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/magic.h>		/* STACK_END_MAGIC		*/
   7#include <linux/sched.h>		/* test_thread_flag(), ...	*/
 
   8#include <linux/kdebug.h>		/* oops_begin/end, ...		*/
   9#include <linux/module.h>		/* search_exception_table	*/
  10#include <linux/bootmem.h>		/* max_low_pfn			*/
  11#include <linux/kprobes.h>		/* __kprobes, ...		*/
 
  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
 
  17#include <asm/traps.h>			/* dotraplinkage, ...		*/
  18#include <asm/pgalloc.h>		/* pgd_*(), ...			*/
  19#include <asm/kmemcheck.h>		/* kmemcheck_*(), ...		*/
  20#include <asm/vsyscall.h>
 
 
 
 
 
 
 
 
 
 
  21
  22/*
  23 * Page fault error code bits:
  24 *
  25 *   bit 0 ==	 0: no page found	1: protection fault
  26 *   bit 1 ==	 0: read access		1: write access
  27 *   bit 2 ==	 0: kernel-mode access	1: user-mode access
  28 *   bit 3 ==				1: use of reserved bit detected
  29 *   bit 4 ==				1: fault was an instruction fetch
  30 */
  31enum x86_pf_error_code {
  32
  33	PF_PROT		=		1 << 0,
  34	PF_WRITE	=		1 << 1,
  35	PF_USER		=		1 << 2,
  36	PF_RSVD		=		1 << 3,
  37	PF_INSTR	=		1 << 4,
  38};
  39
  40/*
  41 * Returns 0 if mmiotrace is disabled, or if the fault is not
  42 * handled by mmiotrace:
  43 */
  44static inline int __kprobes
  45kmmio_fault(struct pt_regs *regs, unsigned long addr)
  46{
  47	if (unlikely(is_kmmio_active()))
  48		if (kmmio_handler(regs, addr) == 1)
  49			return -1;
  50	return 0;
  51}
  52
  53static inline int __kprobes notify_page_fault(struct pt_regs *regs)
  54{
  55	int ret = 0;
  56
  57	/* kprobe_running() needs smp_processor_id() */
  58	if (kprobes_built_in() && !user_mode_vm(regs)) {
  59		preempt_disable();
  60		if (kprobe_running() && kprobe_fault_handler(regs, 14))
  61			ret = 1;
  62		preempt_enable();
  63	}
  64
  65	return ret;
  66}
  67
  68/*
  69 * Prefetch quirks:
  70 *
  71 * 32-bit mode:
  72 *
  73 *   Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
  74 *   Check that here and ignore it.
  75 *
  76 * 64-bit mode:
  77 *
  78 *   Sometimes the CPU reports invalid exceptions on prefetch.
  79 *   Check that here and ignore it.
  80 *
  81 * Opcode checker based on code by Richard Brunner.
  82 */
  83static inline int
  84check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr,
  85		      unsigned char opcode, int *prefetch)
  86{
  87	unsigned char instr_hi = opcode & 0xf0;
  88	unsigned char instr_lo = opcode & 0x0f;
  89
  90	switch (instr_hi) {
  91	case 0x20:
  92	case 0x30:
  93		/*
  94		 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes.
  95		 * In X86_64 long mode, the CPU will signal invalid
  96		 * opcode if some of these prefixes are present so
  97		 * X86_64 will never get here anyway
  98		 */
  99		return ((instr_lo & 7) == 0x6);
 100#ifdef CONFIG_X86_64
 101	case 0x40:
 102		/*
 103		 * In AMD64 long mode 0x40..0x4F are valid REX prefixes
 104		 * Need to figure out under what instruction mode the
 105		 * instruction was issued. Could check the LDT for lm,
 106		 * but for now it's good enough to assume that long
 107		 * mode only uses well known segments or kernel.
 108		 */
 109		return (!user_mode(regs) || user_64bit_mode(regs));
 110#endif
 111	case 0x60:
 112		/* 0x64 thru 0x67 are valid prefixes in all modes. */
 113		return (instr_lo & 0xC) == 0x4;
 114	case 0xF0:
 115		/* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */
 116		return !instr_lo || (instr_lo>>1) == 1;
 117	case 0x00:
 118		/* Prefetch instruction is 0x0F0D or 0x0F18 */
 119		if (probe_kernel_address(instr, opcode))
 120			return 0;
 121
 122		*prefetch = (instr_lo == 0xF) &&
 123			(opcode == 0x0D || opcode == 0x18);
 124		return 0;
 125	default:
 126		return 0;
 127	}
 128}
 129
 
 
 
 
 
 
 
 
 
 130static int
 131is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
 132{
 133	unsigned char *max_instr;
 134	unsigned char *instr;
 135	int prefetch = 0;
 136
 
 
 
 
 137	/*
 138	 * If it was a exec (instruction fetch) fault on NX page, then
 139	 * do not ignore the fault:
 140	 */
 141	if (error_code & PF_INSTR)
 142		return 0;
 143
 144	instr = (void *)convert_ip_to_linear(current, regs);
 145	max_instr = instr + 15;
 146
 147	if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE)
 148		return 0;
 
