fault.c 26.2 KB
Newer Older
Linus Torvalds's avatar
Linus Torvalds committed
1 2
/*
 *  Copyright (C) 1995  Linus Torvalds
Ingo Molnar's avatar
Ingo Molnar committed
3
 *  Copyright (C) 2001, 2002 Andi Kleen, SuSE Labs.
4
 *  Copyright (C) 2008-2009, Red Hat Inc., Ingo Molnar
Linus Torvalds's avatar
Linus Torvalds committed
5 6
 */
#include <linux/interrupt.h>
Ingo Molnar's avatar
Ingo Molnar committed
7 8
#include <linux/mmiotrace.h>
#include <linux/bootmem.h>
Linus Torvalds's avatar
Linus Torvalds committed
9
#include <linux/compiler.h>
Harvey Harrison's avatar
Harvey Harrison committed
10
#include <linux/highmem.h>
11
#include <linux/kprobes.h>
12
#include <linux/uaccess.h>
Ingo Molnar's avatar
Ingo Molnar committed
13 14 15 16 17 18 19
#include <linux/vmalloc.h>
#include <linux/vt_kern.h>
#include <linux/signal.h>
#include <linux/kernel.h>
#include <linux/ptrace.h>
#include <linux/string.h>
#include <linux/module.h>
20
#include <linux/kdebug.h>
Ingo Molnar's avatar
Ingo Molnar committed
21
#include <linux/errno.h>
22
#include <linux/magic.h>
Ingo Molnar's avatar
Ingo Molnar committed
23 24 25 26 27 28 29 30 31
#include <linux/sched.h>
#include <linux/types.h>
#include <linux/init.h>
#include <linux/mman.h>
#include <linux/tty.h>
#include <linux/smp.h>
#include <linux/mm.h>

#include <asm-generic/sections.h>
Linus Torvalds's avatar
Linus Torvalds committed
32 33

#include <asm/tlbflush.h>
Ingo Molnar's avatar
Ingo Molnar committed
34 35 36
#include <asm/pgalloc.h>
#include <asm/segment.h>
#include <asm/system.h>
Linus Torvalds's avatar
Linus Torvalds committed
37
#include <asm/proto.h>
38
#include <asm/traps.h>
Ingo Molnar's avatar
Ingo Molnar committed
39
#include <asm/desc.h>
Linus Torvalds's avatar
Linus Torvalds committed
40

41
/*
Ingo Molnar's avatar
Ingo Molnar committed
42 43 44 45 46 47 48
 * Page fault error code bits:
 *
 *   bit 0 ==	 0: no page found	1: protection fault
 *   bit 1 ==	 0: read access		1: write access
 *   bit 2 ==	 0: kernel-mode access	1: user-mode access
 *   bit 3 ==				1: use of reserved bit detected
 *   bit 4 ==				1: fault was an instruction fetch
49
 */
Ingo Molnar's avatar
Ingo Molnar committed
50 51 52 53 54 55 56 57
enum x86_pf_error_code {

	PF_PROT		=		1 << 0,
	PF_WRITE	=		1 << 1,
	PF_USER		=		1 << 2,
	PF_RSVD		=		1 << 3,
	PF_INSTR	=		1 << 4,
};
58

59 60 61
/*
 * (returns 0 if mmiotrace is disabled)
 */
62
static inline int kmmio_fault(struct pt_regs *regs, unsigned long addr)
63
{
64 65 66 67
	if (unlikely(is_kmmio_active()))
		if (kmmio_handler(regs, addr) == 1)
			return -1;
	return 0;
68 69
}

70
static inline int notify_page_fault(struct pt_regs *regs)
71
{
72 73 74
	int ret = 0;

	/* kprobe_running() needs smp_processor_id() */
75
	if (kprobes_built_in() && !user_mode_vm(regs)) {
76 77 78 79 80
		preempt_disable();
		if (kprobe_running() && kprobe_fault_handler(regs, 14))
			ret = 1;
		preempt_enable();
	}
81

82
	return ret;
83
}
84

85
/*
Ingo Molnar's avatar
Ingo Molnar committed
86 87 88 89 90 91
 * Prefetch quirks:
 *
 * 32-bit mode:
 *
 *   Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
 *   Check that here and ignore it.
92
 *
Ingo Molnar's avatar
Ingo Molnar committed
93
 * 64-bit mode:
94
 *
Ingo Molnar's avatar
Ingo Molnar committed
95 96 97 98
 *   Sometimes the CPU reports invalid exceptions on prefetch.
 *   Check that here and ignore it.
 *
 * Opcode checker based on code by Richard Brunner.
99
 */
100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146
static inline int
check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr,
		      unsigned char opcode, int *prefetch)
{
	unsigned char instr_hi = opcode & 0xf0;
	unsigned char instr_lo = opcode & 0x0f;

	switch (instr_hi) {
	case 0x20:
	case 0x30:
		/*
		 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes.
		 * In X86_64 long mode, the CPU will signal invalid
		 * opcode if some of these prefixes are present so
		 * X86_64 will never get here anyway
		 */
		return ((instr_lo & 7) == 0x6);
#ifdef CONFIG_X86_64
	case 0x40:
		/*
		 * In AMD64 long mode 0x40..0x4F are valid REX prefixes
		 * Need to figure out under what instruction mode the
		 * instruction was issued. Could check the LDT for lm,
		 * but for now it's good enough to assume that long
		 * mode only uses well known segments or kernel.
		 */
		return (!user_mode(regs)) || (regs->cs == __USER_CS);
#endif
	case 0x60:
		/* 0x64 thru 0x67 are valid prefixes in all modes. */
		return (instr_lo & 0xC) == 0x4;
	case 0xF0:
		/* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */
		return !instr_lo || (instr_lo>>1) == 1;
	case 0x00:
		/* Prefetch instruction is 0x0F0D or 0x0F18 */
		if (probe_kernel_address(instr, opcode))
			return 0;

