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grub_err_tgrub_cmd_initrd (grub_command_t cmd __attribute__ ((unused)),		 int argc, char *argv[]){	struct linux_kernel_header *lh;		/* 打开initrd并计算其需要的页面 */	file = grub_file_open (argv[0]);	size = grub_file_size (file);	initrd_pages = (page_align (size) >> 12);		/* 计算initrd加载地址 */	lh = (struct linux_kernel_header *) real_mode_mem;	/* Get the highest address available for the initrd.  */	if (grub_le_to_cpu16 (lh->version) >= 0x0203)    {      addr_max = grub_cpu_to_le32 (lh->initrd_addr_max);    }	addr_max -= 0x10000;	/* Usually, the compression ratio is about 50%.  */	addr_min = (grub_addr_t) prot_mode_target + ((prot_mode_pages * 3) << 12)				+ page_align (size);	/* Put the initrd as high as possible, 4KiB aligned.  */	addr = (addr_max - size) & ~0xFFF;		/* 分配空间 */	grub_relocator_chunk_t ch;    err = grub_relocator_alloc_chunk_align (relocator, &ch,					    addr_min, addr, size, 0x1000,					    GRUB_RELOCATOR_PREFERENCE_HIGH);    initrd_mem = get_virtual_current_address (ch);    initrd_mem_target = get_physical_target_address (ch);		/* 读取initrd到缓存 */	grub_file_read (file, initrd_mem, size) != size		lh->ramdisk_image = initrd_mem_target;	lh->ramdisk_size = size;	lh->root_dev = 0x0100; }

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