xref: /openbmc/linux/arch/x86/kernel/head_32.S (revision 711aab1d) 
1/*
2 *
3 *  Copyright (C) 1991, 1992  Linus Torvalds
4 *
5 *  Enhanced CPU detection and feature setting code by Mike Jagdis
6 *  and Martin Mares, November 1997.
7 */
8
9.text
10#include <linux/threads.h>
11#include <linux/init.h>
12#include <linux/linkage.h>
13#include <asm/segment.h>
14#include <asm/page_types.h>
15#include <asm/pgtable_types.h>
16#include <asm/cache.h>
17#include <asm/thread_info.h>
18#include <asm/asm-offsets.h>
19#include <asm/setup.h>
20#include <asm/processor-flags.h>
21#include <asm/msr-index.h>
22#include <asm/cpufeatures.h>
23#include <asm/percpu.h>
24#include <asm/nops.h>
25#include <asm/bootparam.h>
26#include <asm/export.h>
27#include <asm/pgtable_32.h>
28
29/* Physical address */
30#define pa(X) ((X) - __PAGE_OFFSET)
31
32/*
33 * References to members of the new_cpu_data structure.
34 */
35
36#define X86		new_cpu_data+CPUINFO_x86
37#define X86_VENDOR	new_cpu_data+CPUINFO_x86_vendor
38#define X86_MODEL	new_cpu_data+CPUINFO_x86_model
39#define X86_MASK	new_cpu_data+CPUINFO_x86_mask
40#define X86_HARD_MATH	new_cpu_data+CPUINFO_hard_math
41#define X86_CPUID	new_cpu_data+CPUINFO_cpuid_level
42#define X86_CAPABILITY	new_cpu_data+CPUINFO_x86_capability
43#define X86_VENDOR_ID	new_cpu_data+CPUINFO_x86_vendor_id
44
45
46#define SIZEOF_PTREGS 17*4
47
48/*
49 * Worst-case size of the kernel mapping we need to make:
50 * a relocatable kernel can live anywhere in lowmem, so we need to be able
51 * to map all of lowmem.
52 */
53KERNEL_PAGES = LOWMEM_PAGES
54
55INIT_MAP_SIZE = PAGE_TABLE_SIZE(KERNEL_PAGES) * PAGE_SIZE
56RESERVE_BRK(pagetables, INIT_MAP_SIZE)
57
58/*
59 * 32-bit kernel entrypoint; only used by the boot CPU.  On entry,
60 * %esi points to the real-mode code as a 32-bit pointer.
61 * CS and DS must be 4 GB flat segments, but we don't depend on
62 * any particular GDT layout, because we load our own as soon as we
63 * can.
64 */
65__HEAD
66ENTRY(startup_32)
67	movl pa(initial_stack),%ecx
68
69	/* test KEEP_SEGMENTS flag to see if the bootloader is asking
70		us to not reload segments */
71	testb $KEEP_SEGMENTS, BP_loadflags(%esi)
72	jnz 2f
73
74/*
75 * Set segments to known values.
76 */
77	lgdt pa(boot_gdt_descr)
78	movl $(__BOOT_DS),%eax
79	movl %eax,%ds
80	movl %eax,%es
81	movl %eax,%fs
82	movl %eax,%gs
83	movl %eax,%ss
842:
85	leal -__PAGE_OFFSET(%ecx),%esp
86
87/*
88 * Clear BSS first so that there are no surprises...
89 */
90	cld
91	xorl %eax,%eax
92	movl $pa(__bss_start),%edi
93	movl $pa(__bss_stop),%ecx
94	subl %edi,%ecx
95	shrl $2,%ecx
96	rep ; stosl
97/*
98 * Copy bootup parameters out of the way.
99 * Note: %esi still has the pointer to the real-mode data.
100 * With the kexec as boot loader, parameter segment might be loaded beyond
101 * kernel image and might not even be addressable by early boot page tables.
102 * (kexec on panic case). Hence copy out the parameters before initializing
103 * page tables.
