xref: /linux/arch/x86/kernel/head_32.S (revision c80544dc0b87bb65038355e7aafdc30be16b26ab) 
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/linkage.h>
13#include <asm/segment.h>
14#include <asm/page.h>
15#include <asm/pgtable.h>
16#include <asm/desc.h>
17#include <asm/cache.h>
18#include <asm/thread_info.h>
19#include <asm/asm-offsets.h>
20#include <asm/setup.h>
21
22/*
23 * References to members of the new_cpu_data structure.
24 */
25
26#define X86		new_cpu_data+CPUINFO_x86
27#define X86_VENDOR	new_cpu_data+CPUINFO_x86_vendor
28#define X86_MODEL	new_cpu_data+CPUINFO_x86_model
29#define X86_MASK	new_cpu_data+CPUINFO_x86_mask
30#define X86_HARD_MATH	new_cpu_data+CPUINFO_hard_math
31#define X86_CPUID	new_cpu_data+CPUINFO_cpuid_level
32#define X86_CAPABILITY	new_cpu_data+CPUINFO_x86_capability
33#define X86_VENDOR_ID	new_cpu_data+CPUINFO_x86_vendor_id
34
35/*
36 * This is how much memory *in addition to the memory covered up to
37 * and including _end* we need mapped initially.
38 * We need:
39 *  - one bit for each possible page, but only in low memory, which means
40 *     2^32/4096/8 = 128K worst case (4G/4G split.)
41 *  - enough space to map all low memory, which means
42 *     (2^32/4096) / 1024 pages (worst case, non PAE)
43 *     (2^32/4096) / 512 + 4 pages (worst case for PAE)
44 *  - a few pages for allocator use before the kernel pagetable has
45 *     been set up
46 *
47 * Modulo rounding, each megabyte assigned here requires a kilobyte of
48 * memory, which is currently unreclaimed.
49 *
50 * This should be a multiple of a page.
51 */
52LOW_PAGES = 1<<(32-PAGE_SHIFT_asm)
53
54/*
55 * To preserve the DMA pool in PAGEALLOC kernels, we'll allocate
56 * pagetables from above the 16MB DMA limit, so we'll have to set
57 * up pagetables 16MB more (worst-case):
58 */
59#ifdef CONFIG_DEBUG_PAGEALLOC
60LOW_PAGES = LOW_PAGES + 0x1000000
61#endif
62
63#if PTRS_PER_PMD > 1
64PAGE_TABLE_SIZE = (LOW_PAGES / PTRS_PER_PMD) + PTRS_PER_PGD
65#else
66PAGE_TABLE_SIZE = (LOW_PAGES / PTRS_PER_PGD)
67#endif
68BOOTBITMAP_SIZE = LOW_PAGES / 8
69ALLOCATOR_SLOP = 4
70
71INIT_MAP_BEYOND_END = BOOTBITMAP_SIZE + (PAGE_TABLE_SIZE + ALLOCATOR_SLOP)*PAGE_SIZE_asm
72
73/*
74 * 32-bit kernel entrypoint; only used by the boot CPU.  On entry,
75 * %esi points to the real-mode code as a 32-bit pointer.
76 * CS and DS must be 4 GB flat segments, but we don't depend on
77 * any particular GDT layout, because we load our own as soon as we
78 * can.
79 */
80.section .text.head,"ax",@progbits
81ENTRY(startup_32)
82
83/*
84 * Set segments to known values.
85 */
86	cld
87	lgdt boot_gdt_descr - __PAGE_OFFSET
88	movl $(__BOOT_DS),%eax
89	movl %eax,%ds
90	movl %eax,%es
91	movl %eax,%fs
92	movl %eax,%gs
93
94/*
95 * Clear BSS first so that there are no surprises...
96 * No need to cld as DF is already clear from cld above...
97 */
98	xorl %eax,%eax
99	movl $__bss_start - __PAGE_OFFSET,%edi
100	movl $__bss_stop - __PAGE_OFFSET,%ecx
101	subl %edi,%ecx
102	shrl $2,%ecx
103	rep ; stosl
104/*
105 * Copy bootup parameters out of the way.
106 * Note: %esi still has the pointer to the real-mode data.
107 * With the kexec as boot loader, parameter segment might be loaded beyond
108 * kernel image and might not even be addressable by early boot page tables.
