xref: /openbmc/linux/arch/x86/kernel/head_32.S (revision 15e3ae36) 
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#ifdef CONFIG_PARAVIRT
138	/* This is can only trip for a broken bootloader... */
139	cmpw $0x207, pa(boot_params + BP_version)
140	jb .Ldefault_entry
141
142	/* Paravirt-compatible boot parameters.  Look to see what architecture
143		we're booting under. */
144	movl pa(boot_params + BP_hardware_subarch), %eax
145	cmpl $num_subarch_entries, %eax
146	jae .Lbad_subarch
147
148	movl pa(subarch_entries)(,%eax,4), %eax
149	subl $__PAGE_OFFSET, %eax
150	jmp *%eax
151
152.Lbad_subarch:
153SYM_INNER_LABEL_ALIGN(xen_entry, SYM_L_WEAK)
154	/* Unknown implementation; there's really
155	   nothing we can do at this point. */
156	ud2a
157
158	__INITDATA
159
160subarch_entries:
161	.long .Ldefault_entry		/* normal x86/PC */
162	.long xen_entry			/* Xen hypervisor */
163	.long .Ldefault_entry		/* Moorestown MID */
164num_subarch_entries = (. - subarch_entries) / 4
165.previous
166#else
167	jmp .Ldefault_entry
168#endif /* CONFIG_PARAVIRT */
169SYM_CODE_END(startup_32)
170
171#ifdef CONFIG_HOTPLUG_CPU
172/*
173 * Boot CPU0 entry point. It's called from play_dead(). Everything has been set
174 * up already except stack. We just set up stack here. Then call
175 * start_secondary().
176 */
177SYM_FUNC_START(start_cpu0)
178	movl initial_stack, %ecx
179	movl %ecx, %esp
180	call *(initial_code)
1811:	jmp 1b
182SYM_FUNC_END(start_cpu0)
183#endif
184
185/*
186 * Non-boot CPU entry point; entered from trampoline.S
187 * We can't lgdt here, because lgdt itself uses a data segment, but
188 * we know the trampoline has already loaded the boot_gdt for us.
189 *
190 * If cpu hotplug is not supported then this code can go in init section
191 * which will be freed later
192 */
193SYM_FUNC_START(startup_32_smp)
194	cld
195	movl $(__BOOT_DS),%eax
196	movl %eax,%ds
197	movl %eax,%es
198	movl %eax,%fs
199	movl %eax,%gs
200	movl pa(initial_stack),%ecx
201	movl %eax,%ss
202	leal -__PAGE_OFFSET(%ecx),%esp
203
204#ifdef CONFIG_MICROCODE
205	/* Early load ucode on AP. */
206	call load_ucode_ap
207#endif
208
209.Ldefault_entry:
210	movl $(CR0_STATE & ~X86_CR0_PG),%eax
211	movl %eax,%cr0
212
213/*
214 * We want to start out with EFLAGS unambiguously cleared. Some BIOSes leave
215 * bits like NT set. This would confuse the debugger if this code is traced. So
216 * initialize them properly now before switching to protected mode. That means
217 * DF in particular (even though we have cleared it earlier after copying the
218 * command line) because GCC expects it.
219 */
220	pushl $0
221	popfl
222
223/*
224 * New page tables may be in 4Mbyte page mode and may be using the global pages.
225 *
226 * NOTE! If we are on a 486 we may have no cr4 at all! Specifically, cr4 exists
227 * if and only if CPUID exists and has flags other than the FPU flag set.
228 */
229	movl $-1,pa(X86_CPUID)		# preset CPUID level
230	movl $X86_EFLAGS_ID,%ecx
231	pushl %ecx
232	popfl				# set EFLAGS=ID
233	pushfl
234	popl %eax			# get EFLAGS
235	testl $X86_EFLAGS_ID,%eax	# did EFLAGS.ID remained set?
