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 34 #define CREATE_TRACE_POINTS 35 #include <asm/trace/exceptions.h> 36 37 /* 38 * Returns 0 if mmiotrace is disabled, or if the fault is not 39 * handled by mmiotrace: 40 */ 41 static nokprobe_inline int 42 kmmio_fault(struct pt_regs *regs, unsigned long addr) 43 { 44 if (unlikely(is_kmmio_active())) 45 if (kmmio_handler(regs, addr) == 1) 46 return -1; 47 return 0; 48 } 49 50 /* 51 * Prefetch quirks: 52 * 53 * 32-bit mode: 54 * 55 * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch. 56 * Check that here and ignore it. 57 * 58 * 64-bit mode: 59 * 60 * Sometimes the CPU reports invalid exceptions on prefetch. 61 * Check that here and ignore it. 62 * 63 * Opcode checker based on code by Richard Brunner. 64 */ 65 static inline int 66 check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr, 67 unsigned char opcode, int *prefetch) 68 { 69 unsigned char instr_hi = opcode & 0xf0; 70 unsigned char instr_lo = opcode & 0x0f; 71 72 switch (instr_hi) { 73 case 0x20: 74 case 0x30: 75 /* 76 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes. 77 * In X86_64 long mode, the CPU will signal invalid 78 * opcode if some of these prefixes are present so 79 * X86_64 will never get here anyway 80 */ 81 return ((instr_lo & 7) == 0x6); 82 #ifdef CONFIG_X86_64 83 case 0x40: 84 /* 85 * In AMD64 long mode 0x40..0x4F are valid REX prefixes 86 * Need to figure out under what instruction mode the 87 * instruction was issued. Could check the LDT for lm, 88 * but for now it's good enough to assume that long 89 * mode only uses well known segments or kernel. 90 */ 91 return (!user_mode(regs) || user_64bit_mode(regs)); 92 #endif 93 case 0x60: 94 /* 0x64 thru 0x67 are valid prefixes in all modes. */ 95 return (instr_lo & 0xC) == 0x4; 96 case 0xF0: 97 /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */ 98 return !instr_lo || (instr_lo>>1) == 1; 99 case 0x00: 100 /* Prefetch instruction is 0x0F0D or 0x0F18 */ 101 if (get_kernel_nofault(opcode, instr)) 102 return 0; 103 104 *prefetch = (instr_lo == 0xF) && 105 (opcode == 0x0D || opcode == 0x18); 106 return 0; 107 default: 108 return 0; 109 } 110 } 111 112 static int 113 is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr) 114 { 115 unsigned char *max_instr; 116 unsigned char *instr; 117 int prefetch = 0; 118 119 /* 120 * If it was a exec (instruction fetch) fault on NX page, then 121 * do not ignore the fault: 122 */ 123 if (error_code & X86_PF_INSTR) 124 return 0; 125 126 instr = (void *)convert_ip_to_linear(current, regs); 127 max_instr = instr + 15; 128 129 if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE_MAX) 130 return 0; 131 132 while (instr < max_instr) { 133 unsigned char opcode; 134 135 if (get_kernel_nofault(opcode, instr)) 136 break; 137 138 instr++; 139 140 if (!check_prefetch_opcode(regs, instr, opcode, &prefetch)) 141 break; 142 } 143 return prefetch; 144 } 145 146 DEFINE_SPINLOCK(pgd_lock); 147 LIST_HEAD(pgd_list); 148 149 #ifdef CONFIG_X86_32 150 static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address) 151 { 152 unsigned index = pgd_index(address); 153 pgd_t *pgd_k; 154 p4d_t *p4d, *p4d_k; 155 pud_t *pud, *pud_k; 156 pmd_t *pmd, *pmd_k; 157 158 pgd += index; 159 pgd_k = init_mm.pgd + index; 160 161 if (!pgd_present(*pgd_k)) 162 return NULL; 163 164 /* 165 * set_pgd(pgd, *pgd_k); here would be useless on PAE 166 * and redundant with the set_pmd() on non-PAE. As would 167 * set_p4d/set_pud. 168 */ 169 p4d = p4d_offset(pgd, address); 170 p4d_k = p4d_offset(pgd_k, address); 171 if (!p4d_present(*p4d_k)) 172 return NULL; 173 174 pud = pud_offset(p4d, address); 175 pud_k = pud_offset(p4d_k, address); 176 if (!pud_present(*pud_k)) 177 return NULL; 178 179 pmd = pmd_offset(pud, address); 180 pmd_k = pmd_offset(pud_k, address); 181 182 if (pmd_present(*pmd) != pmd_present(*pmd_k)) 183 set_pmd(pmd, *pmd_k); 184 185 if (!pmd_present(*pmd_k)) 186 return NULL; 187 else 188 BUG_ON(pmd_pfn(*pmd) != pmd_pfn(*pmd_k)); 189 190 return pmd_k; 191 } 192 193 /* 194 * Handle a fault on the vmalloc or module mapping area 195 * 196 * This is needed because there is a race condition between the time 197 * when the vmalloc mapping code updates the PMD to the point in time 198 * where it synchronizes this update with the other page-tables in the 199 * system. 200 * 201 * In this race window another thread/CPU can map an area on the same 202 * PMD, finds it already present and does not synchronize it with the 203 * rest of the system yet. As a result v[mz]alloc might return areas 204 * which are not mapped in every page-table in the system, causing an 205 * unhandled page-fault when they are accessed. 206 */ 207 static noinline int vmalloc_fault(unsigned long address) 208 { 209 unsigned long pgd_paddr; 210 pmd_t *pmd_k; 211 pte_t *pte_k; 212 213 /* Make sure we are in vmalloc area: */ 214 if (!(address >= VMALLOC_START && address < VMALLOC_END)) 215 return -1; 216 217 /* 218 * Synchronize this task's top level page-table 219 * with the 'reference' page table. 220 * 221 * Do _not_ use "current" here. We might be inside 222 * an interrupt in the middle of a task switch.. 