fault.c 31.2 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 7 8 9 10 11 12
#include <linux/magic.h>		/* STACK_END_MAGIC		*/
#include <linux/sched.h>		/* test_thread_flag(), ...	*/
#include <linux/kdebug.h>		/* oops_begin/end, ...		*/
#include <linux/module.h>		/* search_exception_table	*/
#include <linux/bootmem.h>		/* max_low_pfn			*/
#include <linux/kprobes.h>		/* __kprobes, ...		*/
#include <linux/mmiotrace.h>		/* kmmio_handler, ...		*/
13
#include <linux/perf_event.h>		/* perf_sw_event		*/
14
#include <linux/hugetlb.h>		/* hstate_index_to_shift	*/
15
#include <linux/prefetch.h>		/* prefetchw			*/
16
#include <linux/context_tracking.h>	/* exception_enter(), ...	*/
Ingo Molnar's avatar
Ingo Molnar committed
17

18 19
#include <asm/traps.h>			/* dotraplinkage, ...		*/
#include <asm/pgalloc.h>		/* pgd_*(), ...			*/
Vegard Nossum's avatar
Vegard Nossum committed
20
#include <asm/kmemcheck.h>		/* kmemcheck_*(), ...		*/
21 22
#include <asm/fixmap.h>			/* VSYSCALL_ADDR		*/
#include <asm/vsyscall.h>		/* emulate_vsyscall		*/
Linus Torvalds's avatar
Linus Torvalds committed
23

24 25 26
#define CREATE_TRACE_POINTS
#include <asm/trace/exceptions.h>

27
/*
Ingo Molnar's avatar
Ingo Molnar committed
28 29 30 31 32 33 34
 * 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
35
 */
Ingo Molnar's avatar
Ingo Molnar committed
36 37 38 39 40 41 42 43
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,
};
44

45
/*
46 47
 * Returns 0 if mmiotrace is disabled, or if the fault is not
 * handled by mmiotrace:
48
 */
49 50
static inline int __kprobes
kmmio_fault(struct pt_regs *regs, unsigned long addr)
51
{
52 53 54 55
	if (unlikely(is_kmmio_active()))
		if (kmmio_handler(regs, addr) == 1)
			return -1;
	return 0;
56 57
}

58
static inline int __kprobes kprobes_fault(struct pt_regs *regs)
59
{
60 61 62
	int ret = 0;

	/* kprobe_running() needs smp_processor_id() */
63
	if (kprobes_built_in() && !user_mode_vm(regs)) {
64 65 66 67 68
		preempt_disable();
		if (kprobe_running() && kprobe_fault_handler(regs, 14))
			ret = 1;
		preempt_enable();
	}
69

70
	return ret;
71
}
72

73
/*
Ingo Molnar's avatar
Ingo Molnar committed
74 75 76 77 78 79
 * Prefetch quirks:
 *
 * 32-bit mode:
 *
 *   Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
 *   Check that here and ignore it.
80
 *
Ingo Molnar's avatar
Ingo Molnar committed
81
 * 64-bit mode:
82
 *
Ingo Molnar's avatar
Ingo Molnar committed
83 84 85 86
 *   Sometimes the CPU reports invalid exceptions on prefetch.
 *   Check that here and ignore it.
 *
 * Opcode checker based on code by Richard Brunner.
87
 */
88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113
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.
		 */
114
		return (!user_mode(regs) || user_64bit_mode(regs));
115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134
#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
135 136
static int
is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
137
{
Ingo Molnar's avatar
Ingo Molnar committed
138
	unsigned char *max_instr;
139
	unsigned char *instr;
140
	int prefetch = 0;
Linus Torvalds's avatar
Linus Torvalds committed
141

Ingo Molnar's avatar
Ingo Molnar committed
142 143 144 145
	/*
	 * If it was a exec (instruction fetch) fault on NX page, then
	 * do not ignore the fault:
	 */
146
	if (error_code & PF_INSTR)
Linus Torvalds's avatar
Linus Torvalds committed
147
		return 0;
148

149
	instr = (void *)convert_ip_to_linear(current, regs);
150
	max_instr = instr + 15;
Linus Torvalds's avatar
Linus Torvalds committed
151

