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WIP: Port the init binary code to Rust#670

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WIP: Port the init binary code to Rust#670
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jakecorrenti:port-init

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@jakecorrenti jakecorrenti commented May 7, 2026

This PR ports the init binary code to Rust. It acts like any of the other crates that we have within the project.

To run the examples or with Podman, you would build the project as usual: make BLK=1 NET=1 && sudo make BLK=1 NET=1 install and continue with business as usual.

Fixes: #632

@jakecorrenti jakecorrenti mentioned this pull request May 7, 2026
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@mtjhrc mtjhrc May 7, 2026

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Maybe this would also be a good opportunity to move this build.rs away from devices crate too.

Not sure what should it be called, maybe init-blob? I'm thinking it should literally be a crate that has 1 public constant (which is the init binary) and this build.rs.

For now devices crate can depend on this init-blob as usual, but I plan to change that. I may end up stacking multiple PRs on top of this which (depending on how long it will take to merge this), which need this to be a separate crate1, so it would really simplify the rebases for me.

Footnotes

  1. I want to make the VMM crate depend on this init-blob and not the fs device itself (fs device will just receive a list of virtual files in constructor) this is in preparation for the 2.0 Rust API. ↩

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Sounds like #593 ;-)

@jakecorrenti jakecorrenti force-pushed the port-init branch 11 times, most recently from ed606cf to 952316c Compare May 8, 2026 18:20
@jakecorrenti
init: scaffold Rust krun-init crate and wire into build system
6fbda32 
Replace the C-based build_default_init() in src/devices/build.rs with a
Rust crate (init/) compiled via a cargo subprocess. The new build.rs
probes whether the active rustc supports the x86_64-unknown-linux-musl
target (for a static binary) and falls back to the native target with a
user-visible warning if not.

The KRUN_INIT_BINARY_PATH override mechanism is preserved so that
out-of-tree binaries (e.g. pre-built SEV or TDX images) can still be
injected without rebuilding.

Signed-off-by: Jake Correnti <jakecorrenti+github@proton.me>
Assisted-by: Claude Code:claude-sonnet-4.6
@jakecorrenti
init: implement filesystem mounting
fa1aa3c 
Add init/src/fs.rs with:
- mount_once(): helper that treats EBUSY as success
- mount_filesystems(): mounts devtmpfs, proc, sysfs, cgroup2,
  devpts, tmpfs(/dev/shm), and creates the /dev/fd symlink
- is_mount_point(): parses /proc/mounts (avoids triggering Podman
  auto-mounts that stat() would cause)
- mount_tmpfs(): mounts a tmpfs at an arbitrary path

Implement mount_tee_block_root() function used
by both SEV and TDX features to mount /dev/vda and chroot into it.

For amd-sev this replaces the previous LUKS/KBS attestation path
entirely. The SEV and TDX boot paths are now identical at the init level.

Signed-off-by: Jake Correnti <jakecorrenti+github@proton.me>
Assisted-by: Claude Code:claude-sonnet-4.6
@jakecorrenti
init: implement KRUN_BLOCK_ROOT_DEVICE pivot and shared root mount
e339639 
Extend fs.rs with:
- try_mount(): mounts with a known fstype, or probes /proc/filesystems
  when fstype is None
- mount_block_root_device(): handles KRUN_BLOCK_ROOT_DEVICE by mounting
  the block device at /newroot, issuing KRUN_REMOVE_ROOT_DIR_IOCTL to
  drop the virtiofs temporary root, then pivoting with MS_MOVE
- mount_shared_root(): sets MS_REC|MS_SHARED propagation on /

Signed-off-by: Jake Correnti <jakecorrenti+github@proton.me>
Assisted-by: Claude Code:claude-sonnet-4.6
@jakecorrenti jakecorrenti force-pushed the port-init branch 4 times, most recently from 818dd45 to d03e8d3 Compare May 8, 2026 20:37
@jakecorrenti
init: implement DHCP client
a293f59 
Port init/dhcp.c to Rust in init/src/dhcp.rs. The public surface is a
single do_dhcp(iface) function with the same behaviour as the C version:

- Sends DHCPDISCOVER with Rapid Commit (option 80)
- On DHCPACK: applies address, route, MTU, and DNS directly
- On DHCPOFFER: completes the 4-way handshake, then applies
- On no response: returns Ok (VM may be IPv6-only)

Netlink structs not exposed by libc (ifinfomsg, ifaddrmsg, rtmsg) are
defined locally with #[repr(C)]. sockaddr_nl and sockaddr_in are
zero-initialised via mem::zeroed() to handle opaque padding fields.

