summaryrefslogtreecommitdiffstats
path: root/arch/x86/kernel/head_64.S
blob: 22fbf9df61bb4eecbb5ffe530562b56c1def90b8 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
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
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
/*
 *  linux/arch/x86/kernel/head_64.S -- start in 32bit and switch to 64bit
 *
 *  Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE
 *  Copyright (C) 2000 Pavel Machek <pavel@suse.cz>
 *  Copyright (C) 2000 Karsten Keil <kkeil@suse.de>
 *  Copyright (C) 2001,2002 Andi Kleen <ak@suse.de>
 *  Copyright (C) 2005 Eric Biederman <ebiederm@xmission.com>
 */


#include <linux/linkage.h>
#include <linux/threads.h>
#include <linux/init.h>
#include <asm/segment.h>
#include <asm/pgtable.h>
#include <asm/page.h>
#include <asm/msr.h>
#include <asm/cache.h>
#include <asm/processor-flags.h>
#include <asm/percpu.h>
#include <asm/nops.h>

#ifdef CONFIG_PARAVIRT
#include <asm/asm-offsets.h>
#include <asm/paravirt.h>
#define GET_CR2_INTO(reg) GET_CR2_INTO_RAX ; movq %rax, reg
#else
#define GET_CR2_INTO(reg) movq %cr2, reg
#define INTERRUPT_RETURN iretq
#endif

/* we are not able to switch in one step to the final KERNEL ADDRESS SPACE
 * because we need identity-mapped pages.
 *
 */

#define pud_index(x)	(((x) >> PUD_SHIFT) & (PTRS_PER_PUD-1))

L4_PAGE_OFFSET = pgd_index(__PAGE_OFFSET)
L4_START_KERNEL = pgd_index(__START_KERNEL_map)
L3_START_KERNEL = pud_index(__START_KERNEL_map)

	.text
	__HEAD
	.code64
	.globl startup_64
startup_64:
	/*
	 * At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 0,
	 * and someone has loaded an identity mapped page table
	 * for us.  These identity mapped page tables map all of the
	 * kernel pages and possibly all of memory.
	 *
	 * %rsi holds a physical pointer to real_mode_data.
	 *
	 * We come here either directly from a 64bit bootloader, or from
	 * arch/x86/boot/compressed/head_64.S.
	 *
	 * We only come here initially at boot nothing else comes here.
	 *
	 * Since we may be loaded at an address different from what we were
	 * compiled to run at we first fixup the physical addresses in our page
	 * tables and then reload them.
	 */

	/* Sanitize CPU configuration */
	call verify_cpu

	/*
	 * Compute the delta between the address I am compiled to run at and the
	 * address I am actually running at.
	 */
	leaq	_text(%rip), %rbp
	subq	$_text - __START_KERNEL_map, %rbp

	/* Is the address not 2M aligned? */
	testl	$~PMD_PAGE_MASK, %ebp
	jnz	bad_address

	/*
	 * Is the address too large?
	 */
	leaq	_text(%rip), %rax
	shrq	$MAX_PHYSMEM_BITS, %rax
	jnz	bad_address

	/*
	 * Fixup the physical addresses in the page table
	 */
	addq	%rbp, early_level4_pgt + (L4_START_KERNEL*8)(%rip)

	addq	%rbp, level3_kernel_pgt + (510*8)(%rip)
	addq	%rbp, level3_kernel_pgt + (511*8)(%rip)

	addq	%rbp, level2_fixmap_pgt + (506*8)(%rip)

	/*
	 * Set up the identity mapping for the switchover.  These
	 * entries should *NOT* have the global bit set!  This also
	 * creates a bunch of nonsense entries but that is fine --
	 * it avoids problems around wraparound.
	 */
	leaq	_text(%rip), %rdi
	leaq	early_level4_pgt(%rip), %rbx

	movq	%rdi, %rax
	shrq	$PGDIR_SHIFT, %rax

	leaq	(4096 + _KERNPG_TABLE)(%rbx), %rdx
	movq	%rdx, 0(%rbx,%rax,8)
	movq	%rdx, 8(%rbx,%rax,8)

	addq	$4096, %rdx
	movq	%rdi, %rax
	shrq	$PUD_SHIFT, %rax
	andl	$(PTRS_PER_PUD-1), %eax
	movq	%rdx, 4096(%rbx,%rax,8)
	incl	%eax
	andl	$(PTRS_PER_PUD-1), %eax
	movq	%rdx, 4096(%rbx,%rax,8)

	addq	$8192, %rbx
	movq	%rdi, %rax
	shrq	$PMD_SHIFT, %rdi
	addq	$(__PAGE_KERNEL_LARGE_EXEC & ~_PAGE_GLOBAL), %rax
	leaq	(_end - 1)(%rip), %rcx
	shrq	$PMD_SHIFT, %rcx
	subq	%rdi, %rcx
	incl	%ecx

