CE5.0 - romimage.exe如何填充eboot.bin中的pTOC特殊指針生成.nb0

eboot.bin和eboot.nb0的差別就是
eboot.bin中沒有填充pTOC結構體,必須使用parser解釋器[類似於romimage.exe luther.gliethttp]將全局變量數據段解壓釋放到運行時使用的地址才行,
eboot.nb0中經過romimage.exe填充了pTOC結構體,所以eboot.nb0可以自己將自己用到的全局量通過KernelRelocate()函數進行解壓釋放,這就是爲什麼
eboot.nb0比eboot.bin的size大的原因[luther.gliethttp].

eboot.nb0是一個包含全局變量初始化pTOC結構體的文件,所以當eboot.nb0啓動時就可以通過BootloaderMain()==>KernelRelocate(pTOC)來
實現eboot.nb0自己初始化自己定義的全局變量的工作,其實KernelRelocate就相當於ADS啓動彙編中對如下四個section的操作：[luther.gliethttp]
Image$$RO$$Limit
Image$$RW$$Base
Image$$ZI$$Base
Image$$ZI$$Limit
但是我們在源程序中只能找到pTOC的定義ROMHDR * volatile const pTOC = (ROMHDR *)-1;根本找不到對它進行賦值的任何操作,無論是.s彙編還是任何宏中,
那pTOC又是從哪裏得到了有效的數值的呢？這就是我們下面繼續討論的問題,一切疑惑都可以從romimage.exe中獲得答案.[luther.gliethttp]

romimage.exe源碼位於WINCE500/PRIVATE/WINCEOS/COREOS/NK/TOOLS/ROMIMAGE/ROMIMAGE目錄下,
C:/WINCE500/PRIVATE/WINCEOS/COREOS/NK/TOOLS/ROMIMAGE/ROMIMAGE/module.cpp|118| if(token == "pTOC"){
void Module::check_special_symbol(string token, DWORD o32_section, DWORD offset, MemoryList &memory_list){
    ...
    if(is_kernel()){
        if(token == "pTOC"){
//我們在eboot源碼PLATFORM/SMDK2440A/Src/Bootloader/Eboot_usb/blcommon.c中定義了該符號,如下:

//ROMHDR * volatile const pTOC = (ROMHDR *)-1; // Gets replaced by RomLoader with real address

//記錄pTOC指針所在位置[luther.gliethttp]

          m_TOC_offset = offset + m_load_offset; // doesn't get load offset added, because only compared with rva later

          LAST_PASS_PRINT printf("Found pTOC at %08x/n", m_TOC_offset);
        }
        if(needs_signing()){
          if(token == "OEMIoControl")
            s_oem_io_control = offset + m_初始化c代碼定義的非0值全局變量[luther.gliethttp]load_offset - page_size();
        }
        ...
    }
    ...
}

bin.cpp|87| kernel->write_TOC_ptr(romhdr_offset);
bool write_bin(AddressList &hole_list, CopyList &copy_list,
                ModuleList &module_list, FileList &file_list,
                MemoryList &memory_list, MemoryList &reserve_list,
                ModuleList::iterator &kernel, Config &config, MemoryList::iterator xip_mem){
    ...
    // write toc into kernel

    if(xip_mem->is_kernel() && kernel->is_kernel())
        kernel->write_TOC_ptr(romhdr_offset);//將romimage.exe計算後的toc起始地址存入pTOC 指針所在處,這樣eboot.nb0中的pTOC指針就指向了romhdr_offset這個有效空間[luther.gliethttp].

