Major rewrite of mount, umount, losetup. Untangled lots of code, shrunk

things down a bit, fixed a number of funky corner cases, added support for
several new features (things like mount --move, mount --bind, lazy unounts,
automatic detection of loop mounts, and so on).  Probably broke several
other things, but it's fixable.  (Bang on it, tell me what doesn't work for
you...)

Note: you no longer need to say "-o loop".  It does that for you when
necessary.

Still need to add "user mount" support, which involves making mount suid.  Not
too hard to do under the new infrastructure, just haven't done it yet...

The previous code had the following notes, that belong in the version
control comments:

- * 3/21/1999   Charles P. Wright <cpwright@cpwright.com>
- *             searches through fstab when -a is passed
- *             will try mounting stuff with all fses when passed -t auto
- *
- * 1999-04-17  Dave Cinege...Rewrote -t auto. Fixed ro mtab.
- *
- * 1999-10-07  Erik Andersen <andersen@codepoet.org>.
- *              Rewrite of a lot of code. Removed mtab usage (I plan on
- *              putting it back as a compile-time option some time),
- *              major adjustments to option parsing, and some serious
- *              dieting all around.
- *
- * 1999-11-06  mtab support is back - andersee
- *
- * 2000-01-12   Ben Collins <bcollins@debian.org>, Borrowed utils-linux's
- *              mount to add loop support.
- *
- * 2000-04-30  Dave Cinege <dcinege@psychosis.com>
- *             Rewrote fstab while loop and lower mount section. Can now do
- *             single mounts from fstab. Can override fstab options for single
- *             mount. Common mount_one call for single mounts and 'all'. Fixed
- *             mtab updating and stale entries. Removed 'remount' default.
- *

4 files changed, 89 insertions, 191 deletions

diff --git a/libbb/find_mount_point.c b/libbb/find_mount_point.c
index 83824de..eec738a 100644
--- a/libbb/find_mount_point.c
+++ b/libbb/find_mount_point.c
@@ -48,7 +48,7 @@ extern struct mntent *find_mount_point(const char *name, const char *table)
 		mountDevice = s.st_dev;
 
 
-	if ((mountTable = setmntent(table, "r")) == 0)
+	if ((mountTable = setmntent(table ? : bb_path_mtab_file, "r")) == 0)
 		return 0;
 
 	while ((mountEntry = getmntent(mountTable)) != 0) {
diff --git a/libbb/find_root_device.c b/libbb/find_root_device.c
index 2600ce5..7ff65bb 100644
--- a/libbb/find_root_device.c
+++ b/libbb/find_root_device.c
@@ -25,65 +25,25 @@
 #include <stdlib.h>
 #include "libbb.h"
 
-
-
-extern char *find_real_root_device_name(void)
+extern char *find_block_device(char *path)
 {
 	DIR *dir;
 	struct dirent *entry;
-	struct stat statBuf, rootStat;
-	char *fileName = NULL;
+	struct stat st;
 	dev_t dev;
-
-	if (stat("/", &rootStat) != 0)
-		bb_perror_msg("could not stat '/'");
-	else {
-		/* This check is here in case they pass in /dev name */
-		if ((rootStat.st_mode & S_IFMT) == S_IFBLK)
-			dev = rootStat.st_rdev;
-		else
-			dev = rootStat.st_dev;
-
-		dir = opendir("/dev");
-		if (!dir)
-			bb_perror_msg("could not open '/dev'");
-		else {
-			while((entry = readdir(dir)) != NULL) {
-				const char *myname = entry->d_name;
-				/* Must skip ".." since that is "/", and so we
-				 * would get a false positive on ".."  */
-				if (myname[0] == '.' && myname[1] == '.' && !myname[2])
-					continue;
-#ifdef CONFIG_FEATURE_DEVFS
-				/* if there is a link named /dev/root skip that too */
-				if (strcmp(myname, "root")==0)
-					continue;
-#endif
-				fileName = concat_path_file("/dev", myname);
-
-				/* Some char devices have the same dev_t as block
-				 * devices, so make sure this is a block device */
-				if (stat(fileName, &statBuf) == 0 &&
-						S_ISBLK(statBuf.st_mode)!=0 &&
-						statBuf.st_rdev == dev)
-					break;
-				free(fileName);
-				fileName=NULL;
-			}
-			closedir(dir);
+	char *retpath=NULL;
+
+	if(stat(path, &st) || !(dir = opendir("/dev"))) return NULL;
+	dev = (st.st_mode & S_IFMT) == S_IFBLK ? st.st_rdev : st.st_dev;
+	while((entry = readdir(dir)) != NULL) {
+		char devpath[PATH_MAX];
+		sprintf(devpath,"/dev/%s", entry->d_name);
+		if(!stat(devpath, &st) && S_ISBLK(st.st_mode) && st.st_rdev == dev) {
+			retpath = bb_xstrdup(devpath);
+			break;
 		}
 	}
-	if(fileName==NULL)
-		fileName = bb_xstrdup("/dev/root");
-	return fileName;
-}
-
+	closedir(dir);
 
