1 /* SPDX-License-Identifier: GPL-2.0-only */
3 * relocate_kernel.S - put the kernel image in place to boot
4 * Copyright (C) 2002-2005 Eric Biederman <ebiederm@xmission.com>
7 #include <linux/linkage.h>
8 #include <asm/page_types.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>
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.
20 #define PTR(x) (x << 3)
21 #define PAGE_ATTR (_PAGE_PRESENT | _PAGE_RW | _PAGE_ACCESSED | _PAGE_DIRTY)
24 * control_page + KEXEC_CONTROL_CODE_MAX_SIZE
25 * ~ control_page + PAGE_SIZE are used as data storage and stack for
28 #define DATA(offset) (KEXEC_CONTROL_CODE_MAX_SIZE+(offset))
30 /* Minimal CPU state */
33 #define CR3 DATA(0x10)
34 #define CR4 DATA(0x18)
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)
44 SYM_CODE_START_NOALIGN(relocate_kernel)
48 * %rdi indirection_page
51 * %rcx preserve_context
52 * %r8 host_mem_enc_active
55 /* Save the CPU context, used for jumping back */
64 movq PTR(VA_CONTROL_PAGE)(%rsi), %r11
73 /* Save CR4. Required to enable the right paging mode later. */
76 /* zero out flags, and disable interrupts */
80 /* Save SME active flag */
84 * get physical address of control page now
85 * this is impossible after page table switch
87 movq PTR(PA_CONTROL_PAGE)(%rsi), %r8
89 /* get physical address of page table now too */
90 movq PTR(PA_TABLE_PAGE)(%rsi), %r9
92 /* get physical address of swap page now */
93 movq PTR(PA_SWAP_PAGE)(%rsi), %r10
95 /* save some information for jumping back */
96 movq %r9, CP_PA_TABLE_PAGE(%r11)
97 movq %r10, CP_PA_SWAP_PAGE(%r11)
98 movq %rdi, CP_PA_BACKUP_PAGES_MAP(%r11)
100 /* Switch to the identity mapped page tables */
103 /* setup a new stack at the end of the physical control page */
104 lea PAGE_SIZE(%r8), %rsp
106 /* jump to identity mapped page */
107 addq $(identity_mapped - relocate_kernel), %r8
112 SYM_CODE_END(relocate_kernel)
114 SYM_CODE_START_LOCAL_NOALIGN(identity_mapped)
116 /* set return address to 0 if not preserving context */
118 /* store the start address on the stack */
122 * Clear X86_CR4_CET (if it was set) such that we can clear CR0_WP
126 andq $~(X86_CR4_CET), %rax
130 * Set cr0 to a known state:
132 * - Alignment check disabled
133 * - Write protect disabled
135 * - Don't do FP software emulation.
136 * - Protected mode enabled
139 andq $~(X86_CR0_AM | X86_CR0_WP | X86_CR0_TS | X86_CR0_EM), %rax
140 orl $(X86_CR0_PG | X86_CR0_PE), %eax
144 * Set cr4 to a known state:
145 * - physical address extension enabled
146 * - 5-level paging, if it was enabled before
148 movl $X86_CR4_PAE, %eax
149 testq $X86_CR4_LA57, %r13
151 orl $X86_CR4_LA57, %eax
158 /* Flush the TLB (needed?) */
162 * If SME is active, there could be old encrypted cache line
163 * entries that will conflict with the now unencrypted memory
164 * used by kexec. Flush the caches before copying the kernel.
175 * To be certain of avoiding problems with self-modifying code
176 * I need to execute a serializing instruction here.
177 * So I flush the TLB by reloading %cr3 here, it's handy,
178 * and not processor dependent.
184 * set all of the registers to known values
212 leaq PAGE_SIZE(%r10), %rsp
213 ANNOTATE_RETPOLINE_SAFE
216 /* get the re-entry point of the peer system */
218 leaq relocate_kernel(%rip), %r8
219 movq CP_PA_SWAP_PAGE(%r8), %r10
220 movq CP_PA_BACKUP_PAGES_MAP(%r8), %rdi
221 movq CP_PA_TABLE_PAGE(%r8), %rax
223 lea PAGE_SIZE(%r8), %rsp
225 movq $virtual_mapped, %rax
230 SYM_CODE_END(identity_mapped)
232 SYM_CODE_START_LOCAL_NOALIGN(virtual_mapped)
234 ANNOTATE_NOENDBR // RET target, above
254 SYM_CODE_END(virtual_mapped)
257 SYM_CODE_START_LOCAL_NOALIGN(swap_pages)
259 movq %rdi, %rcx /* Put the page_list in %rcx */
264 0: /* top, read another word for the indirection page */
269 testb $0x1, %cl /* is it a destination page? */
272 andq $0xfffffffffffff000, %rdi
275 testb $0x2, %cl /* is it an indirection page? */
278 andq $0xfffffffffffff000, %rbx
281 testb $0x4, %cl /* is it the done indicator? */
285 testb $0x8, %cl /* is it the source indicator? */
286 jz 0b /* Ignore it otherwise */
287 movq %rcx, %rsi /* For ever source page do a copy */
288 andq $0xfffffffffffff000, %rsi
307 lea PAGE_SIZE(%rax), %rsi
313 SYM_CODE_END(swap_pages)
315 .globl kexec_control_code_size
316 .set kexec_control_code_size, . - relocate_kernel