Linux on the IBM ESA/390 Mainframe Architecture

Overview

If you want to hack on the i370 port anyway, follow this link for status and a quick-start guide. The biggest reason why you may want to work on the i370 port is because almost no one else is working on it, and you will have quite the run of the technology. You will learn more than hacking an existing port.

IBM Linux/390

• Linux for S/390, an IBM sponsored site at Marist College, provides precompiled kernel and disk images, installation instructions, and a QuickStart guide. A good place to got when you are ready to install.

• Once you've booted and are up & running, the Millenux Linux S/390 site hosts the Think Blue Linux distribution of nearly five hundred pre-compiled RPM's for Linux/390. This is currently the defacto Linux distribution for the S/390.

• The IBM Linux for S/390 is the original location at which IBM made its patches the the kernel and compilers available. This page is well linked to other IBM sites with background material about VM, OS/390, Linux, and the relationship between all of these.

• Adam Thornton's Linux/390 at Princeton University site hosts a miscellany of materials. This includes Neale Fergusen's Linux/390 - Notes and Observations, a technical review of the kernel internals ( mirror). Also, it provides a copy of the power-point slides for the Linux/390 presentation at Usenix in Malmo, Sweden (Feb 2000), miscellaneous patches, and instructions for setting up the Hercules S/390 emulator. See also Peter Shulte-Stracke's Vintage, a set of scripts that provide a way of running the IBM-supplied s390 kernel on older (pre-G2) machines.

• The VM/ESAŽ and Linux[tm] Resources page provides some good reasons why running Linux on VM is a very, very good idea. The VM/ESA Operating System page is the starting point for VM product info at IBM. VM implements the concept of a 'virtual machine', a very powerful and under-appreciated idea for solving some fundamental operating system design problems. A good overview of what VM is and what it does and why it does it can be found in the paper A Strategic Point Of View For VM. See also the Marist Linux on VM FAQ.

• Market data about customers and the applications they want on Linux/390 can be found at the Millenux Poll of the Week site.

• Join the mailing list: send mail to listserv@vm.marist.edu saying subscribe linux-390 Your Name to join the mailing list. Or browse the mailing list archives.

• Want to see what a Linux on a mainframe looks like? Here are some photos of one of the smaller models.

• Emulation Madness shows OS/360 MFT running on the Hercules System/370 emulator on Linux/390 running as a guest machine in VM/ESA.

Press Releases

• An Introduction to Linux is written from the perspective of an S/390 expert and will help get S/390 folks up to speed.
• Jack Woehr's article for Dr. Dobb's Journal, Linux/390 in the Spotlight at SHARE 94, not only provides coverage of some SHARE events, but records a particularly good panel session discussion among some of the leading participants. It also provides very good links to additional introductory material, answering questions such as What is S/390? and What is VM?.
• The Linux for Big Iron provides a good index for Linux/390 press releases, and in particular, for most of the IBM-authored 'official' press releases.
• Report: S/390: The Linux Dream Machine, Scott Courtney's report on installing and running Linux of the S/390.
• Press Release: IBM taps Linux for Mainframes provides some insight and coverage.
• Press Release: IBM pins hardware plans on Linux is nice because it mentions my name within paragraphs of the word 'strategy' and 'Irving Wladawsky-Berger', and I'm vain enough to enjoy this association.
• Linux on Big Iron has some nice quotes from some of the early adopters and deployers of Linux/390.
• IBM Unveils Way to Make Mainframes Act Like Hundreds of Smaller Servers is a press release that positions Linux/VM as a threat to Sun.
• ROAM, Running Linux On A Mainframe, discusses some of the marketing and positioning issues.
• The debate on Slashdot about the significance of this. See also a story on Linux Today.
• Hangover Fair

Documentation

• RDR/PUN Devices for Linux. A proposal for putting RDR/PUN (virtual punched card readers & writers) on Linux. I think its a great idea, since the other operating systems sharing the box use this, and provide a convenient way of communicating.
• ESA/390 Principles of Operation (alt location) for the machine architecture, including the full instruction set, addressing modes, interrupts, etc.
• The ESA/390 Architecture Bookshelf has the 390 hardware docs
• The ESA/390 Bookshelf points at a large set of online 390 docs.
• Version 4.1 of the ELF (SysV) ABI in (Postscript) or (Acrobat PDF).
• Melinda Varian's VM Past Present and Future
• 3990/9390 Reference defines the interfaces to the disk drives
• The IBM Journal of Research and Development Vol. 43, No. 5/6, 1999 - IBM S/390 Server G5/G6 provides a technical review of the hardware design of modern mainframe systems.
• Architecture and software support in IBM S/390 Parallel Enterprise Servers for IEEE Floating-Point arithmetic
• PRSM Planning Guide provides insight into what an LPAR is, and how to set one up.