109 * (kexec on panic case). Hence copy out the parameters before initializing
110 * page tables.
111 */
112	movl $(boot_params - __PAGE_OFFSET),%edi
113	movl $(PARAM_SIZE/4),%ecx
114	cld
115	rep
116	movsl
117	movl boot_params - __PAGE_OFFSET + NEW_CL_POINTER,%esi
118	andl %esi,%esi
119	jnz 2f			# New command line protocol
120	cmpw $(OLD_CL_MAGIC),OLD_CL_MAGIC_ADDR
121	jne 1f
122	movzwl OLD_CL_OFFSET,%esi
123	addl $(OLD_CL_BASE_ADDR),%esi
1242:
125	movl $(boot_command_line - __PAGE_OFFSET),%edi
126	movl $(COMMAND_LINE_SIZE/4),%ecx
127	rep
128	movsl
1291:
130
131/*
132 * Initialize page tables.  This creates a PDE and a set of page
133 * tables, which are located immediately beyond _end.  The variable
134 * init_pg_tables_end is set up to point to the first "safe" location.
135 * Mappings are created both at virtual address 0 (identity mapping)
136 * and PAGE_OFFSET for up to _end+sizeof(page tables)+INIT_MAP_BEYOND_END.
137 *
138 * Warning: don't use %esi or the stack in this code.  However, %esp
139 * can be used as a GPR if you really need it...
140 */
141page_pde_offset = (__PAGE_OFFSET >> 20);
142
143	movl $(pg0 - __PAGE_OFFSET), %edi
144	movl $(swapper_pg_dir - __PAGE_OFFSET), %edx
145	movl $0x007, %eax			/* 0x007 = PRESENT+RW+USER */
14610:
147	leal 0x007(%edi),%ecx			/* Create PDE entry */
148	movl %ecx,(%edx)			/* Store identity PDE entry */
149	movl %ecx,page_pde_offset(%edx)		/* Store kernel PDE entry */
150	addl $4,%edx
151	movl $1024, %ecx
15211:
153	stosl
154	addl $0x1000,%eax
155	loop 11b
156	/* End condition: we must map up to and including INIT_MAP_BEYOND_END */
157	/* bytes beyond the end of our own page tables; the +0x007 is the attribute bits */
158	leal (INIT_MAP_BEYOND_END+0x007)(%edi),%ebp
159	cmpl %ebp,%eax
160	jb 10b
161	movl %edi,(init_pg_tables_end - __PAGE_OFFSET)
162
163	xorl %ebx,%ebx				/* This is the boot CPU (BSP) */
164	jmp 3f
165/*
166 * Non-boot CPU entry point; entered from trampoline.S
167 * We can't lgdt here, because lgdt itself uses a data segment, but
168 * we know the trampoline has already loaded the boot_gdt for us.
169 *
170 * If cpu hotplug is not supported then this code can go in init section
171 * which will be freed later
172 */
173
174#ifndef CONFIG_HOTPLUG_CPU
175.section .init.text,"ax",@progbits
176#endif
177
178	/* Do an early initialization of the fixmap area */
179	movl $(swapper_pg_dir - __PAGE_OFFSET), %edx
180	movl $(swapper_pg_pmd - __PAGE_OFFSET), %eax
181	addl $0x007, %eax			/* 0x007 = PRESENT+RW+USER */
182	movl %eax, 4092(%edx)
183
184#ifdef CONFIG_SMP
185ENTRY(startup_32_smp)
186	cld
187	movl $(__BOOT_DS),%eax
188	movl %eax,%ds
189	movl %eax,%es
190	movl %eax,%fs
191	movl %eax,%gs
192
193/*
194 *	New page tables may be in 4Mbyte page mode and may
195 *	be using the global pages.
196 *
197 *	NOTE! If we are on a 486 we may have no cr4 at all!
198 *	So we do not try to touch it unless we really have
199 *	some bits in it to set.  This won't work if the BSP
200 *	implements cr4 but this AP does not -- very unlikely
201 *	but be warned!  The same applies to the pse feature
202 *	if not equally supported. --macro
203 *
204 *	NOTE! We have to correct for the fact that we're
205 *	not yet offset PAGE_OFFSET..
206 */
207#define cr4_bits mmu_cr4_features-__PAGE_OFFSET
208	movl cr4_bits,%edx
209	andl %edx,%edx
210	jz 6f
211	movl %cr4,%eax		# Turn on paging options (PSE,PAE,..)
