xref: /openbmc/linux/arch/x86/kernel/head_32.S (revision 60772e48) 
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
67ENTRY(startup_32)
68	movl pa(initial_stack),%ecx
69
70	/* test KEEP_SEGMENTS flag to see if the bootloader is asking
71		us to not reload segments */
72	testb $KEEP_SEGMENTS, BP_loadflags(%esi)
73	jnz 2f
74
75/*
76 * Set segments to known values.
77 */
78	lgdt pa(boot_gdt_descr)
79	movl $(__BOOT_DS),%eax
80	movl %eax,%ds
81	movl %eax,%es
82	movl %eax,%fs
83	movl %eax,%gs
84	movl %eax,%ss
852:
86	leal -__PAGE_OFFSET(%ecx),%esp
87
88/*
89 * Clear BSS first so that there are no surprises...
90 */
91	cld
92	xorl %eax,%eax
93	movl $pa(__bss_start),%edi
94	movl $pa(__bss_stop),%ecx
95	subl %edi,%ecx
96	shrl $2,%ecx
97	rep ; stosl
98/*
99 * Copy bootup parameters out of the way.
100 * Note: %esi still has the pointer to the real-mode data.
101 * With the kexec as boot loader, parameter segment might be loaded beyond
102 * kernel image and might not even be addressable by early boot page tables.
103 * (kexec on panic case). Hence copy out the parameters before initializing
104 * page tables.
105 */
106	movl $pa(boot_params),%edi
107	movl $(PARAM_SIZE/4),%ecx
108	cld
109	rep
110	movsl
111	movl pa(boot_params) + NEW_CL_POINTER,%esi
112	andl %esi,%esi
113	jz 1f			# No command line
114	movl $pa(boot_command_line),%edi
115	movl $(COMMAND_LINE_SIZE/4),%ecx
116	rep
117	movsl
1181:
119
120#ifdef CONFIG_OLPC
121	/* save OFW's pgdir table for later use when calling into OFW */
122	movl %cr3, %eax
123	movl %eax, pa(olpc_ofw_pgd)
124#endif
125
126#ifdef CONFIG_MICROCODE
127	/* Early load ucode on BSP. */
128	call load_ucode_bsp
129#endif
130
131	/* Create early pagetables. */
132	call  mk_early_pgtbl_32
133
134	/* Do early initialization of the fixmap area */
135	movl $pa(initial_pg_fixmap)+PDE_IDENT_ATTR,%eax
136#ifdef  CONFIG_X86_PAE
137#define KPMDS (((-__PAGE_OFFSET) >> 30) & 3) /* Number of kernel PMDs */
138	movl %eax,pa(initial_pg_pmd+0x1000*KPMDS-8)
139#else
140	movl %eax,pa(initial_page_table+0xffc)
141#endif
142
143#ifdef CONFIG_PARAVIRT
144	/* This is can only trip for a broken bootloader... */
145	cmpw $0x207, pa(boot_params + BP_version)
146	jb .Ldefault_entry
147
148	/* Paravirt-compatible boot parameters.  Look to see what architecture
149		we're booting under. */
150	movl pa(boot_params + BP_hardware_subarch), %eax
151	cmpl $num_subarch_entries, %eax
152	jae .Lbad_subarch
153
154	movl pa(subarch_entries)(,%eax,4), %eax
155	subl $__PAGE_OFFSET, %eax
156	jmp *%eax
157
158.Lbad_subarch:
159WEAK(xen_entry)
160	/* Unknown implementation; there's really
161	   nothing we can do at this point. */
162	ud2a
163
164	__INITDATA
165
166subarch_entries:
167	.long .Ldefault_entry		/* normal x86/PC */
168	.long xen_entry			/* Xen hypervisor */
169	.long .Ldefault_entry		/* Moorestown MID */
170num_subarch_entries = (. - subarch_entries) / 4
171.previous
172#else
173	jmp .Ldefault_entry
174#endif /* CONFIG_PARAVIRT */
175
176#ifdef CONFIG_HOTPLUG_CPU
177/*
178 * Boot CPU0 entry point. It's called from play_dead(). Everything has been set
179 * up already except stack. We just set up stack here. Then call
180 * start_secondary().
