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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/nospec-branch.h>
11#include <asm/processor-flags.h>
12
13/*
14 * Must be relocatable PIC code callable as a C function, in particular
15 * there must be a plain RET and not jump to return thunk.
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
40SYM_CODE_START_NOALIGN(relocate_kernel)
41 /* Save the CPU context, used for jumping back */
42
43 pushl %ebx
44 pushl %esi
45 pushl %edi
46 pushl %ebp
47 pushf
48
49 movl 20+8(%esp), %ebp /* list of pages */
50 movl PTR(VA_CONTROL_PAGE)(%ebp), %edi
51 movl %esp, ESP(%edi)
52 movl %cr0, %eax
53 movl %eax, CR0(%edi)
54 movl %cr3, %eax
55 movl %eax, CR3(%edi)
56 movl %cr4, %eax
57 movl %eax, CR4(%edi)
58
59 /* read the arguments and say goodbye to the stack */
60 movl 20+4(%esp), %ebx /* page_list */
61 movl 20+8(%esp), %ebp /* list of pages */
62 movl 20+12(%esp), %edx /* start address */
63 movl 20+16(%esp), %ecx /* cpu_has_pae */
64 movl 20+20(%esp), %esi /* preserve_context */
65
66 /* zero out flags, and disable interrupts */
67 pushl $0
68 popfl
69
70 /* save some information for jumping back */
71 movl PTR(VA_CONTROL_PAGE)(%ebp), %edi
72 movl %edi, CP_VA_CONTROL_PAGE(%edi)
73 movl PTR(PA_PGD)(%ebp), %eax
74 movl %eax, CP_PA_PGD(%edi)
75 movl PTR(PA_SWAP_PAGE)(%ebp), %eax
76 movl %eax, CP_PA_SWAP_PAGE(%edi)
77 movl %ebx, CP_PA_BACKUP_PAGES_MAP(%edi)
78
79 /*
80 * get physical address of control page now
81 * this is impossible after page table switch
82 */
83 movl PTR(PA_CONTROL_PAGE)(%ebp), %edi
84
85 /* switch to new set of page tables */
86 movl PTR(PA_PGD)(%ebp), %eax
87 movl %eax, %cr3
88
89 /* setup a new stack at the end of the physical control page */
90 lea PAGE_SIZE(%edi), %esp
91
92 /* jump to identity mapped page */
93 movl %edi, %eax
94 addl $(identity_mapped - relocate_kernel), %eax
95 pushl %eax
96 ANNOTATE_UNRET_SAFE
97 ret
98 int3
99SYM_CODE_END(relocate_kernel)
100
101SYM_CODE_START_LOCAL_NOALIGN(identity_mapped)
102 /* set return address to 0 if not preserving context */
103 pushl $0
104 /* store the start address on the stack */
105 pushl %edx
106
107 /*
108 * Set cr0 to a known state:
109 * - Paging disabled
110 * - Alignment check disabled
111 * - Write protect disabled
112 * - No task switch
113 * - Don't do FP software emulation.
114 * - Protected mode enabled
115 */
116 movl %cr0, %eax
117 andl $~(X86_CR0_PG | X86_CR0_AM | X86_CR0_WP | X86_CR0_TS | X86_CR0_EM), %eax
118 orl $(X86_CR0_PE), %eax
119 movl %eax, %cr0
120
121 /* clear cr4 if applicable */
122 testl %ecx, %ecx
123 jz 1f
124 /*
125 * Set cr4 to a known state:
126 * Setting everything to zero seems safe.
127 */
128 xorl %eax, %eax
129 movl %eax, %cr4
130
131 jmp 1f
1321:
133
134 /* Flush the TLB (needed?) */
135 xorl %eax, %eax
136 movl %eax, %cr3
137
138 movl CP_PA_SWAP_PAGE(%edi), %eax
139 pushl %eax
140 pushl %ebx
141 call swap_pages
142 addl $8, %esp
143
144 /*
145 * To be certain of avoiding problems with self-modifying code
146 * I need to execute a serializing instruction here.
147 * So I flush the TLB, it's handy, and not processor dependent.
