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/kdebug.h>		/* oops_begin/end, ...		*/
   8#include <linux/extable.h>		/* search_exception_tables	*/
   9#include <linux/bootmem.h>		/* max_low_pfn			*/
  10#include <linux/kprobes.h>		/* NOKPROBE_SYMBOL, ...		*/
  11#include <linux/mmiotrace.h>		/* kmmio_handler, ...		*/
  12#include <linux/perf_event.h>		/* perf_sw_event		*/
  13#include <linux/hugetlb.h>		/* hstate_index_to_shift	*/
  14#include <linux/prefetch.h>		/* prefetchw			*/
  15#include <linux/context_tracking.h>	/* exception_enter(), ...	*/
  16#include <linux/uaccess.h>		/* faulthandler_disabled()	*/
  17
  18#include <asm/cpufeature.h>		/* boot_cpu_has, ...		*/
  19#include <asm/traps.h>			/* dotraplinkage, ...		*/
  20#include <asm/pgalloc.h>		/* pgd_*(), ...			*/
  21#include <asm/kmemcheck.h>		/* kmemcheck_*(), ...		*/
  22#include <asm/fixmap.h>			/* VSYSCALL_ADDR		*/
  23#include <asm/vsyscall.h>		/* emulate_vsyscall		*/
  24#include <asm/vm86.h>			/* struct vm86			*/
  25#include <asm/mmu_context.h>		/* vma_pkey()			*/
  26
  27#define CREATE_TRACE_POINTS
  28#include <asm/trace/exceptions.h>
  29
  30/*
  31 * Page fault error code bits:
  32 *
  33 *   bit 0 ==	 0: no page found	1: protection fault
  34 *   bit 1 ==	 0: read access		1: write access
  35 *   bit 2 ==	 0: kernel-mode access	1: user-mode access
  36 *   bit 3 ==				1: use of reserved bit detected
  37 *   bit 4 ==				1: fault was an instruction fetch
  38 *   bit 5 ==				1: protection keys block access
  39 */
  40enum x86_pf_error_code {
  41
  42	PF_PROT		=		1 << 0,
  43	PF_WRITE	=		1 << 1,
  44	PF_USER		=		1 << 2,
  45	PF_RSVD		=		1 << 3,
  46	PF_INSTR	=		1 << 4,
  47	PF_PK		=		1 << 5,
  48};
  49
  50/*
  51 * Returns 0 if mmiotrace is disabled, or if the fault is not
  52 * handled by mmiotrace:
  53 */
  54static nokprobe_inline int
  55kmmio_fault(struct pt_regs *regs, unsigned long addr)
  56{
  57	if (unlikely(is_kmmio_active()))
  58		if (kmmio_handler(regs, addr) == 1)
  59			return -1;
  60	return 0;
  61}
  62
  63static nokprobe_inline int kprobes_fault(struct pt_regs *regs)
  64{
  65	int ret = 0;
  66
  67	/* kprobe_running() needs smp_processor_id() */
  68	if (kprobes_built_in() && !user_mode(regs)) {
  69		preempt_disable();
  70		if (kprobe_running() && kprobe_fault_handler(regs, 14))
  71			ret = 1;
  72		preempt_enable();
  73	}
  74
  75	return ret;
  76}
  77
  78/*
  79 * Prefetch quirks:
  80 *
  81 * 32-bit mode:
  82 *
  83 *   Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
  84 *   Check that here and ignore it.
  85 *
  86 * 64-bit mode:
  87 *
  88 *   Sometimes the CPU reports invalid exceptions on prefetch.
  89 *   Check that here and ignore it.
  90 *
  91 * Opcode checker based on code by Richard Brunner.
  92 */
  93static inline int
  94check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr,
  95		      unsigned char opcode, int *prefetch)
  96{
  97	unsigned char instr_hi = opcode & 0xf0;
  98	unsigned char instr_lo = opcode & 0x0f;
  99
 100	switch (instr_hi) {
 101	case 0x20:
 102	case 0x30:
 103		/*
 104		 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes.
 105		 * In X86_64 long mode, the CPU will signal invalid
 106		 * opcode if some of these prefixes are present so
 107		 * X86_64 will never get here anyway
 108		 */
 109		return ((instr_lo & 7) == 0x6);
 110#ifdef CONFIG_X86_64
 111	case 0x40:
 112		/*
 113		 * In AMD64 long mode 0x40..0x4F are valid REX prefixes
 114		 * Need to figure out under what instruction mode the
 115		 * instruction was issued. Could check the LDT for lm,
 116		 * but for now it's good enough to assume that long
 117		 * mode only uses well known segments or kernel.
 118		 */
 119		return (!user_mode(regs) || user_64bit_mode(regs));
 120#endif
 121	case 0x60:
 122		/* 0x64 thru 0x67 are valid prefixes in all modes. */
 123		return (instr_lo & 0xC) == 0x4;
 124	case 0xF0:
 125		/* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */
 126		return !instr_lo || (instr_lo>>1) == 1;
 127	case 0x00:
 128		/* Prefetch instruction is 0x0F0D or 0x0F18 */
 129		if (probe_kernel_address(instr, opcode))
 130			return 0;
 131
 132		*prefetch = (instr_lo == 0xF) &&
 133			(opcode == 0x0D || opcode == 0x18);
 134		return 0;
 135	default:
 136		return 0;
 137	}
 138}
 139
 140static int
 141is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
 142{
 143	unsigned char *max_instr;
 144	unsigned char *instr;
 145	int prefetch = 0;
 146
 147	/*
 148	 * If it was a exec (instruction fetch) fault on NX page, then
 149	 * do not ignore the fault:
 150	 */
 151	if (error_code & PF_INSTR)
 152		return 0;
 153
 154	instr = (void *)convert_ip_to_linear(current, regs);
 155	max_instr = instr + 15;
 156
 157	if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE_MAX)
 158		return 0;
 159
 160	while (instr < max_instr) {
 161		unsigned char opcode;
 162
 163		if (probe_kernel_address(instr, opcode))
 164			break;
 165
 166		instr++;
 167
 168		if (!check_prefetch_opcode(regs, instr, opcode, &prefetch))
 169			break;
 170	}
 171	return prefetch;
 172}
 173
 174/*
 175 * A protection key fault means that the PKRU value did not allow
 176 * access to some PTE.  Userspace can figure out what PKRU was
 177 * from the XSAVE state, and this function fills out a field in
 178 * siginfo so userspace can discover which protection key was set
 179 * on the PTE.
 180 *
 181 * If we get here, we know that the hardware signaled a PF_PK
 182 * fault and that there was a VMA once we got in the fault
 183 * handler.  It does *not* guarantee that the VMA we find here
 184 * was the one that we faulted on.
 185 *
 186 * 1. T1   : mprotect_key(foo, PAGE_SIZE, pkey=4);
 187 * 2. T1   : set PKRU to deny access to pkey=4, touches page
 188 * 3. T1   : faults...
 189 * 4.    T2: mprotect_key(foo, PAGE_SIZE, pkey=5);
 190 * 5. T1   : enters fault handler, takes mmap_sem, etc...
 191 * 6. T1   : reaches here, sees vma_pkey(vma)=5, when we really
 192 *	     faulted on a pte with its pkey=4.
 193 */
 194static void fill_sig_info_pkey(int si_code, siginfo_t *info,
 195		struct vm_area_struct *vma)
 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 (!vma) {
 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 = vma_pkey(vma);
 222}
 223
 224static void
 225force_sig_info_fault(int si_signo, int si_code, unsigned long address,
 226		     struct task_struct *tsk, struct vm_area_struct *vma,
 227		     int fault)
 228{
 229	unsigned lsb = 0;
 230	siginfo_t info;
 231
 232	info.si_signo	= si_signo;
 233	info.si_errno	= 0;
 234	info.si_code	= si_code;
 235	info.si_addr	= (void __user *)address;
 236	if (fault & VM_FAULT_HWPOISON_LARGE)
 237		lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault)); 
 238	if (fault & VM_FAULT_HWPOISON)
 239		lsb = PAGE_SHIFT;
 240	info.si_addr_lsb = lsb;
 241
 242	fill_sig_info_pkey(si_code, &info, vma);
 243
 244	force_sig_info(si_signo, &info, tsk);
 245}
 246
 247DEFINE_SPINLOCK(pgd_lock);
 248LIST_HEAD(pgd_list);
 249
 250#ifdef CONFIG_X86_32
 251static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
 252{
 253	unsigned index = pgd_index(address);
 254	pgd_t *pgd_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_pud.
 268	 */
 269	pud = pud_offset(pgd, address);
 270	pud_k = pud_offset(pgd_k, address);
 
