1/* SPDX-License-Identifier: GPL-2.0-only */
2/*
3 * relocate_kernel.S - put the kernel image in place to boot
4 * Copyright (C) 2002-2005 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#include <asm/pgtable_types.h>
12
13/*
14 * Must be relocatable PIC code callable as a C function
15 */
16
17#define PTR(x) (x << 3)
18#define PAGE_ATTR (_PAGE_PRESENT | _PAGE_RW | _PAGE_ACCESSED | _PAGE_DIRTY)
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 RSP			DATA(0x0)
29#define CR0			DATA(0x8)
30#define CR3			DATA(0x10)
31#define CR4			DATA(0x18)
32
33/* other data */
34#define CP_PA_TABLE_PAGE	DATA(0x20)
35#define CP_PA_SWAP_PAGE		DATA(0x28)
36#define CP_PA_BACKUP_PAGES_MAP	DATA(0x30)
37
38	.text
39	.align PAGE_SIZE
40	.code64
41	.globl relocate_kernel
42relocate_kernel:
43	/*
44	 * %rdi indirection_page
45	 * %rsi page_list
46	 * %rdx start address
47	 * %rcx preserve_context
48	 * %r8  sme_active
49	 */
50
51	/* Save the CPU context, used for jumping back */
52	pushq %rbx
53	pushq %rbp
54	pushq %r12
55	pushq %r13
56	pushq %r14
57	pushq %r15
58	pushf
59
60	movq	PTR(VA_CONTROL_PAGE)(%rsi), %r11
61	movq	%rsp, RSP(%r11)
62	movq	%cr0, %rax
63	movq	%rax, CR0(%r11)
64	movq	%cr3, %rax
65	movq	%rax, CR3(%r11)
66	movq	%cr4, %rax
67	movq	%rax, CR4(%r11)
68
69	/* Save CR4. Required to enable the right paging mode later. */
70	movq	%rax, %r13
71
72	/* zero out flags, and disable interrupts */
73	pushq $0
74	popfq
75
76	/* Save SME active flag */
77	movq	%r8, %r12
78
79	/*
80	 * get physical address of control page now
81	 * this is impossible after page table switch
82	 */
83	movq	PTR(PA_CONTROL_PAGE)(%rsi), %r8
84
85	/* get physical address of page table now too */
86	movq	PTR(PA_TABLE_PAGE)(%rsi), %r9
87
88	/* get physical address of swap page now */
89	movq	PTR(PA_SWAP_PAGE)(%rsi), %r10
90
91	/* save some information for jumping back */
92	movq	%r9, CP_PA_TABLE_PAGE(%r11)
93	movq	%r10, CP_PA_SWAP_PAGE(%r11)
94	movq	%rdi, CP_PA_BACKUP_PAGES_MAP(%r11)
95
96	/* Switch to the identity mapped page tables */
97	movq	%r9, %cr3
98
99	/* setup a new stack at the end of the physical control page */
100	lea	PAGE_SIZE(%r8), %rsp
101
102	/* jump to identity mapped page */
103	addq	$(identity_mapped - relocate_kernel), %r8
104	pushq	%r8
105	ret
106
107identity_mapped:
108	/* set return address to 0 if not preserving context */
109	pushq	$0
110	/* store the start address on the stack */
111	pushq   %rdx
112
113	/*
114	 * Set cr0 to a known state:
115	 *  - Paging enabled
116	 *  - Alignment check disabled
117	 *  - Write protect disabled
118	 *  - No task switch
119	 *  - Don't do FP software emulation.
120	 *  - Proctected mode enabled
121	 */
122	movq	%cr0, %rax
123	andq	$~(X86_CR0_AM | X86_CR0_WP | X86_CR0_TS | X86_CR0_EM), %rax
124	orl	$(X86_CR0_PG | X86_CR0_PE), %eax
125	movq	%rax, %cr0
126
127	/*
128	 * Set cr4 to a known state:
129	 *  - physical address extension enabled
130	 *  - 5-level paging, if it was enabled before
131	 */
132	movl	$X86_CR4_PAE, %eax
133	testq	$X86_CR4_LA57, %r13
134	jz	1f
135	orl	$X86_CR4_LA57, %eax
1361:
137	movq	%rax, %cr4
138
139	jmp 1f
1401:
141
142	/* Flush the TLB (needed?) */
143	movq	%r9, %cr3
144
145	/*
146	 * If SME is active, there could be old encrypted cache line
147	 * entries that will conflict with the now unencrypted memory
148	 * used by kexec. Flush the caches before copying the kernel.
