diff options
Diffstat (limited to 'arch/x86/platform/efi/efi_thunk_64.S')
| -rw-r--r-- | arch/x86/platform/efi/efi_thunk_64.S | 121 |
1 files changed, 104 insertions, 17 deletions
diff --git a/arch/x86/platform/efi/efi_thunk_64.S b/arch/x86/platform/efi/efi_thunk_64.S index 8806fa73e6e6..ff85d28c50f2 100644 --- a/arch/x86/platform/efi/efi_thunk_64.S +++ b/arch/x86/platform/efi/efi_thunk_64.S @@ -1,9 +1,26 @@ /* * Copyright (C) 2014 Intel Corporation; author Matt Fleming + * + * Support for invoking 32-bit EFI runtime services from a 64-bit + * kernel. + * + * The below thunking functions are only used after ExitBootServices() + * has been called. This simplifies things considerably as compared with + * the early EFI thunking because we can leave all the kernel state + * intact (GDT, IDT, etc) and simply invoke the the 32-bit EFI runtime + * services from __KERNEL32_CS. This means we can continue to service + * interrupts across an EFI mixed mode call. + * + * We do however, need to handle the fact that we're running in a full + * 64-bit virtual address space. Things like the stack and instruction + * addresses need to be accessible by the 32-bit firmware, so we rely on + * using the identity mappings in the EFI page table to access the stack + * and kernel text (see efi_setup_page_tables()). */ #include <linux/linkage.h> #include <asm/page_types.h> +#include <asm/segment.h> .text .code64 @@ -33,14 +50,6 @@ ENTRY(efi64_thunk) leaq efi_exit32(%rip), %rbx subq %rax, %rbx movl %ebx, 8(%rsp) - leaq efi_gdt64(%rip), %rbx - subq %rax, %rbx - movl %ebx, 2(%ebx) - movl %ebx, 4(%rsp) - leaq efi_gdt32(%rip), %rbx - subq %rax, %rbx - movl %ebx, 2(%ebx) - movl %ebx, (%rsp) leaq __efi64_thunk(%rip), %rbx subq %rax, %rbx @@ -52,14 +61,92 @@ ENTRY(efi64_thunk) retq ENDPROC(efi64_thunk) - .data -efi_gdt32: - .word efi_gdt32_end - efi_gdt32 - .long 0 /* Filled out above */ - .word 0 - .quad 0x0000000000000000 /* NULL descriptor */ - .quad 0x00cf9a000000ffff /* __KERNEL_CS */ - .quad 0x00cf93000000ffff /* __KERNEL_DS */ -efi_gdt32_end: +/* + * We run this function from the 1:1 mapping. + * + * This function must be invoked with a 1:1 mapped stack. + */ +ENTRY(__efi64_thunk) + movl %ds, %eax + push %rax + movl %es, %eax + push %rax + movl %ss, %eax + push %rax + + 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) + + leaq 1f(%rip), %rbx + movq %rbx, func_rt_ptr(%rip) + + /* Switch to 32-bit descriptor */ + pushq $__KERNEL32_CS + leaq efi_enter32(%rip), %rax + pushq %rax + lretq + +1: addq $32, %rsp + + 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: + 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 + + call *%edi + + /* We must preserve return value */ + movl %eax, %edi + + movl 72(%esp), %eax + pushl $__KERNEL_CS + pushl %eax + + lret +ENDPROC(efi_enter32) + + .data + .balign 8 +func_rt_ptr: .quad 0 efi_saved_sp: .quad 0 |