 
 
 
 
 271	if (!pud_present(*pud_k))
 272		return NULL;
 273
 274	pmd = pmd_offset(pud, address);
 275	pmd_k = pmd_offset(pud_k, address);
 276	if (!pmd_present(*pmd_k))
 277		return NULL;
 278
 279	if (!pmd_present(*pmd))
 280		set_pmd(pmd, *pmd_k);
 281	else
 282		BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k));
 283
 284	return pmd_k;
 285}
 286
 287void vmalloc_sync_all(void)
 288{
 289	unsigned long address;
 290
 291	if (SHARED_KERNEL_PMD)
 292		return;
 293
 294	for (address = VMALLOC_START & PMD_MASK;
 295	     address >= TASK_SIZE_MAX && address < FIXADDR_TOP;
 296	     address += PMD_SIZE) {
 297		struct page *page;
 298
 299		spin_lock(&pgd_lock);
 300		list_for_each_entry(page, &pgd_list, lru) {
 301			spinlock_t *pgt_lock;
 302			pmd_t *ret;
 303
 304			/* the pgt_lock only for Xen */
 305			pgt_lock = &pgd_page_get_mm(page)->page_table_lock;
 306
 307			spin_lock(pgt_lock);
 308			ret = vmalloc_sync_one(page_address(page), address);
 309			spin_unlock(pgt_lock);
 310
 311			if (!ret)
 312				break;
 313		}
 314		spin_unlock(&pgd_lock);
 315	}
 316}
 317
 318/*
 319 * 32-bit:
 320 *
 321 *   Handle a fault on the vmalloc or module mapping area
 322 */
 323static noinline int vmalloc_fault(unsigned long address)
 324{
 325	unsigned long pgd_paddr;
 326	pmd_t *pmd_k;
 327	pte_t *pte_k;
 328
 329	/* Make sure we are in vmalloc area: */
 330	if (!(address >= VMALLOC_START && address < VMALLOC_END))
 331		return -1;
 332
 333	WARN_ON_ONCE(in_nmi());
 334
 335	/*
 336	 * Synchronize this task's top level page-table
 337	 * with the 'reference' page table.
 338	 *
 339	 * Do _not_ use "current" here. We might be inside
 340	 * an interrupt in the middle of a task switch..
 341	 */
 342	pgd_paddr = read_cr3();
 343	pmd_k = vmalloc_sync_one(__va(pgd_paddr), address);
 344	if (!pmd_k)
 345		return -1;
 346
 347	if (pmd_huge(*pmd_k))
 348		return 0;
 349
 350	pte_k = pte_offset_kernel(pmd_k, address);
 351	if (!pte_present(*pte_k))
 352		return -1;
 353
 354	return 0;
 355}
 356NOKPROBE_SYMBOL(vmalloc_fault);
 357
 358/*
 359 * Did it hit the DOS screen memory VA from vm86 mode?
 360 */
 361static inline void
 362check_v8086_mode(struct pt_regs *regs, unsigned long address,
 363		 struct task_struct *tsk)
 364{
 365#ifdef CONFIG_VM86
 366	unsigned long bit;
 367
 368	if (!v8086_mode(regs) || !tsk->thread.vm86)
 369		return;
 370
 371	bit = (address - 0xA0000) >> PAGE_SHIFT;
 372	if (bit < 32)
 373		tsk->thread.vm86->screen_bitmap |= 1 << bit;
 374#endif
 375}
 376
 377static bool low_pfn(unsigned long pfn)
 378{
 379	return pfn < max_low_pfn;
 380}
 381
 382static void dump_pagetable(unsigned long address)
 383{
 384	pgd_t *base = __va(read_cr3());
 385	pgd_t *pgd = &base[pgd_index(address)];
 
 
 386	pmd_t *pmd;
 387	pte_t *pte;
 388
 389#ifdef CONFIG_X86_PAE
 390	printk("*pdpt = %016Lx ", pgd_val(*pgd));
 391	if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd))
 392		goto out;
 
