xref: /linux/arch/x86/kernel/head_32.S (revision d39d0ed196aa1685bb24771e92f78633c66ac9cb) 
1/*
2 *
3 *  Copyright (C) 1991, 1992  Linus Torvalds
4 *
5 *  Enhanced CPU detection and feature setting code by Mike Jagdis
6 *  and Martin Mares, November 1997.
7 */
8
9.text
10#include <linux/threads.h>
11#include <linux/init.h>
12#include <linux/linkage.h>
13#include <asm/segment.h>
14#include <asm/page_types.h>
15#include <asm/pgtable_types.h>
16#include <asm/cache.h>
17#include <asm/thread_info.h>
18#include <asm/asm-offsets.h>
19#include <asm/setup.h>
20#include <asm/processor-flags.h>
21#include <asm/msr-index.h>
22#include <asm/cpufeature.h>
23#include <asm/percpu.h>
24
25/* Physical address */
26#define pa(X) ((X) - __PAGE_OFFSET)
27
28/*
29 * References to members of the new_cpu_data structure.
30 */
31
32#define X86		new_cpu_data+CPUINFO_x86
33#define X86_VENDOR	new_cpu_data+CPUINFO_x86_vendor
34#define X86_MODEL	new_cpu_data+CPUINFO_x86_model
35#define X86_MASK	new_cpu_data+CPUINFO_x86_mask
36#define X86_HARD_MATH	new_cpu_data+CPUINFO_hard_math
37#define X86_CPUID	new_cpu_data+CPUINFO_cpuid_level
38#define X86_CAPABILITY	new_cpu_data+CPUINFO_x86_capability
39#define X86_VENDOR_ID	new_cpu_data+CPUINFO_x86_vendor_id
40
41/*
42 * This is how much memory in addition to the memory covered up to
43 * and including _end we need mapped initially.
44 * We need:
45 *     (KERNEL_IMAGE_SIZE/4096) / 1024 pages (worst case, non PAE)
46 *     (KERNEL_IMAGE_SIZE/4096) / 512 + 4 pages (worst case for PAE)
47 *
48 * Modulo rounding, each megabyte assigned here requires a kilobyte of
49 * memory, which is currently unreclaimed.
50 *
51 * This should be a multiple of a page.
52 *
53 * KERNEL_IMAGE_SIZE should be greater than pa(_end)
54 * and small than max_low_pfn, otherwise will waste some page table entries
55 */
56
57#if PTRS_PER_PMD > 1
58#define PAGE_TABLE_SIZE(pages) (((pages) / PTRS_PER_PMD) + PTRS_PER_PGD)
59#else
60#define PAGE_TABLE_SIZE(pages) ((pages) / PTRS_PER_PGD)
61#endif
62
63/* Enough space to fit pagetables for the low memory linear map */
64MAPPING_BEYOND_END = \
65	PAGE_TABLE_SIZE(((1<<32) - __PAGE_OFFSET) >> PAGE_SHIFT) << PAGE_SHIFT
66
67/*
68 * Worst-case size of the kernel mapping we need to make:
69 * the worst-case size of the kernel itself, plus the extra we need
70 * to map for the linear map.
71 */
72KERNEL_PAGES = (KERNEL_IMAGE_SIZE + MAPPING_BEYOND_END)>>PAGE_SHIFT
73
74INIT_MAP_SIZE = PAGE_TABLE_SIZE(KERNEL_PAGES) * PAGE_SIZE_asm
75RESERVE_BRK(pagetables, INIT_MAP_SIZE)
76
77/*
78 * 32-bit kernel entrypoint; only used by the boot CPU.  On entry,
79 * %esi points to the real-mode code as a 32-bit pointer.
80 * CS and DS must be 4 GB flat segments, but we don't depend on
81 * any particular GDT layout, because we load our own as soon as we
82 * can.
83 */
84__HEAD
85ENTRY(startup_32)
86	/* test KEEP_SEGMENTS flag to see if the bootloader is asking
87		us to not reload segments */
88	testb $(1<<6), BP_loadflags(%esi)
89	jnz 2f
90
91/*
92 * Set segments to known values.
93 */
94	lgdt pa(boot_gdt_descr)
95	movl $(__BOOT_DS),%eax
96	movl %eax,%ds
97	movl %eax,%es
98	movl %eax,%fs
99	movl %eax,%gs
1002:
101
102/*
103 * Clear BSS first so that there are no surprises...