1:
	andq	$(PTRS_PER_PMD - 1), %rdi
	movq	%rax, (%rbx,%rdi,8)
	incq	%rdi
	addq	$PMD_SIZE, %rax
	decl	%ecx
	jnz	1b

	/*
	 * Fixup the kernel text+data virtual addresses. Note that
	 * we might write invalid pmds, when the kernel is relocated
	 * cleanup_highmap() fixes this up along with the mappings
	 * beyond _end.
	 */
	leaq	level2_kernel_pgt(%rip), %rdi
	leaq	4096(%rdi), %r8
	/* See if it is a valid page table entry */
1:	testb	$1, 0(%rdi)
	jz	2f
	addq	%rbp, 0(%rdi)
	/* Go to the next page */
2:	addq	$8, %rdi
	cmp	%r8, %rdi
	jne	1b

	/* Fixup phys_base */
	addq	%rbp, phys_base(%rip)

	movq	$(early_level4_pgt - __START_KERNEL_map), %rax
	jmp 1f
ENTRY(secondary_startup_64)
	/*
	 * At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 0,
	 * and someone has loaded a mapped page table.
	 *
	 * %rsi holds a physical pointer to real_mode_data.
	 *
	 * We come here either from startup_64 (using physical addresses)
	 * or from trampoline.S (using virtual addresses).
	 *
	 * Using virtual addresses from trampoline.S removes the need
	 * to have any identity mapped pages in the kernel page table
	 * after the boot processor executes this code.
	 */

	/* Sanitize CPU configuration */
	call verify_cpu

	movq	$(init_level4_pgt - __START_KERNEL_map), %rax
1:

	/* Enable PAE mode and PGE */
	movl	$(X86_CR4_PAE | X86_CR4_PGE), %ecx
	movq	%rcx, %cr4

	/* Setup early boot stage 4 level pagetables. */
	addq	phys_base(%rip), %rax
	movq	%rax, %cr3

	/* Ensure I am executing from virtual addresses */
	movq	$1f, %rax
	jmp	*%rax
1:

	/* Check if nx is implemented */
	movl	$0x80000001, %eax
	cpuid
	movl	%edx,%edi

	/* Setup EFER (Extended Feature Enable Register) */
	movl	$MSR_EFER, %ecx
	rdmsr
	btsl	$_EFER_SCE, %eax	/* Enable System Call */
	btl	$20,%edi		/* No Execute supported? */
	jnc     1f
	btsl	$_EFER_NX, %eax
	btsq	$_PAGE_BIT_NX,early_pmd_flags(%rip)
1:	wrmsr				/* Make changes effective */

	/* Setup cr0 */
#define CR0_STATE	(X86_CR0_PE | X86_CR0_MP | X86_CR0_ET | \
			 X86_CR0_NE | X86_CR0_WP | X86_CR0_AM | \
			 X86_CR0_PG)
	movl	$CR0_STATE, %eax
	/* Make changes effective */
	movq	%rax, %cr0

	/* Setup a boot time stack */
	movq stack_start(%rip), %rsp

	/* zero EFLAGS after setting rsp */
	pushq $0
	popfq

	/*
	 * We must switch to a new descriptor in kernel space for the GDT
	 * because soon the kernel won't have access anymore to the userspace
	 * addresses where we're currently running on. We have to do that here
	 * because in 32bit we couldn't load a 64bit linear address.
	 */
	lgdt	early_gdt_descr(%rip)

	/* set up data segments */
	xorl %eax,%eax
	movl %eax,%ds
	movl %eax,%ss
	movl %eax,%es

	/*
	 * We don't really need to load %fs or %gs, but load them anyway
	 * to kill any stale realmode selectors.  This allows execution
	 * under VT hardware.
	 */
	movl %eax,%fs
	movl %eax,%gs

	/* Set up %gs.
	 *
	 * The base of %gs always points to the bottom of the irqstack
	 * union.  If the stack protector canary is enabled, it is
	 * located at %gs:40.  Note that, on SMP, the boot cpu uses
	 * init data section till per cpu areas are set up.
	 */
	movl	$MSR_GS_BASE,%ecx
	movl	initial_gs(%rip),%eax
	movl	initial_gs+4(%rip),%edx
	wrmsr	

	/* rsi is pointer to real mode structure with interesting info.
	   pass it to C */
	movq	%rsi, %rdi
	