 
 
 393#endif
 394	pmd = pmd_offset(pud_offset(pgd, address), address);
 395	printk(KERN_CONT "*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd));
 
 
 
 396
 397	/*
 398	 * We must not directly access the pte in the highpte
 399	 * case if the page table is located in highmem.
 400	 * And let's rather not kmap-atomic the pte, just in case
 401	 * it's allocated already:
 402	 */
 403	if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_large(*pmd))
 404		goto out;
 405
 406	pte = pte_offset_kernel(pmd, address);
 407	printk("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte));
 408out:
 409	printk("\n");
 410}
 411
 412#else /* CONFIG_X86_64: */
 413
 414void vmalloc_sync_all(void)
 415{
 416	sync_global_pgds(VMALLOC_START & PGDIR_MASK, VMALLOC_END);
 417}
 418
 419/*
 420 * 64-bit:
 421 *
 422 *   Handle a fault on the vmalloc area
 423 */
 424static noinline int vmalloc_fault(unsigned long address)
 425{
 426	pgd_t *pgd, *pgd_ref;
 427	pud_t *pud, *pud_ref;
 428	pmd_t *pmd, *pmd_ref;
 429	pte_t *pte, *pte_ref;
 
 430
 431	/* Make sure we are in vmalloc area: */
 432	if (!(address >= VMALLOC_START && address < VMALLOC_END))
 433		return -1;
 434
 435	WARN_ON_ONCE(in_nmi());
 436
 437	/*
 438	 * Copy kernel mappings over when needed. This can also
 439	 * happen within a race in page table update. In the later
 440	 * case just flush:
 441	 */
 442	pgd = (pgd_t *)__va(read_cr3()) + pgd_index(address);
 443	pgd_ref = pgd_offset_k(address);
 444	if (pgd_none(*pgd_ref))
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 445		return -1;
 446
 447	if (pgd_none(*pgd)) {
 448		set_pgd(pgd, *pgd_ref);
 449		arch_flush_lazy_mmu_mode();
 450	} else {
 451		BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref));
 452	}
 453
 454	/*
 455	 * Below here mismatches are bugs because these lower tables
 456	 * are shared:
 457	 */
 458
 459	pud = pud_offset(pgd, address);
 460	pud_ref = pud_offset(pgd_ref, address);
 461	if (pud_none(*pud_ref))
 462		return -1;
 463
 464	if (pud_none(*pud) || pud_pfn(*pud) != pud_pfn(*pud_ref))
 465		BUG();
 466
 467	if (pud_huge(*pud))
 468		return 0;
 469
 470	pmd = pmd_offset(pud, address);
 471	pmd_ref = pmd_offset(pud_ref, address);
 472	if (pmd_none(*pmd_ref))
 473		return -1;
 474
 475	if (pmd_none(*pmd) || pmd_pfn(*pmd) != pmd_pfn(*pmd_ref))
 476		BUG();
 477
 478	if (pmd_huge(*pmd))
 479		return 0;
 480
 481	pte_ref = pte_offset_kernel(pmd_ref, address);
 482	if (!pte_present(*pte_ref))
 483		return -1;
 484
 485	pte = pte_offset_kernel(pmd, address);
 486
 487	/*
 488	 * Don't use pte_page here, because the mappings can point
 489	 * outside mem_map, and the NUMA hash lookup cannot handle
 490	 * that:
 491	 */
 492	if (!pte_present(*pte) || pte_pfn(*pte) != pte_pfn(*pte_ref))
 493		BUG();
 494
 495	return 0;
 496}
 497NOKPROBE_SYMBOL(vmalloc_fault);
 498
 499#ifdef CONFIG_CPU_SUP_AMD
 500static const char errata93_warning[] =
 501KERN_ERR 
 502"******* Your BIOS seems to not contain a fix for K8 errata #93\n"
 503"******* Working around it, but it may cause SEGVs or burn power.\n"
 504"******* Please consider a BIOS update.\n"
 505"******* Disabling USB legacy in the BIOS may also help.\n";
 506#endif
 507
 508/*
 509 * No vm86 mode in 64-bit mode:
 510 */
 511static inline void
 512check_v8086_mode(struct pt_regs *regs, unsigned long address,
 513		 struct task_struct *tsk)
 514{
 515}
 516
 517static int bad_address(void *p)
 518{
 519	unsigned long dummy;
 520
 521	return probe_kernel_address((unsigned long *)p, dummy);
 522}
 523
 524static void dump_pagetable(unsigned long address)
 525{
 526	pgd_t *base = __va(read_cr3() & PHYSICAL_PAGE_MASK);
 527	pgd_t *pgd = base + pgd_index(address);
 
 528	pud_t *pud;
 529	pmd_t *pmd;
 530	pte_t *pte;
 531
 532	if (bad_address(pgd))
 533		goto bad;
 534
 535	printk("PGD %lx ", pgd_val(*pgd));
 536
 537	if (!pgd_present(*pgd))
 538		goto out;
 539
 540	pud = pud_offset(pgd, address);
 
 
 
 
 
 
 
