这段程序是从龚俊S3C44BO_BIOS中的一个小段程序,实在是看不懂,那位能分析下???
if((prog_begin==0)&&overwrite0) {
unsigned int ins;
ins = *(unsigned int *)data_begin;
if((ins>>24)==0xea) // instruction: b xxxx, now just support b instruction!!!
bios_load_addr = ((ins&0xffffff)<<2)+8;
else
bios_load_addr = 4; // other instruction, jump to 4
bios_load_addr = (bios_load_addr-BIOS_LOAD-8)/4;
bios_load_addr = (bios_load_addr&0xffffff)|0xea000000;
*(unsigned int *)data_begin = 0xea000000+(BIOS_BASE-8)/4;
modify_a0 = 1;
}
cache_cfg = rNCACHBE0;
rNCACHBE0 = 0x20000000;
SectorProg(prog_begin, (unsigned short *)data_begin, size);
if(modify_a0) {
size = FlashSector(size-1)+SECTOR_SIZE;
FlashRead(FlashSector(BIOS_LOAD), (unsigned short *)(DFT_DOWNLOAD_ADDR+size), SECTOR_SIZE);
*(unsigned int *)(DFT_DOWNLOAD_ADDR+size+SECTOR_SIZE-4) = bios_load_addr;
SectorProg(FlashSector(BIOS_LOAD), (unsigned short *)(DFT_DOWNLOAD_ADDR+size), SECTOR_SIZE);
}
rNCACHBE0 = cache_cfg;
}
对if(modify_a0) {
size = FlashSector(size-1)+SECTOR_SIZE;
FlashRead(FlashSector(BIOS_LOAD), (unsigned short *)(DFT_DOWNLOAD_ADDR+size), SECTOR_SIZE);
*(unsigned int *)(DFT_DOWNLOAD_ADDR+size+SECTOR_SIZE-4) = bios_load_addr;
SectorProg(FlashSector(BIOS_LOAD), (unsigned short *)(DFT_DOWNLOAD_ADDR+size), SECTOR_SIZE);
}
这一段实在是不明白. *(unsigned int *)(DFT_DOWNLOAD_ADDR+size+SECTOR_SIZE-4) = bios_load_addr;
放一条跳转指令.跳去那里?
BIOS_LOAD这个地址是怎样来的??
各位解释下,实在是看不懂. |
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