104 */
105	movl $pa(boot_params),%edi
106	movl $(PARAM_SIZE/4),%ecx
107	cld
108	rep
109	movsl
110	movl pa(boot_params) + NEW_CL_POINTER,%esi
111	andl %esi,%esi
112	jz 1f			# No command line
113	movl $pa(boot_command_line),%edi
114	movl $(COMMAND_LINE_SIZE/4),%ecx
115	rep
116	movsl
1171:
118
119#ifdef CONFIG_OLPC
120	/* save OFW's pgdir table for later use when calling into OFW */
121	movl %cr3, %eax
122	movl %eax, pa(olpc_ofw_pgd)
123#endif
124
125#ifdef CONFIG_MICROCODE
126	/* Early load ucode on BSP. */
127	call load_ucode_bsp
128#endif
129
130	/* Create early pagetables. */
131	call  mk_early_pgtbl_32
132
133	/* Do early initialization of the fixmap area */
134	movl $pa(initial_pg_fixmap)+PDE_IDENT_ATTR,%eax
135#ifdef  CONFIG_X86_PAE
136#define KPMDS (((-__PAGE_OFFSET) >> 30) & 3) /* Number of kernel PMDs */
137	movl %eax,pa(initial_pg_pmd+0x1000*KPMDS-8)
138#else
139	movl %eax,pa(initial_page_table+0xffc)
140#endif
141
142#ifdef CONFIG_PARAVIRT
143	/* This is can only trip for a broken bootloader... */
144	cmpw $0x207, pa(boot_params + BP_version)
145	jb .Ldefault_entry
146
147	/* Paravirt-compatible boot parameters.  Look to see what architecture
148		we're booting under. */
149	movl pa(boot_params + BP_hardware_subarch), %eax
150	cmpl $num_subarch_entries, %eax
151	jae .Lbad_subarch
152
153	movl pa(subarch_entries)(,%eax,4), %eax
154	subl $__PAGE_OFFSET, %eax
155	jmp *%eax
156
157.Lbad_subarch:
158WEAK(xen_entry)
159	/* Unknown implementation; there's really
160	   nothing we can do at this point. */
161	ud2a
162
163	__INITDATA
164
165subarch_entries:
166	.long .Ldefault_entry		/* normal x86/PC */
167	.long xen_entry			/* Xen hypervisor */
168	.long .Ldefault_entry		/* Moorestown MID */
169num_subarch_entries = (. - subarch_entries) / 4
170.previous
171#else
172	jmp .Ldefault_entry
173#endif /* CONFIG_PARAVIRT */
174
175#ifdef CONFIG_HOTPLUG_CPU
176/*
177 * Boot CPU0 entry point. It's called from play_dead(). Everything has been set
178 * up already except stack. We just set up stack here. Then call
179 * start_secondary().
180 */
181ENTRY(start_cpu0)
182	movl initial_stack, %ecx
183	movl %ecx, %esp
184	call *(initial_code)
1851:	jmp 1b
186ENDPROC(start_cpu0)
187#endif
188
189/*
190 * Non-boot CPU entry point; entered from trampoline.S
191 * We can't lgdt here, because lgdt itself uses a data segment, but
192 * we know the trampoline has already loaded the boot_gdt for us.
193 *
194 * If cpu hotplug is not supported then this code can go in init section
195 * which will be freed later
196 */
197ENTRY(startup_32_smp)
198	cld
199	movl $(__BOOT_DS),%eax
200	movl %eax,%ds
201	movl %eax,%es
202	movl %eax,%fs
203	movl %eax,%gs
204	movl pa(initial_stack),%ecx
205	movl %eax,%ss
206	leal -__PAGE_OFFSET(%ecx),%esp
207
208#ifdef CONFIG_MICROCODE
209	/* Early load ucode on AP. */
210	call load_ucode_ap
211#endif
212
213.Ldefault_entry:
214#define CR0_STATE	(X86_CR0_PE | X86_CR0_MP | X86_CR0_ET | \
215			 X86_CR0_NE | X86_CR0_WP | X86_CR0_AM | \
216			 X86_CR0_PG)
217	movl $(CR0_STATE & ~X86_CR0_PG),%eax
218	movl %eax,%cr0
219
220/*
221 * We want to start out with EFLAGS unambiguously cleared. Some BIOSes leave
222 * bits like NT set. This would confuse the debugger if this code is traced. So
223 * initialize them properly now before switching to protected mode. That means
224 * DF in particular (even though we have cleared it earlier after copying the
225 * command line) because GCC expects it.
226 */
227	pushl $0
228	popfl
229
230/*
231 * New page tables may be in 4Mbyte page mode and may be using the global pages.
