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torvalds
GitHub Repository: torvalds/linux
 Path: blob/master/arch/x86/platform/efi/efi_stub_32.S
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/* SPDX-License-Identifier: GPL-2.0 */

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/*

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 * EFI call stub for IA32.

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 *

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 * This stub allows us to make EFI calls in physical mode with interrupts

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 * turned off.

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 */

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#include <linux/linkage.h>

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#include <linux/init.h>

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#include <asm/asm-offsets.h>

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#include <asm/page_types.h>

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	__INIT

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SYM_FUNC_START(efi_call_svam)

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	push	%ebp

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	movl	%esp, %ebp

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	push	%ebx

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	push	16(%esp)

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	push	16(%esp)

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	push	%ecx

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	push	%edx

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	movl	%eax, %ebx		// &systab_phys->runtime

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	/*

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	 * Switch to the flat mapped alias of this routine, by jumping to the

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	 * address of label '1' after subtracting PAGE_OFFSET from it.

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	 */

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	movl	$1f, %edx

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	subl	$__PAGE_OFFSET, %edx

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	jmp	*%edx

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1:

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	/* disable paging */

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	movl	%cr0, %edx

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	andl	$0x7fffffff, %edx

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	movl	%edx, %cr0

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	/* convert the stack pointer to a flat mapped address */

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	subl	$__PAGE_OFFSET, %esp

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	/* call the EFI routine */

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	movl	(%eax), %eax

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	call	*EFI_svam(%eax)

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	/* grab the virtually remapped EFI runtime services table pointer */

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	movl	(%ebx), %ecx

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	movl	36(%esp), %edx		// &efi.runtime

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	movl	%ecx, (%edx)

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	/* re-enable paging */

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	movl	%cr0, %edx

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	orl	$0x80000000, %edx

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	movl	%edx, %cr0

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	movl	16(%esp), %ebx

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	leave

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	RET

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SYM_FUNC_END(efi_call_svam)

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