Miscellany

• THE, a gpl'ed editor with many of the features of XEDIT and KEDIT.
• An old proposal for Linux on VM
• Another collector's item is the original Marist Linux/VM Page.

• Linux to Mainframe Interoperability Tools
  • Linux to Mainframe Interoperability Tools, Tips & Techniques.
  • The Linux SNA project attempts to develop a SNA protocol stack for Linux.

GNU and Other Tools for VM, MVS, and/or Open Edition S/390

• IBM 360 shows scanned copies of ads from 1964 for a revolutionary new idea in computing: the general-purpose computer.
• VM Open Edition Ported Packages includes a number of GNU tools, Apache, Samba, etc.
• Hercules an quasi-open-source 390 emulator that runs on a PC. (quasi-open-source, because you can get the source code, but the license is otherwise very restrictive, prohibits redistribution, making patching impossible. The problem is being worked.)
• Mortice Kern Systems

• David Pitts has been maintaining an HLASM-compatible version of gcc for the MVS/Open Edition/C Environment. Among other things, it has ASCII-EBCDIC fixes to allow it to build & run on MVS. This, as well as pre-built binaries are available at David Pitts' GCC/EGCS Compiler Page.

  Note: Most, if not all, of David's patches have now been included in either the mainstream gcc distribution, or are in the i370 patch to egcs-1.1.2. The i370 back end includes a number of bug fixes not available in earlier versions of this compiler. Its the right place to start if you want an MVS-compatible version of the gcc compiler.

  Notes:

  • There may be bugs with the 64-bit integer math and/or the produced code may be very inefficient.
  • There may be bugs with the floating-point math.

• Assemblers. There are two GNU assemblers that understand the the 360/370/390 instruction set. These are the 's390' and the 'i370' assembler front-ends in the gnu 'binutils' package. Neither are HLASM-compatible, although the i370 assembler is closer to HLASM, primarily because it supports literal pools, and uses an HLASM-like syntax for instruction operands. To get a full HLASM compatible assembler, two tasks need to be undertaken: (1) add support for more HLASM-style syntax into the front end, and (2) create an XSD/ESD object format back-end. An alternative might be to write an ELF loader for MVS or VM. The source code for the i370 assembler can be downloaded here. It is part of the standard gnu distribution.

• A number of well known & popular FSF/GNU/Open Source utilities (including Apache, Samba and Perl) for OS/390 are available from the IBM Redbook SG245944 FTP site. See also the overview and the package abstracts.

History

The s390 project was also started in 1998, but followed a very different path. It was begun as a skunk-works project at the IBM Böblingen development center. It was developed in secret for over a year, with little interaction or communication with the outside world. The reason for this secrecy is unclear, although the best explanation seems to be that the developers were unaware of the normal open-source development process. It is said that they feared (political) reprisals from other parts of IBM; since the mainframe business is a lucrative business for IBM, it is beset by turf battles, intrigue and maneuvering, and closed-door deals. This fear is not unfounded: certain individuals within IBM tried to get some of the i370 developers, ahem, fired. Others worked hard to undermine the credibility of the i370 project with carefully placed non-disclosure agreements and leaked secrets. Its not about being fair, its about making money. Whatever the case may be, the s390 team chose not to work with the i370 team, and instead developed similar but incompatible tool chain (compiler, assembler, C Library) and kernel port. This project was announced publicly, and the source code released, shortly before Christmas 1999.

Despite its unusual entrance into the public eye, it has caught the imagination of all, and is currently the focus of all development and deployment efforts. The reasons for this are obvious: Its supported by a staff of paid employees (vs. i370's unpaid volunteers), and the employees work for IBM, which is, after all, the mainframe company. They call the shots. I only regret that work couldn't have proceeded in a more cooperative and inclusive fashion.

Postscript