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| /* SPDX-License-Identifier: GPL-2.0 */
| /*
| * Copyright (C) 2014, 2015 Intel Corporation; author Matt Fleming
| *
| * Early support for invoking 32-bit EFI services from a 64-bit kernel.
| *
| * Because this thunking occurs before ExitBootServices() we have to
| * restore the firmware's 32-bit GDT before we make EFI serivce calls,
| * since the firmware's 32-bit IDT is still currently installed and it
| * needs to be able to service interrupts.
| *
| * On the plus side, we don't have to worry about mangling 64-bit
| * addresses into 32-bits because we're executing with an identify
| * mapped pagetable and haven't transitioned to 64-bit virtual addresses
| * yet.
| */
|
| #include <linux/linkage.h>
| #include <asm/msr.h>
| #include <asm/page_types.h>
| #include <asm/processor-flags.h>
| #include <asm/segment.h>
|
| .code64
| .text
| ENTRY(efi64_thunk)
| push %rbp
| push %rbx
|
| subq $8, %rsp
| leaq efi_exit32(%rip), %rax
| movl %eax, 4(%rsp)
| leaq efi_gdt64(%rip), %rax
| movl %eax, (%rsp)
| movl %eax, 2(%rax) /* Fixup the gdt base address */
|
| movl %ds, %eax
| push %rax
| movl %es, %eax
| push %rax
| movl %ss, %eax
| push %rax
|
| /*
| * Convert x86-64 ABI params to i386 ABI
| */
| subq $32, %rsp
| movl %esi, 0x0(%rsp)
| movl %edx, 0x4(%rsp)
| movl %ecx, 0x8(%rsp)
| movq %r8, %rsi
| movl %esi, 0xc(%rsp)
| movq %r9, %rsi
| movl %esi, 0x10(%rsp)
|
| sgdt save_gdt(%rip)
|
| leaq 1f(%rip), %rbx
| movq %rbx, func_rt_ptr(%rip)
|
| /*
| * Switch to gdt with 32-bit segments. This is the firmware GDT
| * that was installed when the kernel started executing. This
| * pointer was saved at the EFI stub entry point in head_64.S.
| */
| leaq efi32_boot_gdt(%rip), %rax
| lgdt (%rax)
|
| pushq $__KERNEL_CS
| leaq efi_enter32(%rip), %rax
| pushq %rax
| lretq
|
| 1: addq $32, %rsp
|
| lgdt save_gdt(%rip)
|
| pop %rbx
| movl %ebx, %ss
| pop %rbx
| movl %ebx, %es
| pop %rbx
| movl %ebx, %ds
|
| /*
| * Convert 32-bit status code into 64-bit.
| */
| test %rax, %rax
| jz 1f
| movl %eax, %ecx
| andl $0x0fffffff, %ecx
| andl $0xf0000000, %eax
| shl $32, %rax
| or %rcx, %rax
| 1:
| addq $8, %rsp
| pop %rbx
| pop %rbp
| ret
| ENDPROC(efi64_thunk)
|
| ENTRY(efi_exit32)
| movq func_rt_ptr(%rip), %rax
| push %rax
| mov %rdi, %rax
| ret
| ENDPROC(efi_exit32)
|
| .code32
| /*
| * EFI service pointer must be in %edi.
| *
| * The stack should represent the 32-bit calling convention.
| */
| ENTRY(efi_enter32)
| movl $__KERNEL_DS, %eax
| movl %eax, %ds
| movl %eax, %es
| movl %eax, %ss
|
| /* Reload pgtables */
| movl %cr3, %eax
| movl %eax, %cr3
|
| /* Disable paging */
| movl %cr0, %eax
| btrl $X86_CR0_PG_BIT, %eax
| movl %eax, %cr0
|
| /* Disable long mode via EFER */
| movl $MSR_EFER, %ecx
| rdmsr
| btrl $_EFER_LME, %eax
| wrmsr
|
| call *%edi
|
| /* We must preserve return value */
| movl %eax, %edi
|
| /*
| * Some firmware will return with interrupts enabled. Be sure to
| * disable them before we switch GDTs.
| */
| cli
|
| movl 56(%esp), %eax
| movl %eax, 2(%eax)
| lgdtl (%eax)
|
| movl %cr4, %eax
| btsl $(X86_CR4_PAE_BIT), %eax
| movl %eax, %cr4
|
| movl %cr3, %eax
| movl %eax, %cr3
|
| movl $MSR_EFER, %ecx
| rdmsr
| btsl $_EFER_LME, %eax
| wrmsr
|
| xorl %eax, %eax
| lldt %ax
|
| movl 60(%esp), %eax
| pushl $__KERNEL_CS
| pushl %eax
|
| /* Enable paging */
| movl %cr0, %eax
| btsl $X86_CR0_PG_BIT, %eax
| movl %eax, %cr0
| lret
| ENDPROC(efi_enter32)
|
| .data
| .balign 8
| .global efi32_boot_gdt
| efi32_boot_gdt: .word 0
| .quad 0
|
| save_gdt: .word 0
| .quad 0
| func_rt_ptr: .quad 0
|
| .global efi_gdt64
| efi_gdt64:
| .word efi_gdt64_end - efi_gdt64
| .long 0 /* Filled out by user */
| .word 0
| .quad 0x0000000000000000 /* NULL descriptor */
| .quad 0x00af9a000000ffff /* __KERNEL_CS */
| .quad 0x00cf92000000ffff /* __KERNEL_DS */
| .quad 0x0080890000000000 /* TS descriptor */
| .quad 0x0000000000000000 /* TS continued */
| efi_gdt64_end:
|
|
