xref: /linux/arch/x86/kernel/head_32.S (revision b6ebbac51bedf9e98e837688bc838f400196da5e) 
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/cpufeatures.h>
23#include <asm/percpu.h>
24#include <asm/nops.h>
25#include <asm/bootparam.h>
26
27/* Physical address */
28#define pa(X) ((X) - __PAGE_OFFSET)
29
30/*
31 * References to members of the new_cpu_data structure.
32 */
33
34#define X86		new_cpu_data+CPUINFO_x86
35#define X86_VENDOR	new_cpu_data+CPUINFO_x86_vendor
36#define X86_MODEL	new_cpu_data+CPUINFO_x86_model
37#define X86_MASK	new_cpu_data+CPUINFO_x86_mask
38#define X86_HARD_MATH	new_cpu_data+CPUINFO_hard_math
39#define X86_CPUID	new_cpu_data+CPUINFO_cpuid_level
40#define X86_CAPABILITY	new_cpu_data+CPUINFO_x86_capability
41#define X86_VENDOR_ID	new_cpu_data+CPUINFO_x86_vendor_id
42
43/*
44 * This is how much memory in addition to the memory covered up to
45 * and including _end we need mapped initially.
46 * We need:
47 *     (KERNEL_IMAGE_SIZE/4096) / 1024 pages (worst case, non PAE)
48 *     (KERNEL_IMAGE_SIZE/4096) / 512 + 4 pages (worst case for PAE)
49 *
50 * Modulo rounding, each megabyte assigned here requires a kilobyte of
51 * memory, which is currently unreclaimed.
52 *
53 * This should be a multiple of a page.
54 *
55 * KERNEL_IMAGE_SIZE should be greater than pa(_end)
56 * and small than max_low_pfn, otherwise will waste some page table entries
57 */
58
59#if PTRS_PER_PMD > 1
60#define PAGE_TABLE_SIZE(pages) (((pages) / PTRS_PER_PMD) + PTRS_PER_PGD)
61#else
62#define PAGE_TABLE_SIZE(pages) ((pages) / PTRS_PER_PGD)
63#endif
64
65/*
66 * Number of possible pages in the lowmem region.
67 *
68 * We shift 2 by 31 instead of 1 by 32 to the left in order to avoid a
69 * gas warning about overflowing shift count when gas has been compiled
70 * with only a host target support using a 32-bit type for internal
71 * representation.
72 */
73LOWMEM_PAGES = (((2<<31) - __PAGE_OFFSET) >> PAGE_SHIFT)
74
75/* Enough space to fit pagetables for the low memory linear map */
76MAPPING_BEYOND_END = PAGE_TABLE_SIZE(LOWMEM_PAGES) << PAGE_SHIFT
77
78/*
79 * Worst-case size of the kernel mapping we need to make:
80 * a relocatable kernel can live anywhere in lowmem, so we need to be able
81 * to map all of lowmem.
82 */
83KERNEL_PAGES = LOWMEM_PAGES
84
85INIT_MAP_SIZE = PAGE_TABLE_SIZE(KERNEL_PAGES) * PAGE_SIZE
86RESERVE_BRK(pagetables, INIT_MAP_SIZE)
87
88/*
89 * 32-bit kernel entrypoint; only used by the boot CPU.  On entry,
90 * %esi points to the real-mode code as a 32-bit pointer.
91 * CS and DS must be 4 GB flat segments, but we don't depend on
92 * any particular GDT layout, because we load our own as soon as we
93 * can.
94 */
95__HEAD
96ENTRY(startup_32)
97	movl pa(stack_start),%ecx
98
99	/* test KEEP_SEGMENTS flag to see if the bootloader is asking
100		us to not reload segments */
101	testb $KEEP_SEGMENTS, BP_loadflags(%esi)
102	jnz 2f
103
104/*
105 * Set segments to known values.
