mkcramfs.c

嵌入式文件系统 cramfs 用于linux 开发

	printf("%c %04o %s %5d:%-3d %s\n",
	       type, e->mode & ~S_IFMT, info, e->uid, e->gid, e->name);
}

/*
 * We do a width-first printout of the directory
 * entries, using a stack to remember the directories
 * we've seen.
 */
static unsigned int write_directory_structure(struct entry *entry, char *base, unsigned int offset)
{
	int stack_entries = 0;
	int stack_size = 64;
	struct entry **entry_stack;

	entry_stack = malloc(stack_size * sizeof(struct entry *));
	if (!entry_stack) {
		die(MKFS_ERROR, 1, "malloc failed");
	}

	if (opt_verbose) {
		printf("root:\n");
	}

	for (;;) {
		int dir_start = stack_entries;
		while (entry) {
			struct cramfs_inode *inode = (struct cramfs_inode *) (base + offset);
			size_t len = strlen(entry->name);

			entry->dir_offset = offset;

			inode->mode = entry->mode;
			inode->uid = entry->uid;
			inode->gid = entry->gid;
			inode->size = entry->size;
			inode->offset = 0;
			/* Non-empty directories, regfiles and symlinks will
			   write over inode->offset later. */

			offset += sizeof(struct cramfs_inode);
			total_nodes++;	/* another node */
			memcpy(base + offset, entry->name, len);
			/* Pad up the name to a 4-byte boundary */
			while (len & 3) {
				*(base + offset + len) = '\0';
				len++;
			}
			inode->namelen = len >> 2;
			offset += len;

			if (opt_verbose)
				print_node(entry);

			if (entry->child) {
				if (stack_entries >= stack_size) {
					stack_size *= 2;
					entry_stack = realloc(entry_stack, stack_size * sizeof(struct entry *));
					if (!entry_stack) {
						die(MKFS_ERROR, 1, "realloc failed");
					}
				}
				entry_stack[stack_entries] = entry;
				stack_entries++;
			}
			entry = entry->next;
		}

		/*
		 * Reverse the order the stack entries pushed during
		 * this directory, for a small optimization of disk
		 * access in the created fs.  This change makes things
		 * `ls -UR' order.
		 */
		{
			struct entry **lo = entry_stack + dir_start;
			struct entry **hi = entry_stack + stack_entries;
			struct entry *tmp;

			while (lo < --hi) {
				tmp = *lo;
				*lo++ = *hi;
				*hi = tmp;
			}
		}

		/* Pop a subdirectory entry from the stack, and recurse. */
		if (!stack_entries)
			break;
		stack_entries--;
		entry = entry_stack[stack_entries];

		set_data_offset(entry, base, offset);
		if (opt_verbose) {
			printf("%s:\n", entry->name);
		}
		entry = entry->child;
	}
	free(entry_stack);
	return offset;
}

static int is_zero(char const *begin, unsigned len)
{
	/* Returns non-zero iff the first LEN bytes from BEGIN are all NULs. */
	return (len-- == 0 ||
		(begin[0] == '\0' &&
		 (len-- == 0 ||
		  (begin[1] == '\0' &&
		   (len-- == 0 ||
		    (begin[2] == '\0' &&
		     (len-- == 0 ||
		      (begin[3] == '\0' &&
		       memcmp(begin, begin + 4, len) == 0))))))));
}

/*
 * One 4-byte pointer per block and then the actual blocked
 * output. The first block does not need an offset pointer,
 * as it will start immediately after the pointer block;
 * so the i'th pointer points to the end of the i'th block
 * (i.e. the start of the (i+1)'th block or past EOF).
 *
 * Note that size > 0, as a zero-sized file wouldn't ever
 * have gotten here in the first place.
 */
static unsigned int do_compress(char *base, unsigned int offset, char const *name, char *uncompressed, unsigned int size)
{
	unsigned long original_size = size;
	unsigned long original_offset = offset;
	unsigned long new_size;
	unsigned long blocks = (size - 1) / blksize + 1;
	unsigned long curr = offset + 4 * blocks;
	int change;

	total_blocks += blocks;

	do {
		unsigned long len = 2 * blksize;
		unsigned int input = size;
		int err;

		if (input > blksize)
			input = blksize;
		size -= input;
		if (!(opt_holes && is_zero (uncompressed, input))) {
			err = compress2(base + curr, &len, uncompressed, input, Z_BEST_COMPRESSION);
			if (err != Z_OK) {
				die(MKFS_ERROR, 0, "compression error: %s", zError(err));
			}
			curr += len;
		}
		uncompressed += input;

		if (len > blksize*2) {
			/* (I don't think this can happen with zlib.) */
			die(MKFS_ERROR, 0, "AIEEE: block \"compressed\" to > 2*blocklength (%ld)", len);
		}

