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840798a1 PR |
1 | /* SPDX-License-Identifier: GPL-2.0 */ |
2 | /* | |
3 | * Purgatory setup code | |
4 | * | |
5 | * Copyright IBM Corp. 2018 | |
6 | * | |
7 | * Author(s): Philipp Rudo <prudo@linux.vnet.ibm.com> | |
8 | */ | |
9 | ||
10 | #include <linux/linkage.h> | |
11 | #include <asm/asm-offsets.h> | |
12 | #include <asm/page.h> | |
13 | #include <asm/sigp.h> | |
4e62d458 | 14 | #include <asm/ptrace.h> |
840798a1 PR |
15 | |
16 | /* The purgatory is the code running between two kernels. It's main purpose | |
17 | * is to verify that the next kernel was not corrupted after load and to | |
18 | * start it. | |
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19 | * |
20 | * If the next kernel is a crash kernel there are some peculiarities to | |
21 | * consider: | |
22 | * | |
23 | * First the purgatory is called twice. Once only to verify the | |
24 | * sha digest. So if the crash kernel got corrupted the old kernel can try | |
25 | * to trigger a stand-alone dumper. And once to actually load the crash kernel. | |
26 | * | |
27 | * Second the purgatory also has to swap the crash memory region with its | |
28 | * destination at address 0. As the purgatory is part of crash memory this | |
29 | * requires some finesse. The tactic here is that the purgatory first copies | |
30 | * itself to the end of the destination and then swaps the rest of the | |
31 | * memory running from there. | |
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32 | */ |
33 | ||
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34 | #define bufsz purgatory_end-stack |
35 | ||
36 | .macro MEMCPY dst,src,len | |
37 | lgr %r0,\dst | |
38 | lgr %r1,\len | |
39 | lgr %r2,\src | |
40 | lgr %r3,\len | |
41 | ||
42 | 20: mvcle %r0,%r2,0 | |
43 | jo 20b | |
44 | .endm | |
45 | ||
46 | .macro MEMSWAP dst,src,buf,len | |
47 | 10: cghi \len,bufsz | |
48 | jh 11f | |
49 | lgr %r4,\len | |
50 | j 12f | |
51 | 11: lghi %r4,bufsz | |
52 | ||
53 | 12: MEMCPY \buf,\dst,%r4 | |
54 | MEMCPY \dst,\src,%r4 | |
55 | MEMCPY \src,\buf,%r4 | |
56 | ||
57 | agr \dst,%r4 | |
58 | agr \src,%r4 | |
59 | sgr \len,%r4 | |
60 | ||
61 | cghi \len,0 | |
62 | jh 10b | |
63 | .endm | |
64 | ||
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65 | .macro START_NEXT_KERNEL base |
66 | lg %r4,kernel_entry-\base(%r13) | |
67 | lg %r5,load_psw_mask-\base(%r13) | |
68 | ogr %r4,%r5 | |
69 | stg %r4,0(%r0) | |
70 | ||
71 | xgr %r0,%r0 | |
72 | diag %r0,%r0,0x308 | |
73 | .endm | |
74 | ||
75 | .text | |
76 | .align PAGE_SIZE | |
77 | ENTRY(purgatory_start) | |
78 | /* The purgatory might be called after a diag308 so better set | |
79 | * architecture and addressing mode. | |
80 | */ | |
81 | lhi %r1,1 | |
82 | sigp %r1,%r0,SIGP_SET_ARCHITECTURE | |
83 | sam64 | |
84 | ||
85 | larl %r5,gprregs | |
86 | stmg %r6,%r15,0(%r5) | |
87 | ||
88 | basr %r13,0 | |
89 | .base_crash: | |
90 | ||
91 | /* Setup stack */ | |
4e62d458 | 92 | larl %r15,purgatory_end-STACK_FRAME_OVERHEAD |
840798a1 | 93 | |
ee337f54 PR |
94 | /* If the next kernel is KEXEC_TYPE_CRASH the purgatory is called |
95 | * directly with a flag passed in %r2 whether the purgatory shall do | |
