fault.c 23.5 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

Peter Zijlstra's avatar
Peter Zijlstra committed
595 596 597 598 599
	/*
	 * We can fault from pretty much anywhere, with unknown IRQ state.
	 */
	trace_hardirqs_fixup();

600 601 602 603
	tsk = current;
	mm = tsk->mm;
	prefetchw(&mm->mmap_sem);

Linus Torvalds's avatar
Linus Torvalds committed
604
	/* get the address */
605
	address = read_cr2();
Linus Torvalds's avatar
Linus Torvalds committed
606

607
	si_code = SEGV_MAPERR;
Linus Torvalds's avatar
Linus Torvalds committed
608

609 610
	if (notify_page_fault(regs))
		return;
611
	if (unlikely(kmmio_fault(regs, address)))
612
		return;
Linus Torvalds's avatar
Linus Torvalds committed
613 614 615 616 617 618 619 620 621 622 623 624

	/*
	 * 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
625
	 * protection error (error_code & 9) == 0.
Linus Torvalds's avatar
Linus Torvalds committed
626
	 */
627 628
#ifdef CONFIG_X86_32
	if (unlikely(address >= TASK_SIZE)) {
629 630 631
#else
	if (unlikely(address >= TASK_SIZE64)) {
#endif
632 633 634
		if (!(error_code & (PF_RSVD|PF_USER|PF_PROT)) &&
		    vmalloc_fault(address) >= 0)
			return;
635 636 637 638 639

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

640 641 642 643 644 645 646
		/*
		 * Don't take the mm semaphore here. If we fixup a prefetch
		 * fault we could otherwise deadlock.
		 */
		goto bad_area_nosemaphore;
	}

647 648

#ifdef CONFIG_X86_32
649 650
	/* It's safe to allow irq's after cr2 has been saved and the vmalloc
	   fault has been handled. */
651
	if (regs->flags & (X86_EFLAGS_IF | X86_VM_MASK))
652 653 654 655 656 657 658 659 660
		local_irq_enable();

	/*
	 * If we're in an interrupt, have no user context or are running in an
	 * atomic region then we must not take the fault.
	 */
	if (in_atomic() || !mm)
		goto bad_area_nosemaphore;
#else /* CONFIG_X86_64 */
661
	if (likely(regs->flags & X86_EFLAGS_IF))
662 663
		local_irq_enable();

664
	if (unlikely(error_code & PF_RSVD))
Linus Torvalds's avatar
Linus Torvalds committed
665 666 667
		pgtable_bad(address, regs, error_code);

	/*
668 669
	 * 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
670 671 672 673
	 */
	if (unlikely(in_atomic() || !mm))
		goto bad_area_nosemaphore;

674 675 676 677 678 679
	/*
	 * User-mode registers count as a user access even for any
	 * potential system fault or CPU buglet.
	 */
	if (user_mode_vm(regs))
		error_code |= PF_USER;
680 681
again:
#endif
Linus Torvalds's avatar
Linus Torvalds committed
682 683
	/* When running in the kernel we expect faults to occur only to
	 * addresses in user space.  All other faults represent errors in the
Simon Arlott's avatar
Simon Arlott committed
684
	 * kernel and should generate an OOPS.  Unfortunately, in the case of an
685
	 * erroneous fault occurring in a code path which already holds mmap_sem
Linus Torvalds's avatar
Linus Torvalds committed
686 687 688 689 690 691
	 * 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
692
	 * the source reference check when there is a possibility of a deadlock.
Linus Torvalds's avatar
Linus Torvalds committed
693 694 695 696 697
	 * 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)) {
698
		if ((error_code & PF_USER) == 0 &&
699
		    !search_exception_tables(regs->ip))
Linus Torvalds's avatar
Linus Torvalds committed
700 701 702 703 704 705 706
			goto bad_area_nosemaphore;
		down_read(&mm->mmap_sem);
	}

	vma = find_vma(mm, address);
	if (!vma)
		goto bad_area;
707
	if (vma->vm_start <= address)
Linus Torvalds's avatar
Linus Torvalds committed
708 709 710
		goto good_area;
	if (!(vma->vm_flags & VM_GROWSDOWN))
		goto bad_area;
711
	if (error_code & PF_USER) {
712 713 714 715 716
		/*
		 * 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.)
717
		 */
718
		if (address + 65536 + 32 * sizeof(unsigned long) < regs->sp)
Linus Torvalds's avatar
Linus Torvalds committed
719 720 721 722 723 724 725 726 727
			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:
728
	si_code = SEGV_ACCERR;
Linus Torvalds's avatar
Linus Torvalds committed
729
	write = 0;
730
	switch (error_code & (PF_PROT|PF_WRITE)) {
731 732 733 734 735 736 737 738 739 740 741
	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
742 743 744
			goto bad_area;
	}

745 746 747
#ifdef CONFIG_X86_32
survive:
#endif
Linus Torvalds's avatar
Linus Torvalds committed
748 749 750 751 752
	/*
	 * 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
753 754 755 756 757 758 759
	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
760
	}
Nick Piggin's avatar
Nick Piggin committed
761 762 763 764
	if (fault & VM_FAULT_MAJOR)
		tsk->maj_flt++;
	else
		tsk->min_flt++;
765 766 767 768 769 770 771 772 773 774 775

#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
776 777 778 779 780 781 782 783 784 785 786 787
	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 */
788
	if (error_code & PF_USER) {
789 790 791 792 793
		/*
		 * It's possible to have interrupts off here.
		 */
		local_irq_enable();

