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41 results

mount.c

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  • mount.c 7.45 KiB
    /*
     * mount.c, by rmk
     */
    
    #include <sys/mount.h>
    #include <sys/stat.h>
    #include <fcntl.h>
    #include <errno.h>
    #include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    #include <unistd.h>
    
    #include <linux/loop.h>
    
    #define ARRAY_SIZE(x)	(sizeof(x) / sizeof(x[0]))
    
    #define DEFAULT_LOOP_DEVICE "/dev/block/loop0"
    #define LOOPDEV_MAXLEN 64
    
    struct mount_opts {
    	const char str[16];
    	unsigned long rwmask;
    	unsigned long rwset;
    	unsigned long rwnoset;
    };
    
    struct extra_opts {
    	char *str;
    	char *end;
    	int used_size;
    	int alloc_size;
    };
    
    /*
     * These options define the function of "mount(2)".
     */
    #define MS_TYPE	(MS_REMOUNT|MS_BIND|MS_MOVE)
    
    
    static const struct mount_opts options[] = {
    	/* name		mask		set		noset		*/
    	{ "async",	MS_SYNCHRONOUS,	0,		MS_SYNCHRONOUS	},
    	{ "atime",	MS_NOATIME,	0,		MS_NOATIME	},
    	{ "bind",	MS_TYPE,	MS_BIND,	0,		},
    	{ "dev",	MS_NODEV,	0,		MS_NODEV	},
    	{ "diratime",	MS_NODIRATIME,	0,		MS_NODIRATIME	},
    	{ "dirsync",	MS_DIRSYNC,	MS_DIRSYNC,	0		},
    	{ "exec",	MS_NOEXEC,	0,		MS_NOEXEC	},
    	{ "move",	MS_TYPE,	MS_MOVE,	0		},
    	{ "recurse",	MS_REC,		MS_REC,		0		},
    	{ "rec",	MS_REC,		MS_REC,		0		},
    	{ "remount",	MS_TYPE,	MS_REMOUNT,	0		},
    	{ "ro",		MS_RDONLY,	MS_RDONLY,	0		},
    	{ "rw",		MS_RDONLY,	0,		MS_RDONLY	},
    	{ "suid",	MS_NOSUID,	0,		MS_NOSUID	},
    	{ "sync",	MS_SYNCHRONOUS,	MS_SYNCHRONOUS,	0		},
    	{ "verbose",	MS_VERBOSE,	MS_VERBOSE,	0		},
    	{ "unbindable",	MS_UNBINDABLE,	MS_UNBINDABLE,	0		},
    	{ "private",	MS_PRIVATE,	MS_PRIVATE,	0		},
    	{ "slave",	MS_SLAVE,	MS_SLAVE,	0		},
    	{ "shared",	MS_SHARED,	MS_SHARED,	0		},
    };
    
    static void add_extra_option(struct extra_opts *extra, char *s)
    {
    	int len = strlen(s);
    	int newlen;
    
    	if (extra->str)
    	       len++;			/* +1 for ',' */
    	newlen = extra->used_size + len;
    
    	if (newlen >= extra->alloc_size) {
    		char *new;
    
    		new = realloc(extra->str, newlen + 1);	/* +1 for NUL */
    		if (!new)
    			return;
    
    		extra->str = new;
    		extra->end = extra->str + extra->used_size;
    		extra->alloc_size = newlen + 1;
    	}
    
    	if (extra->used_size) {
    		*extra->end = ',';
    		extra->end++;
    	}
    	strcpy(extra->end, s);
    	extra->used_size += len;
    
    }
    
    static unsigned long
    parse_mount_options(char *arg, unsigned long rwflag, struct extra_opts *extra, int* loop, char *loopdev)
    {
    	char *s;
        
        *loop = 0;
    	while ((s = strsep(&arg, ",")) != NULL) {
    		char *opt = s;
    		unsigned int i;
    		int res, no = s[0] == 'n' && s[1] == 'o';
    
    		if (no)
    			s += 2;
    
            if (strncmp(s, "loop=", 5) == 0) {
                *loop = 1;
                strlcpy(loopdev, s + 5, LOOPDEV_MAXLEN);
                continue;
            }
    
            if (strcmp(s, "loop") == 0) {
                *loop = 1;
                strlcpy(loopdev, DEFAULT_LOOP_DEVICE, LOOPDEV_MAXLEN);
                continue;
            }
    		for (i = 0, res = 1; i < ARRAY_SIZE(options); i++) {
    			res = strcmp(s, options[i].str);
    
    			if (res == 0) {
    				rwflag &= ~options[i].rwmask;
    				if (no)
    					rwflag |= options[i].rwnoset;
    				else
    					rwflag |= options[i].rwset;
    			}
    			if (res <= 0)
    				break;
    		}
    
    		if (res != 0 && s[0])
    			add_extra_option(extra, opt);
    	}
    
    	return rwflag;
    }
    
    /*
     * Mark the given block device as read-write, using the BLKROSET ioctl.
     */
    static void fs_set_blk_rw(const char *blockdev)
    {
        int fd;
        int OFF = 0;
    
        fd = open(blockdev, O_RDONLY);
        if (fd < 0) {
            // should never happen
            return;
        }
    
        ioctl(fd, BLKROSET, &OFF);
        close(fd);
    }
    
    static char *progname;
    
    static struct extra_opts extra;
    static unsigned long rwflag;
    
