fault.c 24.4 KB
Newer Older
Linus Torvalds's avatar
Linus Torvalds committed
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
/*
 *  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>
#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
21 22
#include <linux/highmem.h>
#include <linux/bootmem.h>		/* for max_low_pfn */
23
#include <linux/vmalloc.h>
Linus Torvalds's avatar
Linus Torvalds committed
24
#include <linux/module.h>
25
#include <linux/kprobes.h>
26
#include <linux/uaccess.h>
27
#include <linux/kdebug.h>
Linus Torvalds's avatar
Linus Torvalds committed
28 29

#include <asm/system.h>
Harvey Harrison's avatar
Harvey Harrison committed
30 31
#include <asm/desc.h>
#include <asm/segment.h>
Linus Torvalds's avatar
Linus Torvalds committed
32 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 39 40 41 42 43 44 45
/*
 * 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
 */
46
#define PF_PROT		(1<<0)
47
#define PF_WRITE	(1<<1)
48 49
#define PF_USER		(1<<2)
#define PF_RSVD		(1<<3)
50 51
#define PF_INSTR	(1<<4)

52
static inline int notify_page_fault(struct pt_regs *regs)
53
{
54
#ifdef CONFIG_KPROBES
55 56 57
	int ret = 0;

	/* kprobe_running() needs smp_processor_id() */
58 59 60
#ifdef CONFIG_X86_32
	if (!user_mode_vm(regs)) {
#else
61
	if (!user_mode(regs)) {
62
#endif
63 64 65 66 67
		preempt_disable();
		if (kprobe_running() && kprobe_fault_handler(regs, 14))
			ret = 1;
		preempt_enable();
	}
68

69 70 71 72
	return ret;
#else
	return 0;
#endif
73
}
74

75 76 77 78 79 80 81 82 83 84 85 86 87
/*
 * 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)
88
{
89
	unsigned char *instr;
Linus Torvalds's avatar
Linus Torvalds committed
90
	int scan_more = 1;
91
	int prefetch = 0;
92
	unsigned char *max_instr;
Linus Torvalds's avatar
Linus Torvalds committed
93

Ingo Molnar's avatar
Ingo Molnar committed
94 95 96 97
	/*
	 * If it was a exec (instruction fetch) fault on NX page, then
	 * do not ignore the fault:
	 */
98
	if (error_code & PF_INSTR)
Linus Torvalds's avatar
Linus Torvalds committed
99
		return 0;
100

101
	instr = (unsigned char *)convert_ip_to_linear(current, regs);
102
	max_instr = instr + 15;
Linus Torvalds's avatar
Linus Torvalds committed
103

104
	if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE)
Linus Torvalds's avatar
Linus Torvalds committed
105 106
		return 0;

107
	while (scan_more && instr < max_instr) {
Linus Torvalds's avatar
Linus Torvalds committed
108 109 110 111
		unsigned char opcode;
		unsigned char instr_hi;
		unsigned char instr_lo;

112
		if (probe_kernel_address(instr, opcode))
113
			break;
Linus Torvalds's avatar
Linus Torvalds committed
114

115 116
		instr_hi = opcode & 0xf0;
		instr_lo = opcode & 0x0f;
Linus Torvalds's avatar
Linus Torvalds committed
117 118
		instr++;

119
		switch (instr_hi) {
Linus Torvalds's avatar
Linus Torvalds committed
120 121
		case 0x20:
		case 0x30:
122 123 124 125 126 127
			/*
			 * 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
128 129
			scan_more = ((instr_lo & 7) == 0x6);
			break;
130
#ifdef CONFIG_X86_64
Linus Torvalds's avatar
Linus Torvalds committed
131
		case 0x40:
132 133 134 135 136 137 138
			/*
			 * 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.
			 */
139
			scan_more = (!user_mode(regs)) || (regs->cs == __USER_CS);
Linus Torvalds's avatar
Linus Torvalds committed
140
			break;
141
#endif
Linus Torvalds's avatar
Linus Torvalds committed
142 143 144
		case 0x60:
			/* 0x64 thru 0x67 are valid prefixes in all modes. */
			scan_more = (instr_lo & 0xC) == 0x4;
145
			break;
Linus Torvalds's avatar
Linus Torvalds committed
146
		case 0xF0:
147
			/* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */
Linus Torvalds's avatar
Linus Torvalds committed
148
			scan_more = !instr_lo || (instr_lo>>1) == 1;
149
			break;
Linus Torvalds's avatar
Linus Torvalds committed
150 151 152
		case 0x00:
			/* Prefetch instruction is 0x0F0D or 0x0F18 */
			scan_more = 0;
153

