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#include <asm/nospec-branch.h>
13#include <asm/unwind_hints.h>
14
15/*
16 * Must be relocatable PIC code callable as a C function, in particular
17 * there must be a plain RET and not jump to return thunk.
18 */
19
20#define PTR(x) (x << 3)
21#define PAGE_ATTR (_PAGE_PRESENT | _PAGE_RW | _PAGE_ACCESSED | _PAGE_DIRTY)
22
23/*
24 * control_page + KEXEC_CONTROL_CODE_MAX_SIZE
25 * ~ control_page + PAGE_SIZE are used as data storage and stack for
26 * jumping back
27 */
28#define DATA(offset)		(KEXEC_CONTROL_CODE_MAX_SIZE+(offset))
29
30/* Minimal CPU state */
31#define RSP			DATA(0x0)
32#define CR0			DATA(0x8)
33#define CR3			DATA(0x10)
34#define CR4			DATA(0x18)
35
36/* other data */
37#define CP_PA_TABLE_PAGE	DATA(0x20)
38#define CP_PA_SWAP_PAGE		DATA(0x28)
39#define CP_PA_BACKUP_PAGES_MAP	DATA(0x30)
40
41	.text
42	.align PAGE_SIZE
43	.code64
44SYM_CODE_START_NOALIGN(relocate_range)
45SYM_CODE_START_NOALIGN(relocate_kernel)
46	UNWIND_HINT_END_OF_STACK
47	ANNOTATE_NOENDBR
48	/*
49	 * %rdi indirection_page
50	 * %rsi page_list
51	 * %rdx start address
52	 * %rcx preserve_context
53	 * %r8  host_mem_enc_active
54	 */
55
56	/* Save the CPU context, used for jumping back */
57	pushq %rbx
58	pushq %rbp
59	pushq %r12
60	pushq %r13
61	pushq %r14
62	pushq %r15
63	pushf
64
65	movq	PTR(VA_CONTROL_PAGE)(%rsi), %r11
66	movq	%rsp, RSP(%r11)
67	movq	%cr0, %rax
68	movq	%rax, CR0(%r11)
69	movq	%cr3, %rax
70	movq	%rax, CR3(%r11)
71	movq	%cr4, %rax
72	movq	%rax, CR4(%r11)
73
74	/* Save CR4. Required to enable the right paging mode later. */
75	movq	%rax, %r13
76
77	/* zero out flags, and disable interrupts */
78	pushq $0
79	popfq
80
81	/* Save SME active flag */
82	movq	%r8, %r12
83
84	/*
85	 * get physical address of control page now
86	 * this is impossible after page table switch
87	 */
88	movq	PTR(PA_CONTROL_PAGE)(%rsi), %r8
89
90	/* get physical address of page table now too */
91	movq	PTR(PA_TABLE_PAGE)(%rsi), %r9
92
93	/* get physical address of swap page now */
94	movq	PTR(PA_SWAP_PAGE)(%rsi), %r10
95
96	/* save some information for jumping back */
97	movq	%r9, CP_PA_TABLE_PAGE(%r11)
98	movq	%r10, CP_PA_SWAP_PAGE(%r11)
99	movq	%rdi, CP_PA_BACKUP_PAGES_MAP(%r11)
100
101	/* Switch to the identity mapped page tables */
102	movq	%r9, %cr3
103
104	/* setup a new stack at the end of the physical control page */
105	lea	PAGE_SIZE(%r8), %rsp
106
107	/* jump to identity mapped page */
108	addq	$(identity_mapped - relocate_kernel), %r8
109	pushq	%r8
110	ANNOTATE_UNRET_SAFE
111	ret
112	int3
113SYM_CODE_END(relocate_kernel)
114
115SYM_CODE_START_LOCAL_NOALIGN(identity_mapped)
116	UNWIND_HINT_END_OF_STACK
117	/* set return address to 0 if not preserving context */
118	pushq	$0
119	/* store the start address on the stack */
120	pushq   %rdx
121
122	/*
123	 * Clear X86_CR4_CET (if it was set) such that we can clear CR0_WP
124	 * below.
125	 */
126	movq	%cr4, %rax
127	andq	$~(X86_CR4_CET), %rax
128	movq	%rax, %cr4
129
130	/*
131	 * Set cr0 to a known state:
132	 *  - Paging enabled
133	 *  - Alignment check disabled
134	 *  - Write protect disabled
135	 *  - No task switch
136	 *  - Don't do FP software emulation.
137	 *  - Protected mode enabled
138	 */
139	movq	%cr0, %rax
140	andq	$~(X86_CR0_AM | X86_CR0_WP | X86_CR0_TS | X86_CR0_EM), %rax
141	orl	$(X86_CR0_PG | X86_CR0_PE), %eax
142	movq	%rax, %cr0
143
144	/*
145	 * Set cr4 to a known state:
146	 *  - physical address extension enabled
147	 *  - 5-level paging, if it was enabled before
148	 */
149	movl	$X86_CR4_PAE, %eax
150	testq	$X86_CR4_LA57, %r13
151	jz	1f
152	orl	$X86_CR4_LA57, %eax
1531:
154	movq	%rax, %cr4
155
156	jmp 1f
1571:
158
159	/* Flush the TLB (needed?) */
160	movq	%r9, %cr3
161
162	/*
163	 * If SME is active, there could be old encrypted cache line
164	 * entries that will conflict with the now unencrypted memory
165	 * used by kexec. Flush the caches before copying the kernel.