		*prefetch = (instr_lo == 0xF) &&
			(opcode == 0x0D || opcode == 0x18);
		return 0;
	default:
		return 0;
	}
}

Ingo Molnar's avatar
Ingo Molnar committed
147 148
static int
is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
149
{
Ingo Molnar's avatar
Ingo Molnar committed
150
	unsigned char *max_instr;
151
	unsigned char *instr;
152
	int prefetch = 0;
Linus Torvalds's avatar
Linus Torvalds committed
153

Ingo Molnar's avatar
Ingo Molnar committed
154 155 156 157
	/*
	 * If it was a exec (instruction fetch) fault on NX page, then
	 * do not ignore the fault:
	 */
158
	if (error_code & PF_INSTR)
Linus Torvalds's avatar
Linus Torvalds committed
159
		return 0;
160

161
	instr = (void *)convert_ip_to_linear(current, regs);
162
	max_instr = instr + 15;
Linus Torvalds's avatar
Linus Torvalds committed
163

164
	if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE)
Linus Torvalds's avatar
Linus Torvalds committed
165 166
		return 0;

167
	while (instr < max_instr) {
Ingo Molnar's avatar
Ingo Molnar committed
168
		unsigned char opcode;
Linus Torvalds's avatar
Linus Torvalds committed
169

170
		if (probe_kernel_address(instr, opcode))
171
			break;
Linus Torvalds's avatar
Linus Torvalds committed
172 173 174

		instr++;

175
		if (!check_prefetch_opcode(regs, instr, opcode, &prefetch))
Linus Torvalds's avatar
Linus Torvalds committed
176 177 178 179 180
			break;
	}
	return prefetch;
}

Ingo Molnar's avatar
Ingo Molnar committed
181 182 183
static void
force_sig_info_fault(int si_signo, int si_code, unsigned long address,
		     struct task_struct *tsk)
184 185 186
{
	siginfo_t info;

Ingo Molnar's avatar
Ingo Molnar committed
187 188 189 190 191
	info.si_signo	= si_signo;
	info.si_errno	= 0;
	info.si_code	= si_code;
	info.si_addr	= (void __user *)address;

192 193 194
	force_sig_info(si_signo, &info, tsk);
}

195 196 197 198 199
DEFINE_SPINLOCK(pgd_lock);
LIST_HEAD(pgd_list);

#ifdef CONFIG_X86_32
static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
200
{
201 202 203 204
	unsigned index = pgd_index(address);
	pgd_t *pgd_k;
	pud_t *pud, *pud_k;
	pmd_t *pmd, *pmd_k;
Ingo Molnar's avatar
Ingo Molnar committed
205

206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308
	pgd += index;
	pgd_k = init_mm.pgd + index;

	if (!pgd_present(*pgd_k))
		return NULL;

	/*
	 * set_pgd(pgd, *pgd_k); here would be useless on PAE
	 * and redundant with the set_pmd() on non-PAE. As would
	 * set_pud.
	 */
	pud = pud_offset(pgd, address);
	pud_k = pud_offset(pgd_k, address);
	if (!pud_present(*pud_k))
		return NULL;

	pmd = pmd_offset(pud, address);
	pmd_k = pmd_offset(pud_k, address);
	if (!pmd_present(*pmd_k))
		return NULL;

	if (!pmd_present(*pmd)) {
		set_pmd(pmd, *pmd_k);
		arch_flush_lazy_mmu_mode();
	} else {
		BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k));
	}

	return pmd_k;
}

void vmalloc_sync_all(void)
{
	unsigned long address;

	if (SHARED_KERNEL_PMD)
		return;

	for (address = VMALLOC_START & PMD_MASK;
	     address >= TASK_SIZE && address < FIXADDR_TOP;
	     address += PMD_SIZE) {

		unsigned long flags;
		struct page *page;

		spin_lock_irqsave(&pgd_lock, flags);
		list_for_each_entry(page, &pgd_list, lru) {
			if (!vmalloc_sync_one(page_address(page), address))
				break;
		}
		spin_unlock_irqrestore(&pgd_lock, flags);
	}
}

/*
 * 32-bit:
 *
 *   Handle a fault on the vmalloc or module mapping area
 */
static noinline int vmalloc_fault(unsigned long address)
{
	unsigned long pgd_paddr;
	pmd_t *pmd_k;
	pte_t *pte_k;

	/* Make sure we are in vmalloc area: */
	if (!(address >= VMALLOC_START && address < VMALLOC_END))
		return -1;

	/*
	 * Synchronize this task's top level page-table
	 * with the 'reference' page table.
	 *
	 * Do _not_ use "current" here. We might be inside
	 * an interrupt in the middle of a task switch..
	 */
	pgd_paddr = read_cr3();
	pmd_k = vmalloc_sync_one(__va(pgd_paddr), address);
	if (!pmd_k)
		return -1;

	pte_k = pte_offset_kernel(pmd_k, address);
	if (!pte_present(*pte_k))
		return -1;

	return 0;
}

/*
 * Did it hit the DOS screen memory VA from vm86 mode?
 */
static inline void
check_v8086_mode(struct pt_regs *regs, unsigned long address,
		 struct task_struct *tsk)
{
	unsigned long bit;

	if (!v8086_mode(regs))
		return;

	bit = (address - 0xA0000) >> PAGE_SHIFT;
	if (bit < 32)
		tsk->thread.screen_bitmap |= 1 << bit;
309
}
Linus Torvalds's avatar
Linus Torvalds committed
310