154
			if (probe_kernel_address(instr, opcode))
Linus Torvalds's avatar
Linus Torvalds committed
155 156 157
				break;
			prefetch = (instr_lo == 0xF) &&
				(opcode == 0x0D || opcode == 0x18);
158
			break;
Linus Torvalds's avatar
Linus Torvalds committed
159 160 161
		default:
			scan_more = 0;
			break;
162
		}
Linus Torvalds's avatar
Linus Torvalds committed
163 164 165 166
	}
	return prefetch;
}

167 168 169 170 171 172 173 174 175 176 177 178
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);
}

179
#ifdef CONFIG_X86_64
180 181
static int bad_address(void *p)
{
Linus Torvalds's avatar
Linus Torvalds committed
182
	unsigned long dummy;
183
	return probe_kernel_address((unsigned long *)p, dummy);
184
}
185
#endif
Linus Torvalds's avatar
Linus Torvalds committed
186

187
static void dump_pagetable(unsigned long address)
Linus Torvalds's avatar
Linus Torvalds committed
188
{
189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224
#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
225 226 227 228 229
	pgd_t *pgd;
	pud_t *pud;
	pmd_t *pmd;
	pte_t *pte;

230
	pgd = (pgd_t *)read_cr3();
Linus Torvalds's avatar
Linus Torvalds committed
231

232
	pgd = __va((unsigned long)pgd & PHYSICAL_PAGE_MASK);
Linus Torvalds's avatar
Linus Torvalds committed
233 234
	pgd += pgd_index(address);
	if (bad_address(pgd)) goto bad;
235
	printk("PGD %lx ", pgd_val(*pgd));
236
	if (!pgd_present(*pgd)) goto ret;
Linus Torvalds's avatar
Linus Torvalds committed
237

238
	pud = pud_offset(pgd, address);
Linus Torvalds's avatar
Linus Torvalds committed
239 240
	if (bad_address(pud)) goto bad;
	printk("PUD %lx ", pud_val(*pud));
241 242
	if (!pud_present(*pud) || pud_large(*pud))
		goto ret;
Linus Torvalds's avatar
Linus Torvalds committed
243 244 245 246

	pmd = pmd_offset(pud, address);
	if (bad_address(pmd)) goto bad;
	printk("PMD %lx ", pmd_val(*pmd));
247
	if (!pmd_present(*pmd) || pmd_large(*pmd)) goto ret;
Linus Torvalds's avatar
Linus Torvalds committed
248 249 250

	pte = pte_offset_kernel(pmd, address);
	if (bad_address(pte)) goto bad;
251
	printk("PTE %lx", pte_val(*pte));
Linus Torvalds's avatar
Linus Torvalds committed
252 253 254 255 256
ret:
	printk("\n");
	return;
bad:
	printk("BAD\n");
257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294
#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
295
}
296
#endif
Linus Torvalds's avatar
Linus Torvalds committed
297

298
#ifdef CONFIG_X86_64
299
static const char errata93_warning[] =
Linus Torvalds's avatar
Linus Torvalds committed
300 301 302 303
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";
304
#endif
Linus Torvalds's avatar
Linus Torvalds committed
305 306 307

/* Workaround for K8 erratum #93 & buggy BIOS.
   BIOS SMM functions are required to use a specific workaround
308 309
   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
310 311
   The OS sees this as a page fault with the upper 32bits of RIP cleared.
   Try to work around it here.
312 313 314
   Note we only handle faults in kernel here.
   Does nothing for X86_32
 */
315
static int is_errata93(struct pt_regs *regs, unsigned long address)
Linus Torvalds's avatar
Linus Torvalds committed
316
{
317
#ifdef CONFIG_X86_64
Linus Torvalds's avatar
Linus Torvalds committed
318
	static int warned;
319
	if (address != regs->ip)
Linus Torvalds's avatar
Linus Torvalds committed
320
		return 0;
321
	if ((address >> 32) != 0)
Linus Torvalds's avatar
Linus Torvalds committed
322 323
		return 0;
	address |= 0xffffffffUL << 32;
324 325
	if ((address >= (u64)_stext && address <= (u64)_etext) ||
	    (address >= MODULES_VADDR && address <= MODULES_END)) {
Linus Torvalds's avatar
Linus Torvalds committed
326
		if (!warned) {
327
			printk(errata93_warning);
Linus Torvalds's avatar
Linus Torvalds committed
328 329
			warned = 1;
		}
330
		regs->ip = address;
Linus Torvalds's avatar
Linus Torvalds committed
331 332
		return 1;
	}
333
#endif
Linus Torvalds's avatar
Linus Torvalds committed
334
	return 0;
335
}
Linus Torvalds's avatar
Linus Torvalds committed
336

