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	/* Save CR4. Required to enable the right paging mode later. */
72	movq	%rax, %r13
73
74	/* zero out flags, and disable interrupts */
75	pushq $0
76	popfq
77
78	/* Save SME active flag */
79	movq	%r8, %r12
80
81	/*
82	 * get physical address of control page now
83	 * this is impossible after page table switch
84	 */
85	movq	PTR(PA_CONTROL_PAGE)(%rsi), %r8
86
87	/* get physical address of page table now too */
88	movq	PTR(PA_TABLE_PAGE)(%rsi), %r9
89
90	/* get physical address of swap page now */
91	movq	PTR(PA_SWAP_PAGE)(%rsi), %r10
92
93	/* save some information for jumping back */
94	movq	%r9, CP_PA_TABLE_PAGE(%r11)
95	movq	%r10, CP_PA_SWAP_PAGE(%r11)
96	movq	%rdi, CP_PA_BACKUP_PAGES_MAP(%r11)
97
98	/* Switch to the identity mapped page tables */
99	movq	%r9, %cr3
100
101	/* setup a new stack at the end of the physical control page */
102	lea	PAGE_SIZE(%r8), %rsp
103
104	/* jump to identity mapped page */
105	addq	$(identity_mapped - relocate_kernel), %r8
106	pushq	%r8
107	ret
108
109identity_mapped:
110	/* set return address to 0 if not preserving context */
111	pushq	$0
112	/* store the start address on the stack */
113	pushq   %rdx
114
115	/*
116	 * Set cr0 to a known state:
117	 *  - Paging enabled
118	 *  - Alignment check disabled
119	 *  - Write protect disabled
120	 *  - No task switch
121	 *  - Don't do FP software emulation.
122	 *  - Proctected mode enabled
123	 */
124	movq	%cr0, %rax
125	andq	$~(X86_CR0_AM | X86_CR0_WP | X86_CR0_TS | X86_CR0_EM), %rax
126	orl	$(X86_CR0_PG | X86_CR0_PE), %eax
127	movq	%rax, %cr0
128
129	/*
130	 * Set cr4 to a known state:
131	 *  - physical address extension enabled
132	 *  - 5-level paging, if it was enabled before
133	 */
134	movl	$X86_CR4_PAE, %eax
135	testq	$X86_CR4_LA57, %r13
136	jz	1f
137	orl	$X86_CR4_LA57, %eax
1381:
139	movq	%rax, %cr4
140
141	jmp 1f
1421:
143
144	/* Flush the TLB (needed?) */
145	movq	%r9, %cr3
146
147	/*
148	 * If SME is active, there could be old encrypted cache line
149	 * entries that will conflict with the now unencrypted memory
150	 * used by kexec. Flush the caches before copying the kernel.
151	 */
152	testq	%r12, %r12
153	jz 1f
154	wbinvd
1551:
156
157	movq	%rcx, %r11
158	call	swap_pages
159
160	/*
161	 * To be certain of avoiding problems with self-modifying code
162	 * I need to execute a serializing instruction here.
163	 * So I flush the TLB by reloading %cr3 here, it's handy,
164	 * and not processor dependent.
165	 */
166	movq	%cr3, %rax
167	movq	%rax, %cr3
168
169	/*
170	 * set all of the registers to known values
171	 * leave %rsp alone
172	 */
173
174	testq	%r11, %r11
175	jnz 1f
176	xorl	%eax, %eax
177	xorl	%ebx, %ebx
178	xorl    %ecx, %ecx
179	xorl    %edx, %edx
180	xorl    %esi, %esi
181	xorl    %edi, %edi
182	xorl    %ebp, %ebp
183	xorl	%r8d, %r8d
184	xorl	%r9d, %r9d
185	xorl	%r10d, %r10d
186	xorl	%r11d, %r11d
187	xorl	%r12d, %r12d
188	xorl	%r13d, %r13d
189	xorl	%r14d, %r14d
190	xorl	%r15d, %r15d
191
192	ret
193
1941:
195	popq	%rdx
196	leaq	PAGE_SIZE(%r10), %rsp
197	call	*%rdx
198
199	/* get the re-entry point of the peer system */
200	movq	0(%rsp), %rbp
201	call	1f
2021:
203	popq	%r8
204	subq	$(1b - relocate_kernel), %r8
205	movq	CP_PA_SWAP_PAGE(%r8), %r10
206	movq	CP_PA_BACKUP_PAGES_MAP(%r8), %rdi
207	movq	CP_PA_TABLE_PAGE(%r8), %rax
208	movq	%rax, %cr3
209	lea	PAGE_SIZE(%r8), %rsp
210	call	swap_pages
211	movq	$virtual_mapped, %rax
212	pushq	%rax
213	ret
214
215virtual_mapped:
216	movq	RSP(%r8), %rsp
217	movq	CR4(%r8), %rax
218	movq	%rax, %cr4
219	movq	CR3(%r8), %rax
220	movq	CR0(%r8), %r8
221	movq	%rax, %cr3
222	movq	%r8, %cr0
223	movq	%rbp, %rax
224
225	popf
226	popq	%r15
227	popq	%r14
228	popq	%r13
229	popq	%r12
230	popq	%rbp
231	popq	%rbx
232	ret
233
234	/* Do the copies */
235swap_pages:
236	movq	%rdi, %rcx 	/* Put the page_list in %rcx */
237	xorl	%edi, %edi
238	xorl	%esi, %esi
239	jmp	1f
240
2410:	/* top, read another word for the indirection page */
242
243	movq	(%rbx), %rcx
244	addq	$8,	%rbx
2451:
246	testb	$0x1,	%cl   /* is it a destination page? */
247	jz	2f
248	movq	%rcx,	%rdi
249	andq	$0xfffffffffffff000, %rdi
250	jmp	0b
2512:
252	testb	$0x2,	%cl   /* is it an indirection page? */
253	jz	2f
254	movq	%rcx,   %rbx
255	andq	$0xfffffffffffff000, %rbx
256	jmp	0b
2572:
258	testb	$0x4,	%cl   /* is it the done indicator? */
259	jz	2f
260	jmp	3f
2612:
262	testb	$0x8,	%cl   /* is it the source indicator? */
263	jz	0b	      /* Ignore it otherwise */
264	movq	%rcx,   %rsi  /* For ever source page do a copy */
265	andq	$0xfffffffffffff000, %rsi
266
267	movq	%rdi, %rdx
268	movq	%rsi, %rax
269
270	movq	%r10, %rdi
271	movl	$512, %ecx
272	rep ; movsq
273
274	movq	%rax, %rdi
275	movq	%rdx, %rsi
276	movl	$512, %ecx
277	rep ; movsq
278
279	movq	%rdx, %rdi
280	movq	%r10, %rsi
281	movl	$512, %ecx
282	rep ; movsq
283
284	lea	PAGE_SIZE(%rax), %rsi
285	jmp	0b
2863:
287	ret
288
289	.globl kexec_control_code_size
290.set kexec_control_code_size, . - relocate_kernel
291