152
	if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE)
Linus Torvalds's avatar
Linus Torvalds committed
153 154
		return 0;

155
	while (instr < max_instr) {
Ingo Molnar's avatar
Ingo Molnar committed
156
		unsigned char opcode;
Linus Torvalds's avatar
Linus Torvalds committed
157

158
		if (probe_kernel_address(instr, opcode))
159
			break;
Linus Torvalds's avatar
Linus Torvalds committed
160 161 162

		instr++;

163
		if (!check_prefetch_opcode(regs, instr, opcode, &prefetch))
Linus Torvalds's avatar
Linus Torvalds committed
164 165 166 167 168
			break;
	}
	return prefetch;
}

Ingo Molnar's avatar
Ingo Molnar committed
169 170
static void
force_sig_info_fault(int si_signo, int si_code, unsigned long address,
171
		     struct task_struct *tsk, int fault)
172
{
173
	unsigned lsb = 0;
174 175
	siginfo_t info;

Ingo Molnar's avatar
Ingo Molnar committed
176 177 178 179
	info.si_signo	= si_signo;
	info.si_errno	= 0;
	info.si_code	= si_code;
	info.si_addr	= (void __user *)address;
180 181 182 183 184
	if (fault & VM_FAULT_HWPOISON_LARGE)
		lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault)); 
	if (fault & VM_FAULT_HWPOISON)
		lsb = PAGE_SHIFT;
	info.si_addr_lsb = lsb;
Ingo Molnar's avatar
Ingo Molnar committed
185

186 187 188
	force_sig_info(si_signo, &info, tsk);
}

189 190 191 192 193
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)
194
{
195 196 197 198
	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
199

200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220
	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;

221
	if (!pmd_present(*pmd))
222
		set_pmd(pmd, *pmd_k);
223
	else
224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240
		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) {
		struct page *page;

241
		spin_lock(&pgd_lock);
242
		list_for_each_entry(page, &pgd_list, lru) {
243
			spinlock_t *pgt_lock;
244
			pmd_t *ret;
245

246
			/* the pgt_lock only for Xen */
247 248 249 250 251 252 253
			pgt_lock = &pgd_page_get_mm(page)->page_table_lock;

			spin_lock(pgt_lock);
			ret = vmalloc_sync_one(page_address(page), address);
			spin_unlock(pgt_lock);

			if (!ret)
254 255
				break;
		}
256
		spin_unlock(&pgd_lock);
257 258 259 260 261 262 263 264
	}
}

/*
 * 32-bit:
 *
 *   Handle a fault on the vmalloc or module mapping area
 */
265
static noinline __kprobes int vmalloc_fault(unsigned long address)
266 267 268 269 270 271 272 273 274
{
	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;

275 276
	WARN_ON_ONCE(in_nmi());

277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310
	/*
	 * 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;
311
}
Linus Torvalds's avatar
Linus Torvalds committed
312

Akinobu Mita's avatar
Akinobu Mita committed
313
static bool low_pfn(unsigned long pfn)
Linus Torvalds's avatar
Linus Torvalds committed
314
{
Akinobu Mita's avatar
Akinobu Mita committed
315 316
	return pfn < max_low_pfn;
}
317

Akinobu Mita's avatar
Akinobu Mita committed
318 319 320 321 322 323
static void dump_pagetable(unsigned long address)
{
	pgd_t *base = __va(read_cr3());
	pgd_t *pgd = &base[pgd_index(address)];
	pmd_t *pmd;
	pte_t *pte;
Ingo Molnar's avatar
Ingo Molnar committed
324

325
#ifdef CONFIG_X86_PAE
Akinobu Mita's avatar
Akinobu Mita committed
326 327 328
	printk("*pdpt = %016Lx ", pgd_val(*pgd));
	if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd))
		goto out;
329
#endif
Akinobu Mita's avatar
Akinobu Mita committed
330 331
	pmd = pmd_offset(pud_offset(pgd, address), address);
	printk(KERN_CONT "*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd));
332 333 334 335 336