232 *
233 * NOTE! If we are on a 486 we may have no cr4 at all! Specifically, cr4 exists
234 * if and only if CPUID exists and has flags other than the FPU flag set.
235 */
236	movl $-1,pa(X86_CPUID)		# preset CPUID level
237	movl $X86_EFLAGS_ID,%ecx
238	pushl %ecx
239	popfl				# set EFLAGS=ID
240	pushfl
241	popl %eax			# get EFLAGS
242	testl $X86_EFLAGS_ID,%eax	# did EFLAGS.ID remained set?
243	jz .Lenable_paging		# hw disallowed setting of ID bit
244					# which means no CPUID and no CR4
245
246	xorl %eax,%eax
247	cpuid
248	movl %eax,pa(X86_CPUID)		# save largest std CPUID function
249
250	movl $1,%eax
251	cpuid
252	andl $~1,%edx			# Ignore CPUID.FPU
253	jz .Lenable_paging		# No flags or only CPUID.FPU = no CR4
254
255	movl pa(mmu_cr4_features),%eax
256	movl %eax,%cr4
257
258	testb $X86_CR4_PAE, %al		# check if PAE is enabled
259	jz .Lenable_paging
260
261	/* Check if extended functions are implemented */
262	movl $0x80000000, %eax
263	cpuid
264	/* Value must be in the range 0x80000001 to 0x8000ffff */
265	subl $0x80000001, %eax
266	cmpl $(0x8000ffff-0x80000001), %eax
267	ja .Lenable_paging
268
269	/* Clear bogus XD_DISABLE bits */
270	call verify_cpu
271
272	mov $0x80000001, %eax
273	cpuid
274	/* Execute Disable bit supported? */
275	btl $(X86_FEATURE_NX & 31), %edx
276	jnc .Lenable_paging
277
278	/* Setup EFER (Extended Feature Enable Register) */
279	movl $MSR_EFER, %ecx
280	rdmsr
281
282	btsl $_EFER_NX, %eax
283	/* Make changes effective */
284	wrmsr
285
286.Lenable_paging:
287
288/*
289 * Enable paging
290 */
291	movl $pa(initial_page_table), %eax
292	movl %eax,%cr3		/* set the page table pointer.. */
293	movl $CR0_STATE,%eax
294	movl %eax,%cr0		/* ..and set paging (PG) bit */
295	ljmp $__BOOT_CS,$1f	/* Clear prefetch and normalize %eip */
2961:
297	/* Shift the stack pointer to a virtual address */
298	addl $__PAGE_OFFSET, %esp
299
300/*
301 * start system 32-bit setup. We need to re-do some of the things done
302 * in 16-bit mode for the "real" operations.
303 */
304	movl setup_once_ref,%eax
305	andl %eax,%eax
306	jz 1f				# Did we do this already?
307	call *%eax
3081:
309
310/*
311 * Check if it is 486
312 */
313	movb $4,X86			# at least 486
314	cmpl $-1,X86_CPUID
315	je .Lis486
316
317	/* get vendor info */
318	xorl %eax,%eax			# call CPUID with 0 -> return vendor ID
319	cpuid
320	movl %eax,X86_CPUID		# save CPUID level
321	movl %ebx,X86_VENDOR_ID		# lo 4 chars
322	movl %edx,X86_VENDOR_ID+4	# next 4 chars
323	movl %ecx,X86_VENDOR_ID+8	# last 4 chars
324
325	orl %eax,%eax			# do we have processor info as well?
326	je .Lis486
327
328	movl $1,%eax		# Use the CPUID instruction to get CPU type
329	cpuid
330	movb %al,%cl		# save reg for future use
331	andb $0x0f,%ah		# mask processor family
332	movb %ah,X86
333	andb $0xf0,%al		# mask model
334	shrb $4,%al
335	movb %al,X86_MODEL
336	andb $0x0f,%cl		# mask mask revision
337	movb %cl,X86_MASK
338	movl %edx,X86_CAPABILITY
339
340.Lis486:
341	movl $0x50022,%ecx	# set AM, WP, NE and MP
342	movl %cr0,%eax
343	andl $0x80000011,%eax	# Save PG,PE,ET
344	orl %ecx,%eax
345	movl %eax,%cr0
346
347	lgdt early_gdt_descr
348	ljmp $(__KERNEL_CS),$1f
3491:	movl $(__KERNEL_DS),%eax	# reload all the segment registers
350	movl %eax,%ss			# after changing gdt.
