From eec73b70f45e15e48be592009b12a692e4c5b4c1 Mon Sep 17 00:00:00 2001
From: Christoph Herzog <chris@theduke.at>
Date: Wed, 31 May 2023 17:29:02 +0200
Subject: [PATCH] Actually mount when mapping into /

---
 lib/virtual-fs/src/tmp_fs.rs        | 11 +++++++++++
 lib/wasi/src/runners/wasi_common.rs |  1 +
 2 files changed, 12 insertions(+)

diff --git a/lib/virtual-fs/src/tmp_fs.rs b/lib/virtual-fs/src/tmp_fs.rs
index ebad58c4b7c..e72c8d33b9d 100644
--- a/lib/virtual-fs/src/tmp_fs.rs
+++ b/lib/virtual-fs/src/tmp_fs.rs
@@ -42,6 +42,17 @@ impl TmpFileSystem {
         self.fs.union(other)
     }
 
+    /// See [`mem_fs::FileSystem::mount_directory_entries`].
+    pub fn mount_directory_entries(
+        &self,
+        target_path: &Path,
+        other: &Arc<dyn crate::FileSystem + Send + Sync>,
+        source_path: &Path,
+    ) -> Result<()> {
+        self.fs
+            .mount_directory_entries(target_path, other, source_path)
+    }
+
     pub fn mount(
         &self,
         src_path: PathBuf,
diff --git a/lib/wasi/src/runners/wasi_common.rs b/lib/wasi/src/runners/wasi_common.rs
index 6cb70499c37..257d115baaf 100644
--- a/lib/wasi/src/runners/wasi_common.rs
+++ b/lib/wasi/src/runners/wasi_common.rs
@@ -121,6 +121,7 @@ fn prepare_filesystem(
                 })?;
 
             if guest_path == Path::new("/") {
+                root_fs.mount_directory_entries(&guest_path, &host_fs, &host_path)?;
             } else {
                 if let Some(parent) = guest_path.parent() {
                     create_dir_all(&root_fs, parent).with_context(|| {