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实现写时复制，读时加载，原理为，申请内存时，只给一段线性地址空间，并不分配物理内存，当cpu读、写该内存时，发生缺页中，或者写错误，中断处理程序根据前面设置的内容，决写分配物理内存，或者是共享内存，如果需要读取文件时，则根据需要读取相应的文件数据。

主要代码如下：

LPPE_FILE_ELEM load_pe_dll(char * lpFileName) {LPPE_FILE_ELEM lpSysFE, lpUserFE; //文件列表中的元素，保存文件信息//文件加载内存的默认地址//PIMAGE_DOS_HEADER pdh; //dos头PIMAGE_NT_HEADERS pnh; 	//pe文件头LPVOID pfile, pKrFile;PMEMORY_BASIC_INFORMATION pmbi;BYTE buf[512]; 		//临时块//补全文件目录路径add_patch((char *) buf, lpFileName);//1、从系统进程中查找是否已经加载lpSysFE = pe_find_file((char*) buf, get_sys_files_list());if (lpSysFE) {//系统中已经加载，进入下一步pKrFile = (LPVOID) lpSysFE->hModule;DbgPrint("dll已读入内存 : %s ,%x\n", lpSysFE->strFilePath,lpSysFE->dwNumberOfShares);//return lpFE->hModule;} else {//将文件加入系统文件列表中lpSysFE = kr_malloc(sizeof(PE_FILE_ELEM) + strlen((char*) buf) + 1);strcpy(lpSysFE->strFilePath, (char*) buf);if (load_file(lpSysFE->strFilePath, 0, 512, buf)) {//新exe头部的文件地址 指向PEpnh = (PIMAGE_NT_HEADERS) ((DWORD) buf+ ((PIMAGE_DOS_HEADER) buf)->e_lfanew);//系统进程中仅申请空间，读时加载pmbi = mem_virtual_alloc(&stMbiSys, 0,pnh->OptionalHeader.SizeOfImage, MEM_COMMIT,PAGE_READWRITE,MEM_IMAGE);pKrFile = (PBYTE) pmbi->BaseAddress;lpSysFE->hModule = (DWORD) pKrFile;lpSysFE->dwImgsize = pnh->OptionalHeader.SizeOfImage;lpSysFE->dwNumberOfShares = 0;list_push(get_sys_files_list(), (PLIST_ELEM) lpSysFE);load_pe_text((PIMAGE_DOS_HEADER) buf, (DWORD) lpSysFE->hModule,lpSysFE->strFilePath);if (!pKrFile) {//失败//DbgPrint("dll已读入内存 : %s ,%x\n");} else {//初始化时设置文件共享的次数为0,加入系统加载文件队列。}}}		//	if (lpFE)//2、检查用户空间 当前文件是否已经加载lpUserFE = pe_find_file(lpSysFE->strFilePath, get_current_file_list());if (lpUserFE) {//2、已经加载 直接返回return lpUserFE;} else {//第一次加入进程，将pKrfile的物理地址映射到 pfilepnh = (PIMAGE_NT_HEADERS) ((((PIMAGE_DOS_HEADER) pKrFile)->e_lfanew)+ (DWORD) pKrFile);pmbi = mem_virtual_alloc(MBI_USER_BASE, (LPVOID) pnh->OptionalHeader.ImageBase,pnh->OptionalHeader.SizeOfImage,MEM_COMMIT, PAGE_READWRITE, MEM_IMAGE);pfile = (PBYTE) pmbi->BaseAddress;DbgPrint("共享 dll: %s,%x,%x,%x,%x\n", lpSysFE->strFilePath, pfile,pKrFile, pnh->OptionalHeader.ImageBase);lpUserFE = kr_malloc(strlen((char*) lpSysFE->strFilePath) + sizeof(PE_FILE_ELEM)+ 1);strcpy(lpUserFE->strFilePath, lpSysFE->strFilePath);lpUserFE->hModule = (DWORD) pfile;lpUserFE->dwImgsize = lpSysFE->dwImgsize;lpUserFE->hSysModule = pKrFile;list_push(get_current_file_list(), (PLIST_ELEM) lpUserFE);lpSysFE->dwNumberOfShares++;DoRelocationTable(pfile);link_import(pfile);//文件头映射//	mem_map_demand(pKrFile, pfile,//		_ALIGN(	pdh->e_lfanew + sizeof(IMAGE_NT_HEADERS32)//					+ pnh->FileHeader.NumberOfSections//								* sizeof(IMAGE_SECTION_HEADER), 4096),//		PG_USER_R_P);}return lpUserFE;