337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352
/*
 * 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;
}

353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373
void do_invalid_op(struct pt_regs *, unsigned long);

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;
}

374 375 376
static void show_fault_oops(struct pt_regs *regs, unsigned long error_code,
			    unsigned long address)
{
377 378 379
#ifdef CONFIG_X86_32
	if (!oops_may_print())
		return;
380
#endif
381 382 383

#ifdef CONFIG_X86_PAE
	if (error_code & PF_INSTR) {
384
		unsigned int level;
385 386 387 388 389 390 391 392 393
		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

394
	printk(KERN_ALERT "BUG: unable to handle kernel ");
395
	if (address < PAGE_SIZE)
396
		printk(KERN_CONT "NULL pointer dereference");
397
	else
398
		printk(KERN_CONT "paging request");
399 400 401
#ifdef CONFIG_X86_32
	printk(KERN_CONT " at %08lx\n", address);
#else
402
	printk(KERN_CONT " at %016lx\n", address);
403
#endif
404
	printk(KERN_ALERT "IP:");
405 406 407 408
	printk_address(regs->ip, 1);
	dump_pagetable(address);
}

409
#ifdef CONFIG_X86_64
Linus Torvalds's avatar
Linus Torvalds committed
410 411 412
static noinline void pgtable_bad(unsigned long address, struct pt_regs *regs,
				 unsigned long error_code)
{
413
	unsigned long flags = oops_begin();
414
	struct task_struct *tsk;
415

Linus Torvalds's avatar
Linus Torvalds committed
416 417 418
	printk(KERN_ALERT "%s: Corrupted page table at address %lx\n",
	       current->comm, address);
	dump_pagetable(address);
419 420 421 422
	tsk = current;
	tsk->thread.cr2 = address;
	tsk->thread.trap_no = 14;
	tsk->thread.error_code = error_code;
423 424 425
	if (__die("Bad pagetable", regs, error_code))
		regs = NULL;
	oops_end(flags, regs, SIGKILL);
Linus Torvalds's avatar
Linus Torvalds committed
426
}
427
#endif
Linus Torvalds's avatar
Linus Torvalds committed
428

429 430 431 432 433 434 435 436 437 438
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;
}

439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467
/*
 * 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;

468 469 470
	if (pud_large(*pud))
		return spurious_fault_check(error_code, (pte_t *) pud);

471 472 473 474
	pmd = pmd_offset(pud, address);
	if (!pmd_present(*pmd))
		return 0;

475 476 477
	if (pmd_large(*pmd))
		return spurious_fault_check(error_code, (pte_t *) pmd);

478 479 480 481
	pte = pte_offset_kernel(pmd, address);
	if (!pte_present(*pte))
		return 0;

482
	return spurious_fault_check(error_code, pte);
483 484
}

Linus Torvalds's avatar
Linus Torvalds committed
485
/*
486 487 488 489
 * X86_32
 * Handle a fault on the vmalloc or module mapping area
 *
 * X86_64
490
 * Handle a fault on the vmalloc area
491 492
 *
 * This assumes no large pages in there.
Linus Torvalds's avatar
Linus Torvalds committed
493 494 495
 */
static int vmalloc_fault(unsigned long address)
{
496 497 498 499
#ifdef CONFIG_X86_32
	unsigned long pgd_paddr;
	pmd_t *pmd_k;
	pte_t *pte_k;
500 501 502 503 504

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

505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520
	/*
	 * 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
521 522 523 524 525
	pgd_t *pgd, *pgd_ref;
	pud_t *pud, *pud_ref;
	pmd_t *pmd, *pmd_ref;
	pte_t *pte, *pte_ref;

526 527 528 529
	/* Make sure we are in vmalloc area */
	if (!(address >= VMALLOC_START && address < VMALLOC_END))
		return -1;

Linus Torvalds's avatar
Linus Torvalds committed
530 531 532 533 534 535 536 537 538 539
	/* 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);
540
	else
541
		BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref));
Linus Torvalds's avatar
Linus Torvalds committed
542 543 544 545 546 547 548 549

	/* 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;
550
	if (pud_none(*pud) || pud_page_vaddr(*pud) != pud_page_vaddr(*pud_ref))
Linus Torvalds's avatar
Linus Torvalds committed
551 552 553 554 555 556 557 558 559 560 561
		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);
562 563 564 565
	/* 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
566 567
		BUG();
	return 0;
568
#endif
Linus Torvalds's avatar
Linus Torvalds committed
569 570
}

