fault.c 23.1 KB
Newer Older
Linus Torvalds's avatar
Linus Torvalds committed
1
2
3
4
5
6
7
8
9
10
11
12
/*
 *  Copyright (C) 1995  Linus Torvalds
 *  Copyright (C) 2001,2002 Andi Kleen, SuSE Labs.
 */

#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/ptrace.h>
13
#include <linux/mmiotrace.h>
Linus Torvalds's avatar
Linus Torvalds committed
14
15
16
17
18
19
20
21
#include <linux/mman.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/interrupt.h>
#include <linux/init.h>
#include <linux/tty.h>
#include <linux/vt_kern.h>		/* For unblank_screen() */
#include <linux/compiler.h>
Harvey Harrison's avatar
Harvey Harrison committed
22
23
#include <linux/highmem.h>
#include <linux/bootmem.h>		/* for max_low_pfn */
24
#include <linux/vmalloc.h>
Linus Torvalds's avatar
Linus Torvalds committed
25
#include <linux/module.h>
26
#include <linux/kprobes.h>
27
#include <linux/uaccess.h>
28
#include <linux/kdebug.h>
Linus Torvalds's avatar
Linus Torvalds committed
29
30

#include <asm/system.h>
Harvey Harrison's avatar
Harvey Harrison committed
31
32
#include <asm/desc.h>
#include <asm/segment.h>
Linus Torvalds's avatar
Linus Torvalds committed
33
34
35
36
37
#include <asm/pgalloc.h>
#include <asm/smp.h>
#include <asm/tlbflush.h>
#include <asm/proto.h>
#include <asm-generic/sections.h>
38
#include <asm/traps.h>
Linus Torvalds's avatar
Linus Torvalds committed
39

40
41
42
43
44
45
46
47
/*
 * Page fault error code bits
 *	bit 0 == 0 means no page found, 1 means protection fault
 *	bit 1 == 0 means read, 1 means write
 *	bit 2 == 0 means kernel, 1 means user-mode
 *	bit 3 == 1 means use of reserved bit detected
 *	bit 4 == 1 means fault was an instruction fetch
 */
48
#define PF_PROT		(1<<0)
49
#define PF_WRITE	(1<<1)
50
51
#define PF_USER		(1<<2)
#define PF_RSVD		(1<<3)
52
53
#define PF_INSTR	(1<<4)

54
static inline int kmmio_fault(struct pt_regs *regs, unsigned long addr)
55
{
56
#ifdef CONFIG_MMIOTRACE_HOOKS
57
58
59
	if (unlikely(is_kmmio_active()))
		if (kmmio_handler(regs, addr) == 1)
			return -1;
60
#endif
61
	return 0;
62
63
}

64
static inline int notify_page_fault(struct pt_regs *regs)
65
{
66
#ifdef CONFIG_KPROBES
67
68
69
	int ret = 0;

	/* kprobe_running() needs smp_processor_id() */
70
	if (!user_mode_vm(regs)) {
71
72
73
74
75
		preempt_disable();
		if (kprobe_running() && kprobe_fault_handler(regs, 14))
			ret = 1;
		preempt_enable();
	}
76

77
78
79
80
	return ret;
#else
	return 0;
#endif
81
}
82

83
84
85
86
87
88
89
90
91
92
93
94
95
/*
 * X86_32
 * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
 * Check that here and ignore it.
 *
 * X86_64
 * Sometimes the CPU reports invalid exceptions on prefetch.
 * Check that here and ignore it.
 *
 * Opcode checker based on code by Richard Brunner
 */
static int is_prefetch(struct pt_regs *regs, unsigned long addr,
		       unsigned long error_code)
96
{
97
	unsigned char *instr;
Linus Torvalds's avatar
Linus Torvalds committed
98
	int scan_more = 1;
99
	int prefetch = 0;
100
	unsigned char *max_instr;
Linus Torvalds's avatar
Linus Torvalds committed
101

Ingo Molnar's avatar
Ingo Molnar committed
102
103
104
105
	/*
	 * If it was a exec (instruction fetch) fault on NX page, then
	 * do not ignore the fault:
	 */
106
	if (error_code & PF_INSTR)
Linus Torvalds's avatar
Linus Torvalds committed
107
		return 0;
108