311
static void dump_pagetable(unsigned long address)
Linus Torvalds's avatar
Linus Torvalds committed
312
{
313 314 315 316
	__typeof__(pte_val(__pte(0))) page;

	page = read_cr3();
	page = ((__typeof__(page) *) __va(page))[address >> PGDIR_SHIFT];
Ingo Molnar's avatar
Ingo Molnar committed
317

318 319 320 321 322 323
#ifdef CONFIG_X86_PAE
	printk("*pdpt = %016Lx ", page);
	if ((page >> PAGE_SHIFT) < max_low_pfn
	    && page & _PAGE_PRESENT) {
		page &= PAGE_MASK;
		page = ((__typeof__(page) *) __va(page))[(address >> PMD_SHIFT)
Ingo Molnar's avatar
Ingo Molnar committed
324
							& (PTRS_PER_PMD - 1)];
325 326 327 328 329 330 331 332 333 334 335
		printk(KERN_CONT "*pde = %016Lx ", page);
		page &= ~_PAGE_NX;
	}
#else
	printk("*pde = %08lx ", page);
#endif

	/*
	 * We must not directly access the pte in the highpte
	 * case if the page table is located in highmem.
	 * And let's rather not kmap-atomic the pte, just in case
Ingo Molnar's avatar
Ingo Molnar committed
336
	 * it's allocated already:
337 338 339 340
	 */
	if ((page >> PAGE_SHIFT) < max_low_pfn
	    && (page & _PAGE_PRESENT)
	    && !(page & _PAGE_PSE)) {
Ingo Molnar's avatar
Ingo Molnar committed
341

342 343
		page &= PAGE_MASK;
		page = ((__typeof__(page) *) __va(page))[(address >> PAGE_SHIFT)
Ingo Molnar's avatar
Ingo Molnar committed
344
							& (PTRS_PER_PTE - 1)];
345 346 347 348
		printk("*pte = %0*Lx ", sizeof(page)*2, (u64)page);
	}

	printk("\n");
349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474
}

#else /* CONFIG_X86_64: */

void vmalloc_sync_all(void)
{
	unsigned long address;

	for (address = VMALLOC_START & PGDIR_MASK; address <= VMALLOC_END;
	     address += PGDIR_SIZE) {

		const pgd_t *pgd_ref = pgd_offset_k(address);
		unsigned long flags;
		struct page *page;

		if (pgd_none(*pgd_ref))
			continue;

		spin_lock_irqsave(&pgd_lock, flags);
		list_for_each_entry(page, &pgd_list, lru) {
			pgd_t *pgd;
			pgd = (pgd_t *)page_address(page) + pgd_index(address);
			if (pgd_none(*pgd))
				set_pgd(pgd, *pgd_ref);
			else
				BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref));
		}
		spin_unlock_irqrestore(&pgd_lock, flags);
	}
}

/*
 * 64-bit:
 *
 *   Handle a fault on the vmalloc area
 *
 * This assumes no large pages in there.
 */
static noinline int vmalloc_fault(unsigned long address)
{
	pgd_t *pgd, *pgd_ref;
	pud_t *pud, *pud_ref;
	pmd_t *pmd, *pmd_ref;
	pte_t *pte, *pte_ref;

	/* Make sure we are in vmalloc area: */
	if (!(address >= VMALLOC_START && address < VMALLOC_END))
		return -1;

	/*
	 * Copy kernel mappings over when needed. This can also
	 * happen within a race in page table update. In the later
	 * case just flush:
	 */
	pgd = pgd_offset(current->active_mm, address);
	pgd_ref = pgd_offset_k(address);
	if (pgd_none(*pgd_ref))
		return -1;

	if (pgd_none(*pgd))
		set_pgd(pgd, *pgd_ref);
	else
		BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref));

	/*
	 * Below here mismatches are bugs because these lower tables
	 * are shared:
	 */

	pud = pud_offset(pgd, address);
	pud_ref = pud_offset(pgd_ref, address);
	if (pud_none(*pud_ref))
		return -1;

	if (pud_none(*pud) || pud_page_vaddr(*pud) != pud_page_vaddr(*pud_ref))
		BUG();

	pmd = pmd_offset(pud, address);
	pmd_ref = pmd_offset(pud_ref, address);
	if (pmd_none(*pmd_ref))
		return -1;

	if (pmd_none(*pmd) || pmd_page(*pmd) != pmd_page(*pmd_ref))
		BUG();

	pte_ref = pte_offset_kernel(pmd_ref, address);
	if (!pte_present(*pte_ref))
		return -1;

	pte = pte_offset_kernel(pmd, address);

	/*
	 * Don't use pte_page here, because the mappings can point
	 * outside mem_map, and the NUMA hash lookup cannot handle
	 * that:
	 */
	if (!pte_present(*pte) || pte_pfn(*pte) != pte_pfn(*pte_ref))
		BUG();

	return 0;
}

static const char errata93_warning[] =
KERN_ERR "******* Your BIOS seems to not contain a fix for K8 errata #93\n"
KERN_ERR "******* Working around it, but it may cause SEGVs or burn power.\n"
KERN_ERR "******* Please consider a BIOS update.\n"
KERN_ERR "******* Disabling USB legacy in the BIOS may also help.\n";

