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/* SPDX-License-Identifier: GPL-2.0-only */
/*
* relocate_kernel.S - put the kernel image in place to boot
* Copyright (C) 2002-2005 Eric Biederman <ebiederm@xmission.com>
*/
#include <linux/linkage.h>
#include <linux/stringify.h>
#include <asm/alternative.h>
#include <asm/page_types.h>
#include <asm/kexec.h>
#include <asm/processor-flags.h>
#include <asm/pgtable_types.h>
#include <asm/nospec-branch.h>
#include <asm/unwind_hints.h>
/*
* Must be relocatable PIC code callable as a C function, in particular
* there must be a plain RET and not jump to return thunk.
*/
#define PTR(x) (x << 3)
#define PAGE_ATTR (_PAGE_PRESENT | _PAGE_RW | _PAGE_ACCESSED | _PAGE_DIRTY)
/*
* control_page + KEXEC_CONTROL_CODE_MAX_SIZE
* ~ control_page + PAGE_SIZE are used as data storage and stack for
* jumping back
*/
#define DATA(offset) (KEXEC_CONTROL_CODE_MAX_SIZE+(offset))
/* Minimal CPU state */
#define RSP DATA(0x0)
#define CR0 DATA(0x8)
#define CR3 DATA(0x10)
#define CR4 DATA(0x18)
/* other data */
#define CP_PA_TABLE_PAGE DATA(0x20)
#define CP_PA_SWAP_PAGE DATA(0x28)
#define CP_PA_BACKUP_PAGES_MAP DATA(0x30)
.text
.align PAGE_SIZE
.code64
SYM_CODE_START_NOALIGN(relocate_range)
SYM_CODE_START_NOALIGN(relocate_kernel)
UNWIND_HINT_END_OF_STACK
ANNOTATE_NOENDBR
/*
* %rdi indirection_page
* %rsi page_list
* %rdx start address
* %rcx preserve_context
* %r8 host_mem_enc_active
*/
/* Save the CPU context, used for jumping back */
pushq %rbx
pushq %rbp
pushq %r12
pushq %r13
pushq %r14
pushq %r15
pushf
movq PTR(VA_CONTROL_PAGE)(%rsi), %r11
movq %rsp, RSP(%r11)
movq %cr0, %rax
movq %rax, CR0(%r11)
movq %cr3, %rax
movq %rax, CR3(%r11)
movq %cr4, %rax
movq %rax, CR4(%r11)
/* Save CR4. Required to enable the right paging mode later. */
movq %rax, %r13
/* zero out flags, and disable interrupts */
pushq $0
popfq
/* Save SME active flag */
movq %r8, %r12
/*
* get physical address of control page now
* this is impossible after page table switch
*/
movq PTR(PA_CONTROL_PAGE)(%rsi), %r8
/* get physical address of page table now too */
movq PTR(PA_TABLE_PAGE)(%rsi), %r9
/* get physical address of swap page now */
movq PTR(PA_SWAP_PAGE)(%rsi), %r10
/* save some information for jumping back */
movq %r9, CP_PA_TABLE_PAGE(%r11)
movq %r10, CP_PA_SWAP_PAGE(%r11)
movq %rdi, CP_PA_BACKUP_PAGES_MAP(%r11)
/* Switch to the identity mapped page tables */
movq %r9, %cr3
/* setup a new stack at the end of the physical control page */
lea PAGE_SIZE(%r8), %rsp
/* jump to identity mapped page */
addq $(identity_mapped - relocate_kernel), %r8
pushq %r8
ANNOTATE_UNRET_SAFE
ret
int3
SYM_CODE_END(relocate_kernel)
SYM_CODE_START_LOCAL_NOALIGN(identity_mapped)
UNWIND_HINT_END_OF_STACK
/* set return address to 0 if not preserving context */
pushq $0
/* store the start address on the stack */
pushq %rdx
/*
* Clear X86_CR4_CET (if it was set) such that we can clear CR0_WP
* below.
*/
movq %cr4, %rax
andq $~(X86_CR4_CET), %rax
movq %rax, %cr4
/*
* Set cr0 to a known state:
* - Paging enabled
* - Alignment check disabled
* - Write protect disabled
* - No task switch
* - Don't do FP software emulation.
* - Protected mode enabled
*/
movq %cr0, %rax
andq $~(X86_CR0_AM | X86_CR0_WP | X86_CR0_TS | X86_CR0_EM), %rax
orl $(X86_CR0_PG | X86_CR0_PE), %eax
movq %rax, %cr0
/*
* Set cr4 to a known state:
* - physical address extension enabled
* - 5-level paging, if it was enabled before
* - Machine check exception on TDX guest, if it was enabled before.
* Clearing MCE might not be allowed in TDX guests, depending on setup.
