mountlist: remove dependency on libmount

* lib/mountlist.c (read_file_system_list): Parse /proc/self/mountinfo
directly, rather than depending on libmount, which has many
dependencies due to its dependence on libselinux, as detailed at:
http://lists.gnu.org/archive/html/bug-gnulib/2015-01/msg00063.html
Note we restrict this to __linux__ as that's probably where this
interface will remain.  If ever porting, it would be best
to first pull the makedev() wrapper from coreutils to a gnulib module.
Note also we don't add a getline dependency to the mountlist module,
as all Linux versions are sufficient.

ChangeLog

@@ -1,3 +1,16 @@
+2015-04-02  Pádraig Brady  <[email protected]>
+
+	mountlist: remove dependency on libmount
+	* lib/mountlist.c (read_file_system_list): Parse /proc/self/mountinfo
+	directly, rather than depending on libmount, which has many
+	dependencies due to its dependence on libselinux, as detailed at:
+	http://lists.gnu.org/archive/html/bug-gnulib/2015-01/msg00063.html
+	Note we restrict this to __linux__ as that's probably where this
+	interface will remain.  If ever porting, it would be best
+	to first pull the makedev() wrapper from coreutils to a gnulib module.
+	Note also we don't add a getline dependency to the mountlist module,
+	as all Linux versions are sufficient.
+
 2015-04-02  Paul Eggert  <[email protected]>
 
 	stddef: port to pre-C11 GCC on x86

DEPENDENCIES

@@ -162,10 +162,3 @@ at any time.
   + Download:
     http://ftp.gnu.org/gnu/libtool/
     ftp://ftp.gnu.org/gnu/libtool/
-
-* util-linux
-  + Optional.
-    Needed if you want to support /proc/self/mountinfo available on Linux.
-    This will give an ability to propagate device ID of a mounted file system.
-  + Download:
-    http://www.kernel.org/pub/linux/utils/util-linux/

lib/mountlist.c

@@ -58,6 +58,7 @@
 
 #ifdef MOUNTED_GETMNTENT1       /* 4.3BSD, SunOS, HP-UX, Dynix, Irix.  */
 # include <mntent.h>
+# include <sys/types.h>
 # if !defined MOUNTED
 #  if defined _PATH_MOUNTED     /* GNU libc  */
 #   define MOUNTED _PATH_MOUNTED
@@ -128,12 +129,6 @@
 # include <sys/mntent.h>
 #endif
 
-#ifdef MOUNTED_PROC_MOUNTINFO
-/* Use /proc/self/mountinfo instead of /proc/self/mounts (/etc/mtab)
- * on Linux, if available */
-# include <libmount/libmount.h>
-#endif
-
 #ifndef HAVE_HASMNTOPT
 # define hasmntopt(mnt, opt) ((char *) 0)
 #endif
@@ -392,6 +387,34 @@ dev_from_mount_options (char const *mount_options)
 
 #endif
 
+#if defined MOUNTED_GETMNTENT1 && defined __linux__
+
+/* Unescape the paths in mount tables.
+   STR is updated in place.  */
+
+static void
+unescape_tab (char *str)
+{
+  size_t i, j = 0;
+  size_t len = strlen (str) + 1;
+  for (i = 0; i < len; i++)
+    {
+      if (str[i] == '\\' && (i + 4 < len)
+          && str[i + 1] >= '0' && str[i + 1] <= '3'
+          && str[i + 2] >= '0' && str[i + 2] <= '7'
+          && str[i + 3] >= '0' && str[i + 3] <= '7')
+        {
+          str[j++] = (str[i + 1] - '0') * 64 +
+                     (str[i + 2] - '0') * 8 +
+                     (str[i + 3] - '0');
+          i += 3;
+        }
+      else
+        str[j++] = str[i];
+    }
+}
+#endif
+
 /* Return a list of the currently mounted file systems, or NULL on error.
    Add each entry to the tail of the list so that they stay in order.
    If NEED_FS_TYPE is true, ensure that the file system type fields in
@@ -438,30 +461,70 @@ read_file_system_list (bool need_fs_type)
 
 #ifdef MOUNTED_GETMNTENT1 /* GNU/Linux, 4.3BSD, SunOS, HP-UX, Dynix, Irix.  */
   {
-#ifdef MOUNTED_PROC_MOUNTINFO
-    struct libmnt_table *fstable = NULL;
-
-    fstable = mnt_new_table_from_file ("/proc/self/mountinfo");
+    FILE *fp;
 
-    if (fstable != NULL)
+#ifdef __linux__
+    /* Try parsing mountinfo first, as that make device IDs available.
+       Note we could use libmount routines to simplify this parsing a little
+       (and that code is in previous versions of this function), however
+       libmount depends on libselinux which pulls in many dependencies.  */
+    char const *mountinfo = "/proc/self/mountinfo";
+    fp = fopen (mountinfo, "r");
+    if (fp != NULL)
       {
-        struct libmnt_fs *fs;
-        struct libmnt_iter *iter;
+        char *line = NULL;
+        size_t buf_size = 0;
 