/*
 * No vm86 mode in 64-bit mode:
 */
static inline void
check_v8086_mode(struct pt_regs *regs, unsigned long address,
		 struct task_struct *tsk)
{
}

static int bad_address(void *p)
{
	unsigned long dummy;

	return probe_kernel_address((unsigned long *)p, dummy);
}

static void dump_pagetable(unsigned long address)
{
Linus Torvalds's avatar
Linus Torvalds committed
475 476 477 478 479
	pgd_t *pgd;
	pud_t *pud;
	pmd_t *pmd;
	pte_t *pte;

480
	pgd = (pgd_t *)read_cr3();
Linus Torvalds's avatar
Linus Torvalds committed
481

482
	pgd = __va((unsigned long)pgd & PHYSICAL_PAGE_MASK);
Ingo Molnar's avatar
Ingo Molnar committed
483

Linus Torvalds's avatar
Linus Torvalds committed
484
	pgd += pgd_index(address);
Ingo Molnar's avatar
Ingo Molnar committed
485 486 487
	if (bad_address(pgd))
		goto bad;

488
	printk("PGD %lx ", pgd_val(*pgd));
Ingo Molnar's avatar
Ingo Molnar committed
489 490 491

	if (!pgd_present(*pgd))
		goto out;
Linus Torvalds's avatar
Linus Torvalds committed
492

493
	pud = pud_offset(pgd, address);
Ingo Molnar's avatar
Ingo Molnar committed
494 495 496
	if (bad_address(pud))
		goto bad;

Linus Torvalds's avatar
Linus Torvalds committed
497
	printk("PUD %lx ", pud_val(*pud));
498
	if (!pud_present(*pud) || pud_large(*pud))
Ingo Molnar's avatar
Ingo Molnar committed
499
		goto out;
Linus Torvalds's avatar
Linus Torvalds committed
500 501

	pmd = pmd_offset(pud, address);
Ingo Molnar's avatar
Ingo Molnar committed
502 503 504
	if (bad_address(pmd))
		goto bad;

Linus Torvalds's avatar
Linus Torvalds committed
505
	printk("PMD %lx ", pmd_val(*pmd));
Ingo Molnar's avatar
Ingo Molnar committed
506 507
	if (!pmd_present(*pmd) || pmd_large(*pmd))
		goto out;
Linus Torvalds's avatar
Linus Torvalds committed
508 509

	pte = pte_offset_kernel(pmd, address);
Ingo Molnar's avatar
Ingo Molnar committed
510 511 512
	if (bad_address(pte))
		goto bad;

513
	printk("PTE %lx", pte_val(*pte));
Ingo Molnar's avatar
Ingo Molnar committed
514
out:
Linus Torvalds's avatar
Linus Torvalds committed
515 516 517 518
	printk("\n");
	return;
bad:
	printk("BAD\n");
519 520
}

521
#endif /* CONFIG_X86_64 */
Linus Torvalds's avatar
Linus Torvalds committed
522

Ingo Molnar's avatar
Ingo Molnar committed
523 524 525 526 527 528 529 530 531 532 533 534 535
/*
 * Workaround for K8 erratum #93 & buggy BIOS.
 *
 * BIOS SMM functions are required to use a specific workaround
 * to avoid corruption of the 64bit RIP register on C stepping K8.
 *
 * A lot of BIOS that didn't get tested properly miss this.
 *
 * The OS sees this as a page fault with the upper 32bits of RIP cleared.
 * Try to work around it here.
 *
 * Note we only handle faults in kernel here.
 * Does nothing on 32-bit.
536
 */
537
static int is_errata93(struct pt_regs *regs, unsigned long address)
Linus Torvalds's avatar
Linus Torvalds committed
538
{
539
#ifdef CONFIG_X86_64
Ingo Molnar's avatar
Ingo Molnar committed
540 541
	static int once;

542
	if (address != regs->ip)
Linus Torvalds's avatar
Linus Torvalds committed
543
		return 0;
Ingo Molnar's avatar
Ingo Molnar committed
544

545
	if ((address >> 32) != 0)
Linus Torvalds's avatar
Linus Torvalds committed
546
		return 0;
Ingo Molnar's avatar
Ingo Molnar committed
547

Linus Torvalds's avatar
Linus Torvalds committed
548
	address |= 0xffffffffUL << 32;
549 550
	if ((address >= (u64)_stext && address <= (u64)_etext) ||
	    (address >= MODULES_VADDR && address <= MODULES_END)) {
Ingo Molnar's avatar
Ingo Molnar committed
551
		if (!once) {
552
			printk(errata93_warning);
Ingo Molnar's avatar
Ingo Molnar committed
553
			once = 1;
Linus Torvalds's avatar
Linus Torvalds committed
554
		}
555
		regs->ip = address;
Linus Torvalds's avatar
Linus Torvalds committed
556 557
		return 1;
	}
558
#endif
Linus Torvalds's avatar
Linus Torvalds committed
559
	return 0;
560
}
Linus Torvalds's avatar
Linus Torvalds committed
561

562
/*
Ingo Molnar's avatar
Ingo Molnar committed
563 564 565 566 567
 * Work around K8 erratum #100 K8 in compat mode occasionally jumps
 * to illegal addresses >4GB.
 *
 * We catch this in the page fault handler because these addresses
 * are not reachable. Just detect this case and return.  Any code
568 569 570 571 572
 * segment in LDT is compatibility mode.
 */
static int is_errata100(struct pt_regs *regs, unsigned long address)
{
#ifdef CONFIG_X86_64
Ingo Molnar's avatar
Ingo Molnar committed
573
	if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32))
574 575 576 577 578
		return 1;
#endif
	return 0;
}

