1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
|
/* SPDX-License-Identifier: GPL-2.0-only */
/*
* relocate_kernel.S - put the kernel image in place to boot
* Copyright (C) 2002-2004 Eric Biederman <ebiederm@xmission.com>
*/
#include <linux/linkage.h>
#include <asm/page_types.h>
#include <asm/kexec.h>
#include <asm/nospec-branch.h>
#include <asm/processor-flags.h>
/*
* Must be relocatable PIC code callable as a C function, in particular
* there must be a plain RET and not jump to return thunk.
*/
#define PTR(x) (x << 2)
/*
* control_page + KEXEC_CONTROL_CODE_MAX_SIZE
* ~ control_page + PAGE_SIZE are used as data storage and stack for
* jumping back
*/
#define DATA(offset) (KEXEC_CONTROL_CODE_MAX_SIZE+(offset))
/* Minimal CPU state */
#define ESP DATA(0x0)
#define CR0 DATA(0x4)
#define CR3 DATA(0x8)
#define CR4 DATA(0xc)
/* other data */
#define CP_VA_CONTROL_PAGE DATA(0x10)
#define CP_PA_PGD DATA(0x14)
#define CP_PA_SWAP_PAGE DATA(0x18)
#define CP_PA_BACKUP_PAGES_MAP DATA(0x1c)
.text
SYM_CODE_START_NOALIGN(relocate_kernel)
/* Save the CPU context, used for jumping back */
pushl %ebx
pushl %esi
pushl %edi
pushl %ebp
pushf
movl 20+8(%esp), %ebp /* list of pages */
movl PTR(VA_CONTROL_PAGE)(%ebp), %edi
movl %esp, ESP(%edi)
movl %cr0, %eax
movl %eax, CR0(%edi)
movl %cr3, %eax
movl %eax, CR3(%edi)
movl %cr4, %eax
movl %eax, CR4(%edi)
/* read the arguments and say goodbye to the stack */
movl 20+4(%esp), %ebx /* page_list */
movl 20+8(%esp), %ebp /* list of pages */
movl 20+12(%esp), %edx /* start address */
movl 20+16(%esp), %ecx /* cpu_has_pae */
movl 20+20(%esp), %esi /* preserve_context */
/* zero out flags, and disable interrupts */
pushl $0
popfl
/* save some information for jumping back */
movl PTR(VA_CONTROL_PAGE)(%ebp), %edi
movl %edi, CP_VA_CONTROL_PAGE(%edi)
movl PTR(PA_PGD)(%ebp), %eax
movl %eax, CP_PA_PGD(%edi)
movl PTR(PA_SWAP_PAGE)(%ebp), %eax
movl %eax, CP_PA_SWAP_PAGE(%edi)
movl %ebx, CP_PA_BACKUP_PAGES_MAP(%edi)
/*
* get physical address of control page now
* this is impossible after page table switch
*/
movl PTR(PA_CONTROL_PAGE)(%ebp), %edi
/* switch to new set of page tables */
movl PTR(PA_PGD)(%ebp), %eax
movl %eax, %cr3
/* setup a new stack at the end of the physical control page */
lea PAGE_SIZE(%edi), %esp
/* jump to identity mapped page */
movl %edi, %eax
addl $(identity_mapped - relocate_kernel), %eax
pushl %eax
ANNOTATE_UNRET_SAFE
ret
int3
SYM_CODE_END(relocate_kernel)
SYM_CODE_START_LOCAL_NOALIGN(identity_mapped)
/* set return address to 0 if not preserving context */
pushl $0
/* store the start address on the stack */
pushl %edx
/*
* Set cr0 to a known state:
* - Paging disabled
* - Alignment check disabled
* - Write protect disabled
* - No task switch
* - Don't do FP software emulation.
* - Proctected mode enabled
*/
movl %cr0, %eax
andl $~(X86_CR0_PG | X86_CR0_AM | X86_CR0_WP | X86_CR0_TS | X86_CR0_EM), %eax
orl $(X86_CR0_PE), %eax
movl %eax, %cr0
/* clear cr4 if applicable */
testl %ecx, %ecx
jz 1f
/*
* Set cr4 to a known state:
* Setting everything to zero seems safe.
