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Version 85 (modified by Jakub Jermář, 3 years ago) (diff)

Release Notes for HelenOS mainline

Note: This document is a draft describing a future HelenOS release and is subject to change. The software described here has not been released yet. To get these latest and greatest features now, check out our Git master. (But you will also get the latest bugs).

HelenOS version (codename) was released on date.

This document contains a summary of changes made to HelenOS since release previous release.

Special Notes for this Release

Features Introduced in This Release


  • We partially revived the Doxygen documentation and plan to further improve it.
  • Prevent endless loops when printing userspace stack traces


  • Kernel is now stored in standard ELF format
  • Ordered dictionary (odict.h) now available in kernel
    • Container based on red-black trees
    • Replaced AVL trees (storing task and thread structures)
    • Replaced some uses of B+trees
  • The kernel used to pass kernel addresses of IPC phone objects (a.k.a. phone hashes) as connection identifiers to userspace. This intentional but unfortunate information leak was replaced in this release by purely user-defined labels negotiated during IPC connection setup handshake. Each connected phone now has a user-defined label and imprints this label on each IPC call which is routed through it.
  • In 2014 HelenOS got its own implementation of RCU (Read-Copy-Update) synchronization primitive along with a CHT (Concurrent Hash Table) data type based on RCU. Although sophisticated and interesting from the technological point of view, the RCU and CHT were mostly unused and unmaintained. We therefore decided to remove these very complex features.
  • The kernel waitq synchronization primitive was made available to userpace via capabilities. Consequently the userspace implementation of futexes was rewritten to use waitq's as the underlying synchronization mechanism. The custom support for futexes was removed from the kernel. One ramification of this change is that the underlying kernel object is no longer allocated lazily. This increases startup times of components that use futexes, but provides better failure modes, and better resource management possibilities in the future.

Services and Drivers

  • Fixed support for ISA-only PCs
    • Was broken since 0.5.0/0.6.0 since DDF could not enumerate ISA-only PC
    • With custom build (ia32 + CPU=486) you can run in qemu-system-i386 -M isapc


  • Fix some display issues related to a bug in the alpha blending implementation

File Systems

  • fdisk can now configure mount point for a volume
  • We can now create Ext4 (Ext2, actually,) file systems
  • Support volume labels with Ext4
  • Ext4(2) is the default new file system type for fdisk
  • Sysinst now creates Ext4(2) to install HelenOS to
  • vol insert can be used to re-insert a previously ejected volume
  • Persistent storage / system volume
    • Sysinst will now configure a persistent /w directory
      • As a reminder, this can only be used to install on some ia32/amd64 configurations
    • Tetris will now store high-score table under /w
      • Allowing it to persist across reboots - on a system installed by sysinst



  • LaiNES, an NES emulator ported (video)
  • GZX, a ZX Spectrum emulator
    • Experimental HelenOS support in upstream since January 2018
  • tester ping_pong benchmark now computes average and standard deviation across multiple runs
  • contacts is a trivial interactive utility to demonstrate the use of SIF


  • libc
    • Clean separation of fibrils and async framework
    • The async framework defines the label stored in connected IPC phones to be the userspace address of the connection structure. Because of this, the connection lookup hash table could have been dropped entirely as each incoming call already knows the connection from the label.
    • added strtold
    • replaced <atomic.h> with standard <stdatomic.h>
    • 'x' fopen file mode modifier from C11
  • SIF an API for managing structured data


  • Eliminate use of custom linker scripts for user space code
  • Further work on reviving Doxygen Reference
  • Init data is now stored as a tar archive of gzip-compressed files
  • Server binaries under /srv are now in sub-directories
  • Init data can now be configured to be uncompressed (used by default ont GTA02 and ski) for faster boot
  • Can compile with undefined behavior sanitizer in either kernel, user space or both

Regressions in This Release

  • For the list of regressions since the previous release, see this report.
  • Notable regressions

Fixed Logged Bugs & Enhancements

  • For the list of all logged defects fixed in this release, see this report.
  • For the list of all logged enhancements integrated in this release, see this report.

Known Bugs

  • For the list of known bugs still not fixed in this release, see this report.
  • For the list of all open tickets, see this report.