xref: /openbmc/linux/arch/x86/kernel/head_64.S (revision 84f4fc52) 
1/*
2 *  linux/arch/x86_64/kernel/head.S -- start in 32bit and switch to 64bit
3 *
4 *  Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE
5 *  Copyright (C) 2000 Pavel Machek <pavel@suse.cz>
6 *  Copyright (C) 2000 Karsten Keil <kkeil@suse.de>
7 *  Copyright (C) 2001,2002 Andi Kleen <ak@suse.de>
8 *  Copyright (C) 2005 Eric Biederman <ebiederm@xmission.com>
9 */
10
11
12#include <linux/linkage.h>
13#include <linux/threads.h>
14#include <linux/init.h>
15#include <asm/segment.h>
16#include <asm/pgtable.h>
17#include <asm/page.h>
18#include <asm/msr.h>
19#include <asm/cache.h>
20#include <asm/processor-flags.h>
21#include <asm/percpu.h>
22
23#ifdef CONFIG_PARAVIRT
24#include <asm/asm-offsets.h>
25#include <asm/paravirt.h>
26#else
27#define GET_CR2_INTO_RCX movq %cr2, %rcx
28#endif
29
30/* we are not able to switch in one step to the final KERNEL ADDRESS SPACE
31 * because we need identity-mapped pages.
32 *
33 */
34
35#define pud_index(x)	(((x) >> PUD_SHIFT) & (PTRS_PER_PUD-1))
36
37L4_PAGE_OFFSET = pgd_index(__PAGE_OFFSET)
38L3_PAGE_OFFSET = pud_index(__PAGE_OFFSET)
39L4_START_KERNEL = pgd_index(__START_KERNEL_map)
40L3_START_KERNEL = pud_index(__START_KERNEL_map)
41
42	.text
43	__HEAD
44	.code64
45	.globl startup_64
46startup_64:
47
48	/*
49	 * At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 1,
50	 * and someone has loaded an identity mapped page table
51	 * for us.  These identity mapped page tables map all of the
52	 * kernel pages and possibly all of memory.
53	 *
54	 * %esi holds a physical pointer to real_mode_data.
55	 *
56	 * We come here either directly from a 64bit bootloader, or from
57	 * arch/x86_64/boot/compressed/head.S.
58	 *
59	 * We only come here initially at boot nothing else comes here.
60	 *
61	 * Since we may be loaded at an address different from what we were
62	 * compiled to run at we first fixup the physical addresses in our page
63	 * tables and then reload them.
64	 */
65
66	/* Compute the delta between the address I am compiled to run at and the
67	 * address I am actually running at.
68	 */
69	leaq	_text(%rip), %rbp
70	subq	$_text - __START_KERNEL_map, %rbp
71
72	/* Is the address not 2M aligned? */
73	movq	%rbp, %rax
74	andl	$~PMD_PAGE_MASK, %eax
75	testl	%eax, %eax
76	jnz	bad_address
77
78	/* Is the address too large? */
79	leaq	_text(%rip), %rdx
80	movq	$PGDIR_SIZE, %rax
81	cmpq	%rax, %rdx
82	jae	bad_address
83
84	/* Fixup the physical addresses in the page table
85	 */
86	addq	%rbp, init_level4_pgt + 0(%rip)
87	addq	%rbp, init_level4_pgt + (L4_PAGE_OFFSET*8)(%rip)
88	addq	%rbp, init_level4_pgt + (L4_START_KERNEL*8)(%rip)
89
90	addq	%rbp, level3_ident_pgt + 0(%rip)
91
92	addq	%rbp, level3_kernel_pgt + (510*8)(%rip)
93	addq	%rbp, level3_kernel_pgt + (511*8)(%rip)
94
95	addq	%rbp, level2_fixmap_pgt + (506*8)(%rip)
96
97	/* Add an Identity mapping if I am above 1G */
98	leaq	_text(%rip), %rdi
99	andq	$PMD_PAGE_MASK, %rdi
100
101	movq	%rdi, %rax
102	shrq	$PUD_SHIFT, %rax
103	andq	$(PTRS_PER_PUD - 1), %rax
104	jz	ident_complete
105
106	leaq	(level2_spare_pgt - __START_KERNEL_map + _KERNPG_TABLE)(%rbp), %rdx
107	leaq	level3_ident_pgt(%rip), %rbx
108	movq	%rdx, 0(%rbx, %rax, 8)
109
110	movq	%rdi, %rax
111	shrq	$PMD_SHIFT, %rax
112	andq	$(PTRS_PER_PMD - 1), %rax
113	leaq	__PAGE_KERNEL_IDENT_LARGE_EXEC(%rdi), %rdx
114	leaq	level2_spare_pgt(%rip), %rbx
115	movq	%rdx, 0(%rbx, %rax, 8)
116ident_complete:
117
118	/*
119	 * Fixup the kernel text+data virtual addresses. Note that
120	 * we might write invalid pmds, when the kernel is relocated
121	 * cleanup_highmap() fixes this up along with the mappings
122	 * beyond _end.