 
 
 
 149
 150	while (instr < max_instr) {
 151		unsigned char opcode;
 152
 153		if (probe_kernel_address(instr, opcode))
 154			break;
 
 
 
 
 
 155
 156		instr++;
 157
 158		if (!check_prefetch_opcode(regs, instr, opcode, &prefetch))
 159			break;
 160	}
 161	return prefetch;
 162}
 163
 164static void
 165force_sig_info_fault(int si_signo, int si_code, unsigned long address,
 166		     struct task_struct *tsk, int fault)
 167{
 168	unsigned lsb = 0;
 169	siginfo_t info;
 170
 171	info.si_signo	= si_signo;
 172	info.si_errno	= 0;
 173	info.si_code	= si_code;
 174	info.si_addr	= (void __user *)address;
 175	if (fault & VM_FAULT_HWPOISON_LARGE)
 176		lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault)); 
 177	if (fault & VM_FAULT_HWPOISON)
 178		lsb = PAGE_SHIFT;
 179	info.si_addr_lsb = lsb;
 180
 181	force_sig_info(si_signo, &info, tsk);
 182}
 183
 184DEFINE_SPINLOCK(pgd_lock);
 185LIST_HEAD(pgd_list);
 186
 187#ifdef CONFIG_X86_32
 188static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
 189{
 190	unsigned index = pgd_index(address);
 191	pgd_t *pgd_k;
 
 192	pud_t *pud, *pud_k;
 193	pmd_t *pmd, *pmd_k;
 194
 195	pgd += index;
 196	pgd_k = init_mm.pgd + index;
 197
 198	if (!pgd_present(*pgd_k))
 199		return NULL;
 200
 201	/*
 202	 * set_pgd(pgd, *pgd_k); here would be useless on PAE
 203	 * and redundant with the set_pmd() on non-PAE. As would
 204	 * set_pud.
 205	 */
 206	pud = pud_offset(pgd, address);
 207	pud_k = pud_offset(pgd_k, address);
 
 
 
 
 
 208	if (!pud_present(*pud_k))
 209		return NULL;
 210
 211	pmd = pmd_offset(pud, address);
 212	pmd_k = pmd_offset(pud_k, address);
 213	if (!pmd_present(*pmd_k))
 214		return NULL;
 215
 216	if (!pmd_present(*pmd))
 217		set_pmd(pmd, *pmd_k);
 
 
 
 218	else
 219		BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k));
 220
 221	return pmd_k;
 222}
 223
 224void vmalloc_sync_all(void)
 225{
 226	unsigned long address;
 227
 228	if (SHARED_KERNEL_PMD)
 229		return;
 230
 231	for (address = VMALLOC_START & PMD_MASK;
 232	     address >= TASK_SIZE && address < FIXADDR_TOP;
 233	     address += PMD_SIZE) {
 234		struct page *page;
 235
 236		spin_lock(&pgd_lock);
 237		list_for_each_entry(page, &pgd_list, lru) {
 238			spinlock_t *pgt_lock;
 239			pmd_t *ret;
 240
 241			/* the pgt_lock only for Xen */
 242			pgt_lock = &pgd_page_get_mm(page)->page_table_lock;
 243
 244			spin_lock(pgt_lock);
 245			ret = vmalloc_sync_one(page_address(page), address);
 246			spin_unlock(pgt_lock);
 247
 248			if (!ret)
 249				break;
 250		}
 251		spin_unlock(&pgd_lock);
 252	}
 253}
 254
 255/*
 256 * 32-bit:
 257 *
 258 *   Handle a fault on the vmalloc or module mapping area
 
 
 
 
 
 
 
 
 
 
 
 259 */
 260static noinline __kprobes int vmalloc_fault(unsigned long address)
 261{
 262	unsigned long pgd_paddr;
 263	pmd_t *pmd_k;
 264	pte_t *pte_k;
 265
 266	/* Make sure we are in vmalloc area: */
 267	if (!(address >= VMALLOC_START && address < VMALLOC_END))
 268		return -1;
 269
 270	WARN_ON_ONCE(in_nmi());
 271
 272	/*
 273	 * Synchronize this task's top level page-table
 274	 * with the 'reference' page table.
 275	 *
 276	 * Do _not_ use "current" here. We might be inside
 277	 * an interrupt in the middle of a task switch..
 278	 */
 279	pgd_paddr = read_cr3();
 280	pmd_k = vmalloc_sync_one(__va(pgd_paddr), address);
 281	if (!pmd_k)
 282		return -1;
 283
 
 
 
 284	pte_k = pte_offset_kernel(pmd_k, address);
 285	if (!pte_present(*pte_k))
 286		return -1;
 287
 288	return 0;
 289}
 
 290
 291/*
 292 * Did it hit the DOS screen memory VA from vm86 mode?
 293 */
 294static inline void
 295check_v8086_mode(struct pt_regs *regs, unsigned long address,
 296		 struct task_struct *tsk)
 297{
 298	unsigned long bit;
 299
 300	if (!v8086_mode(regs))
 301		return;
 