109
	instr = (unsigned char *)convert_ip_to_linear(current, regs);
110
	max_instr = instr + 15;
Linus Torvalds's avatar
Linus Torvalds committed
111

112
	if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE)
Linus Torvalds's avatar
Linus Torvalds committed
113
114
		return 0;

115
	while (scan_more && instr < max_instr) {
Linus Torvalds's avatar
Linus Torvalds committed
116
117
118
119
		unsigned char opcode;
		unsigned char instr_hi;
		unsigned char instr_lo;

120
		if (probe_kernel_address(instr, opcode))
121
			break;
Linus Torvalds's avatar
Linus Torvalds committed
122

123
124
		instr_hi = opcode & 0xf0;
		instr_lo = opcode & 0x0f;
Linus Torvalds's avatar
Linus Torvalds committed
125
126
		instr++;

127
		switch (instr_hi) {
Linus Torvalds's avatar
Linus Torvalds committed
128
129
		case 0x20:
		case 0x30:
130
131
132
133
134
135
			/*
			 * 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
			 */
Linus Torvalds's avatar
Linus Torvalds committed
136
137
			scan_more = ((instr_lo & 7) == 0x6);
			break;
138
#ifdef CONFIG_X86_64
Linus Torvalds's avatar
Linus Torvalds committed
139
		case 0x40:
140
141
142
143
144
145
146
			/*
			 * 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.
			 */
147
			scan_more = (!user_mode(regs)) || (regs->cs == __USER_CS);
Linus Torvalds's avatar
Linus Torvalds committed
148
			break;
149
#endif
Linus Torvalds's avatar
Linus Torvalds committed
150
151
152
		case 0x60:
			/* 0x64 thru 0x67 are valid prefixes in all modes. */
			scan_more = (instr_lo & 0xC) == 0x4;
153
			break;
Linus Torvalds's avatar
Linus Torvalds committed
154
		case 0xF0:
155
			/* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */
Linus Torvalds's avatar
Linus Torvalds committed
156
			scan_more = !instr_lo || (instr_lo>>1) == 1;
157
			break;
Linus Torvalds's avatar
Linus Torvalds committed
158
159
160
		case 0x00:
			/* Prefetch instruction is 0x0F0D or 0x0F18 */
			scan_more = 0;
161

162
			if (probe_kernel_address(instr, opcode))
Linus Torvalds's avatar
Linus Torvalds committed
163
164
165
				break;
			prefetch = (instr_lo == 0xF) &&
				(opcode == 0x0D || opcode == 0x18);
166
			break;
Linus Torvalds's avatar
Linus Torvalds committed
167
168
169
		default:
			scan_more = 0;
			break;
170
		}
Linus Torvalds's avatar
Linus Torvalds committed
171
172
173
174
	}
	return prefetch;
}

175
176
177
178
179
180
181
182
183
184
185
186
static void force_sig_info_fault(int si_signo, int si_code,
	unsigned long address, struct task_struct *tsk)
{
	siginfo_t info;

	info.si_signo = si_signo;
	info.si_errno = 0;
	info.si_code = si_code;
	info.si_addr = (void __user *)address;
	force_sig_info(si_signo, &info, tsk);
}

187
#ifdef CONFIG_X86_64
188
189
static int bad_address(void *p)
{
Linus Torvalds's avatar
Linus Torvalds committed
190
	unsigned long dummy;
191
	return probe_kernel_address((unsigned long *)p, dummy);
192
}
193
#endif
Linus Torvalds's avatar
Linus Torvalds committed
194

