Allow bind-mounting regular files into the chroot

mount(2) with MS_BIND allows mounting a regular file on top of a regular
file, so there's no reason to only bind directories. This allows finer
control over just which files are and aren't included in the chroot
without having to build symlink trees or the like.

Signed-off-by: Shea Levy <shea@shealevy.com>

1 files changed, 9 insertions, 1 deletions

diff --git a/src/libstore/build.cc b/src/libstore/build.cc
index f71601a77c55..30fbfb8a3a54 100644
--- a/src/libstore/build.cc
+++ b/src/libstore/build.cc
@@ -2117,11 +2117,19 @@ void DerivationGoal::initChild()
                filesystem that we want in the chroot
                environment. */
             foreach (DirsInChroot::iterator, i, dirsInChroot) {
+                struct stat st;
                 Path source = i->second;
                 Path target = chrootRootDir + i->first;
                 if (source == "/proc") continue; // backwards compatibility
                 debug(format("bind mounting `%1%' to `%2%'") % source % target);
-                createDirs(target);
+                if (stat(source.c_str(), &st) == -1)
+                    throw SysError(format("getting attributes of path `%1%'") % source);
+                if (S_ISDIR(st.st_mode))
+                    createDirs(target);
+                else {
+                    createDirs(dirOf(target));
+                    writeFile(target, "");
+                }
                 if (mount(source.c_str(), target.c_str(), "", MS_BIND, 0) == -1)
                     throw SysError(format("bind mount from `%1%' to `%2%' failed") % source % target);
             }