	/*
	 * 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
337
	 * it's allocated already:
338
	 */
Akinobu Mita's avatar
Akinobu Mita committed
339 340
	if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_large(*pmd))
		goto out;
341

Akinobu Mita's avatar
Akinobu Mita committed
342 343 344
	pte = pte_offset_kernel(pmd, address);
	printk("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte));
out:
345
	printk("\n");
346 347 348 349 350 351
}

#else /* CONFIG_X86_64: */

void vmalloc_sync_all(void)
{
352
	sync_global_pgds(VMALLOC_START & PGDIR_MASK, VMALLOC_END);
353 354 355 356 357 358 359 360 361
}

/*
 * 64-bit:
 *
 *   Handle a fault on the vmalloc area
 *
 * This assumes no large pages in there.
 */
362
static noinline __kprobes int vmalloc_fault(unsigned long address)
363 364 365 366 367 368 369 370 371 372
{
	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;

373 374
	WARN_ON_ONCE(in_nmi());

375 376 377 378 379 380 381 382 383 384
	/*
	 * 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;

385
	if (pgd_none(*pgd)) {
386
		set_pgd(pgd, *pgd_ref);
387 388
		arch_flush_lazy_mmu_mode();
	} else {
389
		BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref));
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

	/*
	 * 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;
}

430
#ifdef CONFIG_CPU_SUP_AMD
431
static const char errata93_warning[] =
432 433 434 435 436
KERN_ERR 
"******* Your BIOS seems to not contain a fix for K8 errata #93\n"
"******* Working around it, but it may cause SEGVs or burn power.\n"
"******* Please consider a BIOS update.\n"
"******* Disabling USB legacy in the BIOS may also help.\n";
437
#endif
438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456

/*
 * 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)
{
Akinobu Mita's avatar
Akinobu Mita committed
457 458
	pgd_t *base = __va(read_cr3() & PHYSICAL_PAGE_MASK);
	pgd_t *pgd = base + pgd_index(address);
Linus Torvalds's avatar
Linus Torvalds committed
459 460 461 462
	pud_t *pud;
	pmd_t *pmd;
	pte_t *pte;

Ingo Molnar's avatar
Ingo Molnar committed
463 464 465
	if (bad_address(pgd))
		goto bad;

466
	printk("PGD %lx ", pgd_val(*pgd));
Ingo Molnar's avatar
Ingo Molnar committed
467 468 469

	if (!pgd_present(*pgd))
		goto out;
Linus Torvalds's avatar
Linus Torvalds committed
470

471
	pud = pud_offset(pgd, address);
Ingo Molnar's avatar
Ingo Molnar committed
472 473 474
	if (bad_address(pud))
		goto bad;

Linus Torvalds's avatar
Linus Torvalds committed
475
	printk("PUD %lx ", pud_val(*pud));
476
	if (!pud_present(*pud) || pud_large(*pud))
Ingo Molnar's avatar
Ingo Molnar committed
477
		goto out;
Linus Torvalds's avatar
Linus Torvalds committed
478 479

	pmd = pmd_offset(pud, address);
Ingo Molnar's avatar
Ingo Molnar committed
480 481 482
	if (bad_address(pmd))
		goto bad;

Linus Torvalds's avatar
Linus Torvalds committed
483
	printk("PMD %lx ", pmd_val(*pmd));
Ingo Molnar's avatar
Ingo Molnar committed
484 485
	if (!pmd_present(*pmd) || pmd_large(*pmd))
		goto out;
Linus Torvalds's avatar
Linus Torvalds committed
486 487

	pte = pte_offset_kernel(pmd, address);
Ingo Molnar's avatar
Ingo Molnar committed
488 489 490
	if (bad_address(pte))
		goto bad;

491
	printk("PTE %lx", pte_val(*pte));
Ingo Molnar's avatar
Ingo Molnar committed
492
out:
Linus Torvalds's avatar
Linus Torvalds committed
493 494 495 496
	printk("\n");
	return;
bad:
	printk("BAD\n");
497 498
}

499
#endif /* CONFIG_X86_64 */
Linus Torvalds's avatar
Linus Torvalds committed
500