212	orl %edx,%eax
213	movl %eax,%cr4
214
215	btl $5, %eax		# check if PAE is enabled
216	jnc 6f
217
218	/* Check if extended functions are implemented */
219	movl $0x80000000, %eax
220	cpuid
221	cmpl $0x80000000, %eax
222	jbe 6f
223	mov $0x80000001, %eax
224	cpuid
225	/* Execute Disable bit supported? */
226	btl $20, %edx
227	jnc 6f
228
229	/* Setup EFER (Extended Feature Enable Register) */
230	movl $0xc0000080, %ecx
231	rdmsr
232
233	btsl $11, %eax
234	/* Make changes effective */
235	wrmsr
236
2376:
238	/* This is a secondary processor (AP) */
239	xorl %ebx,%ebx
240	incl %ebx
241
242#endif /* CONFIG_SMP */
2433:
244
245/*
246 * Enable paging
247 */
248	movl $swapper_pg_dir-__PAGE_OFFSET,%eax
249	movl %eax,%cr3		/* set the page table pointer.. */
250	movl %cr0,%eax
251	orl $0x80000000,%eax
252	movl %eax,%cr0		/* ..and set paging (PG) bit */
253	ljmp $__BOOT_CS,$1f	/* Clear prefetch and normalize %eip */
2541:
255	/* Set up the stack pointer */
256	lss stack_start,%esp
257
258/*
259 * Initialize eflags.  Some BIOS's leave bits like NT set.  This would
260 * confuse the debugger if this code is traced.
261 * XXX - best to initialize before switching to protected mode.
262 */
263	pushl $0
264	popfl
265
266#ifdef CONFIG_SMP
267	andl %ebx,%ebx
268	jz  1f				/* Initial CPU cleans BSS */
269	jmp checkCPUtype
2701:
271#endif /* CONFIG_SMP */
272
273/*
274 * start system 32-bit setup. We need to re-do some of the things done
275 * in 16-bit mode for the "real" operations.
276 */
277	call setup_idt
278
279checkCPUtype:
280
281	movl $-1,X86_CPUID		#  -1 for no CPUID initially
282
283/* check if it is 486 or 386. */
284/*
285 * XXX - this does a lot of unnecessary setup.  Alignment checks don't
286 * apply at our cpl of 0 and the stack ought to be aligned already, and
287 * we don't need to preserve eflags.
288 */
289
290	movb $3,X86		# at least 386
291	pushfl			# push EFLAGS
292	popl %eax		# get EFLAGS
293	movl %eax,%ecx		# save original EFLAGS
294	xorl $0x240000,%eax	# flip AC and ID bits in EFLAGS
295	pushl %eax		# copy to EFLAGS
296	popfl			# set EFLAGS
297	pushfl			# get new EFLAGS
298	popl %eax		# put it in eax
299	xorl %ecx,%eax		# change in flags
300	pushl %ecx		# restore original EFLAGS
301	popfl
302	testl $0x40000,%eax	# check if AC bit changed
303	je is386
304
305	movb $4,X86		# at least 486
306	testl $0x200000,%eax	# check if ID bit changed
307	je is486
308
309	/* get vendor info */
310	xorl %eax,%eax			# call CPUID with 0 -> return vendor ID
311	cpuid
312	movl %eax,X86_CPUID		# save CPUID level
313	movl %ebx,X86_VENDOR_ID		# lo 4 chars
314	movl %edx,X86_VENDOR_ID+4	# next 4 chars
315	movl %ecx,X86_VENDOR_ID+8	# last 4 chars
316
317	orl %eax,%eax			# do we have processor info as well?
318	je is486
319
320	movl $1,%eax		# Use the CPUID instruction to get CPU type
321	cpuid
322	movb %al,%cl		# save reg for future use
323	andb $0x0f,%ah		# mask processor family
324	movb %ah,X86
325	andb $0xf0,%al		# mask model
326	shrb $4,%al
327	movb %al,X86_MODEL
328	andb $0x0f,%cl		# mask mask revision
329	movb %cl,X86_MASK
330	movl %edx,X86_CAPABILITY
331
332is486:	movl $0x50022,%ecx	# set AM, WP, NE and MP
333	jmp 2f
334
335is386:	movl $2,%ecx		# set MP
3362:	movl %cr0,%eax
337	andl $0x80000011,%eax	# Save PG,PE,ET
338	orl %ecx,%eax
339	movl %eax,%cr0
340
341	call check_x87
342	lgdt early_gdt_descr
343	lidt idt_descr
344	ljmp $(__KERNEL_CS),$1f
3451:	movl $(__KERNEL_DS),%eax	# reload all the segment registers
346	movl %eax,%ss			# after changing gdt.
