xref: /openbmc/linux/arch/x86/kernel/head_32.S (revision f42b3800) 
1/*
2 *  linux/arch/i386/kernel/head.S -- the 32-bit startup code.
3 *
4 *  Copyright (C) 1991, 1992  Linus Torvalds
5 *
6 *  Enhanced CPU detection and feature setting code by Mike Jagdis
7 *  and Martin Mares, November 1997.
8 */
9
10.text
11#include <linux/threads.h>
12#include <linux/init.h>
13#include <linux/linkage.h>
14#include <asm/segment.h>
15#include <asm/page.h>
16#include <asm/pgtable.h>
17#include <asm/desc.h>
18#include <asm/cache.h>
19#include <asm/thread_info.h>
20#include <asm/asm-offsets.h>
21#include <asm/setup.h>
22#include <asm/processor-flags.h>
23
24/* Physical address */
25#define pa(X) ((X) - __PAGE_OFFSET)
26
27/*
28 * References to members of the new_cpu_data structure.
29 */
30
31#define X86		new_cpu_data+CPUINFO_x86
32#define X86_VENDOR	new_cpu_data+CPUINFO_x86_vendor
33#define X86_MODEL	new_cpu_data+CPUINFO_x86_model
34#define X86_MASK	new_cpu_data+CPUINFO_x86_mask
35#define X86_HARD_MATH	new_cpu_data+CPUINFO_hard_math
36#define X86_CPUID	new_cpu_data+CPUINFO_cpuid_level
37#define X86_CAPABILITY	new_cpu_data+CPUINFO_x86_capability
38#define X86_VENDOR_ID	new_cpu_data+CPUINFO_x86_vendor_id
39
40/*
41 * This is how much memory *in addition to the memory covered up to
42 * and including _end* we need mapped initially.
43 * We need:
44 *  - one bit for each possible page, but only in low memory, which means
45 *     2^32/4096/8 = 128K worst case (4G/4G split.)
46 *  - enough space to map all low memory, which means
47 *     (2^32/4096) / 1024 pages (worst case, non PAE)
48 *     (2^32/4096) / 512 + 4 pages (worst case for PAE)
49 *  - a few pages for allocator use before the kernel pagetable has
50 *     been set up
51 *
52 * Modulo rounding, each megabyte assigned here requires a kilobyte of
53 * memory, which is currently unreclaimed.
54 *
55 * This should be a multiple of a page.
56 */
57LOW_PAGES = 1<<(32-PAGE_SHIFT_asm)
58
59/*
60 * To preserve the DMA pool in PAGEALLOC kernels, we'll allocate
61 * pagetables from above the 16MB DMA limit, so we'll have to set
62 * up pagetables 16MB more (worst-case):
63 */
64#ifdef CONFIG_DEBUG_PAGEALLOC
65LOW_PAGES = LOW_PAGES + 0x1000000
66#endif
67
68#if PTRS_PER_PMD > 1
69PAGE_TABLE_SIZE = (LOW_PAGES / PTRS_PER_PMD) + PTRS_PER_PGD
70#else
71PAGE_TABLE_SIZE = (LOW_PAGES / PTRS_PER_PGD)
72#endif
73BOOTBITMAP_SIZE = LOW_PAGES / 8
74ALLOCATOR_SLOP = 4
75
76INIT_MAP_BEYOND_END = BOOTBITMAP_SIZE + (PAGE_TABLE_SIZE + ALLOCATOR_SLOP)*PAGE_SIZE_asm
77
78/*
79 * 32-bit kernel entrypoint; only used by the boot CPU.  On entry,
80 * %esi points to the real-mode code as a 32-bit pointer.
81 * CS and DS must be 4 GB flat segments, but we don't depend on
82 * any particular GDT layout, because we load our own as soon as we
83 * can.
84 */
85.section .text.head,"ax",@progbits
86ENTRY(startup_32)
87	/* test KEEP_SEGMENTS flag to see if the bootloader is asking
88		us to not reload segments */
89	testb $(1<<6), BP_loadflags(%esi)
90	jnz 2f
91
92/*
93 * Set segments to known values.
94 */
95	lgdt pa(boot_gdt_descr)
96	movl $(__BOOT_DS),%eax
97	movl %eax,%ds
98	movl %eax,%es
99	movl %eax,%fs
100	movl %eax,%gs
1012:
102
103/*
104 * Clear BSS first so that there are no surprises...
