1/* SPDX-License-Identifier: GPL-2.0 */ 2/* 3 * Copyright (C) 2014 Intel Corporation; author Matt Fleming 4 * 5 * Support for invoking 32-bit EFI runtime services from a 64-bit 6 * kernel. 7 * 8 * The below thunking functions are only used after ExitBootServices() 9 * has been called. This simplifies things considerably as compared with 10 * the early EFI thunking because we can leave all the kernel state 11 * intact (GDT, IDT, etc) and simply invoke the 32-bit EFI runtime 12 * services from __KERNEL32_CS. This means we can continue to service 13 * interrupts across an EFI mixed mode call. 14 * 15 * We do however, need to handle the fact that we're running in a full 16 * 64-bit virtual address space. Things like the stack and instruction 17 * addresses need to be accessible by the 32-bit firmware, so we rely on 18 * using the identity mappings in the EFI page table to access the stack 19 * and kernel text (see efi_setup_page_tables()). 20 */ 21 22#include <linux/linkage.h> 23#include <linux/objtool.h> 24#include <asm/page_types.h> 25#include <asm/segment.h> 26#include <asm/nospec-branch.h> 27 28 .text 29 .code64 30SYM_FUNC_START(__efi64_thunk) 31STACK_FRAME_NON_STANDARD __efi64_thunk 32 push %rbp 33 push %rbx 34 35 /* 36 * Switch to 1:1 mapped 32-bit stack pointer. 37 */ 38 movq %rsp, %rax 39 movq efi_mixed_mode_stack_pa(%rip), %rsp 40 push %rax 41 42 /* 43 * Copy args passed via the stack 44 */ 45 subq $0x24, %rsp 46 movq 0x18(%rax), %rbp 47 movq 0x20(%rax), %rbx 48 movq 0x28(%rax), %rax 49 movl %ebp, 0x18(%rsp) 50 movl %ebx, 0x1c(%rsp) 51 movl %eax, 0x20(%rsp) 52 53 /* 54 * Calculate the physical address of the kernel text. 55 */ 56 movq $__START_KERNEL_map, %rax 57 subq phys_base(%rip), %rax 58 59 leaq 1f(%rip), %rbp 60 leaq 2f(%rip), %rbx 61 subq %rax, %rbp 62 subq %rax, %rbx 63 64 movl %ebx, 0x0(%rsp) /* return address */ 65 movl %esi, 0x4(%rsp) 66 movl %edx, 0x8(%rsp) 67 movl %ecx, 0xc(%rsp) 68 movl %r8d, 0x10(%rsp) 69 movl %r9d, 0x14(%rsp) 70 71 /* Switch to 32-bit descriptor */ 72 pushq $__KERNEL32_CS 73 pushq %rdi /* EFI runtime service address */ 74 lretq 75 761: movq 0x20(%rsp), %rsp 77 pop %rbx 78 pop %rbp 79 ANNOTATE_UNRET_SAFE 80 ret 81 int3 82 83 .code32 842: pushl $__KERNEL_CS 85 pushl %ebp 86 lret 87SYM_FUNC_END(__efi64_thunk) 88 89 .bss 90 .balign 8 91SYM_DATA(efi_mixed_mode_stack_pa, .quad 0) 92