		*(u32 *) (base + offset) = curr;
		offset += 4;
	} while (size);

	curr = (curr + 3) & ~3;
	new_size = curr - original_offset;
	/* TODO: Arguably, original_size in these 2 lines should be
	   st_blocks * 512.  But if you say that then perhaps
	   administrative data should also be included in both. */
	change = new_size - original_size;
	if (opt_verbose > 1) {
		printf("%6.2f%% (%+d bytes)\t%s\n",
		       (change * 100) / (double) original_size, change, name);
	}

	return curr;
}


/*
 * Traverse the entry tree, writing data for every item that has
 * non-null entry->compressed (i.e. every symlink and non-empty
 * regfile).
 */
static unsigned int write_data(struct entry *entry, char *base, unsigned int offset)
{
	do {
		if (entry->uncompressed) {
			if (entry->same) {
				set_data_offset(entry, base, entry->same->offset);
				entry->offset = entry->same->offset;
			}
			else {
				set_data_offset(entry, base, offset);
				entry->offset = offset;
				offset = do_compress(base, offset, entry->name, entry->uncompressed, entry->size);
			}
		}
		else if (entry->child)
			offset = write_data(entry->child, base, offset);
		entry=entry->next;
	} while (entry);
	return offset;
}

static unsigned int write_file(char *file, char *base, unsigned int offset)
{
	int fd;
	char *buf;

	fd = open(file, O_RDONLY);
	if (fd < 0) {
		die(MKFS_ERROR, 1, "open failed: %s", file);
	}
	buf = mmap(NULL, image_length, PROT_READ, MAP_PRIVATE, fd, 0);
	if (buf == MAP_FAILED) {
		die(MKFS_ERROR, 1, "mmap failed");
	}
	memcpy(base + offset, buf, image_length);
	munmap(buf, image_length);
	close (fd);
	/* Pad up the image_length to a 4-byte boundary */
	while (image_length & 3) {
		*(base + offset + image_length) = '\0';
		image_length++;
	}
	return (offset + image_length);
}

int main(int argc, char **argv)
{
	struct stat st;		/* used twice... */
	struct entry *root_entry;
	char *rom_image;
	ssize_t offset, written;
	int fd;
	/* initial guess (upper-bound) of required filesystem size */
	loff_t fslen_ub = sizeof(struct cramfs_super);
	char const *dirname, *outfile;
	u32 crc;
	int c;			/* for getopt */
	char *ep;		/* for strtoul */

	total_blocks = 0;

	if (argc)
		progname = argv[0];

	/* command line options */
	while ((c = getopt(argc, argv, "hEe:i:n:psvz")) != EOF) {
		switch (c) {
		case 'h':
			usage(MKFS_OK);
		case 'E':
			opt_errors = 1;
			break;
		case 'e':
			errno = 0;
			opt_edition = strtoul(optarg, &ep, 10);
			if (errno || optarg[0] == '\0' || *ep != '\0')
				usage(MKFS_USAGE);
			break;
		case 'i':
			opt_image = optarg;
			if (lstat(opt_image, &st) < 0) {
				die(MKFS_ERROR, 1, "lstat failed: %s", opt_image);
			}
			image_length = st.st_size; /* may be padded later */
			fslen_ub += (image_length + 3); /* 3 is for padding */
			break;
		case 'n':
			opt_name = optarg;
			break;
		case 'p':
			opt_pad = PAD_SIZE;
			fslen_ub += PAD_SIZE;
			break;
		case 's':
			/* old option, ignored */
			break;
		case 'v':
			opt_verbose++;
			break;
		case 'z':
			opt_holes = 1;
			break;
		}
	}

	if ((argc - optind) != 2)
		usage(MKFS_USAGE);
	dirname = argv[optind];
	outfile = argv[optind + 1];

	if (stat(dirname, &st) < 0) {
		die(MKFS_USAGE, 1, "stat failed: %s", dirname);
	}
	fd = open(outfile, O_WRONLY | O_CREAT | O_TRUNC, 0666);
	if (fd < 0) {
		die(MKFS_USAGE, 1, "open failed: %s", outfile);
	}

	root_entry = calloc(1, sizeof(struct entry));
	if (!root_entry) {
		die(MKFS_ERROR, 1, "calloc failed");
	}
	root_entry->mode = st.st_mode;
	root_entry->uid = st.st_uid;
	root_entry->gid = st.st_gid;

	root_entry->size = parse_directory(root_entry, dirname, &root_entry->child, &fslen_ub);