}
BOOL mem_fail_sys(DWORD code, DWORD addr) {DWORD temp;LPPE_FILE_ELEM fe;PMEMORY_BASIC_INFORMATION pmbi =mem_find_mbi(&stMbiSys,addr);//DbgPrint("内核%s错误  0x%x,0x%x,0x%x,0x%x,0x%x,0x%x\n",(code&2?"写":"读"), addr, code,//		pmbi->BaseAddress, pmbi->RegionSize, pmbi->State, pmbi->Type);if (!pmbi) {return FALSE;}//如果是映射if (pmbi->State == MEM_COMMIT) {//分配物理内存,以4K为单位，if (pmbi->Type == MEM_IMAGE) {mem_physics(addr, 4096, PGE_SYS_RW_P);fe = (LPPE_FILE_ELEM) pe_find_from_addr(get_sys_files_list(), addr);if (fe->dwNumberOfShares != 0) {//直接分配内存，再读取文件//200对齐load_file_4k(fe, addr);} else {//正在读文件头}} else if (pmbi->Type == MEM_4MB_PAGES) {// MEM_4MB_PAGES://二级目录//	DbgPrint("二级页表%x，%x\n", addr, (DWORD *) MiGetPteAddress(addr));mem_physics(addr, 4096, PG_USER_RW_P);//*(DWORD *) MiGetPteAddress(addr) =//		get_freed_physics() + PG_USER_RW_P;} else {mem_physics(addr, 4096, PGE_SYS_RW_P);}//直接分配内存}	//if (pmbi->State == MEM_COMMIT)else {return FALSE;}return TRUE;
}
BOOL mem_fail_user(DWORD code, DWORD addr) {DWORD temp;LPPE_FILE_ELEM fe;PMEMORY_BASIC_INFORMATION pmbi =mem_find_mbi(MBI_USER_BASE, addr);//DbgPrint("用户%s错误  0x%x,0x%x,0x%x,0x%x,0x%x,0x%x\n", (code&2?"写":"读"),addr, code,//		pmbi->BaseAddress, pmbi->RegionSize, pmbi->State, pmbi->Type);if (!pmbi) {
//找不分配的段。return FALSE;}
//状态是不是已经提交
//只读，读写，还共享的读写
//如果是map类，分配内存，如果Image类，则读时加载，写时复制if (pmbi->State == MEM_COMMIT) {if (pmbi->Type == MEM_IMAGE) {fe = (LPPE_FILE_ELEM) pe_find_from_addr(get_current_file_list(),addr);if (fe->hSysModule == 0) {//说明是不是共享文件//DbgPrint("用户内存错误  0x%x , 0x%x , 0x%x , 0x%x \n", addr, code,//			pmbi->BaseAddress, pmbi->State);mem_physics(addr, 4096, PG_USER_RW_P);load_file_4k(fe, addr);//break;} else {//DbgPrint("用户内存错误 %x,%x\n",addr,fe);//先读取系统内存，如果出错则会中断到mem_fail_sys，加载文件//如果是读取，则映射，如果是写则分配内存再复制if (code & 2) {//重新申请物理内，再复制//DbgPrint("用户写错误%x\n", addr);mem_physics(addr, 4096, PG_USER_RW_P);memcpy((PVOID) (addr & 0xFFFFF000),(PVOID) ((fe->hSysModule + (addr - fe->hModule))& 0xFFFFF000), 4096);} else {//DbgPrint("用户读错误%x\n", addr);//说明可能内核没有读取文件，也可能没有映射//先试读下，没有读取文件会中断后读取，再映射//mem_fail_sys(0,fe->hSysModule+addr-fe->hModule);temp = *(PDWORD) (fe->hSysModule + addr - fe->hModule);//函数自己内部齐，size=1~4096效果应是一样mem_map_demand(fe->hSysModule + addr - fe->hModule, addr,4096, PG_USER_R_P);}//直接分配内存，再读取文件//addr-pmbi->BaseAddressg}} else if ((pmbi->Type == MEM_PRIVATE)) {//if (pmbi->Type == MEM_IMAGE)mem_physics(addr, 4096, PG_USER_RW_P);}}		//	if (pmbi->State == MEM_COMMIT)else {return FALSE;}return TRUE;
}