106 */
107	lgdt pa(boot_gdt_descr)
108	movl $(__BOOT_DS),%eax
109	movl %eax,%ds
110	movl %eax,%es
111	movl %eax,%fs
112	movl %eax,%gs
113	movl %eax,%ss
1142:
115	leal -__PAGE_OFFSET(%ecx),%esp
116
117/*
118 * Clear BSS first so that there are no surprises...
119 */
120	cld
121	xorl %eax,%eax
122	movl $pa(__bss_start),%edi
123	movl $pa(__bss_stop),%ecx
124	subl %edi,%ecx
125	shrl $2,%ecx
126	rep ; stosl
127/*
128 * Copy bootup parameters out of the way.
129 * Note: %esi still has the pointer to the real-mode data.
130 * With the kexec as boot loader, parameter segment might be loaded beyond
131 * kernel image and might not even be addressable by early boot page tables.
132 * (kexec on panic case). Hence copy out the parameters before initializing
133 * page tables.
134 */
135	movl $pa(boot_params),%edi
136	movl $(PARAM_SIZE/4),%ecx
137	cld
138	rep
139	movsl
140	movl pa(boot_params) + NEW_CL_POINTER,%esi
141	andl %esi,%esi
142	jz 1f			# No command line
143	movl $pa(boot_command_line),%edi
144	movl $(COMMAND_LINE_SIZE/4),%ecx
145	rep
146	movsl
1471:
148
149#ifdef CONFIG_OLPC
150	/* save OFW's pgdir table for later use when calling into OFW */
151	movl %cr3, %eax
152	movl %eax, pa(olpc_ofw_pgd)
153#endif
154
155#ifdef CONFIG_MICROCODE
156	/* Early load ucode on BSP. */
157	call load_ucode_bsp
158#endif
159
160/*
161 * Initialize page tables.  This creates a PDE and a set of page
162 * tables, which are located immediately beyond __brk_base.  The variable
163 * _brk_end is set up to point to the first "safe" location.
164 * Mappings are created both at virtual address 0 (identity mapping)
165 * and PAGE_OFFSET for up to _end.
166 */
167#ifdef CONFIG_X86_PAE
168
169	/*
170	 * In PAE mode initial_page_table is statically defined to contain
171	 * enough entries to cover the VMSPLIT option (that is the top 1, 2 or 3
172	 * entries). The identity mapping is handled by pointing two PGD entries
173	 * to the first kernel PMD.
174	 *
175	 * Note the upper half of each PMD or PTE are always zero at this stage.
176	 */
177
178#define KPMDS (((-__PAGE_OFFSET) >> 30) & 3) /* Number of kernel PMDs */
179
180	xorl %ebx,%ebx				/* %ebx is kept at zero */
181
182	movl $pa(__brk_base), %edi
183	movl $pa(initial_pg_pmd), %edx
184	movl $PTE_IDENT_ATTR, %eax
18510:
186	leal PDE_IDENT_ATTR(%edi),%ecx		/* Create PMD entry */
187	movl %ecx,(%edx)			/* Store PMD entry */
188						/* Upper half already zero */
189	addl $8,%edx
190	movl $512,%ecx
19111:
192	stosl
193	xchgl %eax,%ebx
194	stosl
195	xchgl %eax,%ebx
196	addl $0x1000,%eax
197	loop 11b
198
199	/*
200	 * End condition: we must map up to the end + MAPPING_BEYOND_END.