Signed-off-by: Jake Correnti <jakecorrenti+github@proton.me>
Assisted-by: Claude Code:claude-sonnet-4.6
@jakecorrenti
init: implement JSON config parsing
98e11b9 
Add init/src/config.rs, replacing the hand-rolled jsmn-based parser
with serde_json. Parses /.krun_config.json (or KRUN_CONFIG env var) and
returns a Config struct with:

- argv: Entrypoint ++ (args | Cmd), or None if absent
- workdir: WorkingDir or Cwd
- tmpfs: first tmpfs mount destination not already mounted

Environment variables from the Env array are applied during parsing,
with HOME and TERM always overwritten, all others set only if unset.
A missing or unparseable config file is silently ignored.

Signed-off-by: Jake Correnti <jakecorrenti+github@proton.me>
Assisted-by: Claude Code:claude-sonnet-4.6
@jakecorrenti
init: implement network interface setup
3b02687 
Add setup_network() and setup_dhcp() to env.rs.

setup_network() brings up lo unconditionally. setup_dhcp() checks that
the interface exists before calling do_dhcp(), and logs a warning on
failure rather than aborting (DHCP failure is non-fatal — the VM may be
IPv6-only or have no network).

Signed-off-by: Jake Correnti <jakecorrenti+github@proton.me>
Assisted-by: Claude Code:claude-sonnet-4.6
@jakecorrenti
init: implement environment and resource setup
46d2b70 
Extend env.rs with:
- apply_hostname(): sets hostname from HOSTNAME env var, defaulting
  to "localhost"
- apply_env(): maps KRUN_HOME -> HOME and KRUN_TERM -> TERM
- apply_rlimits(): parses the KRUN_RLIMITS comma-separated list of
  id,cur,max triples and applies each via setrlimit(2)

Signed-off-by: Jake Correnti <jakecorrenti+github@proton.me>
Assisted-by: Claude Code:claude-sonnet-4.6
@jakecorrenti
init: implement I/O redirects and workload launch
51189e2 
Add exec.rs with:
- setup_redirects(): walks /sys/class/virtio-ports and dup2s
  krun-stdin/stdout/stderr onto the corresponding file descriptors
- set_exit_code(): reports the workload exit code to the host via
  KRUN_EXIT_CODE_IOCTL, only when the root fs is virtiofs
- run_workload(): forks so PID 1 can reap children; the child calls
  exec_workload() which sets up redirects and execvp's the argv.
  Parent waits for the child, reports exit code, syncs, and reboots.
  KRUN_INIT_PID1=1 skips the fork and exec_workload directly as PID 1.

Signed-off-by: Jake Correnti <jakecorrenti+github@proton.me>
Assisted-by: Claude Code:claude-sonnet-4.6
@jakecorrenti
init: wire main.rs with full boot sequence
8de91c5 
Connect all modules in main() in order:
  1. mount_block_root()          [amd-sev | tdx]
  2. mount_filesystems()
  3. mount_block_root_device()   [KRUN_BLOCK_ROOT_DEVICE]
  4. mount_shared_root()
  5. setsid + TIOCSCTTY
  6. setup_network()
  7. config::load()
  8. mount_tmpfs()               [config tmpfs mount]
  9. apply_env / apply_hostname / apply_rlimits
 10. chdir to workdir
 11. run_workload(argv)

