Port the managed agent to Rust

doc/usage.md

@@ -161,12 +161,13 @@ python3 scripts/nvx.py build-guest-binaries --output DIRECTORY
 ```
 
 The Linux-only build command checks the exact `rust-toolchain.toml` pin and
-builds the five PR 1 guest executables for `x86_64-unknown-linux-musl` with one
+builds the six Rust guest executables for `x86_64-unknown-linux-musl` with one
 `cargo build` of the `guest` profile, a fresh target directory, Cargo's locked
 mode, incremental compilation disabled, inherited Cargo profile overrides
 removed, remapped source paths, and no linker build IDs. It runs the static-ELF
 check and writes `manifest.json` with the source and executable SHA-256 digests.
-It updates the output of an earlier build in place, removing the retired
+It updates the output of an earlier build in place, adding `nvx-managed-agent`
+when that build's manifest does not record it and removing the retired
 `nvx-port-io` executable when that build's manifest records it, and refuses any
 other existing `DIRECTORY`.
 
@@ -176,7 +177,7 @@ other existing `DIRECTORY`.
 python3 scripts/nvx.py test-guest-binaries --binaries DIRECTORY
 ```
 
-The Linux-only test command validates the five binaries and build manifest,
+The Linux-only test command validates the six binaries and build manifest,
 sets `NVX_GUEST_BINARIES`, and runs the musl `guest_tools` integration test
 against that exact directory.
 

nvx-rs/Cargo.toml

@@ -20,13 +20,13 @@ name = "nvx"
 default = ["host"]
 # The host side: artifact discovery, launch, network and filesystem lowering, control sessions,
 # process and platform primitives, and the supervision of VM instances.
-host = ["serde", "dep:getrandom", "dep:serde_json", "dep:libc", "dep:windows-sys"]
+host = ["serde", "dep:getrandom", "dep:serde_json", "dep:nix", "dep:windows-sys"]
 # Stages the OpenVMM executable, guest kernel, and control initramfs at build time; see
 # `Artifacts::bundled`. The build script downloads the release pinned in `artifacts.json`, or
 # copies the release directory named by `NVX_BUNDLE_DIR`.
 bundled = ["host", "dep:sha2"]
 # Test doubles: the fake OpenVMM of `testing::fake_openvmm` and its `nvx-fake-openvmm` binary.
-testing = ["dep:getrandom", "dep:serde", "dep:serde_json", "dep:libc", "dep:windows-sys"]
+testing = ["dep:getrandom", "dep:serde", "dep:serde_json", "dep:nix", "dep:windows-sys"]
 # The serde form of `Hypervisor`. The `host` feature enables it.
 serde = ["dep:serde"]
 # The programs that run in Linux guests: the `guest` module and the `nvx-*` guest binaries. Build
@@ -38,9 +38,6 @@ getrandom = { version = "0.4", optional = true }
 serde = { version = "1.0.200", features = ["derive"], optional = true }
 serde_json = { version = "1.0.120", optional = true }
 
-[target.'cfg(unix)'.dependencies]
-libc = { version = "0.2.160", optional = true }
-
 [target.'cfg(windows)'.dependencies]
 windows-sys = { version = "0.61", optional = true, features = [
     "Win32_Foundation",
@@ -52,7 +49,8 @@ windows-sys = { version = "0.61", optional = true, features = [
     "Win32_System_Threading",
 ] }
 
-[target.'cfg(target_os = "linux")'.dependencies]
+# The host and the fake OpenVMM also build on Unix hosts other than Linux, such as macOS.
+[target.'cfg(unix)'.dependencies]
 nix = { version = "0.31.3", default-features = false, optional = true, features = [
     "fs",
     "ioctl",
@@ -121,6 +119,13 @@ required-features = ["guest"]
 doc = false
 test = false
 
+[[bin]]
+name = "nvx-managed-agent"
+path = "src/bin/nvx-managed-agent.rs"
+required-features = ["guest"]
+doc = false
+test = false
+
 # The guest binaries: small, static, and stripped.
 [profile.guest]
 inherits = "release"

nvx-rs/README.md

@@ -165,6 +165,7 @@ executables as `/sbin/nvx-*`.
 | `nvx-reseed [--generation-only] SEED_FILE [PREVIOUS]`, `nvx-reseed --sample` | Reseeds the kernel's random number generator from a seed file and checks its VM generation ID, or prints a random sample |
 | `nvx-exit [CODE]` | Stops the VM with an 8-bit exit code through OpenVMM's control port 0x604 (x86_64) |
 | `nvx-device-io file ...`, `nvx-device-io network ...` | The benchmark helper that measures file and UDP round-trip I/O and prints one JSON line (x86_64) |
+| `nvx-managed-agent CONTROL_TTY ROOTFS HOSTNAME UID GID USER HOME` | Serves the managed control session and supervises sequential workloads; `--exec-config-fd FD -- WORKLOAD ...` is its internal launch helper |
 
 Each binary's command line, exit statuses, and byte output are compatibility
 contracts; the [`nvx::guest`](src/guest/mod.rs) documentation describes each
@@ -187,8 +188,10 @@ NVX_BUNDLE=skip cargo test --all-features   # unit, golden-fixture, and fake-Ope
 The tests need no hypervisor. The fake-OpenVMM test drives `Instance` end to end
 against `nvx-fake-openvmm`, and the protocol tests compare the wire constants
 with the guest agent's source in `guest/common/nvx-managed-agent.c`. On Linux,
-`nvx.py` also lints and tests the guest binaries, and runs their integration
-tests against a build of them:
+a loopback test drives the host `ControlSession` through a broker shim into the
+real managed agent's session, dispatch, and execution engine, and `nvx.py` also
+lints and tests the guest binaries, and runs their integration tests against a
+build of them:
 
 ```bash
 python3 ../scripts/nvx.py check-guest-binaries

nvx-rs/src/bin/nvx-managed-agent.rs

@@ -0,0 +1,19 @@
+//! The managed guest agent. It serves NVX's authenticated control session on the guest's control
+//! TTY and runs one workload at a time, either as the guest's PID 1 or in a sandbox's root
+//! filesystem.
+//!
+//! `nvx-managed-agent CONTROL_TTY ROOTFS HOSTNAME UID GID USER HOME` starts the agent, and
+//! `nvx-managed-agent --exec-config-fd FD -- WORKLOAD...` is its internal execution helper. See
+//! `nvx::guest::managed_agent`.
+
+#[cfg(target_os = "linux")]
+fn main() -> std::process::ExitCode {
+    nvx::guest::managed_agent::main()
+}
+
+// The agent runs only in Linux guests. Elsewhere this stub fails, so that every target that CI
+// checks with `--all-features` still builds.
+#[cfg(not(target_os = "linux"))]
+fn main() -> std::process::ExitCode {
+    std::process::ExitCode::FAILURE
+}