 
 541	if (bad_address(pud))
 542		goto bad;
 543
 544	printk("PUD %lx ", pud_val(*pud));
 545	if (!pud_present(*pud) || pud_large(*pud))
 546		goto out;
 547
 548	pmd = pmd_offset(pud, address);
 549	if (bad_address(pmd))
 550		goto bad;
 551
 552	printk("PMD %lx ", pmd_val(*pmd));
 553	if (!pmd_present(*pmd) || pmd_large(*pmd))
 554		goto out;
 555
 556	pte = pte_offset_kernel(pmd, address);
 557	if (bad_address(pte))
 558		goto bad;
 559
 560	printk("PTE %lx", pte_val(*pte));
 561out:
 562	printk("\n");
 563	return;
 564bad:
 565	printk("BAD\n");
 566}
 567
 568#endif /* CONFIG_X86_64 */
 569
 570/*
 571 * Workaround for K8 erratum #93 & buggy BIOS.
 572 *
 573 * BIOS SMM functions are required to use a specific workaround
 574 * to avoid corruption of the 64bit RIP register on C stepping K8.
 575 *
 576 * A lot of BIOS that didn't get tested properly miss this.
 577 *
 578 * The OS sees this as a page fault with the upper 32bits of RIP cleared.
 579 * Try to work around it here.
 580 *
 581 * Note we only handle faults in kernel here.
 582 * Does nothing on 32-bit.
 583 */
 584static int is_errata93(struct pt_regs *regs, unsigned long address)
 585{
 586#if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD)
 587	if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD
 588	    || boot_cpu_data.x86 != 0xf)
 589		return 0;
 590
 591	if (address != regs->ip)
 592		return 0;
 593
 594	if ((address >> 32) != 0)
 595		return 0;
 596
 597	address |= 0xffffffffUL << 32;
 598	if ((address >= (u64)_stext && address <= (u64)_etext) ||
 599	    (address >= MODULES_VADDR && address <= MODULES_END)) {
 600		printk_once(errata93_warning);
 601		regs->ip = address;
 602		return 1;
 603	}
 604#endif
 605	return 0;
 606}
 607
 608/*
 609 * Work around K8 erratum #100 K8 in compat mode occasionally jumps
 610 * to illegal addresses >4GB.
 611 *
 612 * We catch this in the page fault handler because these addresses
 613 * are not reachable. Just detect this case and return.  Any code
 614 * segment in LDT is compatibility mode.
 615 */
 616static int is_errata100(struct pt_regs *regs, unsigned long address)
 617{
 618#ifdef CONFIG_X86_64
 619	if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32))
 620		return 1;
 621#endif
 622	return 0;
 623}
 624
 625static int is_f00f_bug(struct pt_regs *regs, unsigned long address)
 626{
 627#ifdef CONFIG_X86_F00F_BUG
 628	unsigned long nr;
 629
 630	/*
 631	 * Pentium F0 0F C7 C8 bug workaround:
 632	 */
 633	if (boot_cpu_has_bug(X86_BUG_F00F)) {
 634		nr = (address - idt_descr.address) >> 3;
 635
 636		if (nr == 6) {
 637			do_invalid_op(regs, 0);
 638			return 1;
 639		}
 640	}
 641#endif
 642	return 0;
 643}
 644
 645static const char nx_warning[] = KERN_CRIT
 646"kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n";
 647static const char smep_warning[] = KERN_CRIT
 648"unable to execute userspace code (SMEP?) (uid: %d)\n";
 649
 650static void
 651show_fault_oops(struct pt_regs *regs, unsigned long error_code,
 652		unsigned long address)
 653{
 654	if (!oops_may_print())
 655		return;
 656
 657	if (error_code & PF_INSTR) {
 658		unsigned int level;
 659		pgd_t *pgd;
 660		pte_t *pte;
 661
 662		pgd = __va(read_cr3() & PHYSICAL_PAGE_MASK);
 663		pgd += pgd_index(address);
 664
 665		pte = lookup_address_in_pgd(pgd, address, &level);
 666
 667		if (pte && pte_present(*pte) && !pte_exec(*pte))
 668			printk(nx_warning, from_kuid(&init_user_ns, current_uid()));
 669		if (pte && pte_present(*pte) && pte_exec(*pte) &&
 670				(pgd_flags(*pgd) & _PAGE_USER) &&
 671				(__read_cr4() & X86_CR4_SMEP))
 672			printk(smep_warning, from_kuid(&init_user_ns, current_uid()));
 673	}
 674
 675	printk(KERN_ALERT "BUG: unable to handle kernel ");
 676	if (address < PAGE_SIZE)
 677		printk(KERN_CONT "NULL pointer dereference");
 678	else
 679		printk(KERN_CONT "paging request");
 680
 681	printk(KERN_CONT " at %p\n", (void *) address);
 682	printk(KERN_ALERT "IP: %pS\n", (void *)regs->ip);
 683
 684	dump_pagetable(address);
 685}
 686
 687static noinline void
 688pgtable_bad(struct pt_regs *regs, unsigned long error_code,
 689	    unsigned long address)
 690{
 691	struct task_struct *tsk;
 692	unsigned long flags;
 693	int sig;
 694
 695	flags = oops_begin();
 696	tsk = current;
 697	sig = SIGKILL;
 698
 699	printk(KERN_ALERT "%s: Corrupted page table at address %lx\n",
 700	       tsk->comm, address);
 701	dump_pagetable(address);
 702
 703	tsk->thread.cr2		= address;
 704	tsk->thread.trap_nr	= X86_TRAP_PF;
 705	tsk->thread.error_code	= error_code;
 706
 707	if (__die("Bad pagetable", regs, error_code))
 708		sig = 0;
 709
 710	oops_end(flags, regs, sig);
 711}
 712
 713static noinline void
 714no_context(struct pt_regs *regs, unsigned long error_code,
 715	   unsigned long address, int signal, int si_code)
 716{
 717	struct task_struct *tsk = current;
 718	unsigned long flags;
 719	int sig;
 720	/* No context means no VMA to pass down */
 721	struct vm_area_struct *vma = NULL;
 722
 723	/* Are we prepared to handle this kernel fault? */
 724	if (fixup_exception(regs, X86_TRAP_PF)) {
 725		/*
 726		 * Any interrupt that takes a fault gets the fixup. This makes
 727		 * the below recursive fault logic only apply to a faults from
 728		 * task context.
 729		 */
 730		if (in_interrupt())
 731			return;
 732
 733		/*
 734		 * Per the above we're !in_interrupt(), aka. task context.