181 */
182ENTRY(start_cpu0)
183	movl initial_stack, %ecx
184	movl %ecx, %esp
185	call *(initial_code)
1861:	jmp 1b
187ENDPROC(start_cpu0)
188#endif
189
190/*
191 * Non-boot CPU entry point; entered from trampoline.S
192 * We can't lgdt here, because lgdt itself uses a data segment, but
193 * we know the trampoline has already loaded the boot_gdt for us.
194 *
195 * If cpu hotplug is not supported then this code can go in init section
196 * which will be freed later
197 */
198ENTRY(startup_32_smp)
199	cld
200	movl $(__BOOT_DS),%eax
201	movl %eax,%ds
202	movl %eax,%es
203	movl %eax,%fs
204	movl %eax,%gs
205	movl pa(initial_stack),%ecx
206	movl %eax,%ss
207	leal -__PAGE_OFFSET(%ecx),%esp
208
209#ifdef CONFIG_MICROCODE
210	/* Early load ucode on AP. */
211	call load_ucode_ap
212#endif
213
214.Ldefault_entry:
215	movl $(CR0_STATE & ~X86_CR0_PG),%eax
216	movl %eax,%cr0
217
218/*
219 * We want to start out with EFLAGS unambiguously cleared. Some BIOSes leave
220 * bits like NT set. This would confuse the debugger if this code is traced. So
221 * initialize them properly now before switching to protected mode. That means
222 * DF in particular (even though we have cleared it earlier after copying the
223 * command line) because GCC expects it.
224 */
225	pushl $0
226	popfl
227
228/*
229 * New page tables may be in 4Mbyte page mode and may be using the global pages.
230 *
231 * NOTE! If we are on a 486 we may have no cr4 at all! Specifically, cr4 exists
232 * if and only if CPUID exists and has flags other than the FPU flag set.
233 */
234	movl $-1,pa(X86_CPUID)		# preset CPUID level
235	movl $X86_EFLAGS_ID,%ecx
236	pushl %ecx
237	popfl				# set EFLAGS=ID
238	pushfl
239	popl %eax			# get EFLAGS
240	testl $X86_EFLAGS_ID,%eax	# did EFLAGS.ID remained set?
241	jz .Lenable_paging		# hw disallowed setting of ID bit
242					# which means no CPUID and no CR4
243
244	xorl %eax,%eax
245	cpuid
246	movl %eax,pa(X86_CPUID)		# save largest std CPUID function
247
248	movl $1,%eax
249	cpuid
250	andl $~1,%edx			# Ignore CPUID.FPU
251	jz .Lenable_paging		# No flags or only CPUID.FPU = no CR4
252
253	movl pa(mmu_cr4_features),%eax
254	movl %eax,%cr4
255
256	testb $X86_CR4_PAE, %al		# check if PAE is enabled
257	jz .Lenable_paging
258
259	/* Check if extended functions are implemented */
260	movl $0x80000000, %eax
261	cpuid
262	/* Value must be in the range 0x80000001 to 0x8000ffff */
263	subl $0x80000001, %eax
264	cmpl $(0x8000ffff-0x80000001), %eax
265	ja .Lenable_paging
266
267	/* Clear bogus XD_DISABLE bits */
268	call verify_cpu
269
270	mov $0x80000001, %eax
271	cpuid
272	/* Execute Disable bit supported? */
273	btl $(X86_FEATURE_NX & 31), %edx
274	jnc .Lenable_paging
275
276	/* Setup EFER (Extended Feature Enable Register) */
277	movl $MSR_EFER, %ecx
278	rdmsr
279
280	btsl $_EFER_NX, %eax
281	/* Make changes effective */
282	wrmsr
283
284.Lenable_paging:
285
286/*
287 * Enable paging
288 */
289	movl $pa(initial_page_table), %eax
290	movl %eax,%cr3		/* set the page table pointer.. */
291	movl $CR0_STATE,%eax
292	movl %eax,%cr0		/* ..and set paging (PG) bit */
293	ljmp $__BOOT_CS,$1f	/* Clear prefetch and normalize %eip */
2941:
295	/* Shift the stack pointer to a virtual address */
296	addl $__PAGE_OFFSET, %esp
297
298/*
299 * start system 32-bit setup. We need to re-do some of the things done
300 * in 16-bit mode for the "real" operations.
