NSH no long calls losetup() and loteardown() directly. Now it uses /dev/loop and performs these operations using ioctl() calls

ChangeLog.txt

@@ -1461,3 +1461,7 @@
 	  leading or trailing whitespace (2015-11-23).
 	* apps/nshlib: The mount commands now accepts mount options (currently
 	  needed only for the hostfs file system).  From Ken Petit (2015-11-25).
+	* apps/nshlib:  NSH no longer calls losetup() and loteardown directly.
+	  Now it opens /dev/loop and accomplishes these things using ioctl()
+	  calls (2015-11-25).
+

nshlib/nsh.h

@@ -594,7 +594,7 @@
  *   entries the provide the necessary interfaces.
  * - Other interfaces are more standard and for these there probably should
  *   be new system calls to support the OS interface.  Such interfaces
- *   include things like losetup, loteardown, and mkrd.
+ *   include things like ps, mkfatfs, and mkrd.
  * - Other interfaces simply need to be moved out of the OS and into the C
  *   library where they will become accessible to application code.  Such
  *   interfaces include mkfatfs.
@@ -605,8 +605,6 @@
 #  define CONFIG_NSH_DISABLE_PS 1
 #  undef CONFIG_NSH_DISABLE_DF          /* 'df' depends on foreach_mountpoint */
 #  define CONFIG_NSH_DISABLE_DF 1
-#  undef CONFIG_NSH_DISABLE_LOSETUP     /* 'losetup' depends on losetup/loteardown */
-#  define CONFIG_NSH_DISABLE_LOSETUP 1
 #  undef CONFIG_NSH_DISABLE_MKFATFS     /* 'mkfatfs' depends on mkfatfs interface */
 #  define CONFIG_NSH_DISABLE_MKFATFS 1
 #  undef CONFIG_NSH_DISABLE_MKRD        /* 'mkrd' depends on ramdisk_register */
@@ -908,7 +906,7 @@ void nsh_usbtrace(void);
 # endif /* CONFIG_NFILE_STREAMS && NSH_HAVE_DIROPTS */
 
 # ifndef CONFIG_DISABLE_MOUNTPOINT
-#   ifndef CONFIG_NSH_DISABLE_LOSETUP
+#   if defined(CONFIG_DEV_LOOP) && !defined(CONFIG_NSH_DISABLE_LOSETUP)
        int cmd_losetup(FAR struct nsh_vtbl_s *vtbl, int argc, char **argv);
 #   endif
 #   ifndef CONFIG_NSH_DISABLE_MKFIFO

nshlib/nsh_command.c

@@ -243,7 +243,7 @@ static const struct cmdmap_s g_cmdmap[] =
 #endif
 
 #if CONFIG_NFILE_DESCRIPTORS > 0 && !defined(CONFIG_DISABLE_MOUNTPOINT)
-# ifndef CONFIG_NSH_DISABLE_LOSETUP
+# if defined(CONFIG_DEV_LOOP) && !defined(CONFIG_NSH_DISABLE_LOSETUP)
   { "losetup",   cmd_losetup, 3, 6, "[-d <dev-path>] | [[-o <offset>] [-r] <dev-path> <file-path>]" },
 # endif
 #endif

nshlib/nsh_fscmds.c

@@ -51,6 +51,10 @@
 #     include <sys/mount.h>
 #     include <nuttx/fs/ramdisk.h>
 #   endif
+#   ifdef CONFIG_DEV_LOOP
+#     include <sys/ioctl.h>
+#     include <nuttx/fs/loop.h>
+#   endif
 #   ifdef CONFIG_FS_FAT
 #     include <nuttx/fs/mkfatfs.h>
 #   endif
@@ -838,17 +842,19 @@ errout:
  ****************************************************************************/
 
 #if CONFIG_NFILE_DESCRIPTORS > 0 && !defined(CONFIG_DISABLE_MOUNTPOINT)
-#ifndef CONFIG_NSH_DISABLE_LOSETUP
+#   if defined(CONFIG_DEV_LOOP) && !defined(CONFIG_NSH_DISABLE_LOSETUP)
 int cmd_losetup(FAR struct nsh_vtbl_s *vtbl, int argc, char **argv)
 {
-  char *loopdev  = NULL;
+  FAR char *loopdev = NULL;
-  char *filepath = NULL;
+  FAR char *filepath = NULL;
-  bool  teardown = false;
+  struct losetup_s setup;
-  bool  readonly = false;
+  bool teardown = false;
-  off_t offset   = 0;
+  bool readonly = false;
-  bool  badarg   = false;
+  off_t offset = 0;
-  int   ret      = ERROR;
+  bool badarg = false;
-  int   option;
+  int ret = ERROR;
+  int option;
+  int fd;
 
   /* Get the losetup options:  Two forms are supported:
    *
@@ -917,10 +923,19 @@ int cmd_losetup(FAR struct nsh_vtbl_s *vtbl, int argc, char **argv)
   /* There should be nothing else on the command line */
 
   if (optind < argc)
-   {
+    {
-     nsh_output(vtbl, g_fmttoomanyargs, argv[0]);
+      nsh_output(vtbl, g_fmttoomanyargs, argv[0]);
-     goto errout_with_paths;
+      goto errout_with_paths;
-   }
+    }
+
+  /* Open the loop device */
+
+  fd = open("/dev/loop", O_RDONLY);
+  if (fd < 0)
+    {
+      nsh_output(vtbl, g_fmtcmdfailed, argv[0], "open", NSH_ERRNO);
+      goto errout_with_paths;
+    }
 
   /* Perform the teardown operation */
 
@@ -928,26 +943,37 @@ int cmd_losetup(FAR struct nsh_vtbl_s *vtbl, int argc, char **argv)
     {
       /* Tear down the loop device. */
 
-      ret = loteardown(loopdev);
+      ret = ioctl(fd, LOOPIOC_TEARDOWN, (unsigned long)((uintptr_t)loopdev));
       if (ret < 0)
         {
-          nsh_output(vtbl, g_fmtcmdfailed, argv[0], "loteardown", NSH_ERRNO_OF(-ret));
+          nsh_output(vtbl, g_fmtcmdfailed, argv[0], "ioctl", NSH_ERRNO);
-          goto errout_with_paths;
+          goto errout_with_fd;
         }
     }
   else
     {
       /* Set up the loop device */
 
-      ret = losetup(loopdev, filepath, 512, offset, readonly);
+      setup.devname  = loopdev;   /* The loop block device to be created */
+      setup.filename = filepath;  /* The file or character device to use */
+      setup.sectsize = 512;       /* The sector size to use with the block device */
+      setup.offset   = offset;    /* An offset that may be applied to the device */
+      setup.readonly = readonly;    /* True: Read access will be supported only */
+
+      ret = ioctl(fd, LOOPIOC_SETUP, (unsigned long)((uintptr_t)&setup));
       if (ret < 0)
         {
-          nsh_output(vtbl, g_fmtcmdfailed, argv[0], "losetup", NSH_ERRNO_OF(-ret));
+          nsh_output(vtbl, g_fmtcmdfailed, argv[0], "ioctl", NSH_ERRNO);
-          goto errout_with_paths;
+          goto errout_with_fd;
         }
     }
 
-  /* Free memory */
+  ret = OK;
+
+  /* Free resources */
+
+errout_with_fd:
+  (void)close(fd);
 
 errout_with_paths:
   if (loopdev)