148 */
149 xorl %eax, %eax
150 movl %eax, %cr3
151
152 /*
153 * set all of the registers to known values
154 * leave %esp alone
155 */
156
157 testl %esi, %esi
158 jnz 1f
159 xorl %edi, %edi
160 xorl %eax, %eax
161 xorl %ebx, %ebx
162 xorl %ecx, %ecx
163 xorl %edx, %edx
164 xorl %esi, %esi
165 xorl %ebp, %ebp
166 ANNOTATE_UNRET_SAFE
167 ret
168 int3
1691:
170 popl %edx
171 movl CP_PA_SWAP_PAGE(%edi), %esp
172 addl $PAGE_SIZE, %esp
1732:
174 ANNOTATE_RETPOLINE_SAFE
175 call *%edx
176
177 /* get the re-entry point of the peer system */
178 movl 0(%esp), %ebp
179 call 1f
1801:
181 popl %ebx
182 subl $(1b - relocate_kernel), %ebx
183 movl CP_VA_CONTROL_PAGE(%ebx), %edi
184 lea PAGE_SIZE(%ebx), %esp
185 movl CP_PA_SWAP_PAGE(%ebx), %eax
186 movl CP_PA_BACKUP_PAGES_MAP(%ebx), %edx
187 pushl %eax
188 pushl %edx
189 call swap_pages
190 addl $8, %esp
191 movl CP_PA_PGD(%ebx), %eax
192 movl %eax, %cr3
193 movl %cr0, %eax
194 orl $X86_CR0_PG, %eax
195 movl %eax, %cr0
196 lea PAGE_SIZE(%edi), %esp
197 movl %edi, %eax
198 addl $(virtual_mapped - relocate_kernel), %eax
199 pushl %eax
200 ANNOTATE_UNRET_SAFE
201 ret
202 int3
203SYM_CODE_END(identity_mapped)
204
205SYM_CODE_START_LOCAL_NOALIGN(virtual_mapped)
206 movl CR4(%edi), %eax
207 movl %eax, %cr4
208 movl CR3(%edi), %eax
209 movl %eax, %cr3
210 movl CR0(%edi), %eax
211 movl %eax, %cr0
212 movl ESP(%edi), %esp
213 movl %ebp, %eax
214
215 popf
216 popl %ebp
217 popl %edi
218 popl %esi
219 popl %ebx
220 ANNOTATE_UNRET_SAFE
221 ret
222 int3
223SYM_CODE_END(virtual_mapped)
224
225 /* Do the copies */
226SYM_CODE_START_LOCAL_NOALIGN(swap_pages)
227 movl 8(%esp), %edx
228 movl 4(%esp), %ecx
229 pushl %ebp
230 pushl %ebx
231 pushl %edi
232 pushl %esi
233 movl %ecx, %ebx
234 jmp 1f
235
2360: /* top, read another word from the indirection page */
237 movl (%ebx), %ecx
238 addl $4, %ebx
2391:
240 testb $0x1, %cl /* is it a destination page */
241 jz 2f
242 movl %ecx, %edi
243 andl $0xfffff000, %edi
244 jmp 0b
2452:
246 testb $0x2, %cl /* is it an indirection page */
247 jz 2f
248 movl %ecx, %ebx
249 andl $0xfffff000, %ebx
250 jmp 0b
2512:
252 testb $0x4, %cl /* is it the done indicator */
253 jz 2f
254 jmp 3f
2552:
256 testb $0x8, %cl /* is it the source indicator */
257 jz 0b /* Ignore it otherwise */
258 movl %ecx, %esi /* For every source page do a copy */
259 andl $0xfffff000, %esi
260
261 movl %edi, %eax
262 movl %esi, %ebp
263
264 movl %edx, %edi
265 movl $1024, %ecx
266 rep movsl
267
268 movl %ebp, %edi
269 movl %eax, %esi
270 movl $1024, %ecx
271 rep movsl
272
273 movl %eax, %edi
274 movl %edx, %esi
275 movl $1024, %ecx
276 rep movsl
277
278 lea PAGE_SIZE(%ebp), %esi
279 jmp 0b
2803:
281 popl %esi
282 popl %edi
283 popl %ebx
284 popl %ebp
285 ANNOTATE_UNRET_SAFE
286 ret
287 int3
288SYM_CODE_END(swap_pages)
289
290 .globl kexec_control_code_size
291.set kexec_control_code_size, . - relocate_kernel