105 */
106	cld
107	xorl %eax,%eax
108	movl $pa(__bss_start),%edi
109	movl $pa(__bss_stop),%ecx
110	subl %edi,%ecx
111	shrl $2,%ecx
112	rep ; stosl
113/*
114 * Copy bootup parameters out of the way.
115 * Note: %esi still has the pointer to the real-mode data.
116 * With the kexec as boot loader, parameter segment might be loaded beyond
117 * kernel image and might not even be addressable by early boot page tables.
118 * (kexec on panic case). Hence copy out the parameters before initializing
119 * page tables.
120 */
121	movl $pa(boot_params),%edi
122	movl $(PARAM_SIZE/4),%ecx
123	cld
124	rep
125	movsl
126	movl pa(boot_params) + NEW_CL_POINTER,%esi
127	andl %esi,%esi
128	jz 1f			# No comand line
129	movl $pa(boot_command_line),%edi
130	movl $(COMMAND_LINE_SIZE/4),%ecx
131	rep
132	movsl
1331:
134
135#ifdef CONFIG_PARAVIRT
136	/* This is can only trip for a broken bootloader... */
137	cmpw $0x207, pa(boot_params + BP_version)
138	jb default_entry
139
140	/* Paravirt-compatible boot parameters.  Look to see what architecture
141		we're booting under. */
142	movl pa(boot_params + BP_hardware_subarch), %eax
143	cmpl $num_subarch_entries, %eax
144	jae bad_subarch
145
146	movl pa(subarch_entries)(,%eax,4), %eax
147	subl $__PAGE_OFFSET, %eax
148	jmp *%eax
149
150bad_subarch:
151WEAK(lguest_entry)
152WEAK(xen_entry)
153	/* Unknown implementation; there's really
154	   nothing we can do at this point. */
155	ud2a
156
157	__INITDATA
158
159subarch_entries:
160	.long default_entry		/* normal x86/PC */
161	.long lguest_entry		/* lguest hypervisor */
162	.long xen_entry			/* Xen hypervisor */
163num_subarch_entries = (. - subarch_entries) / 4
164.previous
165#endif /* CONFIG_PARAVIRT */
166
167/*
168 * Initialize page tables.  This creates a PDE and a set of page
169 * tables, which are located immediately beyond _end.  The variable
170 * init_pg_tables_end is set up to point to the first "safe" location.
171 * Mappings are created both at virtual address 0 (identity mapping)
172 * and PAGE_OFFSET for up to _end+sizeof(page tables)+INIT_MAP_BEYOND_END.
173 *
174 * Note that the stack is not yet set up!
175 */
176#define PTE_ATTR	0x007		/* PRESENT+RW+USER */
177#define PDE_ATTR	0x067		/* PRESENT+RW+USER+DIRTY+ACCESSED */
178#define PGD_ATTR	0x001		/* PRESENT (no other attributes) */
179
180default_entry:
181#ifdef CONFIG_X86_PAE
182
183	/*
184	 * In PAE mode swapper_pg_dir is statically defined to contain enough
185	 * entries to cover the VMSPLIT option (that is the top 1, 2 or 3
186	 * entries). The identity mapping is handled by pointing two PGD
187	 * entries to the first kernel PMD.
188	 *
189	 * Note the upper half of each PMD or PTE are always zero at
190	 * this stage.
191	 */
192
193#define KPMDS ((0x100000000-__PAGE_OFFSET) >> 30) /* Number of kernel PMDs */
194
195	xorl %ebx,%ebx				/* %ebx is kept at zero */
196
197	movl $pa(pg0), %edi
198	movl $pa(swapper_pg_pmd), %edx
199	movl $PTE_ATTR, %eax
20010:
201	leal PDE_ATTR(%edi),%ecx		/* Create PMD entry */
202	movl %ecx,(%edx)			/* Store PMD entry */
203						/* Upper half already zero */
204	addl $8,%edx
205	movl $512,%ecx
20611:
207	stosl
208	xchgl %eax,%ebx
209	stosl
210	xchgl %eax,%ebx
211	addl $0x1000,%eax
212	loop 11b
213
214	/*
215	 * End condition: we must map up to and including INIT_MAP_BEYOND_END
216	 * bytes beyond the end of our own page tables.
