1/* SPDX-License-Identifier: GPL-2.0-only */
2/*
3 * relocate_kernel.S - put the kernel image in place to boot
4 * Copyright (C) 2002-2004 Eric Biederman  <ebiederm@xmission.com>
5 */
6
7#include <linux/linkage.h>
8#include <asm/page_types.h>
9#include <asm/kexec.h>
10#include <asm/processor-flags.h>
11
12/*
13 * Must be relocatable PIC code callable as a C function
14 */
15
16#define PTR(x) (x << 2)
17
18/*
19 * control_page + KEXEC_CONTROL_CODE_MAX_SIZE
20 * ~ control_page + PAGE_SIZE are used as data storage and stack for
21 * jumping back
22 */
23#define DATA(offset)		(KEXEC_CONTROL_CODE_MAX_SIZE+(offset))
24
25/* Minimal CPU state */
26#define ESP			DATA(0x0)
27#define CR0			DATA(0x4)
28#define CR3			DATA(0x8)
29#define CR4			DATA(0xc)
30
31/* other data */
32#define CP_VA_CONTROL_PAGE	DATA(0x10)
33#define CP_PA_PGD		DATA(0x14)
34#define CP_PA_SWAP_PAGE		DATA(0x18)
35#define CP_PA_BACKUP_PAGES_MAP	DATA(0x1c)
36
37	.text
38	.globl relocate_kernel
39relocate_kernel:
40	/* Save the CPU context, used for jumping back */
41
42	pushl	%ebx
43	pushl	%esi
44	pushl	%edi
45	pushl	%ebp
46	pushf
47
48	movl	20+8(%esp), %ebp /* list of pages */
49	movl	PTR(VA_CONTROL_PAGE)(%ebp), %edi
50	movl	%esp, ESP(%edi)
51	movl	%cr0, %eax
52	movl	%eax, CR0(%edi)
53	movl	%cr3, %eax
54	movl	%eax, CR3(%edi)
55	movl	%cr4, %eax
56	movl	%eax, CR4(%edi)
57
58	/* read the arguments and say goodbye to the stack */
59	movl  20+4(%esp), %ebx /* page_list */
60	movl  20+8(%esp), %ebp /* list of pages */
61	movl  20+12(%esp), %edx /* start address */
62	movl  20+16(%esp), %ecx /* cpu_has_pae */
63	movl  20+20(%esp), %esi /* preserve_context */
64
65	/* zero out flags, and disable interrupts */
66	pushl $0
67	popfl
68
69	/* save some information for jumping back */
70	movl	PTR(VA_CONTROL_PAGE)(%ebp), %edi
71	movl	%edi, CP_VA_CONTROL_PAGE(%edi)
72	movl	PTR(PA_PGD)(%ebp), %eax
73	movl	%eax, CP_PA_PGD(%edi)
74	movl	PTR(PA_SWAP_PAGE)(%ebp), %eax
75	movl	%eax, CP_PA_SWAP_PAGE(%edi)
76	movl	%ebx, CP_PA_BACKUP_PAGES_MAP(%edi)
77
78	/*
79	 * get physical address of control page now
80	 * this is impossible after page table switch
81	 */
82	movl	PTR(PA_CONTROL_PAGE)(%ebp), %edi
83
84	/* switch to new set of page tables */
85	movl	PTR(PA_PGD)(%ebp), %eax
86	movl	%eax, %cr3
87
88	/* setup a new stack at the end of the physical control page */
89	lea	PAGE_SIZE(%edi), %esp
90
91	/* jump to identity mapped page */
92	movl    %edi, %eax
93	addl    $(identity_mapped - relocate_kernel), %eax
94	pushl   %eax
95	ret
96
97identity_mapped:
98	/* set return address to 0 if not preserving context */
99	pushl	$0
100	/* store the start address on the stack */
101	pushl   %edx
102
103	/*
104	 * Set cr0 to a known state:
105	 *  - Paging disabled
106	 *  - Alignment check disabled
107	 *  - Write protect disabled
108	 *  - No task switch
109	 *  - Don't do FP software emulation.
110	 *  - Proctected mode enabled
111	 */
112	movl	%cr0, %eax
113	andl	$~(X86_CR0_PG | X86_CR0_AM | X86_CR0_WP | X86_CR0_TS | X86_CR0_EM), %eax
114	orl	$(X86_CR0_PE), %eax
115	movl	%eax, %cr0
116
117	/* clear cr4 if applicable */
118	testl	%ecx, %ecx
119	jz	1f
120	/*
121	 * Set cr4 to a known state:
122	 * Setting everything to zero seems safe.
