xref: /linux/arch/x86/kernel/head_32.S (revision c3262d3d) 
1/* SPDX-License-Identifier: GPL-2.0 */
2/*
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/export.h>
12#include <linux/threads.h>
13#include <linux/init.h>
14#include <linux/linkage.h>
15#include <asm/segment.h>
16#include <asm/page_types.h>
17#include <asm/pgtable_types.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#include <asm/msr-index.h>
24#include <asm/cpufeatures.h>
25#include <asm/percpu.h>
26#include <asm/nops.h>
27#include <asm/nospec-branch.h>
28#include <asm/bootparam.h>
29#include <asm/pgtable_32.h>
30
31/* Physical address */
32#define pa(X) ((X) - __PAGE_OFFSET)
33
34/*
35 * References to members of the new_cpu_data structure.
36 */
37
38#define X86		new_cpu_data+CPUINFO_x86
39#define X86_VENDOR	new_cpu_data+CPUINFO_x86_vendor
40#define X86_MODEL	new_cpu_data+CPUINFO_x86_model
41#define X86_STEPPING	new_cpu_data+CPUINFO_x86_stepping
42#define X86_HARD_MATH	new_cpu_data+CPUINFO_hard_math
43#define X86_CPUID	new_cpu_data+CPUINFO_cpuid_level
44#define X86_CAPABILITY	new_cpu_data+CPUINFO_x86_capability
45#define X86_VENDOR_ID	new_cpu_data+CPUINFO_x86_vendor_id
46
47/*
48 * Worst-case size of the kernel mapping we need to make:
49 * a relocatable kernel can live anywhere in lowmem, so we need to be able
50 * to map all of lowmem.
51 */
52KERNEL_PAGES = LOWMEM_PAGES
53
54INIT_MAP_SIZE = PAGE_TABLE_SIZE(KERNEL_PAGES) * PAGE_SIZE
55RESERVE_BRK(pagetables, INIT_MAP_SIZE)
56
57/*
58 * 32-bit kernel entrypoint; only used by the boot CPU.  On entry,
59 * %esi points to the real-mode code as a 32-bit pointer.
60 * CS and DS must be 4 GB flat segments, but we don't depend on
61 * any particular GDT layout, because we load our own as soon as we
62 * can.
63 */
64__HEAD
65SYM_CODE_START(startup_32)
66	movl pa(initial_stack),%ecx
67
68/*
69 * Set segments to known values.
70 */
71	lgdt pa(boot_gdt_descr)
72	movl $(__BOOT_DS),%eax
73	movl %eax,%ds
74	movl %eax,%es
75	movl %eax,%fs
76	movl %eax,%gs
77	movl %eax,%ss
78	leal -__PAGE_OFFSET(%ecx),%esp
79
80/*
81 * Clear BSS first so that there are no surprises...
82 */
83	cld
84	xorl %eax,%eax
85	movl $pa(__bss_start),%edi
86	movl $pa(__bss_stop),%ecx
87	subl %edi,%ecx
88	shrl $2,%ecx
89	rep ; stosl
90/*
91 * Copy bootup parameters out of the way.
92 * Note: %esi still has the pointer to the real-mode data.
93 * With the kexec as boot loader, parameter segment might be loaded beyond
94 * kernel image and might not even be addressable by early boot page tables.
95 * (kexec on panic case). Hence copy out the parameters before initializing
96 * page tables.
97 */
98	movl $pa(boot_params),%edi
99	movl $(PARAM_SIZE/4),%ecx
100	cld
101	rep
102	movsl
103	movl pa(boot_params) + NEW_CL_POINTER,%esi
104	andl %esi,%esi
105	jz 1f			# No command line
106	movl $pa(boot_command_line),%edi
107	movl $(COMMAND_LINE_SIZE/4),%ecx
108	rep
109	movsl
1101:
111
112#ifdef CONFIG_OLPC
113	/* save OFW's pgdir table for later use when calling into OFW */
114	movl %cr3, %eax
115	movl %eax, pa(olpc_ofw_pgd)
116#endif
117
118	/* Create early pagetables. */
119	call  mk_early_pgtbl_32
120
121	/* Do early initialization of the fixmap area */
122	movl $pa(initial_pg_fixmap)+PDE_IDENT_ATTR,%eax
123#ifdef  CONFIG_X86_PAE
124#define KPMDS (((-__PAGE_OFFSET) >> 30) & 3) /* Number of kernel PMDs */
125	movl %eax,pa(initial_pg_pmd+0x1000*KPMDS-8)
126#else
127	movl %eax,pa(initial_page_table+0xffc)
128#endif
129
130	jmp .Ldefault_entry
131SYM_CODE_END(startup_32)
132
133/*
134 * Non-boot CPU entry point; entered from trampoline.S
135 * We can't lgdt here, because lgdt itself uses a data segment, but
136 * we know the trampoline has already loaded the boot_gdt for us.