    ...
}
初始化c代碼定義的非0值全局變量[luther.gliethttp]
void Module::write_TOC_ptr(DWORD addr){
  assert(is_kernel());

  if(!m_TOC_offset){
    fprintf(stderr, "Error: Found NULL or missing TOC pointer for %s/n", m_name.c_str());
    exit(1);
  }
 
// *(DWORD *)(m_o32_list[0].data.ptr() + m_TOC_offset - page_size()) = addr;

  *(DWORD *)rva2ptr(m_TOC_offset) = addr;//等效於eboot.nb0中執行pTOC = (void*)addr;[luther.gliethttp]

}

來看看eboot.nb0是怎麼使用pTOC來初始化eboot.bin定義的全局變量的:
main
==>BootloaderMain()
==>KernelRelocate(pTOC)
typedef struct COPYentry {
    ULONG ulSource; // copy source address

    ULONG ulDest; // copy destination address

    ULONG ulCopyLen; // copy length

    ULONG ulDestLen; // copy destination length

                                    // (zero fill to end if > ulCopyLen)

} COPYentry;
//

// KernelRelocate: move global variables to RAM

//

static BOOL KernelRelocate (ROMHDR *const pTOC)
{
    ULONG loop;
    COPYentry *cptr;
    if (pTOC == (ROMHDR *const) -1)
    {
        return (FALSE); // spin forever!

    }
    // This is where the data sections become valid... don't read globals until after this

    // 就像這句話描述的一樣,只有執行完該函數之後,全局變量所在地址處纔有了真實的全局變量數值,

    // 所以只有執行完該函數之後,我們才能夠訪問全局變量[luther.gliethttp]

    for (loop = 0; loop < pTOC->ulCopyEntries; loop++)
    {
//ulCopyOffset爲若干個COPYentry結構體的內存偏移地址

//COPYentry爲全局變量描述結構體

//其中ulDest爲全局變量被使用時的目的地址

//其中ulSource爲全局變量被壓縮存儲在ROM中的起始地址

//其中ulCopyLen爲全局變量真實個數長度

//其中ulDestLen爲期望全局變量長度

//ulDestLen一定>=ulCopyLen

//如果ulDestLen大於ulCopyLen,那麼說明,該region的全局變量除了有非0數據之外

//還存在ulDestLen減去ulCopyLen字節的清0數據空間[lutehr.gliethttp]

//其實KernelRelocate就相當於ADS中如下彙編代碼:

/* add r2, pc,#-(8+.-CInitData) ; @ where to read values (relative)
    ldmia r2, {r0, r1, r3, r4}
   
    cmp r0, r1 ; Check that they are different
    beq EndRW
LoopRW 初始化c代碼定義的非0值全局變量[luther.gliethttp]
    cmp r1, r3 ; Copy init data
    ldrcc r2, [r0], #4
    strcc r2, [r1], #4
    bcc LoopRW
EndRW

    mov r2, #0
LoopZI 初始化c代碼未定義的全局變量或者強行指定爲0值的全局變量[luther.gliethttp]
    cmp r3, r4 ; Zero init
    strcc r2, [r3], #4
    bcc LoopZI
 
    b EndInitC
               
CInitData
     IMPORT |Image$$RO$$Limit| ; End of ROM code (=start of ROM data)
    IMPORT |Image$$RW$$Base| ; Base of RAM to initialise
    IMPORT |Image$$ZI$$Base| ; Base and limit of area
    IMPORT |Image$$ZI$$Limit| ; Top of zero init segment
   
    DCD |Image$$RO$$Limit| ; End of ROM code (=start of ROM data)
     DCD |Image$$RW$$Base| ; Base of RAM to initialise
     DCD |Image$$ZI$$Base| ; Base and limit of area
     DCD |Image$$ZI$$Limit| ; Top of zero init segment
*/
        cptr = (COPYentry *)(pTOC->ulCopyOffset + loop*sizeof(COPYentry));
        if (cptr->ulCopyLen)
            memcpy((LPVOID)cptr->ulDest,(LPVOID)cptr->ulSource,cptr->ulCopyLen);
        if (cptr->ulCopyLen != cptr->ulDestLen)
            memset((LPVOID)(cptr->ulDest+cptr->ulCopyLen),0,cptr->ulDestLen-cptr->ulCopyLen);
    }
    return (TRUE);
}