123	 */
124
125	leaq	level2_kernel_pgt(%rip), %rdi
126	leaq	4096(%rdi), %r8
127	/* See if it is a valid page table entry */
1281:	testq	$1, 0(%rdi)
129	jz	2f
130	addq	%rbp, 0(%rdi)
131	/* Go to the next page */
1322:	addq	$8, %rdi
133	cmp	%r8, %rdi
134	jne	1b
135
136	/* Fixup phys_base */
137	addq	%rbp, phys_base(%rip)
138
139	/* Fixup trampoline */
140	addq	%rbp, trampoline_level4_pgt + 0(%rip)
141	addq	%rbp, trampoline_level4_pgt + (511*8)(%rip)
142
143	/* Due to ENTRY(), sometimes the empty space gets filled with
144	 * zeros. Better take a jmp than relying on empty space being
145	 * filled with 0x90 (nop)
146	 */
147	jmp secondary_startup_64
148ENTRY(secondary_startup_64)
149	/*
150	 * At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 1,
151	 * and someone has loaded a mapped page table.
152	 *
153	 * %esi holds a physical pointer to real_mode_data.
154	 *
155	 * We come here either from startup_64 (using physical addresses)
156	 * or from trampoline.S (using virtual addresses).
157	 *
158	 * Using virtual addresses from trampoline.S removes the need
159	 * to have any identity mapped pages in the kernel page table
160	 * after the boot processor executes this code.
161	 */
162
163	/* Enable PAE mode and PGE */
164	movl	$(X86_CR4_PAE | X86_CR4_PGE), %eax
165	movq	%rax, %cr4
166
167	/* Setup early boot stage 4 level pagetables. */
168	movq	$(init_level4_pgt - __START_KERNEL_map), %rax
169	addq	phys_base(%rip), %rax
170	movq	%rax, %cr3
171
172	/* Ensure I am executing from virtual addresses */
173	movq	$1f, %rax
174	jmp	*%rax
1751:
176
177	/* Check if nx is implemented */
178	movl	$0x80000001, %eax
179	cpuid
180	movl	%edx,%edi
181
182	/* Setup EFER (Extended Feature Enable Register) */
183	movl	$MSR_EFER, %ecx
184	rdmsr
185	btsl	$_EFER_SCE, %eax	/* Enable System Call */
186	btl	$20,%edi		/* No Execute supported? */
187	jnc     1f
188	btsl	$_EFER_NX, %eax
1891:	wrmsr				/* Make changes effective */
190
191	/* Setup cr0 */
192#define CR0_STATE	(X86_CR0_PE | X86_CR0_MP | X86_CR0_ET | \
193			 X86_CR0_NE | X86_CR0_WP | X86_CR0_AM | \
194			 X86_CR0_PG)
195	movl	$CR0_STATE, %eax
196	/* Make changes effective */
197	movq	%rax, %cr0
198
199	/* Setup a boot time stack */
200	movq stack_start(%rip),%rsp
201
202	/* zero EFLAGS after setting rsp */
203	pushq $0
204	popfq
205
206	/*
207	 * We must switch to a new descriptor in kernel space for the GDT
208	 * because soon the kernel won't have access anymore to the userspace
209	 * addresses where we're currently running on. We have to do that here
210	 * because in 32bit we couldn't load a 64bit linear address.