201	 */
202	movl $pa(_end) + MAPPING_BEYOND_END + PTE_IDENT_ATTR, %ebp
203	cmpl %ebp,%eax
204	jb 10b
2051:
206	addl $__PAGE_OFFSET, %edi
207	movl %edi, pa(_brk_end)
208	shrl $12, %eax
209	movl %eax, pa(max_pfn_mapped)
210
211	/* Do early initialization of the fixmap area */
212	movl $pa(initial_pg_fixmap)+PDE_IDENT_ATTR,%eax
213	movl %eax,pa(initial_pg_pmd+0x1000*KPMDS-8)
214#else	/* Not PAE */
215
216page_pde_offset = (__PAGE_OFFSET >> 20);
217
218	movl $pa(__brk_base), %edi
219	movl $pa(initial_page_table), %edx
220	movl $PTE_IDENT_ATTR, %eax
22110:
222	leal PDE_IDENT_ATTR(%edi),%ecx		/* Create PDE entry */
223	movl %ecx,(%edx)			/* Store identity PDE entry */
224	movl %ecx,page_pde_offset(%edx)		/* Store kernel PDE entry */
225	addl $4,%edx
226	movl $1024, %ecx
22711:
228	stosl
229	addl $0x1000,%eax
230	loop 11b
231	/*
232	 * End condition: we must map up to the end + MAPPING_BEYOND_END.
233	 */
234	movl $pa(_end) + MAPPING_BEYOND_END + PTE_IDENT_ATTR, %ebp
235	cmpl %ebp,%eax
236	jb 10b
237	addl $__PAGE_OFFSET, %edi
238	movl %edi, pa(_brk_end)
239	shrl $12, %eax
240	movl %eax, pa(max_pfn_mapped)
241
242	/* Do early initialization of the fixmap area */
243	movl $pa(initial_pg_fixmap)+PDE_IDENT_ATTR,%eax
244	movl %eax,pa(initial_page_table+0xffc)
245#endif
246
247#ifdef CONFIG_PARAVIRT
248	/* This is can only trip for a broken bootloader... */
249	cmpw $0x207, pa(boot_params + BP_version)
250	jb default_entry
251
252	/* Paravirt-compatible boot parameters.  Look to see what architecture
253		we're booting under. */
254	movl pa(boot_params + BP_hardware_subarch), %eax
255	cmpl $num_subarch_entries, %eax
256	jae bad_subarch
257
258	movl pa(subarch_entries)(,%eax,4), %eax
259	subl $__PAGE_OFFSET, %eax
260	jmp *%eax
261
262bad_subarch:
263WEAK(lguest_entry)
264WEAK(xen_entry)
265	/* Unknown implementation; there's really
266	   nothing we can do at this point. */
267	ud2a
268
269	__INITDATA
270
271subarch_entries:
272	.long default_entry		/* normal x86/PC */
273	.long lguest_entry		/* lguest hypervisor */
274	.long xen_entry			/* Xen hypervisor */
275	.long default_entry		/* Moorestown MID */
276num_subarch_entries = (. - subarch_entries) / 4
277.previous
278#else
279	jmp default_entry
280#endif /* CONFIG_PARAVIRT */
281
282#ifdef CONFIG_HOTPLUG_CPU
283/*
284 * Boot CPU0 entry point. It's called from play_dead(). Everything has been set
285 * up already except stack. We just set up stack here. Then call
286 * start_secondary().
287 */
288ENTRY(start_cpu0)
289	movl stack_start, %ecx
290	movl %ecx, %esp
291	jmp  *(initial_code)
292ENDPROC(start_cpu0)
293#endif
294
295/*
296 * Non-boot CPU entry point; entered from trampoline.S
297 * We can't lgdt here, because lgdt itself uses a data segment, but
298 * we know the trampoline has already loaded the boot_gdt for us.
