROBE_SYMBOL(spurious_kernel_fault); 1096 1097 int show_unhandled_signals = 1; 1098 1099 static inline int 1100 access_error(unsigned long error_code, struct vm_area_struct *vma) 1101 { 1102 /* This is only called for the current mm, so: */ 1103 bool foreign = false; 1104 1105 /* 1106 * Read or write was blocked by protection keys. This is 1107 * always an unconditional error and can never result in 1108 * a follow-up action to resolve the fault, like a COW. 1109 */ 1110 if (error_code & X86_PF_PK) 1111 return 1; 1112 1113 /* 1114 * SGX hardware blocked the access. This usually happens 1115 * when the enclave memory contents have been destroyed, like 1116 * after a suspend/resume cycle. In any case, the kernel can't 1117 * fix the cause of the fault. Handle the fault as an access 1118 * error even in cases where no actual access violation 1119 * occurred. This allows userspace to rebuild the enclave in 1120 * response to the signal. 1121 */ 1122 if (unlikely(error_code & X86_PF_SGX)) 1123 return 1; 1124 1125 /* 1126 * Make sure to check the VMA so that we do not perform 1127 * faults just to hit a X86_PF_PK as soon as we fill in a 1128 * page. 1129 */ 1130 if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE), 1131 (error_code & X86_PF_INSTR), foreign)) 1132 return 1; 1133 1134 if (error_code & X86_PF_WRITE) { 1135 /* write, present and write, not present: */ 1136 if (unlikely(!(vma->vm_flags & VM_WRITE))) 1137 return 1; 1138 return 0; 1139 } 1140 1141 /* read, present: */ 1142 if (unlikely(error_code & X86_PF_PROT)) 1143 return 1; 1144 1145 /* read, not present: */ 1146 if (unlikely(!vma_is_accessible(vma))) 1147 return 1; 1148 1149 return 0; 1150 } 1151 1152 bool fault_in_kernel_space(unsigned long address) 1153 { 1154 /* 1155 * On 64-bit systems, the vsyscall page is at an address above 1156 * TASK_SIZE_MAX, but is not considered part of the kernel 1157 * address space. 1158 */ 1159 if (IS_ENABLED(CONFIG_X86_64) && is_vsyscall_vaddr(address)) 1160 return false; 1161 1162 return address >= TASK_SIZE_MAX; 1163 } 1164 1165 /* 1166 * Called for all faults where 'address' is part of the kernel address 1167 * space. Might get called for faults that originate from *code* that 1168 * ran in userspace or the kernel. 1169 */ 1170 static void 1171 do_kern_addr_fault(struct pt_regs *regs, unsigned long hw_error_code, 1172 unsigned long address) 1173 { 1174 /* 1175 * Protection keys exceptions only happen on user pages. We 1176 * have no user pages in the kernel portion of the address 1177 * space, so do not expect them here. 1178 */ 1179 WARN_ON_ONCE(hw_error_code & X86_PF_PK); 1180 1181 #ifdef CONFIG_X86_32 1182 /* 1183 * We can fault-in kernel-space virtual memory on-demand. The 1184 * 'reference' page table is init_mm.pgd. 1185 * 1186 * NOTE! We MUST NOT take any locks for this case. We may 1187 * be in an interrupt or a critical region, and should 1188 * only copy the information from the master page table, 1189 * nothing more. 1190 * 1191 * Before doing this on-demand faulting, ensure that the 1192 * fault is not any of the following: 1193 * 1. A fault on a PTE with a reserved bit set. 1194 * 2. A fault caused by a user-mode access. (Do not demand- 1195 * fault kernel memory due to user-mode accesses). 1196 * 3. A fault caused by a page-level protection violation. 1197 * (A demand fault would be on a non-present page which 1198 * would have X86_PF_PROT==0). 