mkcramfs.c

嵌入式系统设计与实验教材二源码linux内核移植与编译

/*
 * mkcramfs - make a cramfs file system
 *
 * Copyright (C) 1999-2001 Transmeta Corporation
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include <sys/types.h>
#include <stdio.h>
#include <sys/stat.h>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/fcntl.h>
#include <dirent.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <assert.h>
#include <getopt.h>
#include <linux/cramfs_fs.h>
#include <zlib.h>

#define PAD_SIZE 512		/* only 0 and 512 supported by kernel */

static const char *progname = "mkcramfs";

/* N.B. If you change the disk format of cramfs, please update fs/cramfs/README. */

/* Input status of 0 to print help and exit without an error. */
static void usage(int status)
{
	FILE *stream = status ? stderr : stdout;

	fprintf(stream, "usage: %s [-h] [-e edition] [-i file] [-n name] dirname outfile\n"
		" -h         print this help\n"
		" -E         make all warnings errors (non-zero exit status)\n"
		" -e edition set edition number (part of fsid)\n"
		" -i file    insert a file image into the filesystem (requires >= 2.4.0)\n"
		" -n name    set name of cramfs filesystem\n"
		" -p         pad by %d bytes for boot code\n"
		" -s         sort directory entries (old option, ignored)\n"
		" -z         make explicit holes (requires >= 2.3.39)\n"
		" dirname    root of the filesystem to be compressed\n"
		" outfile    output file\n", progname, PAD_SIZE);

	exit(status);
}

#define PAGE_CACHE_SIZE (4096)
/* The kernel assumes PAGE_CACHE_SIZE as block size. */
static unsigned int blksize = PAGE_CACHE_SIZE;
static long total_blocks = 0, total_nodes = 1; /* pre-count the root node */
static int image_length = 0;

/*
 * If opt_holes is set, then mkcramfs can create explicit holes in the
 * data, which saves 26 bytes per hole (which is a lot smaller a
 * saving than most most filesystems).
 *
 * Note that kernels up to at least 2.3.39 don't support cramfs holes,
 * which is why this is turned off by default.
 */
static int opt_edition = 0;
static int opt_errors = 0;
static int opt_holes = 0;
static int opt_pad = 0;
static char *opt_image = NULL;
static char *opt_name = NULL;

static int warn_dev, warn_gid, warn_namelen, warn_skip, warn_size, warn_uid;

#ifndef MIN
# define MIN(_a,_b) ((_a) < (_b) ? (_a) : (_b))
#endif

/* In-core version of inode / directory entry. */
struct entry {
	/* stats */
	char *name;
	unsigned int mode, size, uid, gid;

	/* FS data */
	void *uncompressed;
        /* points to other identical file */
        struct entry *same;
        unsigned int offset;            /* pointer to compressed data in archive */
	unsigned int dir_offset;	/* Where in the archive is the directory entry? */

	/* organization */
	struct entry *child; /* null for non-directories and empty directories */
	struct entry *next;
};

/*
 * The longest file name component to allow for in the input directory tree.
 * Ext2fs (and many others) allow up to 255 bytes.  A couple of filesystems
 * allow longer (e.g. smbfs 1024), but there isn't much use in supporting
 * >255-byte names in the input directory tree given that such names get
 * truncated to 255 bytes when written to cramfs.
 */
#define MAX_INPUT_NAMELEN 255

static int find_identical_file(struct entry *orig,struct entry *newfile)
{
        if(orig==newfile) return 1;
        if(!orig) return 0;
        if(orig->size==newfile->size && orig->uncompressed && !memcmp(orig->uncompressed,newfile->uncompressed,orig->size)) {
                newfile->same=orig;
                return 1;
        }
        return find_identical_file(orig->child,newfile) ||
                   find_identical_file(orig->next,newfile);
}

static void eliminate_doubles(struct entry *root,struct entry *orig) {
        if(orig) {
                if(orig->size && orig->uncompressed)
			find_identical_file(root,orig);
                eliminate_doubles(root,orig->child);
                eliminate_doubles(root,orig->next);
        }
}

