1/*
2 * relocate_kernel.S - put the kernel image in place to boot
3 * Copyright (C) 2002-2005 Eric Biederman  <ebiederm@xmission.com>
4 *
5 * This source code is licensed under the GNU General Public License,
6 * Version 2.  See the file COPYING for more details.
7 */
8
9#include <linux/linkage.h>
10#include <asm/page_types.h>
11#include <asm/kexec.h>
12#include <asm/processor-flags.h>
13#include <asm/pgtable_types.h>
14
15/*
16 * Must be relocatable PIC code callable as a C function
17 */
18
19#define PTR(x) (x << 3)
20#define PAGE_ATTR (_PAGE_PRESENT | _PAGE_RW | _PAGE_ACCESSED | _PAGE_DIRTY)
21
22/*
23 * control_page + KEXEC_CONTROL_CODE_MAX_SIZE
24 * ~ control_page + PAGE_SIZE are used as data storage and stack for
25 * jumping back
26 */
27#define DATA(offset)		(KEXEC_CONTROL_CODE_MAX_SIZE+(offset))
28
29/* Minimal CPU state */
30#define RSP			DATA(0x0)
31#define CR0			DATA(0x8)
32#define CR3			DATA(0x10)
33#define CR4			DATA(0x18)
34
35/* other data */
36#define CP_PA_TABLE_PAGE	DATA(0x20)
37#define CP_PA_SWAP_PAGE		DATA(0x28)
38#define CP_PA_BACKUP_PAGES_MAP	DATA(0x30)
39
40	.text
41	.align PAGE_SIZE
42	.code64
43	.globl relocate_kernel
44relocate_kernel:
45	/*
46	 * %rdi indirection_page
47	 * %rsi page_list
48	 * %rdx start address
49	 * %rcx preserve_context
50	 */
51
52	/* Save the CPU context, used for jumping back */
53	pushq %rbx
54	pushq %rbp
55	pushq %r12
56	pushq %r13
57	pushq %r14
58	pushq %r15
59	pushf
60
61	movq	PTR(VA_CONTROL_PAGE)(%rsi), %r11
62	movq	%rsp, RSP(%r11)
63	movq	%cr0, %rax
64	movq	%rax, CR0(%r11)
65	movq	%cr3, %rax
66	movq	%rax, CR3(%r11)
67	movq	%cr4, %rax
68	movq	%rax, CR4(%r11)
69
70	/* zero out flags, and disable interrupts */
71	pushq $0
72	popfq
73
74	/*
75	 * get physical address of control page now
76	 * this is impossible after page table switch
77	 */
78	movq	PTR(PA_CONTROL_PAGE)(%rsi), %r8
79
80	/* get physical address of page table now too */
81	movq	PTR(PA_TABLE_PAGE)(%rsi), %r9
82
83	/* get physical address of swap page now */
84	movq	PTR(PA_SWAP_PAGE)(%rsi), %r10
85
86	/* save some information for jumping back */
87	movq	%r9, CP_PA_TABLE_PAGE(%r11)
88	movq	%r10, CP_PA_SWAP_PAGE(%r11)
89	movq	%rdi, CP_PA_BACKUP_PAGES_MAP(%r11)
90
91	/* Switch to the identity mapped page tables */
92	movq	%r9, %cr3
93
94	/* setup a new stack at the end of the physical control page */
95	lea	PAGE_SIZE(%r8), %rsp
96
97	/* jump to identity mapped page */
98	addq	$(identity_mapped - relocate_kernel), %r8
99	pushq	%r8
100	ret
101
102identity_mapped:
103	/* set return address to 0 if not preserving context */
104	pushq	$0
105	/* store the start address on the stack */
106	pushq   %rdx
107
108	/*
109	 * Set cr0 to a known state:
110	 *  - Paging enabled
111	 *  - Alignment check disabled
112	 *  - Write protect disabled
113	 *  - No task switch
114	 *  - Don't do FP software emulation.
115	 *  - Proctected mode enabled
116	 */
117	movq	%cr0, %rax
118	andq	$~(X86_CR0_AM | X86_CR0_WP | X86_CR0_TS | X86_CR0_EM), %rax
119	orl	$(X86_CR0_PG | X86_CR0_PE), %eax
120	movq	%rax, %cr0
121
122	/*
123	 * Set cr4 to a known state:
124	 *  - physical address extension enabled
125	 */
126	movq	$X86_CR4_PAE, %rax
127	movq	%rax, %cr4
128
129	jmp 1f
1301:
131
132	/* Flush the TLB (needed?) */
133	movq	%r9, %cr3
134
135	movq	%rcx, %r11
136	call	swap_pages
137
138	/*
139	 * To be certain of avoiding problems with self-modifying code
140	 * I need to execute a serializing instruction here.