347	movl %eax,%fs			# gets reset once there's real percpu
348
349	movl $(__USER_DS),%eax		# DS/ES contains default USER segment
350	movl %eax,%ds
351	movl %eax,%es
352
353	xorl %eax,%eax			# Clear GS and LDT
354	movl %eax,%gs
355	lldt %ax
356
357	cld			# gcc2 wants the direction flag cleared at all times
358	pushl $0		# fake return address for unwinder
359#ifdef CONFIG_SMP
360	movb ready, %cl
361	movb $1, ready
362	cmpb $0,%cl		# the first CPU calls start_kernel
363	je   1f
364	movl $(__KERNEL_PERCPU), %eax
365	movl %eax,%fs		# set this cpu's percpu
366	jmp initialize_secondary # all other CPUs call initialize_secondary
3671:
368#endif /* CONFIG_SMP */
369	jmp start_kernel
370
371/*
372 * We depend on ET to be correct. This checks for 287/387.
373 */
374check_x87:
375	movb $0,X86_HARD_MATH
376	clts
377	fninit
378	fstsw %ax
379	cmpb $0,%al
380	je 1f
381	movl %cr0,%eax		/* no coprocessor: have to set bits */
382	xorl $4,%eax		/* set EM */
383	movl %eax,%cr0
384	ret
385	ALIGN
3861:	movb $1,X86_HARD_MATH
387	.byte 0xDB,0xE4		/* fsetpm for 287, ignored by 387 */
388	ret
389
390/*
391 *  setup_idt
392 *
393 *  sets up a idt with 256 entries pointing to
394 *  ignore_int, interrupt gates. It doesn't actually load
395 *  idt - that can be done only after paging has been enabled
396 *  and the kernel moved to PAGE_OFFSET. Interrupts
397 *  are enabled elsewhere, when we can be relatively
398 *  sure everything is ok.
399 *
400 *  Warning: %esi is live across this function.
401 */
402setup_idt:
403	lea ignore_int,%edx
404	movl $(__KERNEL_CS << 16),%eax
405	movw %dx,%ax		/* selector = 0x0010 = cs */
406	movw $0x8E00,%dx	/* interrupt gate - dpl=0, present */
407
408	lea idt_table,%edi
409	mov $256,%ecx
410rp_sidt:
411	movl %eax,(%edi)
412	movl %edx,4(%edi)
413	addl $8,%edi
414	dec %ecx
415	jne rp_sidt
416
417.macro	set_early_handler handler,trapno
418	lea \handler,%edx
419	movl $(__KERNEL_CS << 16),%eax
420	movw %dx,%ax
421	movw $0x8E00,%dx	/* interrupt gate - dpl=0, present */
422	lea idt_table,%edi
423	movl %eax,8*\trapno(%edi)
424	movl %edx,8*\trapno+4(%edi)
425.endm
426
427	set_early_handler handler=early_divide_err,trapno=0
428	set_early_handler handler=early_illegal_opcode,trapno=6
429	set_early_handler handler=early_protection_fault,trapno=13
430	set_early_handler handler=early_page_fault,trapno=14
431
432	ret
433
434early_divide_err:
435	xor %edx,%edx
436	pushl $0	/* fake errcode */
437	jmp early_fault
438
439early_illegal_opcode:
440	movl $6,%edx
441	pushl $0	/* fake errcode */
442	jmp early_fault
443
444early_protection_fault:
445	movl $13,%edx
446	jmp early_fault
447
448early_page_fault:
449	movl $14,%edx
450	jmp early_fault
451
452early_fault:
453	cld
454#ifdef CONFIG_PRINTK
455	pusha
456	movl $(__KERNEL_DS),%eax
457	movl %eax,%ds
458	movl %eax,%es
459	cmpl $2,early_recursion_flag
460	je hlt_loop
461	incl early_recursion_flag
462	movl %cr2,%eax
463	pushl %eax
464	pushl %edx		/* trapno */
465	pushl $fault_msg
466#ifdef CONFIG_EARLY_PRINTK