 
 302
 303	bit = (address - 0xA0000) >> PAGE_SHIFT;
 304	if (bit < 32)
 305		tsk->thread.screen_bitmap |= 1 << bit;
 
 
 
 
 
 
 
 
 
 
 306}
 307
 308static bool low_pfn(unsigned long pfn)
 309{
 310	return pfn < max_low_pfn;
 311}
 312
 313static void dump_pagetable(unsigned long address)
 314{
 315	pgd_t *base = __va(read_cr3());
 316	pgd_t *pgd = &base[pgd_index(address)];
 
 
 317	pmd_t *pmd;
 318	pte_t *pte;
 319
 320#ifdef CONFIG_X86_PAE
 321	printk("*pdpt = %016Lx ", pgd_val(*pgd));
 322	if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd))
 323		goto out;
 
 
 
 324#endif
 325	pmd = pmd_offset(pud_offset(pgd, address), address);
 326	printk(KERN_CONT "*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd));
 
 
 
 327
 328	/*
 329	 * We must not directly access the pte in the highpte
 330	 * case if the page table is located in highmem.
 331	 * And let's rather not kmap-atomic the pte, just in case
 332	 * it's allocated already:
 333	 */
 334	if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_large(*pmd))
 335		goto out;
 336
 337	pte = pte_offset_kernel(pmd, address);
 338	printk("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte));
 339out:
 340	printk("\n");
 341}
 342
 343#else /* CONFIG_X86_64: */
 344
 345void vmalloc_sync_all(void)
 346{
 347	sync_global_pgds(VMALLOC_START & PGDIR_MASK, VMALLOC_END);
 348}
 349
 350/*
 351 * 64-bit:
 352 *
 353 *   Handle a fault on the vmalloc area
 354 *
 355 * This assumes no large pages in there.
 356 */
 357static noinline __kprobes int vmalloc_fault(unsigned long address)
 358{
 359	pgd_t *pgd, *pgd_ref;
 360	pud_t *pud, *pud_ref;
 361	pmd_t *pmd, *pmd_ref;
 362	pte_t *pte, *pte_ref;
 363
 364	/* Make sure we are in vmalloc area: */
 365	if (!(address >= VMALLOC_START && address < VMALLOC_END))
 366		return -1;
 367
 368	WARN_ON_ONCE(in_nmi());
 369
 370	/*
 371	 * Copy kernel mappings over when needed. This can also
 372	 * happen within a race in page table update. In the later
 373	 * case just flush:
 374	 */
 375	pgd = pgd_offset(current->active_mm, address);
 376	pgd_ref = pgd_offset_k(address);
 377	if (pgd_none(*pgd_ref))
 378		return -1;
 379
 380	if (pgd_none(*pgd))
 381		set_pgd(pgd, *pgd_ref);
 382	else
 383		BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref));
 384
 385	/*
 386	 * Below here mismatches are bugs because these lower tables
 387	 * are shared:
 388	 */
 389
 390	pud = pud_offset(pgd, address);
 391	pud_ref = pud_offset(pgd_ref, address);
 392	if (pud_none(*pud_ref))
 393		return -1;
 394
 395	if (pud_none(*pud) || pud_page_vaddr(*pud) != pud_page_vaddr(*pud_ref))
 396		BUG();
 397
 398	pmd = pmd_offset(pud, address);
 399	pmd_ref = pmd_offset(pud_ref, address);
 400	if (pmd_none(*pmd_ref))
 401		return -1;
 402
 403	if (pmd_none(*pmd) || pmd_page(*pmd) != pmd_page(*pmd_ref))
 404		BUG();
 405
 406	pte_ref = pte_offset_kernel(pmd_ref, address);
 407	if (!pte_present(*pte_ref))
 408		return -1;
 409
 410	pte = pte_offset_kernel(pmd, address);
 411
 412	/*
 413	 * Don't use pte_page here, because the mappings can point
 414	 * outside mem_map, and the NUMA hash lookup cannot handle
 415	 * that:
 416	 */
 417	if (!pte_present(*pte) || pte_pfn(*pte) != pte_pfn(*pte_ref))
 418		BUG();
 419
 420	return 0;
 421}
 422
 423static const char errata93_warning[] =
 424KERN_ERR 
 425"******* Your BIOS seems to not contain a fix for K8 errata #93\n"
 426"******* Working around it, but it may cause SEGVs or burn power.\n"
 427"******* Please consider a BIOS update.\n"
 428"******* Disabling USB legacy in the BIOS may also help.\n";
 429
 430/*
 431 * No vm86 mode in 64-bit mode:
 432 */
 433static inline void
 434check_v8086_mode(struct pt_regs *regs, unsigned long address,
 435		 struct task_struct *tsk)
 436{
 437}
 438
 439static int bad_address(void *p)
 440{
 441	unsigned long dummy;
 442
 443	return probe_kernel_address((unsigned long *)p, dummy);
 444}
 445
 446static void dump_pagetable(unsigned long address)
 447{
 448	pgd_t *base = __va(read_cr3() & PHYSICAL_PAGE_MASK);
 449	pgd_t *pgd = base + pgd_index(address);
 
