The IBM AIX® operating system historically provided both 32-bit and 64-bit kernels, requiring kernel extension developers to provide 32-bit and 64-bit kernel extensions. To help developers manage multiple kernel extensions, the AIX operating system provides the dual-mode archive method, which permits both 32-bit and 64-bit kernel extensions in the same archive file. At load time, the system loader then loads the bit-appropriate kernel extension.
Beginning with AIX Version 6, the AIX operating system simplifies its kernel environment by providing only the 64-bit kernel. AIX Version 6 maintains binary compatibility with previous AIX versions, as defined by AIX binary compatibility (see Resources).
A simplified kernel extension environment
With the removal of the 32-bit kernel from AIX Version 6, the development effort for kernel extensions is significantly reduced. Kernel extension developers will not be able to build, or even test, 32-bit kernel extensions on AIX Version 6. The reduction of kernel environments means an improved return on investment, requiring less resources to develop, build, test, package, and manage kernel extensions.
To support 64-bit kernel extensions on AIX Version 6, support for building 32-bit kernel extensions is removed from kernel libraries and kernel import files. The <sys/types.h> header file is modified so that if _KERNEL is defined but __64BIT__ is not, a compilation error ensues. With the ability to build only 64-bit kernel extensions, some kernel extension build environments might require changes to avoid build errors.
This simplified kernel environment has the following concerns:
- Applications that supply 32-bit-only kernel extensions will be affected.
- Application build environments that provide 32-bit and 64-bit kernel extensions will be affected when building their kernel extensions on AIX Version 6.
Applications requiring a 32-bit-only kernel extension, whether directly or indirectly through third-party code, will fail to load the kernel extension. Depending on the application logic, the inability to load the kernel extension might result in the application being unusable or severely hindered on AIX Version 6. This is not a breakage of the AIX binary compatibility statement, but a fact that 32-bit kernel extensions are not supported.
Applications that provide both a 32-bit and a 64-bit kernel extension require minor changes in their AIX Version 6 build environment. With the removal of the 32-bit kernel and the 32-bit kernel extension build environment in AIX Version 6, automated build environments that build both 32-bit and 64-bit kernel extensions need modifications to accommodate the single, 64-bit, kernel extension environment.
Support of dual-mode kernel extensions is not being removed from AIX Version 6, and the removal of the 32-bit kernel does not affect binary compatibility. Dual-mode kernel extensions built on AIX Version 5 continue to run on AIX Version 6, but only in 64-bit mode.
The next sections offer two solutions for making the transition to AIX Version 6.
Automated build environments that build both 32-bit and 64-bit kernel extensions must now check the operating system version prior to building a 32-bit kernel extension. A simple check is sufficient, such as:
#!/bin/ksh Version='uname –v' if [ $Version –gt "5" ] then # Build 64-bit kernel extension only else # Build both 32-bit and 64-bit kernel extensions fi |
The above logic would build both 32-bit and 64-bit kernel extensions on AIX Version 5, and build only a 64-bit kernel extension for AIX Version 6.
Makefiles that support the building of both 32- and 64-bit kernel extensions can be modified. A typical Makefile file for building a dual-mode kernel extension has lines similar to:
kext: kext32 kext64:
ar –X32_64 –crf kext kext32 kext64
kext32: …
ld –b32 –o $@ …
kext64: …
ld –b64 –o $@ …
other-makefile-lines
|
This can be converted to a Makefile file building only a 64-bit kernel extension by modifying these lines to:
kext: … ld –b64 –o $@ … other-makefile-lines |
With this solution, the name of the kernel extension is unchanged, so an existing configuration method continues to work without being modified.
Reducing the number of AIX Version 6 supported kernels reduces the development costs for IBM and kernel extension providers. The reduction in cost and improved return on investment comes from reduced resources for developing, building, testing, packaging, and maintaining multiple kernels and kernel extensions.
Learn
-
AIX binary compatibility:
Learn more about AIX binary compatibility here.
-
Popular content:
See what AIX and UNIX® content your peers find interesting.
- Check out other articles and tutorials written
by Brad Cobb:
- Check out other articles and tutorials written
by Stephen Peckham:
-
AIX and
UNIX:
The AIX and UNIX developerWorks zone provides a wealth of information relating to
all aspects of AIX systems administration and expanding your UNIX skills.
-
New to AIX and UNIX?:
Visit the "New to AIX and UNIX" page to learn more about AIX and UNIX.
-
AIX Wiki:
A collaborative environment for technical information related to AIX.
-
AIX Wiki:
Visit the AIX Wiki and consult Nigel Griffith's article.
- Search the AIX and UNIX library by topic:
- System administration
- Application development
- Performance
- Porting
- Security
- Tips
- Tools and utilities
- Java™ technology
- Linux®
- Open source
-
Safari bookstore:
Visit this e-reference library to find specific technical resources.
-
developerWorks technical events and webcasts:
Stay current with developerWorks technical events and webcasts.
-
Podcasts: Tune in and
catch up with IBM technical experts.
Get products and technologies
-
IBM trial software:
Build your next development project with software for download directly from
developerWorks.
-
Quick links
for AIX fixes:
Get your AIX updates here.
- IBM
Fix Central:
This site provides fixes and updates for your system's software, hardware, and
operating system.
Discuss
- Participate in the
developerWorks blogs
and get involved in the developerWorks community.
- Participate in the AIX and UNIX forums:
- AIX—technical forum
- AIX 6 Open Beta
- AIX for Developers Forum
- Cluster Systems Management
- IBM Support Assistant
- Performance Tools—technical
- Virtualization—technical
- More AIX and UNIX forums
Brad Cobb works in the AIX Collaboration Center, where he collaborates with independent software vendors on exploiting key AIX features available on pSeries® servers. Brad has over ten years of experience porting applications to AIX, during which he has worked with various application types. You can reach him at bcobb@us.ibm.com. Also visit the AIX Collaboration Center for more information on AIX.
Stephen Peckham, IBM Corporation, 11400 Burnet Road, Austin, TX 78758. Dr. Peckham is a senior software engineer in the IBM Server Group, where he has been a member of the AIX kernel development team for the past 10 years. He has worked on the link editor, system loader, and runtime linker in recent years, and currently is focusing on performance improvements to the AIX virtual memory system. Dr. Peckham has a Ph.D. in Computer Science from Cornell University.
Comments (Undergoing maintenance)
Table of contents
Local resources
My developerWorks community
Tags
Use the slider bar to see more or fewer tags.
Popular tags shows the top tags for this particular content zone (for example, Java technology, Linux, WebSphere).
My tags shows your tags for this particular content zone (for example, Java technology, Linux, WebSphere).
Popular article tags |
My article tagsSkip to tags list
Popular article tags |
My article tags
