X86PatchInstruction.c File Reference

#include "BaseLibInternals.h"

Go to the source code of this file.

Functions
VOID EFIAPI	PatchInstructionX86 (OUT X86_ASSEMBLY_PATCH_LABEL *InstructionEnd, IN UINT64 PatchValue, IN UINTN ValueSize)

Detailed Description

IA-32/x64 PatchInstructionX86()

Copyright (C) 2018, Intel Corporation. All rights reserved.
Copyright (C) 2018, Red Hat, Inc.

SPDX-License-Identifier: BSD-2-Clause-Patent

Definition in file X86PatchInstruction.c.

Function Documentation

PatchInstructionX86()

VOID EFIAPI PatchInstructionX86	(	OUT X86_ASSEMBLY_PATCH_LABEL *	InstructionEnd,
		IN UINT64	PatchValue,
		IN UINTN	ValueSize
	)

Patch the immediate operand of an IA32 or X64 instruction such that the byte, word, dword or qword operand is encoded at the end of the instruction's binary representation.

This function should be used to update object code that was compiled with NASM from assembly source code. Example:

NASM source code:

  mov     eax, strict dword 0 ; the imm32 zero operand will be patched

ASM_PFX(gPatchCr3): mov cr3, eax

C source code:

X86_ASSEMBLY_PATCH_LABEL gPatchCr3; PatchInstructionX86 (gPatchCr3, AsmReadCr3 (), 4);

Parameters

[out]	InstructionEnd	Pointer right past the instruction to patch. The immediate operand to patch is expected to comprise the trailing bytes of the instruction. If InstructionEnd is closer to address 0 than ValueSize permits, then ASSERT().
[in]	PatchValue	The constant to write to the immediate operand. The caller is responsible for ensuring that PatchValue can be represented in the byte, word, dword or qword operand (as indicated through ValueSize); otherwise ASSERT().
[in]	ValueSize	The size of the operand in bytes; must be 1, 2, 4, or 8. ASSERT() otherwise.

Definition at line 48 of file X86PatchInstruction.c.