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branch: master
April 25, 2013
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/*
* 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 */
}
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