195
static void dump_pagetable(unsigned long address)
Linus Torvalds's avatar
Linus Torvalds committed
196
{
197
198
199
200
201
202
203
204
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
#ifdef CONFIG_X86_32
	__typeof__(pte_val(__pte(0))) page;

	page = read_cr3();
	page = ((__typeof__(page) *) __va(page))[address >> PGDIR_SHIFT];
#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)
		                                         & (PTRS_PER_PMD - 1)];
		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
	 * it's allocated already.
	 */
	if ((page >> PAGE_SHIFT) < max_low_pfn
	    && (page & _PAGE_PRESENT)
	    && !(page & _PAGE_PSE)) {
		page &= PAGE_MASK;
		page = ((__typeof__(page) *) __va(page))[(address >> PAGE_SHIFT)
		                                         & (PTRS_PER_PTE - 1)];
		printk("*pte = %0*Lx ", sizeof(page)*2, (u64)page);
	}

	printk("\n");
#else /* CONFIG_X86_64 */
Linus Torvalds's avatar
Linus Torvalds committed
233
234
235
236
237
	pgd_t *pgd;
	pud_t *pud;
	pmd_t *pmd;
	pte_t *pte;

238
	pgd = (pgd_t *)read_cr3();
Linus Torvalds's avatar
Linus Torvalds committed
239

240
	pgd = __va((unsigned long)pgd & PHYSICAL_PAGE_MASK);
Linus Torvalds's avatar
Linus Torvalds committed
241
242
	pgd += pgd_index(address);
	if (bad_address(pgd)) goto bad;
243
	printk("PGD %lx ", pgd_val(*pgd));
244
	if (!pgd_present(*pgd)) goto ret;
Linus Torvalds's avatar
Linus Torvalds committed
245

246
	pud = pud_offset(pgd, address);
Linus Torvalds's avatar
Linus Torvalds committed
247
248
	if (bad_address(pud)) goto bad;
	printk("PUD %lx ", pud_val(*pud));
249
250
	if (!pud_present(*pud) || pud_large(*pud))
		goto ret;
Linus Torvalds's avatar
Linus Torvalds committed
251
252
253
254

	pmd = pmd_offset(pud, address);
	if (bad_address(pmd)) goto bad;
	printk("PMD %lx ", pmd_val(*pmd));
255
	if (!pmd_present(*pmd) || pmd_large(*pmd)) goto ret;
Linus Torvalds's avatar
Linus Torvalds committed
256
257
258

	pte = pte_offset_kernel(pmd, address);
	if (bad_address(pte)) goto bad;
259
	printk("PTE %lx", pte_val(*pte));
Linus Torvalds's avatar
Linus Torvalds committed
260
261
262
263
264
ret:
	printk("\n");
	return;
bad:
	printk("BAD\n");
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
#endif
}

#ifdef CONFIG_X86_32
static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
{
	unsigned index = pgd_index(address);
	pgd_t *pgd_k;
	pud_t *pud, *pud_k;
	pmd_t *pmd, *pmd_k;

	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;
Linus Torvalds's avatar
Linus Torvalds committed
303
}
304
#endif
Linus Torvalds's avatar
Linus Torvalds committed
305

306
#ifdef CONFIG_X86_64
307
static const char errata93_warning[] =
Linus Torvalds's avatar
Linus Torvalds committed
308
309
310
311
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";
312
#endif
Linus Torvalds's avatar
Linus Torvalds committed
313
314
315

/* Workaround for K8 erratum #93 & buggy BIOS.
   BIOS SMM functions are required to use a specific workaround
316
317
   to avoid corruption of the 64bit RIP register on C stepping K8.
   A lot of BIOS that didn't get tested properly miss this.
Linus Torvalds's avatar
Linus Torvalds committed
318
319
   The OS sees this as a page fault with the upper 32bits of RIP cleared.
   Try to work around it here.
320
321
322
   Note we only handle faults in kernel here.
   Does nothing for X86_32
 */
323
static int is_errata93(struct pt_regs *regs, unsigned long address)
Linus Torvalds's avatar
Linus Torvalds committed
324
{
325
#ifdef CONFIG_X86_64
Linus Torvalds's avatar
Linus Torvalds committed
326
	static int warned;
327
	if (address != regs->ip)
Linus Torvalds's avatar
Linus Torvalds committed
328
		return 0;
329
	if ((address >> 32) != 0)
Linus Torvalds's avatar
Linus Torvalds committed
330
331
		return 0;
	address |= 0xffffffffUL << 32;
332
333
	if ((address >= (u64)_stext && address <= (u64)_etext) ||
	    (address >= MODULES_VADDR && address <= MODULES_END)) {
Linus Torvalds's avatar
Linus Torvalds committed
334
		if (!warned) {
335
			printk(errata93_warning);
Linus Torvalds's avatar
Linus Torvalds committed
336
337
			warned = 1;
		}
338
		regs->ip = address;
Linus Torvalds's avatar
Linus Torvalds committed
339
340
		return 1;
	}
341
#endif
Linus Torvalds's avatar
Linus Torvalds committed
342
	return 0;
343
}
Linus Torvalds's avatar
Linus Torvalds committed
344