	/* Finally jump to run C code and to be on real kernel address
	 * Since we are running on identity-mapped space we have to jump
	 * to the full 64bit address, this is only possible as indirect
	 * jump.  In addition we need to ensure %cs is set so we make this
	 * a far return.
	 *
	 * Note: do not change to far jump indirect with 64bit offset.
	 *
	 * AMD does not support far jump indirect with 64bit offset.
	 * AMD64 Architecture Programmer's Manual, Volume 3: states only
	 *	JMP FAR mem16:16 FF /5 Far jump indirect,
	 *		with the target specified by a far pointer in memory.
	 *	JMP FAR mem16:32 FF /5 Far jump indirect,
	 *		with the target specified by a far pointer in memory.
	 *
	 * Intel64 does support 64bit offset.
	 * Software Developer Manual Vol 2: states:
	 *	FF /5 JMP m16:16 Jump far, absolute indirect,
	 *		address given in m16:16
	 *	FF /5 JMP m16:32 Jump far, absolute indirect,
	 *		address given in m16:32.
	 *	REX.W + FF /5 JMP m16:64 Jump far, absolute indirect,
	 *		address given in m16:64.
	 */
	movq	initial_code(%rip),%rax
	pushq	$0		# fake return address to stop unwinder
	pushq	$__KERNEL_CS	# set correct cs
	pushq	%rax		# target address in negative space
	lretq

#include "verify_cpu.S"

#ifdef CONFIG_HOTPLUG_CPU
/*
 * Boot CPU0 entry point. It's called from play_dead(). Everything has been set
 * up already except stack. We just set up stack here. Then call
 * start_secondary().
 */
ENTRY(start_cpu0)
	movq stack_start(%rip),%rsp
	movq	initial_code(%rip),%rax
	pushq	$0		# fake return address to stop unwinder
	pushq	$__KERNEL_CS	# set correct cs
	pushq	%rax		# target address in negative space
	lretq
ENDPROC(start_cpu0)
#endif

	/* SMP bootup changes these two */
	__REFDATA
	.balign	8
	GLOBAL(initial_code)
	.quad	x86_64_start_kernel
	GLOBAL(initial_gs)
	.quad	INIT_PER_CPU_VAR(irq_stack_union)

	GLOBAL(stack_start)
	.quad  init_thread_union+THREAD_SIZE-8
	.word  0
	__FINITDATA

bad_address:
	jmp bad_address

	__INIT
ENTRY(early_idt_handler_array)
	# 104(%rsp) %rflags
	#  96(%rsp) %cs
	#  88(%rsp) %rip
	#  80(%rsp) error code
	i = 0
	.rept NUM_EXCEPTION_VECTORS
	.ifeq (EXCEPTION_ERRCODE_MASK >> i) & 1
	pushq $0		# Dummy error code, to make stack frame uniform
	.endif
	pushq $i		# 72(%rsp) Vector number
	jmp early_idt_handler_common
	i = i + 1
	.fill early_idt_handler_array + i*EARLY_IDT_HANDLER_SIZE - ., 1, 0xcc
	.endr
ENDPROC(early_idt_handler_array)

early_idt_handler_common:
	/*
	 * The stack is the hardware frame, an error code or zero, and the
	 * vector number.
	 */
	cld

	cmpl $2,(%rsp)		# X86_TRAP_NMI
	je .Lis_nmi		# Ignore NMI

	cmpl $2,early_recursion_flag(%rip)
	jz  1f
	incl early_recursion_flag(%rip)

	pushq %rax		# 64(%rsp)
	pushq %rcx		# 56(%rsp)
	pushq %rdx		# 48(%rsp)
	pushq %rsi		# 40(%rsp)
	pushq %rdi		# 32(%rsp)
	pushq %r8		# 24(%rsp)
	pushq %r9		# 16(%rsp)
	pushq %r10		#  8(%rsp)
	pushq %r11		#  0(%rsp)

	cmpl $__KERNEL_CS,96(%rsp)
	jne 11f

	cmpl $14,72(%rsp)	# Page fault?
	jnz 10f
	GET_CR2_INTO(%rdi)	# can clobber any volatile register if pv
	call early_make_pgtable
	andl %eax,%eax
	jz 20f			# All good

10:
	leaq 88(%rsp),%rdi	# Pointer to %rip
	call early_fixup_exception
	andl %eax,%eax
	jnz 20f			# Found an exception entry

11:
#ifdef CONFIG_EARLY_PRINTK
	GET_CR2_INTO(%r9)	# can clobber any volatile register if pv
	movl 80(%rsp),%r8d	# error code
	movl 72(%rsp),%esi	# vector number
	movl 96(%rsp),%edx	# %cs
	movq 88(%rsp),%rcx	# %rip
	xorl %eax,%eax
	leaq early_idt_msg(%rip),%rdi
	call early_printk
	cmpl $2,early_recursion_flag(%rip)
	jz  1f
	call dump_stack
#ifdef CONFIG_KALLSYMS	
	leaq early_idt_ripmsg(%rip),%rdi
	movq 40(%rsp),%rsi	# %rip again
	call __print_symbol
#endif
#endif /* EARLY_PRINTK */
1:	hlt
	jmp 1b