223 */ 224 pgd_paddr = read_cr3_pa(); 225 pmd_k = vmalloc_sync_one(__va(pgd_paddr), address); 226 if (!pmd_k) 227 return -1; 228 229 if (pmd_large(*pmd_k)) 230 return 0; 231 232 pte_k = pte_offset_kernel(pmd_k, address); 233 if (!pte_present(*pte_k)) 234 return -1; 235 236 return 0; 237 } 238 NOKPROBE_SYMBOL(vmalloc_fault); 239 240 void arch_sync_kernel_mappings(unsigned long start, unsigned long end) 241 { 242 unsigned long addr; 243 244 for (addr = start & PMD_MASK; 245 addr >= TASK_SIZE_MAX && addr < VMALLOC_END; 246 addr += PMD_SIZE) { 247 struct page *page; 248 249 spin_lock(&pgd_lock); 250 list_for_each_entry(page, &pgd_list, lru) { 251 spinlock_t *pgt_lock; 252 253 /* the pgt_lock only for Xen */ 254 pgt_lock = &pgd_page_get_mm(page)->page_table_lock; 255 256 spin_lock(pgt_lock); 257 vmalloc_sync_one(page_address(page), addr); 258 spin_unlock(pgt_lock); 259 } 260 spin_unlock(&pgd_lock); 261 } 262 } 263 264 /* 265 * Did it hit the DOS screen memory VA from vm86 mode? 266 */ 267 static inline void 268 check_v8086_mode(struct pt_regs *regs, unsigned long address, 269 struct task_struct *tsk) 270 { 271 #ifdef CONFIG_VM86 272 unsigned long bit; 273 274 if (!v8086_mode(regs) || !tsk->thread.vm86) 275 return; 276 277 bit = (address - 0xA0000) >> PAGE_SHIFT; 278 if (bit < 32) 279 tsk->thread.vm86->screen_bitmap |= 1 << bit; 280 #endif 281 } 282 283 static bool low_pfn(unsigned long pfn) 284 { 285 return pfn < max_low_pfn; 286 } 287 288 static void dump_pagetable(unsigned long address) 289 { 290 pgd_t *base = __va(read_cr3_pa()); 291 pgd_t *pgd = &base[pgd_index(address)]; 292 p4d_t *p4d; 293 pud_t *pud; 294 pmd_t *pmd; 295 pte_t *pte; 296 297 #ifdef CONFIG_X86_PAE 298 pr_info("*pdpt = %016Lx ", pgd_val(*pgd)); 299 if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd)) 300 goto out; 301 #define pr_pde pr_cont 302 #else 303 #define pr_pde pr_info 304 #endif 305 p4d = p4d_offset(pgd, address); 306 pud = pud_offset(p4d, address); 307 pmd = pmd_offset(pud, address); 308 pr_pde("*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd)); 309 #undef pr_pde 310 311 /* 312 * We must not directly access the pte in the highpte 313 * case if the page table is located in highmem. 314 * And let's rather not kmap-atomic the pte, just in case 315 * it's allocated already: 316 */ 317 if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_large(*pmd)) 318 goto out; 319 320 pte = pte_offset_kernel(pmd, address); 321 pr_cont("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte)); 322 out: 323 pr_cont("\n"); 324 } 325 326 #else /* CONFIG_X86_64: */ 327 328 #ifdef CONFIG_CPU_SUP_AMD 329 static const char errata93_warning[] = 330 KERN_ERR 331 "******* Your BIOS seems to not contain a fix for K8 errata #93\n" 332 "******* Working around it, but it may cause SEGVs or burn power.\n" 333 "******* Please consider a BIOS update.\n" 334 "******* Disabling USB legacy in the BIOS may also help.\n"; 335 #endif 336 337 /* 338 * No vm86 mode in 64-bit mode: 339 */ 340 static inline void 341 check_v8086_mode(struct pt_regs *regs, unsigned long address, 342 struct task_struct *tsk) 343 { 344 } 345 346 static int bad_address(void *p) 347 { 348 unsigned long dummy; 349 350 return get_kernel_nofault(dummy, (unsigned long *)p); 351 } 352 353 static void dump_pagetable(unsigned long address) 354 { 355 pgd_t *base = __va(read_cr3_pa()); 356 pgd_t *pgd = base + pgd_index(address); 357 p4d_t *p4d; 358 pud_t *pud; 359 pmd_t *pmd; 360 pte_t *pte; 361 362 if (bad_address(pgd)) 363 goto bad; 364 365 pr_info("PGD %lx ", pgd_val(*pgd)); 366 367 if (!pgd_present(*pgd)) 368 goto out; 369 370 p4d = p4d_offset(pgd, address); 371 if (bad_address(p4d)) 372 goto bad; 373 374 pr_cont("P4D %lx ", p4d_val(*p4d)); 375 if (!p4d_present(*p4d) || p4d_large(*p4d)) 376 goto out; 377 378 pud = pud_offset(p4d, address); 379 if (bad_address(pud)) 380 goto bad; 381 382 pr_cont("PUD %lx ", pud_val(*pud)); 383 if (!pud_present(*pud) || pud_large(*pud)) 384 goto out; 385 386 pmd = pmd_offset(pud, address); 387 if (bad_address(pmd)) 388 goto bad; 389 390 pr_cont("PMD %lx ", pmd_val(*pmd)); 391 if (!pmd_present(*pmd) || pmd_large(*pmd)) 392 goto out; 393 394 pte = pte_offset_kernel(pmd, address); 395 if (bad_address(pte)) 396 goto bad; 397 398 pr_cont("PTE %lx", pte_val(*pte)); 399 out: 400 pr_cont("\n"); 401 return; 402 bad: 403 pr_info("BAD\n"); 404 } 405 406 #endif /* CONFIG_X86_64 */ 407 408 /* 409 * Workaround for K8 erratum #93 & buggy BIOS. 410 * 411 * BIOS SMM functions are required to use a specific workaround 412 * to avoid corruption of the 64bit RIP register on C stepping K8. 413 * 414 * A lot of BIOS that didn't get tested properly miss this. 415 * 416 * The OS sees this as a page fault with the upper 32bits of RIP cleared. 417 * Try to work around it here. 418 * 419 * Note we only handle faults in kernel here. 420 * Does nothing on 32-bit. 421 */ 422 static int is_errata93(struct pt_regs *regs, unsigned long address) 423 { 424 #if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD) 425 if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD 426 || boot_cpu_data.x86 != 0xf) 427 return 0; 428 429 if (address != regs->ip) 430 return 0; 431 432 if ((address >> 32) != 0) 433 return 0; 434 435 address |= 0xffffffffUL << 32; 436 if ((address >= (u64)_stext && address <= (u64)_etext) || 437 (address >= MODULES_VADDR && address <= MODULES_END)) { 438 printk_once(errata93_warning); 439 regs->ip = address; 440 return 1; 441 } 442 #endif 443 return 0; 444 } 445 446 /* 447 * Work around K8 erratum #100 K8 in compat mode occasionally jumps 448 * to illegal addresses >4GB. 449 * 450 * We catch this in the page fault handler because these addresses 451 * are not reachable. Just detect this case and return. Any code 452 * segment in LDT is compatibility mode. 453 */ 454 static int is_errata100(struct pt_regs *regs, unsigned long address) 455 { 456 #ifdef CONFIG_X86_64 457 if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32)) 458 return 1; 459 #endif 460 return 0; 461 } 462 463 /* Pentium F0 0F C7 C8 bug workaround: */ 464 static int is_f00f_bug(struct pt_regs *regs, unsigned long address) 465 { 466 #ifdef CONFIG_X86_F00F_BUG 467 if (boot_cpu_has_bug(X86_BUG_F00F) && idt_is_f00f_address(address)) { 468 handle_invalid_op(regs); 469 return 1; 470 } 471 #endif 472 return 0; 473 } 474 475 static void show_ldttss(const struct desc_ptr *gdt, const char *name, u16 index) 476 { 477 u32 offset = (index >> 3) * sizeof(struct desc_struct); 478 unsigned long addr; 479 struct ldttss_desc desc; 480 481 if (index == 0) { 482 pr_alert("%s: NULL\n", name); 483 return; 484 } 485 486 if (offset + sizeof(struct ldttss_desc) >= gdt->size) { 487 pr_alert("%s: 0x%hx -- out of bounds\n", name, index); 488 return; 489 } 490 491 if (copy_from_kernel_nofault(&desc, (void *)(gdt->address + offset), 492 sizeof(struct ldttss_desc))) { 493 pr_alert("%s: 0x%hx -- GDT entry is not readable\n", 494 name, index); 495 return; 496 } 497 498 addr = desc.base0 | (desc.base1 << 16) | ((unsigned long)desc.base2 << 24); 499 #ifdef CONFIG_X86_64 500 addr |= ((u64)desc.base3 << 32); 501 #endif 502 pr_alert("%s: 0x%hx -- base=0x%lx limit=0x%x\n", 503 name, index, addr, (desc.limit0 | (desc.limit1 << 16))); 504 } 505 506 static void 507 show_fault_oops(struct pt_regs *regs, unsigned long error_code, unsigned long address) 508 { 509 if (!oops_may_print()) 510 return; 511 512 if (error_code & X86_PF_INSTR) { 513 unsigned int level; 514 pgd_t *pgd; 515 pte_t *pte; 516 517 pgd = __va(read_cr3_pa()); 518 pgd += pgd_index(address); 519 520 pte = lookup_address_in_pgd(pgd, address, &level); 521 522 if (pte && pte_present(*pte) && !pte_exec(*pte)) 523 pr_crit("kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n", 524 from_kuid(&init_user_ns, current_uid())); 525 if (pte && pte_present(*pte) && pte_exec(*pte) && 526 (pgd_flags(*pgd) & _PAGE_USER) && 527 (__read_cr4() & X86_CR4_SMEP)) 528 pr_crit("unable to execute userspace code (SMEP?) (uid: %d)\n", 529 from_kuid(&init_user_ns, current_uid())); 530 } 531 532 if (address < PAGE_SIZE && !user_mode(regs)) 533 pr_alert("BUG: kernel NULL pointer dereference, address: %px\n", 534 (void *)address); 535 else 536 pr_alert("BUG: unable to handle page fault for address: %px\n", 537 (void *)address); 538 539 pr_alert("#PF: %s %s in %s mode\n", 540 (error_code & X86_PF_USER) ? "user" : "supervisor", 541 (error_code & X86_PF_INSTR) ? "instruction fetch" : 542 (error_code & X86_PF_WRITE) ? "write access" : 543 "read access", 544 user_mode(regs) ? "user" : "kernel"); 545 pr_alert("#PF: error_code(0x%04lx) - %s\n", error_code, 546 !(error_code & X86_PF_PROT) ? "not-present page" : 547 (error_code & X86_PF_RSVD) ? "reserved bit violation" : 548 (error_code & X86_PF_PK) ? "protection keys violation" : 549 "permissions violation"); 550 551 if (!(error_code & X86_PF_USER) && user_mode(regs)) { 552 struct desc_ptr idt, gdt; 553 u16 ldtr, tr; 554 555 /* 556 * This can happen for quite a few reasons. The more obvious 557 * ones are faults accessing the GDT, or LDT. Perhaps 558 * surprisingly, if the CPU tries to deliver a benign or 559 * contributory exception from user code and gets a page fault 560 * during delivery, the page fault can be delivered as though 561 * it originated directly from user code. This could happen 562 * due to wrong permissions on the IDT, GDT, LDT, TSS, or 563 * kernel or IST stack. 564 */ 565 store_idt(&idt); 566 567 /* Usable even on Xen PV -- it's just slow. */ 568 native_store_gdt(&gdt); 569 570 pr_alert("IDT: 0x%lx (limit=0x%hx) GDT: 0x%lx (limit=0x%hx)\n", 571 idt.address, idt.size, gdt.address, gdt.size); 572 573 store_ldt(ldtr); 574 show_ldttss(&gdt, "LDTR", ldtr); 575 576 store_tr(tr); 577 show_ldttss(&gdt, "TR", tr); 578 } 579 580 dump_pagetable(address); 581 } 582 583 static noinline void 584 pgtable_bad(struct pt_regs *regs, unsigned long error_code, 585 unsigned long address) 586 { 587 struct task_struct *tsk; 588 unsigned long flags; 589 int sig; 590 591 flags = oops_begin(); 592 tsk = current; 593 sig = SIGKILL; 594 595 printk(KERN_ALERT "%s: Corrupted page table at address %lx\n", 596 tsk->comm, address); 597 dump_pagetable(address); 598 599 if (__die("Bad pagetable", regs, error_code)) 600 sig = 0; 601 602 oops_end(flags, regs, sig); 603 } 604 605 static void set_signal_archinfo(unsigned long address, 606 unsigned long error_code) 607 { 608 struct task_struct *tsk = current; 609 610 /* 611 * To avoid leaking information about the kernel page 612 * table layout, pretend that user-mode accesses to 613 * kernel addresses are always protection faults. 614 * 615 * NB: This means that failed vsyscalls with vsyscall=none 616 * will have the PROT bit. This doesn't leak any 617 * information and does not appear to cause any problems. 