1/*
2 * relocate_kernel.S - put the kernel image in place to boot
3 * Copyright (C) 2002-2004 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
14/*
15 * Must be relocatable PIC code callable as a C function
16 */
17
18#define PTR(x) (x << 2)
19
20/*
21 * control_page + KEXEC_CONTROL_CODE_MAX_SIZE
22 * ~ control_page + PAGE_SIZE are used as data storage and stack for
23 * jumping back
24 */
25#define DATA(offset)		(KEXEC_CONTROL_CODE_MAX_SIZE+(offset))
26
27/* Minimal CPU state */
28#define ESP			DATA(0x0)
29#define CR0			DATA(0x4)
30#define CR3			DATA(0x8)
31#define CR4			DATA(0xc)
32
33/* other data */
34#define CP_VA_CONTROL_PAGE	DATA(0x10)
35#define CP_PA_PGD		DATA(0x14)
36#define CP_PA_SWAP_PAGE		DATA(0x18)
37#define CP_PA_BACKUP_PAGES_MAP	DATA(0x1c)
38
39	.text
40	.globl relocate_kernel
41relocate_kernel:
42	/* Save the CPU context, used for jumping back */
43
44	pushl	%ebx
45	pushl	%esi
46	pushl	%edi
47	pushl	%ebp
48	pushf
49
50	movl	20+8(%esp), %ebp /* list of pages */
51	movl	PTR(VA_CONTROL_PAGE)(%ebp), %edi
52	movl	%esp, ESP(%edi)
53	movl	%cr0, %eax
54	movl	%eax, CR0(%edi)
55	movl	%cr3, %eax
56	movl	%eax, CR3(%edi)
57	movl	%cr4, %eax
58	movl	%eax, CR4(%edi)
59
60	/* read the arguments and say goodbye to the stack */
61	movl  20+4(%esp), %ebx /* page_list */
62	movl  20+8(%esp), %ebp /* list of pages */
63	movl  20+12(%esp), %edx /* start address */
64	movl  20+16(%esp), %ecx /* cpu_has_pae */
65	movl  20+20(%esp), %esi /* preserve_context */
66
67	/* zero out flags, and disable interrupts */
68	pushl $0
69	popfl
70
71	/* save some information for jumping back */
72	movl	PTR(VA_CONTROL_PAGE)(%ebp), %edi
73	movl	%edi, CP_VA_CONTROL_PAGE(%edi)
74	movl	PTR(PA_PGD)(%ebp), %eax
75	movl	%eax, CP_PA_PGD(%edi)
76	movl	PTR(PA_SWAP_PAGE)(%ebp), %eax
77	movl	%eax, CP_PA_SWAP_PAGE(%edi)
78	movl	%ebx, CP_PA_BACKUP_PAGES_MAP(%edi)
79
80	/*
81	 * get physical address of control page now
82	 * this is impossible after page table switch
83	 */
84	movl	PTR(PA_CONTROL_PAGE)(%ebp), %edi
85
86	/* switch to new set of page tables */
87	movl	PTR(PA_PGD)(%ebp), %eax
88	movl	%eax, %cr3
89
90	/* setup a new stack at the end of the physical control page */
91	lea	PAGE_SIZE(%edi), %esp
92
93	/* jump to identity mapped page */
94	movl    %edi, %eax
95	addl    $(identity_mapped - relocate_kernel), %eax
96	pushl   %eax
97	ret
98
99identity_mapped:
100	/* set return address to 0 if not preserving context */
101	pushl	$0
102	/* store the start address on the stack */
103	pushl   %edx
104
105	/*
106	 * Set cr0 to a known state:
107	 *  - Paging disabled
108	 *  - Alignment check disabled
109	 *  - Write protect disabled
110	 *  - No task switch
111	 *  - Don't do FP software emulation.
112	 *  - Proctected mode enabled
113	 */
114	movl	%cr0, %eax
115	andl	$~(X86_CR0_PG | X86_CR0_AM | X86_CR0_WP | X86_CR0_TS | X86_CR0_EM), %eax
116	orl	$(X86_CR0_PE), %eax
117	movl	%eax, %cr0
118
119	/* clear cr4 if applicable */
120	testl	%ecx, %ecx
121	jz	1f
122	/*
123	 * Set cr4 to a known state:
124	 * Setting everything to zero seems safe.