345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
/*
 * 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
 * segment in LDT is compatibility mode.
 */
static int is_errata100(struct pt_regs *regs, unsigned long address)
{
#ifdef CONFIG_X86_64
	if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) &&
	    (address >> 32))
		return 1;
#endif
	return 0;
}

361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
static int is_f00f_bug(struct pt_regs *regs, unsigned long address)
{
#ifdef CONFIG_X86_F00F_BUG
	unsigned long nr;
	/*
	 * Pentium F0 0F C7 C8 bug workaround.
	 */
	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;
}

380
381
382
static void show_fault_oops(struct pt_regs *regs, unsigned long error_code,
			    unsigned long address)
{
383
384
385
#ifdef CONFIG_X86_32
	if (!oops_may_print())
		return;
386
#endif
387
388
389

#ifdef CONFIG_X86_PAE
	if (error_code & PF_INSTR) {
390
		unsigned int level;
391
392
393
394
395
396
397
398
399
		pte_t *pte = lookup_address(address, &level);

		if (pte && pte_present(*pte) && !pte_exec(*pte))
			printk(KERN_CRIT "kernel tried to execute "
				"NX-protected page - exploit attempt? "
				"(uid: %d)\n", current->uid);
	}
#endif

400
	printk(KERN_ALERT "BUG: unable to handle kernel ");
401
	if (address < PAGE_SIZE)
402
		printk(KERN_CONT "NULL pointer dereference");
403
	else
404
		printk(KERN_CONT "paging request");
405
	printk(KERN_CONT " at %p\n", (void *) address);
406
	printk(KERN_ALERT "IP:");
407
408
409
410
	printk_address(regs->ip, 1);
	dump_pagetable(address);
}

411
#ifdef CONFIG_X86_64
Linus Torvalds's avatar
Linus Torvalds committed
412
413
414
static noinline void pgtable_bad(unsigned long address, struct pt_regs *regs,
				 unsigned long error_code)
{
415
	unsigned long flags = oops_begin();
416
	struct task_struct *tsk;
417

Linus Torvalds's avatar
Linus Torvalds committed
418
419
420
	printk(KERN_ALERT "%s: Corrupted page table at address %lx\n",
	       current->comm, address);
	dump_pagetable(address);
421
422
423
424
	tsk = current;
	tsk->thread.cr2 = address;
	tsk->thread.trap_no = 14;
	tsk->thread.error_code = error_code;
425
426
427
	if (__die("Bad pagetable", regs, error_code))
		regs = NULL;
	oops_end(flags, regs, SIGKILL);
Linus Torvalds's avatar
Linus Torvalds committed
428
}
429
#endif
Linus Torvalds's avatar
Linus Torvalds committed
430

431
432
433
434
435
436
437
438
439
440
static int spurious_fault_check(unsigned long error_code, pte_t *pte)
{
	if ((error_code & PF_WRITE) && !pte_write(*pte))
		return 0;
	if ((error_code & PF_INSTR) && !pte_exec(*pte))
		return 0;

	return 1;
}

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
/*
 * 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.
 * There are no security implications to leaving a stale TLB when
 * increasing the permissions on a page.
 */
static int spurious_fault(unsigned long address,
			  unsigned long error_code)
{
	pgd_t *pgd;
	pud_t *pud;
	pmd_t *pmd;
	pte_t *pte;

	/* 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;

470
471
472
	if (pud_large(*pud))
		return spurious_fault_check(error_code, (pte_t *) pud);