 735		 *
 736		 * In this case we need to make sure we're not recursively
 737		 * faulting through the emulate_vsyscall() logic.
 738		 */
 739		if (current->thread.sig_on_uaccess_err && signal) {
 740			tsk->thread.trap_nr = X86_TRAP_PF;
 741			tsk->thread.error_code = error_code | PF_USER;
 742			tsk->thread.cr2 = address;
 743
 744			/* XXX: hwpoison faults will set the wrong code. */
 745			force_sig_info_fault(signal, si_code, address,
 746					     tsk, vma, 0);
 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		register void *__sp asm("rsp");
 765		unsigned long stack = this_cpu_read(orig_ist.ist[DOUBLEFAULT_STACK]) - sizeof(void *);
 766		/*
 767		 * We're likely to be running with very little stack space
 768		 * left.  It's plausible that we'd hit this condition but
 769		 * double-fault even before we get this far, in which case
 770		 * we're fine: the double-fault handler will deal with it.
 771		 *
 772		 * We don't want to make it all the way into the oops code
 773		 * and then double-fault, though, because we're likely to
 774		 * break the console driver and lose most of the stack dump.
 775		 */
 776		asm volatile ("movq %[stack], %%rsp\n\t"
 777			      "call handle_stack_overflow\n\t"
 778			      "1: jmp 1b"
 779			      : "+r" (__sp)
 780			      : "D" ("kernel stack overflow (page fault)"),
 781				"S" (regs), "d" (address),
 782				[stack] "rm" (stack));
 783		unreachable();
 784	}
 785#endif
 786
 787	/*
 788	 * 32-bit:
 789	 *
 790	 *   Valid to do another page fault here, because if this fault
 791	 *   had been triggered by is_prefetch fixup_exception would have
 792	 *   handled it.
 793	 *
 794	 * 64-bit:
 795	 *
 796	 *   Hall of shame of CPU/BIOS bugs.
 797	 */
 798	if (is_prefetch(regs, error_code, address))
 799		return;
 800
 801	if (is_errata93(regs, address))
 802		return;
 803
 804	/*
 805	 * Oops. The kernel tried to access some bad page. We'll have to
 806	 * terminate things with extreme prejudice:
 807	 */
 808	flags = oops_begin();
 809
 810	show_fault_oops(regs, error_code, address);
 811
 812	if (task_stack_end_corrupted(tsk))
 813		printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");
 814
 815	tsk->thread.cr2		= address;
 816	tsk->thread.trap_nr	= X86_TRAP_PF;
 817	tsk->thread.error_code	= error_code;
 818
 819	sig = SIGKILL;
 820	if (__die("Oops", regs, error_code))
 821		sig = 0;
 822
 823	/* Executive summary in case the body of the oops scrolled away */
 824	printk(KERN_DEFAULT "CR2: %016lx\n", address);
 825
 826	oops_end(flags, regs, sig);
 827}
 828
 829/*
 830 * Print out info about fatal segfaults, if the show_unhandled_signals
 831 * sysctl is set:
 832 */
 833static inline void
 834show_signal_msg(struct pt_regs *regs, unsigned long error_code,
 835		unsigned long address, struct task_struct *tsk)
 836{
 837	if (!unhandled_signal(tsk, SIGSEGV))
 838		return;
 839
 840	if (!printk_ratelimit())
 841		return;
 842
 843	printk("%s%s[%d]: segfault at %lx ip %p sp %p error %lx",
 844		task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
 845		tsk->comm, task_pid_nr(tsk), address,
 846		(void *)regs->ip, (void *)regs->sp, error_code);
 847
 848	print_vma_addr(KERN_CONT " in ", regs->ip);
 849
 850	printk(KERN_CONT "\n");
 851}
 852
 853static void
 854__bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
 855		       unsigned long address, struct vm_area_struct *vma,
 856		       int si_code)
 857{
 858	struct task_struct *tsk = current;
 859
 860	/* User mode accesses just cause a SIGSEGV */
 861	if (error_code & PF_USER) {
 862		/*
 863		 * It's possible to have interrupts off here:
 864		 */
 865		local_irq_enable();
 866
 867		/*
 868		 * Valid to do another page fault here because this one came
 869		 * from user space:
 870		 */
 871		if (is_prefetch(regs, error_code, address))
 872			return;
 873
 874		if (is_errata100(regs, address))
 875			return;
 876
 877#ifdef CONFIG_X86_64
 878		/*
 879		 * Instruction fetch faults in the vsyscall page might need
 880		 * emulation.
 881		 */
 882		if (unlikely((error_code & PF_INSTR) &&
 883			     ((address & ~0xfff) == VSYSCALL_ADDR))) {
 884			if (emulate_vsyscall(regs, address))
 885				return;
 886		}
 887#endif
 888
 889		/*
 890		 * To avoid leaking information about the kernel page table
 891		 * layout, pretend that user-mode accesses to kernel addresses
 892		 * are always protection faults.
 893		 */
 894		if (address >= TASK_SIZE_MAX)
 895			error_code |= PF_PROT;
 896
 897		if (likely(show_unhandled_signals))
 898			show_signal_msg(regs, error_code, address, tsk);
 899
 900		tsk->thread.cr2		= address;
 901		tsk->thread.error_code	= error_code;
 902		tsk->thread.trap_nr	= X86_TRAP_PF;
 903
 904		force_sig_info_fault(SIGSEGV, si_code, address, tsk, vma, 0);
 905
 906		return;
 907	}
 908
 909	if (is_f00f_bug(regs, address))
 910		return;
 911
 912	no_context(regs, error_code, address, SIGSEGV, si_code);
 913}
 914
 915static noinline void
 916bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
 917		     unsigned long address, struct vm_area_struct *vma)
 918{
 919	__bad_area_nosemaphore(regs, error_code, address, vma, SEGV_MAPERR);
 920}
 921
 922static void
 923__bad_area(struct pt_regs *regs, unsigned long error_code,
 924	   unsigned long address,  struct vm_area_struct *vma, int si_code)
 925{
 926	struct mm_struct *mm = current->mm;
 