/*
 * We define our own sorting function instead of using alphasort which
 * uses strcoll and changes ordering based on locale information.
 */
static int cramsort (const void *a, const void *b)
{
	return strcmp ((*(const struct dirent **) a)->d_name,
		       (*(const struct dirent **) b)->d_name);
}

static unsigned int parse_directory(struct entry *root_entry, const char *name, struct entry **prev, loff_t *fslen_ub)
{
	struct dirent **dirlist;
	int totalsize = 0, dircount, dirindex;
	char *path, *endpath;
	size_t len = strlen(name);

	/* Set up the path. */
	/* TODO: Reuse the parent's buffer to save memcpy'ing and duplication. */
	path = malloc(len + 1 + MAX_INPUT_NAMELEN + 1);
	if (!path) {
		perror(NULL);
		exit(8);
	}
	memcpy(path, name, len);
	endpath = path + len;
	*endpath = '/';
	endpath++;

        /* read in the directory and sort */
        dircount = scandir(name, &dirlist, 0, cramsort);

	if (dircount < 0) {
		perror(name);
		exit(8);
	}

	/* process directory */
	for (dirindex = 0; dirindex < dircount; dirindex++) {
		struct dirent *dirent;
		struct entry *entry;
		struct stat st;
		int size;
		size_t namelen;

		dirent = dirlist[dirindex];

		/* Ignore "." and ".." - we won't be adding them to the archive */
		if (dirent->d_name[0] == '.') {
			if (dirent->d_name[1] == '\0')
				continue;
			if (dirent->d_name[1] == '.') {
				if (dirent->d_name[2] == '\0')
					continue;
			}
		}
		namelen = strlen(dirent->d_name);
		if (namelen > MAX_INPUT_NAMELEN) {
			fprintf(stderr,
				"Very long (%u bytes) filename `%s' found.\n"
				" Please increase MAX_INPUT_NAMELEN in mkcramfs.c and recompile.  Exiting.\n",
				namelen, dirent->d_name);
			exit(8);
		}
		memcpy(endpath, dirent->d_name, namelen + 1);

		if (lstat(path, &st) < 0) {
			perror(endpath);
			warn_skip = 1;
			continue;
		}
		entry = calloc(1, sizeof(struct entry));
		if (!entry) {
			perror(NULL);
			exit(8);
		}
		entry->name = strdup(dirent->d_name);
		if (!entry->name) {
			perror(NULL);
			exit(8);
		}
		if (namelen > 255) {
			/* Can't happen when reading from ext2fs. */

			/* TODO: we ought to avoid chopping in half
			   multi-byte UTF8 characters. */
			entry->name[namelen = 255] = '\0';
			warn_namelen = 1;
		}
		entry->mode = st.st_mode;
		entry->size = st.st_size;
//		entry->uid = st.st_uid;
		entry->uid = 0;
		if (entry->uid >= 1 << CRAMFS_UID_WIDTH)
			warn_uid = 1;
//		entry->gid = st.st_gid;
		entry->gid = 0;
		if (entry->gid >= 1 << CRAMFS_GID_WIDTH)
			/* TODO: We ought to replace with a default
                           gid instead of truncating; otherwise there
                           are security problems.  Maybe mode should
                           be &= ~070.  Same goes for uid once Linux
                           supports >16-bit uids. */
			warn_gid = 1;
		size = sizeof(struct cramfs_inode) + ((namelen + 3) & ~3);
		*fslen_ub += size;
		if (S_ISDIR(st.st_mode)) {
			entry->size = parse_directory(root_entry, path, &entry->child, fslen_ub);
		} else if (S_ISREG(st.st_mode)) {
			/* TODO: We ought to open files in do_compress, one
			   at a time, instead of amassing all these memory
			   maps during parse_directory (which don't get used
			   until do_compress anyway).  As it is, we tend to
			   get EMFILE errors (especially if mkcramfs is run
			   by non-root).

			   While we're at it, do analagously for symlinks
			   (which would just save a little memory). */
			int fd = open(path, O_RDONLY);
			if (fd < 0) {
				perror(path);
				warn_skip = 1;
				continue;
			}
			if (entry->size) {
				if ((entry->size >= 1 << CRAMFS_SIZE_WIDTH)) {
					warn_size = 1;
					entry->size = (1 << CRAMFS_SIZE_WIDTH) - 1;
				}

				entry->uncompressed = mmap(NULL, entry->size, PROT_READ, MAP_PRIVATE, fd, 0);
				if (-1 == (int) (long) entry->uncompressed) {
					perror("mmap");
					exit(8);
				}
			}
			close(fd);
		} else if (S_ISLNK(st.st_mode)) {
			entry->uncompressed = malloc(entry->size);
			if (!entry->uncompressed) {
				perror(NULL);
				exit(8);
			}
			if (readlink(path, entry->uncompressed, entry->size) < 0) {
				perror(path);
				warn_skip = 1;
				continue;
			}
		} else if (S_ISFIFO(st.st_mode) || S_ISSOCK(st.st_mode)) {
			/* maybe we should skip sockets */
			entry->size = 0;
		} else {
			entry->size = st.st_rdev;
			if (entry->size & -(1<<CRAMFS_SIZE_WIDTH))
				warn_dev = 1;
		}

		if (S_ISREG(st.st_mode) || S_ISLNK(st.st_mode)) {
			int blocks = ((entry->size - 1) / blksize + 1);

			/* block pointers & data expansion allowance + data */
			if(entry->size)
				*fslen_ub += (4+26)*blocks + entry->size + 3;
                }

		/* Link it into the list */
		*prev = entry;
		prev = &entry->next;
		totalsize += size;
	}
	free(path);
	free(dirlist);		/* allocated by scandir() with malloc() */
	return totalsize;
}

/* Returns sizeof(struct cramfs_super), which includes the root inode. */
static unsigned int write_superblock(struct entry *root, char *base, int size)
{
	struct cramfs_super *super = (struct cramfs_super *) base;
	unsigned int offset = sizeof(struct cramfs_super) + image_length;

	if (opt_pad) {
		offset += opt_pad;
	}

	super->magic = CRAMFS_MAGIC;
	super->flags = CRAMFS_FLAG_FSID_VERSION_2 | CRAMFS_FLAG_SORTED_DIRS;
	if (opt_holes)
		super->flags |= CRAMFS_FLAG_HOLES;
	if (image_length > 0)
		super->flags |= CRAMFS_FLAG_SHIFTED_ROOT_OFFSET;
	super->size = size;
	memcpy(super->signature, CRAMFS_SIGNATURE, sizeof(super->signature));

	super->fsid.crc = crc32(0L, Z_NULL, 0);
	super->fsid.edition = opt_edition;
	super->fsid.blocks = total_blocks;
	super->fsid.files = total_nodes;

	memset(super->name, 0x00, sizeof(super->name));
	if (opt_name)
		strncpy(super->name, opt_name, sizeof(super->name));
	else
		strncpy(super->name, "Compressed", sizeof(super->name));

	super->root.mode = root->mode;
	super->root.uid = root->uid;
	super->root.gid = root->gid;
	super->root.size = root->size;
	super->root.offset = offset >> 2;

	return offset;
}

static void set_data_offset(struct entry *entry, char *base, unsigned long offset)
{
	struct cramfs_inode *inode = (struct cramfs_inode *) (base + entry->dir_offset);
#ifdef DEBUG
	assert ((offset & 3) == 0);
#endif /* DEBUG */
	if (offset >= (1 << (2 + CRAMFS_OFFSET_WIDTH))) {
		fprintf(stderr, "filesystem too big.  Exiting.\n");
		exit(8);
	}
	inode->offset = (offset >> 2);
}


/*
 * We do a width-first printout of the directory
 * entries, using a stack to remember the directories
 * we've seen.
 */
#define MAXENTRIES (100)
static unsigned int write_directory_structure(struct entry *entry, char *base, unsigned int offset)
{
	int stack_entries = 0;
	struct entry *entry_stack[MAXENTRIES];

	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. */