1 /* 2 * Copyright (C) 1995 Linus Torvalds 3 * Copyright (C) 2001, 2002 Andi Kleen, SuSE Labs. 4 * Copyright (C) 2008-2009, Red Hat Inc., Ingo Molnar 5 */ 6 #include <linux/sched.h> /* test_thread_flag(), ... */ 7 #include <linux/sched/task_stack.h> /* task_stack_*(), ... */ 8 #include <linux/kdebug.h> /* oops_begin/end, ... */ 9 #include <linux/extable.h> /* search_exception_tables */ 10 #include <linux/bootmem.h> /* max_low_pfn */ 11 #include <linux/kprobes.h> /* NOKPROBE_SYMBOL, ... */ 12 #include <linux/mmiotrace.h> /* kmmio_handler, ... */ 13 #include <linux/perf_event.h> /* perf_sw_event */ 14 #include <linux/hugetlb.h> /* hstate_index_to_shift */ 15 #include <linux/prefetch.h> /* prefetchw */ 16 #include <linux/context_tracking.h> /* exception_enter(), ... */ 17 #include <linux/uaccess.h> /* faulthandler_disabled() */ 18 19 #include <asm/cpufeature.h> /* boot_cpu_has, ... */ 20 #include <asm/traps.h> /* dotraplinkage, ... */ 21 #include <asm/pgalloc.h> /* pgd_*(), ... */ 22 #include <asm/kmemcheck.h> /* kmemcheck_*(), ... */ 23 #include <asm/fixmap.h> /* VSYSCALL_ADDR */ 24 #include <asm/vsyscall.h> /* emulate_vsyscall */ 25 #include <asm/vm86.h> /* struct vm86 */ 26 #include <asm/mmu_context.h> /* vma_pkey() */ 27 28 #define CREATE_TRACE_POINTS 29 #include <asm/trace/exceptions.h> 30 31 /* 32 * Page fault error code bits: 33 * 34 * bit 0 == 0: no page found 1: protection fault 35 * bit 1 == 0: read access 1: write access 36 * bit 2 == 0: kernel-mode access 1: user-mode access 37 * bit 3 == 1: use of reserved bit detected 38 * bit 4 == 1: fault was an instruction fetch 39 * bit 5 == 1: protection keys block access 40 */ 41 enum x86_pf_error_code { 42 43 PF_PROT = 1 << 0, 44 PF_WRITE = 1 << 1, 45 PF_USER = 1 << 2, 46 PF_RSVD = 1 << 3, 47 PF_INSTR = 1 << 4, 48 PF_PK = 1 << 5, 49 }; 50 51 /* 52 * Returns 0 if mmiotrace is disabled, or if the fault is not 53 * handled by mmiotrace: 54 */ 55 static nokprobe_inline int 56 kmmio_fault(struct pt_regs *regs, unsigned long addr) 57 { 58 if (unlikely(is_kmmio_active())) 59 if (kmmio_handler(regs, addr) == 1) 60 return -1; 61 return 0; 62 } 63 64 static nokprobe_inline int kprobes_fault(struct pt_regs *regs) 65 { 66 int ret = 0; 67 68 /* kprobe_running() needs smp_processor_id() */ 69 if (kprobes_built_in() && !user_mode(regs)) { 70 preempt_disable(); 71 if (kprobe_running() && kprobe_fault_handler(regs, 14)) 72 ret = 1; 73 preempt_enable(); 74 } 75 76 return ret; 77 } 78 79 /* 80 * Prefetch quirks: 81 * 82 * 32-bit mode: 83 * 84 * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch. 85 * Check that here and ignore it. 86 * 87 * 64-bit mode: 88 * 89 * Sometimes the CPU reports invalid exceptions on prefetch. 90 * Check that here and ignore it. 91 * 92 * Opcode checker based on code by Richard Brunner. 93 */ 94 static inline int 95 check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr, 96 unsigned char opcode, int *prefetch) 97 { 98 unsigned char instr_hi = opcode & 0xf0; 99 unsigned char instr_lo = opcode & 0x0f; 100 101 switch (instr_hi) { 102 case 0x20: 103 case 0x30: 104 /* 105 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes. 106 * In X86_64 long mode, the CPU will signal invalid 107 * opcode if some of these prefixes are present so 108 * X86_64 will never get here anyway 109 */ 110 return ((instr_lo & 7) == 0x6); 111 #ifdef CONFIG_X86_64 112 case 0x40: 113 /* 114 * In AMD64 long mode 0x40..0x4F are valid REX prefixes 115 * Need to figure out under what instruction mode the 116 * instruction was issued. Could check the LDT for lm, 117 * but for now it's good enough to assume that long 118 * mode only uses well known segments or kernel. 119 */ 120 return (!user_mode(regs) || user_64bit_mode(regs)); 121 #endif 122 case 0x60: 123 /* 0x64 thru 0x67 are valid prefixes in all modes. */ 124 return (instr_lo & 0xC) == 0x4; 125 case 0xF0: 126 /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */ 127 return !instr_lo || (instr_lo>>1) == 1; 128 case 0x00: 129 /* Prefetch instruction is 0x0F0D or 0x0F18 */ 130 if (probe_kernel_address(instr, opcode)) 131 return 0; 132 133 *prefetch = (instr_lo == 0xF) && 134 (opcode == 0x0D || opcode == 0x18); 135 return 0; 136 default: 137 return 0; 138 } 139 } 140 141 static int 142 is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr) 143 { 144 unsigned char *max_instr; 145 unsigned char *instr; 146 int prefetch = 0; 147 148 /* 149 * If it was a exec (instruction fetch) fault on NX page, then 150 * do not ignore the fault: 151 */ 152 if (error_code & PF_INSTR) 153 return 0; 154 155 instr = (void *)convert_ip_to_linear(current, regs); 156 max_instr = instr + 15; 157 158 if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE_MAX) 159 return 0; 160 161 while (instr < max_instr) { 162 unsigned char opcode; 163 164 if (probe_kernel_address(instr, opcode)) 165 break; 166 167 instr++; 168 169 if (!check_prefetch_opcode(regs, instr, opcode, &prefetch)) 170 break; 171 } 172 return prefetch; 173 } 174 175 /* 176 * A protection key fault means that the PKRU value did not allow 177 * access to some PTE. Userspace can figure out what PKRU was 178 * from the XSAVE state, and this function fills out a field in 179 * siginfo so userspace can discover which protection key was set 180 * on the PTE. 181 * 182 * If we get here, we know that the hardware signaled a PF_PK 183 * fault and that there was a VMA once we got in the fault 184 * handler. It does *not* guarantee that the VMA we find here 185 * was the one that we faulted on. 186 * 187 * 1. T1 : mprotect_key(foo, PAGE_SIZE, pkey=4); 188 * 2. T1 : set PKRU to deny access to pkey=4, touches page 189 * 3. T1 : faults... 