Linux/VM: Patching the Linux/390 2.4 Kernel

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Sunday, July 06, 2008

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Patching the Linux/390 2.4 Kernel

This information was originally posted to the Linux-390 mailing list on May 2, 2002, by Mike MacIsaac.

This was originally intended to show how to correct a problem with Samba 2.2 causing a kernel oops, but the method can easily be generalized to applying any kernel patch.

Get the patches.
- Go to http://www10.software.ibm.com/developerworks/opensource/linux390/index.shtml
- Under "Downloads for kernel 2.4" in the left frame, click on "Recommended levels (2.4.7 and 2.4.17)."
- Under "Available recommended downloads:" in the main frame, click on "linux-2.4.7" If you scroll down a little, you should see the patches from November, 2001.
- Click on linux-2.4.7-s390-3
- Click on linux-2.4.7-s390-3.tar.gz which brings up a browser panel with the GNU GPL.
- Click "Accept," and you can download the patch.
- Do the same for patch 4 (linux-2.4.7-s390-4.tar.gz), and FTP these two files to /usr/src/ on the Linux system to be patched. (You may also consider patches 5 and 6, but they are not needed for the kernel oops.)
Get the kernel source.
Those which come with the distribution are usually shipped in RPMs. If the RPM is installed, the head of the source tree is almost always in the directory /usr/src/. If you do not have the directory /usr/src/linux-2.4.7.SuSE, it can be added via YaST as follows:
- # yast
- Choose Package Management (Update, Installation, Queries)
- Choose Change or create configuration
- Choose Development (C, C++, Lisp, etc.)
- Choose kernel-source (with a space bar, then F10)
- Escape up a level
- Choose Start installation - watch for "INSTALLATION COMPLETE"
- Choose Main Menu - SuSEconfig is launched
- Choose Exit Yast
You should now have a directory /usr/src/linux-2.4.7.SuSE.
Patch the code
You should now have the patches as tar files named linux-2.4.7-s390-3.tar.gz and linux-2.4.7-s390-4.tar.gz on your Linux system. Untar them:
```
# cd /usr/src
# tar -xzf linux-2.4.7-s390-3.tar.gz
# tar -xzf linux-2.4.7-s390-4.tar.gz
```
You now have .diff files which are also called patches.
Peek into them using the head command to see the directory structure:
```
# ls *.diff
linux-2.4.7-s390-3.diff  linux-2.4.7-s390-4.diff
# head -3 *.diff
==> linux-2.4.7-s390-3.diff <==
linux-2.4.7-s390/Documentation/s390/chandev.8
--- linux-2.4.7/Documentation/s390/chandev.8    Wed Nov  7 11:43:51 2001
+++ linux-2.4.7-s390/Documentation/s390/chandev.8  Wed Oct 17 14:44:39 2001

==> linux-2.4.7-s390-4.diff <==
diff -urN linux-2.4.7/arch/s390/kernel/entry.S
linux-2.4.7-s390/arch/s390/kernel/entry.S
--- linux-2.4.7/arch/s390/kernel/entry.S        Fri Nov 23 16:30:58 2001
+++ linux-2.4.7-s390/arch/s390/kernel/entry.S   Fri Nov 23 16:32:38 2001
```
Note that the base directory is named linux-2.4.7 and the directory from which the patch was obtained is linux-2-4-7-s390. To apply a patch cleanly, the base directory must be named correctly, so create two symbolic links - one named linux-2.4.7 because that is what the patch file expects and one named linux because by convention, the directory /usr/src/linux contains the current kernel's source code (If you were to upgrade to a new kernel or IPL a different one, you should update the symbolic link /usr/src/linux). Apply patches 3 and 4:
```
# cd /usr/src
# ln -s linux-2.4.7.SuSE linux-2.4.7
# ln -s linux-2.4.7.SuSE linux
# patch -p0 < linux-2.4.7-s390-3.diff
# patch -p0 < linux-2.4.7-s390-4.diff
```
To customize the build, you use the make menuconfig command:
```
# cd /usr/src/linux
# make menuconfig
```
Just exit and save the values (unless you want to change some build configuration variables).

Now build the kernel.

# cd /usr/src/linux
# make dep
...
# make modules
...
# make modules_install
...
# make image
...

Write the new kernel to the boot DASD. Write the IPL record to cylinder 0 of the DASD that will be IPLed. Look at the [ipl] section of /etc/zipl.conf:
```
[ipl]
target=/boot/zipl
image=/boot/kernel/image
#ramdisk=/boot/initrd
parameters="dasd=0130-134 root=/dev/dasda1 noinitrd"
```

Now backup and copy the new kernel files:

# cd /boot/kernel
# mv image image.orig
# mv ipleckd.boot ipleckd.boot.orig
# mv System.map System.map.orig
# cd /usr/src/linux-2.4.7/arch/s390/boot
# cp -p image /boot/kernel/
# cp -p ipleckd.boot /boot/kernel/
# cd /usr/src/linux-2.4.7
# cp -p System.map /boot/kernel/

Now run zipl to write the boot info to DASD and reboot:

# cp -p System.map /boot/kernel/
# cd /etc
# zipl -c zipl.conf
building bootmap    : /boot/zipl/bootmap
adding Kernel Image : /boot/kernel/image located at 0x00010000
adding Parmline     : /boot/zipl/parmfile located at 0x00001000
Bootloader for ECKD type devices with z/OS compatible layout installed.
Syncing disks....
...done

Now you can IPL the new kernel:
```
# shutdown -r now
```

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