 
 
 
 927
 928	/*
 929	 * Something tried to access memory that isn't in our memory map..
 930	 * Fix it, but check if it's kernel or user first..
 931	 */
 932	up_read(&mm->mmap_sem);
 933
 934	__bad_area_nosemaphore(regs, error_code, address, vma, si_code);
 
 935}
 936
 937static noinline void
 938bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address)
 939{
 940	__bad_area(regs, error_code, address, NULL, SEGV_MAPERR);
 941}
 942
 943static inline bool bad_area_access_from_pkeys(unsigned long error_code,
 944		struct vm_area_struct *vma)
 945{
 946	/* This code is always called on the current mm */
 947	bool foreign = false;
 948
 949	if (!boot_cpu_has(X86_FEATURE_OSPKE))
 950		return false;
 951	if (error_code & PF_PK)
 952		return true;
 953	/* this checks permission keys on the VMA: */
 954	if (!arch_vma_access_permitted(vma, (error_code & PF_WRITE),
 955				(error_code & PF_INSTR), foreign))
 956		return true;
 957	return false;
 958}
 959
 960static noinline void
 961bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
 962		      unsigned long address, struct vm_area_struct *vma)
 963{
 964	/*
 965	 * This OSPKE check is not strictly necessary at runtime.
 966	 * But, doing it this way allows compiler optimizations
 967	 * if pkeys are compiled out.
 968	 */
 969	if (bad_area_access_from_pkeys(error_code, vma))
 970		__bad_area(regs, error_code, address, vma, SEGV_PKUERR);
 971	else
 972		__bad_area(regs, error_code, address, vma, SEGV_ACCERR);
 973}
 974
 975static void
 976do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
 977	  struct vm_area_struct *vma, unsigned int fault)
 978{
 979	struct task_struct *tsk = current;
 980	int code = BUS_ADRERR;
 981
 982	/* Kernel mode? Handle exceptions or die: */
 983	if (!(error_code & PF_USER)) {
 984		no_context(regs, error_code, address, SIGBUS, BUS_ADRERR);
 985		return;
 986	}
 987
 988	/* User-space => ok to do another page fault: */
 989	if (is_prefetch(regs, error_code, address))
 990		return;
 991
 992	tsk->thread.cr2		= address;
 993	tsk->thread.error_code	= error_code;
 994	tsk->thread.trap_nr	= X86_TRAP_PF;
 995
 996#ifdef CONFIG_MEMORY_FAILURE
 997	if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
 998		printk(KERN_ERR
 999	"MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
1000			tsk->comm, tsk->pid, address);
1001		code = BUS_MCEERR_AR;
1002	}
1003#endif
1004	force_sig_info_fault(SIGBUS, code, address, tsk, vma, fault);
1005}
1006
1007static noinline void
1008mm_fault_error(struct pt_regs *regs, unsigned long error_code,
1009	       unsigned long address, struct vm_area_struct *vma,
1010	       unsigned int fault)
1011{
1012	if (fatal_signal_pending(current) && !(error_code & PF_USER)) {
1013		no_context(regs, error_code, address, 0, 0);
1014		return;
1015	}
1016
1017	if (fault & VM_FAULT_OOM) {
1018		/* Kernel mode? Handle exceptions or die: */
1019		if (!(error_code & PF_USER)) {
1020			no_context(regs, error_code, address,
1021				   SIGSEGV, SEGV_MAPERR);
1022			return;
1023		}
1024
1025		/*
1026		 * We ran out of memory, call the OOM killer, and return the
1027		 * userspace (which will retry the fault, or kill us if we got
1028		 * oom-killed):
1029		 */
1030		pagefault_out_of_memory();
1031	} else {
1032		if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
1033			     VM_FAULT_HWPOISON_LARGE))
1034			do_sigbus(regs, error_code, address, vma, fault);
1035		else if (fault & VM_FAULT_SIGSEGV)
1036			bad_area_nosemaphore(regs, error_code, address, vma);
1037		else
1038			BUG();
1039	}
1040}
1041
1042static int spurious_fault_check(unsigned long error_code, pte_t *pte)
1043{
1044	if ((error_code & PF_WRITE) && !pte_write(*pte))
1045		return 0;
1046
1047	if ((error_code & PF_INSTR) && !pte_exec(*pte))
1048		return 0;
1049	/*
1050	 * Note: We do not do lazy flushing on protection key
1051	 * changes, so no spurious fault will ever set PF_PK.
1052	 */
1053	if ((error_code & PF_PK))
1054		return 1;
1055
1056	return 1;
1057}
1058
1059/*
1060 * Handle a spurious fault caused by a stale TLB entry.
1061 *
1062 * This allows us to lazily refresh the TLB when increasing the
1063 * permissions of a kernel page (RO -> RW or NX -> X).  Doing it
1064 * eagerly is very expensive since that implies doing a full
1065 * cross-processor TLB flush, even if no stale TLB entries exist
1066 * on other processors.
1067 *
1068 * Spurious faults may only occur if the TLB contains an entry with
1069 * fewer permission than the page table entry.  Non-present (P = 0)
1070 * and reserved bit (R = 1) faults are never spurious.
1071 *
1072 * There are no security implications to leaving a stale TLB when
1073 * increasing the permissions on a page.
1074 *
1075 * Returns non-zero if a spurious fault was handled, zero otherwise.
1076 *
1077 * See Intel Developer's Manual Vol 3 Section 4.10.4.3, bullet 3
1078 * (Optional Invalidation).
1079 */
1080static noinline int
1081spurious_fault(unsigned long error_code, unsigned long address)
1082{
1083	pgd_t *pgd;
 
1084	pud_t *pud;
1085	pmd_t *pmd;
1086	pte_t *pte;
1087	int ret;
1088
1089	/*
1090	 * Only writes to RO or instruction fetches from NX may cause
1091	 * spurious faults.
1092	 *
1093	 * These could be from user or supervisor accesses but the TLB
1094	 * is only lazily flushed after a kernel mapping protection
1095	 * change, so user accesses are not expected to cause spurious
1096	 * faults.
1097	 */
1098	if (error_code != (PF_WRITE | PF_PROT)
1099	    && error_code != (PF_INSTR | PF_PROT))
1100		return 0;
1101
1102	pgd = init_mm.pgd + pgd_index(address);
1103	if (!pgd_present(*pgd))
1104		return 0;
1105
1106	pud = pud_offset(pgd, address);
 
 
 
 
 
 
 