190 * 4. T2: mprotect_key(foo, PAGE_SIZE, pkey=5); 191 * 5. T1 : enters fault handler, takes mmap_sem, etc... 192 * 6. T1 : reaches here, sees vma_pkey(vma)=5, when we really 193 * faulted on a pte with its pkey=4. 194 */ 195 static void fill_sig_info_pkey(int si_code, siginfo_t *info, u32 *pkey) 196 { 197 /* This is effectively an #ifdef */ 198 if (!boot_cpu_has(X86_FEATURE_OSPKE)) 199 return; 200 201 /* Fault not from Protection Keys: nothing to do */ 202 if (si_code != SEGV_PKUERR) 203 return; 204 /* 205 * force_sig_info_fault() is called from a number of 206 * contexts, some of which have a VMA and some of which 207 * do not. The PF_PK handing happens after we have a 208 * valid VMA, so we should never reach this without a 209 * valid VMA. 210 */ 211 if (!pkey) { 212 WARN_ONCE(1, "PKU fault with no VMA passed in"); 213 info->si_pkey = 0; 214 return; 215 } 216 /* 217 * si_pkey should be thought of as a strong hint, but not 218 * absolutely guranteed to be 100% accurate because of 219 * the race explained above. 220 */ 221 info->si_pkey = *pkey; 222 } 223 224 static void 225 force_sig_info_fault(int si_signo, int si_code, unsigned long address, 226 struct task_struct *tsk, u32 *pkey, int fault) 227 { 228 unsigned lsb = 0; 229 siginfo_t info; 230 231 info.si_signo = si_signo; 232 info.si_errno = 0; 233 info.si_code = si_code; 234 info.si_addr = (void __user *)address; 235 if (fault & VM_FAULT_HWPOISON_LARGE) 236 lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault)); 237 if (fault & VM_FAULT_HWPOISON) 238 lsb = PAGE_SHIFT; 239 info.si_addr_lsb = lsb; 240 241 fill_sig_info_pkey(si_code, &info, pkey); 242 243 force_sig_info(si_signo, &info, tsk); 244 } 245 246 DEFINE_SPINLOCK(pgd_lock); 247 LIST_HEAD(pgd_list); 248 249 #ifdef CONFIG_X86_32 250 static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address) 251 { 252 unsigned index = pgd_index(address); 253 pgd_t *pgd_k; 254 p4d_t *p4d, *p4d_k; 255 pud_t *pud, *pud_k; 256 pmd_t *pmd, *pmd_k; 257 258 pgd += index; 259 pgd_k = init_mm.pgd + index; 260 261 if (!pgd_present(*pgd_k)) 262 return NULL; 263 264 /* 265 * set_pgd(pgd, *pgd_k); here would be useless on PAE 266 * and redundant with the set_pmd() on non-PAE. As would 267 * set_p4d/set_pud. 268 */ 269 p4d = p4d_offset(pgd, address); 270 p4d_k = p4d_offset(pgd_k, address); 271 if (!p4d_present(*p4d_k)) 272 return NULL; 273 274 pud = pud_offset(p4d, address); 275 pud_k = pud_offset(p4d_k, address); 276 if (!pud_present(*pud_k)) 277 return NULL; 278 279 pmd = pmd_offset(pud, address); 280 pmd_k = pmd_offset(pud_k, address); 281 if (!pmd_present(*pmd_k)) 282 return NULL; 283 284 if (!pmd_present(*pmd)) 285 set_pmd(pmd, *pmd_k); 286 else 287 BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k)); 288 289 return pmd_k; 290 } 291 292 void vmalloc_sync_all(void) 293 { 294 unsigned long address; 295 296 if (SHARED_KERNEL_PMD) 297 return; 298 299 for (address = VMALLOC_START & PMD_MASK; 300 address >= TASK_SIZE_MAX && address < FIXADDR_TOP; 301 address += PMD_SIZE) { 302 struct page *page; 303 304 spin_lock(&pgd_lock); 305 list_for_each_entry(page, &pgd_list, lru) { 306 spinlock_t *pgt_lock; 307 pmd_t *ret; 308 309 /* the pgt_lock only for Xen */ 310 pgt_lock = &pgd_page_get_mm(page)->page_table_lock; 311 312 spin_lock(pgt_lock); 313 ret = vmalloc_sync_one(page_address(page), address); 314 spin_unlock(pgt_lock); 315 316 if (!ret) 317 break; 318 } 319 spin_unlock(&pgd_lock); 320 } 321 } 322 323 /* 324 * 32-bit: 325 * 326 * Handle a fault on the vmalloc or module mapping area 327 */ 328 static noinline int vmalloc_fault(unsigned long address) 329 { 330 unsigned long pgd_paddr; 331 pmd_t *pmd_k; 332 pte_t *pte_k; 333 334 /* Make sure we are in vmalloc area: */ 335 if (!(address >= VMALLOC_START && address < VMALLOC_END)) 336 return -1; 337 338 WARN_ON_ONCE(in_nmi()); 339 340 /* 341 * Synchronize this task's top level page-table 342 * with the 'reference' page table. 343 * 344 * Do _not_ use "current" here. We might be inside 345 * an interrupt in the middle of a task switch.. 346 */ 347 pgd_paddr = read_cr3_pa(); 348 pmd_k = vmalloc_sync_one(__va(pgd_paddr), address); 349 if (!pmd_k) 350 return -1; 351 352 if (pmd_huge(*pmd_k)) 353 return 0; 354 355 pte_k = pte_offset_kernel(pmd_k, address); 356 if (!pte_present(*pte_k)) 357 return -1; 358 359 return 0; 360 } 361 NOKPROBE_SYMBOL(vmalloc_fault); 362 363 /* 364 * Did it hit the DOS screen memory VA from vm86 mode? 365 */ 366 static inline void 367 check_v8086_mode(struct pt_regs *regs, unsigned long address, 368 struct task_struct *tsk) 369 { 370 #ifdef CONFIG_VM86 371 unsigned long bit; 372 373 if (!v8086_mode(regs) || !tsk->thread.vm86) 374 return; 375 376 bit = (address - 0xA0000) >> PAGE_SHIFT; 377 if (bit < 32) 378 tsk->thread.vm86->screen_bitmap |= 1 << bit; 379 #endif 380 } 381 382 static bool low_pfn(unsigned long pfn) 383 { 384 return pfn < max_low_pfn; 385 } 386 387 static void dump_pagetable(unsigned long address) 388 { 389 pgd_t *base = __va(read_cr3_pa()); 390 pgd_t *pgd = &base[pgd_index(address)]; 391 p4d_t *p4d; 392 pud_t *pud; 393 pmd_t *pmd; 394 pte_t *pte; 395 396 #ifdef CONFIG_X86_PAE 397 pr_info("*pdpt = %016Lx ", pgd_val(*pgd)); 398 if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd)) 399 goto out; 400 #define pr_pde pr_cont 401 #else 402 #define pr_pde pr_info 403 #endif 404 p4d = p4d_offset(pgd, address); 405 pud = pud_offset(p4d, address); 406 pmd = pmd_offset(pud, address); 407 pr_pde("*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd)); 408 #undef pr_pde 409 410 /* 411 * We must not directly access the pte in the highpte 412 * case if the page table is located in highmem. 