 450	pud_t *pud;
 451	pmd_t *pmd;
 452	pte_t *pte;
 453
 454	if (bad_address(pgd))
 455		goto bad;
 456
 457	printk("PGD %lx ", pgd_val(*pgd));
 458
 459	if (!pgd_present(*pgd))
 460		goto out;
 461
 462	pud = pud_offset(pgd, address);
 
 
 
 
 
 
 
 
 463	if (bad_address(pud))
 464		goto bad;
 465
 466	printk("PUD %lx ", pud_val(*pud));
 467	if (!pud_present(*pud) || pud_large(*pud))
 468		goto out;
 469
 470	pmd = pmd_offset(pud, address);
 471	if (bad_address(pmd))
 472		goto bad;
 473
 474	printk("PMD %lx ", pmd_val(*pmd));
 475	if (!pmd_present(*pmd) || pmd_large(*pmd))
 476		goto out;
 477
 478	pte = pte_offset_kernel(pmd, address);
 479	if (bad_address(pte))
 480		goto bad;
 481
 482	printk("PTE %lx", pte_val(*pte));
 483out:
 484	printk("\n");
 485	return;
 486bad:
 487	printk("BAD\n");
 488}
 489
 490#endif /* CONFIG_X86_64 */
 491
 492/*
 493 * Workaround for K8 erratum #93 & buggy BIOS.
 494 *
 495 * BIOS SMM functions are required to use a specific workaround
 496 * to avoid corruption of the 64bit RIP register on C stepping K8.
 497 *
 498 * A lot of BIOS that didn't get tested properly miss this.
 499 *
 500 * The OS sees this as a page fault with the upper 32bits of RIP cleared.
 501 * Try to work around it here.
 502 *
 503 * Note we only handle faults in kernel here.
 504 * Does nothing on 32-bit.
 505 */
 506static int is_errata93(struct pt_regs *regs, unsigned long address)
 507{
 508#ifdef CONFIG_X86_64
 
 
 
 
 
 
 
 509	if (address != regs->ip)
 510		return 0;
 511
 512	if ((address >> 32) != 0)
 513		return 0;
 514
 515	address |= 0xffffffffUL << 32;
 516	if ((address >= (u64)_stext && address <= (u64)_etext) ||
 517	    (address >= MODULES_VADDR && address <= MODULES_END)) {
 518		printk_once(errata93_warning);
 519		regs->ip = address;
 520		return 1;
 521	}
 522#endif
 523	return 0;
 524}
 525
 526/*
 527 * Work around K8 erratum #100 K8 in compat mode occasionally jumps
 528 * to illegal addresses >4GB.
 529 *
 530 * We catch this in the page fault handler because these addresses
 531 * are not reachable. Just detect this case and return.  Any code
 532 * segment in LDT is compatibility mode.
 533 */
 534static int is_errata100(struct pt_regs *regs, unsigned long address)
 535{
 536#ifdef CONFIG_X86_64
 537	if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32))
 538		return 1;
 539#endif
 540	return 0;
 541}
 542
 543static int is_f00f_bug(struct pt_regs *regs, unsigned long address)
 
 
 544{
 545#ifdef CONFIG_X86_F00F_BUG
 546	unsigned long nr;
 547
 548	/*
 549	 * Pentium F0 0F C7 C8 bug workaround:
 550	 */
 551	if (boot_cpu_data.f00f_bug) {
 552		nr = (address - idt_descr.address) >> 3;
 553
 554		if (nr == 6) {
 555			do_invalid_op(regs, 0);
 556			return 1;
 557		}
 558	}
 559#endif
 560	return 0;
 561}
 562
 563static const char nx_warning[] = KERN_CRIT
 564"kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n";
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 565
 566static void
 567show_fault_oops(struct pt_regs *regs, unsigned long error_code,
 568		unsigned long address)
 569{
 570	if (!oops_may_print())
 571		return;
 572
 573	if (error_code & PF_INSTR) {
 574		unsigned int level;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 575
 576		pte_t *pte = lookup_address(address, &level);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 577
 578		if (pte && pte_present(*pte) && !pte_exec(*pte))
 579			printk(nx_warning, current_uid());
 580	}
 
 
 
 
 
 
 
 
 581
 582	printk(KERN_ALERT "BUG: unable to handle kernel ");
 583	if (address < PAGE_SIZE)
 584		printk(KERN_CONT "NULL pointer dereference");
 585	else
 586		printk(KERN_CONT "paging request");
 587
 588	printk(KERN_CONT " at %p\n", (void *) address);
 589	printk(KERN_ALERT "IP:");
 590	printk_address(regs->ip, 1);
 
 
 
 
 
 
 591
 592	dump_pagetable(address);
 
 
 