351
352	movl $(__USER_DS),%eax		# DS/ES contains default USER segment
353	movl %eax,%ds
354	movl %eax,%es
355
356	movl $(__KERNEL_PERCPU), %eax
357	movl %eax,%fs			# set this cpu's percpu
358
359	movl $(__KERNEL_STACK_CANARY),%eax
360	movl %eax,%gs
361
362	xorl %eax,%eax			# Clear LDT
363	lldt %ax
364
365	call *(initial_code)
3661:	jmp 1b
367ENDPROC(startup_32_smp)
368
369#include "verify_cpu.S"
370
371/*
372 *  setup_once
373 *
374 *  The setup work we only want to run on the BSP.
375 *
376 *  Warning: %esi is live across this function.
377 */
378__INIT
379setup_once:
380#ifdef CONFIG_CC_STACKPROTECTOR
381	/*
382	 * Configure the stack canary. The linker can't handle this by
383	 * relocation.  Manually set base address in stack canary
384	 * segment descriptor.
385	 */
386	movl $gdt_page,%eax
387	movl $stack_canary,%ecx
388	movw %cx, 8 * GDT_ENTRY_STACK_CANARY + 2(%eax)
389	shrl $16, %ecx
390	movb %cl, 8 * GDT_ENTRY_STACK_CANARY + 4(%eax)
391	movb %ch, 8 * GDT_ENTRY_STACK_CANARY + 7(%eax)
392#endif
393
394	andl $0,setup_once_ref	/* Once is enough, thanks */
395	ret
396
397ENTRY(early_idt_handler_array)
398	# 36(%esp) %eflags
399	# 32(%esp) %cs
400	# 28(%esp) %eip
401	# 24(%rsp) error code
402	i = 0
403	.rept NUM_EXCEPTION_VECTORS
404	.ifeq (EXCEPTION_ERRCODE_MASK >> i) & 1
405	pushl $0		# Dummy error code, to make stack frame uniform
406	.endif
407	pushl $i		# 20(%esp) Vector number
408	jmp early_idt_handler_common
409	i = i + 1
410	.fill early_idt_handler_array + i*EARLY_IDT_HANDLER_SIZE - ., 1, 0xcc
411	.endr
412ENDPROC(early_idt_handler_array)
413
414early_idt_handler_common:
415	/*
416	 * The stack is the hardware frame, an error code or zero, and the
417	 * vector number.
418	 */
419	cld
420
421	incl %ss:early_recursion_flag
422
423	/* The vector number is in pt_regs->gs */
424
425	cld
426	pushl	%fs		/* pt_regs->fs (__fsh varies by model) */
427	pushl	%es		/* pt_regs->es (__esh varies by model) */
428	pushl	%ds		/* pt_regs->ds (__dsh varies by model) */
429	pushl	%eax		/* pt_regs->ax */
430	pushl	%ebp		/* pt_regs->bp */
431	pushl	%edi		/* pt_regs->di */
432	pushl	%esi		/* pt_regs->si */
433	pushl	%edx		/* pt_regs->dx */
434	pushl	%ecx		/* pt_regs->cx */
435	pushl	%ebx		/* pt_regs->bx */
436
437	/* Fix up DS and ES */
438	movl	$(__KERNEL_DS), %ecx
439	movl	%ecx, %ds
440	movl	%ecx, %es
441
442	/* Load the vector number into EDX */
443	movl	PT_GS(%esp), %edx
444
445	/* Load GS into pt_regs->gs (and maybe clobber __gsh) */
446	movw	%gs, PT_GS(%esp)
447
448	movl	%esp, %eax	/* args are pt_regs (EAX), trapnr (EDX) */
449	call	early_fixup_exception
450
451	popl	%ebx		/* pt_regs->bx */
452	popl	%ecx		/* pt_regs->cx */
453	popl	%edx		/* pt_regs->dx */
454	popl	%esi		/* pt_regs->si */
455	popl	%edi		/* pt_regs->di */
456	popl	%ebp		/* pt_regs->bp */
457	popl	%eax		/* pt_regs->ax */
458	popl	%ds		/* pt_regs->ds (always ignores __dsh) */
459	popl	%es		/* pt_regs->es (always ignores __esh) */
460	popl	%fs		/* pt_regs->fs (always ignores __fsh) */
461	popl	%gs		/* pt_regs->gs (always ignores __gsh) */