413 * And let's rather not kmap-atomic the pte, just in case 414 * it's allocated already: 415 */ 416 if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_large(*pmd)) 417 goto out; 418 419 pte = pte_offset_kernel(pmd, address); 420 pr_cont("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte)); 421 out: 422 pr_cont("\n"); 423 } 424 425 #else /* CONFIG_X86_64: */ 426 427 void vmalloc_sync_all(void) 428 { 429 sync_global_pgds(VMALLOC_START & PGDIR_MASK, VMALLOC_END); 430 } 431 432 /* 433 * 64-bit: 434 * 435 * Handle a fault on the vmalloc area 436 */ 437 static noinline int vmalloc_fault(unsigned long address) 438 { 439 pgd_t *pgd, *pgd_ref; 440 p4d_t *p4d, *p4d_ref; 441 pud_t *pud, *pud_ref; 442 pmd_t *pmd, *pmd_ref; 443 pte_t *pte, *pte_ref; 444 445 /* Make sure we are in vmalloc area: */ 446 if (!(address >= VMALLOC_START && address < VMALLOC_END)) 447 return -1; 448 449 WARN_ON_ONCE(in_nmi()); 450 451 /* 452 * Copy kernel mappings over when needed. This can also 453 * happen within a race in page table update. In the later 454 * case just flush: 455 */ 456 pgd = (pgd_t *)__va(read_cr3_pa()) + pgd_index(address); 457 pgd_ref = pgd_offset_k(address); 458 if (pgd_none(*pgd_ref)) 459 return -1; 460 461 if (pgd_none(*pgd)) { 462 set_pgd(pgd, *pgd_ref); 463 arch_flush_lazy_mmu_mode(); 464 } else if (CONFIG_PGTABLE_LEVELS > 4) { 465 /* 466 * With folded p4d, pgd_none() is always false, so the pgd may 467 * point to an empty page table entry and pgd_page_vaddr() 468 * will return garbage. 469 * 470 * We will do the correct sanity check on the p4d level. 471 */ 472 BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref)); 473 } 474 475 /* With 4-level paging, copying happens on the p4d level. */ 476 p4d = p4d_offset(pgd, address); 477 p4d_ref = p4d_offset(pgd_ref, address); 478 if (p4d_none(*p4d_ref)) 479 return -1; 480 481 if (p4d_none(*p4d)) { 482 set_p4d(p4d, *p4d_ref); 483 arch_flush_lazy_mmu_mode(); 484 } else { 485 BUG_ON(p4d_pfn(*p4d) != p4d_pfn(*p4d_ref)); 486 } 487 488 /* 489 * Below here mismatches are bugs because these lower tables 490 * are shared: 491 */ 492 493 pud = pud_offset(p4d, address); 494 pud_ref = pud_offset(p4d_ref, address); 495 if (pud_none(*pud_ref)) 496 return -1; 497 498 if (pud_none(*pud) || pud_pfn(*pud) != pud_pfn(*pud_ref)) 499 BUG(); 500 501 if (pud_huge(*pud)) 502 return 0; 503 504 pmd = pmd_offset(pud, address); 505 pmd_ref = pmd_offset(pud_ref, address); 506 if (pmd_none(*pmd_ref)) 507 return -1; 508 509 if (pmd_none(*pmd) || pmd_pfn(*pmd) != pmd_pfn(*pmd_ref)) 510 BUG(); 511 512 if (pmd_huge(*pmd)) 513 return 0; 514 515 pte_ref = pte_offset_kernel(pmd_ref, address); 516 if (!pte_present(*pte_ref)) 517 return -1; 518 519 pte = pte_offset_kernel(pmd, address); 520 521 /* 522 * Don't use pte_page here, because the mappings can point 523 * outside mem_map, and the NUMA hash lookup cannot handle 524 * that: 525 */ 526 if (!pte_present(*pte) || pte_pfn(*pte) != pte_pfn(*pte_ref)) 527 BUG(); 528 529 return 0; 530 } 531 NOKPROBE_SYMBOL(vmalloc_fault); 532 533 #ifdef CONFIG_CPU_SUP_AMD 534 static const char errata93_warning[] = 535 KERN_ERR 536 "******* Your BIOS seems to not contain a fix for K8 errata #93\n" 537 "******* Working around it, but it may cause SEGVs or burn power.\n" 538 "******* Please consider a BIOS update.\n" 539 "******* Disabling USB legacy in the BIOS may also help.\n"; 540 #endif 541 542 /* 543 * No vm86 mode in 64-bit mode: 544 */ 545 static inline void 546 check_v8086_mode(struct pt_regs *regs, unsigned long address, 547 struct task_struct *tsk) 548 { 549 } 550 551 static int bad_address(void *p) 552 { 553 unsigned long dummy; 554 555 return probe_kernel_address((unsigned long *)p, dummy); 556 } 557 558 static void dump_pagetable(unsigned long address) 559 { 560 pgd_t *base = __va(read_cr3_pa()); 561 pgd_t *pgd = base + pgd_index(address); 562 p4d_t *p4d; 563 pud_t *pud; 564 pmd_t *pmd; 565 pte_t *pte; 566 567 if (bad_address(pgd)) 568 goto bad; 569 570 pr_info("PGD %lx ", pgd_val(*pgd)); 571 572 if (!pgd_present(*pgd)) 573 goto out; 574 575 p4d = p4d_offset(pgd, address); 576 if (bad_address(p4d)) 577 goto bad; 578 579 pr_cont("P4D %lx ", p4d_val(*p4d)); 580 if (!p4d_present(*p4d) || p4d_large(*p4d)) 581 goto out; 582 583 pud = pud_offset(p4d, address); 584 if (bad_address(pud)) 585 goto bad; 586 587 pr_cont("PUD %lx ", pud_val(*pud)); 588 if (!pud_present(*pud) || pud_large(*pud)) 589 goto out; 590 591 pmd = pmd_offset(pud, address); 592 if (bad_address(pmd)) 593 goto bad; 594 595 pr_cont("PMD %lx ", pmd_val(*pmd)); 596 if (!pmd_present(*pmd) || pmd_large(*pmd)) 597 goto out; 598 599 pte = pte_offset_kernel(pmd, address); 600 if (bad_address(pte)) 601 goto bad; 602 603 pr_cont("PTE %lx", pte_val(*pte)); 604 out: 605 pr_cont("\n"); 606 return; 607 bad: 608 pr_info("BAD\n"); 609 } 610 611 #endif /* CONFIG_X86_64 */ 612 613 /* 614 * Workaround for K8 erratum #93 & buggy BIOS. 615 * 616 * BIOS SMM functions are required to use a specific workaround 617 * to avoid corruption of the 64bit RIP register on C stepping K8. 