473
474
475
476
	pmd = pmd_offset(pud, address);
	if (!pmd_present(*pmd))
		return 0;

477
478
479
	if (pmd_large(*pmd))
		return spurious_fault_check(error_code, (pte_t *) pmd);

480
481
482
483
	pte = pte_offset_kernel(pmd, address);
	if (!pte_present(*pte))
		return 0;

484
	return spurious_fault_check(error_code, pte);
485
486
}

Linus Torvalds's avatar
Linus Torvalds committed
487
/*
488
489
490
491
 * X86_32
 * Handle a fault on the vmalloc or module mapping area
 *
 * X86_64
492
 * Handle a fault on the vmalloc area
493
494
 *
 * This assumes no large pages in there.
Linus Torvalds's avatar
Linus Torvalds committed
495
496
497
 */
static int vmalloc_fault(unsigned long address)
{
498
499
500
501
#ifdef CONFIG_X86_32
	unsigned long pgd_paddr;
	pmd_t *pmd_k;
	pte_t *pte_k;
502
503
504
505
506

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

507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
	/*
	 * 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;
#else
Linus Torvalds's avatar
Linus Torvalds committed
523
524
525
526
527
	pgd_t *pgd, *pgd_ref;
	pud_t *pud, *pud_ref;
	pmd_t *pmd, *pmd_ref;
	pte_t *pte, *pte_ref;

528
529
530
531
	/* Make sure we are in vmalloc area */
	if (!(address >= VMALLOC_START && address < VMALLOC_END))
		return -1;

Linus Torvalds's avatar
Linus Torvalds committed
532
533
534
535
536
537
538
539
540
541
	/* 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->mm ?: &init_mm, address);
	pgd_ref = pgd_offset_k(address);
	if (pgd_none(*pgd_ref))
		return -1;
	if (pgd_none(*pgd))
		set_pgd(pgd, *pgd_ref);
542
	else
543
		BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref));
Linus Torvalds's avatar
Linus Torvalds committed
544
545
546
547
548
549
550
551

	/* 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;
552
	if (pud_none(*pud) || pud_page_vaddr(*pud) != pud_page_vaddr(*pud_ref))
Linus Torvalds's avatar
Linus Torvalds committed
553
554
555
556
557
558
559
560
561
562
563
		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);
564
565
566
567
	/* 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))
Linus Torvalds's avatar
Linus Torvalds committed
568
569
		BUG();
	return 0;
570
#endif
Linus Torvalds's avatar
Linus Torvalds committed
571
572
}

573
int show_unhandled_signals = 1;
Linus Torvalds's avatar
Linus Torvalds committed
574
575
576
577
578
579

/*
 * This routine handles page faults.  It determines the address,
 * and the problem, and then passes it off to one of the appropriate
 * routines.
 */
580
581
582
583
#ifdef CONFIG_X86_64
asmlinkage
#endif
void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
Linus Torvalds's avatar
Linus Torvalds committed
584
585
586
{
	struct task_struct *tsk;
	struct mm_struct *mm;
587
	struct vm_area_struct *vma;
Linus Torvalds's avatar
Linus Torvalds committed
588
	unsigned long address;
589
590
591
	int write, si_code;
	int fault;
#ifdef CONFIG_X86_64
592
	unsigned long flags;
593
#endif
Linus Torvalds's avatar
Linus Torvalds committed
594

595
596
597
598
	tsk = current;
	mm = tsk->mm;
	prefetchw(&mm->mmap_sem);

Linus Torvalds's avatar
Linus Torvalds committed
599
	/* get the address */
600
	address = read_cr2();
Linus Torvalds's avatar
Linus Torvalds committed
601

602
	si_code = SEGV_MAPERR;
Linus Torvalds's avatar
Linus Torvalds committed
603

604
605
	if (notify_page_fault(regs))
		return;
606
	if (unlikely(kmmio_fault(regs, address)))
607
		return;
Linus Torvalds's avatar
Linus Torvalds committed
608
609
610
611
612
613
614
615
616
617
618
619

