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 33 #define CREATE_TRACE_POINTS 34 #include <asm/trace/exceptions.h> 35 36 /* 37 * Returns 0 if mmiotrace is disabled, or if the fault is not 38 * handled by mmiotrace: 39 */ 40 static nokprobe_inline int 41 kmmio_fault(struct pt_regs *regs, unsigned long addr) 42 { 43 if (unlikely(is_kmmio_active())) 44 if (kmmio_handler(regs, addr) == 1) 45 return -1; 46 return 0; 47 } 48 49 /* 50 * Prefetch quirks: 51 * 52 * 32-bit mode: 53 * 54 * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch. 55 * Check that here and ignore it. 56 * 57 * 64-bit mode: 58 * 59 * Sometimes the CPU reports invalid exceptions on prefetch. 60 * Check that here and ignore it. 61 * 62 * Opcode checker based on code by Richard Brunner. 63 */ 64 static inline int 65 check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr, 66 unsigned char opcode, int *prefetch) 67 { 68 unsigned char instr_hi = opcode & 0xf0; 69 unsigned char instr_lo = opcode & 0x0f; 70 71 switch (instr_hi) { 72 case 0x20: 73 case 0x30: 74 /* 75 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes. 76 * In X86_64 long mode, the CPU will signal invalid 77 * opcode if some of these prefixes are present so 78 * X86_64 will never get here anyway 79 */ 80 return ((instr_lo & 7) == 0x6); 81 #ifdef CONFIG_X86_64 82 case 0x40: 83 /* 84 * In AMD64 long mode 0x40..0x4F are valid REX prefixes 85 * Need to figure out under what instruction mode the 86 * instruction was issued. Could check the LDT for lm, 87 * but for now it's good enough to assume that long 88 * mode only uses well known segments or kernel. 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 (probe_kernel_address(instr, opcode)) 101 return 0; 102 103 *prefetch = (instr_lo == 0xF) && 104 (opcode == 0x0D || opcode == 0x18); 105 return 0; 106 default: 107 return 0; 108 } 109 } 110 111 static int 112 is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr) 113 { 114 unsigned char *max_instr; 115 unsigned char *instr; 116 int prefetch = 0; 117 118 /* 119 * If it was a exec (instruction fetch) fault on NX page, then 120 * do not ignore the fault: 121 */ 122 if (error_code & X86_PF_INSTR) 123 return 0; 124 125 instr = (void *)convert_ip_to_linear(current, regs); 126 max_instr = instr + 15; 127 128 if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE_MAX) 129 return 0; 130 131 while (instr < max_instr) { 132 unsigned char opcode; 133 134 if (probe_kernel_address(instr, opcode)) 135 break; 136 137 instr++; 138 139 if (!check_prefetch_opcode(regs, instr, opcode, &prefetch)) 140 break; 141 } 142 return prefetch; 143 } 144 145 DEFINE_SPINLOCK(pgd_lock); 146 LIST_HEAD(pgd_list); 147 148 #ifdef CONFIG_X86_32 149 static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address) 150 { 151 unsigned index = pgd_index(address); 152 pgd_t *pgd_k; 153 p4d_t *p4d, *p4d_k; 154 pud_t *pud, *pud_k; 155 pmd_t *pmd, *pmd_k; 156 157 pgd += index; 158 pgd_k = init_mm.pgd + index; 159 160 if (!pgd_present(*pgd_k)) 161 return NULL; 162 163 /* 164 * set_pgd(pgd, *pgd_k); here would be useless on PAE 165 * and redundant with the set_pmd() on non-PAE. As would 166 * set_p4d/set_pud. 167 */ 168 p4d = p4d_offset(pgd, address); 169 p4d_k = p4d_offset(pgd_k, address); 170 if (!p4d_present(*p4d_k)) 171 return NULL; 172 173 pud = pud_offset(p4d, address); 174 pud_k = pud_offset(p4d_k, address); 175 if (!pud_present(*pud_k)) 176 return NULL; 177 178 pmd = pmd_offset(pud, address); 179 pmd_k = pmd_offset(pud_k, address); 180 if (!pmd_present(*pmd_k)) 181 return NULL; 182 183 if (!pmd_present(*pmd)) 184 set_pmd(pmd, *pmd_k); 185 else 186 BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k)); 187 188 return pmd_k; 189 } 190 191 void vmalloc_sync_all(void) 192 { 193 unsigned long address; 194 195 if (SHARED_KERNEL_PMD) 196 return; 197 198 for (address = VMALLOC_START & PMD_MASK; 199 address >= TASK_SIZE_MAX && address < FIXADDR_TOP; 200 address += 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 pmd_t *ret; 207 208 /* the pgt_lock only for Xen */ 209 pgt_lock = &pgd_page_get_mm(page)->page_table_lock; 210 211 spin_lock(pgt_lock); 212 ret = vmalloc_sync_one(page_address(page), address); 213 spin_unlock(pgt_lock); 214 215 if (!ret) 216 break; 217 } 218 spin_unlock(&pgd_lock); 219 } 220 } 221 222 /* 223 * 32-bit: 224 * 225 * Handle a fault on the vmalloc or module mapping area 226 */ 227 static noinline int vmalloc_fault(unsigned long address) 228 { 229 unsigned long pgd_paddr; 230 pmd_t *pmd_k; 231 pte_t *pte_k; 232 233 /* Make sure we are in vmalloc area: */ 234 if (!(address >= VMALLOC_START && address < VMALLOC_END)) 235 return -1; 236 237 /* 238 * Synchronize this task's top level page-table 239 * with the 'reference' page table. 240 * 241 * Do _not_ use "current" here. We might be inside 242 * an interrupt in the middle of a task switch.. 