>From f0a0a129f996e63981146d819eba425f85fd1eac Mon Sep 17 00:00:00 2001
From: Sam Thursfield <sam thursfield codethink co uk>
Date: Mon, 1 Jun 2015 12:46:13 +0000
Subject: [PATCH] Add --mount-tmpfs option

Allows mounting an in-memory temporary filesystem inside the chroot.
---
 src/linux-user-chroot.c | 27 +++++++++++++++++++++++++--
 1 file changed, 25 insertions(+), 2 deletions(-)

diff --git a/src/linux-user-chroot.c b/src/linux-user-chroot.c
index 8b8700d..57089e8 100644
--- a/src/linux-user-chroot.c
+++ b/src/linux-user-chroot.c
@@ -92,7 +92,8 @@ fatal_errno (const char *message)
 typedef enum {
   MOUNT_SPEC_BIND,
   MOUNT_SPEC_READONLY,
-  MOUNT_SPEC_PROCFS
+  MOUNT_SPEC_PROCFS,
+  MOUNT_SPEC_TMPFS
 } MountSpecType;
 
 typedef struct _MountSpec MountSpec;
@@ -242,6 +243,22 @@ main (int      argc,
           bind_mounts = mount;
           after_mount_arg_index += 2;
         }
+      else if (strcmp (arg, "--mount-tmpfs") == 0)
+        {
+          MountSpec *mount;
+
+          if ((argc - after_mount_arg_index) < 2)
+            fatal ("--mount-tmpfs takes one argument");
+
+          mount = malloc (sizeof (MountSpec));
+          mount->type = MOUNT_SPEC_TMPFS;
+          mount->source = NULL;
+          mount->dest = argv[after_mount_arg_index+1];
+          mount->next = bind_mounts;
+
+          bind_mounts = mount;
+          after_mount_arg_index += 2;
+        }
       else if (strcmp (arg, "--unshare-ipc") == 0)
         {
           unshare_ipc = 1;
@@ -272,7 +289,7 @@ main (int      argc,
   bind_mounts = reverse_mount_list (bind_mounts);
 
   if ((argc - after_mount_arg_index) < 2)
-    fatal ("usage: %s [--unshare-ipc] [--unshare-pid] [--unshare-net] [--mount-proc DIR] [--mount-readonly DIR] [--mount-bind SOURCE DEST] [--chdir DIR] ROOTDIR PROGRAM ARGS...", argv0);
+    fatal ("usage: %s [--unshare-ipc] [--unshare-pid] [--unshare-net] [--mount-proc DIR] [--mount-tmpfs DIR] [--mount-readonly DIR] [--mount-bind SOURCE DEST] [--chdir DIR] ROOTDIR PROGRAM ARGS...", argv0);
   chroot_dir = argv[after_mount_arg_index];
   program = argv[after_mount_arg_index+1];
   program_argv = argv + after_mount_arg_index + 1;
@@ -375,6 +392,12 @@ main (int      argc,
                          "proc", MS_MGC_VAL | MS_PRIVATE, NULL) < 0)
                 fatal_errno ("mount (\"proc\")");
             }
+          else if (bind_mount_iter->type == MOUNT_SPEC_TMPFS)
+            {
+              if (mount ("none", dest,
+                         "tmpfs", 0, NULL) < 0)
+                fatal_errno ("mount (\"tmpfs\")");
+            }
           else
             assert (0);
           free (dest);
-- 
1.9.3