仿照windows的loader实现的pe-loader
本人接触pe文件格式不久，参考网上的一些资料写了一个pe loader，主要是通过把需要加载的文件的所所有section加载到相应的RVA上，然后进行重定位处理、导入表和导出表处理、资源段处理。由于本loader.exe会被加载到0x0f400000处，因此可以把0x400000给被加载的文件预留了，这样可以避免重定位所带来的性能损耗。导入表的处理主要是通过调用GetProcAddress获取导入表中函数的地址。导出表一般仅在dll中使用，而此主要是用于load exe文件，所以不用做任何处理。资源段处理资料不多，我这里好像有些问题，加载console程序可以正常执行，但是当加载一部分gui程序则不能成功，而令一些gui程序则会成功。望高手能指教一二。
下面是源代码部分：
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/*
*LocalFile是对读文件操作的一个简单封装
*/
//LocalFile.h
#pragma once
class CLocalFile
{
public:
CLocalFile(const char * name);
~CLocalFile(void);
int Read(size_t offset, size_t size, void *ppBuf);
size_t GetSize() const { return m_size;}
private:
HANDLE m_fd;
size_t m_size;
};
//LocalFile.cpp
#include "LocalFile.h"
CLocalFile::CLocalFile(const char * name)
{
assert(NULL != name);
assert(0 != name[0]);
m_fd = CreateFileA(name, GENERIC_READ,
FILE_SHARE_READ, NULL,
OPEN_EXISTING,
FILE_ATTRIBUTE_NORMAL, NULL);
if (INVALID_HANDLE_VALUE == m_fd) {
printf("Open file %s failed, error: %d!/n",name, GetLastError());
return ;
}
m_size = GetFileSize(m_fd, NULL);
return;
}
CLocalFile::~CLocalFile(void)
{
if (NULL != m_fd) {
CloseHandle(m_fd);
}
}
int CLocalFile::Read(size_t offset,
size_t size,
void * pBuf)
{
DWORD ret;
ULONG rdsize;
ret = SetFilePointer(m_fd, offset, NULL, FILE_BEGIN);
if (INVALID_SET_FILE_POINTER == ret) {
ret = GetLastError();
printf("Seek file failed, error: %d!/n", ret);
return ret;
}
if (!ReadFile(m_fd, pBuf, size, &rdsize, NULL)) {
ret = GetLastError();
printf("Read file failed, error: %d/n", ret);
return ret;
}
return 0;
}
//loader.cpp
#include "LocalFile.h"
/*把该loader.exe的加载地址设置为0x0f400000,从而可以把0x00400000地址
*预留给将要被加载的程序，从而可以避免因地址重定位而带来的性能损耗。
*/
#pragma comment(linker, "/BASE:0x0f400000")
inline int CDECL DebugPrint(const char *fmt,...)
{
int nLength = 0;
#if defined(_DEBUG)
va_list ap;
va_start(ap, fmt);
nLength = vprintf(fmt, ap);
va_end(ap);
#endif
return nLength;
}
void DumpPeInfo(PeInfo *pInfo)
{
DebugPrint("------------headers info------------/n" /
"imageBase: 0x%x. /n" /
"entryPoint: 0x%x. /n" /
"sections: 0x%x. /n" /
"imageSize: 0x%x. /n" /
"exportRva: 0x%x. /n" /
"exportSize: 0x%x. /n" /
"importRva: 0x%x. /n" /
"importSize: 0x%x. /n" /
"resourceRva: 0x%x. /n" /
"resourceSize: 0x%x. /n" /
"relocRva: 0x%x. /n" /
"relocSize: 0x%x. /n" /
"debugRva: 0x%x. /n" /
"debugSize: 0x%x. /n" /
"offsetSections: 0x%x. /n" /
"fileType: %s. /n",
pInfo->imageBase,
pInfo->entryPoint,