618 * 619 * A lot of BIOS that didn't get tested properly miss this. 620 * 621 * The OS sees this as a page fault with the upper 32bits of RIP cleared. 622 * Try to work around it here. 623 * 624 * Note we only handle faults in kernel here. 625 * Does nothing on 32-bit. 626 */ 627 static int is_errata93(struct pt_regs *regs, unsigned long address) 628 { 629 #if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD) 630 if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD 631 || boot_cpu_data.x86 != 0xf) 632 return 0; 633 634 if (address != regs->ip) 635 return 0; 636 637 if ((address >> 32) != 0) 638 return 0; 639 640 address |= 0xffffffffUL << 32; 641 if ((address >= (u64)_stext && address <= (u64)_etext) || 642 (address >= MODULES_VADDR && address <= MODULES_END)) { 643 printk_once(errata93_warning); 644 regs->ip = address; 645 return 1; 646 } 647 #endif 648 return 0; 649 } 650 651 /* 652 * Work around K8 erratum #100 K8 in compat mode occasionally jumps 653 * to illegal addresses >4GB. 654 * 655 * We catch this in the page fault handler because these addresses 656 * are not reachable. Just detect this case and return. Any code 657 * segment in LDT is compatibility mode. 658 */ 659 static int is_errata100(struct pt_regs *regs, unsigned long address) 660 { 661 #ifdef CONFIG_X86_64 662 if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32)) 663 return 1; 664 #endif 665 return 0; 666 } 667 668 static int is_f00f_bug(struct pt_regs *regs, unsigned long address) 669 { 670 #ifdef CONFIG_X86_F00F_BUG 671 unsigned long nr; 672 673 /* 674 * Pentium F0 0F C7 C8 bug workaround: 675 */ 676 if (boot_cpu_has_bug(X86_BUG_F00F)) { 677 nr = (address - idt_descr.address) >> 3; 678 679 if (nr == 6) { 680 do_invalid_op(regs, 0); 681 return 1; 682 } 683 } 684 #endif 685 return 0; 686 } 687 688 static const char nx_warning[] = KERN_CRIT 689 "kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n"; 690 static const char smep_warning[] = KERN_CRIT 691 "unable to execute userspace code (SMEP?) (uid: %d)\n"; 692 693 static void 694 show_fault_oops(struct pt_regs *regs, unsigned long error_code, 695 unsigned long address) 696 { 697 if (!oops_may_print()) 698 return; 699 700 if (error_code & PF_INSTR) { 701 unsigned int level; 702 pgd_t *pgd; 703 pte_t *pte; 704 705 pgd = __va(read_cr3_pa()); 706 pgd += pgd_index(address); 707 708 pte = lookup_address_in_pgd(pgd, address, &level); 709 710 if (pte && pte_present(*pte) && !pte_exec(*pte)) 711 printk(nx_warning, from_kuid(&init_user_ns, current_uid())); 712 if (pte && pte_present(*pte) && pte_exec(*pte) && 713 (pgd_flags(*pgd) & _PAGE_USER) && 714 (__read_cr4() & X86_CR4_SMEP)) 715 printk(smep_warning, from_kuid(&init_user_ns, current_uid())); 716 } 717 718 printk(KERN_ALERT "BUG: unable to handle kernel "); 719 if (address < PAGE_SIZE) 720 printk(KERN_CONT "NULL pointer dereference"); 721 else 722 printk(KERN_CONT "paging request"); 723 724 printk(KERN_CONT " at %p\n", (void *) address); 725 printk(KERN_ALERT "IP: %pS\n", (void *)regs->ip); 726 727 dump_pagetable(address); 728 } 729 730 static noinline void 731 pgtable_bad(struct pt_regs *regs, unsigned long error_code, 732 unsigned long address) 733 { 734 struct task_struct *tsk; 735 unsigned long flags; 736 int sig; 737 738 flags = oops_begin(); 739 tsk = current; 740 sig = SIGKILL; 741 742 printk(KERN_ALERT "%s: Corrupted page table at address %lx\n", 743 tsk->comm, address); 744 dump_pagetable(address); 745 746 tsk->thread.cr2 = address; 747 tsk->thread.trap_nr = X86_TRAP_PF; 748 tsk->thread.error_code = error_code; 749 750 if (__die("Bad pagetable", regs, error_code)) 751 sig = 0; 752 753 oops_end(flags, regs, sig); 754 } 755 756 static noinline void 757 no_context(struct pt_regs *regs, unsigned long error_code, 758 unsigned long address, int signal, int si_code) 759 { 760 struct task_struct *tsk = current; 761 unsigned long flags; 762 int sig; 763 764 /* Are we prepared to handle this kernel fault? */ 765 if (fixup_exception(regs, X86_TRAP_PF)) { 766 /* 767 * Any interrupt that takes a fault gets the fixup. This makes 768 * the below recursive fault logic only apply to a faults from 769 * task context. 770 */ 771 if (in_interrupt()) 772 return; 773 774 /* 775 * Per the above we're !in_interrupt(), aka. task context. 776 * 777 * In this case we need to make sure we're not recursively 778 * faulting through the emulate_vsyscall() logic. 779 */ 780 if (current->thread.sig_on_uaccess_err && signal) { 781 tsk->thread.trap_nr = X86_TRAP_PF; 782 tsk->thread.error_code = error_code | PF_USER; 783 tsk->thread.cr2 = address; 784 785 /* XXX: hwpoison faults will set the wrong code. */ 786 force_sig_info_fault(signal, si_code, address, 787 tsk, NULL, 0); 788 } 789 790 /* 791 * Barring that, we can do the fixup and be happy. 