104 */
105	cld
106	xorl %eax,%eax
107	movl $pa(__bss_start),%edi
108	movl $pa(__bss_stop),%ecx
109	subl %edi,%ecx
110	shrl $2,%ecx
111	rep ; stosl
112/*
113 * Copy bootup parameters out of the way.
114 * Note: %esi still has the pointer to the real-mode data.
115 * With the kexec as boot loader, parameter segment might be loaded beyond
116 * kernel image and might not even be addressable by early boot page tables.
117 * (kexec on panic case). Hence copy out the parameters before initializing
118 * page tables.
119 */
120	movl $pa(boot_params),%edi
121	movl $(PARAM_SIZE/4),%ecx
122	cld
123	rep
124	movsl
125	movl pa(boot_params) + NEW_CL_POINTER,%esi
126	andl %esi,%esi
127	jz 1f			# No comand line
128	movl $pa(boot_command_line),%edi
129	movl $(COMMAND_LINE_SIZE/4),%ecx
130	rep
131	movsl
1321:
133
134#ifdef CONFIG_OLPC_OPENFIRMWARE
135	/* save OFW's pgdir table for later use when calling into OFW */
136	movl %cr3, %eax
137	movl %eax, pa(olpc_ofw_pgd)
138#endif
139
140#ifdef CONFIG_PARAVIRT
141	/* This is can only trip for a broken bootloader... */
142	cmpw $0x207, pa(boot_params + BP_version)
143	jb default_entry
144
145	/* Paravirt-compatible boot parameters.  Look to see what architecture
146		we're booting under. */
147	movl pa(boot_params + BP_hardware_subarch), %eax
148	cmpl $num_subarch_entries, %eax
149	jae bad_subarch
150
151	movl pa(subarch_entries)(,%eax,4), %eax
152	subl $__PAGE_OFFSET, %eax
153	jmp *%eax
154
155bad_subarch:
156WEAK(lguest_entry)
157WEAK(xen_entry)
158	/* Unknown implementation; there's really
159	   nothing we can do at this point. */
160	ud2a
161
162	__INITDATA
163
164subarch_entries:
165	.long default_entry		/* normal x86/PC */
166	.long lguest_entry		/* lguest hypervisor */
167	.long xen_entry			/* Xen hypervisor */
168	.long default_entry		/* Moorestown MID */
169num_subarch_entries = (. - subarch_entries) / 4
170.previous
171#endif /* CONFIG_PARAVIRT */
172
173/*
174 * Initialize page tables.  This creates a PDE and a set of page
175 * tables, which are located immediately beyond __brk_base.  The variable
176 * _brk_end is set up to point to the first "safe" location.
177 * Mappings are created both at virtual address 0 (identity mapping)
178 * and PAGE_OFFSET for up to _end.
179 *
180 * Note that the stack is not yet set up!
181 */
182default_entry:
183#ifdef CONFIG_X86_PAE
184
185	/*
186	 * In PAE mode swapper_pg_dir is statically defined to contain enough
187	 * entries to cover the VMSPLIT option (that is the top 1, 2 or 3
188	 * entries). The identity mapping is handled by pointing two PGD
189	 * entries to the first kernel PMD.
190	 *
191	 * Note the upper half of each PMD or PTE are always zero at
192	 * this stage.
193	 */
194
195#define KPMDS (((-__PAGE_OFFSET) >> 30) & 3) /* Number of kernel PMDs */
196
197	xorl %ebx,%ebx				/* %ebx is kept at zero */
198
199	movl $pa(__brk_base), %edi
200	movl $pa(swapper_pg_pmd), %edx
201	movl $PTE_IDENT_ATTR, %eax
20210:
203	leal PDE_IDENT_ATTR(%edi),%ecx		/* Create PMD entry */
204	movl %ecx,(%edx)			/* Store PMD entry */
205						/* Upper half already zero */
206	addl $8,%edx
207	movl $512,%ecx
20811:
209	stosl
210	xchgl %eax,%ebx
211	stosl
212	xchgl %eax,%ebx
213	addl $0x1000,%eax
214	loop 11b
215
216	/*
217	 * End condition: we must map up to the end + MAPPING_BEYOND_END.