1199 * 1200 * This is only needed to close a race condition on x86-32 in 1201 * the vmalloc mapping/unmapping code. See the comment above 1202 * vmalloc_fault() for details. On x86-64 the race does not 1203 * exist as the vmalloc mappings don't need to be synchronized 1204 * there. 1205 */ 1206 if (!(hw_error_code & (X86_PF_RSVD | X86_PF_USER | X86_PF_PROT))) { 1207 if (vmalloc_fault(address) >= 0) 1208 return; 1209 } 1210 #endif 1211 1212 /* Was the fault spurious, caused by lazy TLB invalidation? */ 1213 if (spurious_kernel_fault(hw_error_code, address)) 1214 return; 1215 1216 /* kprobes don't want to hook the spurious faults: */ 1217 if (kprobe_page_fault(regs, X86_TRAP_PF)) 1218 return; 1219 1220 /* 1221 * Note, despite being a "bad area", there are quite a few 1222 * acceptable reasons to get here, such as erratum fixups 1223 * and handling kernel code that can fault, like get_user(). 1224 * 1225 * Don't take the mm semaphore here. If we fixup a prefetch 1226 * fault we could otherwise deadlock: 1227 */ 1228 bad_area_nosemaphore(regs, hw_error_code, address); 1229 } 1230 NOKPROBE_SYMBOL(do_kern_addr_fault); 1231 1232 /* Handle faults in the user portion of the address space */ 1233 static inline 1234 void do_user_addr_fault(struct pt_regs *regs, 1235 unsigned long hw_error_code, 1236 unsigned long address) 1237 { 1238 struct vm_area_struct *vma; 1239 struct task_struct *tsk; 1240 struct mm_struct *mm; 1241 vm_fault_t fault; 1242 unsigned int flags = FAULT_FLAG_DEFAULT; 1243 1244 tsk = current; 1245 mm = tsk->mm; 1246 1247 /* kprobes don't want to hook the spurious faults: */ 1248 if (unlikely(kprobe_page_fault(regs, X86_TRAP_PF))) 1249 return; 1250 1251 /* 1252 * Reserved bits are never expected to be set on 1253 * entries in the user portion of the page tables. 1254 */ 1255 if (unlikely(hw_error_code & X86_PF_RSVD)) 1256 pgtable_bad(regs, hw_error_code, address); 1257 1258 /* 1259 * If SMAP is on, check for invalid kernel (supervisor) access to user 1260 * pages in the user address space. The odd case here is WRUSS, 1261 * which, according to the preliminary documentation, does not respect 1262 * SMAP and will have the USER bit set so, in all cases, SMAP 1263 * enforcement appears to be consistent with the USER bit. 1264 */ 1265 if (unlikely(cpu_feature_enabled(X86_FEATURE_SMAP) && 1266 !(hw_error_code & X86_PF_USER) && 1267 !(regs->flags & X86_EFLAGS_AC))) 1268 { 1269 bad_area_nosemaphore(regs, hw_error_code, address); 1270 return; 1271 } 1272 1273 /* 1274 * If we're in an interrupt, have no user context or are running 1275 * in a region with pagefaults disabled then we must not take the fault 1276 */ 1277 if (unlikely(faulthandler_disabled() || !mm)) { 1278 bad_area_nosemaphore(regs, hw_error_code, address); 1279 return; 1280 } 1281 1282 /* 1283 * It's safe to allow irq's after cr2 has been saved and the 1284 * vmalloc fault has been handled. 1285 * 1286 * User-mode registers count as a user access even for any 1287 * potential system fault or CPU buglet: 1288 */ 1289 if (user_mode(regs)) { 1290 local_irq_enable(); 1291 flags |= FAULT_FLAG_USER; 1292 } else { 1293 if (regs->flags & X86_EFLAGS_IF) 1294 local_irq_enable(); 1295 } 1296 1297 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 1298 1299 if (hw_error_code & X86_PF_WRITE) 1300 flags |= FAULT_FLAG_WRITE; 1301 if (hw_error_code & X86_PF_INSTR) 1302 flags |= FAULT_FLAG_INSTRUCTION; 1303 1304 #ifdef CONFIG_X86_64 1305 /* 1306 * Faults in the vsyscall page might need emulation. The 1307 * vsyscall page is at a high address (>PAGE_OFFSET), but is 1308 * considered to be part of the user address space. 