618 */ 619 if (address >= TASK_SIZE_MAX) 620 error_code |= X86_PF_PROT; 621 622 tsk->thread.trap_nr = X86_TRAP_PF; 623 tsk->thread.error_code = error_code | X86_PF_USER; 624 tsk->thread.cr2 = address; 625 } 626 627 static noinline void 628 no_context(struct pt_regs *regs, unsigned long error_code, 629 unsigned long address, int signal, int si_code) 630 { 631 struct task_struct *tsk = current; 632 unsigned long flags; 633 int sig; 634 635 if (user_mode(regs)) { 636 /* 637 * This is an implicit supervisor-mode access from user 638 * mode. Bypass all the kernel-mode recovery code and just 639 * OOPS. 640 */ 641 goto oops; 642 } 643 644 /* Are we prepared to handle this kernel fault? */ 645 if (fixup_exception(regs, X86_TRAP_PF, error_code, address)) { 646 /* 647 * Any interrupt that takes a fault gets the fixup. This makes 648 * the below recursive fault logic only apply to a faults from 649 * task context. 650 */ 651 if (in_interrupt()) 652 return; 653 654 /* 655 * Per the above we're !in_interrupt(), aka. task context. 656 * 657 * In this case we need to make sure we're not recursively 658 * faulting through the emulate_vsyscall() logic. 659 */ 660 if (current->thread.sig_on_uaccess_err && signal) { 661 set_signal_archinfo(address, error_code); 662 663 /* XXX: hwpoison faults will set the wrong code. */ 664 force_sig_fault(signal, si_code, (void __user *)address); 665 } 666 667 /* 668 * Barring that, we can do the fixup and be happy. 669 */ 670 return; 671 } 672 673 #ifdef CONFIG_VMAP_STACK 674 /* 675 * Stack overflow? During boot, we can fault near the initial 676 * stack in the direct map, but that's not an overflow -- check 677 * that we're in vmalloc space to avoid this. 678 */ 679 if (is_vmalloc_addr((void *)address) && 680 (((unsigned long)tsk->stack - 1 - address < PAGE_SIZE) || 681 address - ((unsigned long)tsk->stack + THREAD_SIZE) < PAGE_SIZE)) { 682 unsigned long stack = __this_cpu_ist_top_va(DF) - sizeof(void *); 683 /* 684 * We're likely to be running with very little stack space 685 * left. It's plausible that we'd hit this condition but 686 * double-fault even before we get this far, in which case 687 * we're fine: the double-fault handler will deal with it. 688 * 689 * We don't want to make it all the way into the oops code 690 * and then double-fault, though, because we're likely to 691 * break the console driver and lose most of the stack dump. 692 */ 693 asm volatile ("movq %[stack], %%rsp\n\t" 694 "call handle_stack_overflow\n\t" 695 "1: jmp 1b" 696 : ASM_CALL_CONSTRAINT 697 : "D" ("kernel stack overflow (page fault)"), 698 "S" (regs), "d" (address), 699 [stack] "rm" (stack)); 700 unreachable(); 701 } 702 #endif 703 704 /* 705 * 32-bit: 706 * 707 * Valid to do another page fault here, because if this fault 708 * had been triggered by is_prefetch fixup_exception would have 709 * handled it. 710 * 711 * 64-bit: 712 * 713 * Hall of shame of CPU/BIOS bugs. 714 */ 715 if (is_prefetch(regs, error_code, address)) 716 return; 717 718 if (is_errata93(regs, address)) 719 return; 720 721 /* 722 * Buggy firmware could access regions which might page fault, try to 723 * recover from such faults. 724 */ 725 if (IS_ENABLED(CONFIG_EFI)) 726 efi_recover_from_page_fault(address); 727 728 oops: 729 /* 730 * Oops. The kernel tried to access some bad page. We'll have to 731 * terminate things with extreme prejudice: 732 */ 733 flags = oops_begin(); 734 735 show_fault_oops(regs, error_code, address); 736 737 if (task_stack_end_corrupted(tsk)) 738 printk(KERN_EMERG "Thread overran stack, or stack corrupted\n"); 739 740 sig = SIGKILL; 741 if (__die("Oops", regs, error_code)) 742 sig = 0; 743 744 /* Executive summary in case the body of the oops scrolled away */ 745 printk(KERN_DEFAULT "CR2: %016lx\n", address); 746 747 oops_end(flags, regs, sig); 748 } 749 750 /* 751 * Print out info about fatal segfaults, if the show_unhandled_signals 752 * sysctl is set: 753 */ 754 static inline void 755 show_signal_msg(struct pt_regs *regs, unsigned long error_code, 756 unsigned long address, struct task_struct *tsk) 757 { 758 const char *loglvl = task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG; 759 760 if (!unhandled_signal(tsk, SIGSEGV)) 761 return; 762 763 if (!printk_ratelimit()) 764 return; 765 766 printk("%s%s[%d]: segfault at %lx ip %px sp %px error %lx", 767 loglvl, tsk->comm, task_pid_nr(tsk), address, 768 (void *)regs->ip, (void *)regs->sp, error_code); 769 770 print_vma_addr(KERN_CONT " in ", regs->ip); 771 772 printk(KERN_CONT "\n"); 773 774 show_opcodes(regs, loglvl); 775 } 776 777 /* 778 * The (legacy) vsyscall page is the long page in the kernel portion 779 * of the address space that has user-accessible permissions. 780 */ 781 static bool is_vsyscall_vaddr(unsigned long vaddr) 782 { 783 return unlikely((vaddr & PAGE_MASK) == VSYSCALL_ADDR); 784 } 785 786 static void 787 __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code, 788 unsigned long address, u32 pkey, int si_code) 789 { 790 struct task_struct *tsk = current; 791 792 /* User mode accesses just cause a SIGSEGV */ 793 if (user_mode(regs) && (error_code & X86_PF_USER)) { 794 /* 795 * It's possible to have interrupts off here: 796 */ 797 local_irq_enable(); 798 799 /* 800 * Valid to do another page fault here because this one came 801 * from user space: 802 */ 803 if (is_prefetch(regs, error_code, address)) 804 return; 805 806 if (is_errata100(regs, address)) 807 return; 808 809 /* 810 * To avoid leaking information about the kernel page table 811 * layout, pretend that user-mode accesses to kernel addresses 812 * are always protection faults. 