xref: /openbmc/linux/arch/x86/kernel/head_32.S (revision 56a0eccd) 
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
392	/*
393	 * And make sure that all the mappings we set up have NX set from
394	 * the beginning.
395	 */
396	orl $(1 << (_PAGE_BIT_NX - 32)), pa(__supported_pte_mask + 4)
397
398enable_paging:
399
400/*
401 * Enable paging
402 */
403	movl $pa(initial_page_table), %eax
404	movl %eax,%cr3		/* set the page table pointer.. */
405	movl $CR0_STATE,%eax
406	movl %eax,%cr0		/* ..and set paging (PG) bit */
407	ljmp $__BOOT_CS,$1f	/* Clear prefetch and normalize %eip */
4081:
409	/* Shift the stack pointer to a virtual address */
410	addl $__PAGE_OFFSET, %esp
411
412/*
413 * start system 32-bit setup. We need to re-do some of the things done
414 * in 16-bit mode for the "real" operations.
415 */
416	movl setup_once_ref,%eax
417	andl %eax,%eax
418	jz 1f				# Did we do this already?
419	call *%eax
4201:
421
422/*
423 * Check if it is 486
424 */
425	movb $4,X86			# at least 486
426	cmpl $-1,X86_CPUID
427	je is486
428
429	/* get vendor info */
430	xorl %eax,%eax			# call CPUID with 0 -> return vendor ID
431	cpuid
432	movl %eax,X86_CPUID		# save CPUID level
433	movl %ebx,X86_VENDOR_ID		# lo 4 chars
434	movl %edx,X86_VENDOR_ID+4	# next 4 chars
435	movl %ecx,X86_VENDOR_ID+8	# last 4 chars
436
437	orl %eax,%eax			# do we have processor info as well?
438	je is486
439
440	movl $1,%eax		# Use the CPUID instruction to get CPU type
441	cpuid
442	movb %al,%cl		# save reg for future use
443	andb $0x0f,%ah		# mask processor family
444	movb %ah,X86
445	andb $0xf0,%al		# mask model
446	shrb $4,%al
447	movb %al,X86_MODEL
448	andb $0x0f,%cl		# mask mask revision
449	movb %cl,X86_MASK
450	movl %edx,X86_CAPABILITY
451
452is486:
453	movl $0x50022,%ecx	# set AM, WP, NE and MP
454	movl %cr0,%eax
455	andl $0x80000011,%eax	# Save PG,PE,ET
456	orl %ecx,%eax
457	movl %eax,%cr0
458
459	lgdt early_gdt_descr
460	lidt idt_descr
461	ljmp $(__KERNEL_CS),$1f
4621:	movl $(__KERNEL_DS),%eax	# reload all the segment registers
463	movl %eax,%ss			# after changing gdt.
464
465	movl $(__USER_DS),%eax		# DS/ES contains default USER segment
466	movl %eax,%ds
467	movl %eax,%es
468
469	movl $(__KERNEL_PERCPU), %eax
470	movl %eax,%fs			# set this cpu's percpu
471
472	movl $(__KERNEL_STACK_CANARY),%eax
473	movl %eax,%gs
474
475	xorl %eax,%eax			# Clear LDT
476	lldt %ax
477
478	pushl $0		# fake return address for unwinder
479	jmp *(initial_code)
480
481#include "verify_cpu.S"
482
483/*
484 *  setup_once
485 *
486 *  The setup work we only want to run on the BSP.
487 *
488 *  Warning: %esi is live across this function.
489 */
490__INIT
491setup_once:
492	/*
493	 * Set up a idt with 256 interrupt gates that push zero if there
494	 * is no error code and then jump to early_idt_handler_common.
495	 * It doesn't actually load the idt - that needs to be done on
496	 * each CPU. Interrupts are enabled elsewhere, when we can be
497	 * relatively sure everything is ok.
498	 */
499
500	movl $idt_table,%edi
501	movl $early_idt_handler_array,%eax
502	movl $NUM_EXCEPTION_VECTORS,%ecx
5031:
504	movl %eax,(%edi)
505	movl %eax,4(%edi)
506	/* interrupt gate, dpl=0, present */
507	movl $(0x8E000000 + __KERNEL_CS),2(%edi)
508	addl $EARLY_IDT_HANDLER_SIZE,%eax
509	addl $8,%edi
510	loop 1b
511
512	movl $256 - NUM_EXCEPTION_VECTORS,%ecx
513	movl $ignore_int,%edx
514	movl $(__KERNEL_CS << 16),%eax
515	movw %dx,%ax		/* selector = 0x0010 = cs */
516	movw $0x8E00,%dx	/* interrupt gate - dpl=0, present */
5172:
518	movl %eax,(%edi)
519	movl %edx,4(%edi)
520	addl $8,%edi
521	loop 2b
522
523#ifdef CONFIG_CC_STACKPROTECTOR
524	/*
525	 * Configure the stack canary. The linker can't handle this by
526	 * relocation.  Manually set base address in stack canary
527	 * segment descriptor.