792 */ 793 return; 794 } 795 796 #ifdef CONFIG_VMAP_STACK 797 /* 798 * Stack overflow? During boot, we can fault near the initial 799 * stack in the direct map, but that's not an overflow -- check 800 * that we're in vmalloc space to avoid this. 801 */ 802 if (is_vmalloc_addr((void *)address) && 803 (((unsigned long)tsk->stack - 1 - address < PAGE_SIZE) || 804 address - ((unsigned long)tsk->stack + THREAD_SIZE) < PAGE_SIZE)) { 805 unsigned long stack = this_cpu_read(orig_ist.ist[DOUBLEFAULT_STACK]) - sizeof(void *); 806 /* 807 * We're likely to be running with very little stack space 808 * left. It's plausible that we'd hit this condition but 809 * double-fault even before we get this far, in which case 810 * we're fine: the double-fault handler will deal with it. 811 * 812 * We don't want to make it all the way into the oops code 813 * and then double-fault, though, because we're likely to 814 * break the console driver and lose most of the stack dump. 815 */ 816 asm volatile ("movq %[stack], %%rsp\n\t" 817 "call handle_stack_overflow\n\t" 818 "1: jmp 1b" 819 : ASM_CALL_CONSTRAINT 820 : "D" ("kernel stack overflow (page fault)"), 821 "S" (regs), "d" (address), 822 [stack] "rm" (stack)); 823 unreachable(); 824 } 825 #endif 826 827 /* 828 * 32-bit: 829 * 830 * Valid to do another page fault here, because if this fault 831 * had been triggered by is_prefetch fixup_exception would have 832 * handled it. 833 * 834 * 64-bit: 835 * 836 * Hall of shame of CPU/BIOS bugs. 837 */ 838 if (is_prefetch(regs, error_code, address)) 839 return; 840 841 if (is_errata93(regs, address)) 842 return; 843 844 /* 845 * Oops. The kernel tried to access some bad page. We'll have to 846 * terminate things with extreme prejudice: 847 */ 848 flags = oops_begin(); 849 850 show_fault_oops(regs, error_code, address); 851 852 if (task_stack_end_corrupted(tsk)) 853 printk(KERN_EMERG "Thread overran stack, or stack corrupted\n"); 854 855 tsk->thread.cr2 = address; 856 tsk->thread.trap_nr = X86_TRAP_PF; 857 tsk->thread.error_code = error_code; 858 859 sig = SIGKILL; 860 if (__die("Oops", regs, error_code)) 861 sig = 0; 862 863 /* Executive summary in case the body of the oops scrolled away */ 864 printk(KERN_DEFAULT "CR2: %016lx\n", address); 865 866 oops_end(flags, regs, sig); 867 } 868 869 /* 870 * Print out info about fatal segfaults, if the show_unhandled_signals 871 * sysctl is set: 872 */ 873 static inline void 874 show_signal_msg(struct pt_regs *regs, unsigned long error_code, 875 unsigned long address, struct task_struct *tsk) 876 { 877 if (!unhandled_signal(tsk, SIGSEGV)) 878 return; 879 880 if (!printk_ratelimit()) 881 return; 882 883 printk("%s%s[%d]: segfault at %lx ip %p sp %p error %lx", 884 task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG, 885 tsk->comm, task_pid_nr(tsk), address, 886 (void *)regs->ip, (void *)regs->sp, error_code); 887 888 print_vma_addr(KERN_CONT " in ", regs->ip); 889 890 printk(KERN_CONT "\n"); 891 } 892 893 static void 894 __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code, 895 unsigned long address, u32 *pkey, int si_code) 896 { 897 struct task_struct *tsk = current; 898 899 /* User mode accesses just cause a SIGSEGV */ 900 if (error_code & PF_USER) { 901 /* 902 * It's possible to have interrupts off here: 903 */ 904 local_irq_enable(); 905 906 /* 907 * Valid to do another page fault here because this one came 908 * from user space: 909 */ 910 if (is_prefetch(regs, error_code, address)) 911 return; 912 913 if (is_errata100(regs, address)) 914 return; 915 916 #ifdef CONFIG_X86_64 917 /* 918 * Instruction fetch faults in the vsyscall page might need 919 * emulation. 920 */ 921 if (unlikely((error_code & PF_INSTR) && 922 ((address & ~0xfff) == VSYSCALL_ADDR))) { 923 if (emulate_vsyscall(regs, address)) 924 return; 925 } 926 #endif 927 928 /* 929 * To avoid leaking information about the kernel page table 930 * layout, pretend that user-mode accesses to kernel addresses 931 * are always protection faults. 932 */ 933 if (address >= TASK_SIZE_MAX) 934 error_code |= PF_PROT; 935 936 if (likely(show_unhandled_signals)) 937 show_signal_msg(regs, error_code, address, tsk); 938 939 tsk->thread.cr2 = address; 940 tsk->thread.error_code = error_code; 941 tsk->thread.trap_nr = X86_TRAP_PF; 942 943 force_sig_info_fault(SIGSEGV, si_code, address, tsk, pkey, 0); 944 945 return; 946 } 947 948 if (is_f00f_bug(regs, address)) 949 return; 950 951 no_context(regs, error_code, address, SIGSEGV, si_code); 952 } 953 954 static noinline void 955 bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code, 956 unsigned long address, u32 *pkey) 957 { 958 __bad_area_nosemaphore(regs, error_code, address, pkey, SEGV_MAPERR); 959 } 960 961 static void 962 __bad_area(struct pt_regs *regs, unsigned long error_code, 963 unsigned long address, struct vm_area_struct *vma, int si_code) 964 { 965 struct mm_struct *mm = current->mm; 966 u32 pkey; 967 968 if (vma) 969 pkey = vma_pkey(vma); 970 971 /* 972 * Something tried to access memory that isn't in our memory map.. 973 * Fix it, but check if it's kernel or user first.. 