Signed-off-by: Jake Correnti <jakecorrenti+github@proton.me>
Assisted-by: Claude Code:claude-sonnet-4.6
@jakecorrenti
init: add FreeBSD platform helpers
603731c 
Add init/src/freebsd.rs with:
- kenv_get(): reads a variable from the FreeBSD kernel environment via
  kenv(2), which is the source of env vars for init before the process
  environment is set up
- populate_env_from_kenv(): imports the known KRUN_* variables from
  kenv into std::env at startup so the rest of the code can use
  std::env::var uniformly on both platforms
- open_console(): replicates login_tty(3) without linking libutil —
  revokes existing opens of /dev/console, opens it, creates a new
  session via setsid(2), sets the controlling terminal via TIOCSCTTY,
  and dup2s it onto stdio; falls back to /dev/null + /init.log
- mount_config_iso() / unmount_config_iso(): mounts the KRUN_CONFIG
  ISO 9660 image at /mnt via nmount(2) so the JSON config file can be
  read, then unmounts it afterwards

Signed-off-by: Jake Correnti <jakecorrenti+github@proton.me>
Assisted-by: Claude Code:claude-sonnet-4.6
@jakecorrenti
init: wire FreeBSD platform support
18f5ca5 
Connect the FreeBSD helpers into the boot sequence:
- open_console() and populate_env_from_kenv() are called at the very
  start of main() before anything else
- setsid/TIOCSCTTY are Linux-only; open_console() handles session setup
  on FreeBSD
- setlogin("root") is called on FreeBSD after console setup
- KRUN_DHCP and DHCP setup are Linux-only
- If KRUN_CONFIG is not set, mount_config_iso() is attempted; the ISO
  is unmounted immediately after config::load() returns
- fs::* mounts and mount_shared_root are Linux-only
- exec_workload() calls open_console() on FreeBSD instead of
  setup_redirects(), giving the child process a fresh controlling
  terminal before execvp

Signed-off-by: Jake Correnti <jakecorrenti+github@proton.me>
Assisted-by: Claude Code:claude-sonnet-4.6
@jakecorrenti
ci: fix FreeBSD cross-compilation
8a13671 
Replace the C-based BSD init build rule (which referenced the now-deleted
init/init.c) with a cargo build rule targeting the correct Rust triple.

Makefile:
- Remove dead INIT_SRC = init/init.c variable.
- Derive FREEBSD_RUST_TARGET from the host ARCH with arm64→aarch64
  substitution to get the correct Rust triple.
- Set CARGO_BSD_RUSTFLAGS with the clang cross-linker flags (mirroring
  the existing CC_BSD setup) so cargo can link for FreeBSD.
- aarch64-unknown-freebsd is a Tier 3 target with no prebuilt std;
  use +nightly -Z build-std for that case.

setup-build-env:
- Add rustup target add x86_64-unknown-freebsd (Tier 2, prebuilt std).
- Install nightly toolchain + rust-src for the aarch64 FreeBSD case.

cross-compilation.yml:
- Add clang to the Linux cross-compilation dependencies so the
  FreeBSD linker flags resolve correctly on Linux runners.

Signed-off-by: Jake Correnti <jakecorrenti+github@proton.me>
Assisted-by: Claude Code:claude-sonnet-4.6
@jakecorrenti
init: port timesync clock_worker to Rust
695f59e 
Implements the timesync feature behind the `timesync` cargo feature flag.
Receives host-side nanosecond timestamps over AF_VSOCK/SOCK_DGRAM on port
123 and applies them via clock_settime when the delta exceeds 100ms.

Signed-off-by: Jake Correnti <jakecorrenti+github@proton.me>
Assisted-by: Claude Code:claude-sonnet-4.6
@jakecorrenti
init: remove C sources and tee/ attestation code
1719f2f 
Delete init/init.c, init/dhcp.c, init/dhcp.h, init/jsmn.h, and the
entire init/tee/ directory (snp_attest.c/h and the KBS client).

The amd-sev feature no longer performs LUKS unlock or KBS attestation —
it mounts /dev/vda as ext4 like the tdx path does.

Signed-off-by: Jake Correnti <jakecorrenti+github@proton.me>
Assisted-by: Claude Code:claude-sonnet-4.6
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Rewrite init in Rust

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