    static int
    do_mount(char *dev, char *dir, char *type, unsigned long rwflag, void *data, int loop,
             char *loopdev)
    {
    	char *s;
    	int error = 0;
    
        if (loop) {
            int file_fd, device_fd;
            int flags;
    
            flags = (rwflag & MS_RDONLY) ? O_RDONLY : O_RDWR;
            
            file_fd = open(dev, flags);
            if (file_fd < 0) {
                perror("open backing file failed");
                return 1;
            }
            device_fd = open(loopdev, flags);
            if (device_fd < 0) {
                perror("open loop device failed");
                close(file_fd);
                return 1;
            }
            if (ioctl(device_fd, LOOP_SET_FD, file_fd) < 0) {
                perror("ioctl LOOP_SET_FD failed");
                close(file_fd);
                close(device_fd);
                return 1;
            }
    
            close(file_fd);
            close(device_fd);
            dev = loopdev;
        }
    
        if ((rwflag & MS_RDONLY) == 0) {
            fs_set_blk_rw(dev);
        }
    
    	while ((s = strsep(&type, ",")) != NULL) {
    retry:
    		if (mount(dev, dir, s, rwflag, data) == -1) {
    			error = errno;
    			/*
    			 * If the filesystem is not found, or the
    			 * superblock is invalid, try the next.
    			 */
    			if (error == ENODEV || error == EINVAL)
    				continue;
    
    			/*
    			 * If we get EACCESS, and we're trying to
    			 * mount readwrite and this isn't a remount,
    			 * try read only.
    			 */
    			if (error == EACCES &&
    			    (rwflag & (MS_REMOUNT|MS_RDONLY)) == 0) {
    				rwflag |= MS_RDONLY;
    				goto retry;
    			}
    			break;
    		}
    	}
    
    	if (error) {
    		errno = error;
    		perror("mount");
    		return 255;
    	}
    
    	return 0;
    }
    
    static int print_mounts()
    {
        FILE* f;
        int length;
        char buffer[100];
        
        f = fopen("/proc/mounts", "r");
        if (!f) {
            fprintf(stdout, "could not open /proc/mounts\n");
            return -1;
        }
    
        do {
            length = fread(buffer, 1, 100, f);
            if (length > 0)
                fwrite(buffer, 1, length, stdout);
        } while (length > 0);
    
        fclose(f);
        return 0;
    }
    
    static int get_mounts_dev_dir(const char *arg, char **dev, char **dir)
    {
    	FILE *f;
    	char mount_dev[256];
    	char mount_dir[256];
    	char mount_type[256];
    	char mount_opts[256];
    	int mount_freq;
    	int mount_passno;
    	int match;
    
    	f = fopen("/proc/mounts", "r");
    	if (!f) {
    		fprintf(stdout, "could not open /proc/mounts\n");
    		return -1;
    	}
    
    	do {
    		match = fscanf(f, "%255s %255s %255s %255s %d %d\n",
    					   mount_dev, mount_dir, mount_type,
    					   mount_opts, &mount_freq, &mount_passno);
    		mount_dev[255] = 0;
    		mount_dir[255] = 0;
    		mount_type[255] = 0;
    		mount_opts[255] = 0;
    		if (match == 6 &&
    			(strcmp(arg, mount_dev) == 0 ||
    			 strcmp(arg, mount_dir) == 0)) {
    			*dev = strdup(mount_dev);
    			*dir = strdup(mount_dir);
    			fclose(f);
    			return 0;
    		}
    	} while (match != EOF);
    
    	fclose(f);
    	return -1;
    }
    
    int mount_main(int argc, char *argv[])
    {
    	char *type = NULL;
    	char *dev = NULL;
    	char *dir = NULL;
    	int c;
    	int loop = 0;
    	char loopdev[LOOPDEV_MAXLEN];
    
    	progname = argv[0];
    	rwflag = MS_VERBOSE;
    	
    	// mount with no arguments is equivalent to "cat /proc/mounts"
    	if (argc == 1) return print_mounts();
    
    	do {
    		c = getopt(argc, argv, "o:rt:w");
    		if (c == EOF)
    			break;
    		switch (c) {
    		case 'o':
    			rwflag = parse_mount_options(optarg, rwflag, &extra, &loop, loopdev);
    			break;
    		case 'r':
    			rwflag |= MS_RDONLY;
    			break;
    		case 't':
    			type = optarg;
    			break;
    		case 'w':
    			rwflag &= ~MS_RDONLY;
    			break;
    		case '?':
    			fprintf(stderr, "%s: invalid option -%c\n",
    				progname, optopt);
    			exit(1);
    		}
    	} while (1);
    
    	/*
    	 * If remount, bind or move was specified, then we don't
    	 * have a "type" as such.  Use the dummy "none" type.
    	 */
    	if (rwflag & MS_TYPE)
    		type = "none";
    
    	if (optind + 2 == argc) {
    		dev = argv[optind];
    		dir = argv[optind + 1];
    	} else if (optind + 1 == argc && rwflag & MS_REMOUNT) {
    		get_mounts_dev_dir(argv[optind], &dev, &dir);
    	}
    
    	if (dev == NULL || dir == NULL || type == NULL) {
    		fprintf(stderr, "Usage: %s [-r] [-w] [-o options] [-t type] "
    			"device directory\n", progname);
    		exit(1);
    	}
    
    	return do_mount(dev, dir, type, rwflag, extra.str, loop, loopdev);
    	/* We leak dev and dir in some cases, but we're about to exit */
    }