813 */ 814 if (address >= TASK_SIZE_MAX) 815 error_code |= X86_PF_PROT; 816 817 if (likely(show_unhandled_signals)) 818 show_signal_msg(regs, error_code, address, tsk); 819 820 set_signal_archinfo(address, error_code); 821 822 if (si_code == SEGV_PKUERR) 823 force_sig_pkuerr((void __user *)address, pkey); 824 825 force_sig_fault(SIGSEGV, si_code, (void __user *)address); 826 827 local_irq_disable(); 828 829 return; 830 } 831 832 if (is_f00f_bug(regs, address)) 833 return; 834 835 no_context(regs, error_code, address, SIGSEGV, si_code); 836 } 837 838 static noinline void 839 bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code, 840 unsigned long address) 841 { 842 __bad_area_nosemaphore(regs, error_code, address, 0, SEGV_MAPERR); 843 } 844 845 static void 846 __bad_area(struct pt_regs *regs, unsigned long error_code, 847 unsigned long address, u32 pkey, int si_code) 848 { 849 struct mm_struct *mm = current->mm; 850 /* 851 * Something tried to access memory that isn't in our memory map.. 852 * Fix it, but check if it's kernel or user first.. 853 */ 854 mmap_read_unlock(mm); 855 856 __bad_area_nosemaphore(regs, error_code, address, pkey, si_code); 857 } 858 859 static noinline void 860 bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address) 861 { 862 __bad_area(regs, error_code, address, 0, SEGV_MAPERR); 863 } 864 865 static inline bool bad_area_access_from_pkeys(unsigned long error_code, 866 struct vm_area_struct *vma) 867 { 868 /* This code is always called on the current mm */ 869 bool foreign = false; 870 871 if (!boot_cpu_has(X86_FEATURE_OSPKE)) 872 return false; 873 if (error_code & X86_PF_PK) 874 return true; 875 /* this checks permission keys on the VMA: */ 876 if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE), 877 (error_code & X86_PF_INSTR), foreign)) 878 return true; 879 return false; 880 } 881 882 static noinline void 883 bad_area_access_error(struct pt_regs *regs, unsigned long error_code, 884 unsigned long address, struct vm_area_struct *vma) 885 { 886 /* 887 * This OSPKE check is not strictly necessary at runtime. 888 * But, doing it this way allows compiler optimizations 889 * if pkeys are compiled out. 890 */ 891 if (bad_area_access_from_pkeys(error_code, vma)) { 892 /* 893 * A protection key fault means that the PKRU value did not allow 894 * access to some PTE. Userspace can figure out what PKRU was 895 * from the XSAVE state. This function captures the pkey from 896 * the vma and passes it to userspace so userspace can discover 897 * which protection key was set on the PTE. 898 * 899 * If we get here, we know that the hardware signaled a X86_PF_PK 900 * fault and that there was a VMA once we got in the fault 901 * handler. It does *not* guarantee that the VMA we find here 902 * was the one that we faulted on. 903 * 904 * 1. T1 : mprotect_key(foo, PAGE_SIZE, pkey=4); 905 * 2. T1 : set PKRU to deny access to pkey=4, touches page 906 * 3. T1 : faults... 907 * 4. T2: mprotect_key(foo, PAGE_SIZE, pkey=5); 908 * 5. T1 : enters fault handler, takes mmap_lock, etc... 909 * 6. T1 : reaches here, sees vma_pkey(vma)=5, when we really 910 * faulted on a pte with its pkey=4. 911 */ 912 u32 pkey = vma_pkey(vma); 913 914 __bad_area(regs, error_code, address, pkey, SEGV_PKUERR); 915 } else { 916 __bad_area(regs, error_code, address, 0, SEGV_ACCERR); 917 } 918 } 919 920 static void 921 do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address, 922 vm_fault_t fault) 923 { 924 /* Kernel mode? Handle exceptions or die: */ 925 if (!(error_code & X86_PF_USER)) { 926 no_context(regs, error_code, address, SIGBUS, BUS_ADRERR); 927 return; 928 } 929 930 /* User-space => ok to do another page fault: */ 931 if (is_prefetch(regs, error_code, address)) 932 return; 933 934 set_signal_archinfo(address, error_code); 935 936 #ifdef CONFIG_MEMORY_FAILURE 937 if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) { 938 struct task_struct *tsk = current; 939 unsigned lsb = 0; 940 941 pr_err( 942 "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n", 943 tsk->comm, tsk->pid, address); 944 if (fault & VM_FAULT_HWPOISON_LARGE) 945 lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault)); 946 if (fault & VM_FAULT_HWPOISON) 947 lsb = PAGE_SHIFT; 948 force_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb); 949 return; 950 } 951 #endif 952 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address); 953 } 954 955 static noinline void 956 mm_fault_error(struct pt_regs *regs, unsigned long error_code, 957 unsigned long address, vm_fault_t fault) 958 { 959 if (fatal_signal_pending(current) && !(error_code & X86_PF_USER)) { 960 no_context(regs, error_code, address, 0, 0); 961 return; 962 } 963 964 if (fault & VM_FAULT_OOM) { 965 /* Kernel mode? Handle exceptions or die: */ 966 if (!(error_code & X86_PF_USER)) { 967 no_context(regs, error_code, address, 968 SIGSEGV, SEGV_MAPERR); 969 return; 970 } 971 972 /* 973 * We ran out of memory, call the OOM killer, and return the 974 * userspace (which will retry the fault, or kill us if we got 975 * oom-killed): 976 */ 977 pagefault_out_of_memory(); 978 } else { 979 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON| 980 VM_FAULT_HWPOISON_LARGE)) 981 do_sigbus(regs, error_code, address, fault); 982 else if (fault & VM_FAULT_SIGSEGV) 983 bad_area_nosemaphore(regs, error_code, address); 984 else 985 BUG(); 986 } 987 } 988 989 static int spurious_kernel_fault_check(unsigned long error_code, pte_t *pte) 990 { 991 if ((error_code & X86_PF_WRITE) && !pte_write(*pte)) 992 return 0; 993 994 if ((error_code & X86_PF_INSTR) && !pte_exec(*pte)) 995 return 0; 996 997 return 1; 998 } 999 1000 /* 1001 * Handle a spurious fault caused by a stale TLB entry. 