236	jz .Lenable_paging		# hw disallowed setting of ID bit
237					# which means no CPUID and no CR4
238
239	xorl %eax,%eax
240	cpuid
241	movl %eax,pa(X86_CPUID)		# save largest std CPUID function
242
243	movl $1,%eax
244	cpuid
245	andl $~1,%edx			# Ignore CPUID.FPU
246	jz .Lenable_paging		# No flags or only CPUID.FPU = no CR4
247
248	movl pa(mmu_cr4_features),%eax
249	movl %eax,%cr4
250
251	testb $X86_CR4_PAE, %al		# check if PAE is enabled
252	jz .Lenable_paging
253
254	/* Check if extended functions are implemented */
255	movl $0x80000000, %eax
256	cpuid
257	/* Value must be in the range 0x80000001 to 0x8000ffff */
258	subl $0x80000001, %eax
259	cmpl $(0x8000ffff-0x80000001), %eax
260	ja .Lenable_paging
261
262	/* Clear bogus XD_DISABLE bits */
263	call verify_cpu
264
265	mov $0x80000001, %eax
266	cpuid
267	/* Execute Disable bit supported? */
268	btl $(X86_FEATURE_NX & 31), %edx
269	jnc .Lenable_paging
270
271	/* Setup EFER (Extended Feature Enable Register) */
272	movl $MSR_EFER, %ecx
273	rdmsr
274
275	btsl $_EFER_NX, %eax
276	/* Make changes effective */
277	wrmsr
278
279.Lenable_paging:
280
281/*
282 * Enable paging
283 */
284	movl $pa(initial_page_table), %eax
285	movl %eax,%cr3		/* set the page table pointer.. */
286	movl $CR0_STATE,%eax
287	movl %eax,%cr0		/* ..and set paging (PG) bit */
288	ljmp $__BOOT_CS,$1f	/* Clear prefetch and normalize %eip */
2891:
290	/* Shift the stack pointer to a virtual address */
291	addl $__PAGE_OFFSET, %esp
292
293/*
294 * start system 32-bit setup. We need to re-do some of the things done
295 * in 16-bit mode for the "real" operations.
296 */
297	movl setup_once_ref,%eax
298	andl %eax,%eax
299	jz 1f				# Did we do this already?
300	call *%eax
3011:
302
303/*
304 * Check if it is 486
305 */
306	movb $4,X86			# at least 486
307	cmpl $-1,X86_CPUID
308	je .Lis486
309
310	/* get vendor info */
311	xorl %eax,%eax			# call CPUID with 0 -> return vendor ID
312	cpuid
313	movl %eax,X86_CPUID		# save CPUID level
314	movl %ebx,X86_VENDOR_ID		# lo 4 chars
315	movl %edx,X86_VENDOR_ID+4	# next 4 chars
316	movl %ecx,X86_VENDOR_ID+8	# last 4 chars
317
318	orl %eax,%eax			# do we have processor info as well?
319	je .Lis486
320
321	movl $1,%eax		# Use the CPUID instruction to get CPU type
322	cpuid
323	movb %al,%cl		# save reg for future use
324	andb $0x0f,%ah		# mask processor family
325	movb %ah,X86
326	andb $0xf0,%al		# mask model
327	shrb $4,%al
328	movb %al,X86_MODEL
329	andb $0x0f,%cl		# mask mask revision
330	movb %cl,X86_STEPPING
331	movl %edx,X86_CAPABILITY
332
333.Lis486:
334	movl $0x50022,%ecx	# set AM, WP, NE and MP
335	movl %cr0,%eax
336	andl $0x80000011,%eax	# Save PG,PE,ET
337	orl %ecx,%eax
338	movl %eax,%cr0
339
340	lgdt early_gdt_descr
341	ljmp $(__KERNEL_CS),$1f
3421:	movl $(__KERNEL_DS),%eax	# reload all the segment registers
343	movl %eax,%ss			# after changing gdt.
344
345	movl $(__USER_DS),%eax		# DS/ES contains default USER segment
346	movl %eax,%ds
347	movl %eax,%es
348
349	movl $(__KERNEL_PERCPU), %eax
350	movl %eax,%fs			# set this cpu's percpu
351
352	movl $(__KERNEL_STACK_CANARY),%eax
353	movl %eax,%gs
354
355	xorl %eax,%eax			# Clear LDT
356	lldt %ax
357
358	call *(initial_code)
3591:	jmp 1b
360SYM_FUNC_END(startup_32_smp)
361
362#include "verify_cpu.S"
363
364/*
365 *  setup_once
366 *
367 *  The setup work we only want to run on the BSP.
368 *
369 *  Warning: %esi is live across this function.
370 */
371__INIT
372setup_once:
373#ifdef CONFIG_STACKPROTECTOR
374	/*
375	 * Configure the stack canary. The linker can't handle this by
376	 * relocation.  Manually set base address in stack canary
377	 * segment descriptor.