1107	if (!pud_present(*pud))
1108		return 0;
1109
1110	if (pud_large(*pud))
1111		return spurious_fault_check(error_code, (pte_t *) pud);
1112
1113	pmd = pmd_offset(pud, address);
1114	if (!pmd_present(*pmd))
1115		return 0;
1116
1117	if (pmd_large(*pmd))
1118		return spurious_fault_check(error_code, (pte_t *) pmd);
1119
1120	pte = pte_offset_kernel(pmd, address);
1121	if (!pte_present(*pte))
1122		return 0;
1123
1124	ret = spurious_fault_check(error_code, pte);
1125	if (!ret)
1126		return 0;
1127
1128	/*
1129	 * Make sure we have permissions in PMD.
1130	 * If not, then there's a bug in the page tables:
1131	 */
1132	ret = spurious_fault_check(error_code, (pte_t *) pmd);
1133	WARN_ONCE(!ret, "PMD has incorrect permission bits\n");
1134
1135	return ret;
1136}
1137NOKPROBE_SYMBOL(spurious_fault);
1138
1139int show_unhandled_signals = 1;
1140
1141static inline int
1142access_error(unsigned long error_code, struct vm_area_struct *vma)
1143{
1144	/* This is only called for the current mm, so: */
1145	bool foreign = false;
1146
1147	/*
1148	 * Read or write was blocked by protection keys.  This is
1149	 * always an unconditional error and can never result in
1150	 * a follow-up action to resolve the fault, like a COW.
1151	 */
1152	if (error_code & PF_PK)
1153		return 1;
1154
1155	/*
1156	 * Make sure to check the VMA so that we do not perform
1157	 * faults just to hit a PF_PK as soon as we fill in a
1158	 * page.
1159	 */
1160	if (!arch_vma_access_permitted(vma, (error_code & PF_WRITE),
1161				(error_code & PF_INSTR), foreign))
1162		return 1;
1163
1164	if (error_code & PF_WRITE) {
1165		/* write, present and write, not present: */
1166		if (unlikely(!(vma->vm_flags & VM_WRITE)))
1167			return 1;
1168		return 0;
1169	}
1170
1171	/* read, present: */
1172	if (unlikely(error_code & PF_PROT))
1173		return 1;
1174
1175	/* read, not present: */
1176	if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))))
1177		return 1;
1178
1179	return 0;
1180}
1181
1182static int fault_in_kernel_space(unsigned long address)
1183{
1184	return address >= TASK_SIZE_MAX;
1185}
1186
1187static inline bool smap_violation(int error_code, struct pt_regs *regs)
1188{
1189	if (!IS_ENABLED(CONFIG_X86_SMAP))
1190		return false;
1191
1192	if (!static_cpu_has(X86_FEATURE_SMAP))
1193		return false;
1194
1195	if (error_code & PF_USER)
1196		return false;
1197
1198	if (!user_mode(regs) && (regs->flags & X86_EFLAGS_AC))
1199		return false;
1200
1201	return true;
1202}
1203
1204/*
1205 * This routine handles page faults.  It determines the address,
1206 * and the problem, and then passes it off to one of the appropriate
1207 * routines.
1208 *
1209 * This function must have noinline because both callers
1210 * {,trace_}do_page_fault() have notrace on. Having this an actual function
1211 * guarantees there's a function trace entry.
1212 */
1213static noinline void
1214__do_page_fault(struct pt_regs *regs, unsigned long error_code,
1215		unsigned long address)
1216{
1217	struct vm_area_struct *vma;
1218	struct task_struct *tsk;
1219	struct mm_struct *mm;
1220	int fault, major = 0;
1221	unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
 
1222
1223	tsk = current;
1224	mm = tsk->mm;
1225
1226	/*
1227	 * Detect and handle instructions that would cause a page fault for
1228	 * both a tracked kernel page and a userspace page.
1229	 */
1230	if (kmemcheck_active(regs))
1231		kmemcheck_hide(regs);
1232	prefetchw(&mm->mmap_sem);
1233
1234	if (unlikely(kmmio_fault(regs, address)))
1235		return;
1236
1237	/*
1238	 * We fault-in kernel-space virtual memory on-demand. The
1239	 * 'reference' page table is init_mm.pgd.
1240	 *
1241	 * NOTE! We MUST NOT take any locks for this case. We may
1242	 * be in an interrupt or a critical region, and should
1243	 * only copy the information from the master page table,
1244	 * nothing more.
1245	 *
1246	 * This verifies that the fault happens in kernel space
1247	 * (error_code & 4) == 0, and that the fault was not a
1248	 * protection error (error_code & 9) == 0.
1249	 */
1250	if (unlikely(fault_in_kernel_space(address))) {
1251		if (!(error_code & (PF_RSVD | PF_USER | PF_PROT))) {
1252			if (vmalloc_fault(address) >= 0)
1253				return;
1254
1255			if (kmemcheck_fault(regs, address, error_code))
1256				return;
1257		}
1258
1259		/* Can handle a stale RO->RW TLB: */
1260		if (spurious_fault(error_code, address))
1261			return;
1262
1263		/* kprobes don't want to hook the spurious faults: */
1264		if (kprobes_fault(regs))
1265			return;
1266		/*
1267		 * Don't take the mm semaphore here. If we fixup a prefetch
1268		 * fault we could otherwise deadlock:
1269		 */
1270		bad_area_nosemaphore(regs, error_code, address, NULL);
1271
1272		return;
1273	}
1274
1275	/* kprobes don't want to hook the spurious faults: */
1276	if (unlikely(kprobes_fault(regs)))
1277		return;
1278
1279	if (unlikely(error_code & PF_RSVD))
1280		pgtable_bad(regs, error_code, address);
1281
1282	if (unlikely(smap_violation(error_code, regs))) {
1283		bad_area_nosemaphore(regs, error_code, address, NULL);
1284		return;
1285	}
1286
1287	/*
1288	 * If we're in an interrupt, have no user context or are running
1289	 * in a region with pagefaults disabled then we must not take the fault
1290	 */
1291	if (unlikely(faulthandler_disabled() || !mm)) {
1292		bad_area_nosemaphore(regs, error_code, address, NULL);
1293		return;
1294	}
1295
1296	/*
1297	 * It's safe to allow irq's after cr2 has been saved and the
1298	 * vmalloc fault has been handled.
1299	 *
1300	 * User-mode registers count as a user access even for any
1301	 * potential system fault or CPU buglet:
1302	 */
1303	if (user_mode(regs)) {
1304		local_irq_enable();
1305		error_code |= PF_USER;
1306		flags |= FAULT_FLAG_USER;
1307	} else {
1308		if (regs->flags & X86_EFLAGS_IF)
1309			local_irq_enable();
1310	}
1311
1312	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
1313
1314	if (error_code & PF_WRITE)
1315		flags |= FAULT_FLAG_WRITE;
1316	if (error_code & PF_INSTR)
1317		flags |= FAULT_FLAG_INSTRUCTION;
1318
1319	/*
1320	 * When running in the kernel we expect faults to occur only to
1321	 * addresses in user space.  All other faults represent errors in
1322	 * the kernel and should generate an OOPS.  Unfortunately, in the
1323	 * case of an erroneous fault occurring in a code path which already
1324	 * holds mmap_sem we will deadlock attempting to validate the fault
1325	 * against the address space.  Luckily the kernel only validly
1326	 * references user space from well defined areas of code, which are
1327	 * listed in the exceptions table.
1328	 *
1329	 * As the vast majority of faults will be valid we will only perform
1330	 * the source reference check when there is a possibility of a
1331	 * deadlock. Attempt to lock the address space, if we cannot we then
1332	 * validate the source. If this is invalid we can skip the address
1333	 * space check, thus avoiding the deadlock:
1334	 */
1335	if (unlikely(!down_read_trylock(&mm->mmap_sem))) {
1336		if ((error_code & PF_USER) == 0 &&
1337		    !search_exception_tables(regs->ip)) {
1338			bad_area_nosemaphore(regs, error_code, address, NULL);
1339			return;
1340		}
1341retry:
1342		down_read(&mm->mmap_sem);
1343	} else {
1344		/*
1345		 * The above down_read_trylock() might have succeeded in
1346		 * which case we'll have missed the might_sleep() from
1347		 * down_read():
1348		 */
1349		might_sleep();
1350	}
1351
1352	vma = find_vma(mm, address);
1353	if (unlikely(!vma)) {
1354		bad_area(regs, error_code, address);
1355		return;
1356	}
1357	if (likely(vma->vm_start <= address))
1358		goto good_area;
1359	if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
1360		bad_area(regs, error_code, address);
1361		return;
1362	}
1363	if (error_code & PF_USER) {
1364		/*
1365		 * Accessing the stack below %sp is always a bug.
1366		 * The large cushion allows instructions like enter
1367		 * and pusha to work. ("enter $65535, $31" pushes
1368		 * 32 pointers and then decrements %sp by 65535.)
1369		 */
1370		if (unlikely(address + 65536 + 32 * sizeof(unsigned long) < regs->sp)) {
1371			bad_area(regs, error_code, address);
1372			return;
1373		}
1374	}
1375	if (unlikely(expand_stack(vma, address))) {
1376		bad_area(regs, error_code, address);
1377		return;
1378	}
1379
1380	/*
1381	 * Ok, we have a good vm_area for this memory access, so
1382	 * we can handle it..
1383	 */
1384good_area:
1385	if (unlikely(access_error(error_code, vma))) {
1386		bad_area_access_error(regs, error_code, address, vma);
1387		return;
1388	}
1389
1390	/*
1391	 * If for any reason at all we couldn't handle the fault,
1392	 * make sure we exit gracefully rather than endlessly redo
1393	 * the fault.  Since we never set FAULT_FLAG_RETRY_NOWAIT, if
1394	 * we get VM_FAULT_RETRY back, the mmap_sem has been unlocked.
 
