xref: /openbmc/linux/arch/x86/kernel/head_32.S (revision 94d964e5) 
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/threads.h>
12#include <linux/init.h>
13#include <linux/linkage.h>
14#include <asm/segment.h>
15#include <asm/page_types.h>
16#include <asm/pgtable_types.h>
17#include <asm/cache.h>
18#include <asm/thread_info.h>
19#include <asm/asm-offsets.h>
20#include <asm/setup.h>
21#include <asm/processor-flags.h>
22#include <asm/msr-index.h>
23#include <asm/cpufeatures.h>
24#include <asm/percpu.h>
25#include <asm/nops.h>
26#include <asm/bootparam.h>
27#include <asm/export.h>
28#include <asm/pgtable_32.h>
29
30/* Physical address */
31#define pa(X) ((X) - __PAGE_OFFSET)
32
33/*
34 * References to members of the new_cpu_data structure.
35 */
36
37#define X86		new_cpu_data+CPUINFO_x86
38#define X86_VENDOR	new_cpu_data+CPUINFO_x86_vendor
39#define X86_MODEL	new_cpu_data+CPUINFO_x86_model
40#define X86_STEPPING	new_cpu_data+CPUINFO_x86_stepping
41#define X86_HARD_MATH	new_cpu_data+CPUINFO_hard_math
42#define X86_CPUID	new_cpu_data+CPUINFO_cpuid_level
43#define X86_CAPABILITY	new_cpu_data+CPUINFO_x86_capability
44#define X86_VENDOR_ID	new_cpu_data+CPUINFO_x86_vendor_id
45
46
47#define SIZEOF_PTREGS 17*4
48
49/*
50 * Worst-case size of the kernel mapping we need to make:
51 * a relocatable kernel can live anywhere in lowmem, so we need to be able
52 * to map all of lowmem.
53 */
54KERNEL_PAGES = LOWMEM_PAGES
55
56INIT_MAP_SIZE = PAGE_TABLE_SIZE(KERNEL_PAGES) * PAGE_SIZE
57RESERVE_BRK(pagetables, INIT_MAP_SIZE)
58
59/*
60 * 32-bit kernel entrypoint; only used by the boot CPU.  On entry,
61 * %esi points to the real-mode code as a 32-bit pointer.
62 * CS and DS must be 4 GB flat segments, but we don't depend on
63 * any particular GDT layout, because we load our own as soon as we
64 * can.
65 */
66__HEAD
67SYM_CODE_START(startup_32)
68	movl pa(initial_stack),%ecx
69
70/*
71 * Set segments to known values.
72 */
73	lgdt pa(boot_gdt_descr)
74	movl $(__BOOT_DS),%eax
75	movl %eax,%ds
76	movl %eax,%es
77	movl %eax,%fs
78	movl %eax,%gs
79	movl %eax,%ss
80	leal -__PAGE_OFFSET(%ecx),%esp
81
82/*
83 * Clear BSS first so that there are no surprises...
84 */
85	cld
86	xorl %eax,%eax
87	movl $pa(__bss_start),%edi
88	movl $pa(__bss_stop),%ecx
89	subl %edi,%ecx
90	shrl $2,%ecx
91	rep ; stosl
92/*
93 * Copy bootup parameters out of the way.
94 * Note: %esi still has the pointer to the real-mode data.
95 * With the kexec as boot loader, parameter segment might be loaded beyond
96 * kernel image and might not even be addressable by early boot page tables.
97 * (kexec on panic case). Hence copy out the parameters before initializing
98 * page tables.