pInfo->sections,
pInfo->imageSize,
pInfo->exRva,
pInfo->exSize,
pInfo->imRva,
pInfo->imSize,
pInfo->resRva,
pInfo->resSize,
pInfo->relocRva,
pInfo->relocSize,
pInfo->dbgRva,
pInfo->dbgSize,
pInfo->offsetSection,
pInfo->fileType == 0 ? "exe":"dll");
}
BOOL IsPEFile(CLocalFile& lf)
{
IMAGE_DOS_HEADER dh;
IMAGE_NT_HEADERS nh;
lf.Read(0, sizeof(IMAGE_DOS_HEADER), &dh);
if (IMAGE_DOS_SIGNATURE != dh.e_magic) {
return FALSE;
}
lf.Read(dh.e_lfanew, sizeof(IMAGE_NT_HEADERS), &nh);
if (IMAGE_NT_SIGNATURE != nh.Signature) {
return FALSE;
}
return TRUE;
}
BOOL ParseNTHeader(CLocalFile &lf, PeInfo &pe)
{
IMAGE_DOS_HEADER dh;
IMAGE_NT_HEADERS nh;
PIMAGE_FILE_HEADER pfh;
PIMAGE_OPTIONAL_HEADER32 poh;
lf.Read(0, sizeof(IMAGE_DOS_HEADER), &dh);
pe.offsetSection = dh.e_lfanew + sizeof(IMAGE_NT_HEADERS);
lf.Read(dh.e_lfanew, sizeof(IMAGE_NT_HEADERS), &nh);
pfh = &nh.FileHeader;
poh = &nh.OptionalHeader;
assert(IMAGE_FILE_MACHINE_I386 == pfh->Machine);
assert(pfh->SizeOfOptionalHeader == sizeof(IMAGE_OPTIONAL_HEADER32));
pe.sections = pfh->NumberOfSections;
pe.imageBase = poh->ImageBase;
pe.entryPoint = poh->AddressOfEntryPoint;
pe.imageSize = poh->SizeOfImage;
pe.exRva = poh->DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT].VirtualAddress;
pe.exSize = poh->DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT].Size;
pe.imRva = poh->DataDirectory[IMAGE_DIRECTORY_ENTRY_IMPORT].VirtualAddress;
pe.imSize = poh->DataDirectory[IMAGE_DIRECTORY_ENTRY_IMPORT].Size;
pe.resRva = poh->DataDirectory[IMAGE_DIRECTORY_ENTRY_RESOURCE].VirtualAddress;
pe.resSize = poh->DataDirectory[IMAGE_DIRECTORY_ENTRY_RESOURCE].Size;
pe.relocRva = poh->DataDirectory[IMAGE_DIRECTORY_ENTRY_BASERELOC].VirtualAddress;
pe.relocSize = poh->DataDirectory[IMAGE_DIRECTORY_ENTRY_BASERELOC].Size;
pe.dbgRva = poh->DataDirectory[IMAGE_DIRECTORY_ENTRY_DEBUG].VirtualAddress;
pe.dbgSize = poh->DataDirectory[IMAGE_DIRECTORY_ENTRY_DEBUG].Size;
pe.fileType = pfh->Characteristics == IMAGE_FILE_DLL ? IMAGE_FILE_DLL : 0;
DumpPeInfo(&pe);
return TRUE;
}
BOOL LoadSections(CLocalFile &lf, PeInfo &pe, MODULEINFO &mi)
{
PIMAGE_SECTION_HEADER psh, ptmp;
DWORD protect = 0, oldProtect = 0;
char name[9] = "/0";
psh = (PIMAGE_SECTION_HEADER)_alloca(pe.sections * sizeof(IMAGE_SECTION_HEADER));
if (NULL == psh) {
printf("Memory not enough!/n");
return FALSE;
}
lf.Read(pe.offsetSection, pe.sections * sizeof(IMAGE_SECTION_HEADER), psh);
ptmp = psh;