137 *
138 * If cpu hotplug is not supported then this code can go in init section
139 * which will be freed later
140 */
141SYM_FUNC_START(startup_32_smp)
142	cld
143	movl $(__BOOT_DS),%eax
144	movl %eax,%ds
145	movl %eax,%es
146	movl %eax,%fs
147	movl %eax,%gs
148	movl pa(initial_stack),%ecx
149	movl %eax,%ss
150	leal -__PAGE_OFFSET(%ecx),%esp
151
152.Ldefault_entry:
153	movl $(CR0_STATE & ~X86_CR0_PG),%eax
154	movl %eax,%cr0
155
156/*
157 * We want to start out with EFLAGS unambiguously cleared. Some BIOSes leave
158 * bits like NT set. This would confuse the debugger if this code is traced. So
159 * initialize them properly now before switching to protected mode. That means
160 * DF in particular (even though we have cleared it earlier after copying the
161 * command line) because GCC expects it.
162 */
163	pushl $0
164	popfl
165
166/*
167 * New page tables may be in 4Mbyte page mode and may be using the global pages.
168 *
169 * NOTE! If we are on a 486 we may have no cr4 at all! Specifically, cr4 exists
170 * if and only if CPUID exists and has flags other than the FPU flag set.
171 */
172	movl $-1,pa(X86_CPUID)		# preset CPUID level
173	movl $X86_EFLAGS_ID,%ecx
174	pushl %ecx
175	popfl				# set EFLAGS=ID
176	pushfl
177	popl %eax			# get EFLAGS
178	testl $X86_EFLAGS_ID,%eax	# did EFLAGS.ID remained set?
179	jz .Lenable_paging		# hw disallowed setting of ID bit
180					# which means no CPUID and no CR4
181
182	xorl %eax,%eax
183	cpuid
184	movl %eax,pa(X86_CPUID)		# save largest std CPUID function
185
186	movl $1,%eax
187	cpuid
188	andl $~1,%edx			# Ignore CPUID.FPU
189	jz .Lenable_paging		# No flags or only CPUID.FPU = no CR4
190
191	movl pa(mmu_cr4_features),%eax
192	movl %eax,%cr4
193
194	testb $X86_CR4_PAE, %al		# check if PAE is enabled
195	jz .Lenable_paging
196
197	/* Check if extended functions are implemented */
198	movl $0x80000000, %eax
199	cpuid
200	/* Value must be in the range 0x80000001 to 0x8000ffff */
201	subl $0x80000001, %eax
202	cmpl $(0x8000ffff-0x80000001), %eax
203	ja .Lenable_paging
204
205	/* Clear bogus XD_DISABLE bits */
206	call verify_cpu
207
208	mov $0x80000001, %eax
209	cpuid
210	/* Execute Disable bit supported? */
211	btl $(X86_FEATURE_NX & 31), %edx
212	jnc .Lenable_paging
213
214	/* Setup EFER (Extended Feature Enable Register) */
215	movl $MSR_EFER, %ecx
216	rdmsr
217
218	btsl $_EFER_NX, %eax
219	/* Make changes effective */
220	wrmsr
221
222.Lenable_paging:
223
224/*
225 * Enable paging
226 */
227	movl $pa(initial_page_table), %eax
228	movl %eax,%cr3		/* set the page table pointer.. */
229	movl $CR0_STATE,%eax
230	movl %eax,%cr0		/* ..and set paging (PG) bit */
231	ljmp $__BOOT_CS,$1f	/* Clear prefetch and normalize %eip */
2321:
233	/* Shift the stack pointer to a virtual address */
234	addl $__PAGE_OFFSET, %esp
235
236/*
237 * Check if it is 486
238 */
239	movb $4,X86			# at least 486
240	cmpl $-1,X86_CPUID
241	je .Lis486
242
243	/* get vendor info */
244	xorl %eax,%eax			# call CPUID with 0 -> return vendor ID
245	cpuid
246	movl %eax,X86_CPUID		# save CPUID level
247	movl %ebx,X86_VENDOR_ID		# lo 4 chars
248	movl %edx,X86_VENDOR_ID+4	# next 4 chars
249	movl %ecx,X86_VENDOR_ID+8	# last 4 chars
250
251	orl %eax,%eax			# do we have processor info as well?