571
int show_unhandled_signals = 1;
Linus Torvalds's avatar
Linus Torvalds committed
572 573 574 575 576 577

/*
 * This routine handles page faults.  It determines the address,
 * and the problem, and then passes it off to one of the appropriate
 * routines.
 */
578 579 580 581
#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
582 583 584
{
	struct task_struct *tsk;
	struct mm_struct *mm;
585
	struct vm_area_struct *vma;
Linus Torvalds's avatar
Linus Torvalds committed
586
	unsigned long address;
587 588 589
	int write, si_code;
	int fault;
#ifdef CONFIG_X86_64
590
	unsigned long flags;
591
#endif
Linus Torvalds's avatar
Linus Torvalds committed
592

Peter Zijlstra's avatar
Peter Zijlstra committed
593 594 595 596 597
	/*
	 * We can fault from pretty much anywhere, with unknown IRQ state.
	 */
	trace_hardirqs_fixup();

598 599 600 601
	tsk = current;
	mm = tsk->mm;
	prefetchw(&mm->mmap_sem);

Linus Torvalds's avatar
Linus Torvalds committed
602
	/* get the address */
603
	address = read_cr2();
Linus Torvalds's avatar
Linus Torvalds committed
604

605
	si_code = SEGV_MAPERR;
Linus Torvalds's avatar
Linus Torvalds committed
606

607 608
	if (notify_page_fault(regs))
		return;
Linus Torvalds's avatar
Linus Torvalds committed
609 610 611 612 613 614 615 616 617 618 619 620

	/*
	 * 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
621
	 * protection error (error_code & 9) == 0.
Linus Torvalds's avatar
Linus Torvalds committed
622
	 */
623 624
#ifdef CONFIG_X86_32
	if (unlikely(address >= TASK_SIZE)) {
625 626 627
#else
	if (unlikely(address >= TASK_SIZE64)) {
#endif
628 629 630
		if (!(error_code & (PF_RSVD|PF_USER|PF_PROT)) &&
		    vmalloc_fault(address) >= 0)
			return;
631 632 633 634 635

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

636 637 638 639 640 641 642
		/*
		 * Don't take the mm semaphore here. If we fixup a prefetch
		 * fault we could otherwise deadlock.
		 */
		goto bad_area_nosemaphore;
	}

643 644

#ifdef CONFIG_X86_32
645 646
	/* It's safe to allow irq's after cr2 has been saved and the vmalloc
	   fault has been handled. */
647
	if (regs->flags & (X86_EFLAGS_IF | X86_VM_MASK))
648 649 650 651 652 653 654 655 656
		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 */
657
	if (likely(regs->flags & X86_EFLAGS_IF))
658 659
		local_irq_enable();

660
	if (unlikely(error_code & PF_RSVD))
Linus Torvalds's avatar
Linus Torvalds committed
661 662 663
		pgtable_bad(address, regs, error_code);

	/*
664 665
	 * 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
666 667 668 669
	 */
	if (unlikely(in_atomic() || !mm))
		goto bad_area_nosemaphore;

670 671 672 673 674 675
	/*
	 * 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;
676 677
again:
#endif
Linus Torvalds's avatar
Linus Torvalds committed
678 679
	/* 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
680
	 * kernel and should generate an OOPS.  Unfortunately, in the case of an
681
	 * erroneous fault occurring in a code path which already holds mmap_sem
Linus Torvalds's avatar
Linus Torvalds committed
682 683 684 685 686 687
	 * 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
688
	 * the source reference check when there is a possibility of a deadlock.
Linus Torvalds's avatar
Linus Torvalds committed
689 690 691 692 693
	 * 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)) {
694
		if ((error_code & PF_USER) == 0 &&
695
		    !search_exception_tables(regs->ip))
Linus Torvalds's avatar
Linus Torvalds committed
696 697 698 699 700 701 702
			goto bad_area_nosemaphore;
		down_read(&mm->mmap_sem);
	}

	vma = find_vma(mm, address);
	if (!vma)
		goto bad_area;
703
	if (vma->vm_start <= address)
Linus Torvalds's avatar
Linus Torvalds committed
704 705 706
		goto good_area;
	if (!(vma->vm_flags & VM_GROWSDOWN))
		goto bad_area;
707
	if (error_code & PF_USER) {
708 709 710 711 712
		/*
		 * 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.)
713
		 */
714
		if (address + 65536 + 32 * sizeof(unsigned long) < regs->sp)
Linus Torvalds's avatar
Linus Torvalds committed
715 716 717 718 719 720 721 722 723
			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:
724
	si_code = SEGV_ACCERR;
Linus Torvalds's avatar
Linus Torvalds committed
725
	write = 0;
726
	switch (error_code & (PF_PROT|PF_WRITE)) {
727 728 729 730 731 732 733 734 735 736 737
	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
738 739 740
			goto bad_area;
	}

