1/*
2 * relocate_kernel.S - put the kernel image in place to boot
3 * Copyright (C) 2002-2005 Eric Biederman  <ebiederm@xmission.com>
4 *
5 * This source code is licensed under the GNU General Public License,
6 * Version 2.  See the file COPYING for more details.
7 */
8
9#include <linux/linkage.h>
10#include <asm/page_types.h>
11#include <asm/kexec.h>
12#include <asm/processor-flags.h>
13#include <asm/pgtable_types.h>
14
15/*
16 * Must be relocatable PIC code callable as a C function
17 */
18
19#define PTR(x) (x << 3)
20#define PAGE_ATTR (_PAGE_PRESENT | _PAGE_RW | _PAGE_ACCESSED | _PAGE_DIRTY)
21
22/*
23 * control_page + KEXEC_CONTROL_CODE_MAX_SIZE
24 * ~ control_page + PAGE_SIZE are used as data storage and stack for
25 * jumping back
26 */
27#define DATA(offset)		(KEXEC_CONTROL_CODE_MAX_SIZE+(offset))
28
29/* Minimal CPU state */
30#define RSP			DATA(0x0)
31#define CR0			DATA(0x8)
32#define CR3			DATA(0x10)
33#define CR4			DATA(0x18)
34
35/* other data */
36#define CP_PA_TABLE_PAGE	DATA(0x20)
37#define CP_PA_SWAP_PAGE		DATA(0x28)
38#define CP_PA_BACKUP_PAGES_MAP	DATA(0x30)
39
40	.text
41	.align PAGE_SIZE
42	.code64
43	.globl relocate_kernel
44relocate_kernel:
45	/*
46	 * %rdi indirection_page
47	 * %rsi page_list
48	 * %rdx start address
49	 * %rcx preserve_context
50	 * %r8  sme_active
51	 */
52
53	/* Save the CPU context, used for jumping back */
54	pushq %rbx
55	pushq %rbp
56	pushq %r12
57	pushq %r13
58	pushq %r14
59	pushq %r15
60	pushf
61
62	movq	PTR(VA_CONTROL_PAGE)(%rsi), %r11
63	movq	%rsp, RSP(%r11)
64	movq	%cr0, %rax
65	movq	%rax, CR0(%r11)
66	movq	%cr3, %rax
67	movq	%rax, CR3(%r11)
68	movq	%cr4, %rax
69	movq	%rax, CR4(%r11)
70
71	/* zero out flags, and disable interrupts */
72	pushq $0
73	popfq
74
75	/* Save SME active flag */
76	movq	%r8, %r12
77
78	/*
79	 * get physical address of control page now
80	 * this is impossible after page table switch
81	 */
82	movq	PTR(PA_CONTROL_PAGE)(%rsi), %r8
83
84	/* get physical address of page table now too */
85	movq	PTR(PA_TABLE_PAGE)(%rsi), %r9
86
87	/* get physical address of swap page now */
88	movq	PTR(PA_SWAP_PAGE)(%rsi), %r10
89
90	/* save some information for jumping back */
91	movq	%r9, CP_PA_TABLE_PAGE(%r11)
92	movq	%r10, CP_PA_SWAP_PAGE(%r11)
93	movq	%rdi, CP_PA_BACKUP_PAGES_MAP(%r11)
94
95	/* Switch to the identity mapped page tables */
96	movq	%r9, %cr3
97
98	/* setup a new stack at the end of the physical control page */
99	lea	PAGE_SIZE(%r8), %rsp
100
101	/* jump to identity mapped page */
102	addq	$(identity_mapped - relocate_kernel), %r8
103	pushq	%r8
104	ret
105
106identity_mapped:
107	/* set return address to 0 if not preserving context */
108	pushq	$0
109	/* store the start address on the stack */
110	pushq   %rdx
111
112	/*
113	 * Set cr0 to a known state:
114	 *  - Paging enabled
115	 *  - Alignment check disabled
116	 *  - Write protect disabled
117	 *  - No task switch
118	 *  - Don't do FP software emulation.
119	 *  - Proctected mode enabled
120	 */
121	movq	%cr0, %rax
122	andq	$~(X86_CR0_AM | X86_CR0_WP | X86_CR0_TS | X86_CR0_EM), %rax
123	orl	$(X86_CR0_PG | X86_CR0_PE), %eax
124	movq	%rax, %cr0
125
126	/*
127	 * Set cr4 to a known state:
128	 *  - physical address extension enabled
129	 */
130	movl	$X86_CR4_PAE, %eax
131	movq	%rax, %cr4
132
133	jmp 1f
1341:
135
136	/* Flush the TLB (needed?) */
137	movq	%r9, %cr3
138
139	/*
140	 * If SME is active, there could be old encrypted cache line
141	 * entries that will conflict with the now unencrypted memory
142	 * used by kexec. Flush the caches before copying the kernel.
