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Source document: community/ChangeLog/V0.2.x/V0.2.0.md
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V0.2.0

Release Date: 2025-08-22

Version Positioning: 0.2.0 is a milestone version of DragonOS in the three dimensions of “usability, observability, and extensibility” — introducing support for ext4, dynamic linking, eBPF, virtualization, namespaces (initial PID/Mount/User), multi-architecture (x86_64 / RISC-V64 / LoongArch64), as well as significant restructuring of the system call subsystem and memory/file cache subsystems, laying the foundation for containerization, networking, and scheduling enhancements in subsequent 0.3.x versions.

📌 Executive Summary

Key Highlights:

File System & Storage: Added ext4; completed mount/umount2; implemented gendisk/partition scanning; /proc/mounts; systematic page cache and file mapping; experimental overlayfs support; improved FAT & VFS metadata (statx / newfstatat).
Processes & Namespaces: Introduced PID Namespace, Mount Namespace, Namespace Proxy; implemented unshare(); improved process group / Session / TTY job control; enhanced /proc process information.
Memory & Virtual Memory: mmap lazy allocation, msync, private/shared file mappings; PageCache dirty page synchronization/recycling; multiple stack usage optimizations and stack overflow fixes; improved SLAB and buddy recycling.
Observability & Extensibility: Initial eBPF support (rbpf → mainline / kprobe / tracepoint / Aya ecosystem); tracepoint framework; static keys.
Virtualization: Introduced KVM/VMX basic framework and EPT; cleaned up old KVM code; improved boot stability.
Architecture: Added LoongArch64 boot & early exception handling; RISC-V64 improvements; multi-boot protocol abstraction (Multiboot2 / HVM / Serial Console / Framebuffer).
System Calls & Kernel Structure: Unified syscall table; modular migration of numerous subsystems; ERESTARTSYS mechanism; added/completed numerous system calls (poll/epoll/select, eventfd, execveat, unshare, msync, etc.).
Security & Permissions: Cred framework (UID/GID/FSUID/permission determination); set*id / setres*; chown/chmod migration and fixes.
Devices & I/O: virtio console, virtio blk partition recognition, loopback network card, TTY + epoll, HVC, PCI configuration space access, network device sysfs registration.
Toolchain & Ecosystem: Dynamic linking (ELF interpreter); Dadk 0.2.0 accelerated builds; unified user-space program builds; experimental integration with Tokio single-threaded runtime; automated documentation translation and versioning.
Stability & Quality: Fixed numerous stack frames/deadlocks/memory overflows/races/signals/wait semantics/PageCache issues; improved backtrace/unwind; unified logging system.

⚠️ Major Changes & Potential Incompatibilities (Breaking / Important Changes)

Dadk upgraded to 0.2.0: Legacy configurations are incompatible; migration required per new documentation.
Syscall structure reorganization: Subsystems migrated to table-driven architecture; custom patches need adaptation.
Default kernel stack size increased from 16K → 32K, with Guard Pages / write protection (x86_64).
PageCache semantics upgraded: mmap + direct reads/writes now require msync; legacy behavior assumptions need adjustment.
Namespace architecture initial: Interfaces may change in the future (still experimental).
eBPF interface in early form: Maps / Helpers / type restrictions may change later.

✨ New / Enhanced Features (Features & Enhancements)

1. File Systems & VFS

ext4: Integrated based on another_ext4, mountable from block devices.
mount/umount2: Real block device mount chain + partition scanning (MBR); supports MountFlags; /proc/mounts.
overlayfs (experimental): Multiple read-only layers + top-layer write copy-up + whiteout.
gendisk abstraction; virtio disk as root filesystem; automatic block device registration in devfs.
FAT/vfat: rename/move refactored; statx creation time (btime); file mapping; page cache sync fixes.
VFS: statx/newfstatat, faccessat2, linkat/renameat2, readlinkat, etc.; split open/close/stat/ioctl; LookUpFlags; /proc extended (kthread marking / FD occupancy / exe link / run/start times / TTY info).