 593}
 594
 595static noinline void
 596pgtable_bad(struct pt_regs *regs, unsigned long error_code,
 597	    unsigned long address)
 598{
 599	struct task_struct *tsk;
 600	unsigned long flags;
 601	int sig;
 602
 603	flags = oops_begin();
 604	tsk = current;
 605	sig = SIGKILL;
 606
 607	printk(KERN_ALERT "%s: Corrupted page table at address %lx\n",
 608	       tsk->comm, address);
 609	dump_pagetable(address);
 610
 611	tsk->thread.cr2		= address;
 612	tsk->thread.trap_no	= 14;
 613	tsk->thread.error_code	= error_code;
 614
 615	if (__die("Bad pagetable", regs, error_code))
 616		sig = 0;
 617
 618	oops_end(flags, regs, sig);
 619}
 620
 621static noinline void
 622no_context(struct pt_regs *regs, unsigned long error_code,
 623	   unsigned long address)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 624{
 625	struct task_struct *tsk = current;
 626	unsigned long *stackend;
 
 
 
 
 
 
 
 
 
 
 
 
 627	unsigned long flags;
 628	int sig;
 629
 630	/* Are we prepared to handle this kernel fault? */
 631	if (fixup_exception(regs))
 632		return;
 
 
 
 
 633
 
 634	/*
 635	 * 32-bit:
 636	 *
 637	 *   Valid to do another page fault here, because if this fault
 638	 *   had been triggered by is_prefetch fixup_exception would have
 639	 *   handled it.
 640	 *
 641	 * 64-bit:
 642	 *
 643	 *   Hall of shame of CPU/BIOS bugs.
 644	 */
 645	if (is_prefetch(regs, error_code, address))
 646		return;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 647
 648	if (is_errata93(regs, address))
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 649		return;
 650
 
 651	/*
 652	 * Oops. The kernel tried to access some bad page. We'll have to
 653	 * terminate things with extreme prejudice:
 654	 */
 655	flags = oops_begin();
 656
 657	show_fault_oops(regs, error_code, address);
 658
 659	stackend = end_of_stack(tsk);
 660	if (tsk != &init_task && *stackend != STACK_END_MAGIC)
 661		printk(KERN_ALERT "Thread overran stack, or stack corrupted\n");
 662
 663	tsk->thread.cr2		= address;
 664	tsk->thread.trap_no	= 14;
 665	tsk->thread.error_code	= error_code;
 666
 667	sig = SIGKILL;
 668	if (__die("Oops", regs, error_code))
 669		sig = 0;
 670
 671	/* Executive summary in case the body of the oops scrolled away */
 672	printk(KERN_EMERG "CR2: %016lx\n", address);
 673
 674	oops_end(flags, regs, sig);
 675}
 676
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 677/*
 678 * Print out info about fatal segfaults, if the show_unhandled_signals
 679 * sysctl is set:
 680 */
 681static inline void
 682show_signal_msg(struct pt_regs *regs, unsigned long error_code,
 683		unsigned long address, struct task_struct *tsk)
 684{
 
 
 
 
 685	if (!unhandled_signal(tsk, SIGSEGV))
 686		return;
 687
 688	if (!printk_ratelimit())
 689		return;
 690
 691	printk("%s%s[%d]: segfault at %lx ip %p sp %p error %lx",
 692		task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
 693		tsk->comm, task_pid_nr(tsk), address,
 694		(void *)regs->ip, (void *)regs->sp, error_code);
 695
 696	print_vma_addr(KERN_CONT " in ", regs->ip);
 697
 
 
 
 
 
 
 
 
 698	printk(KERN_CONT "\n");
 
 
 699}
 700
 701static void
 702__bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
 703		       unsigned long address, int si_code)
 704{
 705	struct task_struct *tsk = current;
 706
 707	/* User mode accesses just cause a SIGSEGV */
 708	if (error_code & PF_USER) {
 709		/*
 710		 * It's possible to have interrupts off here:
 711		 */
 712		local_irq_enable();
 713
 714		/*
 715		 * Valid to do another page fault here because this one came
 716		 * from user space:
 717		 */
 718		if (is_prefetch(regs, error_code, address))
 719			return;
 720
 721		if (is_errata100(regs, address))
 722			return;
 
 
 
 723
 724#ifdef CONFIG_X86_64
 725		/*
 726		 * Instruction fetch faults in the vsyscall page might need
 727		 * emulation.
 728		 */
 729		if (unlikely((error_code & PF_INSTR) &&
 730			     ((address & ~0xfff) == VSYSCALL_START))) {
 731			if (emulate_vsyscall(regs, address))
 732				return;
 733		}
 734#endif
 735
 736		if (unlikely(show_unhandled_signals))
 737			show_signal_msg(regs, error_code, address, tsk);
 
 
 
 
 738
 739		/* Kernel addresses are always protection faults: */
 740		tsk->thread.cr2		= address;
 741		tsk->thread.error_code	= error_code | (address >= TASK_SIZE);
 742		tsk->thread.trap_no	= 14;
 743
 744		force_sig_info_fault(SIGSEGV, si_code, address, tsk, 0);
 745
 
 746		return;
 747	}
 748
 749	if (is_f00f_bug(regs, address))
 750		return;
 
 
 
 
 
 
 
 751
 752	no_context(regs, error_code, address);
 753}
 754
 755static noinline void
 756bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
 757		     unsigned long address)
 758{
 759	__bad_area_nosemaphore(regs, error_code, address, SEGV_MAPERR);
 760}
 761
 762static void
 763__bad_area(struct pt_regs *regs, unsigned long error_code,
 764	   unsigned long address, int si_code)
 