218	 */
219	movl $pa(_end) + MAPPING_BEYOND_END + PTE_IDENT_ATTR, %ebp
220	cmpl %ebp,%eax
221	jb 10b
2221:
223	addl $__PAGE_OFFSET, %edi
224	movl %edi, pa(_brk_end)
225	shrl $12, %eax
226	movl %eax, pa(max_pfn_mapped)
227
228	/* Do early initialization of the fixmap area */
229	movl $pa(swapper_pg_fixmap)+PDE_IDENT_ATTR,%eax
230	movl %eax,pa(swapper_pg_pmd+0x1000*KPMDS-8)
231#else	/* Not PAE */
232
233page_pde_offset = (__PAGE_OFFSET >> 20);
234
235	movl $pa(__brk_base), %edi
236	movl $pa(swapper_pg_dir), %edx
237	movl $PTE_IDENT_ATTR, %eax
23810:
239	leal PDE_IDENT_ATTR(%edi),%ecx		/* Create PDE entry */
240	movl %ecx,(%edx)			/* Store identity PDE entry */
241	movl %ecx,page_pde_offset(%edx)		/* Store kernel PDE entry */
242	addl $4,%edx
243	movl $1024, %ecx
24411:
245	stosl
246	addl $0x1000,%eax
247	loop 11b
248	/*
249	 * End condition: we must map up to the end + MAPPING_BEYOND_END.
250	 */
251	movl $pa(_end) + MAPPING_BEYOND_END + PTE_IDENT_ATTR, %ebp
252	cmpl %ebp,%eax
253	jb 10b
254	addl $__PAGE_OFFSET, %edi
255	movl %edi, pa(_brk_end)
256	shrl $12, %eax
257	movl %eax, pa(max_pfn_mapped)
258
259	/* Do early initialization of the fixmap area */
260	movl $pa(swapper_pg_fixmap)+PDE_IDENT_ATTR,%eax
261	movl %eax,pa(swapper_pg_dir+0xffc)
262#endif
263	jmp 3f
264/*
265 * Non-boot CPU entry point; entered from trampoline.S
266 * We can't lgdt here, because lgdt itself uses a data segment, but
267 * we know the trampoline has already loaded the boot_gdt for us.
268 *
269 * If cpu hotplug is not supported then this code can go in init section
270 * which will be freed later
271 */
272
273__CPUINIT
274
275#ifdef CONFIG_SMP
276ENTRY(startup_32_smp)
277	cld
278	movl $(__BOOT_DS),%eax
279	movl %eax,%ds
280	movl %eax,%es
281	movl %eax,%fs
282	movl %eax,%gs
283#endif /* CONFIG_SMP */
2843:
285
286/*
287 *	New page tables may be in 4Mbyte page mode and may
288 *	be using the global pages.
289 *
290 *	NOTE! If we are on a 486 we may have no cr4 at all!
291 *	So we do not try to touch it unless we really have
292 *	some bits in it to set.  This won't work if the BSP
293 *	implements cr4 but this AP does not -- very unlikely
294 *	but be warned!  The same applies to the pse feature
295 *	if not equally supported. --macro
296 *
297 *	NOTE! We have to correct for the fact that we're
298 *	not yet offset PAGE_OFFSET..
299 */
300#define cr4_bits pa(mmu_cr4_features)
301	movl cr4_bits,%edx
302	andl %edx,%edx
303	jz 6f
304	movl %cr4,%eax		# Turn on paging options (PSE,PAE,..)
305	orl %edx,%eax
306	movl %eax,%cr4
307
308	testb $X86_CR4_PAE, %al		# check if PAE is enabled
309	jz 6f
310
311	/* Check if extended functions are implemented */
312	movl $0x80000000, %eax
313	cpuid
314	/* Value must be in the range 0x80000001 to 0x8000ffff */
315	subl $0x80000001, %eax
316	cmpl $(0x8000ffff-0x80000001), %eax
317	ja 6f
318	mov $0x80000001, %eax
319	cpuid
320	/* Execute Disable bit supported? */
321	btl $(X86_FEATURE_NX & 31), %edx
322	jnc 6f
323
324	/* Setup EFER (Extended Feature Enable Register) */
325	movl $MSR_EFER, %ecx
326	rdmsr
327
328	btsl $_EFER_NX, %eax
329	/* Make changes effective */
330	wrmsr
331
3326:
333
334/*
335 * Enable paging
336 */
337	movl $pa(swapper_pg_dir),%eax
338	movl %eax,%cr3		/* set the page table pointer.. */
339	movl %cr0,%eax
340	orl  $X86_CR0_PG,%eax
341	movl %eax,%cr0		/* ..and set paging (PG) bit */
342	ljmp $__BOOT_CS,$1f	/* Clear prefetch and normalize %eip */
3431:
344	/* Set up the stack pointer */
345	lss stack_start,%esp
346
347/*
348 * Initialize eflags.  Some BIOS's leave bits like NT set.  This would
349 * confuse the debugger if this code is traced.