1002 * 1003 * This allows us to lazily refresh the TLB when increasing the 1004 * permissions of a kernel page (RO -> RW or NX -> X). Doing it 1005 * eagerly is very expensive since that implies doing a full 1006 * cross-processor TLB flush, even if no stale TLB entries exist 1007 * on other processors. 1008 * 1009 * Spurious faults may only occur if the TLB contains an entry with 1010 * fewer permission than the page table entry. Non-present (P = 0) 1011 * and reserved bit (R = 1) faults are never spurious. 1012 * 1013 * There are no security implications to leaving a stale TLB when 1014 * increasing the permissions on a page. 1015 * 1016 * Returns non-zero if a spurious fault was handled, zero otherwise. 1017 * 1018 * See Intel Developer's Manual Vol 3 Section 4.10.4.3, bullet 3 1019 * (Optional Invalidation). 1020 */ 1021 static noinline int 1022 spurious_kernel_fault(unsigned long error_code, unsigned long address) 1023 { 1024 pgd_t *pgd; 1025 p4d_t *p4d; 1026 pud_t *pud; 1027 pmd_t *pmd; 1028 pte_t *pte; 1029 int ret; 1030 1031 /* 1032 * Only writes to RO or instruction fetches from NX may cause 1033 * spurious faults. 1034 * 1035 * These could be from user or supervisor accesses but the TLB 1036 * is only lazily flushed after a kernel mapping protection 1037 * change, so user accesses are not expected to cause spurious 1038 * faults. 1039 */ 1040 if (error_code != (X86_PF_WRITE | X86_PF_PROT) && 1041 error_code != (X86_PF_INSTR | X86_PF_PROT)) 1042 return 0; 1043 1044 pgd = init_mm.pgd + pgd_index(address); 1045 if (!pgd_present(*pgd)) 1046 return 0; 1047 1048 p4d = p4d_offset(pgd, address); 1049 if (!p4d_present(*p4d)) 1050 return 0; 1051 1052 if (p4d_large(*p4d)) 1053 return spurious_kernel_fault_check(error_code, (pte_t *) p4d); 1054 1055 pud = pud_offset(p4d, address); 1056 if (!pud_present(*pud)) 1057 return 0; 1058 1059 if (pud_large(*pud)) 1060 return spurious_kernel_fault_check(error_code, (pte_t *) pud); 1061 1062 pmd = pmd_offset(pud, address); 1063 if (!pmd_present(*pmd)) 1064 return 0; 1065 1066 if (pmd_large(*pmd)) 1067 return spurious_kernel_fault_check(error_code, (pte_t *) pmd); 1068 1069 pte = pte_offset_kernel(pmd, address); 1070 if (!pte_present(*pte)) 1071 return 0; 1072 1073 ret = spurious_kernel_fault_check(error_code, pte); 1074 if (!ret) 1075 return 0; 1076 1077 /* 1078 * Make sure we have permissions in PMD. 1079 * If not, then there's a bug in the page tables: 1080 */ 1081 ret = spurious_kernel_fault_check(error_code, (pte_t *) pmd); 1082 WARN_ONCE(!ret, "PMD has incorrect permission bits\n"); 1083 1084 return ret; 1085 } 1086 NOKPROBE_SYMBOL(spurious_kernel_fault); 1087 1088 int show_unhandled_signals = 1; 1089 1090 static inline int 1091 access_error(unsigned long error_code, struct vm_area_struct *vma) 1092 { 1093 /* This is only called for the current mm, so: */ 1094 bool foreign = false; 1095 1096 /* 1097 * Read or write was blocked by protection keys. This is 1098 * always an unconditional error and can never result in 1099 * a follow-up action to resolve the fault, like a COW. 1100 */ 1101 if (error_code & X86_PF_PK) 1102 return 1; 1103 1104 /* 1105 * Make sure to check the VMA so that we do not perform 1106 * faults just to hit a X86_PF_PK as soon as we fill in a 1107 * page. 1108 */ 1109 if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE), 1110 (error_code & X86_PF_INSTR), foreign)) 1111 return 1; 1112 1113 if (error_code & X86_PF_WRITE) { 1114 /* write, present and write, not present: */ 1115 if (unlikely(!(vma->vm_flags & VM_WRITE))) 1116 return 1; 1117 return 0; 1118 } 1119 1120 /* read, present: */ 1121 if (unlikely(error_code & X86_PF_PROT)) 1122 return 1; 1123 1124 /* read, not present: */ 1125 if (unlikely(!vma_is_accessible(vma))) 1126 return 1; 1127 1128 return 0; 1129 } 1130 1131 static int fault_in_kernel_space(unsigned long address) 1132 { 1133 /* 1134 * On 64-bit systems, the vsyscall page is at an address above 1135 * TASK_SIZE_MAX, but is not considered part of the kernel 1136 * address space. 1137 */ 1138 if (IS_ENABLED(CONFIG_X86_64) && is_vsyscall_vaddr(address)) 1139 return false; 1140 1141 return address >= TASK_SIZE_MAX; 1142 } 1143 1144 /* 1145 * Called for all faults where 'address' is part of the kernel address 1146 * space. Might get called for faults that originate from *code* that 1147 * ran in userspace or the kernel. 1148 */ 1149 static void 1150 do_kern_addr_fault(struct pt_regs *regs, unsigned long hw_error_code, 1151 unsigned long address) 1152 { 1153 /* 1154 * Protection keys exceptions only happen on user pages. We 1155 * have no user pages in the kernel portion of the address 1156 * space, so do not expect them here. 1157 */ 1158 WARN_ON_ONCE(hw_error_code & X86_PF_PK); 1159 1160 #ifdef CONFIG_X86_32 1161 /* 1162 * We can fault-in kernel-space virtual memory on-demand. The 1163 * 'reference' page table is init_mm.pgd. 1164 * 1165 * NOTE! We MUST NOT take any locks for this case. We may 1166 * be in an interrupt or a critical region, and should 1167 * only copy the information from the master page table, 1168 * nothing more. 1169 * 1170 * Before doing this on-demand faulting, ensure that the 1171 * fault is not any of the following: 1172 * 1. A fault on a PTE with a reserved bit set. 1173 * 2. A fault caused by a user-mode access. (Do not demand- 1174 * fault kernel memory due to user-mode accesses). 