1309 * 1310 * The vsyscall page does not have a "real" VMA, so do this 1311 * emulation before we go searching for VMAs. 1312 * 1313 * PKRU never rejects instruction fetches, so we don't need 1314 * to consider the PF_PK bit. 1315 */ 1316 if (is_vsyscall_vaddr(address)) { 1317 if (emulate_vsyscall(hw_error_code, regs, address)) 1318 return; 1319 } 1320 #endif 1321 1322 /* 1323 * Kernel-mode access to the user address space should only occur 1324 * on well-defined single instructions listed in the exception 1325 * tables. But, an erroneous kernel fault occurring outside one of 1326 * those areas which also holds mmap_lock might deadlock attempting 1327 * to validate the fault against the address space. 1328 * 1329 * Only do the expensive exception table search when we might be at 1330 * risk of a deadlock. This happens if we 1331 * 1. Failed to acquire mmap_lock, and 1332 * 2. The access did not originate in userspace. 1333 */ 1334 if (unlikely(!mmap_read_trylock(mm))) { 1335 if (!user_mode(regs) && !search_exception_tables(regs->ip)) { 1336 /* 1337 * Fault from code in kernel from 1338 * which we do not expect faults. 1339 */ 1340 bad_area_nosemaphore(regs, hw_error_code, address); 1341 return; 1342 } 1343 retry: 1344 mmap_read_lock(mm); 1345 } else { 1346 /* 1347 * The above down_read_trylock() might have succeeded in 1348 * which case we'll have missed the might_sleep() from 1349 * down_read(): 1350 */ 1351 might_sleep(); 1352 } 1353 1354 vma = find_vma(mm, address); 1355 if (unlikely(!vma)) { 1356 bad_area(regs, hw_error_code, address); 1357 return; 1358 } 1359 if (likely(vma->vm_start <= address)) 1360 goto good_area; 1361 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) { 1362 bad_area(regs, hw_error_code, address); 1363 return; 1364 } 1365 if (unlikely(expand_stack(vma, address))) { 1366 bad_area(regs, hw_error_code, address); 1367 return; 1368 } 1369 1370 /* 1371 * Ok, we have a good vm_area for this memory access, so 1372 * we can handle it.. 1373 */ 1374 good_area: 1375 if (unlikely(access_error(hw_error_code, vma))) { 1376 bad_area_access_error(regs, hw_error_code, address, vma); 1377 return; 1378 } 1379 1380 /* 1381 * If for any reason at all we couldn't handle the fault, 1382 * make sure we exit gracefully rather than endlessly redo 1383 * the fault. Since we never set FAULT_FLAG_RETRY_NOWAIT, if 1384 * we get VM_FAULT_RETRY back, the mmap_lock has been unlocked. 1385 * 1386 * Note that handle_userfault() may also release and reacquire mmap_lock 1387 * (and not return with VM_FAULT_RETRY), when returning to userland to 1388 * repeat the page fault later with a VM_FAULT_NOPAGE retval 1389 * (potentially after handling any pending signal during the return to 1390 * userland). The return to userland is identified whenever 1391 * FAULT_FLAG_USER|FAULT_FLAG_KILLABLE are both set in flags. 1392 */ 1393 fault = handle_mm_fault(vma, address, flags, regs); 1394 1395 /* Quick path to respond to signals */ 1396 if (fault_signal_pending(fault, regs)) { 1397 if (!user_mode(regs)) 1398 no_context(regs, hw_error_code, address, SIGBUS, 1399 BUS_ADRERR); 1400 return; 1401 } 1402 1403 /* 1404 * If we need to retry the mmap_lock has already been released, 1405 * and if there is a fatal signal pending there is no guarantee 1406 * that we made any progress. Handle this case first. 