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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>
14#include <asm/ptrace.h>
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.
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.
32 */
33
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
4220: mvcle %r0,%r2,0
43 jo 20b
44.endm
45
46.macro MEMSWAP dst,src,buf,len
4710: larl %r0,purgatory_end
48 larl %r1,stack
49 slgr %r0,%r1
50 cgr \len,%r0
51 jh 11f
52 lgr %r4,\len
53 j 12f
5411: lgr %r4,%r0
55
5612: MEMCPY \buf,\dst,%r4
57 MEMCPY \dst,\src,%r4
58 MEMCPY \src,\buf,%r4
59
60 agr \dst,%r4
61 agr \src,%r4
62 sgr \len,%r4
63
64 cghi \len,0
65 jh 10b
66.endm
67
68.macro START_NEXT_KERNEL base subcode
69 lg %r4,kernel_entry-\base(%r13)
70 lg %r5,load_psw_mask-\base(%r13)
71 ogr %r4,%r5
72 stg %r4,0(%r0)
73
74 xgr %r0,%r0
75 lghi %r1,\subcode
76 diag %r0,%r1,0x308
77.endm
78
79 .text
80 .balign PAGE_SIZE
81SYM_CODE_START(purgatory_start)
82 /* The purgatory might be called after a diag308 so better set
83 * architecture and addressing mode.
84 */
85 lhi %r1,1
86 sigp %r1,%r0,SIGP_SET_ARCHITECTURE
87 sam64
88
89 larl %r5,gprregs
90 stmg %r6,%r15,0(%r5)
91
92 basr %r13,0
93.base_crash:
94
95 /* Setup stack */
96 larl %r15,purgatory_end-STACK_FRAME_OVERHEAD
97
98 /* If the next kernel is KEXEC_TYPE_CRASH the purgatory is called
99 * directly with a flag passed in %r2 whether the purgatory shall do
100 * checksum verification only (%r2 = 0 -> verification only).
101 *
102 * Check now and preserve over C function call by storing in
103 * %r10 with
104 * 1 -> checksum verification only
105 * 0 -> load new kernel
106 */
107 lghi %r10,0
108 lg %r11,kernel_type-.base_crash(%r13)
109 cghi %r11,1 /* KEXEC_TYPE_CRASH */
110 jne .do_checksum_verification
111 cghi %r2,0 /* checksum verification only */
112 jne .do_checksum_verification
113 lghi %r10,1
114
115.do_checksum_verification:
116 brasl %r14,verify_sha256_digest
117
118 cghi %r10,1 /* checksum verification only */
119 je .return_old_kernel
120 cghi %r2,0 /* checksum match */
121 jne .disabled_wait
122
123 /* If the next kernel is a crash kernel the purgatory has to swap
124 * the mem regions first.
125 */
126 cghi %r11,1 /* KEXEC_TYPE_CRASH */
127 je .start_crash_kernel
128
129 /* start normal kernel */
130 START_NEXT_KERNEL .base_crash 0
131
132.return_old_kernel:
133 lmg %r6,%r15,gprregs-.base_crash(%r13)
134 br %r14
135
136.disabled_wait:
137 lpswe disabled_wait_psw-.base_crash(%r13)
138
139.start_crash_kernel:
140 /* Location of purgatory_start in crash memory */
141 larl %r0,.base_crash
142 larl %r1,purgatory_start
143 slgr %r0,%r1
144 lgr %r8,%r13
145 sgr %r8,%r0
146
147 /* Destination for this code i.e. end of memory to be swapped. */
148 larl %r0,purgatory_end
149 larl %r1,purgatory_start
150 slgr %r0,%r1
151 lg %r9,crash_size-.base_crash(%r13)
152 sgr %r9,%r0
153
154 /* Destination in crash memory, i.e. same as r9 but in crash memory. */
155 lg %r10,crash_start-.base_crash(%r13)
156 agr %r10,%r9
157
158 /* Buffer location (in crash memory) and size. As the purgatory is
159 * behind the point of no return it can re-use the stack as buffer.