DebugPrint("/n/n------------sections info------------/n" /
"name/tVA/tSOD/tPTR/tPTR/tPTL/tNOR/tNOL/tCrt/n");
/* 循环从被加载的文件中读取各个section内容，并存放在该section所指定的
* VirtualAddress地址空间中。
*/
for (int i = 0; i < pe.sections; ++i, ptmp++) {
memcpy(name, ptmp->Name, 8);
if (NULL != ptmp->PointerToRawData && 0 != ptmp->SizeOfRawData) {
lf.Read(ptmp->PointerToRawData,
ptmp->SizeOfRawData,
(void *)((DWORD)mi.lpBaseOfDll + ptmp->VirtualAddress));
}
/* 此处代码主要功能是根据各个区段的Characteristics值，
* 来设置其所在内存的页属性，但因在RelocPeModule机制重定位时还需要对相关内存
* 进行写入，因此此处的代码应该在RelocPeModule函数调用之后才能执行。
*/
#if 0
if (ptmp->Characteristics & IMAGE_SCN_MEM_READ) {
protect = PAGE_READONLY;
}
if (ptmp->Characteristics & IMAGE_SCN_MEM_WRITE) {
protect = PAGE_READWRITE;
}
if (ptmp->Characteristics & IMAGE_SCN_MEM_EXECUTE) {
if (protect & PAGE_READONLY) {
protect = PAGE_EXECUTE_READ;
}
else if (protect & PAGE_READWRITE) {
protect = PAGE_EXECUTE_READWRITE;
}
else {
protect = PAGE_EXECUTE;
}
}
if (!VirtualProtect((LPVOID)(ptmp->VirtualAddress + (DWORD)mi.lpBaseOfDll),
ptmp->SizeOfRawData, protect, &oldProtect)) {
printf("Set memory protection failed, error: %d/n", GetLastError());
return FALSE;
}
#endif
DebugPrint("%-8s" /
"0x%x/t" /
"0x%x/t" /
"0x%x/t" /
"0x%x/t" /
"0x%x/t" /
"0x%x/t" /
"0x%x/t" /
"0x%x/n",
name,
ptmp->VirtualAddress,
ptmp->SizeOfRawData,
ptmp->PointerToRawData,
ptmp->PointerToRelocations,
ptmp->PointerToLinenumbers,
ptmp->NumberOfRelocations,
ptmp->NumberOfLinenumbers,
ptmp->Characteristics);
}
return TRUE;
}
BOOL FixupResource(PIMAGE_RESOURCE_DIRECTORY pRes, DWORD imagebase, int offsetRlc)
{
PIMAGE_RESOURCE_DIRECTORY_ENTRY pEntry;
DWORD nEntries;
nEntries = pRes->NumberOfIdEntries + pRes->NumberOfNamedEntries;
pEntry = (PIMAGE_RESOURCE_DIRECTORY_ENTRY)((DWORD)pRes + sizeof(IMAGE_RESOURCE_DIRECTORY));
for (DWORD i = 0; i < nEntries; ++i, ++pEntry) {
if (IMAGE_RESOURCE_DATA_IS_DIRECTORY & pEntry->OffsetToData) {
PIMAGE_RESOURCE_DIRECTORY pRes2;
PIMAGE_RESOURCE_DIRECTORY_ENTRY pEntry2;
DWORD nEntries2;
pRes2 = (PIMAGE_RESOURCE_DIRECTORY)((DWORD)pRes
+ (~IMAGE_RESOURCE_DATA_IS_DIRECTORY & pEntry->OffsetToData));
nEntries2 = pRes2->NumberOfIdEntries + pRes2->NumberOfNamedEntries;
pEntry2 = (PIMAGE_RESOURCE_DIRECTORY_ENTRY)((DWORD)pRes2 + sizeof(IMAGE_RESOURCE_DIRECTORY));
for (DWORD j = 0; j < nEntries2; ++j, ++pEntry2) {
if (IMAGE_RESOURCE_NAME_IS_STRING & pEntry2->Name) {
PIMAGE_RESOURCE_DIR_STRING_U pDirStr;
pDirStr = (PIMAGE_RESOURCE_DIR_STRING_U)((DWORD)pRes