217	 */
218	leal (INIT_MAP_BEYOND_END+PTE_ATTR)(%edi),%ebp
219	cmpl %ebp,%eax
220	jb 10b
2211:
222	movl %edi,pa(init_pg_tables_end)
223
224	/* Do early initialization of the fixmap area */
225	movl $pa(swapper_pg_fixmap)+PDE_ATTR,%eax
226	movl %eax,pa(swapper_pg_pmd+0x1000*KPMDS-8)
227#else	/* Not PAE */
228
229page_pde_offset = (__PAGE_OFFSET >> 20);
230
231	movl $pa(pg0), %edi
232	movl $pa(swapper_pg_dir), %edx
233	movl $PTE_ATTR, %eax
23410:
235	leal PDE_ATTR(%edi),%ecx		/* Create PDE entry */
236	movl %ecx,(%edx)			/* Store identity PDE entry */
237	movl %ecx,page_pde_offset(%edx)		/* Store kernel PDE entry */
238	addl $4,%edx
239	movl $1024, %ecx
24011:
241	stosl
242	addl $0x1000,%eax
243	loop 11b
244	/*
245	 * End condition: we must map up to and including INIT_MAP_BEYOND_END
246	 * bytes beyond the end of our own page tables; the +0x007 is
247	 * the attribute bits
248	 */
249	leal (INIT_MAP_BEYOND_END+PTE_ATTR)(%edi),%ebp
250	cmpl %ebp,%eax
251	jb 10b
252	movl %edi,pa(init_pg_tables_end)
253
254	/* Do early initialization of the fixmap area */
255	movl $pa(swapper_pg_fixmap)+PDE_ATTR,%eax
256	movl %eax,pa(swapper_pg_dir+0xffc)
257#endif
258	jmp 3f
259/*
260 * Non-boot CPU entry point; entered from trampoline.S
261 * We can't lgdt here, because lgdt itself uses a data segment, but
262 * we know the trampoline has already loaded the boot_gdt for us.
263 *
264 * If cpu hotplug is not supported then this code can go in init section
265 * which will be freed later
266 */
267
268#ifndef CONFIG_HOTPLUG_CPU
269.section .init.text,"ax",@progbits
270#endif
271
272#ifdef CONFIG_SMP
273ENTRY(startup_32_smp)
274	cld
275	movl $(__BOOT_DS),%eax
276	movl %eax,%ds
277	movl %eax,%es
278	movl %eax,%fs
279	movl %eax,%gs
280#endif /* CONFIG_SMP */
2813:
282
283/*
284 *	New page tables may be in 4Mbyte page mode and may
285 *	be using the global pages.
286 *
287 *	NOTE! If we are on a 486 we may have no cr4 at all!
288 *	So we do not try to touch it unless we really have
289 *	some bits in it to set.  This won't work if the BSP
290 *	implements cr4 but this AP does not -- very unlikely
291 *	but be warned!  The same applies to the pse feature
292 *	if not equally supported. --macro
293 *
294 *	NOTE! We have to correct for the fact that we're
295 *	not yet offset PAGE_OFFSET..
296 */
297#define cr4_bits pa(mmu_cr4_features)
298	movl cr4_bits,%edx
299	andl %edx,%edx
300	jz 6f
301	movl %cr4,%eax		# Turn on paging options (PSE,PAE,..)
302	orl %edx,%eax
303	movl %eax,%cr4
304
305	btl $5, %eax		# check if PAE is enabled
306	jnc 6f
307
308	/* Check if extended functions are implemented */
309	movl $0x80000000, %eax
310	cpuid
311	cmpl $0x80000000, %eax
312	jbe 6f
313	mov $0x80000001, %eax
314	cpuid
315	/* Execute Disable bit supported? */
316	btl $20, %edx
317	jnc 6f
318
319	/* Setup EFER (Extended Feature Enable Register) */
320	movl $0xc0000080, %ecx
321	rdmsr
322
323	btsl $11, %eax
324	/* Make changes effective */
325	wrmsr
326
3276:
328
329/*
330 * Enable paging
331 */
332	movl $pa(swapper_pg_dir),%eax
333	movl %eax,%cr3		/* set the page table pointer.. */
334	movl %cr0,%eax
335	orl  $X86_CR0_PG,%eax
336	movl %eax,%cr0		/* ..and set paging (PG) bit */
337	ljmp $__BOOT_CS,$1f	/* Clear prefetch and normalize %eip */
3381:
339	/* Set up the stack pointer */
340	lss stack_start,%esp
341
342/*
343 * Initialize eflags.  Some BIOS's leave bits like NT set.  This would
344 * confuse the debugger if this code is traced.