99 */
100	movl $pa(boot_params),%edi
101	movl $(PARAM_SIZE/4),%ecx
102	cld
103	rep
104	movsl
105	movl pa(boot_params) + NEW_CL_POINTER,%esi
106	andl %esi,%esi
107	jz 1f			# No command line
108	movl $pa(boot_command_line),%edi
109	movl $(COMMAND_LINE_SIZE/4),%ecx
110	rep
111	movsl
1121:
113
114#ifdef CONFIG_OLPC
115	/* save OFW's pgdir table for later use when calling into OFW */
116	movl %cr3, %eax
117	movl %eax, pa(olpc_ofw_pgd)
118#endif
119
120#ifdef CONFIG_MICROCODE
121	/* Early load ucode on BSP. */
122	call load_ucode_bsp
123#endif
124
125	/* Create early pagetables. */
126	call  mk_early_pgtbl_32
127
128	/* Do early initialization of the fixmap area */
129	movl $pa(initial_pg_fixmap)+PDE_IDENT_ATTR,%eax
130#ifdef  CONFIG_X86_PAE
131#define KPMDS (((-__PAGE_OFFSET) >> 30) & 3) /* Number of kernel PMDs */
132	movl %eax,pa(initial_pg_pmd+0x1000*KPMDS-8)
133#else
134	movl %eax,pa(initial_page_table+0xffc)
135#endif
136
137	jmp .Ldefault_entry
138SYM_CODE_END(startup_32)
139
140#ifdef CONFIG_HOTPLUG_CPU
141/*
142 * Boot CPU0 entry point. It's called from play_dead(). Everything has been set
143 * up already except stack. We just set up stack here. Then call
144 * start_secondary().
145 */
146SYM_FUNC_START(start_cpu0)
147	movl initial_stack, %ecx
148	movl %ecx, %esp
149	call *(initial_code)
1501:	jmp 1b
151SYM_FUNC_END(start_cpu0)
152#endif
153
154/*
155 * Non-boot CPU entry point; entered from trampoline.S
156 * We can't lgdt here, because lgdt itself uses a data segment, but
157 * we know the trampoline has already loaded the boot_gdt for us.
158 *
159 * If cpu hotplug is not supported then this code can go in init section
160 * which will be freed later
161 */
162SYM_FUNC_START(startup_32_smp)
163	cld
164	movl $(__BOOT_DS),%eax
165	movl %eax,%ds
166	movl %eax,%es
167	movl %eax,%fs
168	movl %eax,%gs
169	movl pa(initial_stack),%ecx
170	movl %eax,%ss
171	leal -__PAGE_OFFSET(%ecx),%esp
172
173#ifdef CONFIG_MICROCODE
174	/* Early load ucode on AP. */
175	call load_ucode_ap
176#endif
177
178.Ldefault_entry:
179	movl $(CR0_STATE & ~X86_CR0_PG),%eax
180	movl %eax,%cr0
181
182/*
183 * We want to start out with EFLAGS unambiguously cleared. Some BIOSes leave
184 * bits like NT set. This would confuse the debugger if this code is traced. So
185 * initialize them properly now before switching to protected mode. That means
186 * DF in particular (even though we have cleared it earlier after copying the
187 * command line) because GCC expects it.
188 */
189	pushl $0
190	popfl
191
192/*
193 * New page tables may be in 4Mbyte page mode and may be using the global pages.
194 *
195 * NOTE! If we are on a 486 we may have no cr4 at all! Specifically, cr4 exists
196 * if and only if CPUID exists and has flags other than the FPU flag set.
197 */
198	movl $-1,pa(X86_CPUID)		# preset CPUID level
199	movl $X86_EFLAGS_ID,%ecx
200	pushl %ecx
201	popfl				# set EFLAGS=ID
202	pushfl
203	popl %eax			# get EFLAGS
204	testl $X86_EFLAGS_ID,%eax	# did EFLAGS.ID remained set?