579 580 581 582
static int is_f00f_bug(struct pt_regs *regs, unsigned long address)
{
#ifdef CONFIG_X86_F00F_BUG
	unsigned long nr;
Ingo Molnar's avatar
Ingo Molnar committed
583

584
	/*
Ingo Molnar's avatar
Ingo Molnar committed
585
	 * Pentium F0 0F C7 C8 bug workaround:
586 587 588 589 590 591 592 593 594 595 596 597 598
	 */
	if (boot_cpu_data.f00f_bug) {
		nr = (address - idt_descr.address) >> 3;

		if (nr == 6) {
			do_invalid_op(regs, 0);
			return 1;
		}
	}
#endif
	return 0;
}

599 600 601
static const char nx_warning[] = KERN_CRIT
"kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n";

Ingo Molnar's avatar
Ingo Molnar committed
602 603 604
static void
show_fault_oops(struct pt_regs *regs, unsigned long error_code,
		unsigned long address)
605
{
606 607 608 609
	if (!oops_may_print())
		return;

	if (error_code & PF_INSTR) {
610
		unsigned int level;
Ingo Molnar's avatar
Ingo Molnar committed
611

612 613
		pte_t *pte = lookup_address(address, &level);

614 615
		if (pte && pte_present(*pte) && !pte_exec(*pte))
			printk(nx_warning, current_uid());
616 617
	}

618
	printk(KERN_ALERT "BUG: unable to handle kernel ");
619
	if (address < PAGE_SIZE)
620
		printk(KERN_CONT "NULL pointer dereference");
621
	else
622
		printk(KERN_CONT "paging request");
Ingo Molnar's avatar
Ingo Molnar committed
623

624
	printk(KERN_CONT " at %p\n", (void *) address);
625
	printk(KERN_ALERT "IP:");
626
	printk_address(regs->ip, 1);
Ingo Molnar's avatar
Ingo Molnar committed
627

628 629 630
	dump_pagetable(address);
}

Ingo Molnar's avatar
Ingo Molnar committed
631 632 633
static noinline void
pgtable_bad(struct pt_regs *regs, unsigned long error_code,
	    unsigned long address)
Linus Torvalds's avatar
Linus Torvalds committed
634
{
Ingo Molnar's avatar
Ingo Molnar committed
635 636 637 638 639 640 641
	struct task_struct *tsk;
	unsigned long flags;
	int sig;

	flags = oops_begin();
	tsk = current;
	sig = SIGKILL;
642

Linus Torvalds's avatar
Linus Torvalds committed
643
	printk(KERN_ALERT "%s: Corrupted page table at address %lx\n",
644
	       tsk->comm, address);
Linus Torvalds's avatar
Linus Torvalds committed
645
	dump_pagetable(address);
Ingo Molnar's avatar
Ingo Molnar committed
646 647 648 649 650

	tsk->thread.cr2		= address;
	tsk->thread.trap_no	= 14;
	tsk->thread.error_code	= error_code;

651
	if (__die("Bad pagetable", regs, error_code))
652
		sig = 0;
Ingo Molnar's avatar
Ingo Molnar committed
653

654
	oops_end(flags, regs, sig);
Linus Torvalds's avatar
Linus Torvalds committed
655 656
}

Ingo Molnar's avatar
Ingo Molnar committed
657 658 659
static noinline void
no_context(struct pt_regs *regs, unsigned long error_code,
	   unsigned long address)
660 661
{
	struct task_struct *tsk = current;
662
	unsigned long *stackend;
663 664 665
	unsigned long flags;
	int sig;

Ingo Molnar's avatar
Ingo Molnar committed
666
	/* Are we prepared to handle this kernel fault? */
667 668 669 670
	if (fixup_exception(regs))
		return;

	/*
Ingo Molnar's avatar
Ingo Molnar committed
671 672 673 674 675 676 677
	 * 32-bit:
	 *
	 *   Valid to do another page fault here, because if this fault
	 *   had been triggered by is_prefetch fixup_exception would have
	 *   handled it.
	 *
	 * 64-bit:
678
	 *
Ingo Molnar's avatar
Ingo Molnar committed
679
	 *   Hall of shame of CPU/BIOS bugs.
680 681 682 683 684 685 686 687 688
	 */
	if (is_prefetch(regs, error_code, address))
		return;

	if (is_errata93(regs, address))
		return;

	/*
	 * Oops. The kernel tried to access some bad page. We'll have to
Ingo Molnar's avatar
Ingo Molnar committed
689
	 * terminate things with extreme prejudice:
690 691 692 693 694
	 */
	flags = oops_begin();

	show_fault_oops(regs, error_code, address);

Ingo Molnar's avatar
Ingo Molnar committed
695
	stackend = end_of_stack(tsk);
696 697 698
	if (*stackend != STACK_END_MAGIC)
		printk(KERN_ALERT "Thread overran stack, or stack corrupted\n");

699 700 701
	tsk->thread.cr2		= address;
	tsk->thread.trap_no	= 14;
	tsk->thread.error_code	= error_code;
702 703 704 705

	sig = SIGKILL;
	if (__die("Oops", regs, error_code))
		sig = 0;
Ingo Molnar's avatar
Ingo Molnar committed
706

707 708
	/* Executive summary in case the body of the oops scrolled away */
	printk(KERN_EMERG "CR2: %016lx\n", address);
Ingo Molnar's avatar
Ingo Molnar committed
709