123	 */
124	xorl	%eax, %eax
125	movl	%eax, %cr4
126
127	jmp 1f
1281:
129
130	/* Flush the TLB (needed?) */
131	xorl	%eax, %eax
132	movl	%eax, %cr3
133
134	movl	CP_PA_SWAP_PAGE(%edi), %eax
135	pushl	%eax
136	pushl	%ebx
137	call	swap_pages
138	addl	$8, %esp
139
140	/*
141	 * To be certain of avoiding problems with self-modifying code
142	 * I need to execute a serializing instruction here.
143	 * So I flush the TLB, it's handy, and not processor dependent.
144	 */
145	xorl	%eax, %eax
146	movl	%eax, %cr3
147
148	/*
149	 * set all of the registers to known values
150	 * leave %esp alone
151	 */
152
153	testl	%esi, %esi
154	jnz 1f
155	xorl	%edi, %edi
156	xorl	%eax, %eax
157	xorl	%ebx, %ebx
158	xorl    %ecx, %ecx
159	xorl    %edx, %edx
160	xorl    %esi, %esi
161	xorl    %ebp, %ebp
162	ret
1631:
164	popl	%edx
165	movl	CP_PA_SWAP_PAGE(%edi), %esp
166	addl	$PAGE_SIZE, %esp
1672:
168	call	*%edx
169
170	/* get the re-entry point of the peer system */
171	movl	0(%esp), %ebp
172	call	1f
1731:
174	popl	%ebx
175	subl	$(1b - relocate_kernel), %ebx
176	movl	CP_VA_CONTROL_PAGE(%ebx), %edi
177	lea	PAGE_SIZE(%ebx), %esp
178	movl	CP_PA_SWAP_PAGE(%ebx), %eax
179	movl	CP_PA_BACKUP_PAGES_MAP(%ebx), %edx
180	pushl	%eax
181	pushl	%edx
182	call	swap_pages
183	addl	$8, %esp
184	movl	CP_PA_PGD(%ebx), %eax
185	movl	%eax, %cr3
186	movl	%cr0, %eax
187	orl	$X86_CR0_PG, %eax
188	movl	%eax, %cr0
189	lea	PAGE_SIZE(%edi), %esp
190	movl	%edi, %eax
191	addl	$(virtual_mapped - relocate_kernel), %eax
192	pushl	%eax
193	ret
194
195virtual_mapped:
196	movl	CR4(%edi), %eax
197	movl	%eax, %cr4
198	movl	CR3(%edi), %eax
199	movl	%eax, %cr3
200	movl	CR0(%edi), %eax
201	movl	%eax, %cr0
202	movl	ESP(%edi), %esp
203	movl	%ebp, %eax
204
205	popf
206	popl	%ebp
207	popl	%edi
208	popl	%esi
209	popl	%ebx
210	ret
211
212	/* Do the copies */
213swap_pages:
214	movl	8(%esp), %edx
215	movl	4(%esp), %ecx
216	pushl	%ebp
217	pushl	%ebx
218	pushl	%edi
219	pushl	%esi
220	movl	%ecx, %ebx
221	jmp	1f
222
2230:	/* top, read another word from the indirection page */
224	movl	(%ebx), %ecx
225	addl	$4, %ebx
2261:
227	testb	$0x1, %cl     /* is it a destination page */
228	jz	2f
229	movl	%ecx,	%edi
230	andl	$0xfffff000, %edi
231	jmp     0b
2322:
233	testb	$0x2, %cl    /* is it an indirection page */
234	jz	2f
235	movl	%ecx,	%ebx
236	andl	$0xfffff000, %ebx
237	jmp     0b
2382:
239	testb   $0x4, %cl    /* is it the done indicator */
240	jz      2f
241	jmp     3f
2422:
243	testb   $0x8, %cl    /* is it the source indicator */
244	jz      0b	     /* Ignore it otherwise */
245	movl    %ecx,   %esi /* For every source page do a copy */
246	andl    $0xfffff000, %esi
247
248	movl	%edi, %eax
249	movl	%esi, %ebp
250
251	movl	%edx, %edi
252	movl    $1024, %ecx
253	rep ; movsl
254
255	movl	%ebp, %edi
256	movl	%eax, %esi
257	movl	$1024, %ecx
258	rep ; movsl
259
260	movl	%eax, %edi
261	movl	%edx, %esi
262	movl	$1024, %ecx
263	rep ; movsl
264
265	lea	PAGE_SIZE(%ebp), %esi
266	jmp     0b
2673:
268	popl	%esi
269	popl	%edi
270	popl	%ebx
271	popl	%ebp
272	ret
273
274	.globl kexec_control_code_size
275.set kexec_control_code_size, . - relocate_kernel
276