205	jz .Lenable_paging		# hw disallowed setting of ID bit
206					# which means no CPUID and no CR4
207
208	xorl %eax,%eax
209	cpuid
210	movl %eax,pa(X86_CPUID)		# save largest std CPUID function
211
212	movl $1,%eax
213	cpuid
214	andl $~1,%edx			# Ignore CPUID.FPU
215	jz .Lenable_paging		# No flags or only CPUID.FPU = no CR4
216
217	movl pa(mmu_cr4_features),%eax
218	movl %eax,%cr4
219
220	testb $X86_CR4_PAE, %al		# check if PAE is enabled
221	jz .Lenable_paging
222
223	/* Check if extended functions are implemented */
224	movl $0x80000000, %eax
225	cpuid
226	/* Value must be in the range 0x80000001 to 0x8000ffff */
227	subl $0x80000001, %eax
228	cmpl $(0x8000ffff-0x80000001), %eax
229	ja .Lenable_paging
230
231	/* Clear bogus XD_DISABLE bits */
232	call verify_cpu
233
234	mov $0x80000001, %eax
235	cpuid
236	/* Execute Disable bit supported? */
237	btl $(X86_FEATURE_NX & 31), %edx
238	jnc .Lenable_paging
239
240	/* Setup EFER (Extended Feature Enable Register) */
241	movl $MSR_EFER, %ecx
242	rdmsr
243
244	btsl $_EFER_NX, %eax
245	/* Make changes effective */
246	wrmsr
247
248.Lenable_paging:
249
250/*
251 * Enable paging
252 */
253	movl $pa(initial_page_table), %eax
254	movl %eax,%cr3		/* set the page table pointer.. */
255	movl $CR0_STATE,%eax
256	movl %eax,%cr0		/* ..and set paging (PG) bit */
257	ljmp $__BOOT_CS,$1f	/* Clear prefetch and normalize %eip */
2581:
259	/* Shift the stack pointer to a virtual address */
260	addl $__PAGE_OFFSET, %esp
261
262/*
263 * start system 32-bit setup. We need to re-do some of the things done
264 * in 16-bit mode for the "real" operations.
265 */
266	movl setup_once_ref,%eax
267	andl %eax,%eax
268	jz 1f				# Did we do this already?
269	call *%eax
2701:
271
272/*
273 * Check if it is 486
274 */
275	movb $4,X86			# at least 486
276	cmpl $-1,X86_CPUID
277	je .Lis486
278
279	/* get vendor info */
280	xorl %eax,%eax			# call CPUID with 0 -> return vendor ID
281	cpuid
282	movl %eax,X86_CPUID		# save CPUID level
283	movl %ebx,X86_VENDOR_ID		# lo 4 chars
284	movl %edx,X86_VENDOR_ID+4	# next 4 chars
285	movl %ecx,X86_VENDOR_ID+8	# last 4 chars
286
287	orl %eax,%eax			# do we have processor info as well?
288	je .Lis486
289
290	movl $1,%eax		# Use the CPUID instruction to get CPU type
291	cpuid
292	movb %al,%cl		# save reg for future use
293	andb $0x0f,%ah		# mask processor family
294	movb %ah,X86
295	andb $0xf0,%al		# mask model
296	shrb $4,%al
297	movb %al,X86_MODEL
298	andb $0x0f,%cl		# mask mask revision
299	movb %cl,X86_STEPPING
300	movl %edx,X86_CAPABILITY
301
302.Lis486:
303	movl $0x50022,%ecx	# set AM, WP, NE and MP
304	movl %cr0,%eax
305	andl $0x80000011,%eax	# Save PG,PE,ET
306	orl %ecx,%eax
307	movl %eax,%cr0
308
309	lgdt early_gdt_descr
310	ljmp $(__KERNEL_CS),$1f
3111:	movl $(__KERNEL_DS),%eax	# reload all the segment registers
312	movl %eax,%ss			# after changing gdt.
313
314	movl $(__USER_DS),%eax		# DS/ES contains default USER segment
315	movl %eax,%ds
316	movl %eax,%es
317
318	movl $(__KERNEL_PERCPU), %eax
319	movl %eax,%fs			# set this cpu's percpu
320
321	xorl %eax,%eax
322	movl %eax,%gs			# clear possible garbage in %gs
323
324	xorl %eax,%eax			# Clear LDT
325	lldt %ax
326
327	call *(initial_code)
3281:	jmp 1b
329SYM_FUNC_END(startup_32_smp)
330
331#include "verify_cpu.S"
332
333/*
334 *  setup_once
335 *
336 *  The setup work we only want to run on the BSP.
337 *
338 *  Warning: %esi is live across this function.