-/* END CODE */
-/*
-Local Variables:
-c-file-style: "linux"
-c-basic-offset: 4
-tab-width: 4
-End:
-*/
+	return retpath;
+}
diff --git a/libbb/loop.c b/libbb/loop.c
index c4c3da4..25f66fc 100644
--- a/libbb/loop.c
+++ b/libbb/loop.c
@@ -19,10 +19,8 @@
  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  */
 
+
 #include <features.h>
-#if defined (__GLIBC__) && !defined(__UCLIBC__)
-#include <linux/posix_types.h>
-#endif
 #include <stdio.h>
 #include <errno.h>
 #include <fcntl.h>
@@ -30,127 +28,108 @@
 #include <unistd.h>
 #include <sys/ioctl.h>
 #include "libbb.h"
-#ifdef CONFIG_FEATURE_MOUNT_LOOP
 
-/* Grumble...  The 2.6.x kernel breaks asm/posix_types.h
- * so we get to try and cope as best we can... */
+/* For 2.6, use the cleaned up header to get the 64 bit API. */
 #include <linux/version.h>
-
 #if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,0)
-#define __bb_kernel_dev_t   __kernel_old_dev_t
-#elif LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
-#define __bb_kernel_dev_t   __kernel_dev_t
-#else
-#define __bb_kernel_dev_t   unsigned short
-#endif
+#include <linux/loop.h>
+typedef struct loop_info64 bb_loop_info;
+#define BB_LOOP_SET_STATUS LOOP_SET_STATUS64
+#define BB_LOOP_GET_STATUS LOOP_GET_STATUS64
 
-/* Stuff stolen from linux/loop.h */
+/* For 2.4 and earlier, use the 32 bit API (and don't trust the headers) */
+#else
+/* Stuff stolen from linux/loop.h for 2.4 and earlier kernels*/
+#include <linux/posix_types.h>
 #define LO_NAME_SIZE        64
 #define LO_KEY_SIZE         32
 #define LOOP_SET_FD         0x4C00
 #define LOOP_CLR_FD         0x4C01
-#define LOOP_SET_STATUS     0x4C02
-#define LOOP_GET_STATUS     0x4C03
-struct loop_info {
+#define BB_LOOP_SET_STATUS  0x4C02
+#define BB_LOOP_GET_STATUS  0x4C03
+typedef struct {
 	int                lo_number;
-	__bb_kernel_dev_t  lo_device;
+	__kernel_dev_t     lo_device;
 	unsigned long      lo_inode;
-	__bb_kernel_dev_t  lo_rdevice;
+	__kernel_dev_t     lo_rdevice;
 	int                lo_offset;
 	int                lo_encrypt_type;
 	int                lo_encrypt_key_size;
 	int                lo_flags;
-	char               lo_name[LO_NAME_SIZE];
+	char               lo_file_name[LO_NAME_SIZE];
 	unsigned char      lo_encrypt_key[LO_KEY_SIZE];
 	unsigned long      lo_init[2];
 	char               reserved[4];
-};
+} bb_loop_info;
+#endif
 
 extern int del_loop(const char *device)
 {
-	int fd;
+	int fd,rc=0;
 