160 */
161 larl %r11,purgatory_end
162 larl %r12,stack
163 slgr %r11,%r12
164
165 MEMCPY %r12,%r9,%r11 /* dst -> (crash) buf */
166 MEMCPY %r9,%r8,%r11 /* self -> dst */
167
168 /* Jump to new location. */
169 lgr %r7,%r9
170 larl %r0,.jump_to_dst
171 larl %r1,purgatory_start
172 slgr %r0,%r1
173 agr %r7,%r0
174 br %r7
175
176.jump_to_dst:
177 basr %r13,0
178.base_dst:
179
180 /* clear buffer */
181 MEMCPY %r12,%r10,%r11 /* (crash) buf -> (crash) dst */
182
183 /* Load new buffer location after jump */
184 larl %r7,stack
185 lgr %r0,%r7
186 larl %r1,purgatory_start
187 slgr %r0,%r1
188 agr %r10,%r0
189 MEMCPY %r10,%r7,%r11 /* (new) buf -> (crash) buf */
190
191 /* Now the code is set up to run from its designated location. Start
192 * swapping the rest of crash memory now.
193 *
194 * The registers will be used as follow:
195 *
196 * %r0-%r4 reserved for macros defined above
197 * %r5-%r6 tmp registers
198 * %r7 pointer to current struct sha region
199 * %r8 index to iterate over all sha regions
200 * %r9 pointer in crash memory
201 * %r10 pointer in old kernel
202 * %r11 total size (still) to be moved
203 * %r12 pointer to buffer
204 */
205 lgr %r12,%r7
206 lgr %r11,%r9
207 lghi %r10,0
208 lg %r9,crash_start-.base_dst(%r13)
209 lghi %r8,16 /* KEXEC_SEGMENTS_MAX */
210 larl %r7,purgatory_sha_regions
211
212 j .loop_first
213
214 /* Loop over all purgatory_sha_regions. */
215.loop_next:
216 aghi %r8,-1
217 cghi %r8,0
218 je .loop_out
219
220 aghi %r7,__KEXEC_SHA_REGION_SIZE
221
222.loop_first:
223 lg %r5,__KEXEC_SHA_REGION_START(%r7)
224 cghi %r5,0
225 je .loop_next
226
227 /* Copy [end last sha region, start current sha region) */
228 /* Note: kexec_sha_region->start points in crash memory */
229 sgr %r5,%r9
230 MEMCPY %r9,%r10,%r5
231
232 agr %r9,%r5
233 agr %r10,%r5
234 sgr %r11,%r5
235
236 /* Swap sha region */
237 lg %r6,__KEXEC_SHA_REGION_LEN(%r7)
238 MEMSWAP %r9,%r10,%r12,%r6
239 sg %r11,__KEXEC_SHA_REGION_LEN(%r7)
240 j .loop_next
241
242.loop_out:
243 /* Copy rest of crash memory */
244 MEMCPY %r9,%r10,%r11
245
246 /* start crash kernel */
247 START_NEXT_KERNEL .base_dst 1
248SYM_CODE_END(purgatory_start)
249
250SYM_DATA_LOCAL(load_psw_mask, .long 0x00080000,0x80000000)
251 .balign 8
252SYM_DATA_LOCAL(disabled_wait_psw, .quad 0x0002000180000000,.do_checksum_verification)
253SYM_DATA_LOCAL(gprregs, .fill 10,8,0)
254SYM_DATA(purgatory_sha256_digest, .skip 32)
255SYM_DATA(purgatory_sha_regions, .skip 16*__KEXEC_SHA_REGION_SIZE)
256SYM_DATA(kernel_entry, .skip 8)
257SYM_DATA(kernel_type, .skip 8)
258SYM_DATA(crash_start, .skip 8)
259SYM_DATA(crash_size, .skip 8)
260 .balign PAGE_SIZE
261SYM_DATA_START_LOCAL(stack)
262 /* The buffer to move this code must be as big as the code. */
263 .skip stack-purgatory_start
264 .balign PAGE_SIZE
265SYM_DATA_END_LABEL(stack, SYM_L_LOCAL, purgatory_end)
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>
14#include <asm/ptrace.h>
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.