 765{
 766	struct mm_struct *mm = current->mm;
 767
 768	/*
 769	 * Something tried to access memory that isn't in our memory map..
 770	 * Fix it, but check if it's kernel or user first..
 771	 */
 772	up_read(&mm->mmap_sem);
 
 
 
 773
 774	__bad_area_nosemaphore(regs, error_code, address, si_code);
 775}
 776
 777static noinline void
 778bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address)
 779{
 780	__bad_area(regs, error_code, address, SEGV_MAPERR);
 
 
 
 
 
 
 
 
 
 
 
 781}
 782
 783static noinline void
 784bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
 785		      unsigned long address)
 786{
 787	__bad_area(regs, error_code, address, SEGV_ACCERR);
 788}
 789
 790/* TODO: fixup for "mm-invoke-oom-killer-from-page-fault.patch" */
 791static void
 792out_of_memory(struct pt_regs *regs, unsigned long error_code,
 793	      unsigned long address)
 794{
 795	/*
 796	 * We ran out of memory, call the OOM killer, and return the userspace
 797	 * (which will retry the fault, or kill us if we got oom-killed):
 
 798	 */
 799	up_read(&current->mm->mmap_sem);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 800
 801	pagefault_out_of_memory();
 
 
 
 802}
 803
 804static void
 805do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
 806	  unsigned int fault)
 807{
 808	struct task_struct *tsk = current;
 809	struct mm_struct *mm = tsk->mm;
 810	int code = BUS_ADRERR;
 811
 812	up_read(&mm->mmap_sem);
 813
 814	/* Kernel mode? Handle exceptions or die: */
 815	if (!(error_code & PF_USER)) {
 816		no_context(regs, error_code, address);
 
 817		return;
 818	}
 819
 820	/* User-space => ok to do another page fault: */
 821	if (is_prefetch(regs, error_code, address))
 822		return;
 823
 824	tsk->thread.cr2		= address;
 825	tsk->thread.error_code	= error_code;
 826	tsk->thread.trap_no	= 14;
 
 
 
 827
 828#ifdef CONFIG_MEMORY_FAILURE
 829	if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
 830		printk(KERN_ERR
 
 
 
 831	"MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
 832			tsk->comm, tsk->pid, address);
 833		code = BUS_MCEERR_AR;
 
 
 
 
 
 834	}
 835#endif
 836	force_sig_info_fault(SIGBUS, code, address, tsk, fault);
 837}
 838
 839static noinline int
 840mm_fault_error(struct pt_regs *regs, unsigned long error_code,
 841	       unsigned long address, unsigned int fault)
 842{
 843	/*
 844	 * Pagefault was interrupted by SIGKILL. We have no reason to
 845	 * continue pagefault.
 846	 */
 847	if (fatal_signal_pending(current)) {
 848		if (!(fault & VM_FAULT_RETRY))
 849			up_read(&current->mm->mmap_sem);
 850		if (!(error_code & PF_USER))
 851			no_context(regs, error_code, address);
 852		return 1;
 853	}
 854	if (!(fault & VM_FAULT_ERROR))
 855		return 0;
 856
 857	if (fault & VM_FAULT_OOM) {
 858		/* Kernel mode? Handle exceptions or die: */
 859		if (!(error_code & PF_USER)) {
 860			up_read(&current->mm->mmap_sem);
 861			no_context(regs, error_code, address);
 862			return 1;
 863		}
 864
 865		out_of_memory(regs, error_code, address);
 866	} else {
 867		if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
 868			     VM_FAULT_HWPOISON_LARGE))
 869			do_sigbus(regs, error_code, address, fault);
 870		else
 871			BUG();
 872	}
 873	return 1;
 874}
 875
 876static int spurious_fault_check(unsigned long error_code, pte_t *pte)
 877{
 878	if ((error_code & PF_WRITE) && !pte_write(*pte))
 879		return 0;
 880
 881	if ((error_code & PF_INSTR) && !pte_exec(*pte))
 882		return 0;
 883
 884	return 1;
 885}
 886
 887/*
 888 * Handle a spurious fault caused by a stale TLB entry.
 889 *
 890 * This allows us to lazily refresh the TLB when increasing the
 891 * permissions of a kernel page (RO -> RW or NX -> X).  Doing it
 892 * eagerly is very expensive since that implies doing a full
 893 * cross-processor TLB flush, even if no stale TLB entries exist
 894 * on other processors.
 895 *
 
 
 
 
 896 * There are no security implications to leaving a stale TLB when
 897 * increasing the permissions on a page.
 