710 711 712
	oops_end(flags, regs, sig);
}

Ingo Molnar's avatar
Ingo Molnar committed
713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739
/*
 * Print out info about fatal segfaults, if the show_unhandled_signals
 * sysctl is set:
 */
static inline void
show_signal_msg(struct pt_regs *regs, unsigned long error_code,
		unsigned long address, struct task_struct *tsk)
{
	if (!unhandled_signal(tsk, SIGSEGV))
		return;

	if (!printk_ratelimit())
		return;

	printk(KERN_CONT "%s%s[%d]: segfault at %lx ip %p sp %p error %lx",
		task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
		tsk->comm, task_pid_nr(tsk), address,
		(void *)regs->ip, (void *)regs->sp, error_code);

	print_vma_addr(KERN_CONT " in ", regs->ip);

	printk(KERN_CONT "\n");
}

static void
__bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
		       unsigned long address, int si_code)
740 741 742 743 744 745
{
	struct task_struct *tsk = current;

	/* User mode accesses just cause a SIGSEGV */
	if (error_code & PF_USER) {
		/*
Ingo Molnar's avatar
Ingo Molnar committed
746
		 * It's possible to have interrupts off here:
747 748 749 750 751
		 */
		local_irq_enable();

		/*
		 * Valid to do another page fault here because this one came
Ingo Molnar's avatar
Ingo Molnar committed
752
		 * from user space:
753 754 755 756 757 758 759
		 */
		if (is_prefetch(regs, error_code, address))
			return;

		if (is_errata100(regs, address))
			return;

Ingo Molnar's avatar
Ingo Molnar committed
760 761 762 763 764 765 766
		if (unlikely(show_unhandled_signals))
			show_signal_msg(regs, error_code, address, tsk);

		/* Kernel addresses are always protection faults: */
		tsk->thread.cr2		= address;
		tsk->thread.error_code	= error_code | (address >= TASK_SIZE);
		tsk->thread.trap_no	= 14;
767 768

		force_sig_info_fault(SIGSEGV, si_code, address, tsk);
Ingo Molnar's avatar
Ingo Molnar committed
769

770 771 772 773 774 775 776 777 778
		return;
	}

	if (is_f00f_bug(regs, address))
		return;

	no_context(regs, error_code, address);
}

Ingo Molnar's avatar
Ingo Molnar committed
779 780 781
static noinline void
bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
		     unsigned long address)
782 783 784 785
{
	__bad_area_nosemaphore(regs, error_code, address, SEGV_MAPERR);
}

Ingo Molnar's avatar
Ingo Molnar committed
786 787 788
static void
__bad_area(struct pt_regs *regs, unsigned long error_code,
	   unsigned long address, int si_code)
789 790 791 792 793 794 795 796 797 798 799 800
{
	struct mm_struct *mm = current->mm;

	/*
	 * Something tried to access memory that isn't in our memory map..
	 * Fix it, but check if it's kernel or user first..
	 */
	up_read(&mm->mmap_sem);

	__bad_area_nosemaphore(regs, error_code, address, si_code);
}

Ingo Molnar's avatar
Ingo Molnar committed
801 802
static noinline void
bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address)
803 804 805 806
{
	__bad_area(regs, error_code, address, SEGV_MAPERR);
}

Ingo Molnar's avatar
Ingo Molnar committed
807 808 809
static noinline void
bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
		      unsigned long address)
810 811 812 813 814
{
	__bad_area(regs, error_code, address, SEGV_ACCERR);
}

/* TODO: fixup for "mm-invoke-oom-killer-from-page-fault.patch" */
Ingo Molnar's avatar
Ingo Molnar committed
815 816 817
static void
out_of_memory(struct pt_regs *regs, unsigned long error_code,
	      unsigned long address)
818 819 820
{
	/*
	 * We ran out of memory, call the OOM killer, and return the userspace
Ingo Molnar's avatar
Ingo Molnar committed
821
	 * (which will retry the fault, or kill us if we got oom-killed):
822 823
	 */
	up_read(&current->mm->mmap_sem);
Ingo Molnar's avatar
Ingo Molnar committed
824

825 826 827
	pagefault_out_of_memory();
}

Ingo Molnar's avatar
Ingo Molnar committed
828 829
static void
do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address)
830 831 832 833 834 835
{
	struct task_struct *tsk = current;
	struct mm_struct *mm = tsk->mm;

	up_read(&mm->mmap_sem);

Ingo Molnar's avatar
Ingo Molnar committed
836
	/* Kernel mode? Handle exceptions or die: */
837 838
	if (!(error_code & PF_USER))
		no_context(regs, error_code, address);
Ingo Molnar's avatar
Ingo Molnar committed
839

840
	/* User-space => ok to do another page fault: */
841 842
	if (is_prefetch(regs, error_code, address))
		return;
Ingo Molnar's avatar
Ingo Molnar committed
843 844 845 846 847

	tsk->thread.cr2		= address;
	tsk->thread.error_code	= error_code;
	tsk->thread.trap_no	= 14;

848 849 850
	force_sig_info_fault(SIGBUS, BUS_ADRERR, address, tsk);
}

Ingo Molnar's avatar
Ingo Molnar committed
851 852 853
static noinline void
mm_fault_error(struct pt_regs *regs, unsigned long error_code,
	       unsigned long address, unsigned int fault)
854
{
Ingo Molnar's avatar
Ingo Molnar committed
855
	if (fault & VM_FAULT_OOM) {
856
		out_of_memory(regs, error_code, address);
Ingo Molnar's avatar
Ingo Molnar committed
857 858 859 860 861 862
	} else {
		if (fault & VM_FAULT_SIGBUS)
			do_sigbus(regs, error_code, address);
		else
			BUG();
	}
863 864
}

