From 94da3ddd336a308cc6e1c42d7124c8f417a66597 Mon Sep 17 00:00:00 2001
From: Jonathan Klimt <jonathan.klimt@eonerc.rwth-aachen.de>
Date: Mon, 13 Oct 2025 16:35:20 +0200
Subject: [PATCH] fs: Allow multiple Uhyve mounts at arbitrary paths given by
 fdt
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Co-authored-by: Martin Kröning <martin.kroening@eonerc.rwth-aachen.de>
---
 src/fs/mod.rs   | 13 +++++++++++
 src/fs/uhyve.rs | 57 ++++++++++++++++++++++++++++++++++++++++---------
 2 files changed, 60 insertions(+), 10 deletions(-)

diff --git a/src/fs/mod.rs b/src/fs/mod.rs
index 78eb630ed4..9b7a9245d3 100644
--- a/src/fs/mod.rs
+++ b/src/fs/mod.rs
@@ -404,6 +404,19 @@ pub fn create_dir(path: &str, mode: AccessPermission) -> io::Result<()> {
 	})
 }
 
+/// Creates a directory and creates all missing parent directories as well.
+fn create_dir_recursive(path: &str, mode: AccessPermission) -> io::Result<()> {
+	trace!("create_dir_recursive: {path}");
+	create_dir(path, mode).or_else(|errno| {
+		if errno != Errno::Badf {
+			return Err(errno);
+		}
+		let (parent_path, _file_name) = path.rsplit_once('/').unwrap();
+		create_dir_recursive(parent_path, mode)?;
+		create_dir(path, mode)
+	})
+}
+
 /// Returns an vector with all the entries within a directory.
 pub fn readdir(name: &str) -> io::Result<Vec<DirectoryEntry>> {
 	debug!("Read directory {name}");
diff --git a/src/fs/uhyve.rs b/src/fs/uhyve.rs
index 58c0afe607..dce0a4fe58 100644
--- a/src/fs/uhyve.rs
+++ b/src/fs/uhyve.rs
@@ -1,3 +1,4 @@
+use alloc::borrow::ToOwned;
 use alloc::boxed::Box;
 use alloc::ffi::CString;
 use alloc::string::{String, ToString};
@@ -14,9 +15,11 @@ use uhyve_interface::parameters::{
 use uhyve_interface::{GuestPhysAddr, GuestVirtAddr, Hypercall};
 
 use crate::arch::mm::paging;
+use crate::env::fdt;
 use crate::errno::Errno;
 use crate::fs::{
 	self, AccessPermission, FileAttr, NodeKind, ObjectInterface, OpenOption, SeekWhence, VfsNode,
+	create_dir_recursive,
 };
 use crate::io;
 use crate::syscalls::interfaces::uhyve::uhyve_hypercall;
@@ -229,14 +232,48 @@ impl VfsNode for UhyveDirectory {
 
 pub(crate) fn init() {
 	info!("Try to initialize uhyve filesystem");
-	let mount_point = hermit_var_or!("UHYVE_MOUNT", "/root").to_string();
-	info!("Mounting uhyve filesystem at {mount_point}");
-	fs::FILESYSTEM
-		.get()
-		.unwrap()
-		.mount(
-			&mount_point,
-			Box::new(UhyveDirectory::new(Some(mount_point.clone()))),
-		)
-		.expect("Mount failed. Duplicate mount_point?");
+	let mount_str = fdt().and_then(|fdt| {
+		fdt.find_node("/uhyve,mounts")
+			.and_then(|node| node.property("mounts"))
+			.and_then(|property| property.as_str())
+	});
+	if let Some(mount_str) = mount_str {
+		assert_ne!(mount_str.len(), 0, "Invalid /uhyve,mounts node in FDT");
+		for mount_point in mount_str.split('\0') {
+			info!("Mounting uhyve filesystem at {mount_point}");
+
+			if let Err(errno) = fs::FILESYSTEM.get().unwrap().mount(
+				mount_point,
+				Box::new(UhyveDirectory::new(Some(mount_point.to_owned()))),
+			) {
+				assert_eq!(errno, Errno::Badf);
+				debug!(
+					"Mounting of {mount_point} failed with {errno:?}. Creating missing parent folders"
+				);
+				let (parent_path, _file_name) = mount_point.rsplit_once('/').unwrap();
+				create_dir_recursive(parent_path, AccessPermission::S_IRWXU).unwrap();
+
+				fs::FILESYSTEM
+					.get()
+					.unwrap()
+					.mount(
+						mount_point,
+						Box::new(UhyveDirectory::new(Some(mount_point.to_owned()))),
+					)
+					.unwrap();
+			}
+		}
+	} else {
+		// No FDT -> Uhyve legacy mounting (to /root)
+		let mount_point = hermit_var_or!("UHYVE_MOUNT", "/root").to_string();
+		info!("Mounting uhyve filesystem at {mount_point}");
+		fs::FILESYSTEM
+			.get()
+			.unwrap()
+			.mount(
+				&mount_point,
+				Box::new(UhyveDirectory::new(Some(mount_point.clone()))),
+			)
+			.expect("Mount failed. Duplicate mount_point?");
+	}
 }