125	 */
126	xorl	%eax, %eax
127	movl	%eax, %cr4
128
129	jmp 1f
1301:
131
132	/* Flush the TLB (needed?) */
133	xorl	%eax, %eax
134	movl	%eax, %cr3
135
136	movl	CP_PA_SWAP_PAGE(%edi), %eax
137	pushl	%eax
138	pushl	%ebx
139	call	swap_pages
140	addl	$8, %esp
141
142	/*
143	 * To be certain of avoiding problems with self-modifying code
144	 * I need to execute a serializing instruction here.
145	 * So I flush the TLB, it's handy, and not processor dependent.
146	 */
147	xorl	%eax, %eax
148	movl	%eax, %cr3
149
150	/*
151	 * set all of the registers to known values
152	 * leave %esp alone
153	 */
154
155	testl	%esi, %esi
156	jnz 1f
157	xorl	%edi, %edi
158	xorl	%eax, %eax
159	xorl	%ebx, %ebx
160	xorl    %ecx, %ecx
161	xorl    %edx, %edx
162	xorl    %esi, %esi
163	xorl    %ebp, %ebp
164	ret
1651:
166	popl	%edx
167	movl	CP_PA_SWAP_PAGE(%edi), %esp
168	addl	$PAGE_SIZE, %esp
1692:
170	call	*%edx
171
172	/* get the re-entry point of the peer system */
173	movl	0(%esp), %ebp
174	call	1f
1751:
176	popl	%ebx
177	subl	$(1b - relocate_kernel), %ebx
178	movl	CP_VA_CONTROL_PAGE(%ebx), %edi
179	lea	PAGE_SIZE(%ebx), %esp
180	movl	CP_PA_SWAP_PAGE(%ebx), %eax
181	movl	CP_PA_BACKUP_PAGES_MAP(%ebx), %edx
182	pushl	%eax
183	pushl	%edx
184	call	swap_pages
185	addl	$8, %esp
186	movl	CP_PA_PGD(%ebx), %eax
187	movl	%eax, %cr3
188	movl	%cr0, %eax
189	orl	$X86_CR0_PG, %eax
190	movl	%eax, %cr0
191	lea	PAGE_SIZE(%edi), %esp
192	movl	%edi, %eax
193	addl	$(virtual_mapped - relocate_kernel), %eax
194	pushl	%eax
195	ret
196
197virtual_mapped:
198	movl	CR4(%edi), %eax
199	movl	%eax, %cr4
200	movl	CR3(%edi), %eax
201	movl	%eax, %cr3
202	movl	CR0(%edi), %eax
203	movl	%eax, %cr0
204	movl	ESP(%edi), %esp
205	movl	%ebp, %eax
206
207	popf
208	popl	%ebp
209	popl	%edi
210	popl	%esi
211	popl	%ebx
212	ret
213
214	/* Do the copies */
215swap_pages:
216	movl	8(%esp), %edx
217	movl	4(%esp), %ecx
218	pushl	%ebp
219	pushl	%ebx
220	pushl	%edi
221	pushl	%esi
222	movl	%ecx, %ebx
223	jmp	1f
224
2250:	/* top, read another word from the indirection page */
226	movl	(%ebx), %ecx
227	addl	$4, %ebx
2281:
229	testl	$0x1,   %ecx  /* is it a destination page */
230	jz	2f
231	movl	%ecx,	%edi
232	andl	$0xfffff000, %edi
233	jmp     0b
2342:
235	testl	$0x2,	%ecx  /* is it an indirection page */
236	jz	2f
237	movl	%ecx,	%ebx
238	andl	$0xfffff000, %ebx
239	jmp     0b
2402:
241	testl   $0x4,   %ecx /* is it the done indicator */
242	jz      2f
243	jmp     3f
2442:
245	testl   $0x8,   %ecx /* is it the source indicator */
246	jz      0b	     /* Ignore it otherwise */
247	movl    %ecx,   %esi /* For every source page do a copy */
248	andl    $0xfffff000, %esi
249
250	movl	%edi, %eax
251	movl	%esi, %ebp
252
253	movl	%edx, %edi
254	movl    $1024, %ecx
255	rep ; movsl
256
257	movl	%ebp, %edi
258	movl	%eax, %esi
259	movl	$1024, %ecx
260	rep ; movsl
261
262	movl	%eax, %edi
263	movl	%edx, %esi
264	movl	$1024, %ecx
265	rep ; movsl
266
267	lea	PAGE_SIZE(%ebp), %esi
268	jmp     0b
2693:
270	popl	%esi
271	popl	%edi
272	popl	%ebx
273	popl	%ebp
274	ret
275
276	.globl kexec_control_code_size
277.set kexec_control_code_size, . - relocate_kernel
278