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.
32 */
33
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
4220: mvcle %r0,%r2,0
43 jo 20b
44.endm
45
46.macro MEMSWAP dst,src,buf,len
4710: cghi \len,bufsz
48 jh 11f
49 lgr %r4,\len
50 j 12f
5111: lghi %r4,bufsz
52
5312: 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
65.macro START_NEXT_KERNEL base subcode
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 lghi %r1,\subcode
73 diag %r0,%r1,0x308
74.endm
75
76.text
77.align PAGE_SIZE
78ENTRY(purgatory_start)
79 /* The purgatory might be called after a diag308 so better set
80 * architecture and addressing mode.
81 */
82 lhi %r1,1
83 sigp %r1,%r0,SIGP_SET_ARCHITECTURE
84 sam64
85
86 larl %r5,gprregs
87 stmg %r6,%r15,0(%r5)
88
89 basr %r13,0
90.base_crash:
91
92 /* Setup stack */
93 larl %r15,purgatory_end-STACK_FRAME_OVERHEAD
94
95 /* If the next kernel is KEXEC_TYPE_CRASH the purgatory is called
96 * directly with a flag passed in %r2 whether the purgatory shall do
97 * checksum verification only (%r2 = 0 -> verification only).
98 *
99 * Check now and preserve over C function call by storing in
100 * %r10 whith
101 * 1 -> checksum verification only
102 * 0 -> load new kernel
103 */
104 lghi %r10,0
105 lg %r11,kernel_type-.base_crash(%r13)
106 cghi %r11,1 /* KEXEC_TYPE_CRASH */
107 jne .do_checksum_verification
108 cghi %r2,0 /* checksum verification only */
109 jne .do_checksum_verification
110 lghi %r10,1
111
112.do_checksum_verification:
113 brasl %r14,verify_sha256_digest
114
115 cghi %r10,1 /* checksum verification only */
116 je .return_old_kernel
117 cghi %r2,0 /* checksum match */
118 jne .disabled_wait
119
120 /* If the next kernel is a crash kernel the purgatory has to swap
121 * the mem regions first.
122 */
123 cghi %r11,1 /* KEXEC_TYPE_CRASH */
124 je .start_crash_kernel
125
126 /* start normal kernel */
127 START_NEXT_KERNEL .base_crash 0
128
129.return_old_kernel:
130 lmg %r6,%r15,gprregs-.base_crash(%r13)
131 br %r14
132
133.disabled_wait:
134 lpswe disabled_wait_psw-.base_crash(%r13)
135
136.start_crash_kernel:
137 /* Location of purgatory_start in crash memory */
138 lgr %r8,%r13
139 aghi %r8,-(.base_crash-purgatory_start)
140
141 /* Destination for this code i.e. end of memory to be swapped. */
142 lg %r9,crash_size-.base_crash(%r13)
143 aghi %r9,-(purgatory_end-purgatory_start)
144
145 /* Destination in crash memory, i.e. same as r9 but in crash memory. */
146 lg %r10,crash_start-.base_crash(%r13)
147 agr %r10,%r9
148
149 /* Buffer location (in crash memory) and size. As the purgatory is
150 * behind the point of no return it can re-use the stack as buffer.