 
 
 
 
 
 
 
 
1395	 */
 
1396	fault = handle_mm_fault(vma, address, flags);
1397	major |= fault & VM_FAULT_MAJOR;
1398
1399	/*
1400	 * If we need to retry the mmap_sem has already been released,
1401	 * and if there is a fatal signal pending there is no guarantee
1402	 * that we made any progress. Handle this case first.
1403	 */
1404	if (unlikely(fault & VM_FAULT_RETRY)) {
1405		/* Retry at most once */
1406		if (flags & FAULT_FLAG_ALLOW_RETRY) {
1407			flags &= ~FAULT_FLAG_ALLOW_RETRY;
1408			flags |= FAULT_FLAG_TRIED;
1409			if (!fatal_signal_pending(tsk))
1410				goto retry;
1411		}
1412
1413		/* User mode? Just return to handle the fatal exception */
1414		if (flags & FAULT_FLAG_USER)
1415			return;
1416
1417		/* Not returning to user mode? Handle exceptions or die: */
1418		no_context(regs, error_code, address, SIGBUS, BUS_ADRERR);
1419		return;
1420	}
1421
1422	up_read(&mm->mmap_sem);
1423	if (unlikely(fault & VM_FAULT_ERROR)) {
1424		mm_fault_error(regs, error_code, address, vma, fault);
1425		return;
1426	}
1427
1428	/*
1429	 * Major/minor page fault accounting. If any of the events
1430	 * returned VM_FAULT_MAJOR, we account it as a major fault.
1431	 */
1432	if (major) {
1433		tsk->maj_flt++;
1434		perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address);
1435	} else {
1436		tsk->min_flt++;
1437		perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address);
1438	}
1439
1440	check_v8086_mode(regs, address, tsk);
1441}
1442NOKPROBE_SYMBOL(__do_page_fault);
1443
1444dotraplinkage void notrace
1445do_page_fault(struct pt_regs *regs, unsigned long error_code)
1446{
1447	unsigned long address = read_cr2(); /* Get the faulting address */
1448	enum ctx_state prev_state;
1449
1450	/*
1451	 * We must have this function tagged with __kprobes, notrace and call
1452	 * read_cr2() before calling anything else. To avoid calling any kind
1453	 * of tracing machinery before we've observed the CR2 value.
1454	 *
1455	 * exception_{enter,exit}() contain all sorts of tracepoints.
1456	 */
1457
1458	prev_state = exception_enter();
1459	__do_page_fault(regs, error_code, address);
1460	exception_exit(prev_state);
1461}
1462NOKPROBE_SYMBOL(do_page_fault);
1463
1464#ifdef CONFIG_TRACING
1465static nokprobe_inline void
1466trace_page_fault_entries(unsigned long address, struct pt_regs *regs,
1467			 unsigned long error_code)
1468{
1469	if (user_mode(regs))
1470		trace_page_fault_user(address, regs, error_code);
1471	else
1472		trace_page_fault_kernel(address, regs, error_code);
1473}
1474
 
 
 
 
 
 
 
1475dotraplinkage void notrace
1476trace_do_page_fault(struct pt_regs *regs, unsigned long error_code)
1477{
1478	/*
1479	 * The exception_enter and tracepoint processing could
1480	 * trigger another page faults (user space callchain
1481	 * reading) and destroy the original cr2 value, so read
1482	 * the faulting address now.
1483	 */
1484	unsigned long address = read_cr2();
1485	enum ctx_state prev_state;
1486
1487	prev_state = exception_enter();
1488	trace_page_fault_entries(address, regs, error_code);
 
 
1489	__do_page_fault(regs, error_code, address);
1490	exception_exit(prev_state);
1491}
1492NOKPROBE_SYMBOL(trace_do_page_fault);
1493#endif /* CONFIG_TRACING */