2. Processes / Namespaces / Sessions

PID Namespace: ID mapping and isolation; nsproxy unified mounting.
Mount Namespace: Isolated root mount tree.
unshare(): New namespace creation (currently covers PID/Mount basics).
Session / Process Group: Complete job control; TTY foreground process group signals (SIGINT, etc.); wait4 fixes.
Reboot process enhanced (magic verification / multiple cmd reservations).

3. Memory Management (MM)

mmap lazy allocation / msync / mprotect fixes / madvise / msync table integration.
PageCache: ID management, page writeback, dirty page cleaning, recycling thread, multi-mapping consistency fixes.
SLAB → buddy release path completion; stack overflow detection (clippy); large function splitting to reduce stack usage.
mincore() placeholder returns ENOSYS; truncate_inode_pages framework.

4. Observability & eBPF

bpf(): Initial Maps / kprobe / statistical examples; rbpf upgraded → mainline; Aya-compatible templates.
Tracepoint framework; static key support for hotspot condition enabling.

5. Virtualization & Platform

Initial KVM/VMX + EPT; old KVM code cleaned up.
HVM / Multiboot2 / boot command line parsing (Arg/KV/EarlyKV).
LoongArch64: Boot into kernel_main + exception handling; RISC-V64 runs Rust HelloWorld; multi-platform serial/console abstraction; Serial Console + nographic.

6. Devices & I/O

virtio console (HVC); virtio blk/net/console interrupt naming improvements; PCI configuration space access (portio).
Loopback network card; network device sysfs nodes and attributes; DHCP stability.
eventfd / epoll / poll / ppoll / select / pselect6: Consistent wait/timeout/signal handling.
TTY: Adapted to epoll; control character parsing; baud rate/termios; tab/erase fixes; SIGINT broadcasting.

7. Security & Accounts

Cred framework: UID/EUID/FSUID/GID/group lists; seteuid/setegid/setres*; chown/chmod/fchownat/lchown.
get/setgroups; umask type transformation; /proc status name refinement.

8. System Call Subsystem

Unified syscall table; ERESTARTSYS; batch migration (process/mm/vfs/ipc).
Added/completed: mount, umount2, eventfd, poll/ppoll/select/pselect6, epoll refactored, fchdir, mkdirat/mkdirat2, utimensat/utimes, newfstatat/statx, execveat, unshare, set|getgroups, msync, madvise, mremap, mprotect, brk/sbrk, reboot enhanced, rt_sigpending, mincore(ENOSYS), etc.

9. Toolchain / Build / Documentation

Dadk 0.2.0: Image lifecycle management / build acceleration / profiling.
Unified user program builds: Rust + C; example Rust applications.
Dynamic linking ELF interpreter; busybox boot mode & NovaShell/DragonReach evolution.
Automated documentation translation, multilingual, multi-version Sphinx; footer shows commit; README / Q&A / namespace docs updated.
CI: Docker build caching, branch-triggered, auto image pushing, MinIO/S3 distribution, loongarch64 QEMU builds, toolchain nightly locking, backtrace/unwind upgrades, stack overflow tests.

🚀 Performance & Resource Usage (Performance & Footprint)

Reduced multiple large stack frames: IRQ initialization split, ACPI table reading macro-ized, process create/memory pool structures rewritten (Vec replacing large arrays).
PageCache secondary mapping write panic fixes → improved mmap IO coherence; reduced copies.
SLAB free page recycling → buddy, reducing resident memory.
Early detection of illegal writes via write protection + Guard Pages.

