/* SPDX-License-Identifier: GPL-2.0-only */ /* * relocate_kernel.S - put the kernel image in place to boot * Copyright (C) 2002-2005 Eric Biederman */ #include #include #include #include #include #include #include #include #include /* * 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: /* Save the preserve_context to %r11 as swap_pages clobbers %rcx. */ 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 indirection_page 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 /* Save destination page to %rdx */ movq %rsi, %rax /* Save source page to %rax */ /* copy source page to swap page */ movq %r10, %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 %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);