From 41abb0b0be8d4c7604b132a0e9c7f2db92c12d57 Mon Sep 17 00:00:00 2001
From: Tristan Ross <tristan.ross@midstall.com>
Date: Thu, 20 Jun 2024 12:09:03 -0700
Subject: [PATCH] Passthru NixOS system & OpenGL Driver

Signed-off-by: Tristan Ross <tristan.ross@midstall.com>
---
 crates/krun-guest/src/mount.rs | 25 +++++++++++++++++++++++--
 crates/krun/src/env.rs         |  4 +++-
 2 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/crates/krun-guest/src/mount.rs b/crates/krun-guest/src/mount.rs
index 31b6566..8ec9df3 100644
--- a/crates/krun-guest/src/mount.rs
+++ b/crates/krun-guest/src/mount.rs
@@ -1,9 +1,10 @@
-use std::fs::File;
+use std::fs::{File, create_dir_all};
+use std::env::var_os;
 use std::os::fd::AsFd;
 
 use anyhow::{Context, Result};
 use rustix::fs::CWD;
-use rustix::mount::{mount2, move_mount, open_tree, MountFlags, MoveMountFlags, OpenTreeFlags};
+use rustix::mount::{mount2, move_mount, mount_recursive_bind, open_tree, MountFlags, MoveMountFlags, OpenTreeFlags};
 
 pub fn mount_filesystems() -> Result<()> {
     mount2(
@@ -40,6 +41,26 @@ pub fn mount_filesystems() -> Result<()> {
         .context("Failed to move_mount `/etc/resolv.conf`")?;
     }
 
+    let opengl_driver = var_os("OPENGL_DRIVER");
+    if let Some(dir) = opengl_driver {
+        create_dir_all("/run/opengl-driver")?;
+        mount_recursive_bind(
+            dir,
+            "/run/opengl-driver",
+        )
+        .context("Failed to mount `/run/opengl-driver`")?;
+    }
+
+    let nixos_curr_sys = var_os("NIXOS_CURRENT_SYSTEM");
+    if let Some(dir) = nixos_curr_sys {
+        create_dir_all("/run/current-system")?;
+        mount_recursive_bind(
+            dir,
+            "/run/current-system",
+        )
+        .context("Failed to mount `/run/current-system`")?;
+    }
+
     mount2(
         Some("binfmt_misc"),
         "/proc/sys/fs/binfmt_misc",
diff --git a/crates/krun/src/env.rs b/crates/krun/src/env.rs
index 7efd3f6..876cf03 100644
--- a/crates/krun/src/env.rs
+++ b/crates/krun/src/env.rs
@@ -11,12 +11,14 @@ use utils::env::find_in_path;
 
 /// Automatically pass these environment variables to the microVM, if they are
 /// set.
-const WELL_KNOWN_ENV_VARS: [&str; 5] = [
+const WELL_KNOWN_ENV_VARS: [&str; 7] = [
     "LD_LIBRARY_PATH",
     "LIBGL_DRIVERS_PATH",
     "MESA_LOADER_DRIVER_OVERRIDE", // needed for asahi
     "PATH",                        // needed by `krun-guest` program
     "RUST_LOG",
+    "OPENGL_DRIVER",               // needed for OpenGL on NixOS
+    "NIXOS_CURRENT_SYSTEM",        // needed for some paths to work on NixOS
 ];
 
 /// See https://github.com/AsahiLinux/docs/wiki/Devices