299 *
300 * If cpu hotplug is not supported then this code can go in init section
301 * which will be freed later
302 */
303ENTRY(startup_32_smp)
304	cld
305	movl $(__BOOT_DS),%eax
306	movl %eax,%ds
307	movl %eax,%es
308	movl %eax,%fs
309	movl %eax,%gs
310	movl pa(stack_start),%ecx
311	movl %eax,%ss
312	leal -__PAGE_OFFSET(%ecx),%esp
313
314#ifdef CONFIG_MICROCODE
315	/* Early load ucode on AP. */
316	call load_ucode_ap
317#endif
318
319default_entry:
320#define CR0_STATE	(X86_CR0_PE | X86_CR0_MP | X86_CR0_ET | \
321			 X86_CR0_NE | X86_CR0_WP | X86_CR0_AM | \
322			 X86_CR0_PG)
323	movl $(CR0_STATE & ~X86_CR0_PG),%eax
324	movl %eax,%cr0
325
326/*
327 * We want to start out with EFLAGS unambiguously cleared. Some BIOSes leave
328 * bits like NT set. This would confuse the debugger if this code is traced. So
329 * initialize them properly now before switching to protected mode. That means
330 * DF in particular (even though we have cleared it earlier after copying the
331 * command line) because GCC expects it.
332 */
333	pushl $0
334	popfl
335
336/*
337 * New page tables may be in 4Mbyte page mode and may be using the global pages.
338 *
339 * NOTE! If we are on a 486 we may have no cr4 at all! Specifically, cr4 exists
340 * if and only if CPUID exists and has flags other than the FPU flag set.
341 */
342	movl $-1,pa(X86_CPUID)		# preset CPUID level
343	movl $X86_EFLAGS_ID,%ecx
344	pushl %ecx
345	popfl				# set EFLAGS=ID
346	pushfl
347	popl %eax			# get EFLAGS
348	testl $X86_EFLAGS_ID,%eax	# did EFLAGS.ID remained set?
349	jz enable_paging		# hw disallowed setting of ID bit
350					# which means no CPUID and no CR4
351
352	xorl %eax,%eax
353	cpuid
354	movl %eax,pa(X86_CPUID)		# save largest std CPUID function
355
356	movl $1,%eax
357	cpuid
358	andl $~1,%edx			# Ignore CPUID.FPU
359	jz enable_paging		# No flags or only CPUID.FPU = no CR4
360
361	movl pa(mmu_cr4_features),%eax
362	movl %eax,%cr4
363
364	testb $X86_CR4_PAE, %al		# check if PAE is enabled
365	jz enable_paging
366
367	/* Check if extended functions are implemented */
368	movl $0x80000000, %eax
369	cpuid
370	/* Value must be in the range 0x80000001 to 0x8000ffff */
371	subl $0x80000001, %eax
372	cmpl $(0x8000ffff-0x80000001), %eax
373	ja enable_paging
374
375	/* Clear bogus XD_DISABLE bits */
376	call verify_cpu
377
378	mov $0x80000001, %eax
379	cpuid
380	/* Execute Disable bit supported? */
381	btl $(X86_FEATURE_NX & 31), %edx
382	jnc enable_paging
383
384	/* Setup EFER (Extended Feature Enable Register) */
385	movl $MSR_EFER, %ecx
386	rdmsr
387
388	btsl $_EFER_NX, %eax
389	/* Make changes effective */
390	wrmsr
391
392enable_paging:
393
394/*
395 * Enable paging
396 */
397	movl $pa(initial_page_table), %eax
398	movl %eax,%cr3		/* set the page table pointer.. */
399	movl $CR0_STATE,%eax
400	movl %eax,%cr0		/* ..and set paging (PG) bit */
401	ljmp $__BOOT_CS,$1f	/* Clear prefetch and normalize %eip */
4021:
403	/* Shift the stack pointer to a virtual address */
404	addl $__PAGE_OFFSET, %esp
405
406/*
407 * start system 32-bit setup. We need to re-do some of the things done
408 * in 16-bit mode for the "real" operations.
409 */
410	movl setup_once_ref,%eax
411	andl %eax,%eax
412	jz 1f				# Did we do this already?
413	call *%eax
4141:
415
416/*
417 * Check if it is 486
418 */
419	movb $4,X86			# at least 486
420	cmpl $-1,X86_CPUID
421	je is486
422
423	/* get vendor info */
424	xorl %eax,%eax			# call CPUID with 0 -> return vendor ID
425	cpuid
426	movl %eax,X86_CPUID		# save CPUID level
427	movl %ebx,X86_VENDOR_ID		# lo 4 chars
428	movl %edx,X86_VENDOR_ID+4	# next 4 chars
429	movl %ecx,X86_VENDOR_ID+8	# last 4 chars
430
431	orl %eax,%eax			# do we have processor info as well?