350 * XXX - best to initialize before switching to protected mode.
351 */
352	pushl $0
353	popfl
354
355#ifdef CONFIG_SMP
356	cmpb $0, ready
357	jz  1f				/* Initial CPU cleans BSS */
358	jmp checkCPUtype
3591:
360#endif /* CONFIG_SMP */
361
362/*
363 * start system 32-bit setup. We need to re-do some of the things done
364 * in 16-bit mode for the "real" operations.
365 */
366	call setup_idt
367
368checkCPUtype:
369
370	movl $-1,X86_CPUID		#  -1 for no CPUID initially
371
372/* check if it is 486 or 386. */
373/*
374 * XXX - this does a lot of unnecessary setup.  Alignment checks don't
375 * apply at our cpl of 0 and the stack ought to be aligned already, and
376 * we don't need to preserve eflags.
377 */
378
379	movb $3,X86		# at least 386
380	pushfl			# push EFLAGS
381	popl %eax		# get EFLAGS
382	movl %eax,%ecx		# save original EFLAGS
383	xorl $0x240000,%eax	# flip AC and ID bits in EFLAGS
384	pushl %eax		# copy to EFLAGS
385	popfl			# set EFLAGS
386	pushfl			# get new EFLAGS
387	popl %eax		# put it in eax
388	xorl %ecx,%eax		# change in flags
389	pushl %ecx		# restore original EFLAGS
390	popfl
391	testl $0x40000,%eax	# check if AC bit changed
392	je is386
393
394	movb $4,X86		# at least 486
395	testl $0x200000,%eax	# check if ID bit changed
396	je is486
397
398	/* get vendor info */
399	xorl %eax,%eax			# call CPUID with 0 -> return vendor ID
400	cpuid
401	movl %eax,X86_CPUID		# save CPUID level
402	movl %ebx,X86_VENDOR_ID		# lo 4 chars
403	movl %edx,X86_VENDOR_ID+4	# next 4 chars
404	movl %ecx,X86_VENDOR_ID+8	# last 4 chars
405
406	orl %eax,%eax			# do we have processor info as well?
407	je is486
408
409	movl $1,%eax		# Use the CPUID instruction to get CPU type
410	cpuid
411	movb %al,%cl		# save reg for future use
412	andb $0x0f,%ah		# mask processor family
413	movb %ah,X86
414	andb $0xf0,%al		# mask model
415	shrb $4,%al
416	movb %al,X86_MODEL
417	andb $0x0f,%cl		# mask mask revision
418	movb %cl,X86_MASK
419	movl %edx,X86_CAPABILITY
420
421is486:	movl $0x50022,%ecx	# set AM, WP, NE and MP
422	jmp 2f
423
424is386:	movl $2,%ecx		# set MP
4252:	movl %cr0,%eax
426	andl $0x80000011,%eax	# Save PG,PE,ET
427	orl %ecx,%eax
428	movl %eax,%cr0
429
430	call check_x87
431	lgdt early_gdt_descr
432	lidt idt_descr
433	ljmp $(__KERNEL_CS),$1f
4341:	movl $(__KERNEL_DS),%eax	# reload all the segment registers
435	movl %eax,%ss			# after changing gdt.
436
437	movl $(__USER_DS),%eax		# DS/ES contains default USER segment
438	movl %eax,%ds
439	movl %eax,%es
440
441	movl $(__KERNEL_PERCPU), %eax
442	movl %eax,%fs			# set this cpu's percpu
443
444#ifdef CONFIG_CC_STACKPROTECTOR
445	/*
446	 * The linker can't handle this by relocation.  Manually set
447	 * base address in stack canary segment descriptor.
448	 */
449	cmpb $0,ready
450	jne 1f
451	movl $gdt_page,%eax
452	movl $stack_canary,%ecx
453	movw %cx, 8 * GDT_ENTRY_STACK_CANARY + 2(%eax)
454	shrl $16, %ecx
455	movb %cl, 8 * GDT_ENTRY_STACK_CANARY + 4(%eax)
456	movb %ch, 8 * GDT_ENTRY_STACK_CANARY + 7(%eax)
4571:
458#endif
459	movl $(__KERNEL_STACK_CANARY),%eax
460	movl %eax,%gs
461
462	xorl %eax,%eax			# Clear LDT
463	lldt %ax
464
465	cld			# gcc2 wants the direction flag cleared at all times
466	pushl $0		# fake return address for unwinder
467#ifdef CONFIG_SMP
468	movb ready, %cl
469	movb $1, ready
470	cmpb $0,%cl		# the first CPU calls start_kernel
471	je   1f
472	movl (stack_start), %esp
4731:
474#endif /* CONFIG_SMP */
475	jmp *(initial_code)
476
477/*
478 * We depend on ET to be correct. This checks for 287/387.