211	 */
212	lgdt	early_gdt_descr(%rip)
213
214	/* set up data segments */
215	xorl %eax,%eax
216	movl %eax,%ds
217	movl %eax,%ss
218	movl %eax,%es
219
220	/*
221	 * We don't really need to load %fs or %gs, but load them anyway
222	 * to kill any stale realmode selectors.  This allows execution
223	 * under VT hardware.
224	 */
225	movl %eax,%fs
226	movl %eax,%gs
227
228	/* Set up %gs.
229	 *
230	 * The base of %gs always points to the bottom of the irqstack
231	 * union.  If the stack protector canary is enabled, it is
232	 * located at %gs:40.  Note that, on SMP, the boot cpu uses
233	 * init data section till per cpu areas are set up.
234	 */
235	movl	$MSR_GS_BASE,%ecx
236	movl	initial_gs(%rip),%eax
237	movl	initial_gs+4(%rip),%edx
238	wrmsr
239
240	/* esi is pointer to real mode structure with interesting info.
241	   pass it to C */
242	movl	%esi, %edi
243
244	/* Finally jump to run C code and to be on real kernel address
245	 * Since we are running on identity-mapped space we have to jump
246	 * to the full 64bit address, this is only possible as indirect
247	 * jump.  In addition we need to ensure %cs is set so we make this
248	 * a far return.
249	 */
250	movq	initial_code(%rip),%rax
251	pushq	$0		# fake return address to stop unwinder
252	pushq	$__KERNEL_CS	# set correct cs
253	pushq	%rax		# target address in negative space
254	lretq
255
256	/* SMP bootup changes these two */
257	__REFDATA
258	.align	8
259	ENTRY(initial_code)
260	.quad	x86_64_start_kernel
261	ENTRY(initial_gs)
262	.quad	INIT_PER_CPU_VAR(irq_stack_union)
263
264	ENTRY(stack_start)
265	.quad  init_thread_union+THREAD_SIZE-8
266	.word  0
267	__FINITDATA
268
269bad_address:
270	jmp bad_address
271
272	.section ".init.text","ax"
273#ifdef CONFIG_EARLY_PRINTK
274	.globl early_idt_handlers
275early_idt_handlers:
276	i = 0
277	.rept NUM_EXCEPTION_VECTORS
278	movl $i, %esi
279	jmp early_idt_handler
280	i = i + 1
281	.endr
282#endif
283
284ENTRY(early_idt_handler)
285#ifdef CONFIG_EARLY_PRINTK
286	cmpl $2,early_recursion_flag(%rip)
287	jz  1f
288	incl early_recursion_flag(%rip)
289	GET_CR2_INTO_RCX
290	movq %rcx,%r9
291	xorl %r8d,%r8d		# zero for error code
292	movl %esi,%ecx		# get vector number
293	# Test %ecx against mask of vectors that push error code.