528	 */
529	movl $gdt_page,%eax
530	movl $stack_canary,%ecx
531	movw %cx, 8 * GDT_ENTRY_STACK_CANARY + 2(%eax)
532	shrl $16, %ecx
533	movb %cl, 8 * GDT_ENTRY_STACK_CANARY + 4(%eax)
534	movb %ch, 8 * GDT_ENTRY_STACK_CANARY + 7(%eax)
535#endif
536
537	andl $0,setup_once_ref	/* Once is enough, thanks */
538	ret
539
540ENTRY(early_idt_handler_array)
541	# 36(%esp) %eflags
542	# 32(%esp) %cs
543	# 28(%esp) %eip
544	# 24(%rsp) error code
545	i = 0
546	.rept NUM_EXCEPTION_VECTORS
547	.ifeq (EXCEPTION_ERRCODE_MASK >> i) & 1
548	pushl $0		# Dummy error code, to make stack frame uniform
549	.endif
550	pushl $i		# 20(%esp) Vector number
551	jmp early_idt_handler_common
552	i = i + 1
553	.fill early_idt_handler_array + i*EARLY_IDT_HANDLER_SIZE - ., 1, 0xcc
554	.endr
555ENDPROC(early_idt_handler_array)
556
557early_idt_handler_common:
558	/*
559	 * The stack is the hardware frame, an error code or zero, and the
560	 * vector number.
561	 */
562	cld
563
564	cmpl $2,(%esp)		# X86_TRAP_NMI
565	je .Lis_nmi		# Ignore NMI
566
567	cmpl $2,%ss:early_recursion_flag
568	je hlt_loop
569	incl %ss:early_recursion_flag
570
571	push %eax		# 16(%esp)
572	push %ecx		# 12(%esp)
573	push %edx		#  8(%esp)
574	push %ds		#  4(%esp)
575	push %es		#  0(%esp)
576	movl $(__KERNEL_DS),%eax
577	movl %eax,%ds
578	movl %eax,%es
579
580	cmpl $(__KERNEL_CS),32(%esp)
581	jne 10f
582
583	leal 28(%esp),%eax	# Pointer to %eip
584	call early_fixup_exception
585	andl %eax,%eax
586	jnz ex_entry		/* found an exception entry */
587
58810:
589#ifdef CONFIG_PRINTK
590	xorl %eax,%eax
591	movw %ax,2(%esp)	/* clean up the segment values on some cpus */
592	movw %ax,6(%esp)
593	movw %ax,34(%esp)
594	leal  40(%esp),%eax
595	pushl %eax		/* %esp before the exception */
596	pushl %ebx
597	pushl %ebp
598	pushl %esi
599	pushl %edi
600	movl %cr2,%eax
601	pushl %eax
602	pushl (20+6*4)(%esp)	/* trapno */
603	pushl $fault_msg
604	call printk
605#endif
606	call dump_stack
607hlt_loop:
608	hlt
609	jmp hlt_loop
610
611ex_entry:
612	pop %es
613	pop %ds
614	pop %edx
615	pop %ecx
616	pop %eax
617	decl %ss:early_recursion_flag
618.Lis_nmi:
619	addl $8,%esp		/* drop vector number and error code */
620	iret
621ENDPROC(early_idt_handler_common)
622
623/* This is the default interrupt "handler" :-) */
624	ALIGN
625ignore_int:
626	cld
627#ifdef CONFIG_PRINTK
628	pushl %eax
629	pushl %ecx
630	pushl %edx
631	pushl %es
632	pushl %ds
633	movl $(__KERNEL_DS),%eax
634	movl %eax,%ds
635	movl %eax,%es
636	cmpl $2,early_recursion_flag
637	je hlt_loop
638	incl early_recursion_flag
639	pushl 16(%esp)
640	pushl 24(%esp)
641	pushl 32(%esp)
642	pushl 40(%esp)
643	pushl $int_msg
644	call printk
645
646	call dump_stack
647
648	addl $(5*4),%esp
649	popl %ds
650	popl %es
651	popl %edx
652	popl %ecx
653	popl %eax
654#endif
655	iret
656ENDPROC(ignore_int)
657__INITDATA
658	.align 4
659early_recursion_flag:
660	.long 0
661
662__REFDATA
663	.align 4
664ENTRY(initial_code)
665	.long i386_start_kernel
666ENTRY(setup_once_ref)
667	.long setup_once
668
669/*
670 * BSS section
671 */
672__PAGE_ALIGNED_BSS
673	.align PAGE_SIZE
674#ifdef CONFIG_X86_PAE
675initial_pg_pmd:
676	.fill 1024*KPMDS,4,0
677#else
678ENTRY(initial_page_table)
679	.fill 1024,4,0
680#endif
681initial_pg_fixmap:
682	.fill 1024,4,0
683ENTRY(empty_zero_page)
684	.fill 4096,1,0
685ENTRY(swapper_pg_dir)
686	.fill 1024,4,0
687
688/*
689 * This starts the data section.