 
 
 
 
 898 */
 899static noinline __kprobes int
 900spurious_fault(unsigned long error_code, unsigned long address)
 901{
 902	pgd_t *pgd;
 
 903	pud_t *pud;
 904	pmd_t *pmd;
 905	pte_t *pte;
 906	int ret;
 907
 908	/* Reserved-bit violation or user access to kernel space? */
 909	if (error_code & (PF_USER | PF_RSVD))
 
 
 
 
 
 
 
 
 
 910		return 0;
 911
 912	pgd = init_mm.pgd + pgd_index(address);
 913	if (!pgd_present(*pgd))
 914		return 0;
 915
 916	pud = pud_offset(pgd, address);
 
 
 
 
 
 
 
 917	if (!pud_present(*pud))
 918		return 0;
 919
 920	if (pud_large(*pud))
 921		return spurious_fault_check(error_code, (pte_t *) pud);
 922
 923	pmd = pmd_offset(pud, address);
 924	if (!pmd_present(*pmd))
 925		return 0;
 926
 927	if (pmd_large(*pmd))
 928		return spurious_fault_check(error_code, (pte_t *) pmd);
 929
 930	/*
 931	 * Note: don't use pte_present() here, since it returns true
 932	 * if the _PAGE_PROTNONE bit is set.  However, this aliases the
 933	 * _PAGE_GLOBAL bit, which for kernel pages give false positives
 934	 * when CONFIG_DEBUG_PAGEALLOC is used.
 935	 */
 936	pte = pte_offset_kernel(pmd, address);
 937	if (!(pte_flags(*pte) & _PAGE_PRESENT))
 938		return 0;
 939
 940	ret = spurious_fault_check(error_code, pte);
 941	if (!ret)
 942		return 0;
 943
 944	/*
 945	 * Make sure we have permissions in PMD.
 946	 * If not, then there's a bug in the page tables:
 947	 */
 948	ret = spurious_fault_check(error_code, (pte_t *) pmd);
 949	WARN_ONCE(!ret, "PMD has incorrect permission bits\n");
 950
 951	return ret;
 952}
 
 953
 954int show_unhandled_signals = 1;
 955
 956static inline int
 957access_error(unsigned long error_code, struct vm_area_struct *vma)
 958{
 959	if (error_code & PF_WRITE) {
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 960		/* write, present and write, not present: */
 
 
 961		if (unlikely(!(vma->vm_flags & VM_WRITE)))
 962			return 1;
 963		return 0;
 964	}
 965
 966	/* read, present: */
 967	if (unlikely(error_code & PF_PROT))
 968		return 1;
 969
 970	/* read, not present: */
 971	if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))))
 972		return 1;
 973
 974	return 0;
 975}
 976
 977static int fault_in_kernel_space(unsigned long address)
 978{
 
 
 
 
 
 
 
 
 979	return address >= TASK_SIZE_MAX;
 980}
 981
 982/*
 983 * This routine handles page faults.  It determines the address,
 984 * and the problem, and then passes it off to one of the appropriate
 985 * routines.
 986 */
 987dotraplinkage void __kprobes
 988do_page_fault(struct pt_regs *regs, unsigned long error_code)
 
 989{
 990	struct vm_area_struct *vma;
 991	struct task_struct *tsk;
 992	unsigned long address;
 993	struct mm_struct *mm;
 994	int fault;
 995	int write = error_code & PF_WRITE;
 996	unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE |
 997					(write ? FAULT_FLAG_WRITE : 0);
 998
 999	tsk = current;
1000	mm = tsk->mm;
1001
1002	/* Get the faulting address: */
1003	address = read_cr2();
1004
1005	/*
1006	 * Detect and handle instructions that would cause a page fault for
1007	 * both a tracked kernel page and a userspace page.
 
1008	 */
1009	if (kmemcheck_active(regs))
1010		kmemcheck_hide(regs);
1011	prefetchw(&mm->mmap_sem);
1012
1013	if (unlikely(kmmio_fault(regs, address)))
1014		return;
1015
 
1016	/*
1017	 * We fault-in kernel-space virtual memory on-demand. The
1018	 * 'reference' page table is init_mm.pgd.
1019	 *
1020	 * NOTE! We MUST NOT take any locks for this case. We may
1021	 * be in an interrupt or a critical region, and should
1022	 * only copy the information from the master page table,
1023	 * nothing more.
1024	 *
1025	 * This verifies that the fault happens in kernel space
1026	 * (error_code & 4) == 0, and that the fault was not a
1027	 * protection error (error_code & 9) == 0.
 
 
 
 
 
 
 
 
 
 
 
1028	 */
1029	if (unlikely(fault_in_kernel_space(address))) {
1030		if (!(error_code & (PF_RSVD | PF_USER | PF_PROT))) {
1031			if (vmalloc_fault(address) >= 0)
1032				return;
 
1033
1034			if (kmemcheck_fault(regs, address, error_code))
1035				return;
1036		}
1037
1038		/* Can handle a stale RO->RW TLB: */
1039		if (spurious_fault(error_code, address))
1040			return;
1041
1042		/* kprobes don't want to hook the spurious faults: */
1043		if (notify_page_fault(regs))
1044			return;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1045		/*
1046		 * Don't take the mm semaphore here. If we fixup a prefetch
1047		 * fault we could otherwise deadlock:
 
 
 
1048		 */
1049		bad_area_nosemaphore(regs, error_code, address);
 
1050
 
1051		return;
1052	}
1053
1054	/* kprobes don't want to hook the spurious faults: */
1055	if (unlikely(notify_page_fault(regs)))
1056		return;
 
