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

eboot.bin和eboot.nb0的差别就是
eboot.bin中没有填充pTOC结构体,必须使用parser解释器[类似于romimage.exe luther.gliethttp]将全局变量数据段解压释放到运行时使用的地址才行,
eboot.nb0中经过romimage.exe填充了pTOC结构体,所以eboot.nb0可以自己将自己用到的全局量通过KernelRelocate()函数进行解压释放,这就是为什么
eboot.nb0比eboot.bin的size大的原因[luther.gliethttp].

eboot.nb0是一个包含全局变量初始化pTOC结构体的文件,所以当eboot.nb0启动时就可以通过BootloaderMain()==>KernelRelocate(pTOC)来
实现eboot.nb0自己初始化自己定义的全局变量的工作,其实KernelRelocate就相当于ADS启动汇编中对如下四个section的操作：[luther.gliethttp]
Image$$RO$$Limit
Image$$RW$$Base
Image$$ZI$$Base
Image$$ZI$$Limit
但是我们在源程序中只能找到pTOC的定义ROMHDR * volatile const pTOC = (ROMHDR *)-1;根本找不到对它进行赋值的任何操作,无论是.s汇编还是任何宏中,
那pTOC又是从哪里得到了有效的数值的呢？这就是我们下面继续讨论的问题,一切疑惑都可以从romimage.exe中获得答案.[luther.gliethttp]

romimage.exe源码位于WINCE500/PRIVATE/WINCEOS/COREOS/NK/TOOLS/ROMIMAGE/ROMIMAGE目录下,
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"){
//我们在eboot源码PLATFORM/SMDK2440A/Src/Bootloader/Eboot_usb/blcommon.c中定义了该符号,如下:

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

//记录pTOC指针所在位置[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代码定义的非0值全局变量[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);//将romimage.exe计算后的toc起始地址存入pTOC 指针所在处,这样eboot.nb0中的pTOC指针就指向了romhdr_offset这个有效空间[luther.gliethttp].

    ...
}
初始化c代码定义的非0值全局变量[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;//等效于eboot.nb0中执行pTOC = (void*)addr;[luther.gliethttp]

}

来看看eboot.nb0是怎么使用pTOC来初始化eboot.bin定义的全局变量的:
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

    // 就像这句话描述的一样,只有执行完该函数之后,全局变量所在地址处才有了真实的全局变量数值,

    // 所以只有执行完该函数之后,我们才能够访问全局变量[luther.gliethttp]

    for (loop = 0; loop < pTOC->ulCopyEntries; loop++)
    {
//ulCopyOffset为若干个COPYentry结构体的内存偏移地址

//COPYentry为全局变量描述结构体

//其中ulDest为全局变量被使用时的目的地址

//其中ulSource为全局变量被压缩存储在ROM中的起始地址

//其中ulCopyLen为全局变量真实个数长度

//其中ulDestLen为期望全局变量长度

//ulDestLen一定>=ulCopyLen

//如果ulDestLen大于ulCopyLen,那么说明,该region的全局变量除了有非0数据之外

//还存在ulDestLen减去ulCopyLen字节的清0数据空间[lutehr.gliethttp]

//其实KernelRelocate就相当于ADS中如下汇编代码:

/* 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代码定义的非0值全局变量[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代码未定义的全局变量或者强行指定为0值的全局变量[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);
}