339 */
340__INIT
341setup_once:
342	andl $0,setup_once_ref	/* Once is enough, thanks */
343	RET
344
345SYM_FUNC_START(early_idt_handler_array)
346	# 36(%esp) %eflags
347	# 32(%esp) %cs
348	# 28(%esp) %eip
349	# 24(%rsp) error code
350	i = 0
351	.rept NUM_EXCEPTION_VECTORS
352	.if ((EXCEPTION_ERRCODE_MASK >> i) & 1) == 0
353	pushl $0		# Dummy error code, to make stack frame uniform
354	.endif
355	pushl $i		# 20(%esp) Vector number
356	jmp early_idt_handler_common
357	i = i + 1
358	.fill early_idt_handler_array + i*EARLY_IDT_HANDLER_SIZE - ., 1, 0xcc
359	.endr
360SYM_FUNC_END(early_idt_handler_array)
361
362SYM_CODE_START_LOCAL(early_idt_handler_common)
363	/*
364	 * The stack is the hardware frame, an error code or zero, and the
365	 * vector number.
366	 */
367	cld
368
369	incl %ss:early_recursion_flag
370
371	/* The vector number is in pt_regs->gs */
372
373	cld
374	pushl	%fs		/* pt_regs->fs (__fsh varies by model) */
375	pushl	%es		/* pt_regs->es (__esh varies by model) */
376	pushl	%ds		/* pt_regs->ds (__dsh varies by model) */
377	pushl	%eax		/* pt_regs->ax */
378	pushl	%ebp		/* pt_regs->bp */
379	pushl	%edi		/* pt_regs->di */
380	pushl	%esi		/* pt_regs->si */
381	pushl	%edx		/* pt_regs->dx */
382	pushl	%ecx		/* pt_regs->cx */
383	pushl	%ebx		/* pt_regs->bx */
384
385	/* Fix up DS and ES */
386	movl	$(__KERNEL_DS), %ecx
387	movl	%ecx, %ds
388	movl	%ecx, %es
389
390	/* Load the vector number into EDX */
391	movl	PT_GS(%esp), %edx
392
393	/* Load GS into pt_regs->gs (and maybe clobber __gsh) */
394	movw	%gs, PT_GS(%esp)
395
396	movl	%esp, %eax	/* args are pt_regs (EAX), trapnr (EDX) */
397	call	early_fixup_exception
398
399	popl	%ebx		/* pt_regs->bx */
400	popl	%ecx		/* pt_regs->cx */
401	popl	%edx		/* pt_regs->dx */
402	popl	%esi		/* pt_regs->si */
403	popl	%edi		/* pt_regs->di */
404	popl	%ebp		/* pt_regs->bp */
405	popl	%eax		/* pt_regs->ax */
406	popl	%ds		/* pt_regs->ds (always ignores __dsh) */
407	popl	%es		/* pt_regs->es (always ignores __esh) */
408	popl	%fs		/* pt_regs->fs (always ignores __fsh) */
409	popl	%gs		/* pt_regs->gs (always ignores __gsh) */
410	decl	%ss:early_recursion_flag
411	addl	$4, %esp	/* pop pt_regs->orig_ax */
412	iret
413SYM_CODE_END(early_idt_handler_common)
414
415/* This is the default interrupt "handler" :-) */
416SYM_FUNC_START(early_ignore_irq)
417	cld
418#ifdef CONFIG_PRINTK
419	pushl %eax
420	pushl %ecx
421	pushl %edx
422	pushl %es
423	pushl %ds
424	movl $(__KERNEL_DS),%eax
425	movl %eax,%ds
426	movl %eax,%es
427	cmpl $2,early_recursion_flag
428	je hlt_loop
429	incl early_recursion_flag
430	pushl 16(%esp)
431	pushl 24(%esp)
432	pushl 32(%esp)
433	pushl 40(%esp)
434	pushl $int_msg
435	call _printk
436
437	call dump_stack
438
439	addl $(5*4),%esp
440	popl %ds
441	popl %es
442	popl %edx
443	popl %ecx
444	popl %eax
445#endif
446	iret
447
448hlt_loop:
449	hlt
450	jmp hlt_loop
451SYM_FUNC_END(early_ignore_irq)
452
453__INITDATA
454	.align 4
455SYM_DATA(early_recursion_flag, .long 0)
456
457__REFDATA
458	.align 4
459SYM_DATA(initial_code,		.long i386_start_kernel)
460SYM_DATA(setup_once_ref,	.long setup_once)
461
462#ifdef CONFIG_PAGE_TABLE_ISOLATION
463#define	PGD_ALIGN	(2 * PAGE_SIZE)
464#define PTI_USER_PGD_FILL	1024
465#else
466#define	PGD_ALIGN	(PAGE_SIZE)
467#define PTI_USER_PGD_FILL	0
468#endif
469/*
470 * BSS section
471 */
472__PAGE_ALIGNED_BSS
473	.align PGD_ALIGN
474#ifdef CONFIG_X86_PAE
475.globl initial_pg_pmd
476initial_pg_pmd:
477	.fill 1024*KPMDS,4,0
478#else
479.globl initial_page_table
480initial_page_table:
481	.fill 1024,4,0
482#endif
483	.align PGD_ALIGN
484initial_pg_fixmap:
485	.fill 1024,4,0
486.globl swapper_pg_dir
487	.align PGD_ALIGN
488swapper_pg_dir:
489	.fill 1024,4,0
490	.fill PTI_USER_PGD_FILL,4,0
491.globl empty_zero_page
492empty_zero_page:
493	.fill 4096,1,0
494EXPORT_SYMBOL(empty_zero_page)
495
496/*
497 * This starts the data section.
