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-rw-r--r--arch/x86/kernel/relocate_kernel_64.S316
1 files changed, 316 insertions, 0 deletions
diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S
new file mode 100644
index 000000000..4809c0dc4
--- /dev/null
+++ b/arch/x86/kernel/relocate_kernel_64.S
@@ -0,0 +1,316 @@
+/* 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 <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_kernel)
+ UNWIND_HINT_EMPTY
+ 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_EMPTY
+ /* 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
+ */
+ movl $X86_CR4_PAE, %eax
+ testq $X86_CR4_LA57, %r13
+ jz 1f
+ orl $X86_CR4_LA57, %eax
+1:
+ movq %rax, %cr4
+
+ jmp 1f
+1:
+
+ /* 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 1f
+ wbinvd
+1:
+
+ 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 1f
+ 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
+
+1:
+ 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_EMPTY
+ 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_EMPTY
+ 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)
+
+ .globl kexec_control_code_size
+.set kexec_control_code_size, . - relocate_kernel