378	 */
379	movl $gdt_page,%eax
380	movl $stack_canary,%ecx
381	movw %cx, 8 * GDT_ENTRY_STACK_CANARY + 2(%eax)
382	shrl $16, %ecx
383	movb %cl, 8 * GDT_ENTRY_STACK_CANARY + 4(%eax)
384	movb %ch, 8 * GDT_ENTRY_STACK_CANARY + 7(%eax)
385#endif
386
387	andl $0,setup_once_ref	/* Once is enough, thanks */
388	ret
389
390SYM_FUNC_START(early_idt_handler_array)
391	# 36(%esp) %eflags
392	# 32(%esp) %cs
393	# 28(%esp) %eip
394	# 24(%rsp) error code
395	i = 0
396	.rept NUM_EXCEPTION_VECTORS
397	.if ((EXCEPTION_ERRCODE_MASK >> i) & 1) == 0
398	pushl $0		# Dummy error code, to make stack frame uniform
399	.endif
400	pushl $i		# 20(%esp) Vector number
401	jmp early_idt_handler_common
402	i = i + 1
403	.fill early_idt_handler_array + i*EARLY_IDT_HANDLER_SIZE - ., 1, 0xcc
404	.endr
405SYM_FUNC_END(early_idt_handler_array)
406
407SYM_CODE_START_LOCAL(early_idt_handler_common)
408	/*
409	 * The stack is the hardware frame, an error code or zero, and the
410	 * vector number.
411	 */
412	cld
413
414	incl %ss:early_recursion_flag
415
416	/* The vector number is in pt_regs->gs */
417
418	cld
419	pushl	%fs		/* pt_regs->fs (__fsh varies by model) */
420	pushl	%es		/* pt_regs->es (__esh varies by model) */
421	pushl	%ds		/* pt_regs->ds (__dsh varies by model) */
422	pushl	%eax		/* pt_regs->ax */
423	pushl	%ebp		/* pt_regs->bp */
424	pushl	%edi		/* pt_regs->di */
425	pushl	%esi		/* pt_regs->si */
426	pushl	%edx		/* pt_regs->dx */
427	pushl	%ecx		/* pt_regs->cx */
428	pushl	%ebx		/* pt_regs->bx */
429
430	/* Fix up DS and ES */
431	movl	$(__KERNEL_DS), %ecx
432	movl	%ecx, %ds
433	movl	%ecx, %es
434
435	/* Load the vector number into EDX */
436	movl	PT_GS(%esp), %edx
437
438	/* Load GS into pt_regs->gs (and maybe clobber __gsh) */
439	movw	%gs, PT_GS(%esp)
440
441	movl	%esp, %eax	/* args are pt_regs (EAX), trapnr (EDX) */
442	call	early_fixup_exception
443
444	popl	%ebx		/* pt_regs->bx */
445	popl	%ecx		/* pt_regs->cx */
446	popl	%edx		/* pt_regs->dx */
447	popl	%esi		/* pt_regs->si */
448	popl	%edi		/* pt_regs->di */
449	popl	%ebp		/* pt_regs->bp */
450	popl	%eax		/* pt_regs->ax */
451	popl	%ds		/* pt_regs->ds (always ignores __dsh) */
452	popl	%es		/* pt_regs->es (always ignores __esh) */
453	popl	%fs		/* pt_regs->fs (always ignores __fsh) */
454	popl	%gs		/* pt_regs->gs (always ignores __gsh) */
455	decl	%ss:early_recursion_flag
456	addl	$4, %esp	/* pop pt_regs->orig_ax */
457	iret
458SYM_CODE_END(early_idt_handler_common)
459
460/* This is the default interrupt "handler" :-) */
461SYM_FUNC_START(early_ignore_irq)
462	cld
463#ifdef CONFIG_PRINTK
464	pushl %eax
465	pushl %ecx
466	pushl %edx
467	pushl %es
468	pushl %ds
469	movl $(__KERNEL_DS),%eax
470	movl %eax,%ds
471	movl %eax,%es
472	cmpl $2,early_recursion_flag
473	je hlt_loop
474	incl early_recursion_flag
475	pushl 16(%esp)
476	pushl 24(%esp)
477	pushl 32(%esp)
478	pushl 40(%esp)
479	pushl $int_msg
480	call printk
481
482	call dump_stack
483
484	addl $(5*4),%esp
485	popl %ds
486	popl %es
487	popl %edx
488	popl %ecx
489	popl %eax
490#endif
491	iret
492
493hlt_loop:
494	hlt
495	jmp hlt_loop
496SYM_FUNC_END(early_ignore_irq)
497
498__INITDATA
499	.align 4
500SYM_DATA(early_recursion_flag, .long 0)
501
502__REFDATA
503	.align 4
504SYM_DATA(initial_code,		.long i386_start_kernel)
505SYM_DATA(setup_once_ref,	.long setup_once)
506
507#ifdef CONFIG_PAGE_TABLE_ISOLATION
508#define	PGD_ALIGN	(2 * PAGE_SIZE)
509#define PTI_USER_PGD_FILL	1024
510#else
511#define	PGD_ALIGN	(PAGE_SIZE)
512#define PTI_USER_PGD_FILL	0
513#endif
514/*
515 * BSS section
516 */
517__PAGE_ALIGNED_BSS
518	.align PGD_ALIGN
519#ifdef CONFIG_X86_PAE
520.globl initial_pg_pmd
521initial_pg_pmd:
522	.fill 1024*KPMDS,4,0
523#else
524.globl initial_page_table
525initial_page_table:
526	.fill 1024,4,0
527#endif
528	.align PGD_ALIGN
529initial_pg_fixmap:
530	.fill 1024,4,0
531.globl swapper_pg_dir
532	.align PGD_ALIGN
533swapper_pg_dir:
534	.fill 1024,4,0
535	.fill PTI_USER_PGD_FILL,4,0
536.globl empty_zero_page
537empty_zero_page:
538	.fill 4096,1,0
539EXPORT_SYMBOL(empty_zero_page)
540
541/*
542 * This starts the data section.