294	cmpl $31,%ecx
295	ja 0f
296	movl $1,%eax
297	salq %cl,%rax
298	testl $EXCEPTION_ERRCODE_MASK,%eax
299	je 0f
300	popq %r8		# get error code
3010:	movq 0(%rsp),%rcx	# get ip
302	movq 8(%rsp),%rdx	# get cs
303	xorl %eax,%eax
304	leaq early_idt_msg(%rip),%rdi
305	call early_printk
306	cmpl $2,early_recursion_flag(%rip)
307	jz  1f
308	call dump_stack
309#ifdef CONFIG_KALLSYMS
310	leaq early_idt_ripmsg(%rip),%rdi
311	movq 0(%rsp),%rsi	# get rip again
312	call __print_symbol
313#endif
314#endif /* EARLY_PRINTK */
3151:	hlt
316	jmp 1b
317
318#ifdef CONFIG_EARLY_PRINTK
319early_recursion_flag:
320	.long 0
321
322early_idt_msg:
323	.asciz "PANIC: early exception %02lx rip %lx:%lx error %lx cr2 %lx\n"
324early_idt_ripmsg:
325	.asciz "RIP %s\n"
326#endif /* CONFIG_EARLY_PRINTK */
327	.previous
328
329#define NEXT_PAGE(name) \
330	.balign	PAGE_SIZE; \
331ENTRY(name)
332
333/* Automate the creation of 1 to 1 mapping pmd entries */
334#define PMDS(START, PERM, COUNT)			\
335	i = 0 ;						\
336	.rept (COUNT) ;					\
337	.quad	(START) + (i << PMD_SHIFT) + (PERM) ;	\
338	i = i + 1 ;					\
339	.endr
340
341	.data
342	/*
343	 * This default setting generates an ident mapping at address 0x100000
344	 * and a mapping for the kernel that precisely maps virtual address
345	 * 0xffffffff80000000 to physical address 0x000000. (always using
346	 * 2Mbyte large pages provided by PAE mode)
347	 */
348NEXT_PAGE(init_level4_pgt)
349	.quad	level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE
350	.org	init_level4_pgt + L4_PAGE_OFFSET*8, 0
351	.quad	level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE
352	.org	init_level4_pgt + L4_START_KERNEL*8, 0
353	/* (2^48-(2*1024*1024*1024))/(2^39) = 511 */
354	.quad	level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE
355
356NEXT_PAGE(level3_ident_pgt)
357	.quad	level2_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE
358	.fill	511,8,0
359
360NEXT_PAGE(level3_kernel_pgt)
361	.fill	L3_START_KERNEL,8,0
362	/* (2^48-(2*1024*1024*1024)-((2^39)*511))/(2^30) = 510 */
363	.quad	level2_kernel_pgt - __START_KERNEL_map + _KERNPG_TABLE
364	.quad	level2_fixmap_pgt - __START_KERNEL_map + _PAGE_TABLE
365
366NEXT_PAGE(level2_fixmap_pgt)
367	.fill	506,8,0
368	.quad	level1_fixmap_pgt - __START_KERNEL_map + _PAGE_TABLE
369	/* 8MB reserved for vsyscalls + a 2MB hole = 4 + 1 entries */
370	.fill	5,8,0
371
372NEXT_PAGE(level1_fixmap_pgt)
373	.fill	512,8,0
374
375NEXT_PAGE(level2_ident_pgt)
376	/* Since I easily can, map the first 1G.
377	 * Don't set NX because code runs from these pages.
378	 */
379	PMDS(0, __PAGE_KERNEL_IDENT_LARGE_EXEC, PTRS_PER_PMD)
380
381NEXT_PAGE(level2_kernel_pgt)
382	/*
383	 * 512 MB kernel mapping. We spend a full page on this pagetable
384	 * anyway.
385	 *
386	 * The kernel code+data+bss must not be bigger than that.
387	 *
388	 * (NOTE: at +512MB starts the module area, see MODULES_VADDR.
389	 *  If you want to increase this then increase MODULES_VADDR
390	 *  too.)
391	 */
392	PMDS(0, __PAGE_KERNEL_LARGE_EXEC,
393		KERNEL_IMAGE_SIZE/PMD_SIZE)
394
395NEXT_PAGE(level2_spare_pgt)
396	.fill   512, 8, 0
397
398#undef PMDS
399#undef NEXT_PAGE
400
401	.data
402	.align 16
403	.globl early_gdt_descr
404early_gdt_descr:
405	.word	GDT_ENTRIES*8-1
406early_gdt_descr_base:
407	.quad	INIT_PER_CPU_VAR(gdt_page)
408
409ENTRY(phys_base)
410	/* This must match the first entry in level2_kernel_pgt */
411	.quad   0x0000000000000000
412
413#include "../../x86/xen/xen-head.S"
414
415	.section .bss, "aw", @nobits
416	.align L1_CACHE_BYTES
417ENTRY(idt_table)
418	.skip IDT_ENTRIES * 16
419
420	.align L1_CACHE_BYTES
421ENTRY(nmi_idt_table)
422	.skip IDT_ENTRIES * 16
423
424	__PAGE_ALIGNED_BSS
425	.align PAGE_SIZE
426ENTRY(empty_zero_page)
427	.skip PAGE_SIZE
428