974 */ 975 up_read(&mm->mmap_sem); 976 977 __bad_area_nosemaphore(regs, error_code, address, 978 (vma) ? &pkey : NULL, si_code); 979 } 980 981 static noinline void 982 bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address) 983 { 984 __bad_area(regs, error_code, address, NULL, SEGV_MAPERR); 985 } 986 987 static inline bool bad_area_access_from_pkeys(unsigned long error_code, 988 struct vm_area_struct *vma) 989 { 990 /* This code is always called on the current mm */ 991 bool foreign = false; 992 993 if (!boot_cpu_has(X86_FEATURE_OSPKE)) 994 return false; 995 if (error_code & PF_PK) 996 return true; 997 /* this checks permission keys on the VMA: */ 998 if (!arch_vma_access_permitted(vma, (error_code & PF_WRITE), 999 (error_code & PF_INSTR), foreign)) 1000 return true; 1001 return false; 1002 } 1003 1004 static noinline void 1005 bad_area_access_error(struct pt_regs *regs, unsigned long error_code, 1006 unsigned long address, struct vm_area_struct *vma) 1007 { 1008 /* 1009 * This OSPKE check is not strictly necessary at runtime. 1010 * But, doing it this way allows compiler optimizations 1011 * if pkeys are compiled out. 1012 */ 1013 if (bad_area_access_from_pkeys(error_code, vma)) 1014 __bad_area(regs, error_code, address, vma, SEGV_PKUERR); 1015 else 1016 __bad_area(regs, error_code, address, vma, SEGV_ACCERR); 1017 } 1018 1019 static void 1020 do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address, 1021 u32 *pkey, unsigned int fault) 1022 { 1023 struct task_struct *tsk = current; 1024 int code = BUS_ADRERR; 1025 1026 /* Kernel mode? Handle exceptions or die: */ 1027 if (!(error_code & PF_USER)) { 1028 no_context(regs, error_code, address, SIGBUS, BUS_ADRERR); 1029 return; 1030 } 1031 1032 /* User-space => ok to do another page fault: */ 1033 if (is_prefetch(regs, error_code, address)) 1034 return; 1035 1036 tsk->thread.cr2 = address; 1037 tsk->thread.error_code = error_code; 1038 tsk->thread.trap_nr = X86_TRAP_PF; 1039 1040 #ifdef CONFIG_MEMORY_FAILURE 1041 if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) { 1042 printk(KERN_ERR 1043 "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n", 1044 tsk->comm, tsk->pid, address); 1045 code = BUS_MCEERR_AR; 1046 } 1047 #endif 1048 force_sig_info_fault(SIGBUS, code, address, tsk, pkey, fault); 1049 } 1050 1051 static noinline void 1052 mm_fault_error(struct pt_regs *regs, unsigned long error_code, 1053 unsigned long address, u32 *pkey, unsigned int fault) 1054 { 1055 if (fatal_signal_pending(current) && !(error_code & PF_USER)) { 1056 no_context(regs, error_code, address, 0, 0); 1057 return; 1058 } 1059 1060 if (fault & VM_FAULT_OOM) { 1061 /* Kernel mode? Handle exceptions or die: */ 1062 if (!(error_code & PF_USER)) { 1063 no_context(regs, error_code, address, 1064 SIGSEGV, SEGV_MAPERR); 1065 return; 1066 } 1067 1068 /* 1069 * We ran out of memory, call the OOM killer, and return the 1070 * userspace (which will retry the fault, or kill us if we got 1071 * oom-killed): 1072 */ 1073 pagefault_out_of_memory(); 1074 } else { 1075 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON| 1076 VM_FAULT_HWPOISON_LARGE)) 1077 do_sigbus(regs, error_code, address, pkey, fault); 1078 else if (fault & VM_FAULT_SIGSEGV) 1079 bad_area_nosemaphore(regs, error_code, address, pkey); 1080 else 1081 BUG(); 1082 } 1083 } 1084 1085 static int spurious_fault_check(unsigned long error_code, pte_t *pte) 1086 { 1087 if ((error_code & PF_WRITE) && !pte_write(*pte)) 1088 return 0; 1089 1090 if ((error_code & PF_INSTR) && !pte_exec(*pte)) 1091 return 0; 1092 /* 1093 * Note: We do not do lazy flushing on protection key 1094 * changes, so no spurious fault will ever set PF_PK. 1095 */ 1096 if ((error_code & PF_PK)) 1097 return 1; 1098 1099 return 1; 1100 } 1101 1102 /* 1103 * Handle a spurious fault caused by a stale TLB entry. 1104 * 1105 * This allows us to lazily refresh the TLB when increasing the 1106 * permissions of a kernel page (RO -> RW or NX -> X). Doing it 1107 * eagerly is very expensive since that implies doing a full 1108 * cross-processor TLB flush, even if no stale TLB entries exist 1109 * on other processors. 1110 * 1111 * Spurious faults may only occur if the TLB contains an entry with 1112 * fewer permission than the page table entry. Non-present (P = 0) 1113 * and reserved bit (R = 1) faults are never spurious. 1114 * 1115 * There are no security implications to leaving a stale TLB when 1116 * increasing the permissions on a page. 1117 * 1118 * Returns non-zero if a spurious fault was handled, zero otherwise. 1119 * 1120 * See Intel Developer's Manual Vol 3 Section 4.10.4.3, bullet 3 1121 * (Optional Invalidation). 1122 */ 1123 static noinline int 1124 spurious_fault(unsigned long error_code, unsigned long address) 1125 { 1126 pgd_t *pgd; 1127 p4d_t *p4d; 1128 pud_t *pud; 1129 pmd_t *pmd; 1130 pte_t *pte; 1131 int ret; 1132 1133 /* 1134 * Only writes to RO or instruction fetches from NX may cause 1135 * spurious faults. 1136 * 1137 * These could be from user or supervisor accesses but the TLB 1138 * is only lazily flushed after a kernel mapping protection 1139 * change, so user accesses are not expected to cause spurious 1140 * faults. 