	/*
	 * 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
620
	 * protection error (error_code & 9) == 0.
Linus Torvalds's avatar
Linus Torvalds committed
621
	 */
622
623
#ifdef CONFIG_X86_32
	if (unlikely(address >= TASK_SIZE)) {
624
625
626
#else
	if (unlikely(address >= TASK_SIZE64)) {
#endif
627
628
629
		if (!(error_code & (PF_RSVD|PF_USER|PF_PROT)) &&
		    vmalloc_fault(address) >= 0)
			return;
630
631
632
633
634

		/* Can handle a stale RO->RW TLB */
		if (spurious_fault(address, error_code))
			return;

635
636
637
638
639
640
641
		/*
		 * Don't take the mm semaphore here. If we fixup a prefetch
		 * fault we could otherwise deadlock.
		 */
		goto bad_area_nosemaphore;
	}

642

643
	/*
644
645
646
647
648
	 * 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
	 * potential system fault or CPU buglet.
649
	 */
650
651
652
653
	if (user_mode_vm(regs)) {
		local_irq_enable();
		error_code |= PF_USER;
	} else if (regs->flags & X86_EFLAGS_IF)
654
655
		local_irq_enable();

656
#ifdef CONFIG_X86_64
657
	if (unlikely(error_code & PF_RSVD))
Linus Torvalds's avatar
Linus Torvalds committed
658
		pgtable_bad(address, regs, error_code);
659
#endif
Linus Torvalds's avatar
Linus Torvalds committed
660
661

	/*
662
663
	 * 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
664
665
666
667
	 */
	if (unlikely(in_atomic() || !mm))
		goto bad_area_nosemaphore;

668
again:
669
670
	/*
	 * When running in the kernel we expect faults to occur only to
Linus Torvalds's avatar
Linus Torvalds committed
671
	 * addresses in user space.  All other faults represent errors in the
Simon Arlott's avatar
Simon Arlott committed
672
	 * kernel and should generate an OOPS.  Unfortunately, in the case of an
673
	 * erroneous fault occurring in a code path which already holds mmap_sem
Linus Torvalds's avatar
Linus Torvalds committed
674
675
676
677
678
679
	 * 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.
	 *
	 * As the vast majority of faults will be valid we will only perform
Simon Arlott's avatar
Simon Arlott committed
680
	 * the source reference check when there is a possibility of a deadlock.
Linus Torvalds's avatar
Linus Torvalds committed
681
682
683
684
685
	 * 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.
	 */
	if (!down_read_trylock(&mm->mmap_sem)) {
686
		if ((error_code & PF_USER) == 0 &&
687
		    !search_exception_tables(regs->ip))
Linus Torvalds's avatar
Linus Torvalds committed
688
689
690
691
692
693
694
			goto bad_area_nosemaphore;
		down_read(&mm->mmap_sem);
	}

	vma = find_vma(mm, address);
	if (!vma)
		goto bad_area;
695
	if (vma->vm_start <= address)
Linus Torvalds's avatar
Linus Torvalds committed
696
697
698
		goto good_area;
	if (!(vma->vm_flags & VM_GROWSDOWN))
		goto bad_area;
699
	if (error_code & PF_USER) {
700
701
702
703
704
		/*
		 * Accessing the stack below %sp is always a bug.
		 * The large cushion allows instructions like enter
		 * and pusha to work.  ("enter $65535,$31" pushes
		 * 32 pointers and then decrements %sp by 65535.)
705
		 */
706
		if (address + 65536 + 32 * sizeof(unsigned long) < regs->sp)
Linus Torvalds's avatar
Linus Torvalds committed
707
708
709
710
711
712
713
714
715
			goto bad_area;
	}
	if (expand_stack(vma, address))
		goto bad_area;
/*
 * Ok, we have a good vm_area for this memory access, so
 * we can handle it..
 */
good_area:
716
	si_code = SEGV_ACCERR;
Linus Torvalds's avatar
Linus Torvalds committed
717
	write = 0;
718
	switch (error_code & (PF_PROT|PF_WRITE)) {
719
720
721
722
723
724
725
726
727
728
729
	default:	/* 3: write, present */
		/* fall through */
	case PF_WRITE:		/* write, not present */
		if (!(vma->vm_flags & VM_WRITE))
			goto bad_area;
		write++;
		break;
	case PF_PROT:		/* read, present */
		goto bad_area;
	case 0:			/* read, not present */
		if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
Linus Torvalds's avatar
Linus Torvalds committed
730
731
732
733
734
735
736
737
			goto bad_area;
	}