🛠 Stability & Critical Fixes (Stability & Fixes)

Representative fixes:

Wait/process: wait/wait4 semantics, do_wait lock release, blocked child process handling.
I/O Multiplexing: epoll inode reference release, epoll timeout/wake broadcast, poll boundary/RestartBlock.
Pipes/Signals: pipe/FIFO non-blocking + signal/kill semantics; blocked pipes can be killed; named pipes POSIX behavior.
PageCache: mmap multi-instance consistency; panic on writeback of dropped address space; unlink post dirty page handling.
Futex: User-space address safety safe_read/safe_write; robust list.
Signals: Default handler restoration; SIGINT distribution; KILL pid=1 feedback; pending not masked checks; execve error propagation.
TTY: Foreground process group null error; init early character input crash; tab expansion out-of-bounds.
Timers: Insertion boundaries; sleep interrupted by signals ERESTARTSYS.
Races/Memory: slab UAF/overflows; nttyData stack overflow; buddy construction large stack frames; incorrect kernel address RIP output.
File Systems: getcwd semantics; read O_PATH validation; unlink post dirty cleanup; remount errors; mprotect vm_flags.
ELF: Interpreter path read bounds; execve failure error codes.
Multiplexing: select/pselect6 early compilation issues.
virtio/PCI: Multi-device interrupt conflicts; PCI initialization order; virtio net interrupt handling.
Networking: DHCP NIC order; loopback / poll listen states.

🧾 New System Call List (Partial)

mount, umount2, fchdir, mkdirat/mkdirat2, linkat/renameat/renameat2, newfstatat, statx, readlinkat, faccessat/faccessat2, eventfd, poll, ppoll, select, pselect6, epoll (refactored), utimensat, utimes, msync, madvise, mremap, mprotect, brk/sbrk (tabled), execveat, unshare, setgroups/getgroups, rt_sigpending, reboot (enhanced), mincore(ENOSYS) …

🧪 Development & Build Experience (Dev Experience)

Dadk 0.2.0: Unified image creation / mounting / unmounting; build acceleration; profiling.
User Programs: Unified Rust + C build pipelines; Rust examples.
Toolchain: Fixed nightly versions & upgrade scripts; multi-architecture cross-toolchain scripts.
Documentation: Automated translation & stale content cleanup; bilingual (EN/zh); FAQ / build issue guidance.

🙌 Contributors (Partial, by Commit Activity / Alphabetical)

Thanks to all contributors for their ongoing efforts in kernel subsystems, file systems, virtualization, documentation, and toolchains.

Special thanks to the following core contributors:

longjin - Project lead, numerous core feature implementations and restructurings
chenlinfeng (Godones) - eBPF, networking, file systems, etc.
sparkzky - TTY, process management, system call restructurings
MemoryShore - File systems, memory management, VFS
Samuel Dai - KVM, networking, drivers
黄铭涛 - PCI, drivers, kernel optimizations
And all other contributors!

Contributors for This Release

✅ Smoke Test Checklist

Basic Boot: x86_64 / riscv64 / loongarch64 (serial/graphical); check /proc/mounts /proc/*/status.
Dynamic Linking: Run dynamically linked busybox / Rust programs.
File Systems: Mount ext4 & vfat; create/delete/rename; mmap + direct writes + msync.
Process Control: Multiple shells / Ctrl+C / foreground/background switching.
Networking: loopback ping / DHCP initialization logs.
eBPF: Load example kprobe statistics program; read trace_pipe.
poll/epoll: Run test_poll / test_epoll.
Reboot: Execute reboot syscall (simulated).
Namespaces: Test unshare (mount isolation / PID observation).

🙏 Acknowledgements

Thanks to all developers, testers, documentation contributors, and community users for their feedback. DragonOS 0.2.0 builds upon prior versions’ experiments and accumulations, also laying structural foundations for future containerization, resource isolation, and performance optimizations. Welcome to continue participating via Issues / PRs / Discussions.

🔎 Appendix: Keyword Index (for Easy Lookup)

ext4 overlayfs PageCache mmap PID namespace mount namespace unshare syscall table eBPF kprobe tracepoint Aya KVM VMX EPT LoongArch64 RISC-V virtio console loopback eventfd poll epoll select pselect6 ppoll statx newfstatat execveat dynamic linking Dadk 0.2.0 Cred chown msync mprotect utimensat reboot slab buddy Guard Page WP Tokio groupprocess/session

– END OF DragonOS 0.2.0 Release Notes –