RVA与Offset的换算函数

最新推荐文章于 2023-12-17 14:49:21 发布

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最新推荐文章于 2023-12-17 14:49:21 发布

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本文提供了一种在PE文件中进行相对虚拟地址（RVA）与文件偏移相互转换的方法。通过两个实用函数，可以实现从RVA到文件偏移及从文件偏移到RVA的准确转换，这对于理解和操作PE文件格式非常有用。

function RVAToFileOffset(FileName:string; RVA: Cardinal): Cardinal;
var
  MemPE: TFileStream;
  PEDosHead: TImageDosHeader;
  PENtHead: TImageNtHeaders;
  Section : TImageSectionHeader;
  i, SectionsCount: Integer;
begin
  Result := RVA;
  MemPE:=TFileStream.Create(FileName,fmOpenReadWrite);
  try
    MemPE.Seek(0, soFromBeginning);
    MemPE.Read(PEDosHead, SizeOf(PEDosHead));
    MemPE.Seek(PEDosHead._lfanew, soFromBeginning);
    MemPE.Read(PENtHead, SizeOf(PENtHead));

    SectionsCount := PENtHead.FileHeader.NumberOfSections;

    if SectionsCount <> 0 then
      for i := 0 to SectionsCount - 1 do
      begin
        MemPE.Read(Section, SizeOf(Section));
        if (RVA >= Section.VirtualAddress) and (RVA < Section.VirtualAddress + Section.SizeOfRawData) then
        begin
          Result := RVA - Section.VirtualAddress + Section.PointerToRawData;
          Break;
        end;
      end;
  finally
    FreeAndNil(MemPE);
  end;
end;

function FileOffsetToRVA(FileName:string; Offset: Cardinal): Cardinal;
var
  MemPE: TFileStream;
  PEDosHead: TImageDosHeader;
  PENtHead: TImageNtHeaders;
  Section : TImageSectionHeader;
  i, SectionsCount: Integer;
begin
  Result :=Offset;
  MemPE:=TFileStream.Create(FileName,fmOpenReadWrite);
  try
    MemPE.Seek(0, soFromBeginning);
    MemPE.Read(PEDosHead, SizeOf(PEDosHead));
    MemPE.Seek(PEDosHead._lfanew, soFromBeginning);
    MemPE.Read(PENtHead, SizeOf(PENtHead));

    SectionsCount := PENtHead.FileHeader.NumberOfSections;

    if SectionsCount <> 0 then
      for i := 0 to SectionsCount - 1 do
      begin
        MemPE.Read(Section, SizeOf(Section));
        if (Offset >= Section.PointerToRawData) and (Offset < Section.PointerToRawData + Section.SizeOfRawData) then
        begin
          Result := Offset - Section.PointerToRawData + Section.VirtualAddress;
          Break;
        end;
      end;
  finally
    FreeAndNil(MemPE);
  end;
end;

程序源代码：

unit Unit1;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls;

type
TForm1 = class(TForm)
    Button1: TButton;
    Edit1: TEdit;
    Edit2: TEdit;
    Edit3: TEdit;
    Edit4: TEdit;
    Button2: TButton;
    Edit5: TEdit;
    Label1: TLabel;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
private
    { Private declarations }
public
    { Public declarations }
end;

var
Form1: TForm1;

implementation

{$R *.dfm}

function FileOffsetToRVA(FileName:string; Offset: Cardinal): Cardinal;
var
MemPE: TFileStream;
PEDosHead: TImageDosHeader;
PENtHead: TImageNtHeaders;
Section : TImageSectionHeader;
i, SectionsCount: Integer;
begin
Result :=Offset;
MemPE:=TFileStream.Create(FileName,fmOpenReadWrite);
try
    MemPE.Seek(0, soFromBeginning);
    MemPE.Read(PEDosHead, SizeOf(PEDosHead));
    MemPE.Seek(PEDosHead._lfanew, soFromBeginning);
    MemPE.Read(PENtHead, SizeOf(PENtHead));

    SectionsCount := PENtHead.FileHeader.NumberOfSections;

    if SectionsCount <> 0 then
      for i := 0 to SectionsCount - 1 do
      begin
        MemPE.Read(Section, SizeOf(Section));
        if (Offset >= Section.PointerToRawData) and (Offset < Section.PointerToRawData + Section.SizeOfRawData) then
        begin
          Result := Offset - Section.PointerToRawData + Section.VirtualAddress;
          Break;
        end;
      end;
finally
    FreeAndNil(MemPE);
end;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
Edit2.Text := string(FileOffsetToRVA(Edit5.Text,Cardinal(Edit1.Text)));
end;

function RVAToFileOffset(FileName:string; RVA: Cardinal): Cardinal;
var
MemPE: TFileStream;
PEDosHead: TImageDosHeader;
PENtHead: TImageNtHeaders;
Section : TImageSectionHeader;
i, SectionsCount: Integer;
begin
Result := RVA;
MemPE:=TFileStream.Create(FileName,fmOpenReadWrite);
try
    MemPE.Seek(0, soFromBeginning);
    MemPE.Read(PEDosHead, SizeOf(PEDosHead));
    MemPE.Seek(PEDosHead._lfanew, soFromBeginning);
    MemPE.Read(PENtHead, SizeOf(PENtHead));

    SectionsCount := PENtHead.FileHeader.NumberOfSections;

    if SectionsCount <> 0 then
      for i := 0 to SectionsCount - 1 do
      begin
        MemPE.Read(Section, SizeOf(Section));
        if (RVA >= Section.VirtualAddress) and (RVA < Section.VirtualAddress + Section.SizeOfRawData) then
        begin
          Result := RVA - Section.VirtualAddress + Section.PointerToRawData;
          Break;
        end;
      end;
finally
    FreeAndNil(MemPE);
end;
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
Edit4.Text := string(RVAToFileOffset(Edit5.Text,Cardinal(Edit3.Text)));
end;

end.