865 866 867 868
static int spurious_fault_check(unsigned long error_code, pte_t *pte)
{
	if ((error_code & PF_WRITE) && !pte_write(*pte))
		return 0;
Ingo Molnar's avatar
Ingo Molnar committed
869

870 871 872 873 874 875
	if ((error_code & PF_INSTR) && !pte_exec(*pte))
		return 0;

	return 1;
}

876
/*
Ingo Molnar's avatar
Ingo Molnar committed
877 878 879 880 881 882 883 884
 * Handle a spurious fault caused by a stale TLB entry.
 *
 * This allows us to lazily refresh the TLB when increasing the
 * permissions of a kernel page (RO -> RW or NX -> X).  Doing it
 * eagerly is very expensive since that implies doing a full
 * cross-processor TLB flush, even if no stale TLB entries exist
 * on other processors.
 *
885 886 887
 * There are no security implications to leaving a stale TLB when
 * increasing the permissions on a page.
 */
Ingo Molnar's avatar
Ingo Molnar committed
888 889
static noinline int
spurious_fault(unsigned long error_code, unsigned long address)
890 891 892 893 894
{
	pgd_t *pgd;
	pud_t *pud;
	pmd_t *pmd;
	pte_t *pte;
895
	int ret;
896 897 898 899 900 901 902 903 904 905 906 907 908

	/* Reserved-bit violation or user access to kernel space? */
	if (error_code & (PF_USER | PF_RSVD))
		return 0;

	pgd = init_mm.pgd + pgd_index(address);
	if (!pgd_present(*pgd))
		return 0;

	pud = pud_offset(pgd, address);
	if (!pud_present(*pud))
		return 0;

909 910 911
	if (pud_large(*pud))
		return spurious_fault_check(error_code, (pte_t *) pud);

912 913 914 915
	pmd = pmd_offset(pud, address);
	if (!pmd_present(*pmd))
		return 0;

916 917 918
	if (pmd_large(*pmd))
		return spurious_fault_check(error_code, (pte_t *) pmd);

919 920 921 922
	pte = pte_offset_kernel(pmd, address);
	if (!pte_present(*pte))
		return 0;

923 924 925 926 927
	ret = spurious_fault_check(error_code, pte);
	if (!ret)
		return 0;

	/*
Ingo Molnar's avatar
Ingo Molnar committed
928 929
	 * Make sure we have permissions in PMD.
	 * If not, then there's a bug in the page tables:
930 931 932
	 */
	ret = spurious_fault_check(error_code, (pte_t *) pmd);
	WARN_ONCE(!ret, "PMD has incorrect permission bits\n");
Ingo Molnar's avatar
Ingo Molnar committed
933

934
	return ret;
935 936
}

937
int show_unhandled_signals = 1;
Linus Torvalds's avatar
Linus Torvalds committed
938

Ingo Molnar's avatar
Ingo Molnar committed
939 940
static inline int
access_error(unsigned long error_code, int write, struct vm_area_struct *vma)
941 942
{
	if (write) {
Ingo Molnar's avatar
Ingo Molnar committed
943
		/* write, present and write, not present: */
944 945
		if (unlikely(!(vma->vm_flags & VM_WRITE)))
			return 1;
Ingo Molnar's avatar
Ingo Molnar committed
946
		return 0;
947 948
	}

Ingo Molnar's avatar
Ingo Molnar committed
949 950 951 952 953 954 955 956
	/* read, present: */
	if (unlikely(error_code & PF_PROT))
		return 1;

	/* read, not present: */
	if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))))
		return 1;

957 958 959
	return 0;
}

960 961
static int fault_in_kernel_space(unsigned long address)
{
962
	return address >= TASK_SIZE_MAX;
963 964
}

Linus Torvalds's avatar
Linus Torvalds committed
965 966 967 968 969
/*
 * This routine handles page faults.  It determines the address,
 * and the problem, and then passes it off to one of the appropriate
 * routines.
 */
970 971
dotraplinkage void __kprobes
do_page_fault(struct pt_regs *regs, unsigned long error_code)
Linus Torvalds's avatar
Linus Torvalds committed
972
{
Ingo Molnar's avatar
Ingo Molnar committed
973
	struct vm_area_struct *vma;
Linus Torvalds's avatar
Linus Torvalds committed
974
	struct task_struct *tsk;
Ingo Molnar's avatar
Ingo Molnar committed
975
	unsigned long address;
Linus Torvalds's avatar
Linus Torvalds committed
976
	struct mm_struct *mm;
977
	int write;
978
	int fault;
Linus Torvalds's avatar
Linus Torvalds committed
979

980 981
	tsk = current;
	mm = tsk->mm;
Ingo Molnar's avatar
Ingo Molnar committed
982

983 984
	prefetchw(&mm->mmap_sem);

Ingo Molnar's avatar
Ingo Molnar committed
985
	/* Get the faulting address: */
986
	address = read_cr2();
Linus Torvalds's avatar
Linus Torvalds committed
987

988
	if (unlikely(kmmio_fault(regs, address)))
989
		return;
Linus Torvalds's avatar
Linus Torvalds committed
990 991 992 993 994 995 996 997 998 999 1000 1001

	/*
	 * We fault-in kernel-space virtual memory on-demand. The
	 * 'reference' page table is init_mm.pgd.
	 *
	 * NOTE! We MUST NOT take any locks for this case. We may
	 * be in an interrupt or a critical region, and should
	 * only copy the information from the master page table,
	 * nothing more.
	 *
	 * This verifies that the fault happens in kernel space
	 * (error_code & 4) == 0, and that the fault was not a
1002
	 * protection error (error_code & 9) == 0.
Linus Torvalds's avatar
Linus Torvalds committed
1003
	 */
1004
	if (unlikely(fault_in_kernel_space(address))) {
1005 1006 1007
		if (!(error_code & (PF_RSVD|PF_USER|PF_PROT)) &&
		    vmalloc_fault(address) >= 0)
			return;
1008