	/* always allocate a multiple of blksize bytes because that's
	   what we're going to write later on */
	fslen_ub = ((fslen_ub - 1) | (blksize - 1)) + 1;

	if (fslen_ub > MAXFSLEN) {
		fprintf(stderr,
			"warning: estimate of required size (upper bound) is %LdMB, but maximum image size is %uMB, we might die prematurely\n",
			fslen_ub >> 20,
			MAXFSLEN >> 20);
		fslen_ub = MAXFSLEN;
	}

	/* find duplicate files. TODO: uses the most inefficient algorithm
	   possible. */
	eliminate_doubles(root_entry,root_entry);

	/* TODO: Why do we use a private/anonymous mapping here
	   followed by a write below, instead of just a shared mapping
	   and a couple of ftruncate calls?  Is it just to save us
	   having to deal with removing the file afterwards?  If we
	   really need this huge anonymous mapping, we ought to mmap
	   in smaller chunks, so that the user doesn't need nn MB of
	   RAM free.  If the reason is to be able to write to
	   un-mmappable block devices, then we could try shared mmap
	   and revert to anonymous mmap if the shared mmap fails. */
	rom_image = mmap(NULL, fslen_ub?fslen_ub:1, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);

	if (rom_image == MAP_FAILED) {
		die(MKFS_ERROR, 1, "mmap failed");
	}

	/* Skip the first opt_pad bytes for boot loader code */
	offset = opt_pad;
	memset(rom_image, 0x00, opt_pad);

	/* Skip the superblock and come back to write it later. */
	offset += sizeof(struct cramfs_super);

	/* Insert a file image. */
	if (opt_image) {
		printf("Including: %s\n", opt_image);
		offset = write_file(opt_image, rom_image, offset);
	}

	offset = write_directory_structure(root_entry->child, rom_image, offset);
	printf("Directory data: %d bytes\n", offset);

	offset = write_data(root_entry, rom_image, offset);

	/* We always write a multiple of blksize bytes, so that
	   losetup works. */
	offset = ((offset - 1) | (blksize - 1)) + 1;
	printf("Everything: %d kilobytes\n", offset >> 10);

	/* Write the superblock now that we can fill in all of the fields. */
	write_superblock(root_entry, rom_image+opt_pad, offset);
	printf("Super block: %d bytes\n", sizeof(struct cramfs_super));

	/* Put the checksum in. */
	crc = crc32(0L, Z_NULL, 0);
	crc = crc32(crc, (rom_image+opt_pad), (offset-opt_pad));
	((struct cramfs_super *) (rom_image+opt_pad))->fsid.crc = crc;
	printf("CRC: %x\n", crc);

	/* Check to make sure we allocated enough space. */
	if (fslen_ub < offset) {
		die(MKFS_ERROR, 0, "not enough space allocated for ROM image (%Ld allocated, %d used)", fslen_ub, offset);
	}

	written = write(fd, rom_image, offset);
	if (written < 0) {
		die(MKFS_ERROR, 1, "write failed");
	}
	if (offset != written) {
		die(MKFS_ERROR, 0, "ROM image write failed (wrote %d of %d bytes)", written, offset);
	}

	/* (These warnings used to come at the start, but they scroll off the
	   screen too quickly.) */
	if (warn_namelen)
		fprintf(stderr, /* bytes, not chars: think UTF-8. */
			"warning: filenames truncated to %d bytes (possibly less if multi-byte UTF-8)\n",
			CRAMFS_MAXPATHLEN);
	if (warn_skip)
		fprintf(stderr, "warning: files were skipped due to errors\n");
	if (warn_size)
		fprintf(stderr,
			"warning: file sizes truncated to %luMB (minus 1 byte)\n",
			1L << (CRAMFS_SIZE_WIDTH - 20));
	if (warn_uid) /* (not possible with current Linux versions) */
		fprintf(stderr,
			"warning: uids truncated to %u bits (this may be a security concern)\n",
			CRAMFS_UID_WIDTH);
	if (warn_gid)
		fprintf(stderr,
			"warning: gids truncated to %u bits (this may be a security concern)\n",
			CRAMFS_GID_WIDTH);
	if (warn_dev)
		fprintf(stderr,
			"WARNING: device numbers truncated to %u bits (this almost certainly means\n"
			"that some device files will be wrong)\n",
			CRAMFS_OFFSET_WIDTH);
	if (opt_errors &&
	    (warn_namelen||warn_skip||warn_size||warn_uid||warn_gid||warn_dev))
		exit(MKFS_ERROR);

	exit(MKFS_OK);
}

/*
 * Local variables:
 * c-file-style: "linux"
 * End:
 */