252	je .Lis486
253
254	movl $1,%eax		# Use the CPUID instruction to get CPU type
255	cpuid
256	movb %al,%cl		# save reg for future use
257	andb $0x0f,%ah		# mask processor family
258	movb %ah,X86
259	andb $0xf0,%al		# mask model
260	shrb $4,%al
261	movb %al,X86_MODEL
262	andb $0x0f,%cl		# mask mask revision
263	movb %cl,X86_STEPPING
264	movl %edx,X86_CAPABILITY
265
266.Lis486:
267	movl $0x50022,%ecx	# set AM, WP, NE and MP
268	movl %cr0,%eax
269	andl $0x80000011,%eax	# Save PG,PE,ET
270	orl %ecx,%eax
271	movl %eax,%cr0
272
273	lgdt early_gdt_descr
274	ljmp $(__KERNEL_CS),$1f
2751:	movl $(__KERNEL_DS),%eax	# reload all the segment registers
276	movl %eax,%ss			# after changing gdt.
277
278	movl $(__USER_DS),%eax		# DS/ES contains default USER segment
279	movl %eax,%ds
280	movl %eax,%es
281
282	movl $(__KERNEL_PERCPU), %eax
283	movl %eax,%fs			# set this cpu's percpu
284
285	xorl %eax,%eax
286	movl %eax,%gs			# clear possible garbage in %gs
287
288	xorl %eax,%eax			# Clear LDT
289	lldt %ax
290
291	call *(initial_code)
2921:	jmp 1b
293SYM_FUNC_END(startup_32_smp)
294
295#include "verify_cpu.S"
296
297__INIT
298SYM_FUNC_START(early_idt_handler_array)
299	# 36(%esp) %eflags
300	# 32(%esp) %cs
301	# 28(%esp) %eip
302	# 24(%rsp) error code
303	i = 0
304	.rept NUM_EXCEPTION_VECTORS
305	.if ((EXCEPTION_ERRCODE_MASK >> i) & 1) == 0
306	pushl $0		# Dummy error code, to make stack frame uniform
307	.endif
308	pushl $i		# 20(%esp) Vector number
309	jmp early_idt_handler_common
310	i = i + 1
311	.fill early_idt_handler_array + i*EARLY_IDT_HANDLER_SIZE - ., 1, 0xcc
312	.endr
313SYM_FUNC_END(early_idt_handler_array)
314
315SYM_CODE_START_LOCAL(early_idt_handler_common)
316	/*
317	 * The stack is the hardware frame, an error code or zero, and the
318	 * vector number.
319	 */
320	cld
321
322	incl %ss:early_recursion_flag
323
324	/* The vector number is in pt_regs->gs */
325
326	cld
327	pushl	%fs		/* pt_regs->fs (__fsh varies by model) */
328	pushl	%es		/* pt_regs->es (__esh varies by model) */
329	pushl	%ds		/* pt_regs->ds (__dsh varies by model) */
330	pushl	%eax		/* pt_regs->ax */
331	pushl	%ebp		/* pt_regs->bp */
332	pushl	%edi		/* pt_regs->di */
333	pushl	%esi		/* pt_regs->si */
334	pushl	%edx		/* pt_regs->dx */
335	pushl	%ecx		/* pt_regs->cx */
336	pushl	%ebx		/* pt_regs->bx */
337
338	/* Fix up DS and ES */
339	movl	$(__KERNEL_DS), %ecx
340	movl	%ecx, %ds
341	movl	%ecx, %es
342
343	/* Load the vector number into EDX */
344	movl	PT_GS(%esp), %edx
345
346	/* Load GS into pt_regs->gs (and maybe clobber __gsh) */
347	movw	%gs, PT_GS(%esp)
348
349	movl	%esp, %eax	/* args are pt_regs (EAX), trapnr (EDX) */
350	call	early_fixup_exception
351
352	popl	%ebx		/* pt_regs->bx */
353	popl	%ecx		/* pt_regs->cx */
354	popl	%edx		/* pt_regs->dx */
355	popl	%esi		/* pt_regs->si */
356	popl	%edi		/* pt_regs->di */
357	popl	%ebp		/* pt_regs->bp */
358	popl	%eax		/* pt_regs->ax */
359	popl	%ds		/* pt_regs->ds (always ignores __dsh) */
360	popl	%es		/* pt_regs->es (always ignores __esh) */
361	popl	%fs		/* pt_regs->fs (always ignores __fsh) */
362	popl	%gs		/* pt_regs->gs (always ignores __gsh) */
363	decl	%ss:early_recursion_flag
364	addl	$4, %esp	/* pop pt_regs->orig_ax */
365	iret
366SYM_CODE_END(early_idt_handler_common)
367
368/* This is the default interrupt "handler" :-) */
369SYM_FUNC_START(early_ignore_irq)
370	cld
371#ifdef CONFIG_PRINTK
372	pushl %eax
373	pushl %ecx
374	pushl %edx
375	pushl %es
376	pushl %ds
377	movl $(__KERNEL_DS),%eax
378	movl %eax,%ds
379	movl %eax,%es
380	cmpl $2,early_recursion_flag
381	je hlt_loop
382	incl early_recursion_flag
383	pushl 16(%esp)
384	pushl 24(%esp)
385	pushl 32(%esp)
386	pushl 40(%esp)
387	pushl $int_msg
388	call _printk
389