Ingo Molnar's avatar
Ingo Molnar committed
501 502 503 504 505 506 507 508 509 510 511 512 513
/*
 * 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.
514
 */
515
static int is_errata93(struct pt_regs *regs, unsigned long address)
Linus Torvalds's avatar
Linus Torvalds committed
516
{
517 518 519 520 521
#if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD)
	if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD
	    || boot_cpu_data.x86 != 0xf)
		return 0;

522
	if (address != regs->ip)
Linus Torvalds's avatar
Linus Torvalds committed
523
		return 0;
Ingo Molnar's avatar
Ingo Molnar committed
524

525
	if ((address >> 32) != 0)
Linus Torvalds's avatar
Linus Torvalds committed
526
		return 0;
Ingo Molnar's avatar
Ingo Molnar committed
527

Linus Torvalds's avatar
Linus Torvalds committed
528
	address |= 0xffffffffUL << 32;
529 530
	if ((address >= (u64)_stext && address <= (u64)_etext) ||
	    (address >= MODULES_VADDR && address <= MODULES_END)) {
531
		printk_once(errata93_warning);
532
		regs->ip = address;
Linus Torvalds's avatar
Linus Torvalds committed
533 534
		return 1;
	}
535
#endif
Linus Torvalds's avatar
Linus Torvalds committed
536
	return 0;
537
}
Linus Torvalds's avatar
Linus Torvalds committed
538

539
/*
Ingo Molnar's avatar
Ingo Molnar committed
540 541 542 543 544
 * 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
545 546 547 548 549
 * 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
550
	if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32))
551 552 553 554 555
		return 1;
#endif
	return 0;
}

556 557 558 559
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
560

561
	/*
Ingo Molnar's avatar
Ingo Molnar committed
562
	 * Pentium F0 0F C7 C8 bug workaround:
563
	 */
564
	if (boot_cpu_has_bug(X86_BUG_F00F)) {
565 566 567 568 569 570 571 572 573 574 575
		nr = (address - idt_descr.address) >> 3;

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

576 577 578
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
579 580 581
static void
show_fault_oops(struct pt_regs *regs, unsigned long error_code,
		unsigned long address)
582
{
583 584 585 586
	if (!oops_may_print())
		return;

	if (error_code & PF_INSTR) {
587
		unsigned int level;
588 589
		pgd_t *pgd;
		pte_t *pte;
Ingo Molnar's avatar
Ingo Molnar committed
590

591 592 593 594
		pgd = __va(read_cr3() & PHYSICAL_PAGE_MASK);
		pgd += pgd_index(address);

		pte = lookup_address_in_pgd(pgd, address, &level);
595

596
		if (pte && pte_present(*pte) && !pte_exec(*pte))
597
			printk(nx_warning, from_kuid(&init_user_ns, current_uid()));
598 599
	}

600
	printk(KERN_ALERT "BUG: unable to handle kernel ");
601
	if (address < PAGE_SIZE)
602
		printk(KERN_CONT "NULL pointer dereference");
603
	else
604
		printk(KERN_CONT "paging request");
Ingo Molnar's avatar
Ingo Molnar committed
605

606
	printk(KERN_CONT " at %p\n", (void *) address);
607
	printk(KERN_ALERT "IP:");
608
	printk_address(regs->ip);
Ingo Molnar's avatar
Ingo Molnar committed
609

610 611 612
	dump_pagetable(address);
}

Ingo Molnar's avatar
Ingo Molnar committed
613 614 615
static noinline void
pgtable_bad(struct pt_regs *regs, unsigned long error_code,
	    unsigned long address)
Linus Torvalds's avatar
Linus Torvalds committed
616
{
Ingo Molnar's avatar
Ingo Molnar committed
617 618 619 620 621 622 623
	struct task_struct *tsk;
	unsigned long flags;
	int sig;

	flags = oops_begin();
	tsk = current;
	sig = SIGKILL;
624

Linus Torvalds's avatar
Linus Torvalds committed
625
	printk(KERN_ALERT "%s: Corrupted page table at address %lx\n",
626
	       tsk->comm, address);
Linus Torvalds's avatar
Linus Torvalds committed
627
	dump_pagetable(address);
Ingo Molnar's avatar
Ingo Molnar committed
628 629

	tsk->thread.cr2		= address;
630
	tsk->thread.trap_nr	= X86_TRAP_PF;
Ingo Molnar's avatar
Ingo Molnar committed
631 632
	tsk->thread.error_code	= error_code;