432	je is486
433
434	movl $1,%eax		# Use the CPUID instruction to get CPU type
435	cpuid
436	movb %al,%cl		# save reg for future use
437	andb $0x0f,%ah		# mask processor family
438	movb %ah,X86
439	andb $0xf0,%al		# mask model
440	shrb $4,%al
441	movb %al,X86_MODEL
442	andb $0x0f,%cl		# mask mask revision
443	movb %cl,X86_MASK
444	movl %edx,X86_CAPABILITY
445
446is486:
447	movl $0x50022,%ecx	# set AM, WP, NE and MP
448	movl %cr0,%eax
449	andl $0x80000011,%eax	# Save PG,PE,ET
450	orl %ecx,%eax
451	movl %eax,%cr0
452
453	lgdt early_gdt_descr
454	lidt idt_descr
455	ljmp $(__KERNEL_CS),$1f
4561:	movl $(__KERNEL_DS),%eax	# reload all the segment registers
457	movl %eax,%ss			# after changing gdt.
458
459	movl $(__USER_DS),%eax		# DS/ES contains default USER segment
460	movl %eax,%ds
461	movl %eax,%es
462
463	movl $(__KERNEL_PERCPU), %eax
464	movl %eax,%fs			# set this cpu's percpu
465
466	movl $(__KERNEL_STACK_CANARY),%eax
467	movl %eax,%gs
468
469	xorl %eax,%eax			# Clear LDT
470	lldt %ax
471
472	pushl $0		# fake return address for unwinder
473	jmp *(initial_code)
474
475#include "verify_cpu.S"
476
477/*
478 *  setup_once
479 *
480 *  The setup work we only want to run on the BSP.
481 *
482 *  Warning: %esi is live across this function.
483 */
484__INIT
485setup_once:
486	/*
487	 * Set up a idt with 256 interrupt gates that push zero if there
488	 * is no error code and then jump to early_idt_handler_common.
489	 * It doesn't actually load the idt - that needs to be done on
490	 * each CPU. Interrupts are enabled elsewhere, when we can be
491	 * relatively sure everything is ok.
492	 */
493
494	movl $idt_table,%edi
495	movl $early_idt_handler_array,%eax
496	movl $NUM_EXCEPTION_VECTORS,%ecx
4971:
498	movl %eax,(%edi)
499	movl %eax,4(%edi)
500	/* interrupt gate, dpl=0, present */
501	movl $(0x8E000000 + __KERNEL_CS),2(%edi)
502	addl $EARLY_IDT_HANDLER_SIZE,%eax
503	addl $8,%edi
504	loop 1b
505
506	movl $256 - NUM_EXCEPTION_VECTORS,%ecx
507	movl $ignore_int,%edx
508	movl $(__KERNEL_CS << 16),%eax
509	movw %dx,%ax		/* selector = 0x0010 = cs */
510	movw $0x8E00,%dx	/* interrupt gate - dpl=0, present */
5112:
512	movl %eax,(%edi)
513	movl %edx,4(%edi)
514	addl $8,%edi
515	loop 2b
516
517#ifdef CONFIG_CC_STACKPROTECTOR
518	/*
519	 * Configure the stack canary. The linker can't handle this by
520	 * relocation.  Manually set base address in stack canary
521	 * segment descriptor.