1407 */ 1408 if (unlikely((fault & VM_FAULT_RETRY) && 1409 (flags & FAULT_FLAG_ALLOW_RETRY))) { 1410 flags |= FAULT_FLAG_TRIED; 1411 goto retry; 1412 } 1413 1414 mmap_read_unlock(mm); 1415 if (unlikely(fault & VM_FAULT_ERROR)) { 1416 mm_fault_error(regs, hw_error_code, address, fault); 1417 return; 1418 } 1419 1420 check_v8086_mode(regs, address, tsk); 1421 } 1422 NOKPROBE_SYMBOL(do_user_addr_fault); 1423 1424 static __always_inline void 1425 trace_page_fault_entries(struct pt_regs *regs, unsigned long error_code, 1426 unsigned long address) 1427 { 1428 if (!trace_pagefault_enabled()) 1429 return; 1430 1431 if (user_mode(regs)) 1432 trace_page_fault_user(address, regs, error_code); 1433 else 1434 trace_page_fault_kernel(address, regs, error_code); 1435 } 1436 1437 static __always_inline void 1438 handle_page_fault(struct pt_regs *regs, unsigned long error_code, 1439 unsigned long address) 1440 { 1441 trace_page_fault_entries(regs, error_code, address); 1442 1443 if (unlikely(kmmio_fault(regs, address))) 1444 return; 1445 1446 /* Was the fault on kernel-controlled part of the address space? */ 1447 if (unlikely(fault_in_kernel_space(address))) { 1448 do_kern_addr_fault(regs, error_code, address); 1449 } else { 1450 do_user_addr_fault(regs, error_code, address); 1451 /* 1452 * User address page fault handling might have reenabled 1453 * interrupts. Fixing up all potential exit points of 1454 * do_user_addr_fault() and its leaf functions is just not 1455 * doable w/o creating an unholy mess or turning the code 1456 * upside down. 1457 */ 1458 local_irq_disable(); 1459 } 1460 } 1461 1462 DEFINE_IDTENTRY_RAW_ERRORCODE(exc_page_fault) 1463 { 1464 unsigned long address = read_cr2(); 1465 irqentry_state_t state; 1466 1467 prefetchw(¤t->mm->mmap_lock); 1468 1469 /* 1470 * KVM uses #PF vector to deliver 'page not present' events to guests 1471 * (asynchronous page fault mechanism). The event happens when a 1472 * userspace task is trying to access some valid (from guest's point of 1473 * view) memory which is not currently mapped by the host (e.g. the 1474 * memory is swapped out). Note, the corresponding "page ready" event 1475 * which is injected when the memory becomes available, is delived via 1476 * an interrupt mechanism and not a #PF exception 1477 * (see arch/x86/kernel/kvm.c: sysvec_kvm_asyncpf_interrupt()). 1478 * 1479 * We are relying on the interrupted context being sane (valid RSP, 1480 * relevant locks not held, etc.), which is fine as long as the 1481 * interrupted context had IF=1. We are also relying on the KVM 1482 * async pf type field and CR2 being read consistently instead of 1483 * getting values from real and async page faults mixed up. 1484 * 1485 * Fingers crossed. 1486 * 1487 * The async #PF handling code takes care of idtentry handling 1488 * itself. 1489 */ 1490 if (kvm_handle_async_pf(regs, (u32)address)) 1491 return; 1492 1493 /* 1494 * Entry handling for valid #PF from kernel mode is slightly 1495 * different: RCU is already watching and rcu_irq_enter() must not 1496 * be invoked because a kernel fault on a user space address might 1497 * sleep. 1498 * 1499 * In case the fault hit a RCU idle region the conditional entry 1500 * code reenabled RCU to avoid subsequent wreckage which helps 1501 * debugability. 1502 */ 1503 state = irqentry_enter(regs); 1504 1505 instrumentation_begin(); 1506 handle_page_fault(regs, error_code, address); 1507 instrumentation_end(); 1508 1509 irqentry_exit(regs, state); 1510 } 1511