1175 * 3. A fault caused by a page-level protection violation. 1176 * (A demand fault would be on a non-present page which 1177 * would have X86_PF_PROT==0). 1178 * 1179 * This is only needed to close a race condition on x86-32 in 1180 * the vmalloc mapping/unmapping code. See the comment above 1181 * vmalloc_fault() for details. On x86-64 the race does not 1182 * exist as the vmalloc mappings don't need to be synchronized 1183 * there. 1184 */ 1185 if (!(hw_error_code & (X86_PF_RSVD | X86_PF_USER | X86_PF_PROT))) { 1186 if (vmalloc_fault(address) >= 0) 1187 return; 1188 } 1189 #endif 1190 1191 /* Was the fault spurious, caused by lazy TLB invalidation? */ 1192 if (spurious_kernel_fault(hw_error_code, address)) 1193 return; 1194 1195 /* kprobes don't want to hook the spurious faults: */ 1196 if (kprobe_page_fault(regs, X86_TRAP_PF)) 1197 return; 1198 1199 /* 1200 * Note, despite being a "bad area", there are quite a few 1201 * acceptable reasons to get here, such as erratum fixups 1202 * and handling kernel code that can fault, like get_user(). 1203 * 1204 * Don't take the mm semaphore here. If we fixup a prefetch 1205 * fault we could otherwise deadlock: 1206 */ 1207 bad_area_nosemaphore(regs, hw_error_code, address); 1208 } 1209 NOKPROBE_SYMBOL(do_kern_addr_fault); 1210 1211 /* Handle faults in the user portion of the address space */ 1212 static inline 1213 void do_user_addr_fault(struct pt_regs *regs, 1214 unsigned long hw_error_code, 1215 unsigned long address) 1216 { 1217 struct vm_area_struct *vma; 1218 struct task_struct *tsk; 1219 struct mm_struct *mm; 1220 vm_fault_t fault; 1221 unsigned int flags = FAULT_FLAG_DEFAULT; 1222 1223 tsk = current; 1224 mm = tsk->mm; 1225 1226 /* kprobes don't want to hook the spurious faults: */ 1227 if (unlikely(kprobe_page_fault(regs, X86_TRAP_PF))) 1228 return; 1229 1230 /* 1231 * Reserved bits are never expected to be set on 1232 * entries in the user portion of the page tables. 1233 */ 1234 if (unlikely(hw_error_code & X86_PF_RSVD)) 1235 pgtable_bad(regs, hw_error_code, address); 1236 1237 /* 1238 * If SMAP is on, check for invalid kernel (supervisor) access to user 1239 * pages in the user address space. The odd case here is WRUSS, 1240 * which, according to the preliminary documentation, does not respect 1241 * SMAP and will have the USER bit set so, in all cases, SMAP 1242 * enforcement appears to be consistent with the USER bit. 1243 */ 1244 if (unlikely(cpu_feature_enabled(X86_FEATURE_SMAP) && 1245 !(hw_error_code & X86_PF_USER) && 1246 !(regs->flags & X86_EFLAGS_AC))) 1247 { 1248 bad_area_nosemaphore(regs, hw_error_code, address); 1249 return; 1250 } 1251 1252 /* 1253 * If we're in an interrupt, have no user context or are running 1254 * in a region with pagefaults disabled then we must not take the fault 1255 */ 1256 if (unlikely(faulthandler_disabled() || !mm)) { 1257 bad_area_nosemaphore(regs, hw_error_code, address); 1258 return; 1259 } 1260 1261 /* 1262 * It's safe to allow irq's after cr2 has been saved and the 1263 * vmalloc fault has been handled. 1264 * 1265 * User-mode registers count as a user access even for any 1266 * potential system fault or CPU buglet: 1267 */ 1268 if (user_mode(regs)) { 1269 local_irq_enable(); 1270 flags |= FAULT_FLAG_USER; 1271 } else { 1272 if (regs->flags & X86_EFLAGS_IF) 1273 local_irq_enable(); 1274 } 1275 1276 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 1277 1278 if (hw_error_code & X86_PF_WRITE) 1279 flags |= FAULT_FLAG_WRITE; 1280 if (hw_error_code & X86_PF_INSTR) 1281 flags |= FAULT_FLAG_INSTRUCTION; 1282 1283 #ifdef CONFIG_X86_64 1284 /* 1285 * Faults in the vsyscall page might need emulation. The 1286 * vsyscall page is at a high address (>PAGE_OFFSET), but is 1287 * considered to be part of the user address space. 1288 * 1289 * The vsyscall page does not have a "real" VMA, so do this 1290 * emulation before we go searching for VMAs. 1291 * 1292 * PKRU never rejects instruction fetches, so we don't need 1293 * to consider the PF_PK bit. 1294 */ 1295 if (is_vsyscall_vaddr(address)) { 1296 if (emulate_vsyscall(hw_error_code, regs, address)) 1297 return; 1298 } 1299 #endif 1300 1301 /* 1302 * Kernel-mode access to the user address space should only occur 1303 * on well-defined single instructions listed in the exception 1304 * tables. But, an erroneous kernel fault occurring outside one of 1305 * those areas which also holds mmap_lock might deadlock attempting 1306 * to validate the fault against the address space. 1307 * 1308 * Only do the expensive exception table search when we might be at 1309 * risk of a deadlock. This happens if we 1310 * 1. Failed to acquire mmap_lock, and 1311 * 2. The access did not originate in userspace. 1312 */ 1313 if (unlikely(!mmap_read_trylock(mm))) { 1314 if (!user_mode(regs) && !search_exception_tables(regs->ip)) { 1315 /* 1316 * Fault from code in kernel from 1317 * which we do not expect faults. 