633
	if (__die("Bad pagetable", regs, error_code))
634
		sig = 0;
Ingo Molnar's avatar
Ingo Molnar committed
635

636
	oops_end(flags, regs, sig);
Linus Torvalds's avatar
Linus Torvalds committed
637 638
}

Ingo Molnar's avatar
Ingo Molnar committed
639 640
static noinline void
no_context(struct pt_regs *regs, unsigned long error_code,
641
	   unsigned long address, int signal, int si_code)
642 643
{
	struct task_struct *tsk = current;
644
	unsigned long *stackend;
645 646 647
	unsigned long flags;
	int sig;

Ingo Molnar's avatar
Ingo Molnar committed
648
	/* Are we prepared to handle this kernel fault? */
649
	if (fixup_exception(regs)) {
650 651 652 653 654 655 656 657 658 659 660 661 662 663
		/*
		 * Any interrupt that takes a fault gets the fixup. This makes
		 * the below recursive fault logic only apply to a faults from
		 * task context.
		 */
		if (in_interrupt())
			return;

		/*
		 * Per the above we're !in_interrupt(), aka. task context.
		 *
		 * In this case we need to make sure we're not recursively
		 * faulting through the emulate_vsyscall() logic.
		 */
664
		if (current_thread_info()->sig_on_uaccess_error && signal) {
665
			tsk->thread.trap_nr = X86_TRAP_PF;
666 667 668 669 670 671
			tsk->thread.error_code = error_code | PF_USER;
			tsk->thread.cr2 = address;

			/* XXX: hwpoison faults will set the wrong code. */
			force_sig_info_fault(signal, si_code, address, tsk, 0);
		}
672 673 674 675

		/*
		 * Barring that, we can do the fixup and be happy.
		 */
676
		return;
677
	}
678 679

	/*
Ingo Molnar's avatar
Ingo Molnar committed
680 681 682 683 684 685 686
	 * 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:
687
	 *
Ingo Molnar's avatar
Ingo Molnar committed
688
	 *   Hall of shame of CPU/BIOS bugs.
689 690 691 692 693 694 695 696 697
	 */
	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
698
	 * terminate things with extreme prejudice:
699 700 701 702 703
	 */
	flags = oops_begin();

	show_fault_oops(regs, error_code, address);

Ingo Molnar's avatar
Ingo Molnar committed
704
	stackend = end_of_stack(tsk);
705
	if (tsk != &init_task && *stackend != STACK_END_MAGIC)
706
		printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");
707

708
	tsk->thread.cr2		= address;
709
	tsk->thread.trap_nr	= X86_TRAP_PF;
710
	tsk->thread.error_code	= error_code;
711 712 713 714

	sig = SIGKILL;
	if (__die("Oops", regs, error_code))
		sig = 0;
Ingo Molnar's avatar
Ingo Molnar committed
715

716
	/* Executive summary in case the body of the oops scrolled away */
717
	printk(KERN_DEFAULT "CR2: %016lx\n", address);
Ingo Molnar's avatar
Ingo Molnar committed
718

719 720 721
	oops_end(flags, regs, sig);
}

Ingo Molnar's avatar
Ingo Molnar committed
722 723 724 725 726 727 728 729 730 731 732 733 734 735
/*
 * 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;

736
	printk("%s%s[%d]: segfault at %lx ip %p sp %p error %lx",
Ingo Molnar's avatar
Ingo Molnar committed
737 738 739 740 741 742 743 744 745 746 747 748
		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)
749 750 751 752 753 754
{
	struct task_struct *tsk = current;

	/* User mode accesses just cause a SIGSEGV */
	if (error_code & PF_USER) {
		/*
Ingo Molnar's avatar
Ingo Molnar committed
755
		 * It's possible to have interrupts off here:
756 757 758 759 760
		 */
		local_irq_enable();