479 */
480check_x87:
481	movb $0,X86_HARD_MATH
482	clts
483	fninit
484	fstsw %ax
485	cmpb $0,%al
486	je 1f
487	movl %cr0,%eax		/* no coprocessor: have to set bits */
488	xorl $4,%eax		/* set EM */
489	movl %eax,%cr0
490	ret
491	ALIGN
4921:	movb $1,X86_HARD_MATH
493	.byte 0xDB,0xE4		/* fsetpm for 287, ignored by 387 */
494	ret
495
496/*
497 *  setup_idt
498 *
499 *  sets up a idt with 256 entries pointing to
500 *  ignore_int, interrupt gates. It doesn't actually load
501 *  idt - that can be done only after paging has been enabled
502 *  and the kernel moved to PAGE_OFFSET. Interrupts
503 *  are enabled elsewhere, when we can be relatively
504 *  sure everything is ok.
505 *
506 *  Warning: %esi is live across this function.
507 */
508setup_idt:
509	lea ignore_int,%edx
510	movl $(__KERNEL_CS << 16),%eax
511	movw %dx,%ax		/* selector = 0x0010 = cs */
512	movw $0x8E00,%dx	/* interrupt gate - dpl=0, present */
513
514	lea idt_table,%edi
515	mov $256,%ecx
516rp_sidt:
517	movl %eax,(%edi)
518	movl %edx,4(%edi)
519	addl $8,%edi
520	dec %ecx
521	jne rp_sidt
522
523.macro	set_early_handler handler,trapno
524	lea \handler,%edx
525	movl $(__KERNEL_CS << 16),%eax
526	movw %dx,%ax
527	movw $0x8E00,%dx	/* interrupt gate - dpl=0, present */
528	lea idt_table,%edi
529	movl %eax,8*\trapno(%edi)
530	movl %edx,8*\trapno+4(%edi)
531.endm
532
533	set_early_handler handler=early_divide_err,trapno=0
534	set_early_handler handler=early_illegal_opcode,trapno=6
535	set_early_handler handler=early_protection_fault,trapno=13
536	set_early_handler handler=early_page_fault,trapno=14
537
538	ret
539
540early_divide_err:
541	xor %edx,%edx
542	pushl $0	/* fake errcode */
543	jmp early_fault
544
545early_illegal_opcode:
546	movl $6,%edx
547	pushl $0	/* fake errcode */
548	jmp early_fault
549
550early_protection_fault:
551	movl $13,%edx
552	jmp early_fault
553
554early_page_fault:
555	movl $14,%edx
556	jmp early_fault
557
558early_fault:
559	cld
560#ifdef CONFIG_PRINTK
561	pusha
562	movl $(__KERNEL_DS),%eax
563	movl %eax,%ds
564	movl %eax,%es
565	cmpl $2,early_recursion_flag
566	je hlt_loop
567	incl early_recursion_flag
568	movl %cr2,%eax
569	pushl %eax
570	pushl %edx		/* trapno */
571	pushl $fault_msg
572	call printk
573#endif
574	call dump_stack
575hlt_loop:
576	hlt
577	jmp hlt_loop
578
579/* This is the default interrupt "handler" :-) */
580	ALIGN
581ignore_int:
582	cld
583#ifdef CONFIG_PRINTK
584	pushl %eax
585	pushl %ecx
586	pushl %edx
587	pushl %es
588	pushl %ds
589	movl $(__KERNEL_DS),%eax
590	movl %eax,%ds
591	movl %eax,%es
592	cmpl $2,early_recursion_flag
593	je hlt_loop
594	incl early_recursion_flag
595	pushl 16(%esp)
596	pushl 24(%esp)
597	pushl 32(%esp)
598	pushl 40(%esp)
599	pushl $int_msg
600	call printk
601
602	call dump_stack
603
604	addl $(5*4),%esp
605	popl %ds
606	popl %es
607	popl %edx
608	popl %ecx
609	popl %eax
610#endif
611	iret
612
613	__REFDATA
614.align 4
615ENTRY(initial_code)
616	.long i386_start_kernel
617
618/*
619 * BSS section
620 */
621__PAGE_ALIGNED_BSS
622	.align PAGE_SIZE_asm
623#ifdef CONFIG_X86_PAE
624swapper_pg_pmd:
625	.fill 1024*KPMDS,4,0
626#else
627ENTRY(swapper_pg_dir)
628	.fill 1024,4,0
629#endif
630swapper_pg_fixmap:
631	.fill 1024,4,0
632ENTRY(empty_zero_page)
633	.fill 4096,1,0
634
635/*
636 * This starts the data section.