1318 */ 1319 bad_area_nosemaphore(regs, hw_error_code, address); 1320 return; 1321 } 1322 retry: 1323 mmap_read_lock(mm); 1324 } else { 1325 /* 1326 * The above down_read_trylock() might have succeeded in 1327 * which case we'll have missed the might_sleep() from 1328 * down_read(): 1329 */ 1330 might_sleep(); 1331 } 1332 1333 vma = find_vma(mm, address); 1334 if (unlikely(!vma)) { 1335 bad_area(regs, hw_error_code, address); 1336 return; 1337 } 1338 if (likely(vma->vm_start <= address)) 1339 goto good_area; 1340 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) { 1341 bad_area(regs, hw_error_code, address); 1342 return; 1343 } 1344 if (unlikely(expand_stack(vma, address))) { 1345 bad_area(regs, hw_error_code, address); 1346 return; 1347 } 1348 1349 /* 1350 * Ok, we have a good vm_area for this memory access, so 1351 * we can handle it.. 1352 */ 1353 good_area: 1354 if (unlikely(access_error(hw_error_code, vma))) { 1355 bad_area_access_error(regs, hw_error_code, address, vma); 1356 return; 1357 } 1358 1359 /* 1360 * If for any reason at all we couldn't handle the fault, 1361 * make sure we exit gracefully rather than endlessly redo 1362 * the fault. Since we never set FAULT_FLAG_RETRY_NOWAIT, if 1363 * we get VM_FAULT_RETRY back, the mmap_lock has been unlocked. 1364 * 1365 * Note that handle_userfault() may also release and reacquire mmap_lock 1366 * (and not return with VM_FAULT_RETRY), when returning to userland to 1367 * repeat the page fault later with a VM_FAULT_NOPAGE retval 1368 * (potentially after handling any pending signal during the return to 1369 * userland). The return to userland is identified whenever 1370 * FAULT_FLAG_USER|FAULT_FLAG_KILLABLE are both set in flags. 1371 */ 1372 fault = handle_mm_fault(vma, address, flags, regs); 1373 1374 /* Quick path to respond to signals */ 1375 if (fault_signal_pending(fault, regs)) { 1376 if (!user_mode(regs)) 1377 no_context(regs, hw_error_code, address, SIGBUS, 1378 BUS_ADRERR); 1379 return; 1380 } 1381 1382 /* 1383 * If we need to retry the mmap_lock has already been released, 1384 * and if there is a fatal signal pending there is no guarantee 1385 * that we made any progress. Handle this case first. 1386 */ 1387 if (unlikely((fault & VM_FAULT_RETRY) && 1388 (flags & FAULT_FLAG_ALLOW_RETRY))) { 1389 flags |= FAULT_FLAG_TRIED; 1390 goto retry; 1391 } 1392 1393 mmap_read_unlock(mm); 1394 if (unlikely(fault & VM_FAULT_ERROR)) { 1395 mm_fault_error(regs, hw_error_code, address, fault); 1396 return; 1397 } 1398 1399 check_v8086_mode(regs, address, tsk); 1400 } 1401 NOKPROBE_SYMBOL(do_user_addr_fault); 1402 1403 static __always_inline void 1404 trace_page_fault_entries(struct pt_regs *regs, unsigned long error_code, 1405 unsigned long address) 1406 { 1407 if (!trace_pagefault_enabled()) 1408 return; 1409 1410 if (user_mode(regs)) 1411 trace_page_fault_user(address, regs, error_code); 1412 else 1413 trace_page_fault_kernel(address, regs, error_code); 1414 } 1415 1416 static __always_inline void 1417 handle_page_fault(struct pt_regs *regs, unsigned long error_code, 1418 unsigned long address) 1419 { 1420 trace_page_fault_entries(regs, error_code, address); 1421 1422 if (unlikely(kmmio_fault(regs, address))) 1423 return; 1424 1425 /* Was the fault on kernel-controlled part of the address space? */ 1426 if (unlikely(fault_in_kernel_space(address))) { 1427 do_kern_addr_fault(regs, error_code, address); 1428 } else { 1429 do_user_addr_fault(regs, error_code, address); 1430 /* 1431 * User address page fault handling might have reenabled 1432 * interrupts. Fixing up all potential exit points of 1433 * do_user_addr_fault() and its leaf functions is just not 1434 * doable w/o creating an unholy mess or turning the code 1435 * upside down. 1436 */ 1437 local_irq_disable(); 1438 } 1439 } 1440 1441 DEFINE_IDTENTRY_RAW_ERRORCODE(exc_page_fault) 1442 { 1443 unsigned long address = read_cr2(); 1444 irqentry_state_t state; 1445 1446 prefetchw(¤t->mm->mmap_lock); 1447 1448 /* 1449 * KVM has two types of events that are, logically, interrupts, but 1450 * are unfortunately delivered using the #PF vector. These events are 1451 * "you just accessed valid memory, but the host doesn't have it right 1452 * now, so I'll put you to sleep if you continue" and "that memory 1453 * you tried to access earlier is available now." 1454 * 1455 * We are relying on the interrupted context being sane (valid RSP, 1456 * relevant locks not held, etc.), which is fine as long as the 1457 * interrupted context had IF=1. We are also relying on the KVM 1458 * async pf type field and CR2 being read consistently instead of 1459 * getting values from real and async page faults mixed up. 1460 * 1461 * Fingers crossed. 1462 * 1463 * The async #PF handling code takes care of idtentry handling 1464 * itself. 1465 */ 1466 if (kvm_handle_async_pf(regs, (u32)address)) 1467 return; 1468 1469 /* 1470 * Entry handling for valid #PF from kernel mode is slightly 1471 * different: RCU is already watching and rcu_irq_enter() must not 1472 * be invoked because a kernel fault on a user space address might 1473 * sleep. 1474 * 1475 * In case the fault hit a RCU idle region the conditional entry 1476 * code reenabled RCU to avoid subsequent wreckage which helps 1477 * debugability. 1478 */ 1479 state = irqentry_enter(regs); 1480 1481 instrumentation_begin(); 1482 handle_page_fault(regs, error_code, address); 1483 instrumentation_end(); 1484 1485 irqentry_exit(regs, state); 1486 } 1487