345 * XXX - best to initialize before switching to protected mode.
346 */
347	pushl $0
348	popfl
349
350#ifdef CONFIG_SMP
351	cmpb $0, ready
352	jz  1f				/* Initial CPU cleans BSS */
353	jmp checkCPUtype
3541:
355#endif /* CONFIG_SMP */
356
357/*
358 * start system 32-bit setup. We need to re-do some of the things done
359 * in 16-bit mode for the "real" operations.
360 */
361	call setup_idt
362
363checkCPUtype:
364
365	movl $-1,X86_CPUID		#  -1 for no CPUID initially
366
367/* check if it is 486 or 386. */
368/*
369 * XXX - this does a lot of unnecessary setup.  Alignment checks don't
370 * apply at our cpl of 0 and the stack ought to be aligned already, and
371 * we don't need to preserve eflags.
372 */
373
374	movb $3,X86		# at least 386
375	pushfl			# push EFLAGS
376	popl %eax		# get EFLAGS
377	movl %eax,%ecx		# save original EFLAGS
378	xorl $0x240000,%eax	# flip AC and ID bits in EFLAGS
379	pushl %eax		# copy to EFLAGS
380	popfl			# set EFLAGS
381	pushfl			# get new EFLAGS
382	popl %eax		# put it in eax
383	xorl %ecx,%eax		# change in flags
384	pushl %ecx		# restore original EFLAGS
385	popfl
386	testl $0x40000,%eax	# check if AC bit changed
387	je is386
388
389	movb $4,X86		# at least 486
390	testl $0x200000,%eax	# check if ID bit changed
391	je is486
392
393	/* get vendor info */
394	xorl %eax,%eax			# call CPUID with 0 -> return vendor ID
395	cpuid
396	movl %eax,X86_CPUID		# save CPUID level
397	movl %ebx,X86_VENDOR_ID		# lo 4 chars
398	movl %edx,X86_VENDOR_ID+4	# next 4 chars
399	movl %ecx,X86_VENDOR_ID+8	# last 4 chars
400
401	orl %eax,%eax			# do we have processor info as well?
402	je is486
403
404	movl $1,%eax		# Use the CPUID instruction to get CPU type
405	cpuid
406	movb %al,%cl		# save reg for future use
407	andb $0x0f,%ah		# mask processor family
408	movb %ah,X86
409	andb $0xf0,%al		# mask model
410	shrb $4,%al
411	movb %al,X86_MODEL
412	andb $0x0f,%cl		# mask mask revision
413	movb %cl,X86_MASK
414	movl %edx,X86_CAPABILITY
415
416is486:	movl $0x50022,%ecx	# set AM, WP, NE and MP
417	jmp 2f
418
419is386:	movl $2,%ecx		# set MP
4202:	movl %cr0,%eax
421	andl $0x80000011,%eax	# Save PG,PE,ET
422	orl %ecx,%eax
423	movl %eax,%cr0
424
425	call check_x87
426	lgdt early_gdt_descr
427	lidt idt_descr
428	ljmp $(__KERNEL_CS),$1f
4291:	movl $(__KERNEL_DS),%eax	# reload all the segment registers
430	movl %eax,%ss			# after changing gdt.
431	movl %eax,%fs			# gets reset once there's real percpu
432
433	movl $(__USER_DS),%eax		# DS/ES contains default USER segment
434	movl %eax,%ds
435	movl %eax,%es
436
437	xorl %eax,%eax			# Clear GS and LDT
438	movl %eax,%gs
439	lldt %ax
440
441	cld			# gcc2 wants the direction flag cleared at all times
442	pushl $0		# fake return address for unwinder
443#ifdef CONFIG_SMP
444	movb ready, %cl
445	movb $1, ready
446	cmpb $0,%cl		# the first CPU calls start_kernel
447	je   1f
448	movl $(__KERNEL_PERCPU), %eax
449	movl %eax,%fs		# set this cpu's percpu
450	jmp initialize_secondary # all other CPUs call initialize_secondary
4511:
452#endif /* CONFIG_SMP */
453	jmp i386_start_kernel
454
455/*
456 * We depend on ET to be correct. This checks for 287/387.