151 */
152 lghi %r11,bufsz
153 larl %r12,stack
154
155 MEMCPY %r12,%r9,%r11 /* dst -> (crash) buf */
156 MEMCPY %r9,%r8,%r11 /* self -> dst */
157
158 /* Jump to new location. */
159 lgr %r7,%r9
160 aghi %r7,.jump_to_dst-purgatory_start
161 br %r7
162
163.jump_to_dst:
164 basr %r13,0
165.base_dst:
166
167 /* clear buffer */
168 MEMCPY %r12,%r10,%r11 /* (crash) buf -> (crash) dst */
169
170 /* Load new buffer location after jump */
171 larl %r7,stack
172 aghi %r10,stack-purgatory_start
173 MEMCPY %r10,%r7,%r11 /* (new) buf -> (crash) buf */
174
175 /* Now the code is set up to run from its designated location. Start
176 * swapping the rest of crash memory now.
177 *
178 * The registers will be used as follow:
179 *
180 * %r0-%r4 reserved for macros defined above
181 * %r5-%r6 tmp registers
182 * %r7 pointer to current struct sha region
183 * %r8 index to iterate over all sha regions
184 * %r9 pointer in crash memory
185 * %r10 pointer in old kernel
186 * %r11 total size (still) to be moved
187 * %r12 pointer to buffer
188 */
189 lgr %r12,%r7
190 lgr %r11,%r9
191 lghi %r10,0
192 lg %r9,crash_start-.base_dst(%r13)
193 lghi %r8,16 /* KEXEC_SEGMENTS_MAX */
194 larl %r7,purgatory_sha_regions
195
196 j .loop_first
197
198 /* Loop over all purgatory_sha_regions. */
199.loop_next:
200 aghi %r8,-1
201 cghi %r8,0
202 je .loop_out
203
204 aghi %r7,__KEXEC_SHA_REGION_SIZE
205
206.loop_first:
207 lg %r5,__KEXEC_SHA_REGION_START(%r7)
208 cghi %r5,0
209 je .loop_next
210
211 /* Copy [end last sha region, start current sha region) */
212 /* Note: kexec_sha_region->start points in crash memory */
213 sgr %r5,%r9
214 MEMCPY %r9,%r10,%r5
215
216 agr %r9,%r5
217 agr %r10,%r5
218 sgr %r11,%r5
219
220 /* Swap sha region */
221 lg %r6,__KEXEC_SHA_REGION_LEN(%r7)
222 MEMSWAP %r9,%r10,%r12,%r6
223 sg %r11,__KEXEC_SHA_REGION_LEN(%r7)
224 j .loop_next
225
226.loop_out:
227 /* Copy rest of crash memory */
228 MEMCPY %r9,%r10,%r11
229
230 /* start crash kernel */
231 START_NEXT_KERNEL .base_dst 1
232
233
234load_psw_mask:
235 .long 0x00080000,0x80000000
236
237 .align 8
238disabled_wait_psw:
239 .quad 0x0002000180000000
240 .quad 0x0000000000000000 + .do_checksum_verification
241
242gprregs:
243 .rept 10
244 .quad 0
245 .endr
246
247/* Macro to define a global variable with name and size (in bytes) to be
248 * shared with C code.
249 *
250 * Add the .size and .type attribute to satisfy checks on the Elf_Sym during
251 * purgatory load.
252 */
253.macro GLOBAL_VARIABLE name,size
254\name:
255 .global \name
256 .size \name,\size
257 .type \name,object
258 .skip \size,0
259.endm
260
261GLOBAL_VARIABLE purgatory_sha256_digest,32
262GLOBAL_VARIABLE purgatory_sha_regions,16*__KEXEC_SHA_REGION_SIZE
263GLOBAL_VARIABLE kernel_entry,8
264GLOBAL_VARIABLE kernel_type,8
265GLOBAL_VARIABLE crash_start,8
266GLOBAL_VARIABLE crash_size,8
267
268 .align PAGE_SIZE
269stack:
270 /* The buffer to move this code must be as big as the code. */
271 .skip stack-purgatory_start
272 .align PAGE_SIZE
273purgatory_end: