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
38SYM_CODE_START_NOALIGN(relocate_kernel)
39	/* Save the CPU context, used for jumping back */
40
41	pushl	%ebx
42	pushl	%esi
43	pushl	%edi
44	pushl	%ebp
45	pushf
46
47	movl	20+8(%esp), %ebp /* list of pages */
48	movl	PTR(VA_CONTROL_PAGE)(%ebp), %edi
49	movl	%esp, ESP(%edi)
50	movl	%cr0, %eax
51	movl	%eax, CR0(%edi)
52	movl	%cr3, %eax
53	movl	%eax, CR3(%edi)
54	movl	%cr4, %eax
55	movl	%eax, CR4(%edi)
56
57	/* read the arguments and say goodbye to the stack */
58	movl  20+4(%esp), %ebx /* page_list */
59	movl  20+8(%esp), %ebp /* list of pages */
60	movl  20+12(%esp), %edx /* start address */
61	movl  20+16(%esp), %ecx /* cpu_has_pae */
62	movl  20+20(%esp), %esi /* preserve_context */
63
64	/* zero out flags, and disable interrupts */
65	pushl $0
66	popfl
67
68	/* save some information for jumping back */
69	movl	PTR(VA_CONTROL_PAGE)(%ebp), %edi
70	movl	%edi, CP_VA_CONTROL_PAGE(%edi)
71	movl	PTR(PA_PGD)(%ebp), %eax
72	movl	%eax, CP_PA_PGD(%edi)
73	movl	PTR(PA_SWAP_PAGE)(%ebp), %eax
74	movl	%eax, CP_PA_SWAP_PAGE(%edi)
75	movl	%ebx, CP_PA_BACKUP_PAGES_MAP(%edi)
76
77	/*
78	 * get physical address of control page now
79	 * this is impossible after page table switch
80	 */
81	movl	PTR(PA_CONTROL_PAGE)(%ebp), %edi
82
83	/* switch to new set of page tables */
84	movl	PTR(PA_PGD)(%ebp), %eax
85	movl	%eax, %cr3
86
87	/* setup a new stack at the end of the physical control page */
88	lea	PAGE_SIZE(%edi), %esp
89
90	/* jump to identity mapped page */
91	movl    %edi, %eax
92	addl    $(identity_mapped - relocate_kernel), %eax
93	pushl   %eax
94	ret
95SYM_CODE_END(relocate_kernel)
96
97SYM_CODE_START_LOCAL_NOALIGN(identity_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	 *  - Protected 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
194SYM_CODE_END(identity_mapped)
195
196SYM_CODE_START_LOCAL_NOALIGN(virtual_mapped)
197	movl	CR4(%edi), %eax
198	movl	%eax, %cr4
199	movl	CR3(%edi), %eax
200	movl	%eax, %cr3
201	movl	CR0(%edi), %eax
202	movl	%eax, %cr0
203	movl	ESP(%edi), %esp
204	movl	%ebp, %eax
205
206	popf
207	popl	%ebp
208	popl	%edi
209	popl	%esi
210	popl	%ebx
211	ret
212SYM_CODE_END(virtual_mapped)
213
214	/* Do the copies */
215SYM_CODE_START_LOCAL_NOALIGN(swap_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	testb	$0x1, %cl     /* is it a destination page */
230	jz	2f
231	movl	%ecx,	%edi
232	andl	$0xfffff000, %edi
233	jmp     0b
2342:
235	testb	$0x2, %cl    /* is it an indirection page */
236	jz	2f
237	movl	%ecx,	%ebx
238	andl	$0xfffff000, %ebx
239	jmp     0b
2402:
241	testb   $0x4, %cl    /* is it the done indicator */
242	jz      2f
243	jmp     3f
2442:
245	testb   $0x8, %cl    /* 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
275SYM_CODE_END(swap_pages)
276
277	.globl kexec_control_code_size
278.set kexec_control_code_size, . - relocate_kernel
279