457 */
458check_x87:
459	movb $0,X86_HARD_MATH
460	clts
461	fninit
462	fstsw %ax
463	cmpb $0,%al
464	je 1f
465	movl %cr0,%eax		/* no coprocessor: have to set bits */
466	xorl $4,%eax		/* set EM */
467	movl %eax,%cr0
468	ret
469	ALIGN
4701:	movb $1,X86_HARD_MATH
471	.byte 0xDB,0xE4		/* fsetpm for 287, ignored by 387 */
472	ret
473
474/*
475 *  setup_idt
476 *
477 *  sets up a idt with 256 entries pointing to
478 *  ignore_int, interrupt gates. It doesn't actually load
479 *  idt - that can be done only after paging has been enabled
480 *  and the kernel moved to PAGE_OFFSET. Interrupts
481 *  are enabled elsewhere, when we can be relatively
482 *  sure everything is ok.
483 *
484 *  Warning: %esi is live across this function.
485 */
486setup_idt:
487	lea ignore_int,%edx
488	movl $(__KERNEL_CS << 16),%eax
489	movw %dx,%ax		/* selector = 0x0010 = cs */
490	movw $0x8E00,%dx	/* interrupt gate - dpl=0, present */
491
492	lea idt_table,%edi
493	mov $256,%ecx
494rp_sidt:
495	movl %eax,(%edi)
496	movl %edx,4(%edi)
497	addl $8,%edi
498	dec %ecx
499	jne rp_sidt
500
501.macro	set_early_handler handler,trapno
502	lea \handler,%edx
503	movl $(__KERNEL_CS << 16),%eax
504	movw %dx,%ax
505	movw $0x8E00,%dx	/* interrupt gate - dpl=0, present */
506	lea idt_table,%edi
507	movl %eax,8*\trapno(%edi)
508	movl %edx,8*\trapno+4(%edi)
509.endm
510
511	set_early_handler handler=early_divide_err,trapno=0
512	set_early_handler handler=early_illegal_opcode,trapno=6
513	set_early_handler handler=early_protection_fault,trapno=13
514	set_early_handler handler=early_page_fault,trapno=14
515
516	ret
517
518early_divide_err:
519	xor %edx,%edx
520	pushl $0	/* fake errcode */
521	jmp early_fault
522
523early_illegal_opcode:
524	movl $6,%edx
525	pushl $0	/* fake errcode */
526	jmp early_fault
527
528early_protection_fault:
529	movl $13,%edx
530	jmp early_fault
531
532early_page_fault:
533	movl $14,%edx
534	jmp early_fault
535
536early_fault:
537	cld
538#ifdef CONFIG_PRINTK
539	pusha
540	movl $(__KERNEL_DS),%eax
541	movl %eax,%ds
542	movl %eax,%es
543	cmpl $2,early_recursion_flag
544	je hlt_loop
545	incl early_recursion_flag
546	movl %cr2,%eax
547	pushl %eax
548	pushl %edx		/* trapno */
549	pushl $fault_msg
550#ifdef CONFIG_EARLY_PRINTK
551	call early_printk
552#else
553	call printk
554#endif
555#endif
556	call dump_stack
557hlt_loop:
558	hlt
559	jmp hlt_loop
560
561/* This is the default interrupt "handler" :-) */
562	ALIGN
563ignore_int:
564	cld
565#ifdef CONFIG_PRINTK
566	pushl %eax
567	pushl %ecx
568	pushl %edx
569	pushl %es
570	pushl %ds
571	movl $(__KERNEL_DS),%eax
572	movl %eax,%ds
573	movl %eax,%es
574	cmpl $2,early_recursion_flag
575	je hlt_loop
576	incl early_recursion_flag
577	pushl 16(%esp)
578	pushl 24(%esp)
579	pushl 32(%esp)
580	pushl 40(%esp)
581	pushl $int_msg
582#ifdef CONFIG_EARLY_PRINTK
583	call early_printk
584#else
585	call printk
586#endif
587	addl $(5*4),%esp
588	popl %ds
589	popl %es
590	popl %edx
591	popl %ecx
592	popl %eax
593#endif
594	iret
595
596.section .text
597/*
598 * Real beginning of normal "text" segment
599 */
600ENTRY(stext)
601ENTRY(_stext)
602
603/*
604 * BSS section
605 */
606.section ".bss.page_aligned","wa"
607	.align PAGE_SIZE_asm
608#ifdef CONFIG_X86_PAE
609swapper_pg_pmd:
610	.fill 1024*KPMDS,4,0
611#else
612ENTRY(swapper_pg_dir)
613	.fill 1024,4,0
614#endif
615swapper_pg_fixmap:
616	.fill 1024,4,0
617ENTRY(empty_zero_page)
618	.fill 4096,1,0
619/*
620 * This starts the data section.