741 742 743
#ifdef CONFIG_X86_32
survive:
#endif
Linus Torvalds's avatar
Linus Torvalds committed
744 745 746 747 748
	/*
	 * 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
749 750 751 752 753 754 755
	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
756
	}
Nick Piggin's avatar
Nick Piggin committed
757 758 759 760
	if (fault & VM_FAULT_MAJOR)
		tsk->maj_flt++;
	else
		tsk->min_flt++;
761 762 763 764 765 766 767 768 769 770 771

#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
772 773 774 775 776 777 778 779 780 781 782 783
	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 */
784
	if (error_code & PF_USER) {
785 786 787 788 789
		/*
		 * It's possible to have interrupts off here.
		 */
		local_irq_enable();

790 791 792 793
		/*
		 * Valid to do another page fault here because this one came
		 * from user space.
		 */
Linus Torvalds's avatar
Linus Torvalds committed
794 795 796
		if (is_prefetch(regs, address, error_code))
			return;

797
		if (is_errata100(regs, address))
Linus Torvalds's avatar
Linus Torvalds committed
798 799
			return;

800 801
		if (show_unhandled_signals && unhandled_signal(tsk, SIGSEGV) &&
		    printk_ratelimit()) {
Linus Torvalds's avatar
Linus Torvalds committed
802
			printk(
803
#ifdef CONFIG_X86_32
804
			"%s%s[%d]: segfault at %lx ip %08lx sp %08lx error %lx",
805
#else
806
			"%s%s[%d]: segfault at %lx ip %lx sp %lx error %lx",
807 808 809 810
#endif
			task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
			tsk->comm, task_pid_nr(tsk), address, regs->ip,
			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)
{
917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937
#ifdef CONFIG_X86_32
	/*
	 * Note that races in the updates of insync and start aren't
	 * problematic: insync can only get set bits added, and updates to
	 * start are only improving performance (without affecting correctness
	 * if undone).
	 */
	static DECLARE_BITMAP(insync, PTRS_PER_PGD);
	static unsigned long start = TASK_SIZE;
	unsigned long address;

	if (SHARED_KERNEL_PMD)
		return;

	BUILD_BUG_ON(TASK_SIZE & ~PGDIR_MASK);
	for (address = start; address >= TASK_SIZE; address += PGDIR_SIZE) {
		if (!test_bit(pgd_index(address), insync)) {
			unsigned long flags;
			struct page *page;

			spin_lock_irqsave(&pgd_lock, flags);
938
			list_for_each_entry(page, &pgd_list, lru) {
939
				if (!vmalloc_sync_one(page_address(page),
940
						      address))
941
					break;
942
			}
943 944 945 946 947 948 949 950
			spin_unlock_irqrestore(&pgd_lock, flags);
			if (!page)
				set_bit(pgd_index(address), insync);
		}
		if (address == start && test_bit(pgd_index(address), insync))
			start = address + PGDIR_SIZE;
	}
#else /* CONFIG_X86_64 */
951 952 953 954 955 956
	/*
	 * Note that races in the updates of insync and start aren't
	 * problematic: insync can only get set bits added, and updates to
	 * start are only improving performance (without affecting correctness
	 * if undone).
	 */
957 958 959 960 961 962 963
	static DECLARE_BITMAP(insync, PTRS_PER_PGD);
	static unsigned long start = VMALLOC_START & PGDIR_MASK;
	unsigned long address;

	for (address = start; address <= VMALLOC_END; address += PGDIR_SIZE) {
		if (!test_bit(pgd_index(address), insync)) {
			const pgd_t *pgd_ref = pgd_offset_k(address);
964
			unsigned long flags;
965 966 967 968
			struct page *page;

			if (pgd_none(*pgd_ref))
				continue;
969
			spin_lock_irqsave(&pgd_lock, flags);
970
			list_for_each_entry(page, &pgd_list, lru) {
971 972 973 974 975
				pgd_t *pgd;
				pgd = (pgd_t *)page_address(page) + pgd_index(address);
				if (pgd_none(*pgd))
					set_pgd(pgd, *pgd_ref);
				else
976
					BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref));
977
			}
978
			spin_unlock_irqrestore(&pgd_lock, flags);
979 980 981 982 983
			set_bit(pgd_index(address), insync);
		}
		if (address == start)
			start = address + PGDIR_SIZE;
	}
984
#endif
985
}