498 */
499#ifdef CONFIG_X86_PAE
500__PAGE_ALIGNED_DATA
501	/* Page-aligned for the benefit of paravirt? */
502	.align PGD_ALIGN
503SYM_DATA_START(initial_page_table)
504	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR),0	/* low identity map */
505# if KPMDS == 3
506	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR),0
507	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR+0x1000),0
508	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR+0x2000),0
509# elif KPMDS == 2
510	.long	0,0
511	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR),0
512	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR+0x1000),0
513# elif KPMDS == 1
514	.long	0,0
515	.long	0,0
516	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR),0
517# else
518#  error "Kernel PMDs should be 1, 2 or 3"
519# endif
520	.align PAGE_SIZE		/* needs to be page-sized too */
521
522#ifdef CONFIG_PAGE_TABLE_ISOLATION
523	/*
524	 * PTI needs another page so sync_initial_pagetable() works correctly
525	 * and does not scribble over the data which is placed behind the
526	 * actual initial_page_table. See clone_pgd_range().
527	 */
528	.fill 1024, 4, 0
529#endif
530
531SYM_DATA_END(initial_page_table)
532#endif
533
534.data
535.balign 4
536/*
537 * The SIZEOF_PTREGS gap is a convention which helps the in-kernel unwinder
538 * reliably detect the end of the stack.
539 */
540SYM_DATA(initial_stack,
541		.long init_thread_union + THREAD_SIZE -
542		SIZEOF_PTREGS - TOP_OF_KERNEL_STACK_PADDING)
543
544__INITRODATA
545int_msg:
546	.asciz "Unknown interrupt or fault at: %p %p %p\n"
547
548#include "../../x86/xen/xen-head.S"
549
550/*
551 * The IDT and GDT 'descriptors' are a strange 48-bit object
552 * only used by the lidt and lgdt instructions. They are not
553 * like usual segment descriptors - they consist of a 16-bit
554 * segment size, and 32-bit linear address value:
555 */
556
557	.data
558	ALIGN
559# early boot GDT descriptor (must use 1:1 address mapping)
560	.word 0				# 32 bit align gdt_desc.address
561SYM_DATA_START_LOCAL(boot_gdt_descr)
562	.word __BOOT_DS+7
563	.long boot_gdt - __PAGE_OFFSET
564SYM_DATA_END(boot_gdt_descr)
565
566# boot GDT descriptor (later on used by CPU#0):
567	.word 0				# 32 bit align gdt_desc.address
568SYM_DATA_START(early_gdt_descr)
569	.word GDT_ENTRIES*8-1
570	.long gdt_page			/* Overwritten for secondary CPUs */
571SYM_DATA_END(early_gdt_descr)
572
573/*
574 * The boot_gdt must mirror the equivalent in setup.S and is
575 * used only for booting.
576 */
577	.align L1_CACHE_BYTES
578SYM_DATA_START(boot_gdt)
579	.fill GDT_ENTRY_BOOT_CS,8,0
580	.quad 0x00cf9a000000ffff	/* kernel 4GB code at 0x00000000 */
581	.quad 0x00cf92000000ffff	/* kernel 4GB data at 0x00000000 */
582SYM_DATA_END(boot_gdt)
583