243 */ 244 pgd_paddr = read_cr3_pa(); 245 pmd_k = vmalloc_sync_one(__va(pgd_paddr), address); 246 if (!pmd_k) 247 return -1; 248 249 if (pmd_large(*pmd_k)) 250 return 0; 251 252 pte_k = pte_offset_kernel(pmd_k, address); 253 if (!pte_present(*pte_k)) 254 return -1; 255 256 return 0; 257 } 258 NOKPROBE_SYMBOL(vmalloc_fault); 259 260 /* 261 * Did it hit the DOS screen memory VA from vm86 mode? 262 */ 263 static inline void 264 check_v8086_mode(struct pt_regs *regs, unsigned long address, 265 struct task_struct *tsk) 266 { 267 #ifdef CONFIG_VM86 268 unsigned long bit; 269 270 if (!v8086_mode(regs) || !tsk->thread.vm86) 271 return; 272 273 bit = (address - 0xA0000) >> PAGE_SHIFT; 274 if (bit < 32) 275 tsk->thread.vm86->screen_bitmap |= 1 << bit; 276 #endif 277 } 278 279 static bool low_pfn(unsigned long pfn) 280 { 281 return pfn < max_low_pfn; 282 } 283 284 static void dump_pagetable(unsigned long address) 285 { 286 pgd_t *base = __va(read_cr3_pa()); 287 pgd_t *pgd = &base[pgd_index(address)]; 288 p4d_t *p4d; 289 pud_t *pud; 290 pmd_t *pmd; 291 pte_t *pte; 292 293 #ifdef CONFIG_X86_PAE 294 pr_info("*pdpt = %016Lx ", pgd_val(*pgd)); 295 if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd)) 296 goto out; 297 #define pr_pde pr_cont 298 #else 299 #define pr_pde pr_info 300 #endif 301 p4d = p4d_offset(pgd, address); 302 pud = pud_offset(p4d, address); 303 pmd = pmd_offset(pud, address); 304 pr_pde("*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd)); 305 #undef pr_pde 306 307 /* 308 * We must not directly access the pte in the highpte 309 * case if the page table is located in highmem. 310 * And let's rather not kmap-atomic the pte, just in case 311 * it's allocated already: 312 */ 313 if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_large(*pmd)) 314 goto out; 315 316 pte = pte_offset_kernel(pmd, address); 317 pr_cont("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte)); 318 out: 319 pr_cont("\n"); 320 } 321 322 #else /* CONFIG_X86_64: */ 323 324 void vmalloc_sync_all(void) 325 { 326 sync_global_pgds(VMALLOC_START & PGDIR_MASK, VMALLOC_END); 327 } 328 329 /* 330 * 64-bit: 331 * 332 * Handle a fault on the vmalloc area 333 */ 334 static noinline int vmalloc_fault(unsigned long address) 335 { 336 pgd_t *pgd, *pgd_k; 337 p4d_t *p4d, *p4d_k; 338 pud_t *pud; 339 pmd_t *pmd; 340 pte_t *pte; 341 342 /* Make sure we are in vmalloc area: */ 343 if (!(address >= VMALLOC_START && address < VMALLOC_END)) 344 return -1; 345 346 /* 347 * Copy kernel mappings over when needed. This can also 348 * happen within a race in page table update. In the later 349 * case just flush: 350 */ 351 pgd = (pgd_t *)__va(read_cr3_pa()) + pgd_index(address); 352 pgd_k = pgd_offset_k(address); 353 if (pgd_none(*pgd_k)) 354 return -1; 355 356 if (pgtable_l5_enabled()) { 357 if (pgd_none(*pgd)) { 358 set_pgd(pgd, *pgd_k); 359 arch_flush_lazy_mmu_mode(); 360 } else { 361 BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_k)); 362 } 363 } 364 365 /* With 4-level paging, copying happens on the p4d level. */ 366 p4d = p4d_offset(pgd, address); 367 p4d_k = p4d_offset(pgd_k, address); 368 if (p4d_none(*p4d_k)) 369 return -1; 370 371 if (p4d_none(*p4d) && !pgtable_l5_enabled()) { 372 set_p4d(p4d, *p4d_k); 373 arch_flush_lazy_mmu_mode(); 374 } else { 375 BUG_ON(p4d_pfn(*p4d) != p4d_pfn(*p4d_k)); 376 } 377 378 BUILD_BUG_ON(CONFIG_PGTABLE_LEVELS < 4); 379 380 pud = pud_offset(p4d, address); 381 if (pud_none(*pud)) 382 return -1; 383 384 if (pud_large(*pud)) 385 return 0; 386 387 pmd = pmd_offset(pud, address); 388 if (pmd_none(*pmd)) 389 return -1; 390 391 if (pmd_large(*pmd)) 392 return 0; 393 394 pte = pte_offset_kernel(pmd, address); 395 if (!pte_present(*pte)) 396 return -1; 397 398 return 0; 399 } 400 NOKPROBE_SYMBOL(vmalloc_fault); 401 402 #ifdef CONFIG_CPU_SUP_AMD 403 static const char errata93_warning[] = 404 KERN_ERR 405 "******* Your BIOS seems to not contain a fix for K8 errata #93\n" 406 "******* Working around it, but it may cause SEGVs or burn power.\n" 407 "******* Please consider a BIOS update.\n" 408 "******* Disabling USB legacy in the BIOS may also help.\n"; 409 #endif 410 411 /* 412 * No vm86 mode in 64-bit mode: 413 */ 414 static inline void 415 check_v8086_mode(struct pt_regs *regs, unsigned long address, 416 struct task_struct *tsk) 417 { 418 } 419 420 static int bad_address(void *p) 421 { 422 unsigned long dummy; 423 424 return probe_kernel_address((unsigned long *)p, dummy); 425 } 426 427 static void dump_pagetable(unsigned long address) 428 { 429 pgd_t *base = __va(read_cr3_pa()); 430 pgd_t *pgd = base + pgd_index(address); 431 p4d_t *p4d; 432 pud_t *pud; 433 pmd_t *pmd; 434 pte_t *pte; 435 436 if (bad_address(pgd)) 437 goto bad; 438 439 pr_info("PGD %lx ", pgd_val(*pgd)); 440 441 if (!pgd_present(*pgd)) 442 goto out; 443 444 p4d = p4d_offset(pgd, address); 445 if (bad_address(p4d)) 446 goto bad; 447 448 pr_cont("P4D %lx ", p4d_val(*p4d)); 449 if (!p4d_present(*p4d) || p4d_large(*p4d)) 450 goto out; 451 452 pud = pud_offset(p4d, address); 453 if (bad_address(pud)) 454 goto bad; 455 456 pr_cont("PUD %lx ", pud_val(*pud)); 457 if (!pud_present(*pud) || pud_large(*pud)) 458 goto out; 459 460 pmd = pmd_offset(pud, address); 461 if (bad_address(pmd)) 462 goto bad; 463 464 pr_cont("PMD %lx ", pmd_val(*pmd)); 465 if (!pmd_present(*pmd) || pmd_large(*pmd)) 466 goto out; 467 468 pte = pte_offset_kernel(pmd, address); 469 if (bad_address(pte)) 470 goto bad; 471 472 pr_cont("PTE %lx", pte_val(*pte)); 473 out: 474 pr_cont("\n"); 475 return; 476 bad: 477 pr_info("BAD\n"); 478 } 479 480 #endif /* CONFIG_X86_64 */ 481 482 /* 483 * Workaround for K8 erratum #93 & buggy BIOS. 484 * 485 * BIOS SMM functions are required to use a specific workaround 486 * to avoid corruption of the 64bit RIP register on C stepping K8. 