1141 */ 1142 if (error_code != (PF_WRITE | PF_PROT) 1143 && error_code != (PF_INSTR | PF_PROT)) 1144 return 0; 1145 1146 pgd = init_mm.pgd + pgd_index(address); 1147 if (!pgd_present(*pgd)) 1148 return 0; 1149 1150 p4d = p4d_offset(pgd, address); 1151 if (!p4d_present(*p4d)) 1152 return 0; 1153 1154 if (p4d_large(*p4d)) 1155 return spurious_fault_check(error_code, (pte_t *) p4d); 1156 1157 pud = pud_offset(p4d, address); 1158 if (!pud_present(*pud)) 1159 return 0; 1160 1161 if (pud_large(*pud)) 1162 return spurious_fault_check(error_code, (pte_t *) pud); 1163 1164 pmd = pmd_offset(pud, address); 1165 if (!pmd_present(*pmd)) 1166 return 0; 1167 1168 if (pmd_large(*pmd)) 1169 return spurious_fault_check(error_code, (pte_t *) pmd); 1170 1171 pte = pte_offset_kernel(pmd, address); 1172 if (!pte_present(*pte)) 1173 return 0; 1174 1175 ret = spurious_fault_check(error_code, pte); 1176 if (!ret) 1177 return 0; 1178 1179 /* 1180 * Make sure we have permissions in PMD. 1181 * If not, then there's a bug in the page tables: 1182 */ 1183 ret = spurious_fault_check(error_code, (pte_t *) pmd); 1184 WARN_ONCE(!ret, "PMD has incorrect permission bits\n"); 1185 1186 return ret; 1187 } 1188 NOKPROBE_SYMBOL(spurious_fault); 1189 1190 int show_unhandled_signals = 1; 1191 1192 static inline int 1193 access_error(unsigned long error_code, struct vm_area_struct *vma) 1194 { 1195 /* This is only called for the current mm, so: */ 1196 bool foreign = false; 1197 1198 /* 1199 * Read or write was blocked by protection keys. This is 1200 * always an unconditional error and can never result in 1201 * a follow-up action to resolve the fault, like a COW. 1202 */ 1203 if (error_code & PF_PK) 1204 return 1; 1205 1206 /* 1207 * Make sure to check the VMA so that we do not perform 1208 * faults just to hit a PF_PK as soon as we fill in a 1209 * page. 1210 */ 1211 if (!arch_vma_access_permitted(vma, (error_code & PF_WRITE), 1212 (error_code & PF_INSTR), foreign)) 1213 return 1; 1214 1215 if (error_code & PF_WRITE) { 1216 /* write, present and write, not present: */ 1217 if (unlikely(!(vma->vm_flags & VM_WRITE))) 1218 return 1; 1219 return 0; 1220 } 1221 1222 /* read, present: */ 1223 if (unlikely(error_code & PF_PROT)) 1224 return 1; 1225 1226 /* read, not present: */ 1227 if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))) 1228 return 1; 1229 1230 return 0; 1231 } 1232 1233 static int fault_in_kernel_space(unsigned long address) 1234 { 1235 return address >= TASK_SIZE_MAX; 1236 } 1237 1238 static inline bool smap_violation(int error_code, struct pt_regs *regs) 1239 { 1240 if (!IS_ENABLED(CONFIG_X86_SMAP)) 1241 return false; 1242 1243 if (!static_cpu_has(X86_FEATURE_SMAP)) 1244 return false; 1245 1246 if (error_code & PF_USER) 1247 return false; 1248 1249 if (!user_mode(regs) && (regs->flags & X86_EFLAGS_AC)) 1250 return false; 1251 1252 return true; 1253 } 1254 1255 /* 1256 * This routine handles page faults. It determines the address, 1257 * and the problem, and then passes it off to one of the appropriate 1258 * routines. 1259 */ 1260 static noinline void 1261 __do_page_fault(struct pt_regs *regs, unsigned long error_code, 1262 unsigned long address) 1263 { 1264 struct vm_area_struct *vma; 1265 struct task_struct *tsk; 1266 struct mm_struct *mm; 1267 int fault, major = 0; 1268 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; 1269 u32 pkey; 1270 1271 tsk = current; 1272 mm = tsk->mm; 1273 1274 /* 1275 * Detect and handle instructions that would cause a page fault for 1276 * both a tracked kernel page and a userspace page. 1277 */ 1278 if (kmemcheck_active(regs)) 1279 kmemcheck_hide(regs); 1280 prefetchw(&mm->mmap_sem); 1281 1282 if (unlikely(kmmio_fault(regs, address))) 1283 return; 1284 1285 /* 1286 * We fault-in kernel-space virtual memory on-demand. The 1287 * 'reference' page table is init_mm.pgd. 1288 * 1289 * NOTE! We MUST NOT take any locks for this case. We may 1290 * be in an interrupt or a critical region, and should 1291 * only copy the information from the master page table, 1292 * nothing more. 1293 * 1294 * This verifies that the fault happens in kernel space 1295 * (error_code & 4) == 0, and that the fault was not a 1296 * protection error (error_code & 9) == 0. 1297 */ 1298 if (unlikely(fault_in_kernel_space(address))) { 1299 if (!(error_code & (PF_RSVD | PF_USER | PF_PROT))) { 1300 if (vmalloc_fault(address) >= 0) 1301 return; 1302 1303 if (kmemcheck_fault(regs, address, error_code)) 1304 return; 1305 } 1306 1307 /* Can handle a stale RO->RW TLB: */ 1308 if (spurious_fault(error_code, address)) 1309 return; 1310 1311 /* kprobes don't want to hook the spurious faults: */ 1312 if (kprobes_fault(regs)) 1313 return; 1314 /* 1315 * Don't take the mm semaphore here. If we fixup a prefetch 1316 * fault we could otherwise deadlock: 1317 */ 1318 bad_area_nosemaphore(regs, error_code, address, NULL); 1319 1320 return; 1321 } 1322 1323 /* kprobes don't want to hook the spurious faults: */ 1324 if (unlikely(kprobes_fault(regs))) 1325 return; 1326 1327 if (unlikely(error_code & PF_RSVD)) 1328 pgtable_bad(regs, error_code, address); 1329 1330 if (unlikely(smap_violation(error_code, regs))) { 1331 bad_area_nosemaphore(regs, error_code, address, NULL); 1332 return; 1333 } 1334 1335 /* 1336 * If we're in an interrupt, have no user context or are running 1337 * in a region with pagefaults disabled then we must not take the fault 1338 */ 1339 if (unlikely(faulthandler_disabled() || !mm)) { 1340 bad_area_nosemaphore(regs, error_code, address, NULL); 1341 return; 1342 } 1343 1344 /* 1345 * It's safe to allow irq's after cr2 has been saved and the 1346 * vmalloc fault has been handled. 