ReactOS 源码分析 (三) By:ProgrammeBoy
freeldr.c代码位置: D:/ReactOS/ReactOS_src/boot/freeldr/freeldr/freeldr.c 终于终于看到C语言了,汇编看者就是不爽,先介绍下这个文件,这个文件内的代码很少,基本上是命令参数,文件系统、调试、UI、内存的初始化，最后进行系统的加载。 看代码： #include <freeldr.h> #include <debug.h>
VOID BootMain(LPSTR CmdLine) { /* 命令行分析,经调试命令行的为NULL,所以分析这个函数就没意思了这里略过*/ CmdLineParse(CmdLine); /*这里我们得看下,见下文*/ MachInit(CmdLine); /*这里是文件系统的初始化*/ FsInit(); /*调试初始化,是用串口通信*/ DebugInit(); /*这是我调试时加上的看CmdLine的代码*/ DbgPrintMask( DPRINT_WARNING,"CmdLine:%s/n",CmdLine );
DPRINTM(DPRINT_WARNING,"BootMain() called./n"); /*初始化UI*/ if (!UiInitialize(FALSE)) { UiMessageBoxCritical("Unable to initialize UI./n"); return; } /*初始化内存管理*/ if (!MmInitializeMemoryManager()) { UiMessageBoxCritical("Unable to initialize memory manager"); return; } /*开始加载系统*/ RunLoader(); } 接下来我们就按照上面函数的顺序还分析代码… 首先是MachInit(). archmach.c代码位置: d:/ReactOS/ReactOS_src/boot/freeldr/freeldr/arch/i386/archmach.c VOID MachInit(const char *CmdLine) { ULONG PciId;
memset(&MachVtbl,sizeof(MACHVTBL));
/* Check for Xbox by identifying device at PCI 0:0:0,if it's * 0x10de/0x02a5 then we're running on an Xbox */ WRITE_PORT_ULONG((ULONG*) 0xcf8,CONFIG_CMD(0,0)); PciId = READ_PORT_ULONG((ULONG*) 0xcfc); if (0x02a510de == PciId) { XboxMachInit(CmdLine); } else { PcMachInit (CmdLine); }
HalpCalibrateStallExecution(); } 代码也不多,这里说下结构体MachVtbl,这个结构体看下定义 int (*ConsGetCh)(VOID);
VOID (*VideoClearScreen)(UCHAR Attr); VIDEODISPLAYMODE (*VideoSetDisplayMode)(char *DisplayMode,BOOLEAN Init); VOID (*VideoGetDisplaySize)(PULONG Width,PULONG Height,PULONG Depth); ULONG (*VideoGetBufferSize)(VOID); VOID (*VideoSetTextCursorPosition)(ULONG X,ULONG Y); VOID (*VideoHideShowTextCursor)(BOOLEAN Show); VOID (*VideoPutChar)(int Ch,UCHAR Attr,unsigned X,unsigned Y); VOID (*VideoCopyOffScreenBufferToVRAM)(PVOID Buffer); BOOLEAN (*VideoIsPaletteFixed)(VOID); VOID (*VideoSetPaletteColor)(UCHAR Color,UCHAR Red,UCHAR Green,UCHAR Blue); VOID (*VideoGetPaletteColor)(UCHAR Color,UCHAR* Red,UCHAR* Green,UCHAR* Blue); VOID (*VideoSync)(VOID); VOID (*Beep)(VOID); VOID (*PrepareForReactOS)(IN BOOLEAN Setup);
MEMORY_DESCRIPTOR* (*GetMemoryDescriptor)(MEMORY_DESCRIPTOR* Current); ULONG (*GetMemoryMap)(PBIOS_MEMORY_MAP BiosMemoryMap,ULONG MaxMemoryMapSize);
BOOLEAN (*DiskGetBootVolume)(PULONG DriveNumber,PULONGLONG StartSector,PULONGLONG SectorCount,int *FsType); BOOLEAN (*DiskGetSystemVolume)(char *SystemPath,char *RemainingPath,PULONG Device,PULONG DriveNumber,int *FsType); BOOLEAN (*DiskGetBootPath)(char *BootPath,unsigned Size); VOID (*DiskGetBootDevice)(PULONG BootDevice); BOOLEAN (*DiskBootingFromFloppy)(VOID); BOOLEAN (*DiskNormalizeSystemPath)(char *SystemPath,unsigned Size); BOOLEAN (*DiskReadLogicalSectors)(ULONG DriveNumber,ULONGLONG SectorNumber,ULONG SectorCount,PVOID Buffer); BOOLEAN (*DiskGetPartitionEntry)(ULONG DriveNumber,ULONG PartitionNumber,PPARTITION_TABLE_ENTRY PartitionTableEntry); BOOLEAN (*DiskGetDriveGeometry)(ULONG DriveNumber,PGEOMETRY DriveGeometry); ULONG (*DiskGetCacheableBlockCount)(ULONG DriveNumber);
TIMEINFO* (*GetTime)(VOID); ULONG (*GetRelativeTime)(VOID);