143	 */
144	testq	%r12, %r12
145	jz 1f
146	wbinvd
1471:
148
149	movq	%rcx, %r11
150	call	swap_pages
151
152	/*
153	 * To be certain of avoiding problems with self-modifying code
154	 * I need to execute a serializing instruction here.
155	 * So I flush the TLB by reloading %cr3 here, it's handy,
156	 * and not processor dependent.
157	 */
158	movq	%cr3, %rax
159	movq	%rax, %cr3
160
161	/*
162	 * set all of the registers to known values
163	 * leave %rsp alone
164	 */
165
166	testq	%r11, %r11
167	jnz 1f
168	xorl	%eax, %eax
169	xorl	%ebx, %ebx
170	xorl    %ecx, %ecx
171	xorl    %edx, %edx
172	xorl    %esi, %esi
173	xorl    %edi, %edi
174	xorl    %ebp, %ebp
175	xorl	%r8d, %r8d
176	xorl	%r9d, %r9d
177	xorl	%r10d, %r10d
178	xorl	%r11d, %r11d
179	xorl	%r12d, %r12d
180	xorl	%r13d, %r13d
181	xorl	%r14d, %r14d
182	xorl	%r15d, %r15d
183
184	ret
185
1861:
187	popq	%rdx
188	leaq	PAGE_SIZE(%r10), %rsp
189	call	*%rdx
190
191	/* get the re-entry point of the peer system */
192	movq	0(%rsp), %rbp
193	call	1f
1941:
195	popq	%r8
196	subq	$(1b - relocate_kernel), %r8
197	movq	CP_PA_SWAP_PAGE(%r8), %r10
198	movq	CP_PA_BACKUP_PAGES_MAP(%r8), %rdi
199	movq	CP_PA_TABLE_PAGE(%r8), %rax
200	movq	%rax, %cr3
201	lea	PAGE_SIZE(%r8), %rsp
202	call	swap_pages
203	movq	$virtual_mapped, %rax
204	pushq	%rax
205	ret
206
207virtual_mapped:
208	movq	RSP(%r8), %rsp
209	movq	CR4(%r8), %rax
210	movq	%rax, %cr4
211	movq	CR3(%r8), %rax
212	movq	CR0(%r8), %r8
213	movq	%rax, %cr3
214	movq	%r8, %cr0
215	movq	%rbp, %rax
216
217	popf
218	popq	%r15
219	popq	%r14
220	popq	%r13
221	popq	%r12
222	popq	%rbp
223	popq	%rbx
224	ret
225
226	/* Do the copies */
227swap_pages:
228	movq	%rdi, %rcx 	/* Put the page_list in %rcx */
229	xorl	%edi, %edi
230	xorl	%esi, %esi
231	jmp	1f
232
2330:	/* top, read another word for the indirection page */
234
235	movq	(%rbx), %rcx
236	addq	$8,	%rbx
2371:
238	testb	$0x1,	%cl   /* is it a destination page? */
239	jz	2f
240	movq	%rcx,	%rdi
241	andq	$0xfffffffffffff000, %rdi
242	jmp	0b
2432:
244	testb	$0x2,	%cl   /* is it an indirection page? */
245	jz	2f
246	movq	%rcx,   %rbx
247	andq	$0xfffffffffffff000, %rbx
248	jmp	0b
2492:
250	testb	$0x4,	%cl   /* is it the done indicator? */
251	jz	2f
252	jmp	3f
2532:
254	testb	$0x8,	%cl   /* is it the source indicator? */
255	jz	0b	      /* Ignore it otherwise */
256	movq	%rcx,   %rsi  /* For ever source page do a copy */
257	andq	$0xfffffffffffff000, %rsi
258
259	movq	%rdi, %rdx
260	movq	%rsi, %rax
261
262	movq	%r10, %rdi
263	movl	$512, %ecx
264	rep ; movsq
265
266	movq	%rax, %rdi
267	movq	%rdx, %rsi
268	movl	$512, %ecx
269	rep ; movsq
270
271	movq	%rdx, %rdi
272	movq	%r10, %rsi
273	movl	$512, %ecx
274	rep ; movsq
275
276	lea	PAGE_SIZE(%rax), %rsi
277	jmp	0b
2783:
279	ret
280
281	.globl kexec_control_code_size
282.set kexec_control_code_size, . - relocate_kernel
283