*/
xorl %eax, %eax
movl %eax, %cr4
jmp 1f
1:
/* Flush the TLB (needed?) */
xorl %eax, %eax
movl %eax, %cr3
movl CP_PA_SWAP_PAGE(%edi), %eax
pushl %eax
pushl %ebx
call swap_pages
addl $8, %esp
/*
* To be certain of avoiding problems with self-modifying code
* I need to execute a serializing instruction here.
* So I flush the TLB, it's handy, and not processor dependent.
*/
xorl %eax, %eax
movl %eax, %cr3
/*
* set all of the registers to known values
* leave %esp alone
*/
testl %esi, %esi
jnz 1f
xorl %edi, %edi
xorl %eax, %eax
xorl %ebx, %ebx
xorl %ecx, %ecx
xorl %edx, %edx
xorl %esi, %esi
xorl %ebp, %ebp
ANNOTATE_UNRET_SAFE
ret
int3
1:
popl %edx
movl CP_PA_SWAP_PAGE(%edi), %esp
addl $PAGE_SIZE, %esp
2:
ANNOTATE_RETPOLINE_SAFE
call *%edx
/* get the re-entry point of the peer system */
movl 0(%esp), %ebp
call 1f
1:
popl %ebx
subl $(1b - relocate_kernel), %ebx
movl CP_VA_CONTROL_PAGE(%ebx), %edi
lea PAGE_SIZE(%ebx), %esp
movl CP_PA_SWAP_PAGE(%ebx), %eax
movl CP_PA_BACKUP_PAGES_MAP(%ebx), %edx
pushl %eax
pushl %edx
call swap_pages
addl $8, %esp
movl CP_PA_PGD(%ebx), %eax
movl %eax, %cr3
movl %cr0, %eax
orl $X86_CR0_PG, %eax
movl %eax, %cr0
lea PAGE_SIZE(%edi), %esp
movl %edi, %eax
addl $(virtual_mapped - relocate_kernel), %eax
pushl %eax
ANNOTATE_UNRET_SAFE
ret
int3
SYM_CODE_END(identity_mapped)
SYM_CODE_START_LOCAL_NOALIGN(virtual_mapped)
movl CR4(%edi), %eax
movl %eax, %cr4
movl CR3(%edi), %eax
movl %eax, %cr3
movl CR0(%edi), %eax
movl %eax, %cr0
movl ESP(%edi), %esp
movl %ebp, %eax
popf
popl %ebp
popl %edi
popl %esi
popl %ebx
ANNOTATE_UNRET_SAFE
ret
int3
SYM_CODE_END(virtual_mapped)
/* Do the copies */
SYM_CODE_START_LOCAL_NOALIGN(swap_pages)
movl 8(%esp), %edx
movl 4(%esp), %ecx
pushl %ebp
pushl %ebx
pushl %edi
pushl %esi
movl %ecx, %ebx
jmp 1f
0: /* top, read another word from the indirection page */
movl (%ebx), %ecx
addl $4, %ebx
1:
testb $0x1, %cl /* is it a destination page */
jz 2f
movl %ecx, %edi
andl $0xfffff000, %edi
jmp 0b
2:
testb $0x2, %cl /* is it an indirection page */
jz 2f
movl %ecx, %ebx
andl $0xfffff000, %ebx
jmp 0b
2:
testb $0x4, %cl /* is it the done indicator */
jz 2f
jmp 3f
2:
testb $0x8, %cl /* is it the source indicator */
jz 0b /* Ignore it otherwise */
movl %ecx, %esi /* For every source page do a copy */
andl $0xfffff000, %esi
movl %edi, %eax
movl %esi, %ebp
movl %edx, %edi
movl $1024, %ecx
rep ; movsl
movl %ebp, %edi
movl %eax, %esi
movl $1024, %ecx
rep ; movsl
movl %eax, %edi
movl %edx, %esi
movl $1024, %ecx
rep ; movsl
lea PAGE_SIZE(%ebp), %esi
jmp 0b
3:
popl %esi
popl %edi
popl %ebx
popl %ebp
ANNOTATE_UNRET_SAFE
ret
int3
SYM_CODE_END(swap_pages)
.globl kexec_control_code_size
.set kexec_control_code_size, . - relocate_kernel
|