96 | * checksum verification only (%r2 = 0 -> verification only). | |
97 | * | |
98 | * Check now and preserve over C function call by storing in | |
99 | * %r10 whith | |
100 | * 1 -> checksum verification only | |
101 | * 0 -> load new kernel | |
102 | */ | |
103 | lghi %r10,0 | |
104 | lg %r11,kernel_type-.base_crash(%r13) | |
105 | cghi %r11,1 /* KEXEC_TYPE_CRASH */ | |
106 | jne .do_checksum_verification | |
107 | cghi %r2,0 /* checksum verification only */ | |
108 | jne .do_checksum_verification | |
109 | lghi %r10,1 | |
110 | ||
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111 | .do_checksum_verification: |
112 | brasl %r14,verify_sha256_digest | |
113 | ||
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114 | cghi %r10,1 /* checksum verification only */ |
115 | je .return_old_kernel | |
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116 | cghi %r2,0 /* checksum match */ |
117 | jne .disabled_wait | |
118 | ||
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119 | /* If the next kernel is a crash kernel the purgatory has to swap |
120 | * the mem regions first. | |
121 | */ | |
122 | cghi %r11,1 /* KEXEC_TYPE_CRASH */ | |
123 | je .start_crash_kernel | |
124 | ||
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125 | /* start normal kernel */ |
126 | START_NEXT_KERNEL .base_crash | |
127 | ||
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128 | .return_old_kernel: |
129 | lmg %r6,%r15,gprregs-.base_crash(%r13) | |
130 | br %r14 | |
131 | ||
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132 | .disabled_wait: |
133 | lpswe disabled_wait_psw-.base_crash(%r13) | |
134 | ||
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135 | .start_crash_kernel: |
136 | /* Location of purgatory_start in crash memory */ | |
137 | lgr %r8,%r13 | |
138 | aghi %r8,-(.base_crash-purgatory_start) | |
139 | ||
140 | /* Destination for this code i.e. end of memory to be swapped. */ | |
141 | lg %r9,crash_size-.base_crash(%r13) | |
142 | aghi %r9,-(purgatory_end-purgatory_start) | |
143 | ||
144 | /* Destination in crash memory, i.e. same as r9 but in crash memory. */ | |
145 | lg %r10,crash_start-.base_crash(%r13) | |
146 | agr %r10,%r9 | |
147 | ||
148 | /* Buffer location (in crash memory) and size. As the purgatory is | |
149 | * behind the point of no return it can re-use the stack as buffer. | |
150 | */ | |
151 | lghi %r11,bufsz | |
152 | larl %r12,stack | |
153 | ||
154 | MEMCPY %r12,%r9,%r11 /* dst -> (crash) buf */ | |
155 | MEMCPY %r9,%r8,%r11 /* self -> dst */ | |
156 | ||
157 | /* Jump to new location. */ | |
158 | lgr %r7,%r9 | |
159 | aghi %r7,.jump_to_dst-purgatory_start | |
160 | br %r7 | |
161 | ||
162 | .jump_to_dst: | |
163 | basr %r13,0 | |
164 | .base_dst: | |
165 | ||
166 | /* clear buffer */ | |
167 | MEMCPY %r12,%r10,%r11 /* (crash) buf -> (crash) dst */ | |
168 | ||
169 | /* Load new buffer location after jump */ | |
170 | larl %r7,stack | |
171 | aghi %r10,stack-purgatory_start | |
172 | MEMCPY %r10,%r7,%r11 /* (new) buf -> (crash) buf */ | |
173 | ||
174 | /* Now the code is set up to run from its designated location. Start | |
175 | * swapping the rest of crash memory now. | |
176 | * | |