-        iter = mnt_new_iter (MNT_ITER_FORWARD);
-
-        while (iter && mnt_table_next_fs (fstable, iter, &fs) == 0)
+        while (getline (&line, &buf_size, fp) != -1)
           {
+            unsigned int devmaj, devmin;
+            int target_s, target_e, type_s, type_e, source_s, source_e;
+            char test;
+            char *dash;
+            int rc;
+
+            rc = sscanf(line, "%*u "        /* id - discarded  */
+                              "%*u "        /* parent - discarded */
+                              "%u:%u "      /* dev major:minor  */
+                              "%*s "        /* mountroot - discarded  */
+                              "%n%*s%n"     /* target, start and end  */
+                              "%c",         /* more data...  */
+                              &devmaj, &devmin,
+                              &target_s, &target_e,
+                              &test);
+            if (rc != 3 && rc != 5)  /* 5 if %n included in count.  */
+              continue;
+
+            /* skip optional fields, terminated by " - "  */
+            dash = strstr (line + target_e, " - ");
+            if (! dash)
+              continue;
+
+            rc = sscanf(dash, " - "
+                              "%n%*s%n "    /* FS type, start and end  */
+                              "%n%*s%n "    /* source, start and end  */
+                              "%c",         /* more data...  */
+                              &type_s, &type_e,
+                              &source_s, &source_e,
+                              &test);
+            if (rc != 1 && rc != 5)  /* 5 if %n included in count.  */
+              continue;
+
+            /* manipulate the sub-strings in place.  */
+            line[target_e] = '\0';
+            dash[type_e] = '\0';
+            dash[source_e] = '\0';
+            unescape_tab (dash + source_s);
+            unescape_tab (line + target_s);
+
             me = xmalloc (sizeof *me);
 
-            me->me_devname = xstrdup (mnt_fs_get_source (fs));
-            me->me_mountdir = xstrdup (mnt_fs_get_target (fs));
-            me->me_type = xstrdup (mnt_fs_get_fstype (fs));
+            me->me_devname = xstrdup (dash + source_s);
+            me->me_mountdir = xstrdup (line + target_s);
+            me->me_type = xstrdup (dash + type_s);
             me->me_type_malloced = 1;
-            me->me_dev = mnt_fs_get_devno (fs);
-            /* Note we don't use mnt_fs_is_pseudofs() or mnt_fs_is_netfs() here
-               as libmount's classification is non-compatible currently.
-               Also we pass "false" for the "Bind" option as that's only
+            me->me_dev = makedev (devmaj, devmin);
+            /* we pass "false" for the "Bind" option as that's only
                significant when the Fs_type is "none" which will not be
                the case when parsing "/proc/self/mountinfo", and only
                applies for static /etc/mtab files.  */
@@ -473,13 +536,22 @@ read_file_system_list (bool need_fs_type)
             mtail = &me->me_next;
           }
 
-        mnt_free_iter (iter);
-        mnt_free_table (fstable);
+        free (line);
+
+        if (ferror (fp))
+          {
+            int saved_errno = errno;
+            fclose (fp);
+            errno = saved_errno;
+            goto free_then_fail;
+          }
+
+        if (fclose (fp) == EOF)
+          goto free_then_fail;
       }
-    else /* fallback to /proc/self/mounts (/etc/mtab) if anything failed */
-#endif /* MOUNTED_PROC_MOUNTINFO */
+    else /* fallback to /proc/self/mounts (/etc/mtab).  */
+#endif /* __linux __ */
       {
-        FILE * fp;
         struct mntent *mnt;
         char const *table = MOUNTED;
 

m4/ls-mntd-fs.m4

@@ -1,4 +1,4 @@
-# serial 31
+# serial 32
 # How to list mounted file systems.
 
 # Copyright (C) 1998-2004, 2006, 2009-2015 Free Software Foundation, Inc.
@@ -120,7 +120,7 @@ if test $ac_cv_func_getmntent = yes; then
   # Determine whether it's the one-argument variant or the two-argument one.
 
   if test -z "$ac_list_mounted_fs"; then
-    # 4.3BSD, SunOS, HP-UX, Dynix, Irix
+    # GNU/Linux, 4.3BSD, SunOS, HP-UX, Dynix, Irix
     AC_MSG_CHECKING([for one-argument getmntent function])
     AC_CACHE_VAL([fu_cv_sys_mounted_getmntent1],
                  [AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
@@ -152,25 +152,6 @@ if test $ac_cv_func_getmntent = yes; then
          of mounted file systems, and that function takes a single argument.
          (4.3BSD, SunOS, HP-UX, Dynix, Irix)])
       AC_CHECK_FUNCS([hasmntopt])
-
-      AC_ARG_WITH([libmount],
-        [AS_HELP_STRING([--with-libmount],
-          [use libmount if available to parse the system mount list.])],
-        [],
-        dnl libmount has the advantage of propagating accurate device IDs for
-        dnl each entry, but the disadvantage of many dependent shared libs
-        dnl with associated runtime startup overhead and virt mem usage.
-        [with_libmount=no])
-
-      # Check for libmount to support /proc/self/mountinfo on Linux
-      if test "x$with_libmount" != xno; then
-        AC_CHECK_LIB([mount], [mnt_new_table_from_file],
-           [AC_DEFINE([MOUNTED_PROC_MOUNTINFO], [1],
-             [Define if want to use /proc/self/mountinfo on Linux.])
-            LIBS="-lmount $LIBS"],
-           [test -f /proc/self/mountinfo &&
-             AC_MSG_WARN([/proc/self/mountinfo present but libmount missing.])])
-      fi
     fi
   fi