462	decl	%ss:early_recursion_flag
463	addl	$4, %esp	/* pop pt_regs->orig_ax */
464	iret
465ENDPROC(early_idt_handler_common)
466
467/* This is the default interrupt "handler" :-) */
468ENTRY(early_ignore_irq)
469	cld
470#ifdef CONFIG_PRINTK
471	pushl %eax
472	pushl %ecx
473	pushl %edx
474	pushl %es
475	pushl %ds
476	movl $(__KERNEL_DS),%eax
477	movl %eax,%ds
478	movl %eax,%es
479	cmpl $2,early_recursion_flag
480	je hlt_loop
481	incl early_recursion_flag
482	pushl 16(%esp)
483	pushl 24(%esp)
484	pushl 32(%esp)
485	pushl 40(%esp)
486	pushl $int_msg
487	call printk
488
489	call dump_stack
490
491	addl $(5*4),%esp
492	popl %ds
493	popl %es
494	popl %edx
495	popl %ecx
496	popl %eax
497#endif
498	iret
499
500hlt_loop:
501	hlt
502	jmp hlt_loop
503ENDPROC(early_ignore_irq)
504
505__INITDATA
506	.align 4
507GLOBAL(early_recursion_flag)
508	.long 0
509
510__REFDATA
511	.align 4
512ENTRY(initial_code)
513	.long i386_start_kernel
514ENTRY(setup_once_ref)
515	.long setup_once
516
517/*
518 * BSS section
519 */
520__PAGE_ALIGNED_BSS
521	.align PAGE_SIZE
522#ifdef CONFIG_X86_PAE
523.globl initial_pg_pmd
524initial_pg_pmd:
525	.fill 1024*KPMDS,4,0
526#else
527.globl initial_page_table
528initial_page_table:
529	.fill 1024,4,0
530#endif
531initial_pg_fixmap:
532	.fill 1024,4,0
533.globl empty_zero_page
534empty_zero_page:
535	.fill 4096,1,0
536.globl swapper_pg_dir
537swapper_pg_dir:
538	.fill 1024,4,0
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 PAGE_SIZE
548ENTRY(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#endif
567
568.data
569.balign 4
570ENTRY(initial_stack)
571	/*
572	 * The SIZEOF_PTREGS gap is a convention which helps the in-kernel
573	 * unwinder reliably detect the end of the stack.
574	 */
575	.long init_thread_union + THREAD_SIZE - SIZEOF_PTREGS - \
576	      TOP_OF_KERNEL_STACK_PADDING;
577
578__INITRODATA
579int_msg:
580	.asciz "Unknown interrupt or fault at: %p %p %p\n"
581
582#include "../../x86/xen/xen-head.S"
583
584/*
585 * The IDT and GDT 'descriptors' are a strange 48-bit object
586 * only used by the lidt and lgdt instructions. They are not
587 * like usual segment descriptors - they consist of a 16-bit
588 * segment size, and 32-bit linear address value:
589 */
590
591	.data
592.globl boot_gdt_descr
593
594	ALIGN
595# early boot GDT descriptor (must use 1:1 address mapping)
596	.word 0				# 32 bit align gdt_desc.address
597boot_gdt_descr:
598	.word __BOOT_DS+7
599	.long boot_gdt - __PAGE_OFFSET
600
601# boot GDT descriptor (later on used by CPU#0):
602	.word 0				# 32 bit align gdt_desc.address
603ENTRY(early_gdt_descr)
604	.word GDT_ENTRIES*8-1
605	.long gdt_page			/* Overwritten for secondary CPUs */
606
607/*
608 * The boot_gdt must mirror the equivalent in setup.S and is
609 * used only for booting.
610 */
611	.align L1_CACHE_BYTES
612ENTRY(boot_gdt)
613	.fill GDT_ENTRY_BOOT_CS,8,0
614	.quad 0x00cf9a000000ffff	/* kernel 4GB code at 0x00000000 */
615	.quad 0x00cf92000000ffff	/* kernel 4GB data at 0x00000000 */
616