20:	# Exception table entry found or page table generated
	popq %r11
	popq %r10
	popq %r9
	popq %r8
	popq %rdi
	popq %rsi
	popq %rdx
	popq %rcx
	popq %rax
	decl early_recursion_flag(%rip)
.Lis_nmi:
	addq $16,%rsp		# drop vector number and error code
	INTERRUPT_RETURN
ENDPROC(early_idt_handler_common)

	__INITDATA

	.balign 4
early_recursion_flag:
	.long 0

#ifdef CONFIG_EARLY_PRINTK
early_idt_msg:
	.asciz "PANIC: early exception %02lx rip %lx:%lx error %lx cr2 %lx\n"
early_idt_ripmsg:
	.asciz "RIP %s\n"
#endif /* CONFIG_EARLY_PRINTK */

#define NEXT_PAGE(name) \
	.balign	PAGE_SIZE; \
GLOBAL(name)

/* Automate the creation of 1 to 1 mapping pmd entries */
#define PMDS(START, PERM, COUNT)			\
	i = 0 ;						\
	.rept (COUNT) ;					\
	.quad	(START) + (i << PMD_SHIFT) + (PERM) ;	\
	i = i + 1 ;					\
	.endr

	__INITDATA
NEXT_PAGE(early_level4_pgt)
	.fill	511,8,0
	.quad	level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE

NEXT_PAGE(early_dynamic_pgts)
	.fill	512*EARLY_DYNAMIC_PAGE_TABLES,8,0

	.data

#ifndef CONFIG_XEN
NEXT_PAGE(init_level4_pgt)
	.fill	512,8,0
#else
NEXT_PAGE(init_level4_pgt)
	.quad   level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE
	.org    init_level4_pgt + L4_PAGE_OFFSET*8, 0
	.quad   level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE
	.org    init_level4_pgt + L4_START_KERNEL*8, 0
	/* (2^48-(2*1024*1024*1024))/(2^39) = 511 */
	.quad   level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE

NEXT_PAGE(level3_ident_pgt)
	.quad	level2_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE
	.fill	511, 8, 0
NEXT_PAGE(level2_ident_pgt)
	/* Since I easily can, map the first 1G.
	 * Don't set NX because code runs from these pages.
	 */
	PMDS(0, __PAGE_KERNEL_IDENT_LARGE_EXEC, PTRS_PER_PMD)
#endif

NEXT_PAGE(level3_kernel_pgt)
	.fill	L3_START_KERNEL,8,0
	/* (2^48-(2*1024*1024*1024)-((2^39)*511))/(2^30) = 510 */
	.quad	level2_kernel_pgt - __START_KERNEL_map + _KERNPG_TABLE
	.quad	level2_fixmap_pgt - __START_KERNEL_map + _PAGE_TABLE

NEXT_PAGE(level2_kernel_pgt)
	/*
	 * 512 MB kernel mapping. We spend a full page on this pagetable
	 * anyway.
	 *
	 * The kernel code+data+bss must not be bigger than that.
	 *
	 * (NOTE: at +512MB starts the module area, see MODULES_VADDR.
	 *  If you want to increase this then increase MODULES_VADDR
	 *  too.)
	 */
	PMDS(0, __PAGE_KERNEL_LARGE_EXEC,
		KERNEL_IMAGE_SIZE/PMD_SIZE)

NEXT_PAGE(level2_fixmap_pgt)
	.fill	506,8,0
	.quad	level1_fixmap_pgt - __START_KERNEL_map + _PAGE_TABLE
	/* 8MB reserved for vsyscalls + a 2MB hole = 4 + 1 entries */
	.fill	5,8,0

NEXT_PAGE(level1_fixmap_pgt)
	.fill	512,8,0

#undef PMDS

	.data
	.align 16
	.globl early_gdt_descr
early_gdt_descr:
	.word	GDT_ENTRIES*8-1
early_gdt_descr_base:
	.quad	INIT_PER_CPU_VAR(gdt_page)

ENTRY(phys_base)
	/* This must match the first entry in level2_kernel_pgt */
	.quad   0x0000000000000000

#include "../../x86/xen/xen-head.S"
	
	__PAGE_ALIGNED_BSS
NEXT_PAGE(empty_zero_page)
	.skip PAGE_SIZE

OpenPOWER on IntegriCloud