	/*
	 * If for any reason at all we couldn't handle the fault,
	 * make sure we exit gracefully rather than endlessly redo
	 * the fault.
	 */
Nick Piggin's avatar
Nick Piggin committed
738
739
740
741
742
743
744
	fault = handle_mm_fault(mm, vma, address, write);
	if (unlikely(fault & VM_FAULT_ERROR)) {
		if (fault & VM_FAULT_OOM)
			goto out_of_memory;
		else if (fault & VM_FAULT_SIGBUS)
			goto do_sigbus;
		BUG();
Linus Torvalds's avatar
Linus Torvalds committed
745
	}
Nick Piggin's avatar
Nick Piggin committed
746
747
748
749
	if (fault & VM_FAULT_MAJOR)
		tsk->maj_flt++;
	else
		tsk->min_flt++;
750
751
752
753
754
755
756
757
758
759
760

#ifdef CONFIG_X86_32
	/*
	 * Did it hit the DOS screen memory VA from vm86 mode?
	 */
	if (v8086_mode(regs)) {
		unsigned long bit = (address - 0xA0000) >> PAGE_SHIFT;
		if (bit < 32)
			tsk->thread.screen_bitmap |= 1 << bit;
	}
#endif
Linus Torvalds's avatar
Linus Torvalds committed
761
762
763
764
765
766
767
768
769
770
771
772
	up_read(&mm->mmap_sem);
	return;

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

bad_area_nosemaphore:
	/* User mode accesses just cause a SIGSEGV */
773
	if (error_code & PF_USER) {
774
775
776
777
778
		/*
		 * It's possible to have interrupts off here.
		 */
		local_irq_enable();

779
780
781
782
		/*
		 * Valid to do another page fault here because this one came
		 * from user space.
		 */
Linus Torvalds's avatar
Linus Torvalds committed
783
784
785
		if (is_prefetch(regs, address, error_code))
			return;

786
		if (is_errata100(regs, address))
Linus Torvalds's avatar
Linus Torvalds committed
787
788
			return;

789
790
		if (show_unhandled_signals && unhandled_signal(tsk, SIGSEGV) &&
		    printk_ratelimit()) {
Linus Torvalds's avatar
Linus Torvalds committed
791
			printk(
792
			"%s%s[%d]: segfault at %lx ip %p sp %p error %lx",
793
			task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
794
795
			tsk->comm, task_pid_nr(tsk), address,
			(void *) regs->ip, (void *) regs->sp, error_code);
796
797
			print_vma_addr(" in ", regs->ip);
			printk("\n");
Linus Torvalds's avatar
Linus Torvalds committed
798
		}
799

Linus Torvalds's avatar
Linus Torvalds committed
800
801
802
803
		tsk->thread.cr2 = address;
		/* Kernel addresses are always protection faults */
		tsk->thread.error_code = error_code | (address >= TASK_SIZE);
		tsk->thread.trap_no = 14;
804
		force_sig_info_fault(SIGSEGV, si_code, address, tsk);
Linus Torvalds's avatar
Linus Torvalds committed
805
806
807
		return;
	}

808
809
810
	if (is_f00f_bug(regs, address))
		return;

Linus Torvalds's avatar
Linus Torvalds committed
811
812
no_context:
	/* Are we prepared to handle this kernel fault?  */
813
	if (fixup_exception(regs))
Linus Torvalds's avatar
Linus Torvalds committed
814
815
		return;

