Commit 9241dfe7 authored by Arvind Sankar's avatar Arvind Sankar Committed by Ard Biesheuvel
Browse files

efi/x86: Drop the special GDT for the EFI thunk 



Instead of using efi_gdt64 to switch back to 64-bit mode and then
switching to the real boot-time GDT, just switch to the boot-time GDT
directly. The two GDT's are identical other than efi_gdt64 not including
the 32-bit code segment.

Signed-off-by: default avatarArvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200523221513.1642948-1-nivedita@alum.mit.edu


Signed-off-by: default avatarArd Biesheuvel <ardb@kernel.org>
parent 6e99d321

arch/x86/boot/compressed/efi_thunk_64.S

+3 −16
Original line number Diff line number Diff line
@@ -28,8 +28,6 @@ SYM_FUNC_START(__efi64_thunk) 
	push	%rbx



	leaq	1f(%rip), %rbp

	leaq	efi_gdt64(%rip), %rbx

	movl	%ebx, 2(%rbx)		/* Fixup the gdt base address */



	movl	%ds, %eax

	push	%rax
@@ -48,7 +46,8 @@ SYM_FUNC_START(__efi64_thunk) 
	movl	%r8d, 0xc(%rsp)

	movl	%r9d, 0x10(%rsp)



	sgdt	0x14(%rsp)

	leaq	0x14(%rsp), %rbx

	sgdt	(%rbx)



	/*

	 * Switch to gdt with 32-bit segments. This is the firmware GDT
@@ -68,8 +67,7 @@ SYM_FUNC_START(__efi64_thunk) 
	pushq	%rax

	lretq



1:	lgdt	0x14(%rsp)

	addq	$32, %rsp

1:	addq	$32, %rsp

	movq	%rdi, %rax



	pop	%rbx
@@ -175,14 +173,3 @@ SYM_DATA_END(efi32_boot_cs) 
SYM_DATA_START(efi32_boot_ds)

	.word	0

SYM_DATA_END(efi32_boot_ds)
 


SYM_DATA_START(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 */

SYM_DATA_END_LABEL(efi_gdt64, SYM_L_LOCAL, efi_gdt64_end)

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