/* 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>
#include <asm/asm-offsets.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)
/*
* The .text..relocate_kernel and .data..relocate_kernel sections are copied
* into the control page, and the remainder of the page is used as the stack.
*/
.section .data..relocate_kernel,"a";
/* Minimal CPU state */
SYM_DATA_LOCAL(saved_rsp, .quad 0)
SYM_DATA_LOCAL(saved_cr0, .quad 0)
SYM_DATA_LOCAL(saved_cr3, .quad 0)
SYM_DATA_LOCAL(saved_cr4, .quad 0)
/* other data */
SYM_DATA(kexec_va_control_page, .quad 0)
SYM_DATA(kexec_pa_table_page, .quad 0)
SYM_DATA(kexec_pa_swap_page, .quad 0)
SYM_DATA_LOCAL(pa_backup_pages_map, .quad 0)
.section .text..relocate_kernel,"ax";
.code64
SYM_CODE_START_NOALIGN(relocate_kernel)
UNWIND_HINT_END_OF_STACK
ANNOTATE_NOENDBR
/*
* %rdi indirection_page
* %rsi pa_control_page
* %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
/* zero out flags, and disable interrupts */
pushq $0
popfq
/* Switch to the identity mapped page tables */
movq %cr3, %rax
movq kexec_pa_table_page(%rip), %r9
movq %r9, %cr3
/* Leave CR4 in %r13 to enable the right paging mode later. */
movq %cr4, %r13
/* Disable global pages immediately to ensure this mapping is RWX */
movq %r13, %r12
andq $~(X86_CR4_PGE), %r12
movq %r12, %cr4
/* Save %rsp and CRs. */
movq %r13, saved_cr4(%rip)
movq %rsp, saved_rsp(%rip)
movq %rax, saved_cr3(%rip)
movq %cr0, %rax
movq %rax, saved_cr0(%rip)
/* save indirection list for jumping back */
movq %rdi, pa_backup_pages_map(%rip)
/* Save the preserve_context to %r11 as swap_pages clobbers %rcx. */
movq %rcx, %r11
/* setup a new stack at the end of the physical control page */
lea PAGE_SIZE(%rsi), %rsp
/* jump to identity mapped page */
0: addq $identity_mapped - 0b, %rsi
subq $__relocate_kernel_start - 0b, %rsi
ANNOTATE_RETPOLINE_SAFE
jmp *%rsi
SYM_CODE_END(relocate_kernel)
SYM_CODE_START_LOCAL_NOALIGN(identity_mapped)
UNWIND_HINT_END_OF_STACK
/*
* %rdi indirection page
* %rdx start address
* %r8 host_mem_enc_active
* %r9 page table page
* %r11 preserve_context
* %r13 original CR4 when relocate_kernel() was invoked
*/
/* 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 %r8, %r8
jz .Lsme_off
wbinvd
.Lsme_off:
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
testq %r11, %r11 /* preserve_context */
jnz .Lrelocate
/*
* set all of the registers to known values
* leave %rsp alone
*/
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
/* Use the swap page for the callee's stack */
movq kexec_pa_swap_page(%rip), %r10
leaq PAGE_SIZE(%r10), %rsp
/* push the existing entry point onto the callee's stack */
pushq %rdx
ANNOTATE_RETPOLINE_SAFE
call *%rdx
/* get the re-entry point of the peer system */
popq %rbp
movq kexec_pa_swap_page(%rip), %r10
movq pa_backup_pages_map(%rip), %rdi
movq kexec_pa_table_page(%rip), %rax
movq %rax, %cr3
/* Find start (and end) of this physical mapping of control page */
leaq (%rip), %r8
ANNOTATE_NOENDBR
andq $PAGE_MASK, %r8
lea PAGE_SIZE(%r8), %rsp
movl $1, %r11d /* Ensure preserve_context flag is set */
call swap_pages
movq kexec_va_control_page(%rip), %rax
0: addq $virtual_mapped - 0b, %rax
subq $__relocate_kernel_start - 0b, %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 saved_rsp(%rip), %rsp
movq saved_cr4(%rip), %rax
movq %rax, %cr4
movq saved_cr3(%rip), %rax
movq saved_cr0(%rip), %r8
movq %rax, %cr3
movq %r8, %cr0
#ifdef CONFIG_KEXEC_JUMP
/* Saved in save_processor_state. */
movq $saved_context, %rax
lgdt saved_context_gdt_desc(%rax)
#endif
/* relocate_kernel() returns the re-entry point for next time */
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
/*
* %rdi indirection page
* %r11 preserve_context
*/
movq %rdi, %rcx /* Put the indirection_page in %rcx */
xorl %edi, %edi
xorl %esi, %esi
jmp .Lstart /* Should start with an indirection record */
.Lloop: /* top, read another word for the indirection page */
movq (%rbx), %rcx
addq $8, %rbx
.Lstart:
testb $0x1, %cl /* is it a destination page? */
jz .Lnotdest
movq %rcx, %rdi
andq $0xfffffffffffff000, %rdi
jmp .Lloop
.Lnotdest:
testb $0x2, %cl /* is it an indirection page? */
jz .Lnotind
movq %rcx, %rbx
andq $0xfffffffffffff000, %rbx
jmp .Lloop
.Lnotind:
testb $0x4, %cl /* is it the done indicator? */
jz .Lnotdone
jmp .Ldone
.Lnotdone:
testb $0x8, %cl /* is it the source indicator? */
jz .Lloop /* Ignore it otherwise */
movq %rcx, %rsi /* For ever source page do a copy */
andq $0xfffffffffffff000, %rsi
movq %rdi, %rdx /* Save destination page to %rdx */
movq %rsi, %rax /* Save source page to %rax */
testq %r11, %r11 /* Only actually swap for ::preserve_context */
jz .Lnoswap
/* copy source page to swap page */
movq kexec_pa_swap_page(%rip), %rdi
movl $512, %ecx
rep ; movsq
/* copy destination page to source page */
movq %rax, %rdi
movq %rdx, %rsi
movl $512, %ecx
rep ; movsq
/* copy swap page to destination page */
movq %rdx, %rdi
movq kexec_pa_swap_page(%rip), %rsi
.Lnoswap:
movl $512, %ecx
rep ; movsq
lea PAGE_SIZE(%rax), %rsi
jmp .Lloop
.Ldone:
ANNOTATE_UNRET_SAFE
ret
int3
SYM_CODE_END(swap_pages)