1347 * 1348 * User-mode registers count as a user access even for any 1349 * potential system fault or CPU buglet: 1350 */ 1351 if (user_mode(regs)) { 1352 local_irq_enable(); 1353 error_code |= PF_USER; 1354 flags |= FAULT_FLAG_USER; 1355 } else { 1356 if (regs->flags & X86_EFLAGS_IF) 1357 local_irq_enable(); 1358 } 1359 1360 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 1361 1362 if (error_code & PF_WRITE) 1363 flags |= FAULT_FLAG_WRITE; 1364 if (error_code & PF_INSTR) 1365 flags |= FAULT_FLAG_INSTRUCTION; 1366 1367 /* 1368 * When running in the kernel we expect faults to occur only to 1369 * addresses in user space. All other faults represent errors in 1370 * the kernel and should generate an OOPS. Unfortunately, in the 1371 * case of an erroneous fault occurring in a code path which already 1372 * holds mmap_sem we will deadlock attempting to validate the fault 1373 * against the address space. Luckily the kernel only validly 1374 * references user space from well defined areas of code, which are 1375 * listed in the exceptions table. 1376 * 1377 * As the vast majority of faults will be valid we will only perform 1378 * the source reference check when there is a possibility of a 1379 * deadlock. Attempt to lock the address space, if we cannot we then 1380 * validate the source. If this is invalid we can skip the address 1381 * space check, thus avoiding the deadlock: 1382 */ 1383 if (unlikely(!down_read_trylock(&mm->mmap_sem))) { 1384 if ((error_code & PF_USER) == 0 && 1385 !search_exception_tables(regs->ip)) { 1386 bad_area_nosemaphore(regs, error_code, address, NULL); 1387 return; 1388 } 1389 retry: 1390 down_read(&mm->mmap_sem); 1391 } else { 1392 /* 1393 * The above down_read_trylock() might have succeeded in 1394 * which case we'll have missed the might_sleep() from 1395 * down_read(): 1396 */ 1397 might_sleep(); 1398 } 1399 1400 vma = find_vma(mm, address); 1401 if (unlikely(!vma)) { 1402 bad_area(regs, error_code, address); 1403 return; 1404 } 1405 if (likely(vma->vm_start <= address)) 1406 goto good_area; 1407 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) { 1408 bad_area(regs, error_code, address); 1409 return; 1410 } 1411 if (error_code & PF_USER) { 1412 /* 1413 * Accessing the stack below %sp is always a bug. 1414 * The large cushion allows instructions like enter 1415 * and pusha to work. ("enter $65535, $31" pushes 1416 * 32 pointers and then decrements %sp by 65535.) 1417 */ 1418 if (unlikely(address + 65536 + 32 * sizeof(unsigned long) < regs->sp)) { 1419 bad_area(regs, error_code, address); 1420 return; 1421 } 1422 } 1423 if (unlikely(expand_stack(vma, address))) { 1424 bad_area(regs, error_code, address); 1425 return; 1426 } 1427 1428 /* 1429 * Ok, we have a good vm_area for this memory access, so 1430 * we can handle it.. 1431 */ 1432 good_area: 1433 if (unlikely(access_error(error_code, vma))) { 1434 bad_area_access_error(regs, error_code, address, vma); 1435 return; 1436 } 1437 1438 /* 1439 * If for any reason at all we couldn't handle the fault, 1440 * make sure we exit gracefully rather than endlessly redo 1441 * the fault. Since we never set FAULT_FLAG_RETRY_NOWAIT, if 1442 * we get VM_FAULT_RETRY back, the mmap_sem has been unlocked. 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, error_code, address, SIGBUS, BUS_ADRERR); 1467 return; 1468 } 1469 1470 pkey = vma_pkey(vma); 1471 up_read(&mm->mmap_sem); 1472 if (unlikely(fault & VM_FAULT_ERROR)) { 1473 mm_fault_error(regs, error_code, address, &pkey, fault); 1474 return; 1475 } 1476 1477 /* 1478 * Major/minor page fault accounting. If any of the events 1479 * returned VM_FAULT_MAJOR, we account it as a major fault. 1480 */ 1481 if (major) { 1482 tsk->maj_flt++; 1483 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address); 1484 } else { 1485 tsk->min_flt++; 1486 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address); 1487 } 1488 1489 check_v8086_mode(regs, address, tsk); 1490 } 1491 NOKPROBE_SYMBOL(__do_page_fault); 1492 1493 static nokprobe_inline void 1494 trace_page_fault_entries(unsigned long address, struct pt_regs *regs, 1495 unsigned long error_code) 1496 { 1497 if (user_mode(regs)) 1498 trace_page_fault_user(address, regs, error_code); 1499 else 1500 trace_page_fault_kernel(address, regs, error_code); 1501 } 1502 1503 /* 1504 * We must have this function blacklisted from kprobes, tagged with notrace 1505 * and call read_cr2() before calling anything else. To avoid calling any 1506 * kind of tracing machinery before we've observed the CR2 value. 1507 * 1508 * exception_{enter,exit}() contains all sorts of tracepoints. 1509 */ 1510 dotraplinkage void notrace 1511 do_page_fault(struct pt_regs *regs, unsigned long error_code) 1512 { 1513 unsigned long address = read_cr2(); /* Get the faulting address */ 1514 enum ctx_state prev_state; 1515 1516 prev_state = exception_enter(); 1517 if (trace_pagefault_enabled()) 1518 trace_page_fault_entries(address, regs, error_code); 1519 1520 __do_page_fault(regs, error_code, address); 1521 exception_exit(prev_state); 1522 } 1523 NOKPROBE_SYMBOL(do_page_fault); 1524