467	call early_printk
468#else
469	call printk
470#endif
471#endif
472hlt_loop:
473	hlt
474	jmp hlt_loop
475
476/* This is the default interrupt "handler" :-) */
477	ALIGN
478ignore_int:
479	cld
480#ifdef CONFIG_PRINTK
481	pushl %eax
482	pushl %ecx
483	pushl %edx
484	pushl %es
485	pushl %ds
486	movl $(__KERNEL_DS),%eax
487	movl %eax,%ds
488	movl %eax,%es
489	cmpl $2,early_recursion_flag
490	je hlt_loop
491	incl early_recursion_flag
492	pushl 16(%esp)
493	pushl 24(%esp)
494	pushl 32(%esp)
495	pushl 40(%esp)
496	pushl $int_msg
497#ifdef CONFIG_EARLY_PRINTK
498	call early_printk
499#else
500	call printk
501#endif
502	addl $(5*4),%esp
503	popl %ds
504	popl %es
505	popl %edx
506	popl %ecx
507	popl %eax
508#endif
509	iret
510
511.section .text
512/*
513 * Real beginning of normal "text" segment
514 */
515ENTRY(stext)
516ENTRY(_stext)
517
518/*
519 * BSS section
520 */
521.section ".bss.page_aligned","wa"
522	.align PAGE_SIZE_asm
523ENTRY(swapper_pg_dir)
524	.fill 1024,4,0
525ENTRY(swapper_pg_pmd)
526	.fill 1024,4,0
527ENTRY(empty_zero_page)
528	.fill 4096,1,0
529
530/*
531 * This starts the data section.
532 */
533.data
534ENTRY(stack_start)
535	.long init_thread_union+THREAD_SIZE
536	.long __BOOT_DS
537
538ready:	.byte 0
539
540early_recursion_flag:
541	.long 0
542
543int_msg:
544	.asciz "Unknown interrupt or fault at EIP %p %p %p\n"
545
546fault_msg:
547	.ascii								\
548/* fault info: */	"BUG: Int %d: CR2 %p\n"				\
549/* pusha regs: */	"     EDI %p  ESI %p  EBP %p  ESP %p\n"		\
550			"     EBX %p  EDX %p  ECX %p  EAX %p\n"		\
551/* fault frame: */	"     err %p  EIP %p   CS %p  flg %p\n"		\
552									\
553			"Stack: %p %p %p %p %p %p %p %p\n"		\
554			"       %p %p %p %p %p %p %p %p\n"		\
555			"       %p %p %p %p %p %p %p %p\n"
556
557#include "../../x86/xen/xen-head.S"
558
559/*
560 * The IDT and GDT 'descriptors' are a strange 48-bit object
561 * only used by the lidt and lgdt instructions. They are not
562 * like usual segment descriptors - they consist of a 16-bit
563 * segment size, and 32-bit linear address value:
564 */
565
566.globl boot_gdt_descr
567.globl idt_descr
568
569	ALIGN
570# early boot GDT descriptor (must use 1:1 address mapping)
571	.word 0				# 32 bit align gdt_desc.address
572boot_gdt_descr:
573	.word __BOOT_DS+7
574	.long boot_gdt - __PAGE_OFFSET
575
576	.word 0				# 32-bit align idt_desc.address
577idt_descr:
578	.word IDT_ENTRIES*8-1		# idt contains 256 entries
579	.long idt_table
580
581# boot GDT descriptor (later on used by CPU#0):
582	.word 0				# 32 bit align gdt_desc.address
583ENTRY(early_gdt_descr)
584	.word GDT_ENTRIES*8-1
585	.long per_cpu__gdt_page		/* Overwritten for secondary CPUs */
586
587/*
588 * The boot_gdt must mirror the equivalent in setup.S and is
589 * used only for booting.
590 */
591	.align L1_CACHE_BYTES
592ENTRY(boot_gdt)
593	.fill GDT_ENTRY_BOOT_CS,8,0
594	.quad 0x00cf9a000000ffff	/* kernel 4GB code at 0x00000000 */
595	.quad 0x00cf92000000ffff	/* kernel 4GB data at 0x00000000 */
596