487 * 488 * A lot of BIOS that didn't get tested properly miss this. 489 * 490 * The OS sees this as a page fault with the upper 32bits of RIP cleared. 491 * Try to work around it here. 492 * 493 * Note we only handle faults in kernel here. 494 * Does nothing on 32-bit. 495 */ 496 static int is_errata93(struct pt_regs *regs, unsigned long address) 497 { 498 #if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD) 499 if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD 500 || boot_cpu_data.x86 != 0xf) 501 return 0; 502 503 if (address != regs->ip) 504 return 0; 505 506 if ((address >> 32) != 0) 507 return 0; 508 509 address |= 0xffffffffUL << 32; 510 if ((address >= (u64)_stext && address <= (u64)_etext) || 511 (address >= MODULES_VADDR && address <= MODULES_END)) { 512 printk_once(errata93_warning); 513 regs->ip = address; 514 return 1; 515 } 516 #endif 517 return 0; 518 } 519 520 /* 521 * Work around K8 erratum #100 K8 in compat mode occasionally jumps 522 * to illegal addresses >4GB. 523 * 524 * We catch this in the page fault handler because these addresses 525 * are not reachable. Just detect this case and return. Any code 526 * segment in LDT is compatibility mode. 527 */ 528 static int is_errata100(struct pt_regs *regs, unsigned long address) 529 { 530 #ifdef CONFIG_X86_64 531 if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32)) 532 return 1; 533 #endif 534 return 0; 535 } 536 537 static int is_f00f_bug(struct pt_regs *regs, unsigned long address) 538 { 539 #ifdef CONFIG_X86_F00F_BUG 540 unsigned long nr; 541 542 /* 543 * Pentium F0 0F C7 C8 bug workaround: 544 */ 545 if (boot_cpu_has_bug(X86_BUG_F00F)) { 546 nr = (address - idt_descr.address) >> 3; 547 548 if (nr == 6) { 549 do_invalid_op(regs, 0); 550 return 1; 551 } 552 } 553 #endif 554 return 0; 555 } 556 557 static void show_ldttss(const struct desc_ptr *gdt, const char *name, u16 index) 558 { 559 u32 offset = (index >> 3) * sizeof(struct desc_struct); 560 unsigned long addr; 561 struct ldttss_desc desc; 562 563 if (index == 0) { 564 pr_alert("%s: NULL\n", name); 565 return; 566 } 567 568 if (offset + sizeof(struct ldttss_desc) >= gdt->size) { 569 pr_alert("%s: 0x%hx -- out of bounds\n", name, index); 570 return; 571 } 572 573 if (probe_kernel_read(&desc, (void *)(gdt->address + offset), 574 sizeof(struct ldttss_desc))) { 575 pr_alert("%s: 0x%hx -- GDT entry is not readable\n", 576 name, index); 577 return; 578 } 579 580 addr = desc.base0 | (desc.base1 << 16) | ((unsigned long)desc.base2 << 24); 581 #ifdef CONFIG_X86_64 582 addr |= ((u64)desc.base3 << 32); 583 #endif 584 pr_alert("%s: 0x%hx -- base=0x%lx limit=0x%x\n", 585 name, index, addr, (desc.limit0 | (desc.limit1 << 16))); 586 } 587 588 static void 589 show_fault_oops(struct pt_regs *regs, unsigned long error_code, unsigned long address) 590 { 591 if (!oops_may_print()) 592 return; 593 594 if (error_code & X86_PF_INSTR) { 595 unsigned int level; 596 pgd_t *pgd; 597 pte_t *pte; 598 599 pgd = __va(read_cr3_pa()); 600 pgd += pgd_index(address); 601 602 pte = lookup_address_in_pgd(pgd, address, &level); 603 604 if (pte && pte_present(*pte) && !pte_exec(*pte)) 605 pr_crit("kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n", 606 from_kuid(&init_user_ns, current_uid())); 607 if (pte && pte_present(*pte) && pte_exec(*pte) && 608 (pgd_flags(*pgd) & _PAGE_USER) && 609 (__read_cr4() & X86_CR4_SMEP)) 610 pr_crit("unable to execute userspace code (SMEP?) (uid: %d)\n", 611 from_kuid(&init_user_ns, current_uid())); 612 } 613 614 if (address < PAGE_SIZE && !user_mode(regs)) 615 pr_alert("BUG: kernel NULL pointer dereference, address: %px\n", 616 (void *)address); 617 else 618 pr_alert("BUG: unable to handle page fault for address: %px\n", 619 (void *)address); 620 621 pr_alert("#PF: %s %s in %s mode\n", 622 (error_code & X86_PF_USER) ? "user" : "supervisor", 623 (error_code & X86_PF_INSTR) ? "instruction fetch" : 624 (error_code & X86_PF_WRITE) ? "write access" : 625 "read access", 626 user_mode(regs) ? "user" : "kernel"); 627 pr_alert("#PF: error_code(0x%04lx) - %s\n", error_code, 628 !(error_code & X86_PF_PROT) ? "not-present page" : 629 (error_code & X86_PF_RSVD) ? "reserved bit violation" : 630 (error_code & X86_PF_PK) ? "protection keys violation" : 631 "permissions violation"); 632 633 if (!(error_code & X86_PF_USER) && user_mode(regs)) { 634 struct desc_ptr idt, gdt; 635 u16 ldtr, tr; 636 637 /* 638 * This can happen for quite a few reasons. The more obvious 639 * ones are faults accessing the GDT, or LDT. Perhaps 640 * surprisingly, if the CPU tries to deliver a benign or 641 * contributory exception from user code and gets a page fault 642 * during delivery, the page fault can be delivered as though 643 * it originated directly from user code. This could happen 644 * due to wrong permissions on the IDT, GDT, LDT, TSS, or 645 * kernel or IST stack. 