WIP: Port the init binary code to Rust

.github/actions/setup-build-env/action.yml

@@ -9,6 +9,9 @@ runs:
         rustup update stable
         rustup default stable
         rustup component add rustfmt clippy
+        rustup target add x86_64-unknown-freebsd
+        rustup toolchain install nightly
+        rustup component add rust-src --toolchain nightly
 
     - name: Cache Cargo dependencies
       uses: actions/cache@v4

.github/workflows/cross-compilation.yml

@@ -35,7 +35,7 @@ jobs:
       - name: Install cross-compilation dependencies
         run: |
           sudo apt-get update
-          sudo apt-get install -y --no-install-recommends lld
+          sudo apt-get install -y --no-install-recommends clang lld
 
       - name: Build FreeBSD init on Linux
         run: make BUILD_BSD_INIT=1 -- init/init-freebsd
@@ -52,7 +52,7 @@ jobs:
       - name: Install cross-compilation dependencies
         run: |
           sudo apt-get update
-          sudo apt-get install -y --no-install-recommends lld
+          sudo apt-get install -y --no-install-recommends clang lld
 
       - name: Build FreeBSD init on Linux aarch64
         run: make BUILD_BSD_INIT=1 -- init/init-freebsd

Cargo.toml

@@ -1,5 +1,6 @@
 [workspace]
 members = [
+    "init",
     "src/libkrun",
     "src/input",
     "src/display",

Makefile

@@ -20,8 +20,6 @@ AWS_NITRO_INIT_SRC = \
 
 AWS_NITRO_INIT_LD_FLAGS = -larchive -lnsm
 
-INIT_SRC = init/init.c
-
 ifeq ($(SEV),1)
     VARIANT = -sev
     FEATURE_FLAGS := --features amd-sev
@@ -130,6 +128,7 @@ else
 endif
     # Cross-compile on macOS with the LLVM linker (brew install lld)
     CC_BSD=$(CLANG) -target $(ARCH)-unknown-freebsd -fuse-ld=lld -stdlib=libc++ -Wl,-strip-debug --sysroot $(SYSROOT_BSD)
+    CARGO_BSD_RUSTFLAGS = -C linker=$(CLANG) -C link-arg=-target -C link-arg=$(ARCH)-unknown-freebsd -C link-arg=-fuse-ld=lld -C link-arg=-stdlib=libc++ -C link-arg=--sysroot=$(abspath $(SYSROOT_BSD))
 else ifeq ($(OS),Linux)
 # Linux -> FreeBSD cross-compilation
 ifeq ($(SYSROOT_BSD),)
@@ -140,16 +139,34 @@ else
 endif
     # Cross-compile on Linux with clang
     CC_BSD=$(CLANG) -target $(ARCH)-unknown-freebsd -fuse-ld=lld -Wl,-strip-debug --sysroot $(SYSROOT_BSD)
+    CARGO_BSD_RUSTFLAGS = -C linker=$(CLANG) -C link-arg=-target -C link-arg=$(ARCH)-unknown-freebsd -C link-arg=-fuse-ld=lld -C link-arg=--sysroot=$(abspath $(SYSROOT_BSD))
 else
     # Build on FreeBSD host
     CC_BSD=$(CC)
     SYSROOT_BSD_TARGET =
+    CARGO_BSD_RUSTFLAGS =
+endif
+
+FREEBSD_RUST_TARGET = $(subst arm64,aarch64,$(ARCH))-unknown-freebsd
+
+# aarch64-unknown-freebsd is Tier 3: no prebuilt std, requires nightly + build-std.
+ifeq ($(FREEBSD_RUST_TARGET),aarch64-unknown-freebsd)
+    CARGO_BSD_TOOLCHAIN = +nightly
+    CARGO_BSD_EXTRA_FLAGS = -Z build-std
+else
+    CARGO_BSD_TOOLCHAIN =
+    CARGO_BSD_EXTRA_FLAGS =
 endif
 
 ifeq ($(BUILD_BSD_INIT),1)
 INIT_BINARY_BSD = init/init-freebsd
-$(INIT_BINARY_BSD): $(INIT_SRC) $(SYSROOT_BSD_TARGET)
-	$(CC_BSD) -std=c23 -O2 -static -Wall -o $@ $(INIT_SRC) -lutil
+$(INIT_BINARY_BSD): $(shell find init/src -name '*.rs') init/Cargo.toml $(SYSROOT_BSD_TARGET)
+	RUSTFLAGS="$(CARGO_BSD_RUSTFLAGS)" \
+	cargo $(CARGO_BSD_TOOLCHAIN) build --release \
+		$(CARGO_BSD_EXTRA_FLAGS) \
+		--manifest-path init/Cargo.toml \
+		--target $(FREEBSD_RUST_TARGET)
+	cp target/$(FREEBSD_RUST_TARGET)/release/krun-init $@
 endif
 
 # Sysroot preparation rules for cross-compilation on macOS

init/Cargo.toml

@@ -0,0 +1,23 @@
+[package]
+name = "krun-init"
+version = "0.1.0-1.18.0"
+edition = "2021"
+description = "PID-1 init binary for libkrun guest VMs"
+license = "Apache-2.0"
+repository = "https://github.com/containers/libkrun"
+
+[[bin]]
+name = "krun-init"
+path = "src/main.rs"
+
+[features]
+amd-sev = []
+tdx = []
+timesync = []
+
+[dependencies]
+anyhow = "1"
+libc = "0.2"
+nix = { version = "0.30", features = ["fs", "hostname", "ioctl", "mount", "process", "reboot", "resource", "signal", "socket", "term", "uio"] }
+serde = { version = "1", features = ["derive"] }
+serde_json = "1"