+ (~IMAGE_RESOURCE_NAME_IS_STRING & pEntry2->Name));
}
if (IMAGE_RESOURCE_DATA_IS_DIRECTORY & pEntry2->OffsetToData) {
PIMAGE_RESOURCE_DIRECTORY pRes3;
PIMAGE_RESOURCE_DIRECTORY_ENTRY pEntry3;
DWORD nEntries3;
pRes3 = (PIMAGE_RESOURCE_DIRECTORY)((DWORD)pRes
+ (~IMAGE_RESOURCE_DATA_IS_DIRECTORY & pEntry2->OffsetToData));
nEntries3 = pRes3->NumberOfIdEntries + pRes3->NumberOfNamedEntries;
pEntry3 = (PIMAGE_RESOURCE_DIRECTORY_ENTRY)((DWORD)pRes3 + sizeof(IMAGE_RESOURCE_DIRECTORY));
for (DWORD k = 0; k < nEntries3; ++k) {
PIMAGE_RESOURCE_DATA_ENTRY pData;
assert(~IMAGE_RESOURCE_DATA_IS_DIRECTORY & pEntry3->OffsetToData);
pData = (PIMAGE_RESOURCE_DATA_ENTRY)((DWORD)pRes + pEntry3->OffsetToData);
pData->OffsetToData += (DWORD)imagebase;
}
}
}
}
}
return TRUE;
}
BOOL RelocPeModule(PIMAGE_BASE_RELOCATION pBlc, DWORD imagebase, int offsetRlc)
{
DWORD vaddr, count, offset, type;
WORD *items = NULL;
while (NULL != pBlc->VirtualAddress) {
vaddr = imagebase + pBlc->VirtualAddress;
count = (pBlc->SizeOfBlock - sizeof(IMAGE_BASE_RELOCATION)) >> 1;
items = (WORD *)((char *)pBlc + sizeof(IMAGE_BASE_RELOCATION));
for (DWORD i = 0; i < count; ++i) {
offset = items[i] & 0x0fff;
type = items[i] >> 12;
if (type == 3) {
*(DWORD *)(vaddr + offset) += offsetRlc;
}
}
pBlc = (PIMAGE_BASE_RELOCATION)(items + count);
}
return TRUE;
}
BOOL FixupExport(PIMAGE_EXPORT_DIRECTORY pExp, DWORD imagebase)
{
return TRUE;
}
BOOL FixupImport(PIMAGE_IMPORT_DESCRIPTOR pImp, DWORD imagebase)
{
PIMAGE_THUNK_DATA pOrgThunk, pFirstThunk;
PIMAGE_IMPORT_BY_NAME pImportName;
DebugPrint("/n/n------------import table info------------/n");
while (NULL != pImp->OriginalFirstThunk) {
pImp->Name += imagebase;
DebugPrint("DLL: %s/n", pImp->Name);
FARPROC fpFun;
HINSTANCE hInstance = LoadLibraryA((LPCSTR)pImp->Name);
if (NULL == hInstance) {
printf("Load library %s failed, error: %d/n", pImp->Name, GetLastError());
return FALSE;
}
pOrgThunk = (PIMAGE_THUNK_DATA)(imagebase + pImp->OriginalFirstThunk);
pFirstThunk = (PIMAGE_THUNK_DATA)(imagebase + pImp->FirstThunk);
while (NULL != *(DWORD *)pOrgThunk) {
if (pOrgThunk->u1.Ordinal & IMAGE_ORDINAL_FLAG32) {
fpFun = GetProcAddress(hInstance, (LPCSTR)(pOrgThunk->u1.Ordinal & 0x0000ffff));
//DebugPrint("/t0x%x/n", pOrgThunk->u1.Ordinal);
}
else {
pImportName = (PIMAGE_IMPORT_BY_NAME)(imagebase + pOrgThunk->u1.AddressOfData);
fpFun = GetProcAddress(hInstance, (LPCSTR)pImportName->Name);