522	 */
523	movl $gdt_page,%eax
524	movl $stack_canary,%ecx
525	movw %cx, 8 * GDT_ENTRY_STACK_CANARY + 2(%eax)
526	shrl $16, %ecx
527	movb %cl, 8 * GDT_ENTRY_STACK_CANARY + 4(%eax)
528	movb %ch, 8 * GDT_ENTRY_STACK_CANARY + 7(%eax)
529#endif
530
531	andl $0,setup_once_ref	/* Once is enough, thanks */
532	ret
533
534ENTRY(early_idt_handler_array)
535	# 36(%esp) %eflags
536	# 32(%esp) %cs
537	# 28(%esp) %eip
538	# 24(%rsp) error code
539	i = 0
540	.rept NUM_EXCEPTION_VECTORS
541	.ifeq (EXCEPTION_ERRCODE_MASK >> i) & 1
542	pushl $0		# Dummy error code, to make stack frame uniform
543	.endif
544	pushl $i		# 20(%esp) Vector number
545	jmp early_idt_handler_common
546	i = i + 1
547	.fill early_idt_handler_array + i*EARLY_IDT_HANDLER_SIZE - ., 1, 0xcc
548	.endr
549ENDPROC(early_idt_handler_array)
550
551early_idt_handler_common:
552	/*
553	 * The stack is the hardware frame, an error code or zero, and the
554	 * vector number.
555	 */
556	cld
557
558	incl %ss:early_recursion_flag
559
560	/* The vector number is in pt_regs->gs */
561
562	cld
563	pushl	%fs		/* pt_regs->fs */
564	movw	$0, 2(%esp)	/* clear high bits (some CPUs leave garbage) */
565	pushl	%es		/* pt_regs->es */
566	movw	$0, 2(%esp)	/* clear high bits (some CPUs leave garbage) */
567	pushl	%ds		/* pt_regs->ds */
568	movw	$0, 2(%esp)	/* clear high bits (some CPUs leave garbage) */
569	pushl	%eax		/* pt_regs->ax */
570	pushl	%ebp		/* pt_regs->bp */
571	pushl	%edi		/* pt_regs->di */
572	pushl	%esi		/* pt_regs->si */
573	pushl	%edx		/* pt_regs->dx */
574	pushl	%ecx		/* pt_regs->cx */
575	pushl	%ebx		/* pt_regs->bx */
576
577	/* Fix up DS and ES */
578	movl	$(__KERNEL_DS), %ecx
579	movl	%ecx, %ds
580	movl	%ecx, %es
581
582	/* Load the vector number into EDX */
583	movl	PT_GS(%esp), %edx
584
585	/* Load GS into pt_regs->gs and clear high bits */
586	movw	%gs, PT_GS(%esp)
587	movw	$0, PT_GS+2(%esp)
588
589	movl	%esp, %eax	/* args are pt_regs (EAX), trapnr (EDX) */
590	call	early_fixup_exception
591
592	popl	%ebx		/* pt_regs->bx */
593	popl	%ecx		/* pt_regs->cx */
594	popl	%edx		/* pt_regs->dx */
595	popl	%esi		/* pt_regs->si */
596	popl	%edi		/* pt_regs->di */
597	popl	%ebp		/* pt_regs->bp */
598	popl	%eax		/* pt_regs->ax */
599	popl	%ds		/* pt_regs->ds */
600	popl	%es		/* pt_regs->es */
601	popl	%fs		/* pt_regs->fs */
602	popl	%gs		/* pt_regs->gs */
603	decl	%ss:early_recursion_flag
604	addl	$4, %esp	/* pop pt_regs->orig_ax */
605	iret
606ENDPROC(early_idt_handler_common)
607
608/* This is the default interrupt "handler" :-) */
609	ALIGN
610ignore_int:
611	cld
612#ifdef CONFIG_PRINTK
613	pushl %eax
614	pushl %ecx
615	pushl %edx
616	pushl %es
617	pushl %ds
618	movl $(__KERNEL_DS),%eax
619	movl %eax,%ds
620	movl %eax,%es
621	cmpl $2,early_recursion_flag
622	je hlt_loop
623	incl early_recursion_flag
624	pushl 16(%esp)
625	pushl 24(%esp)
626	pushl 32(%esp)
627	pushl 40(%esp)
628	pushl $int_msg
629	call printk
630
631	call dump_stack
632
633	addl $(5*4),%esp
634	popl %ds
635	popl %es
