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3e1e00c00e
As a first step to removing the awkward 'struct efi_scratch' definition that conveniently combines the storage of the mixed mode stack pointer with the MM pointer variable that records the task's MM pointer while it is being replaced with the EFI MM one, move the mixed mode stack pointer into a separate variable. Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
77 lines
1.8 KiB
ArmAsm
77 lines
1.8 KiB
ArmAsm
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Copyright (C) 2014 Intel Corporation; author Matt Fleming
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*
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* Support for invoking 32-bit EFI runtime services from a 64-bit
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* kernel.
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*
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* The below thunking functions are only used after ExitBootServices()
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* has been called. This simplifies things considerably as compared with
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* the early EFI thunking because we can leave all the kernel state
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* intact (GDT, IDT, etc) and simply invoke the the 32-bit EFI runtime
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* services from __KERNEL32_CS. This means we can continue to service
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* interrupts across an EFI mixed mode call.
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*
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* We do however, need to handle the fact that we're running in a full
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* 64-bit virtual address space. Things like the stack and instruction
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* addresses need to be accessible by the 32-bit firmware, so we rely on
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* using the identity mappings in the EFI page table to access the stack
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* and kernel text (see efi_setup_page_tables()).
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*/
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#include <linux/linkage.h>
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#include <asm/page_types.h>
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#include <asm/segment.h>
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.text
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.code64
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SYM_CODE_START(__efi64_thunk)
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push %rbp
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push %rbx
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/*
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* Switch to 1:1 mapped 32-bit stack pointer.
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*/
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movq %rsp, %rax
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movq efi_mixed_mode_stack_pa(%rip), %rsp
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push %rax
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/*
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* Calculate the physical address of the kernel text.
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*/
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movq $__START_KERNEL_map, %rax
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subq phys_base(%rip), %rax
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leaq 1f(%rip), %rbp
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leaq 2f(%rip), %rbx
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subq %rax, %rbp
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subq %rax, %rbx
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subq $28, %rsp
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movl %ebx, 0x0(%rsp) /* return address */
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movl %esi, 0x4(%rsp)
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movl %edx, 0x8(%rsp)
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movl %ecx, 0xc(%rsp)
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movl %r8d, 0x10(%rsp)
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movl %r9d, 0x14(%rsp)
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/* Switch to 32-bit descriptor */
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pushq $__KERNEL32_CS
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pushq %rdi /* EFI runtime service address */
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lretq
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1: movq 24(%rsp), %rsp
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pop %rbx
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pop %rbp
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retq
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.code32
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2: pushl $__KERNEL_CS
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pushl %ebp
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lret
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SYM_CODE_END(__efi64_thunk)
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.bss
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.balign 8
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SYM_DATA(efi_mixed_mode_stack_pa, .quad 0)
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