166	 */
167	testq	%r12, %r12
168	jz 1f
169	wbinvd
1701:
171
172	movq	%rcx, %r11
173	call	swap_pages
174
175	/*
176	 * To be certain of avoiding problems with self-modifying code
177	 * I need to execute a serializing instruction here.
178	 * So I flush the TLB by reloading %cr3 here, it's handy,
179	 * and not processor dependent.
180	 */
181	movq	%cr3, %rax
182	movq	%rax, %cr3
183
184	/*
185	 * set all of the registers to known values
186	 * leave %rsp alone
187	 */
188
189	testq	%r11, %r11
190	jnz 1f
191	xorl	%eax, %eax
192	xorl	%ebx, %ebx
193	xorl    %ecx, %ecx
194	xorl    %edx, %edx
195	xorl    %esi, %esi
196	xorl    %edi, %edi
197	xorl    %ebp, %ebp
198	xorl	%r8d, %r8d
199	xorl	%r9d, %r9d
200	xorl	%r10d, %r10d
201	xorl	%r11d, %r11d
202	xorl	%r12d, %r12d
203	xorl	%r13d, %r13d
204	xorl	%r14d, %r14d
205	xorl	%r15d, %r15d
206
207	ANNOTATE_UNRET_SAFE
208	ret
209	int3
210
2111:
212	popq	%rdx
213	leaq	PAGE_SIZE(%r10), %rsp
214	ANNOTATE_RETPOLINE_SAFE
215	call	*%rdx
216
217	/* get the re-entry point of the peer system */
218	movq	0(%rsp), %rbp
219	leaq	relocate_kernel(%rip), %r8
220	movq	CP_PA_SWAP_PAGE(%r8), %r10
221	movq	CP_PA_BACKUP_PAGES_MAP(%r8), %rdi
222	movq	CP_PA_TABLE_PAGE(%r8), %rax
223	movq	%rax, %cr3
224	lea	PAGE_SIZE(%r8), %rsp
225	call	swap_pages
226	movq	$virtual_mapped, %rax
227	pushq	%rax
228	ANNOTATE_UNRET_SAFE
229	ret
230	int3
231SYM_CODE_END(identity_mapped)
232
233SYM_CODE_START_LOCAL_NOALIGN(virtual_mapped)
234	UNWIND_HINT_END_OF_STACK
235	ANNOTATE_NOENDBR // RET target, above
236	movq	RSP(%r8), %rsp
237	movq	CR4(%r8), %rax
238	movq	%rax, %cr4
239	movq	CR3(%r8), %rax
240	movq	CR0(%r8), %r8
241	movq	%rax, %cr3
242	movq	%r8, %cr0
243	movq	%rbp, %rax
244
245	popf
246	popq	%r15
247	popq	%r14
248	popq	%r13
249	popq	%r12
250	popq	%rbp
251	popq	%rbx
252	ANNOTATE_UNRET_SAFE
253	ret
254	int3
255SYM_CODE_END(virtual_mapped)
256
257	/* Do the copies */
258SYM_CODE_START_LOCAL_NOALIGN(swap_pages)
259	UNWIND_HINT_END_OF_STACK
260	movq	%rdi, %rcx	/* Put the page_list in %rcx */
261	xorl	%edi, %edi
262	xorl	%esi, %esi
263	jmp	1f
264
2650:	/* top, read another word for the indirection page */
266
267	movq	(%rbx), %rcx
268	addq	$8,	%rbx
2691:
270	testb	$0x1,	%cl   /* is it a destination page? */
271	jz	2f
272	movq	%rcx,	%rdi
273	andq	$0xfffffffffffff000, %rdi
274	jmp	0b
2752:
276	testb	$0x2,	%cl   /* is it an indirection page? */
277	jz	2f
278	movq	%rcx,   %rbx
279	andq	$0xfffffffffffff000, %rbx
280	jmp	0b
2812:
282	testb	$0x4,	%cl   /* is it the done indicator? */
283	jz	2f
284	jmp	3f
2852:
286	testb	$0x8,	%cl   /* is it the source indicator? */
287	jz	0b	      /* Ignore it otherwise */
288	movq	%rcx,   %rsi  /* For ever source page do a copy */
289	andq	$0xfffffffffffff000, %rsi
290
291	movq	%rdi, %rdx
292	movq	%rsi, %rax
293
294	movq	%r10, %rdi
295	movl	$512, %ecx
296	rep ; movsq
297
298	movq	%rax, %rdi
299	movq	%rdx, %rsi
300	movl	$512, %ecx
301	rep ; movsq
302
303	movq	%rdx, %rdi
304	movq	%r10, %rsi
305	movl	$512, %ecx
306	rep ; movsq
307
308	lea	PAGE_SIZE(%rax), %rsi
309	jmp	0b
3103:
311	ANNOTATE_UNRET_SAFE
312	ret
313	int3
314SYM_CODE_END(swap_pages)
315
316	.skip KEXEC_CONTROL_CODE_MAX_SIZE - (. - relocate_kernel), 0xcc
317SYM_CODE_END(relocate_range);
318