-	if ((fd = open(device, O_RDONLY)) < 0) {
-		bb_perror_msg("%s", device);
-		return (FALSE);
-	}
-	if (ioctl(fd, LOOP_CLR_FD, 0) < 0) {
+	if ((fd = open(device, O_RDONLY)) < 0) rc=1;
+	else {
+		if (ioctl(fd, LOOP_CLR_FD, 0) < 0) rc=1;
 		close(fd);
-		bb_perror_msg("ioctl: LOOP_CLR_FD");
-		return (FALSE);
 	}
-	close(fd);
-	return (TRUE);
+	return rc;
 }
 
-extern int set_loop(const char *device, const char *file, int offset,
-					int *loopro)
-{
-	struct loop_info loopinfo;
-	int fd, ffd, mode;
-
-	mode = *loopro ? O_RDONLY : O_RDWR;
-	if ((ffd = open(file, mode)) < 0 && !*loopro
-		&& (errno != EROFS || (ffd = open(file, mode = O_RDONLY)) < 0)) {
-		bb_perror_msg("%s", file);
-		return 1;
-	}
-	if ((fd = open(device, mode)) < 0) {
-		close(ffd);
-		bb_perror_msg("%s", device);
-		return 1;
-	}
-	*loopro = (mode == O_RDONLY);
-
-	memset(&loopinfo, 0, sizeof(loopinfo));
-	safe_strncpy(loopinfo.lo_name, file, LO_NAME_SIZE);
-
-	loopinfo.lo_offset = offset;
-
-	loopinfo.lo_encrypt_key_size = 0;
-	if (ioctl(fd, LOOP_SET_FD, ffd) < 0) {
-		bb_perror_msg("ioctl: LOOP_SET_FD");
-		close(fd);
-		close(ffd);
-		return 1;
-	}
-	if (ioctl(fd, LOOP_SET_STATUS, &loopinfo) < 0) {
-		(void) ioctl(fd, LOOP_CLR_FD, 0);
-		bb_perror_msg("ioctl: LOOP_SET_STATUS");
-		close(fd);
-		close(ffd);
-		return 1;
-	}
-	close(fd);
-	close(ffd);
-	return 0;
-}
-
-extern char *find_unused_loop_device(void)
+// Returns 0 if mounted RW, 1 if mounted read-only, <0 for error.
+// *device is loop device to use, or if *device==NULL finds a loop device to
+// mount it on and sets *device to a strdup of that loop device name.  This
+// search will re-use an existing loop device already bound to that
+// file/offset if it finds one.
+extern int set_loop(char **device, const char *file, int offset)
 {
 	char dev[20];
-	int i, fd;
+	bb_loop_info loopinfo;
 	struct stat statbuf;
-	struct loop_info loopinfo;
+	int i, dfd, ffd, mode, rc=1;
 