1057	/*
1058	 * It's safe to allow irq's after cr2 has been saved and the
1059	 * vmalloc fault has been handled.
1060	 *
1061	 * User-mode registers count as a user access even for any
1062	 * potential system fault or CPU buglet:
1063	 */
1064	if (user_mode_vm(regs)) {
1065		local_irq_enable();
1066		error_code |= PF_USER;
1067	} else {
1068		if (regs->flags & X86_EFLAGS_IF)
1069			local_irq_enable();
1070	}
1071
1072	if (unlikely(error_code & PF_RSVD))
1073		pgtable_bad(regs, error_code, address);
1074
1075	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1076
1077	/*
1078	 * If we're in an interrupt, have no user context or are running
1079	 * in an atomic region then we must not take the fault:
1080	 */
1081	if (unlikely(in_atomic() || !mm)) {
1082		bad_area_nosemaphore(regs, error_code, address);
1083		return;
1084	}
1085
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1086	/*
1087	 * When running in the kernel we expect faults to occur only to
1088	 * addresses in user space.  All other faults represent errors in
1089	 * the kernel and should generate an OOPS.  Unfortunately, in the
1090	 * case of an erroneous fault occurring in a code path which already
1091	 * holds mmap_sem we will deadlock attempting to validate the fault
1092	 * against the address space.  Luckily the kernel only validly
1093	 * references user space from well defined areas of code, which are
1094	 * listed in the exceptions table.
1095	 *
1096	 * As the vast majority of faults will be valid we will only perform
1097	 * the source reference check when there is a possibility of a
1098	 * deadlock. Attempt to lock the address space, if we cannot we then
1099	 * validate the source. If this is invalid we can skip the address
1100	 * space check, thus avoiding the deadlock:
1101	 */
1102	if (unlikely(!down_read_trylock(&mm->mmap_sem))) {
1103		if ((error_code & PF_USER) == 0 &&
1104		    !search_exception_tables(regs->ip)) {
1105			bad_area_nosemaphore(regs, error_code, address);
1106			return;
1107		}
1108retry:
1109		down_read(&mm->mmap_sem);
1110	} else {
1111		/*
1112		 * The above down_read_trylock() might have succeeded in
1113		 * which case we'll have missed the might_sleep() from
1114		 * down_read():
1115		 */
1116		might_sleep();
1117	}
 
1118
1119	vma = find_vma(mm, address);
1120	if (unlikely(!vma)) {
1121		bad_area(regs, error_code, address);
 
 
 
 
 
 
 
1122		return;
1123	}
1124	if (likely(vma->vm_start <= address))
1125		goto good_area;
1126	if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
1127		bad_area(regs, error_code, address);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1128		return;
1129	}
1130	if (error_code & PF_USER) {
1131		/*
1132		 * Accessing the stack below %sp is always a bug.
1133		 * The large cushion allows instructions like enter
1134		 * and pusha to work. ("enter $65535, $31" pushes
1135		 * 32 pointers and then decrements %sp by 65535.)
1136		 */
1137		if (unlikely(address + 65536 + 32 * sizeof(unsigned long) < regs->sp)) {
1138			bad_area(regs, error_code, address);
1139			return;
1140		}
1141	}
1142	if (unlikely(expand_stack(vma, address))) {
1143		bad_area(regs, error_code, address);
1144		return;
1145	}
1146
1147	/*
1148	 * Ok, we have a good vm_area for this memory access, so
1149	 * we can handle it..
1150	 */
1151good_area:
1152	if (unlikely(access_error(error_code, vma))) {
1153		bad_area_access_error(regs, error_code, address);
1154		return;
1155	}
1156
1157	/*
1158	 * If for any reason at all we couldn't handle the fault,
1159	 * make sure we exit gracefully rather than endlessly redo
1160	 * the fault:
 
 
 
 
 
 
 
 
1161	 */
1162	fault = handle_mm_fault(mm, vma, address, flags);
1163
1164	if (unlikely(fault & (VM_FAULT_RETRY|VM_FAULT_ERROR))) {
1165		if (mm_fault_error(regs, error_code, address, fault))
1166			return;
 
 
 
 
 
 
 
1167	}
1168
 
 
 
 
1169	/*
1170	 * Major/minor page fault accounting is only done on the
1171	 * initial attempt. If we go through a retry, it is extremely
1172	 * likely that the page will be found in page cache at that point.
1173	 */
1174	if (flags & FAULT_FLAG_ALLOW_RETRY) {
1175		if (fault & VM_FAULT_MAJOR) {
1176			tsk->maj_flt++;
1177			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
1178				      regs, address);
1179		} else {
1180			tsk->min_flt++;
1181			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
1182				      regs, address);
1183		}
1184		if (fault & VM_FAULT_RETRY) {
1185			/* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
1186			 * of starvation. */
1187			flags &= ~FAULT_FLAG_ALLOW_RETRY;
1188			goto retry;
 
 
 
 
 
 
 
 
1189		}
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1190	}
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1191
1192	check_v8086_mode(regs, address, tsk);
 
 
1193
1194	up_read(&mm->mmap_sem);
1195}