816
	/*
817
818
819
820
821
822
	 * X86_32
	 * Valid to do another page fault here, because if this fault
	 * had been triggered by is_prefetch fixup_exception would have
	 * handled it.
	 *
	 * X86_64
Linus Torvalds's avatar
Linus Torvalds committed
823
824
	 * Hall of shame of CPU/BIOS bugs.
	 */
825
826
	if (is_prefetch(regs, address, error_code))
		return;
Linus Torvalds's avatar
Linus Torvalds committed
827
828

	if (is_errata93(regs, address))
829
		return;
Linus Torvalds's avatar
Linus Torvalds committed
830
831
832
833
834

/*
 * Oops. The kernel tried to access some bad page. We'll have to
 * terminate things with extreme prejudice.
 */
835
836
#ifdef CONFIG_X86_32
	bust_spinlocks(1);
837
838
839
#else
	flags = oops_begin();
#endif
840
841

	show_fault_oops(regs, error_code, address);
Linus Torvalds's avatar
Linus Torvalds committed
842

843
844
845
	tsk->thread.cr2 = address;
	tsk->thread.trap_no = 14;
	tsk->thread.error_code = error_code;
846
847

#ifdef CONFIG_X86_32
848
849
850
	die("Oops", regs, error_code);
	bust_spinlocks(0);
	do_exit(SIGKILL);
851
#else
852
853
	if (__die("Oops", regs, error_code))
		regs = NULL;
Linus Torvalds's avatar
Linus Torvalds committed
854
855
	/* Executive summary in case the body of the oops scrolled away */
	printk(KERN_EMERG "CR2: %016lx\n", address);
856
	oops_end(flags, regs, SIGKILL);
857
#endif
Linus Torvalds's avatar
Linus Torvalds committed
858
859
860
861
862
863
864

/*
 * We ran out of memory, or some other thing happened to us that made
 * us unable to handle the page fault gracefully.
 */
out_of_memory:
	up_read(&mm->mmap_sem);
865
866
	if (is_global_init(tsk)) {
		yield();
867
868
869
870
		/*
		 * Re-lookup the vma - in theory the vma tree might
		 * have changed:
		 */
Linus Torvalds's avatar
Linus Torvalds committed
871
		goto again;
872
873
	}

Linus Torvalds's avatar
Linus Torvalds committed
874
	printk("VM: killing process %s\n", tsk->comm);
875
	if (error_code & PF_USER)
876
		do_group_exit(SIGKILL);
Linus Torvalds's avatar
Linus Torvalds committed
877
878
879
880
881
882
	goto no_context;

do_sigbus:
	up_read(&mm->mmap_sem);

	/* Kernel mode? Handle exceptions or die */
883
	if (!(error_code & PF_USER))
Linus Torvalds's avatar
Linus Torvalds committed
884
		goto no_context;
885
886
887
888
889
#ifdef CONFIG_X86_32
	/* User space => ok to do another page fault */
	if (is_prefetch(regs, address, error_code))
		return;
#endif
Linus Torvalds's avatar
Linus Torvalds committed
890
891
892
	tsk->thread.cr2 = address;
	tsk->thread.error_code = error_code;
	tsk->thread.trap_no = 14;
893
	force_sig_info_fault(SIGBUS, BUS_ADRERR, address, tsk);
Linus Torvalds's avatar
Linus Torvalds committed
894
}
895

896
DEFINE_SPINLOCK(pgd_lock);
897
LIST_HEAD(pgd_list);
898
899
900

void vmalloc_sync_all(void)
{
901
902
	unsigned long address;

903
#ifdef CONFIG_X86_32
904
905
906
	if (SHARED_KERNEL_PMD)
		return;

907
908
909
	for (address = VMALLOC_START & PMD_MASK;
	     address >= TASK_SIZE && address < FIXADDR_TOP;
	     address += PMD_SIZE) {
910
911
912
913
914
915
916
917
		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;
918
		}
919
		spin_unlock_irqrestore(&pgd_lock, flags);
920
921
	}
#else /* CONFIG_X86_64 */
922
923
	for (address = VMALLOC_START & PGDIR_MASK; address <= VMALLOC_END;
	     address += PGDIR_SIZE) {
924
925
926
927
928
929
930
931
932
933
934
935
936
937
		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));
938
		}
939
		spin_unlock_irqrestore(&pgd_lock, flags);
940
	}
941
#endif
942
}