177 | * The registers will be used as follow: | |
178 | * | |
179 | * %r0-%r4 reserved for macros defined above | |
180 | * %r5-%r6 tmp registers | |
181 | * %r7 pointer to current struct sha region | |
182 | * %r8 index to iterate over all sha regions | |
183 | * %r9 pointer in crash memory | |
184 | * %r10 pointer in old kernel | |
185 | * %r11 total size (still) to be moved | |
186 | * %r12 pointer to buffer | |
187 | */ | |
188 | lgr %r12,%r7 | |
189 | lgr %r11,%r9 | |
190 | lghi %r10,0 | |
191 | lg %r9,crash_start-.base_dst(%r13) | |
192 | lghi %r8,16 /* KEXEC_SEGMENTS_MAX */ | |
193 | larl %r7,purgatory_sha_regions | |
194 | ||
195 | j .loop_first | |
196 | ||
197 | /* Loop over all purgatory_sha_regions. */ | |
198 | .loop_next: | |
199 | aghi %r8,-1 | |
200 | cghi %r8,0 | |
201 | je .loop_out | |
202 | ||
203 | aghi %r7,__KEXEC_SHA_REGION_SIZE | |
204 | ||
205 | .loop_first: | |
206 | lg %r5,__KEXEC_SHA_REGION_START(%r7) | |
207 | cghi %r5,0 | |
208 | je .loop_next | |
209 | ||
210 | /* Copy [end last sha region, start current sha region) */ | |
211 | /* Note: kexec_sha_region->start points in crash memory */ | |
212 | sgr %r5,%r9 | |
213 | MEMCPY %r9,%r10,%r5 | |
214 | ||
215 | agr %r9,%r5 | |
216 | agr %r10,%r5 | |
217 | sgr %r11,%r5 | |
218 | ||
219 | /* Swap sha region */ | |
220 | lg %r6,__KEXEC_SHA_REGION_LEN(%r7) | |
221 | MEMSWAP %r9,%r10,%r12,%r6 | |
222 | sg %r11,__KEXEC_SHA_REGION_LEN(%r7) | |
223 | j .loop_next | |
224 | ||
225 | .loop_out: | |
226 | /* Copy rest of crash memory */ | |
227 | MEMCPY %r9,%r10,%r11 | |
228 | ||
229 | /* start crash kernel */ | |
230 | START_NEXT_KERNEL .base_dst | |
231 | ||
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232 | |
233 | load_psw_mask: | |
234 | .long 0x00080000,0x80000000 | |
235 | ||
236 | .align 8 | |
237 | disabled_wait_psw: | |
238 | .quad 0x0002000180000000 | |
239 | .quad 0x0000000000000000 + .do_checksum_verification | |
240 | ||
241 | gprregs: | |
242 | .rept 10 | |
243 | .quad 0 | |
244 | .endr | |
245 | ||
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246 | /* Macro to define a global variable with name and size (in bytes) to be |
247 | * shared with C code. | |
248 | * | |
249 | * Add the .size and .type attribute to satisfy checks on the Elf_Sym during | |
250 | * purgatory load. | |
251 | */ | |
252 | .macro GLOBAL_VARIABLE name,size | |
253 | \name: | |
254 | .global \name | |
255 | .size \name,\size | |
256 | .type \name,object | |
257 | .skip \size,0 | |
258 | .endm | |
ee337f54 | 259 | |
287d6070 PR |
260 | GLOBAL_VARIABLE purgatory_sha256_digest,32 |
261 | GLOBAL_VARIABLE purgatory_sha_regions,16*__KEXEC_SHA_REGION_SIZE | |
262 | GLOBAL_VARIABLE kernel_entry,8 | |
263 | GLOBAL_VARIABLE kernel_type,8 | |
264 | GLOBAL_VARIABLE crash_start,8 | |
265 | GLOBAL_VARIABLE crash_size,8 | |
ee337f54 | 266 | |
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267 | .align PAGE_SIZE |
268 | stack: | |
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269 | /* The buffer to move this code must be as big as the code. */ |
270 | .skip stack-purgatory_start | |
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271 | .align PAGE_SIZE |
272 | purgatory_end: |