minijail0: fix multiple data options with the -k mount
The recent fix for optional fields (fea05c6dcac6b69e9cc7ba03ee9c3d074)
broke passing in multiple mount options with the -k flag. Fix it and
add a unittest to prevent regression.
Bug: None
Test: `make check` passes
Test: `./minijail0 -v -k none,/tmp,tmpfs,0xe,uid=10,mode=0755 /bin/ls -al /tmp/` works again
Change-Id: Ia9fe9dec4a16654fc9a32414586a8c39d22692eb
diff --git a/minijail0.1 b/minijail0.1
index 9c962b4..e713fed 100644
--- a/minijail0.1
+++ b/minijail0.1
@@ -65,10 +65,22 @@
Run \fIprogram\fR as init (pid 1) inside a new pid namespace (implies \fB-p\fR).
.TP
\fB-k <src>,<dest>,<type>[,<flags>[,<data>]]\fR
-Mount \fIsrc\fR, a \fItype\fR filesystem, into the chroot directory at \fIdest\fR,
-with optional \fIflags\fR and optional \fIdata\fR (see \fBmount\fR(2)).
+Mount \fIsrc\fR, a \fItype\fR filesystem, at \fIdest\fR. If a chroot or pivot
+root is active, \fIdest\fR will automatically be placed below that path.
+
+The \fIflags\fR field is optional and is a hex constant. These represent the
+\fIMS_XXX\fR settings (see \fBmount\fR(2) for details). Their values can be
+looked up in the sys/mount.h header file. \fI0xe\fR is a common value here
+(a writable mount with nodev/nosuid/noexec bits set), and it is strongly
+recommended that all mounts have these three bits set whenever possible.
+
+The \fIdata\fR field is optional and is a comma delimited string (see
+\fBmount\fR(2) for details). It is passed directly to the kernel, so all
+fields here are filesystem specific.
+
If the mount is not a pseudo filesystem (e.g. proc or sysfs), \fIsrc\fR path
must be an absolute path (e.g. \fI/dev/sda1\fR and not \fIsda1\fR).
+
If the destination does not exist, it will be created as a directory.
.TP
\fB-K\fR