cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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efi_thunk_64.S (2131B)

      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
     27	.text
     28	.code64
     29SYM_FUNC_START(__efi64_thunk)
     30STACK_FRAME_NON_STANDARD __efi64_thunk
     31	push	%rbp
     32	push	%rbx
     33
     34	/*
     35	 * Switch to 1:1 mapped 32-bit stack pointer.
     36	 */
     37	movq	%rsp, %rax
     38	movq	efi_mixed_mode_stack_pa(%rip), %rsp
     39	push	%rax
     40
     41	/*
     42	 * Copy args passed via the stack
     43	 */
     44	subq	$0x24, %rsp
     45	movq	0x18(%rax), %rbp
     46	movq	0x20(%rax), %rbx
     47	movq	0x28(%rax), %rax
     48	movl	%ebp, 0x18(%rsp)
     49	movl	%ebx, 0x1c(%rsp)
     50	movl	%eax, 0x20(%rsp)
     51
     52	/*
     53	 * Calculate the physical address of the kernel text.
     54	 */
     55	movq	$__START_KERNEL_map, %rax
     56	subq	phys_base(%rip), %rax
     57
     58	leaq	1f(%rip), %rbp
     59	leaq	2f(%rip), %rbx
     60	subq	%rax, %rbp
     61	subq	%rax, %rbx
     62
     63	movl	%ebx, 0x0(%rsp)		/* return address */
     64	movl	%esi, 0x4(%rsp)
     65	movl	%edx, 0x8(%rsp)
     66	movl	%ecx, 0xc(%rsp)
     67	movl	%r8d, 0x10(%rsp)
     68	movl	%r9d, 0x14(%rsp)
     69
     70	/* Switch to 32-bit descriptor */
     71	pushq	$__KERNEL32_CS
     72	pushq	%rdi			/* EFI runtime service address */
     73	lretq
     74
     751:	movq	0x20(%rsp), %rsp
     76	pop	%rbx
     77	pop	%rbp
     78	RET
     79
     80	.code32
     812:	pushl	$__KERNEL_CS
     82	pushl	%ebp
     83	lret
     84SYM_FUNC_END(__efi64_thunk)
     85
     86	.bss
     87	.balign 8
     88SYM_DATA(efi_mixed_mode_stack_pa, .quad 0)