621 */
622#ifdef CONFIG_X86_PAE
623.section ".data.page_aligned","wa"
624	/* Page-aligned for the benefit of paravirt? */
625	.align PAGE_SIZE_asm
626ENTRY(swapper_pg_dir)
627	.long	pa(swapper_pg_pmd+PGD_ATTR),0		/* low identity map */
628# if KPMDS == 3
629	.long	pa(swapper_pg_pmd+PGD_ATTR),0
630	.long	pa(swapper_pg_pmd+PGD_ATTR+0x1000),0
631	.long	pa(swapper_pg_pmd+PGD_ATTR+0x2000),0
632# elif KPMDS == 2
633	.long	0,0
634	.long	pa(swapper_pg_pmd+PGD_ATTR),0
635	.long	pa(swapper_pg_pmd+PGD_ATTR+0x1000),0
636# elif KPMDS == 1
637	.long	0,0
638	.long	0,0
639	.long	pa(swapper_pg_pmd+PGD_ATTR),0
640# else
641#  error "Kernel PMDs should be 1, 2 or 3"
642# endif
643	.align PAGE_SIZE_asm		/* needs to be page-sized too */
644#endif
645
646.data
647ENTRY(stack_start)
648	.long init_thread_union+THREAD_SIZE
649	.long __BOOT_DS
650
651ready:	.byte 0
652
653early_recursion_flag:
654	.long 0
655
656int_msg:
657	.asciz "Unknown interrupt or fault at EIP %p %p %p\n"
658
659fault_msg:
660	.asciz								\
661/* fault info: */	"BUG: Int %d: CR2 %p\n"				\
662/* pusha regs: */	"     EDI %p  ESI %p  EBP %p  ESP %p\n"		\
663			"     EBX %p  EDX %p  ECX %p  EAX %p\n"		\
664/* fault frame: */	"     err %p  EIP %p   CS %p  flg %p\n"		\
665									\
666			"Stack: %p %p %p %p %p %p %p %p\n"		\
667			"       %p %p %p %p %p %p %p %p\n"		\
668			"       %p %p %p %p %p %p %p %p\n"
669
670#include "../../x86/xen/xen-head.S"
671
672/*
673 * The IDT and GDT 'descriptors' are a strange 48-bit object
674 * only used by the lidt and lgdt instructions. They are not
675 * like usual segment descriptors - they consist of a 16-bit
676 * segment size, and 32-bit linear address value:
677 */
678
679.globl boot_gdt_descr
680.globl idt_descr
681
682	ALIGN
683# early boot GDT descriptor (must use 1:1 address mapping)
684	.word 0				# 32 bit align gdt_desc.address
685boot_gdt_descr:
686	.word __BOOT_DS+7
687	.long boot_gdt - __PAGE_OFFSET
688
689	.word 0				# 32-bit align idt_desc.address
690idt_descr:
691	.word IDT_ENTRIES*8-1		# idt contains 256 entries
692	.long idt_table
693
694# boot GDT descriptor (later on used by CPU#0):
695	.word 0				# 32 bit align gdt_desc.address
696ENTRY(early_gdt_descr)
697	.word GDT_ENTRIES*8-1
698	.long per_cpu__gdt_page		/* Overwritten for secondary CPUs */
699
700/*
701 * The boot_gdt must mirror the equivalent in setup.S and is
702 * used only for booting.
703 */
704	.align L1_CACHE_BYTES
705ENTRY(boot_gdt)
706	.fill GDT_ENTRY_BOOT_CS,8,0
707	.quad 0x00cf9a000000ffff	/* kernel 4GB code at 0x00000000 */
708	.quad 0x00cf92000000ffff	/* kernel 4GB data at 0x00000000 */
709