//DebugPrint("/t%s/n", pImportName->Name);
}
//DebugPrint("/t/t0x%x/n", fpFun);
pFirstThunk->u1.Ordinal = (LONG)fpFun;
++pFirstThunk;
++pOrgThunk;
}
FreeLibrary(hInstance);
++pImp;
}
return TRUE;
}
int LoadPeModule(const char * name, int argc, _TCHAR* argv[])
{
CLocalFile lf(name);
LPVOID addr;
PeInfo pe;
MODULEINFO mi;
/* 验证是否为合法的pe文件 */
assert(IsPEFile(lf));
/* 处理nt header，获取pe文件的相关信息 */
ParseNTHeader(lf, pe);
/*为image按照imageBase优先原则分配空间地址。
*如该空间地址已被reserved或commit，则重新分配一个可用的空间地址，
*但此种情况下需要做基址重定位处理。*/
addr = VirtualAlloc((LPVOID)(pe.imageBase),
pe.imageSize,
MEM_RESERVE | MEM_COMMIT,
PAGE_EXECUTE_READWRITE);
if (NULL == addr) {
printf("VirtualAlloc failed, error: %d/n", GetLastError());
addr = VirtualAlloc(NULL, pe.imageSize, MEM_RESERVE | MEM_COMMIT, PAGE_EXECUTE_READWRITE);
if (NULL == addr) {
printf("VirtualAlloc failed, error: %d/n", GetLastError());
return -1;
}
}
memset((void *)addr, 0, pe.imageSize);
mi.EntryPoint = (LPVOID)pe.entryPoint;
mi.lpBaseOfDll = (LPVOID)addr;
mi.SizeOfImage = pe.imageSize;
/* 把sections加载到内存 */
LoadSections(lf, pe, mi);
/* 如果实际分配的空间地址和pe文件的基址不一样，则需要做基址重定位处理 */
if ((int)mi.lpBaseOfDll != pe.imageBase) {
if (0 == pe.relocSize) {
printf("Cannot reloc address!/n");
return -1;
}
PIMAGE_BASE_RELOCATION pBrlc = (PIMAGE_BASE_RELOCATION)((DWORD)mi.lpBaseOfDll + pe.relocRva);
RelocPeModule(pBrlc, (DWORD)mi.lpBaseOfDll, (DWORD)mi.lpBaseOfDll - pe.imageBase);
}
/* 如果该pe文件有导出表，则处理导出表区段 */
if (0 != pe.exSize) {
PIMAGE_EXPORT_DIRECTORY pExp = (PIMAGE_EXPORT_DIRECTORY)((DWORD)mi.lpBaseOfDll + pe.exRva);
FixupExport(pExp, (DWORD)mi.lpBaseOfDll);
}
/* 如果pe文件有资源文件，则需要处理资源区段 */
if (0 != pe.resSize) {
PIMAGE_RESOURCE_DIRECTORY pRes = (PIMAGE_RESOURCE_DIRECTORY)((DWORD)mi.lpBaseOfDll + pe.resRva);
FixupResource(pRes, (DWORD)mi.lpBaseOfDll, (DWORD)mi.lpBaseOfDll - pe.imageBase);
}
/* 如果pe文件有导入表，则需要处理导入表区段 */
if (0 != pe.imSize) {
PIMAGE_IMPORT_DESCRIPTOR pImp = (PIMAGE_IMPORT_DESCRIPTOR)((DWORD)mi.lpBaseOfDll + pe.imRva);
FixupImport(pImp, (DWORD)mi.lpBaseOfDll);
}
DebugPrint("/n/nentry: 0x%x/n/n", (DWORD)mi.EntryPoint + (DWORD)mi.lpBaseOfDll);
/* 进入该pe文件的entry pointer，执行该pe文件 */
__asm {
push argc;
push argv;
mov eax, mi.EntryPoint;
add eax, mi.lpBaseOfDll;
call eax;
}
}
int _tmain(int argc, _TCHAR* argv[])
{
//LoadPeModule("HelloWorld.exe", argc - 1, argv + 1);
LoadPeModule("btnlook.exe", argc - 1, argv + 1);
return 0;
}
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