637 */
638#ifdef CONFIG_X86_PAE
639__PAGE_ALIGNED_DATA
640	/* Page-aligned for the benefit of paravirt? */
641	.align PAGE_SIZE_asm
642ENTRY(swapper_pg_dir)
643	.long	pa(swapper_pg_pmd+PGD_IDENT_ATTR),0	/* low identity map */
644# if KPMDS == 3
645	.long	pa(swapper_pg_pmd+PGD_IDENT_ATTR),0
646	.long	pa(swapper_pg_pmd+PGD_IDENT_ATTR+0x1000),0
647	.long	pa(swapper_pg_pmd+PGD_IDENT_ATTR+0x2000),0
648# elif KPMDS == 2
649	.long	0,0
650	.long	pa(swapper_pg_pmd+PGD_IDENT_ATTR),0
651	.long	pa(swapper_pg_pmd+PGD_IDENT_ATTR+0x1000),0
652# elif KPMDS == 1
653	.long	0,0
654	.long	0,0
655	.long	pa(swapper_pg_pmd+PGD_IDENT_ATTR),0
656# else
657#  error "Kernel PMDs should be 1, 2 or 3"
658# endif
659	.align PAGE_SIZE_asm		/* needs to be page-sized too */
660#endif
661
662.data
663ENTRY(stack_start)
664	.long init_thread_union+THREAD_SIZE
665	.long __BOOT_DS
666
667ready:	.byte 0
668
669early_recursion_flag:
670	.long 0
671
672int_msg:
673	.asciz "Unknown interrupt or fault at: %p %p %p\n"
674
675fault_msg:
676/* fault info: */
677	.ascii "BUG: Int %d: CR2 %p\n"
678/* pusha regs: */
679	.ascii "     EDI %p  ESI %p  EBP %p  ESP %p\n"
680	.ascii "     EBX %p  EDX %p  ECX %p  EAX %p\n"
681/* fault frame: */
682	.ascii "     err %p  EIP %p   CS %p  flg %p\n"
683	.ascii "Stack: %p %p %p %p %p %p %p %p\n"
684	.ascii "       %p %p %p %p %p %p %p %p\n"
685	.asciz "       %p %p %p %p %p %p %p %p\n"
686
687#include "../../x86/xen/xen-head.S"
688
689/*
690 * The IDT and GDT 'descriptors' are a strange 48-bit object
691 * only used by the lidt and lgdt instructions. They are not
692 * like usual segment descriptors - they consist of a 16-bit
693 * segment size, and 32-bit linear address value:
694 */
695
696.globl boot_gdt_descr
697.globl idt_descr
698
699	ALIGN
700# early boot GDT descriptor (must use 1:1 address mapping)
701	.word 0				# 32 bit align gdt_desc.address
702boot_gdt_descr:
703	.word __BOOT_DS+7
704	.long boot_gdt - __PAGE_OFFSET
705
706	.word 0				# 32-bit align idt_desc.address
707idt_descr:
708	.word IDT_ENTRIES*8-1		# idt contains 256 entries
709	.long idt_table
710
711# boot GDT descriptor (later on used by CPU#0):
712	.word 0				# 32 bit align gdt_desc.address
713ENTRY(early_gdt_descr)
714	.word GDT_ENTRIES*8-1
715	.long gdt_page			/* Overwritten for secondary CPUs */
716
717/*
718 * The boot_gdt must mirror the equivalent in setup.S and is
719 * used only for booting.
720 */
721	.align L1_CACHE_BYTES
722ENTRY(boot_gdt)
723	.fill GDT_ENTRY_BOOT_CS,8,0
724	.quad 0x00cf9a000000ffff	/* kernel 4GB code at 0x00000000 */
725	.quad 0x00cf92000000ffff	/* kernel 4GB data at 0x00000000 */
726