301 */
302	movl setup_once_ref,%eax
303	andl %eax,%eax
304	jz 1f				# Did we do this already?
305	call *%eax
3061:
307
308/*
309 * Check if it is 486
310 */
311	movb $4,X86			# at least 486
312	cmpl $-1,X86_CPUID
313	je .Lis486
314
315	/* get vendor info */
316	xorl %eax,%eax			# call CPUID with 0 -> return vendor ID
317	cpuid
318	movl %eax,X86_CPUID		# save CPUID level
319	movl %ebx,X86_VENDOR_ID		# lo 4 chars
320	movl %edx,X86_VENDOR_ID+4	# next 4 chars
321	movl %ecx,X86_VENDOR_ID+8	# last 4 chars
322
323	orl %eax,%eax			# do we have processor info as well?
324	je .Lis486
325
326	movl $1,%eax		# Use the CPUID instruction to get CPU type
327	cpuid
328	movb %al,%cl		# save reg for future use
329	andb $0x0f,%ah		# mask processor family
330	movb %ah,X86
331	andb $0xf0,%al		# mask model
332	shrb $4,%al
333	movb %al,X86_MODEL
334	andb $0x0f,%cl		# mask mask revision
335	movb %cl,X86_STEPPING
336	movl %edx,X86_CAPABILITY
337
338.Lis486:
339	movl $0x50022,%ecx	# set AM, WP, NE and MP
340	movl %cr0,%eax
341	andl $0x80000011,%eax	# Save PG,PE,ET
342	orl %ecx,%eax
343	movl %eax,%cr0
344
345	lgdt early_gdt_descr
346	ljmp $(__KERNEL_CS),$1f
3471:	movl $(__KERNEL_DS),%eax	# reload all the segment registers
348	movl %eax,%ss			# after changing gdt.
349
350	movl $(__USER_DS),%eax		# DS/ES contains default USER segment
351	movl %eax,%ds
352	movl %eax,%es
353
354	movl $(__KERNEL_PERCPU), %eax
355	movl %eax,%fs			# set this cpu's percpu
356
357	movl $(__KERNEL_STACK_CANARY),%eax
358	movl %eax,%gs
359
360	xorl %eax,%eax			# Clear LDT
361	lldt %ax
362
363	call *(initial_code)
3641:	jmp 1b
365ENDPROC(startup_32_smp)
366
367#include "verify_cpu.S"
368
369/*
370 *  setup_once
371 *
372 *  The setup work we only want to run on the BSP.
373 *
374 *  Warning: %esi is live across this function.
375 */
376__INIT
377setup_once:
378#ifdef CONFIG_CC_STACKPROTECTOR
379	/*
380	 * Configure the stack canary. The linker can't handle this by
381	 * relocation.  Manually set base address in stack canary
382	 * segment descriptor.