141	 * So I flush the TLB by reloading %cr3 here, it's handy,
142	 * and not processor dependent.
143	 */
144	movq	%cr3, %rax
145	movq	%rax, %cr3
146
147	/*
148	 * set all of the registers to known values
149	 * leave %rsp alone
150	 */
151
152	testq	%r11, %r11
153	jnz 1f
154	xorq	%rax, %rax
155	xorq	%rbx, %rbx
156	xorq    %rcx, %rcx
157	xorq    %rdx, %rdx
158	xorq    %rsi, %rsi
159	xorq    %rdi, %rdi
160	xorq    %rbp, %rbp
161	xorq	%r8,  %r8
162	xorq	%r9,  %r9
163	xorq	%r10, %r9
164	xorq	%r11, %r11
165	xorq	%r12, %r12
166	xorq	%r13, %r13
167	xorq	%r14, %r14
168	xorq	%r15, %r15
169
170	ret
171
1721:
173	popq	%rdx
174	leaq	PAGE_SIZE(%r10), %rsp
175	call	*%rdx
176
177	/* get the re-entry point of the peer system */
178	movq	0(%rsp), %rbp
179	call	1f
1801:
181	popq	%r8
182	subq	$(1b - relocate_kernel), %r8
183	movq	CP_PA_SWAP_PAGE(%r8), %r10
184	movq	CP_PA_BACKUP_PAGES_MAP(%r8), %rdi
185	movq	CP_PA_TABLE_PAGE(%r8), %rax
186	movq	%rax, %cr3
187	lea	PAGE_SIZE(%r8), %rsp
188	call	swap_pages
189	movq	$virtual_mapped, %rax
190	pushq	%rax
191	ret
192
193virtual_mapped:
194	movq	RSP(%r8), %rsp
195	movq	CR4(%r8), %rax
196	movq	%rax, %cr4
197	movq	CR3(%r8), %rax
198	movq	CR0(%r8), %r8
199	movq	%rax, %cr3
200	movq	%r8, %cr0
201	movq	%rbp, %rax
202
203	popf
204	popq	%r15
205	popq	%r14
206	popq	%r13
207	popq	%r12
208	popq	%rbp
209	popq	%rbx
210	ret
211
212	/* Do the copies */
213swap_pages:
214	movq	%rdi, %rcx 	/* Put the page_list in %rcx */
215	xorq	%rdi, %rdi
216	xorq	%rsi, %rsi
217	jmp	1f
218
2190:	/* top, read another word for the indirection page */
220
221	movq	(%rbx), %rcx
222	addq	$8,	%rbx
2231:
224	testq	$0x1,	%rcx  /* is it a destination page? */
225	jz	2f
226	movq	%rcx,	%rdi
227	andq	$0xfffffffffffff000, %rdi
228	jmp	0b
2292:
230	testq	$0x2,	%rcx  /* is it an indirection page? */
231	jz	2f
232	movq	%rcx,   %rbx
233	andq	$0xfffffffffffff000, %rbx
234	jmp	0b
2352:
236	testq	$0x4,	%rcx  /* is it the done indicator? */
237	jz	2f
238	jmp	3f
2392:
240	testq	$0x8,	%rcx  /* is it the source indicator? */
241	jz	0b	      /* Ignore it otherwise */
242	movq	%rcx,   %rsi  /* For ever source page do a copy */
243	andq	$0xfffffffffffff000, %rsi
244
245	movq	%rdi, %rdx
246	movq	%rsi, %rax
247
248	movq	%r10, %rdi
249	movq	$512,   %rcx
250	rep ; movsq
251
252	movq	%rax, %rdi
253	movq	%rdx, %rsi
254	movq	$512,   %rcx
255	rep ; movsq
256
257	movq	%rdx, %rdi
258	movq	%r10, %rsi
259	movq	$512,   %rcx
260	rep ; movsq
261
262	lea	PAGE_SIZE(%rax), %rsi
263	jmp	0b
2643:
265	ret
266
267	.globl kexec_control_code_size
268.set kexec_control_code_size, . - relocate_kernel
269