149	 */
150	testq	%r12, %r12
151	jz 1f
152	wbinvd
1531:
154
155	movq	%rcx, %r11
156	call	swap_pages
157
158	/*
159	 * To be certain of avoiding problems with self-modifying code
160	 * I need to execute a serializing instruction here.
161	 * So I flush the TLB by reloading %cr3 here, it's handy,
162	 * and not processor dependent.
163	 */
164	movq	%cr3, %rax
165	movq	%rax, %cr3
166
167	/*
168	 * set all of the registers to known values
169	 * leave %rsp alone
170	 */
171
172	testq	%r11, %r11
173	jnz 1f
174	xorl	%eax, %eax
175	xorl	%ebx, %ebx
176	xorl    %ecx, %ecx
177	xorl    %edx, %edx
178	xorl    %esi, %esi
179	xorl    %edi, %edi
180	xorl    %ebp, %ebp
181	xorl	%r8d, %r8d
182	xorl	%r9d, %r9d
183	xorl	%r10d, %r10d
184	xorl	%r11d, %r11d
185	xorl	%r12d, %r12d
186	xorl	%r13d, %r13d
187	xorl	%r14d, %r14d
188	xorl	%r15d, %r15d
189
190	ret
191
1921:
193	popq	%rdx
194	leaq	PAGE_SIZE(%r10), %rsp
195	call	*%rdx
196
197	/* get the re-entry point of the peer system */
198	movq	0(%rsp), %rbp
199	call	1f
2001:
201	popq	%r8
202	subq	$(1b - relocate_kernel), %r8
203	movq	CP_PA_SWAP_PAGE(%r8), %r10
204	movq	CP_PA_BACKUP_PAGES_MAP(%r8), %rdi
205	movq	CP_PA_TABLE_PAGE(%r8), %rax
206	movq	%rax, %cr3
207	lea	PAGE_SIZE(%r8), %rsp
208	call	swap_pages
209	movq	$virtual_mapped, %rax
210	pushq	%rax
211	ret
212
213virtual_mapped:
214	movq	RSP(%r8), %rsp
215	movq	CR4(%r8), %rax
216	movq	%rax, %cr4
217	movq	CR3(%r8), %rax
218	movq	CR0(%r8), %r8
219	movq	%rax, %cr3
220	movq	%r8, %cr0
221	movq	%rbp, %rax
222
223	popf
224	popq	%r15
225	popq	%r14
226	popq	%r13
227	popq	%r12
228	popq	%rbp
229	popq	%rbx
230	ret
231
232	/* Do the copies */
233swap_pages:
234	movq	%rdi, %rcx 	/* Put the page_list in %rcx */
235	xorl	%edi, %edi
236	xorl	%esi, %esi
237	jmp	1f
238
2390:	/* top, read another word for the indirection page */
240
241	movq	(%rbx), %rcx
242	addq	$8,	%rbx
2431:
244	testb	$0x1,	%cl   /* is it a destination page? */
245	jz	2f
246	movq	%rcx,	%rdi
247	andq	$0xfffffffffffff000, %rdi
248	jmp	0b
2492:
250	testb	$0x2,	%cl   /* is it an indirection page? */
251	jz	2f
252	movq	%rcx,   %rbx
253	andq	$0xfffffffffffff000, %rbx
254	jmp	0b
2552:
256	testb	$0x4,	%cl   /* is it the done indicator? */
257	jz	2f
258	jmp	3f
2592:
260	testb	$0x8,	%cl   /* is it the source indicator? */
261	jz	0b	      /* Ignore it otherwise */
262	movq	%rcx,   %rsi  /* For ever source page do a copy */
263	andq	$0xfffffffffffff000, %rsi
264
265	movq	%rdi, %rdx
266	movq	%rsi, %rax
267
268	movq	%r10, %rdi
269	movl	$512, %ecx
270	rep ; movsq
271
272	movq	%rax, %rdi
273	movq	%rdx, %rsi
274	movl	$512, %ecx
275	rep ; movsq
276
277	movq	%rdx, %rdi
278	movq	%r10, %rsi
279	movl	$512, %ecx
280	rep ; movsq
281
282	lea	PAGE_SIZE(%rax), %rsi
283	jmp	0b
2843:
285	ret
286
287	.globl kexec_control_code_size
288.set kexec_control_code_size, . - relocate_kernel
289