646 */ 647 store_idt(&idt); 648 649 /* Usable even on Xen PV -- it's just slow. */ 650 native_store_gdt(&gdt); 651 652 pr_alert("IDT: 0x%lx (limit=0x%hx) GDT: 0x%lx (limit=0x%hx)\n", 653 idt.address, idt.size, gdt.address, gdt.size); 654 655 store_ldt(ldtr); 656 show_ldttss(&gdt, "LDTR", ldtr); 657 658 store_tr(tr); 659 show_ldttss(&gdt, "TR", tr); 660 } 661 662 dump_pagetable(address); 663 } 664 665 static noinline void 666 pgtable_bad(struct pt_regs *regs, unsigned long error_code, 667 unsigned long address) 668 { 669 struct task_struct *tsk; 670 unsigned long flags; 671 int sig; 672 673 flags = oops_begin(); 674 tsk = current; 675 sig = SIGKILL; 676 677 printk(KERN_ALERT "%s: Corrupted page table at address %lx\n", 678 tsk->comm, address); 679 dump_pagetable(address); 680 681 if (__die("Bad pagetable", regs, error_code)) 682 sig = 0; 683 684 oops_end(flags, regs, sig); 685 } 686 687 static void set_signal_archinfo(unsigned long address, 688 unsigned long error_code) 689 { 690 struct task_struct *tsk = current; 691 692 /* 693 * To avoid leaking information about the kernel page 694 * table layout, pretend that user-mode accesses to 695 * kernel addresses are always protection faults. 696 * 697 * NB: This means that failed vsyscalls with vsyscall=none 698 * will have the PROT bit. This doesn't leak any 699 * information and does not appear to cause any problems. 700 */ 701 if (address >= TASK_SIZE_MAX) 702 error_code |= X86_PF_PROT; 703 704 tsk->thread.trap_nr = X86_TRAP_PF; 705 tsk->thread.error_code = error_code | X86_PF_USER; 706 tsk->thread.cr2 = address; 707 } 708 709 static noinline void 710 no_context(struct pt_regs *regs, unsigned long error_code, 711 unsigned long address, int signal, int si_code) 712 { 713 struct task_struct *tsk = current; 714 unsigned long flags; 715 int sig; 716 717 if (user_mode(regs)) { 718 /* 719 * This is an implicit supervisor-mode access from user 720 * mode. Bypass all the kernel-mode recovery code and just 721 * OOPS. 722 */ 723 goto oops; 724 } 725 726 /* Are we prepared to handle this kernel fault? */ 727 if (fixup_exception(regs, X86_TRAP_PF, error_code, address)) { 728 /* 729 * Any interrupt that takes a fault gets the fixup. This makes 730 * the below recursive fault logic only apply to a faults from 731 * task context. 732 */ 733 if (in_interrupt()) 734 return; 735 736 /* 737 * Per the above we're !in_interrupt(), aka. task context. 738 * 739 * In this case we need to make sure we're not recursively 740 * faulting through the emulate_vsyscall() logic. 741 */ 742 if (current->thread.sig_on_uaccess_err && signal) { 743 set_signal_archinfo(address, error_code); 744 745 /* XXX: hwpoison faults will set the wrong code. */ 746 force_sig_fault(signal, si_code, (void __user *)address); 747 } 748 749 /* 750 * Barring that, we can do the fixup and be happy. 751 */ 752 return; 753 } 754 755 #ifdef CONFIG_VMAP_STACK 756 /* 757 * Stack overflow? During boot, we can fault near the initial 758 * stack in the direct map, but that's not an overflow -- check 759 * that we're in vmalloc space to avoid this. 760 */ 761 if (is_vmalloc_addr((void *)address) && 762 (((unsigned long)tsk->stack - 1 - address < PAGE_SIZE) || 763 address - ((unsigned long)tsk->stack + THREAD_SIZE) < PAGE_SIZE)) { 764 unsigned long stack = __this_cpu_ist_top_va(DF) - sizeof(void *); 765 /* 766 * We're likely to be running with very little stack space 767 * left. It's plausible that we'd hit this condition but 768 * double-fault even before we get this far, in which case 769 * we're fine: the double-fault handler will deal with it. 770 * 771 * We don't want to make it all the way into the oops code 772 * and then double-fault, though, because we're likely to 773 * break the console driver and lose most of the stack dump. 774 */ 775 asm volatile ("movq %[stack], %%rsp\n\t" 776 "call handle_stack_overflow\n\t" 777 "1: jmp 1b" 778 : ASM_CALL_CONSTRAINT 779 : "D" ("kernel stack overflow (page fault)"), 780 "S" (regs), "d" (address), 781 [stack] "rm" (stack)); 782 unreachable(); 783 } 784 #endif 785 786 /* 787 * 32-bit: 788 * 789 * Valid to do another page fault here, because if this fault 790 * had been triggered by is_prefetch fixup_exception would have 791 * handled it. 792 * 793 * 64-bit: 794 * 795 * Hall of shame of CPU/BIOS bugs. 796 */ 797 if (is_prefetch(regs, error_code, address)) 798 return; 799 800 if (is_errata93(regs, address)) 801 return; 802 803 /* 804 * Buggy firmware could access regions which might page fault, try to 805 * recover from such faults. 806 */ 807 if (IS_ENABLED(CONFIG_EFI)) 808 efi_recover_from_page_fault(address); 809 810 oops: 811 /* 812 * Oops. The kernel tried to access some bad page. We'll have to 813 * terminate things with extreme prejudice: 814 */ 815 flags = oops_begin(); 816 817 show_fault_oops(regs, error_code, address); 818 819 if (task_stack_end_corrupted(tsk)) 820 printk(KERN_EMERG "Thread overran stack, or stack corrupted\n"); 821 822 sig = SIGKILL; 823 if (__die("Oops", regs, error_code)) 824 sig = 0; 825 826 /* Executive summary in case the body of the oops scrolled away */ 827 printk(KERN_DEFAULT "CR2: %016lx\n", address); 828 829 oops_end(flags, regs, sig); 830 } 831 832 /* 833 * Print out info about fatal segfaults, if the show_unhandled_signals 834 * sysctl is set: 835 */ 836 static inline void 837 show_signal_msg(struct pt_regs *regs, unsigned long error_code, 838 unsigned long address, struct task_struct *tsk) 839 { 840 const char *loglvl = task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG; 841 842 if (!unhandled_signal(tsk, SIGSEGV)) 843 return; 844 845 if (!printk_ratelimit()) 846 return; 847 848 printk("%s%s[%d]: segfault at %lx ip %px sp %px error %lx", 849 loglvl, tsk->comm, task_pid_nr(tsk), address, 850 (void *)regs->ip, (void *)regs->sp, error_code); 851 852 print_vma_addr(KERN_CONT " in ", regs->ip); 853 854 printk(KERN_CONT "\n"); 855 856 show_opcodes(regs, loglvl); 857 } 858 859 /* 860 * The (legacy) vsyscall page is the long page in the kernel portion 861 * of the address space that has user-accessible permissions. 862 */ 863 static bool is_vsyscall_vaddr(unsigned long vaddr) 864 { 865 return unlikely((vaddr & PAGE_MASK) == VSYSCALL_ADDR); 866 } 867 868 static void 869 __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code, 870 unsigned long address, u32 pkey, int si_code) 871 { 872 struct task_struct *tsk = current; 873 874 /* User mode accesses just cause a SIGSEGV */ 875 if (user_mode(regs) && (error_code & X86_PF_USER)) { 876 /* 877 * It's possible to have interrupts off here: 878 */ 879 local_irq_enable(); 880 881 /* 882 * Valid to do another page fault here because this one came 883 * from user space: 884 */ 885 if (is_prefetch(regs, error_code, address)) 886 return; 887 888 if (is_errata100(regs, address)) 889 return; 890 891 /* 892 * To avoid leaking information about the kernel page table 893 * layout, pretend that user-mode accesses to kernel addresses 894 * are always protection faults. 895 */ 896 if (address >= TASK_SIZE_MAX) 897 error_code |= X86_PF_PROT; 898 899 if (likely(show_unhandled_signals)) 900 show_signal_msg(regs, error_code, address, tsk); 901 902 set_signal_archinfo(address, error_code); 903 904 if (si_code == SEGV_PKUERR) 905 force_sig_pkuerr((void __user *)address, pkey); 906 907 force_sig_fault(SIGSEGV, si_code, (void __user *)address); 908 909 return; 910 } 911 912 if (is_f00f_bug(regs, address)) 913 return; 914 915 no_context(regs, error_code, address, SIGSEGV, si_code); 916 } 917 918 static noinline void 919 bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code, 920 unsigned long address) 921 { 922 __bad_area_nosemaphore(regs, error_code, address, 0, SEGV_MAPERR); 923 } 924 925 static void 926 __bad_area(struct pt_regs *regs, unsigned long error_code, 927 unsigned long address, u32 pkey, int si_code) 928 { 929 struct mm_struct *mm = current->mm; 930 /* 931 * Something tried to access memory that isn't in our memory map.. 932 * Fix it, but check if it's kernel or user first.. 933 */ 934 up_read(&mm->mmap_sem); 935 936 __bad_area_nosemaphore(regs, error_code, address, pkey, si_code); 937 } 938 939 static noinline void 940 bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address) 941 { 942 __bad_area(regs, error_code, address, 0, SEGV_MAPERR); 943 } 944 945 static inline bool bad_area_access_from_pkeys(unsigned long error_code, 946 struct vm_area_struct *vma) 947 { 948 /* This code is always called on the current mm */ 949 bool foreign = false; 950 951 if (!boot_cpu_has(X86_FEATURE_OSPKE)) 952 return false; 953 if (error_code & X86_PF_PK) 954 return true; 955 /* this checks permission keys on the VMA: */ 956 if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE), 957 (error_code & X86_PF_INSTR), foreign)) 958 return true; 959 return false; 960 } 961 962 static noinline void 963 bad_area_access_error(struct pt_regs *regs, unsigned long error_code, 964 unsigned long address, struct vm_area_struct *vma) 965 { 966 /* 967 * This OSPKE check is not strictly necessary at runtime. 968 * But, doing it this way allows compiler optimizations 969 * if pkeys are compiled out. 970 */ 971 if (bad_area_access_from_pkeys(error_code, vma)) { 972 /* 973 * A protection key fault means that the PKRU value did not allow 974 * access to some PTE. Userspace can figure out what PKRU was 975 * from the XSAVE state. This function captures the pkey from 976 * the vma and passes it to userspace so userspace can discover 977 * which protection key was set on the PTE. 978 * 979 * If we get here, we know that the hardware signaled a X86_PF_PK 980 * fault and that there was a VMA once we got in the fault 981 * handler. It does *not* guarantee that the VMA we find here 982 * was the one that we faulted on. 983 * 984 * 1. T1 : mprotect_key(foo, PAGE_SIZE, pkey=4); 985 * 2. T1 : set PKRU to deny access to pkey=4, touches page 986 * 3. T1 : faults... 987 * 4. T2: mprotect_key(foo, PAGE_SIZE, pkey=5); 988 * 5. T1 : enters fault handler, takes mmap_sem, etc... 989 * 6. T1 : reaches here, sees vma_pkey(vma)=5, when we really 990 * faulted on a pte with its pkey=4. 991 */ 992 u32 pkey = vma_pkey(vma); 993 994 __bad_area(regs, error_code, address, pkey, SEGV_PKUERR); 995 } else { 996 __bad_area(regs, error_code, address, 0, SEGV_ACCERR); 997 } 998 } 999 1000 static void 1001 do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address, 1002 vm_fault_t fault) 1003 { 1004 /* Kernel mode? Handle exceptions or die: */ 1005 if (!(error_code & X86_PF_USER)) { 1006 no_context(regs, error_code, address, SIGBUS, BUS_ADRERR); 1007 return; 1008 } 1009 1010 /* User-space => ok to do another page fault: */ 1011 if (is_prefetch(regs, error_code, address)) 1012 return; 1013 1014 set_signal_archinfo(address, error_code); 1015 1016 #ifdef CONFIG_MEMORY_FAILURE 1017 if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) { 1018 struct task_struct *tsk = current; 1019 unsigned lsb = 0; 1020 1021 pr_err( 1022 "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n", 1023 tsk->comm, tsk->pid, address); 1024 if (fault & VM_FAULT_HWPOISON_LARGE) 1025 lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault)); 1026 if (fault & VM_FAULT_HWPOISON) 1027 lsb = PAGE_SHIFT; 1028 force_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb); 1029 return; 1030 } 1031 #endif 1032 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address); 1033 } 1034 1035 static noinline void 1036 mm_fault_error(struct pt_regs *regs, unsigned long error_code, 1037 unsigned long address, vm_fault_t fault) 1038 { 1039 if (fatal_signal_pending(current) && !(error_code & X86_PF_USER)) { 1040 no_context(regs, error_code, address, 0, 0); 1041 return; 1042 } 1043 1044 if (fault & VM_FAULT_OOM) { 1045 /* Kernel mode? Handle exceptions or die: */ 1046 if (!(error_code & X86_PF_USER)) { 1047 no_context(regs, error_code, address, 1048 SIGSEGV, SEGV_MAPERR); 1049 return; 1050 } 1051 1052 /* 1053 * We ran out of memory, call the OOM killer, and return the 1054 * userspace (which will retry the fault, or kill us if we got 1055 * oom-killed): 1056 */ 1057 pagefault_out_of_memory(); 1058 } else { 1059 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON| 1060 VM_FAULT_HWPOISON_LARGE)) 1061 do_sigbus(regs, error_code, address, fault); 1062 else if (fault & VM_FAULT_SIGSEGV) 1063 bad_area_nosemaphore(regs, error_code, address); 1064 else 1065 BUG(); 1066 } 1067 } 1068 1069 static int spurious_kernel_fault_check(unsigned long error_code, pte_t *pte) 1070 { 1071 if ((error_code & X86_PF_WRITE) && !pte_write(*pte)) 1072 return 0; 1073 1074 if ((error_code & X86_PF_INSTR) && !pte_exec(*pte)) 1075 return 0; 1076 1077 return 1; 1078 } 1079 1080 /* 1081 * Handle a spurious fault caused by a stale TLB entry. 1082 * 1083 * This allows us to lazily refresh the TLB when increasing the 1084 * permissions of a kernel page (RO -> RW or NX -> X). Doing it 1085 * eagerly is very expensive since that implies doing a full 1086 * cross-processor TLB flush, even if no stale TLB entries exist 1087 * on other processors. 1088 * 1089 * Spurious faults may only occur if the TLB contains an entry with 1090 * fewer permission than the page table entry. Non-present (P = 0) 1091 * and reserved bit (R = 1) faults are never spurious. 1092 * 1093 * There are no security implications to leaving a stale TLB when 1094 * increasing the permissions on a page. 1095 * 1096 * Returns non-zero if a spurious fault was handled, zero otherwise. 1097 * 1098 * See Intel Developer's Manual Vol 3 Section 4.10.4.3, bullet 3 1099 * (Optional Invalidation). 1100 */ 1101 static noinline int 1102 spurious_kernel_fault(unsigned long error_code, unsigned long address) 1103 { 1104 pgd_t *pgd; 1105 p4d_t *p4d; 1106 pud_t *pud; 1107 pmd_t *pmd; 1108 pte_t *pte; 1109 int ret; 1110 1111 /* 1112 * Only writes to RO or instruction fetches from NX may cause 1113 * spurious faults. 1114 * 1115 * These could be from user or supervisor accesses but the TLB 1116 * is only lazily flushed after a kernel mapping protection 1117 * change, so user accesses are not expected to cause spurious 1118 * faults. 1119 */ 1120 if (error_code != (X86_PF_WRITE | X86_PF_PROT) && 1121 error_code != (X86_PF_INSTR | X86_PF_PROT)) 1122 return 0; 1123 1124 pgd = init_mm.pgd + pgd_index(address); 1125 if (!pgd_present(*pgd)) 1126 return 0; 1127 1128 p4d = p4d_offset(pgd, address); 1129 if (!p4d_present(*p4d)) 1130 return 0; 1131 1132 if (p4d_large(*p4d)) 1133 return spurious_kernel_fault_check(error_code, (pte_t *) p4d); 1134 1135 pud = pud_offset(p4d, address); 1136 if (!pud_present(*pud)) 1137 return 0; 1138 1139 if (pud_large(*pud)) 1140 return spurious_kernel_fault_check(error_code, (pte_t *) pud); 1141 1142 pmd = pmd_offset(pud, address); 1143 if (!pmd_present(*pmd)) 1144 return 0; 1145 1146 if (pmd_large(*pmd)) 1147 return spurious_kernel_fault_check(error_code, (pte_t *) pmd); 1148 1149 pte = pte_offset_kernel(pmd, address); 1150 if (!pte_present(*pte)) 1151 return 0; 1152 1153 ret = spurious_kernel_fault_check(error_code, pte); 1154 if (!ret) 1155 return 0; 1156 1157 /* 1158 * Make sure we have permissions in PMD. 1159 * If not, then there's a bug in the page tables: 1160 */ 1161 ret = spurious_kernel_fault_check(error_code, (pte_t *) pmd); 1162 WARN_ONCE(!ret, "PMD has incorrect permission bits\n"); 1163 1164 return ret; 1165 } 1166 NOKPROBE_SYMBOL(spurious_kernel_fault); 1167 1168 int show_unhandled_signals = 1; 1169 1170 static inline int 1171 access_error(unsigned long error_code, struct vm_area_struct *vma) 1172 { 1173 /* This is only called for the current mm, so: */ 1174 bool foreign = false; 1175 1176 /* 1177 * Read or write was blocked by protection keys. This is 1178 * always an unconditional error and can never result in 1179 * a follow-up action to resolve the fault, like a COW. 1180 */ 1181 if (error_code & X86_PF_PK) 1182 return 1; 1183 1184 /* 1185 * Make sure to check the VMA so that we do not perform 1186 * faults just to hit a X86_PF_PK as soon as we fill in a 1187 * page. 1188 */ 1189 if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE), 1190 (error_code & X86_PF_INSTR), foreign)) 1191 return 1; 1192 1193 if (error_code & X86_PF_WRITE) { 1194 /* write, present and write, not present: */ 1195 if (unlikely(!(vma->vm_flags & VM_WRITE))) 1196 return 1; 1197 return 0; 1198 } 1199 1200 /* read, present: */ 1201 if (unlikely(error_code & X86_PF_PROT)) 1202 return 1; 1203 1204 /* read, not present: */ 1205 if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))) 1206 return 1; 1207 1208 return 0; 1209 } 1210 1211 static int fault_in_kernel_space(unsigned long address) 1212 { 1213 /* 1214 * On 64-bit systems, the vsyscall page is at an address above 1215 * TASK_SIZE_MAX, but is not considered part of the kernel 1216 * address space. 1217 */ 1218 if (IS_ENABLED(CONFIG_X86_64) && is_vsyscall_vaddr(address)) 1219 return false; 1220 1221 return address >= TASK_SIZE_MAX; 1222 } 1223 1224 /* 1225 * Called for all faults where 'address' is part of the kernel address 1226 * space. Might get called for faults that originate from *code* that 1227 * ran in userspace or the kernel. 1228 */ 1229 static void 1230 do_kern_addr_fault(struct pt_regs *regs, unsigned long hw_error_code, 1231 unsigned long address) 1232 { 1233 /* 1234 * Protection keys exceptions only happen on user pages. We 1235 * have no user pages in the kernel portion of the address 1236 * space, so do not expect them here. 1237 */ 1238 WARN_ON_ONCE(hw_error_code & X86_PF_PK); 1239 1240 /* 1241 * We can fault-in kernel-space virtual memory on-demand. The 1242 * 'reference' page table is init_mm.pgd. 1243 * 1244 * NOTE! We MUST NOT take any locks for this case. We may 1245 * be in an interrupt or a critical region, and should 1246 * only copy the information from the master page table, 1247 * nothing more. 1248 * 1249 * Before doing this on-demand faulting, ensure that the 1250 * fault is not any of the following: 1251 * 1. A fault on a PTE with a reserved bit set. 1252 * 2. A fault caused by a user-mode access. (Do not demand- 1253 * fault kernel memory due to user-mode accesses). 1254 * 3. A fault caused by a page-level protection violation. 1255 * (A demand fault would be on a non-present page which 1256 * would have X86_PF_PROT==0). 1257 */ 1258 if (!(hw_error_code & (X86_PF_RSVD | X86_PF_USER | X86_PF_PROT))) { 1259 if (vmalloc_fault(address) >= 0) 1260 return; 1261 } 1262 1263 /* Was the fault spurious, caused by lazy TLB invalidation? */ 1264 if (spurious_kernel_fault(hw_error_code, address)) 1265 return; 1266 1267 /* kprobes don't want to hook the spurious faults: */ 1268 if (kprobe_page_fault(regs, X86_TRAP_PF)) 1269 return; 1270 1271 /* 1272 * Note, despite being a "bad area", there are quite a few 1273 * acceptable reasons to get here, such as erratum fixups 1274 * and handling kernel code that can fault, like get_user(). 1275 * 1276 * Don't take the mm semaphore here. If we fixup a prefetch 1277 * fault we could otherwise deadlock: 1278 */ 1279 bad_area_nosemaphore(regs, hw_error_code, address); 1280 } 1281 NOKPROBE_SYMBOL(do_kern_addr_fault); 1282 1283 /* Handle faults in the user portion of the address space */ 1284 static inline 1285 void do_user_addr_fault(struct pt_regs *regs, 1286 unsigned long hw_error_code, 1287 unsigned long address) 1288 { 1289 struct vm_area_struct *vma; 1290 struct task_struct *tsk; 1291 struct mm_struct *mm; 1292 vm_fault_t fault, major = 0; 1293 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; 1294 1295 tsk = current; 1296 mm = tsk->mm; 1297 1298 /* kprobes don't want to hook the spurious faults: */ 1299 if (unlikely(kprobe_page_fault(regs, X86_TRAP_PF))) 1300 return; 1301 1302 /* 1303 * Reserved bits are never expected to be set on 1304 * entries in the user portion of the page tables. 1305 */ 1306 if (unlikely(hw_error_code & X86_PF_RSVD)) 1307 pgtable_bad(regs, hw_error_code, address); 1308 1309 /* 1310 * If SMAP is on, check for invalid kernel (supervisor) access to user 1311 * pages in the user address space. The odd case here is WRUSS, 1312 * which, according to the preliminary documentation, does not respect 1313 * SMAP and will have the USER bit set so, in all cases, SMAP 1314 * enforcement appears to be consistent with the USER bit. 1315 */ 1316 if (unlikely(cpu_feature_enabled(X86_FEATURE_SMAP) && 1317 !(hw_error_code & X86_PF_USER) && 1318 !(regs->flags & X86_EFLAGS_AC))) 1319 { 1320 bad_area_nosemaphore(regs, hw_error_code, address); 1321 return; 1322 } 1323 1324 /* 1325 * If we're in an interrupt, have no user context or are running 1326 * in a region with pagefaults disabled then we must not take the fault 1327 */ 1328 if (unlikely(faulthandler_disabled() || !mm)) { 1329 bad_area_nosemaphore(regs, hw_error_code, address); 1330 return; 1331 } 1332 1333 /* 1334 * It's safe to allow irq's after cr2 has been saved and the 1335 * vmalloc fault has been handled. 1336 * 1337 * User-mode registers count as a user access even for any 1338 * potential system fault or CPU buglet: 1339 */ 1340 if (user_mode(regs)) { 1341 local_irq_enable(); 1342 flags |= FAULT_FLAG_USER; 1343 } else { 1344 if (regs->flags & X86_EFLAGS_IF) 1345 local_irq_enable(); 1346 } 1347 1348 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 1349 1350 if (hw_error_code & X86_PF_WRITE) 1351 flags |= FAULT_FLAG_WRITE; 1352 if (hw_error_code & X86_PF_INSTR) 1353 flags |= FAULT_FLAG_INSTRUCTION; 1354 1355 #ifdef CONFIG_X86_64 1356 /* 1357 * Faults in the vsyscall page might need emulation. The 1358 * vsyscall page is at a high address (>PAGE_OFFSET), but is 1359 * considered to be part of the user address space. 1360 * 1361 * The vsyscall page does not have a "real" VMA, so do this 1362 * emulation before we go searching for VMAs. 1363 * 1364 * PKRU never rejects instruction fetches, so we don't need 1365 * to consider the PF_PK bit. 1366 */ 1367 if (is_vsyscall_vaddr(address)) { 1368 if (emulate_vsyscall(hw_error_code, regs, address)) 1369 return; 1370 } 1371 #endif 1372 1373 /* 1374 * Kernel-mode access to the user address space should only occur 1375 * on well-defined single instructions listed in the exception 1376 * tables. But, an erroneous kernel fault occurring outside one of 1377 * those areas which also holds mmap_sem might deadlock attempting 1378 * to validate the fault against the address space. 1379 * 1380 * Only do the expensive exception table search when we might be at 1381 * risk of a deadlock. This happens if we 1382 * 1. Failed to acquire mmap_sem, and 1383 * 2. The access did not originate in userspace. 1384 */ 1385 if (unlikely(!down_read_trylock(&mm->mmap_sem))) { 1386 if (!user_mode(regs) && !search_exception_tables(regs->ip)) { 1387 /* 1388 * Fault from code in kernel from 1389 * which we do not expect faults. 1390 */ 1391 bad_area_nosemaphore(regs, hw_error_code, address); 1392 return; 1393 } 1394 retry: 1395 down_read(&mm->mmap_sem); 1396 } else { 1397 /* 1398 * The above down_read_trylock() might have succeeded in 1399 * which case we'll have missed the might_sleep() from 1400 * down_read(): 1401 */ 1402 might_sleep(); 1403 } 1404 1405 vma = find_vma(mm, address); 1406 if (unlikely(!vma)) { 1407 bad_area(regs, hw_error_code, address); 1408 return; 1409 } 1410 if (likely(vma->vm_start <= address)) 1411 goto good_area; 1412 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) { 1413 bad_area(regs, hw_error_code, address); 1414 return; 1415 } 1416 if (unlikely(expand_stack(vma, address))) { 1417 bad_area(regs, hw_error_code, address); 1418 return; 1419 } 1420 1421 /* 1422 * Ok, we have a good vm_area for this memory access, so 1423 * we can handle it.. 1424 */ 1425 good_area: 1426 if (unlikely(access_error(hw_error_code, vma))) { 1427 bad_area_access_error(regs, hw_error_code, address, vma); 1428 return; 1429 } 1430 1431 /* 1432 * If for any reason at all we couldn't handle the fault, 1433 * make sure we exit gracefully rather than endlessly redo 1434 * the fault. Since we never set FAULT_FLAG_RETRY_NOWAIT, if 1435 * we get VM_FAULT_RETRY back, the mmap_sem has been unlocked. 1436 * 1437 * Note that handle_userfault() may also release and reacquire mmap_sem 1438 * (and not return with VM_FAULT_RETRY), when returning to userland to 1439 * repeat the page fault later with a VM_FAULT_NOPAGE retval 1440 * (potentially after handling any pending signal during the return to 1441 * userland). The return to userland is identified whenever 1442 * FAULT_FLAG_USER|FAULT_FLAG_KILLABLE are both set in flags. 1443 */ 1444 fault = handle_mm_fault(vma, address, flags); 1445 major |= fault & VM_FAULT_MAJOR; 1446 1447 /* 1448 * If we need to retry the mmap_sem has already been released, 1449 * and if there is a fatal signal pending there is no guarantee 1450 * that we made any progress. Handle this case first. 1451 */ 1452 if (unlikely(fault & VM_FAULT_RETRY)) { 1453 /* Retry at most once */ 1454 if (flags & FAULT_FLAG_ALLOW_RETRY) { 1455 flags &= ~FAULT_FLAG_ALLOW_RETRY; 1456 flags |= FAULT_FLAG_TRIED; 1457 if (!fatal_signal_pending(tsk)) 1458 goto retry; 1459 } 1460 1461 /* User mode? Just return to handle the fatal exception */ 1462 if (flags & FAULT_FLAG_USER) 1463 return; 1464 1465 /* Not returning to user mode? Handle exceptions or die: */ 1466 no_context(regs, hw_error_code, address, SIGBUS, BUS_ADRERR); 1467 return; 1468 } 1469 1470 up_read(&mm->mmap_sem); 1471 if (unlikely(fault & VM_FAULT_ERROR)) { 1472 mm_fault_error(regs, hw_error_code, address, fault); 1473 return; 1474 } 1475 1476 /* 1477 * Major/minor page fault accounting. If any of the events 1478 * returned VM_FAULT_MAJOR, we account it as a major fault. 1479 */ 1480 if (major) { 1481 tsk->maj_flt++; 1482 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address); 1483 } else { 1484 tsk->min_flt++; 1485 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address); 1486 } 1487 1488 check_v8086_mode(regs, address, tsk); 1489 } 1490 NOKPROBE_SYMBOL(do_user_addr_fault); 1491 1492 /* 1493 * Explicitly marked noinline such that the function tracer sees this as the 1494 * page_fault entry point. 1495 */ 1496 static noinline void 1497 __do_page_fault(struct pt_regs *regs, unsigned long hw_error_code, 1498 unsigned long address) 1499 { 1500 prefetchw(¤t->mm->mmap_sem); 1501 1502 if (unlikely(kmmio_fault(regs, address))) 1503 return; 1504 1505 /* Was the fault on kernel-controlled part of the address space? */ 1506 if (unlikely(fault_in_kernel_space(address))) 1507 do_kern_addr_fault(regs, hw_error_code, address); 1508 else 1509 do_user_addr_fault(regs, hw_error_code, address); 1510 } 1511 NOKPROBE_SYMBOL(__do_page_fault); 1512 1513 static __always_inline void 1514 trace_page_fault_entries(struct pt_regs *regs, unsigned long error_code, 1515 unsigned long address) 1516 { 1517 if (!trace_pagefault_enabled()) 1518 return; 1519 1520 if (user_mode(regs)) 1521 trace_page_fault_user(address, regs, error_code); 1522 else 1523 trace_page_fault_kernel(address, regs, error_code); 1524 } 1525 1526 dotraplinkage void 1527 do_page_fault(struct pt_regs *regs, unsigned long error_code, unsigned long address) 1528 { 1529 enum ctx_state prev_state; 1530 1531 prev_state = exception_enter(); 1532 trace_page_fault_entries(regs, error_code, address); 1533 __do_page_fault(regs, error_code, address); 1534 exception_exit(prev_state); 1535 } 1536 NOKPROBE_SYMBOL(do_page_fault); 1537