Ingo Molnar's avatar
Ingo Molnar committed
1009
		/* Can handle a stale RO->RW TLB: */
1010
		if (spurious_fault(error_code, address))
1011 1012
			return;

Ingo Molnar's avatar
Ingo Molnar committed
1013
		/* kprobes don't want to hook the spurious faults: */
1014 1015
		if (notify_page_fault(regs))
			return;
1016 1017
		/*
		 * Don't take the mm semaphore here. If we fixup a prefetch
Ingo Molnar's avatar
Ingo Molnar committed
1018
		 * fault we could otherwise deadlock:
1019
		 */
1020
		bad_area_nosemaphore(regs, error_code, address);
Ingo Molnar's avatar
Ingo Molnar committed
1021

1022
		return;
1023 1024
	}

Ingo Molnar's avatar
Ingo Molnar committed
1025
	/* kprobes don't want to hook the spurious faults: */
1026
	if (unlikely(notify_page_fault(regs)))
1027
		return;
1028
	/*
1029 1030 1031 1032
	 * It's safe to allow irq's after cr2 has been saved and the
	 * vmalloc fault has been handled.
	 *
	 * User-mode registers count as a user access even for any
Ingo Molnar's avatar
Ingo Molnar committed
1033
	 * potential system fault or CPU buglet:
1034
	 */
1035 1036 1037
	if (user_mode_vm(regs)) {
		local_irq_enable();
		error_code |= PF_USER;
Ingo Molnar's avatar
Ingo Molnar committed
1038 1039 1040 1041
	} else {
		if (regs->flags & X86_EFLAGS_IF)
			local_irq_enable();
	}
1042

1043
	if (unlikely(error_code & PF_RSVD))
1044
		pgtable_bad(regs, error_code, address);
Linus Torvalds's avatar
Linus Torvalds committed
1045 1046

	/*
Ingo Molnar's avatar
Ingo Molnar committed
1047 1048
	 * If we're in an interrupt, have no user context or are running
	 * in an atomic region then we must not take the fault:
Linus Torvalds's avatar
Linus Torvalds committed
1049
	 */
1050 1051 1052 1053
	if (unlikely(in_atomic() || !mm)) {
		bad_area_nosemaphore(regs, error_code, address);
		return;
	}
Linus Torvalds's avatar
Linus Torvalds committed
1054

1055 1056
	/*
	 * When running in the kernel we expect faults to occur only to
Ingo Molnar's avatar
Ingo Molnar committed
1057 1058 1059 1060 1061 1062 1063
	 * addresses in user space.  All other faults represent errors in
	 * the kernel and should generate an OOPS.  Unfortunately, in the
	 * case of an erroneous fault occurring in a code path which already
	 * holds mmap_sem we will deadlock attempting to validate the fault
	 * against the address space.  Luckily the kernel only validly
	 * references user space from well defined areas of code, which are
	 * listed in the exceptions table.
Linus Torvalds's avatar
Linus Torvalds committed
1064 1065
	 *
	 * As the vast majority of faults will be valid we will only perform
Ingo Molnar's avatar
Ingo Molnar committed
1066 1067 1068 1069
	 * the source reference check when there is a possibility of a
	 * deadlock. Attempt to lock the address space, if we cannot we then
	 * validate the source. If this is invalid we can skip the address
	 * space check, thus avoiding the deadlock:
Linus Torvalds's avatar
Linus Torvalds committed
1070
	 */
1071
	if (unlikely(!down_read_trylock(&mm->mmap_sem))) {
1072
		if ((error_code & PF_USER) == 0 &&
1073 1074 1075 1076
		    !search_exception_tables(regs->ip)) {
			bad_area_nosemaphore(regs, error_code, address);
			return;
		}
Linus Torvalds's avatar
Linus Torvalds committed
1077
		down_read(&mm->mmap_sem);
1078 1079
	} else {
		/*
Ingo Molnar's avatar
Ingo Molnar committed
1080 1081 1082
		 * The above down_read_trylock() might have succeeded in
		 * which case we'll have missed the might_sleep() from
		 * down_read():
1083 1084
		 */
		might_sleep();
Linus Torvalds's avatar
Linus Torvalds committed
1085 1086 1087
	}

	vma = find_vma(mm, address);
1088 1089 1090 1091 1092
	if (unlikely(!vma)) {
		bad_area(regs, error_code, address);
		return;
	}
	if (likely(vma->vm_start <= address))
Linus Torvalds's avatar
Linus Torvalds committed
1093
		goto good_area;
1094 1095 1096 1097
	if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
		bad_area(regs, error_code, address);
		return;
	}
1098
	if (error_code & PF_USER) {
1099 1100 1101
		/*
		 * Accessing the stack below %sp is always a bug.
		 * The large cushion allows instructions like enter
Ingo Molnar's avatar
Ingo Molnar committed
1102
		 * and pusha to work. ("enter $65535, $31" pushes
1103
		 * 32 pointers and then decrements %sp by 65535.)
1104
		 */
1105 1106 1107 1108
		if (unlikely(address + 65536 + 32 * sizeof(unsigned long) < regs->sp)) {
			bad_area(regs, error_code, address);
			return;
		}
Linus Torvalds's avatar
Linus Torvalds committed
1109
	}
1110