390	call dump_stack
391
392	addl $(5*4),%esp
393	popl %ds
394	popl %es
395	popl %edx
396	popl %ecx
397	popl %eax
398#endif
399	iret
400
401hlt_loop:
402	hlt
403	jmp hlt_loop
404SYM_FUNC_END(early_ignore_irq)
405
406__INITDATA
407	.align 4
408SYM_DATA(early_recursion_flag, .long 0)
409
410__REFDATA
411	.align 4
412SYM_DATA(initial_code,		.long i386_start_kernel)
413
414#ifdef CONFIG_MITIGATION_PAGE_TABLE_ISOLATION
415#define	PGD_ALIGN	(2 * PAGE_SIZE)
416#define PTI_USER_PGD_FILL	1024
417#else
418#define	PGD_ALIGN	(PAGE_SIZE)
419#define PTI_USER_PGD_FILL	0
420#endif
421/*
422 * BSS section
423 */
424__PAGE_ALIGNED_BSS
425	.align PGD_ALIGN
426#ifdef CONFIG_X86_PAE
427.globl initial_pg_pmd
428initial_pg_pmd:
429	.fill 1024*KPMDS,4,0
430#else
431.globl initial_page_table
432initial_page_table:
433	.fill 1024,4,0
434#endif
435	.align PGD_ALIGN
436initial_pg_fixmap:
437	.fill 1024,4,0
438.globl swapper_pg_dir
439	.align PGD_ALIGN
440swapper_pg_dir:
441	.fill 1024,4,0
442	.fill PTI_USER_PGD_FILL,4,0
443.globl empty_zero_page
444empty_zero_page:
445	.fill 4096,1,0
446EXPORT_SYMBOL(empty_zero_page)
447
448/*
449 * This starts the data section.
450 */
451#ifdef CONFIG_X86_PAE
452__PAGE_ALIGNED_DATA
453	/* Page-aligned for the benefit of paravirt? */
454	.align PGD_ALIGN
455SYM_DATA_START(initial_page_table)
456	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR),0	/* low identity map */
457# if KPMDS == 3
458	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR),0
459	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR+0x1000),0
460	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR+0x2000),0
461# elif KPMDS == 2
462	.long	0,0
463	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR),0
464	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR+0x1000),0
465# elif KPMDS == 1
466	.long	0,0
467	.long	0,0
468	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR),0
469# else
470#  error "Kernel PMDs should be 1, 2 or 3"
471# endif
472	.align PAGE_SIZE		/* needs to be page-sized too */
473
474#ifdef CONFIG_MITIGATION_PAGE_TABLE_ISOLATION
475	/*
476	 * PTI needs another page so sync_initial_pagetable() works correctly
477	 * and does not scribble over the data which is placed behind the
478	 * actual initial_page_table. See clone_pgd_range().
479	 */
480	.fill 1024, 4, 0
481#endif
482
483SYM_DATA_END(initial_page_table)
484#endif
485
486.data
487.balign 4
488SYM_DATA(initial_stack, .long __top_init_kernel_stack)
489
490__INITRODATA
491int_msg:
492	.asciz "Unknown interrupt or fault at: %p %p %p\n"
493
494#include "../xen/xen-head.S"
495
496/*
497 * The IDT and GDT 'descriptors' are a strange 48-bit object
498 * only used by the lidt and lgdt instructions. They are not
499 * like usual segment descriptors - they consist of a 16-bit
500 * segment size, and 32-bit linear address value:
501 */
502
503	.data
504	ALIGN
505# early boot GDT descriptor (must use 1:1 address mapping)
506	.word 0				# 32 bit align gdt_desc.address
507SYM_DATA_START_LOCAL(boot_gdt_descr)
508	.word __BOOT_DS+7
509	.long boot_gdt - __PAGE_OFFSET
510SYM_DATA_END(boot_gdt_descr)
511
512# boot GDT descriptor (later on used by CPU#0):
513	.word 0				# 32 bit align gdt_desc.address
514SYM_DATA_START(early_gdt_descr)
515	.word GDT_ENTRIES*8-1
516	.long gdt_page			/* Overwritten for secondary CPUs */
517SYM_DATA_END(early_gdt_descr)
518
519/*
520 * The boot_gdt must mirror the equivalent in setup.S and is
521 * used only for booting.
522 */
523	.align L1_CACHE_BYTES
524SYM_DATA_START(boot_gdt)
525	.fill GDT_ENTRY_BOOT_CS,8,0
526	.quad 0x00cf9a000000ffff	/* kernel 4GB code at 0x00000000 */
527	.quad 0x00cf92000000ffff	/* kernel 4GB data at 0x00000000 */
528SYM_DATA_END(boot_gdt)
529