		/*
		 * Valid to do another page fault here because this one came
Ingo Molnar's avatar
Ingo Molnar committed
761
		 * from user space:
762 763 764 765 766 767 768
		 */
		if (is_prefetch(regs, error_code, address))
			return;

		if (is_errata100(regs, address))
			return;

769 770 771 772 773 774
#ifdef CONFIG_X86_64
		/*
		 * Instruction fetch faults in the vsyscall page might need
		 * emulation.
		 */
		if (unlikely((error_code & PF_INSTR) &&
775
			     ((address & ~0xfff) == VSYSCALL_ADDR))) {
776 777 778 779
			if (emulate_vsyscall(regs, address))
				return;
		}
#endif
780 781 782
		/* Kernel addresses are always protection faults: */
		if (address >= TASK_SIZE)
			error_code |= PF_PROT;
783

784
		if (likely(show_unhandled_signals))
Ingo Molnar's avatar
Ingo Molnar committed
785 786 787
			show_signal_msg(regs, error_code, address, tsk);

		tsk->thread.cr2		= address;
788
		tsk->thread.error_code	= error_code;
789
		tsk->thread.trap_nr	= X86_TRAP_PF;
790

791
		force_sig_info_fault(SIGSEGV, si_code, address, tsk, 0);
Ingo Molnar's avatar
Ingo Molnar committed
792

793 794 795 796 797 798
		return;
	}

	if (is_f00f_bug(regs, address))
		return;

799
	no_context(regs, error_code, address, SIGSEGV, si_code);
800 801
}

Ingo Molnar's avatar
Ingo Molnar committed
802 803 804
static noinline void
bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
		     unsigned long address)
805 806 807 808
{
	__bad_area_nosemaphore(regs, error_code, address, SEGV_MAPERR);
}

Ingo Molnar's avatar
Ingo Molnar committed
809 810 811
static void
__bad_area(struct pt_regs *regs, unsigned long error_code,
	   unsigned long address, int si_code)
812 813 814 815 816 817 818 819 820 821 822 823
{
	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
824 825
static noinline void
bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address)
826 827 828 829
{
	__bad_area(regs, error_code, address, SEGV_MAPERR);
}

Ingo Molnar's avatar
Ingo Molnar committed
830 831 832
static noinline void
bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
		      unsigned long address)
833 834 835 836
{
	__bad_area(regs, error_code, address, SEGV_ACCERR);
}

Ingo Molnar's avatar
Ingo Molnar committed
837
static void
838 839
do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
	  unsigned int fault)
840 841 842
{
	struct task_struct *tsk = current;
	struct mm_struct *mm = tsk->mm;
843
	int code = BUS_ADRERR;
844 845 846

	up_read(&mm->mmap_sem);

Ingo Molnar's avatar
Ingo Molnar committed
847
	/* Kernel mode? Handle exceptions or die: */
848
	if (!(error_code & PF_USER)) {
849
		no_context(regs, error_code, address, SIGBUS, BUS_ADRERR);
850 851
		return;
	}
Ingo Molnar's avatar
Ingo Molnar committed
852

853
	/* User-space => ok to do another page fault: */
854 855
	if (is_prefetch(regs, error_code, address))
		return;
Ingo Molnar's avatar
Ingo Molnar committed
856 857 858

	tsk->thread.cr2		= address;
	tsk->thread.error_code	= error_code;
859
	tsk->thread.trap_nr	= X86_TRAP_PF;
Ingo Molnar's avatar
Ingo Molnar committed
860

861
#ifdef CONFIG_MEMORY_FAILURE
862
	if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
863 864 865 866 867 868
		printk(KERN_ERR
	"MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
			tsk->comm, tsk->pid, address);
		code = BUS_MCEERR_AR;
	}
#endif
869
	force_sig_info_fault(SIGBUS, code, address, tsk, fault);
870 871
}

872
static noinline void
Ingo Molnar's avatar
Ingo Molnar committed
873 874
mm_fault_error(struct pt_regs *regs, unsigned long error_code,
	       unsigned long address, unsigned int fault)
875
{
876 877 878 879
	if (fatal_signal_pending(current) && !(error_code & PF_USER)) {
		up_read(&current->mm->mmap_sem);
		no_context(regs, error_code, address, 0, 0);
		return;
880 881
	}