690 */
691#ifdef CONFIG_X86_PAE
692__PAGE_ALIGNED_DATA
693	/* Page-aligned for the benefit of paravirt? */
694	.align PAGE_SIZE
695ENTRY(initial_page_table)
696	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR),0	/* low identity map */
697# if KPMDS == 3
698	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR),0
699	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR+0x1000),0
700	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR+0x2000),0
701# elif KPMDS == 2
702	.long	0,0
703	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR),0
704	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR+0x1000),0
705# elif KPMDS == 1
706	.long	0,0
707	.long	0,0
708	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR),0
709# else
710#  error "Kernel PMDs should be 1, 2 or 3"
711# endif
712	.align PAGE_SIZE		/* needs to be page-sized too */
713#endif
714
715.data
716.balign 4
717ENTRY(stack_start)
718	.long init_thread_union+THREAD_SIZE
719
720__INITRODATA
721int_msg:
722	.asciz "Unknown interrupt or fault at: %p %p %p\n"
723
724fault_msg:
725/* fault info: */
726	.ascii "BUG: Int %d: CR2 %p\n"
727/* regs pushed in early_idt_handler: */
728	.ascii "     EDI %p  ESI %p  EBP %p  EBX %p\n"
729	.ascii "     ESP %p   ES %p   DS %p\n"
730	.ascii "     EDX %p  ECX %p  EAX %p\n"
731/* fault frame: */
732	.ascii "     vec %p  err %p  EIP %p   CS %p  flg %p\n"
733	.ascii "Stack: %p %p %p %p %p %p %p %p\n"
734	.ascii "       %p %p %p %p %p %p %p %p\n"
735	.asciz "       %p %p %p %p %p %p %p %p\n"
736
737#include "../../x86/xen/xen-head.S"
738
739/*
740 * The IDT and GDT 'descriptors' are a strange 48-bit object
741 * only used by the lidt and lgdt instructions. They are not
742 * like usual segment descriptors - they consist of a 16-bit
743 * segment size, and 32-bit linear address value:
744 */
745
746	.data
747.globl boot_gdt_descr
748.globl idt_descr
749
750	ALIGN
751# early boot GDT descriptor (must use 1:1 address mapping)
752	.word 0				# 32 bit align gdt_desc.address
753boot_gdt_descr:
754	.word __BOOT_DS+7
755	.long boot_gdt - __PAGE_OFFSET
756
757	.word 0				# 32-bit align idt_desc.address
758idt_descr:
759	.word IDT_ENTRIES*8-1		# idt contains 256 entries
760	.long idt_table
761
762# boot GDT descriptor (later on used by CPU#0):
763	.word 0				# 32 bit align gdt_desc.address
764ENTRY(early_gdt_descr)
765	.word GDT_ENTRIES*8-1
766	.long gdt_page			/* Overwritten for secondary CPUs */
767
768/*
769 * The boot_gdt must mirror the equivalent in setup.S and is
770 * used only for booting.
771 */
772	.align L1_CACHE_BYTES
773ENTRY(boot_gdt)
774	.fill GDT_ENTRY_BOOT_CS,8,0
775	.quad 0x00cf9a000000ffff	/* kernel 4GB code at 0x00000000 */
776	.quad 0x00cf92000000ffff	/* kernel 4GB data at 0x00000000 */
777