-	for (i = 0; i <= CONFIG_FEATURE_MOUNT_LOOP_MAX; i++) {
-		sprintf(dev, LOOP_FORMAT, i);
-		if (stat(dev, &statbuf) == 0 && S_ISBLK(statbuf.st_mode)) {
-			if ((fd = open(dev, O_RDONLY)) >= 0) {
-				if (ioctl(fd, LOOP_GET_STATUS, &loopinfo) != 0) {
-					if (errno == ENXIO) {	/* probably free */
-						close(fd);
-						return strdup(dev);
-					}
-				}
-				close(fd);
-			}
+	// Open the file.  Barf if this doesn't work.
+	if((ffd = open(file, mode=O_RDWR))<0)
+		if(errno!=EROFS || (ffd=open(file,mode=O_RDONLY))<0)
+			return errno;
+
+	// Find a loop device
+	for(i=0;rc;i++) {
+		sprintf(dev, LOOP_FORMAT, i++);
+		// Ran out of block devices, return failure.
+		if(stat(*device ? : dev, &statbuf) || !S_ISBLK(statbuf.st_mode)) {
+			rc=ENOENT;
+			break;
 		}
+		// Open the sucker and check its loopiness.
+		if((dfd=open(dev, mode))<0 && errno==EROFS)
+			dfd=open(dev,mode=O_RDONLY);
+		if(dfd<0) continue;
+
+		rc=ioctl(dfd, BB_LOOP_GET_STATUS, &loopinfo);
+		// If device free, claim it.
+		if(rc && errno==ENXIO) {
+			memset(&loopinfo, 0, sizeof(loopinfo));
+			safe_strncpy(loopinfo.lo_file_name, file, LO_NAME_SIZE);
+			loopinfo.lo_offset = offset;
+			// Associate free loop device with file
+			if(!ioctl(dfd, LOOP_SET_FD, ffd) &&
+			   !ioctl(dfd, BB_LOOP_SET_STATUS, &loopinfo)) rc=0;
+			else ioctl(dfd, LOOP_CLR_FD, 0);
+		// If this block device already set up right, re-use it.
+		// (Yes this is racy, but associating two loop devices with the same
+		// file isn't pretty either.  In general, mounting the same file twice
+		// without using losetup manually is problematic.)
+		} else if(strcmp(file,loopinfo.lo_file_name)
+					|| offset!=loopinfo.lo_offset) rc=1;
+		close(dfd);
+		if(*device) break;
 	}
-	return NULL;
+	close(ffd);
+	if(!rc) {
+		if(!*device) *device=strdup(dev);
+		return mode==O_RDONLY ? 1 : 0;
+	} else return rc;
 }
-#endif
-
 
 /* END CODE */
 /*
diff --git a/libbb/mtab.c b/libbb/mtab.c
index b1f74c4..fa4958c 100644
--- a/libbb/mtab.c
+++ b/libbb/mtab.c
@@ -28,8 +28,8 @@
 #include "libbb.h"
 
 #define MTAB_MAX_ENTRIES 40
-static const int MS_RDONLY = 1;	/* Mount read-only.  */
 
+#ifdef CONFIG_FEATURE_MTAB_SUPPORT
 void erase_mtab(const char *name)
 {
 	struct mntent entries[MTAB_MAX_ENTRIES];
@@ -72,45 +72,4 @@ void erase_mtab(const char *name)
 	} else if (errno != EROFS)
 		bb_perror_msg(bb_path_mtab_file);
 }
-
-void write_mtab(char *blockDevice, char *directory,
-				char *filesystemType, long flags, char *string_flags)
-{
-	FILE *mountTable = setmntent(bb_path_mtab_file, "a+");
-	struct mntent m;
-
-	if (mountTable == 0) {
-		bb_perror_msg(bb_path_mtab_file);
-		return;
-	}
-	if (mountTable) {
-		int length = strlen(directory);
-
-		if (length > 1 && directory[length - 1] == '/')
-			directory[length - 1] = '\0';
-
-		if (filesystemType == 0) {
-			struct mntent *p = find_mount_point(blockDevice, "/proc/mounts");
-
-			if (p && p->mnt_type)
-				filesystemType = p->mnt_type;
-		}
-		m.mnt_fsname = blockDevice;
-		m.mnt_dir = directory;
-		m.mnt_type = filesystemType ? filesystemType : "default";
-
-		if (*string_flags) {
-			m.mnt_opts = string_flags;
-		} else {
-			if ((flags | MS_RDONLY) == flags)
-				m.mnt_opts = "ro";
-			else
-				m.mnt_opts = "rw";
-		}
-
-		m.mnt_freq = 0;
-		m.mnt_passno = 0;
-		addmntent(mountTable, &m);
-		endmntent(mountTable);
-	}
-}
+#endif