PCONFIGURATION_COMPONENT_DATA (*HwDetect)(VOID); } MACHVTBL,*PMACHVTBL; 看到了没都是些函数的定义,为什么要这么定义呢?是问了可以增加程序的可移植性,为不同的硬件编写不同函数最后把指针赋予这个结构体就OK了。 接下来就是检查是否运行在Xbox虚拟机下,本人没用过,不多说,这里我们也学习到了怎样检测系统是否运行在Xbox下。我是在Vmware下运行的所以在我机子上会调用PcMachInit()函数. 这个函数下面说,最后是调用HalpCalibrateStallExecution()函数,现在还不知道是干什么的? 一个一个接着来 (下面要开启函数介绍的模式啦) machpc.c代码位置: d:/ReactOS/ReactOS_src/boot/freeldr/freeldr/arch/i386/machpc.c 来看函数PcMachInit(); 代码如下: VOID PcMachInit(const char *CmdLine) { EnableA20();
/* Setup vtbl */ MachVtbl.ConsPutChar = PcConsPutChar; MachVtbl.ConsKbHit = PcConsKbHit; MachVtbl.ConsGetCh = PcConsGetCh; MachVtbl.VideoClearScreen = PcVideoClearScreen; MachVtbl.VideoSetDisplayMode = PcVideoSetDisplayMode; MachVtbl.VideoGetDisplaySize = PcVideoGetDisplaySize; MachVtbl.VideoGetBufferSize = PcVideoGetBufferSize; MachVtbl.VideoSetTextCursorPosition = PcVideoSetTextCursorPosition; MachVtbl.VideoSetTextCursorPosition = PcVideoSetTextCursorPosition; MachVtbl.VideoHideShowTextCursor = PcVideoHideShowTextCursor; MachVtbl.VideoPutChar = PcVideoPutChar; MachVtbl.VideoCopyOffScreenBufferToVRAM = PcVideoCopyOffScreenBufferToVRAM; MachVtbl.VideoIsPaletteFixed = PcVideoIsPaletteFixed; MachVtbl.VideoSetPaletteColor = PcVideoSetPaletteColor; MachVtbl.VideoGetPaletteColor = PcVideoGetPaletteColor; MachVtbl.VideoSync = PcVideoSync; MachVtbl.Beep = PcBeep; MachVtbl.PrepareForReactOS = PcPrepareForReactOS; MachVtbl.GetMemoryMap = PcMemGetMemoryMap; MachVtbl.DiskGetBootVolume = DiskGetBootVolume; MachVtbl.DiskGetSystemVolume = DiskGetSystemVolume; MachVtbl.DiskGetBootPath = DiskGetBootPath; MachVtbl.DiskGetBootDevice = DiskGetBootDevice; MachVtbl.DiskBootingFromFloppy = DiskBootingFromFloppy; MachVtbl.DiskNormalizeSystemPath = DiskNormalizeSystemPath; MachVtbl.DiskReadLogicalSectors = PcDiskReadLogicalSectors; MachVtbl.DiskGetPartitionEntry = DiskGetPartitionEntry; MachVtbl.DiskGetDriveGeometry = PcDiskGetDriveGeometry; MachVtbl.DiskGetCacheableBlockCount = PcDiskGetCacheableBlockCount; MachVtbl.GetTime = PcGetTime; MachVtbl.HwDetect = PcHwDetect; } 都是指针呀,现在开启函数介绍模式.一个一个的看,从第一个开始 MachVtbl 函数之 PcConsPutChar()代码位置: d:/ReactOS/ReactOS_src/boot/freeldr/freeldr/arch/i386/pccons.c 函数参数 int Ch 函数返回值: NULL 函数说明:在屏幕上打印字符,主要是调用int 10h实现 Int 10h AH=0Eh MachVtbl 函数之PcConsKbHit代码位置: d:/ReactOS/ReactOS_src/boot/freeldr/freeldr/arch/i386/pccons.c 函数参数:NULL 函数返回值:BOOL 函数说明: CHECK FOR KEYSTROKE 类似于C语言函数getch()主要调用int 16h 实现 Int 16h AH=01h MachVtbl 函数之PcConsGetCh代码位置: d:/ReactOS/ReactOS_src/boot/freeldr/freeldr/arch/i386/pccons.c 函数参数:NULL 函数返回值:int 获得的按键值 函数说明:类似C语言函数的getchar();主要用int 16h实现 Int 16h AH=00h MachVtbl 函数之PcVideoClearScreen代码位置: d:/ReactOS/ReactOS_src/boot/freeldr/freeldr/arch/i386/pcvideo.c 函数参数: UCHAR Attr 函数返回值:NULL 函数说明:清屏函数,即向显示器内存写入数据清屏 代码如下: VOID PcVideoClearScreen(UCHAR Attr) { USHORT AttrChar; USHORT *BufPtr; /* VIDEOTEXT_MEM_ADDRESS 0xB8000*/ AttrChar = ((USHORT) Attr << 8) | ' '; /*填充显存*/ for (BufPtr = (USHORT *) VIDEOTEXT_MEM_ADDRESS; BufPtr < (USHORT *) (VIDEOTEXT_MEM_ADDRESS + VIDEOTEXT_MEM_SIZE); BufPtr++) { *BufPtr = AttrChar; } } MachVtbl 函数之PcVideoSetDisplayMode（编辑：李大同） 【声明】本站内容均来自网络，其相关言论仅代表作者个人观点，不代表本站立场。若无意侵犯到您的权利，请及时与联系站长删除相关内容! |