383	 */
384	movl $gdt_page,%eax
385	movl $stack_canary,%ecx
386	movw %cx, 8 * GDT_ENTRY_STACK_CANARY + 2(%eax)
387	shrl $16, %ecx
388	movb %cl, 8 * GDT_ENTRY_STACK_CANARY + 4(%eax)
389	movb %ch, 8 * GDT_ENTRY_STACK_CANARY + 7(%eax)
390#endif
391
392	andl $0,setup_once_ref	/* Once is enough, thanks */
393	ret
394
395ENTRY(early_idt_handler_array)
396	# 36(%esp) %eflags
397	# 32(%esp) %cs
398	# 28(%esp) %eip
399	# 24(%rsp) error code
400	i = 0
401	.rept NUM_EXCEPTION_VECTORS
402	.if ((EXCEPTION_ERRCODE_MASK >> i) & 1) == 0
403	pushl $0		# Dummy error code, to make stack frame uniform
404	.endif
405	pushl $i		# 20(%esp) Vector number
406	jmp early_idt_handler_common
407	i = i + 1
408	.fill early_idt_handler_array + i*EARLY_IDT_HANDLER_SIZE - ., 1, 0xcc
409	.endr
410ENDPROC(early_idt_handler_array)
411
412early_idt_handler_common:
413	/*
414	 * The stack is the hardware frame, an error code or zero, and the
415	 * vector number.
416	 */
417	cld
418
419	incl %ss:early_recursion_flag
420
421	/* The vector number is in pt_regs->gs */
422
423	cld
424	pushl	%fs		/* pt_regs->fs (__fsh varies by model) */
425	pushl	%es		/* pt_regs->es (__esh varies by model) */
426	pushl	%ds		/* pt_regs->ds (__dsh varies by model) */
427	pushl	%eax		/* pt_regs->ax */
428	pushl	%ebp		/* pt_regs->bp */
429	pushl	%edi		/* pt_regs->di */
430	pushl	%esi		/* pt_regs->si */
431	pushl	%edx		/* pt_regs->dx */
432	pushl	%ecx		/* pt_regs->cx */
433	pushl	%ebx		/* pt_regs->bx */
434
435	/* Fix up DS and ES */
436	movl	$(__KERNEL_DS), %ecx
437	movl	%ecx, %ds
438	movl	%ecx, %es
439
440	/* Load the vector number into EDX */
441	movl	PT_GS(%esp), %edx
442
443	/* Load GS into pt_regs->gs (and maybe clobber __gsh) */
444	movw	%gs, PT_GS(%esp)
445
446	movl	%esp, %eax	/* args are pt_regs (EAX), trapnr (EDX) */
447	call	early_fixup_exception
448
449	popl	%ebx		/* pt_regs->bx */
450	popl	%ecx		/* pt_regs->cx */
451	popl	%edx		/* pt_regs->dx */
452	popl	%esi		/* pt_regs->si */
453	popl	%edi		/* pt_regs->di */
454	popl	%ebp		/* pt_regs->bp */
455	popl	%eax		/* pt_regs->ax */
456	popl	%ds		/* pt_regs->ds (always ignores __dsh) */
457	popl	%es		/* pt_regs->es (always ignores __esh) */
458	popl	%fs		/* pt_regs->fs (always ignores __fsh) */
459	popl	%gs		/* pt_regs->gs (always ignores __gsh) */
460	decl	%ss:early_recursion_flag
461	addl	$4, %esp	/* pop pt_regs->orig_ax */
462	iret
463ENDPROC(early_idt_handler_common)
464
465/* This is the default interrupt "handler" :-) */
466ENTRY(early_ignore_irq)
467	cld
468#ifdef CONFIG_PRINTK
469	pushl %eax
470	pushl %ecx
471	pushl %edx
472	pushl %es
473	pushl %ds
474	movl $(__KERNEL_DS),%eax
475	movl %eax,%ds
476	movl %eax,%es
477	cmpl $2,early_recursion_flag
478	je hlt_loop
479	incl early_recursion_flag
480	pushl 16(%esp)
481	pushl 24(%esp)
482	pushl 32(%esp)
483	pushl 40(%esp)
484	pushl $int_msg
485	call printk
486
487	call dump_stack
488
489	addl $(5*4),%esp
490	popl %ds
491	popl %es
492	popl %edx
493	popl %ecx
494	popl %eax
495#endif
496	iret
497
498hlt_loop:
499	hlt
500	jmp hlt_loop
501ENDPROC(early_ignore_irq)