794 795 796 797
		/*
		 * Valid to do another page fault here because this one came
		 * from user space.
		 */
Linus Torvalds's avatar
Linus Torvalds committed
798 799 800
		if (is_prefetch(regs, address, error_code))
			return;

801
		if (is_errata100(regs, address))
Linus Torvalds's avatar
Linus Torvalds committed
802 803
			return;

804 805
		if (show_unhandled_signals && unhandled_signal(tsk, SIGSEGV) &&
		    printk_ratelimit()) {
Linus Torvalds's avatar
Linus Torvalds committed
806
			printk(
807
			"%s%s[%d]: segfault at %lx ip %p sp %p error %lx",
808
			task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
809 810
			tsk->comm, task_pid_nr(tsk), address,
			(void *) regs->ip, (void *) regs->sp, error_code);
811 812
			print_vma_addr(" in ", regs->ip);
			printk("\n");
Linus Torvalds's avatar
Linus Torvalds committed
813
		}
814

Linus Torvalds's avatar
Linus Torvalds committed
815 816 817 818
		tsk->thread.cr2 = address;
		/* Kernel addresses are always protection faults */
		tsk->thread.error_code = error_code | (address >= TASK_SIZE);
		tsk->thread.trap_no = 14;
819
		force_sig_info_fault(SIGSEGV, si_code, address, tsk);
Linus Torvalds's avatar
Linus Torvalds committed
820 821 822
		return;
	}

823 824 825
	if (is_f00f_bug(regs, address))
		return;

Linus Torvalds's avatar
Linus Torvalds committed
826 827
no_context:
	/* Are we prepared to handle this kernel fault?  */
828
	if (fixup_exception(regs))
Linus Torvalds's avatar
Linus Torvalds committed
829 830
		return;

831
	/*
832 833 834 835 836 837
	 * 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
838 839
	 * Hall of shame of CPU/BIOS bugs.
	 */
840 841
	if (is_prefetch(regs, address, error_code))
		return;
Linus Torvalds's avatar
Linus Torvalds committed
842 843

	if (is_errata93(regs, address))
844
		return;
Linus Torvalds's avatar
Linus Torvalds committed
845 846 847 848 849

/*
 * Oops. The kernel tried to access some bad page. We'll have to
 * terminate things with extreme prejudice.
 */
850 851
#ifdef CONFIG_X86_32
	bust_spinlocks(1);
852 853 854
#else
	flags = oops_begin();
#endif
855 856

	show_fault_oops(regs, error_code, address);
Linus Torvalds's avatar
Linus Torvalds committed
857

858 859 860
	tsk->thread.cr2 = address;
	tsk->thread.trap_no = 14;
	tsk->thread.error_code = error_code;
861 862

#ifdef CONFIG_X86_32
863 864 865
	die("Oops", regs, error_code);
	bust_spinlocks(0);
	do_exit(SIGKILL);
866
#else
867 868
	if (__die("Oops", regs, error_code))
		regs = NULL;
Linus Torvalds's avatar
Linus Torvalds committed
869 870
	/* Executive summary in case the body of the oops scrolled away */
	printk(KERN_EMERG "CR2: %016lx\n", address);
871
	oops_end(flags, regs, SIGKILL);
872
#endif
Linus Torvalds's avatar
Linus Torvalds committed
873 874 875 876 877 878 879

/*
 * 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);
880 881
	if (is_global_init(tsk)) {
		yield();
882
#ifdef CONFIG_X86_32
883 884 885
		down_read(&mm->mmap_sem);
		goto survive;
#else
Linus Torvalds's avatar
Linus Torvalds committed
886
		goto again;
887
#endif
888 889
	}

Linus Torvalds's avatar
Linus Torvalds committed
890
	printk("VM: killing process %s\n", tsk->comm);
891
	if (error_code & PF_USER)
892
		do_group_exit(SIGKILL);
Linus Torvalds's avatar
Linus Torvalds committed
893 894 895 896 897 898
	goto no_context;

do_sigbus:
	up_read(&mm->mmap_sem);

	/* Kernel mode? Handle exceptions or die */
899
	if (!(error_code & PF_USER))
Linus Torvalds's avatar
Linus Torvalds committed
900
		goto no_context;
901 902 903 904 905
#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
906 907 908
	tsk->thread.cr2 = address;
	tsk->thread.error_code = error_code;
	tsk->thread.trap_no = 14;
909
	force_sig_info_fault(SIGBUS, BUS_ADRERR, address, tsk);
Linus Torvalds's avatar
Linus Torvalds committed
910
}
911

912
DEFINE_SPINLOCK(pgd_lock);
913
LIST_HEAD(pgd_list);
914 915 916

void vmalloc_sync_all(void)
{
917 918
	unsigned long address;

919
#ifdef CONFIG_X86_32
920 921 922
	if (SHARED_KERNEL_PMD)
		return;

923 924 925
	for (address = VMALLOC_START & PMD_MASK;
	     address >= TASK_SIZE && address < FIXADDR_TOP;
	     address += PMD_SIZE) {
926 927 928 929 930 931 932 933
		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;
934
		}
935
		spin_unlock_irqrestore(&pgd_lock, flags);
936 937
	}
#else /* CONFIG_X86_64 */
938 939
	for (address = VMALLOC_START & PGDIR_MASK; address <= VMALLOC_END;
	     address += PGDIR_SIZE) {
940 941 942 943 944 945 946 947 948 949 950 951 952 953
		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));
954
		}
955
		spin_unlock_irqrestore(&pgd_lock, flags);
956
	}
957
#endif
958
}