*
* Use R13 that contains the original CR4 value, read in relocate_kernel().
* PAE is always set in the original CR4.
*/
andl $(X86_CR4_PAE | X86_CR4_LA57), %r13d
ALTERNATIVE "", __stringify(orl $X86_CR4_MCE, %r13d), X86_FEATURE_TDX_GUEST
movq %r13, %cr4
/* Flush the TLB (needed?) */
movq %r9, %cr3
/*
* If SME is active, there could be old encrypted cache line
* entries that will conflict with the now unencrypted memory
* used by kexec. Flush the caches before copying the kernel.
*/
testq %r12, %r12
jz .Lsme_off
wbinvd
.Lsme_off:
movq %rcx, %r11
call swap_pages
/*
* To be certain of avoiding problems with self-modifying code
* I need to execute a serializing instruction here.
* So I flush the TLB by reloading %cr3 here, it's handy,
* and not processor dependent.
*/
movq %cr3, %rax
movq %rax, %cr3
/*
* set all of the registers to known values
* leave %rsp alone
*/
testq %r11, %r11
jnz .Lrelocate
xorl %eax, %eax
xorl %ebx, %ebx
xorl %ecx, %ecx
xorl %edx, %edx
xorl %esi, %esi
xorl %edi, %edi
xorl %ebp, %ebp
xorl %r8d, %r8d
xorl %r9d, %r9d
xorl %r10d, %r10d
xorl %r11d, %r11d
xorl %r12d, %r12d
xorl %r13d, %r13d
xorl %r14d, %r14d
xorl %r15d, %r15d
ANNOTATE_UNRET_SAFE
ret
int3
.Lrelocate:
popq %rdx
leaq PAGE_SIZE(%r10), %rsp
ANNOTATE_RETPOLINE_SAFE
call *%rdx
/* get the re-entry point of the peer system */
movq 0(%rsp), %rbp
leaq relocate_kernel(%rip), %r8
movq CP_PA_SWAP_PAGE(%r8), %r10
movq CP_PA_BACKUP_PAGES_MAP(%r8), %rdi
movq CP_PA_TABLE_PAGE(%r8), %rax
movq %rax, %cr3
lea PAGE_SIZE(%r8), %rsp
call swap_pages
movq $virtual_mapped, %rax
pushq %rax
ANNOTATE_UNRET_SAFE
ret
int3
SYM_CODE_END(identity_mapped)
SYM_CODE_START_LOCAL_NOALIGN(virtual_mapped)
UNWIND_HINT_END_OF_STACK
ANNOTATE_NOENDBR // RET target, above
movq RSP(%r8), %rsp
movq CR4(%r8), %rax
movq %rax, %cr4
movq CR3(%r8), %rax
movq CR0(%r8), %r8
movq %rax, %cr3
movq %r8, %cr0
movq %rbp, %rax
popf
popq %r15
popq %r14
popq %r13
popq %r12
popq %rbp
popq %rbx
ANNOTATE_UNRET_SAFE
ret
int3
SYM_CODE_END(virtual_mapped)
/* Do the copies */
SYM_CODE_START_LOCAL_NOALIGN(swap_pages)
UNWIND_HINT_END_OF_STACK
movq %rdi, %rcx /* Put the page_list in %rcx */
xorl %edi, %edi
xorl %esi, %esi
jmp 1f
0: /* top, read another word for the indirection page */
movq (%rbx), %rcx
addq $8, %rbx
1:
testb $0x1, %cl /* is it a destination page? */
jz 2f
movq %rcx, %rdi
andq $0xfffffffffffff000, %rdi
jmp 0b
2:
testb $0x2, %cl /* is it an indirection page? */
jz 2f
movq %rcx, %rbx
andq $0xfffffffffffff000, %rbx
jmp 0b
2:
testb $0x4, %cl /* is it the done indicator? */
jz 2f
jmp 3f
2:
testb $0x8, %cl /* is it the source indicator? */
jz 0b /* Ignore it otherwise */
movq %rcx, %rsi /* For ever source page do a copy */
andq $0xfffffffffffff000, %rsi
movq %rdi, %rdx
movq %rsi, %rax
movq %r10, %rdi
movl $512, %ecx
rep ; movsq
movq %rax, %rdi
movq %rdx, %rsi
movl $512, %ecx
rep ; movsq
movq %rdx, %rdi
movq %r10, %rsi
movl $512, %ecx
rep ; movsq
lea PAGE_SIZE(%rax), %rsi
jmp 0b
3:
ANNOTATE_UNRET_SAFE
ret
int3
SYM_CODE_END(swap_pages)
.skip KEXEC_CONTROL_CODE_MAX_SIZE - (. - relocate_kernel), 0xcc
SYM_CODE_END(relocate_range);
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