Ingo Molnar's avatar
Ingo Molnar committed
882
	if (fault & VM_FAULT_OOM) {
883 884 885
		/* Kernel mode? Handle exceptions or die: */
		if (!(error_code & PF_USER)) {
			up_read(&current->mm->mmap_sem);
886 887
			no_context(regs, error_code, address,
				   SIGSEGV, SEGV_MAPERR);
888
			return;
889 890
		}

891 892 893 894 895 896 897 898
		up_read(&current->mm->mmap_sem);

		/*
		 * We ran out of memory, call the OOM killer, and return the
		 * userspace (which will retry the fault, or kill us if we got
		 * oom-killed):
		 */
		pagefault_out_of_memory();
Ingo Molnar's avatar
Ingo Molnar committed
899
	} else {
900 901
		if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
			     VM_FAULT_HWPOISON_LARGE))
902
			do_sigbus(regs, error_code, address, fault);
Ingo Molnar's avatar
Ingo Molnar committed
903 904 905
		else
			BUG();
	}
906 907
}

908 909 910 911
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
912

913 914 915 916 917 918
	if ((error_code & PF_INSTR) && !pte_exec(*pte))
		return 0;

	return 1;
}

919
/*
Ingo Molnar's avatar
Ingo Molnar committed
920 921 922 923 924 925 926 927
 * 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.
 *
928 929 930
 * There are no security implications to leaving a stale TLB when
 * increasing the permissions on a page.
 */
931
static noinline __kprobes int
Ingo Molnar's avatar
Ingo Molnar committed
932
spurious_fault(unsigned long error_code, unsigned long address)
933 934 935 936 937
{
	pgd_t *pgd;
	pud_t *pud;
	pmd_t *pmd;
	pte_t *pte;
938
	int ret;
939 940 941 942 943 944 945 946 947 948 949 950 951

	/* 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;

952 953 954
	if (pud_large(*pud))
		return spurious_fault_check(error_code, (pte_t *) pud);

955 956 957 958
	pmd = pmd_offset(pud, address);
	if (!pmd_present(*pmd))
		return 0;

959 960 961
	if (pmd_large(*pmd))
		return spurious_fault_check(error_code, (pte_t *) pmd);

962
	pte = pte_offset_kernel(pmd, address);
963
	if (!pte_present(*pte))
964 965
		return 0;

966 967 968 969 970
	ret = spurious_fault_check(error_code, pte);
	if (!ret)
		return 0;

	/*
Ingo Molnar's avatar
Ingo Molnar committed
971 972
	 * Make sure we have permissions in PMD.
	 * If not, then there's a bug in the page tables:
973 974 975
	 */
	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
976

977
	return ret;
978 979
}

980
int show_unhandled_signals = 1;
Linus Torvalds's avatar
Linus Torvalds committed
981

Ingo Molnar's avatar
Ingo Molnar committed
982
static inline int
983
access_error(unsigned long error_code, struct vm_area_struct *vma)
984
{
985
	if (error_code & PF_WRITE) {
Ingo Molnar's avatar
Ingo Molnar committed
986
		/* write, present and write, not present: */
987 988
		if (unlikely(!(vma->vm_flags & VM_WRITE)))
			return 1;
Ingo Molnar's avatar
Ingo Molnar committed
989
		return 0;
990 991
	}

Ingo Molnar's avatar
Ingo Molnar committed
992 993 994 995 996 997 998 999
	/* 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;

1000 1001 1002
	return 0;
}

1003 1004
static int fault_in_kernel_space(unsigned long address)
{
1005
	return address >= TASK_SIZE_MAX;
1006 1007
}

1008 1009
static inline bool smap_violation(int error_code, struct pt_regs *regs)
{
1010 1011 1012 1013 1014 1015
	if (!IS_ENABLED(CONFIG_X86_SMAP))
		return false;

	if (!static_cpu_has(X86_FEATURE_SMAP))
		return false;

1016 1017 1018 1019 1020 1021 1022