502
503__INITDATA
504	.align 4
505GLOBAL(early_recursion_flag)
506	.long 0
507
508__REFDATA
509	.align 4
510ENTRY(initial_code)
511	.long i386_start_kernel
512ENTRY(setup_once_ref)
513	.long setup_once
514
515/*
516 * BSS section
517 */
518__PAGE_ALIGNED_BSS
519	.align PAGE_SIZE
520#ifdef CONFIG_X86_PAE
521.globl initial_pg_pmd
522initial_pg_pmd:
523	.fill 1024*KPMDS,4,0
524#else
525.globl initial_page_table
526initial_page_table:
527	.fill 1024,4,0
528#endif
529initial_pg_fixmap:
530	.fill 1024,4,0
531.globl empty_zero_page
532empty_zero_page:
533	.fill 4096,1,0
534.globl swapper_pg_dir
535swapper_pg_dir:
536	.fill 1024,4,0
537EXPORT_SYMBOL(empty_zero_page)
538
539/*
540 * This starts the data section.
541 */
542#ifdef CONFIG_X86_PAE
543__PAGE_ALIGNED_DATA
544	/* Page-aligned for the benefit of paravirt? */
545	.align PAGE_SIZE
546ENTRY(initial_page_table)
547	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR),0	/* low identity map */
548# if KPMDS == 3
549	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR),0
550	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR+0x1000),0
551	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR+0x2000),0
552# elif KPMDS == 2
553	.long	0,0
554	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR),0
555	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR+0x1000),0
556# elif KPMDS == 1
557	.long	0,0
558	.long	0,0
559	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR),0
560# else
561#  error "Kernel PMDs should be 1, 2 or 3"
562# endif
563	.align PAGE_SIZE		/* needs to be page-sized too */
564#endif
565
566.data
567.balign 4
568ENTRY(initial_stack)
569	/*
570	 * The SIZEOF_PTREGS gap is a convention which helps the in-kernel
571	 * unwinder reliably detect the end of the stack.
572	 */
573	.long init_thread_union + THREAD_SIZE - SIZEOF_PTREGS - \
574	      TOP_OF_KERNEL_STACK_PADDING;
575
576__INITRODATA
577int_msg:
578	.asciz "Unknown interrupt or fault at: %p %p %p\n"
579
580#include "../../x86/xen/xen-head.S"
581
582/*
583 * The IDT and GDT 'descriptors' are a strange 48-bit object
584 * only used by the lidt and lgdt instructions. They are not
585 * like usual segment descriptors - they consist of a 16-bit
586 * segment size, and 32-bit linear address value:
587 */
588
589	.data
590.globl boot_gdt_descr
591
592	ALIGN
593# early boot GDT descriptor (must use 1:1 address mapping)
594	.word 0				# 32 bit align gdt_desc.address
595boot_gdt_descr:
596	.word __BOOT_DS+7
597	.long boot_gdt - __PAGE_OFFSET
598
599# boot GDT descriptor (later on used by CPU#0):
600	.word 0				# 32 bit align gdt_desc.address
601ENTRY(early_gdt_descr)
602	.word GDT_ENTRIES*8-1
603	.long gdt_page			/* Overwritten for secondary CPUs */
604
605/*
606 * The boot_gdt must mirror the equivalent in setup.S and is
607 * used only for booting.
608 */
609	.align L1_CACHE_BYTES
610ENTRY(boot_gdt)
611	.fill GDT_ENTRY_BOOT_CS,8,0
612	.quad 0x00cf9a000000ffff	/* kernel 4GB code at 0x00000000 */
613	.quad 0x00cf92000000ffff	/* kernel 4GB data at 0x00000000 */
614