543 */
544#ifdef CONFIG_X86_PAE
545__PAGE_ALIGNED_DATA
546	/* Page-aligned for the benefit of paravirt? */
547	.align PGD_ALIGN
548SYM_DATA_START(initial_page_table)
549	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR),0	/* low identity map */
550# if KPMDS == 3
551	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR),0
552	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR+0x1000),0
553	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR+0x2000),0
554# elif KPMDS == 2
555	.long	0,0
556	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR),0
557	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR+0x1000),0
558# elif KPMDS == 1
559	.long	0,0
560	.long	0,0
561	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR),0
562# else
563#  error "Kernel PMDs should be 1, 2 or 3"
564# endif
565	.align PAGE_SIZE		/* needs to be page-sized too */
566
567#ifdef CONFIG_PAGE_TABLE_ISOLATION
568	/*
569	 * PTI needs another page so sync_initial_pagetable() works correctly
570	 * and does not scribble over the data which is placed behind the
571	 * actual initial_page_table. See clone_pgd_range().
572	 */
573	.fill 1024, 4, 0
574#endif
575
576SYM_DATA_END(initial_page_table)
577#endif
578
579.data
580.balign 4
581/*
582 * The SIZEOF_PTREGS gap is a convention which helps the in-kernel unwinder
583 * reliably detect the end of the stack.
584 */
585SYM_DATA(initial_stack,
586		.long init_thread_union + THREAD_SIZE -
587		SIZEOF_PTREGS - TOP_OF_KERNEL_STACK_PADDING)
588
589__INITRODATA
590int_msg:
591	.asciz "Unknown interrupt or fault at: %p %p %p\n"
592
593#include "../../x86/xen/xen-head.S"
594
595/*
596 * The IDT and GDT 'descriptors' are a strange 48-bit object
597 * only used by the lidt and lgdt instructions. They are not
598 * like usual segment descriptors - they consist of a 16-bit
599 * segment size, and 32-bit linear address value:
600 */
601
602	.data
603	ALIGN
604# early boot GDT descriptor (must use 1:1 address mapping)
605	.word 0				# 32 bit align gdt_desc.address
606SYM_DATA_START_LOCAL(boot_gdt_descr)
607	.word __BOOT_DS+7
608	.long boot_gdt - __PAGE_OFFSET
609SYM_DATA_END(boot_gdt_descr)
610
611# boot GDT descriptor (later on used by CPU#0):
612	.word 0				# 32 bit align gdt_desc.address
613SYM_DATA_START(early_gdt_descr)
614	.word GDT_ENTRIES*8-1
615	.long gdt_page			/* Overwritten for secondary CPUs */
616SYM_DATA_END(early_gdt_descr)
617
618/*
619 * The boot_gdt must mirror the equivalent in setup.S and is
620 * used only for booting.
621 */
622	.align L1_CACHE_BYTES
623SYM_DATA_START(boot_gdt)
624	.fill GDT_ENTRY_BOOT_CS,8,0
625	.quad 0x00cf9a000000ffff	/* kernel 4GB code at 0x00000000 */
626	.quad 0x00cf92000000ffff	/* kernel 4GB data at 0x00000000 */
627SYM_DATA_END(boot_gdt)
628