v0.21.0 (Ijiraq)

We are proud to announce the latest version of Unikraft, v0.21.0!

This release introduces a new Platform Abstraction Layer, support for VirtioFS, an overhauled printing subsystem including a dmesg-style log buffer, an improved crash screen and crash management, the ability to reseed the CSPRNG, an implementation of brk()/sbrk() syscalls, basic netlink socket support, and native build system support for JSON Compilation Database.

[!WARNING] DEPRECATION NOTICE: The old VFS, vfscore, is now marked as deprecated and will be fully removed from the codebase in a forthcoming release. For help on transitioning, consult the migration guide or join us on Discord.

A summary of the most important changes follows.

For more info refer to the accompanying blog post.

🚀 New Features#

Platform Abstraction Layer (PAL) & Architecture Rework#

• arch: Introduce new generic arch API.
• lib/ukpal: Introduce the Platform Abstraction Layer.
• plat/native: Introduce libukplat_native.
• plat/xen: Adapt to PAL (arm64 & x86_64).

Per-CPU Variables & CPU Management#

• lib/ukpcpuvar: Introduce per-CPU variables library.
• lib/uklcpu: Introduce CPU management library.

Paging#

• lib/ukpaging: Introduce paging library.

Power Management#

• lib/ukpm: Introduce system-wide power management library.

Firmware Drivers#

• drivers/firmware/ukefi: Implement power management driver for EFI platforms.
• drivers/firmware/uksmccc: Introduce SMC Calling Convention library.
• drivers/firmware/ukpsci: Introduce PSCI library.
• drivers/firmware/ukacpi: Add MADT-based CPU idx/id map filler; migrate ACPI code from plat/ to drivers/firmware.

Filesystem & Storage#

• lib/ukfs-virtiofs: Introduce VirtioFS filesystem driver.
• drivers/virtio/fs: Add Virtio FS device driver.
• lib/ukfs: Introduce node driver template.

Printing#

• lib/ukprint: Overhaul printing subsystem with dedicated console management, optional dmesg-style kernel log buffer, raw printing facilities, and runtime console loglevel adjustment via ukstore.

System Call and Process#

• lib/posix-process: Add per-process sbrk/brk implementations.

Random Number Generation#

• lib/ukrandom: Add manual and periodic CSPRNG reseed mechanism.

Crash Handling#

• lib/ukdebug: Add crash handling facilities with crashdump support.
• arch: Add support for nested exception handling.

Time#

• lib/posix-time: Provide the times() syscall and CLOCK_THREAD_CPUTIME_ID; support clock_getres() for all clocks.

Networking#

• lib/posix-netlink: Add basic Netlink socket support (route and link discovery).

Build System#

• support/build: Add native JSON Compilation Database support for IDE and tooling integration (GCC & Clang).

🐛 Bug Fixes & Improvements#

Architecture & Platform#

• arch/x86: Handle ectx in AVX512 cases;
• plat/common/arm64: Enable FP/SIMD on secondary cores
• plat/kvm/arm: Do not check for system calls on IRQ entry
• plat/kvm/x86: Enable AVX512 if available; fix lxboot do_uk_reloc call stack alignment; do hardcoded ACPI port/value write as shutdown fallback

System Call and Process#

• lib/posix-process: Use exit_signal from clone(); raise clone event on PID1; update PID allocation policy
• lib/syscall_shim: Don't inline syscall enter/exit tab wrapper; fix strace build error

Filesystem#

• lib/posix-vfs: Fix off-by-1 in return of getcwd; fully support typed vopen
• lib/posix-fstab: Tolerate mkdir failures; correctly handle mounting initrd
• lib/ukfs: Fix handling of lookup returns, live template type assumption, pathutil assert; allow readlink operation to fail; update typed vopen API
• lib/devfs: Make device name size configurable; Expose device_destroy to other link targets
• lib/vfscore: Mark vfscore as deprecated in Kconfig

Random Number Generation#

• lib/ukrandom: Fix incorrect size parameters; decouple crypto implementation from swrandom API; improve efficiency of chacha_rand32(); add end-to-end tests

Memory Management#

• lib/ukvmem: Do not assert on uninitialized DMA VMA creation
• lib/ukfallocbuddy: Fix definition of BFA_DIRECT_MAPPED
• lib/ukallocregion: Fix variable name in allocregion_posix_memalign

Networking#

• lib/posix-socket: Don't block if MSG_DONTWAIT is set in flags

Debugging#

• lib/ukdebug: Make UK_BUG an unconditional halt; mark crash function noreturn; deprecate asmdump

Boot#

• lib/ukboot: Halt system instead of crashing on init_mainlike return

Printing#

• lib/posix-tty: Fix truncated device names; fix TTY devfs initcall priority typo