636	popl %edx
637	popl %ecx
638	popl %eax
639#endif
640	iret
641
642hlt_loop:
643	hlt
644	jmp hlt_loop
645ENDPROC(ignore_int)
646__INITDATA
647	.align 4
648GLOBAL(early_recursion_flag)
649	.long 0
650
651__REFDATA
652	.align 4
653ENTRY(initial_code)
654	.long i386_start_kernel
655ENTRY(setup_once_ref)
656	.long setup_once
657
658/*
659 * BSS section
660 */
661__PAGE_ALIGNED_BSS
662	.align PAGE_SIZE
663#ifdef CONFIG_X86_PAE
664initial_pg_pmd:
665	.fill 1024*KPMDS,4,0
666#else
667ENTRY(initial_page_table)
668	.fill 1024,4,0
669#endif
670initial_pg_fixmap:
671	.fill 1024,4,0
672ENTRY(empty_zero_page)
673	.fill 4096,1,0
674ENTRY(swapper_pg_dir)
675	.fill 1024,4,0
676
677/*
678 * This starts the data section.
679 */
680#ifdef CONFIG_X86_PAE
681__PAGE_ALIGNED_DATA
682	/* Page-aligned for the benefit of paravirt? */
683	.align PAGE_SIZE
684ENTRY(initial_page_table)
685	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR),0	/* low identity map */
686# if KPMDS == 3
687	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR),0
688	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR+0x1000),0
689	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR+0x2000),0
690# elif KPMDS == 2
691	.long	0,0
692	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR),0
693	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR+0x1000),0
694# elif KPMDS == 1
695	.long	0,0
696	.long	0,0
697	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR),0
698# else
699#  error "Kernel PMDs should be 1, 2 or 3"
700# endif
701	.align PAGE_SIZE		/* needs to be page-sized too */
702#endif
703
704.data
705.balign 4
706ENTRY(stack_start)
707	.long init_thread_union+THREAD_SIZE
708
709__INITRODATA
710int_msg:
711	.asciz "Unknown interrupt or fault at: %p %p %p\n"
712
713#include "../../x86/xen/xen-head.S"
714
715/*
716 * The IDT and GDT 'descriptors' are a strange 48-bit object
717 * only used by the lidt and lgdt instructions. They are not
718 * like usual segment descriptors - they consist of a 16-bit
719 * segment size, and 32-bit linear address value:
720 */
721
722	.data
723.globl boot_gdt_descr
724.globl idt_descr
725
726	ALIGN
727# early boot GDT descriptor (must use 1:1 address mapping)
728	.word 0				# 32 bit align gdt_desc.address
729boot_gdt_descr:
730	.word __BOOT_DS+7
731	.long boot_gdt - __PAGE_OFFSET
732
733	.word 0				# 32-bit align idt_desc.address
734idt_descr:
735	.word IDT_ENTRIES*8-1		# idt contains 256 entries
736	.long idt_table
737
738# boot GDT descriptor (later on used by CPU#0):
739	.word 0				# 32 bit align gdt_desc.address
740ENTRY(early_gdt_descr)
741	.word GDT_ENTRIES*8-1
742	.long gdt_page			/* Overwritten for secondary CPUs */
743
744/*
745 * The boot_gdt must mirror the equivalent in setup.S and is
746 * used only for booting.
747 */
748	.align L1_CACHE_BYTES
749ENTRY(boot_gdt)
750	.fill GDT_ENTRY_BOOT_CS,8,0
751	.quad 0x00cf9a000000ffff	/* kernel 4GB code at 0x00000000 */
752	.quad 0x00cf92000000ffff	/* kernel 4GB data at 0x00000000 */
753