Does anyone have a debugging kernel SlackBuild? (or the experience of making one)

Lockywolf · 07-05-2020, 02:20 AM

Hello, everyone.

I seem to be needing a few features of the debugging kernel (such a KPROBES).
I have built the kernel myself and had a few successful days of work, but the kernel keeps getting updated almost daily, so just through that I'd better make a script that rebuilds everything as soon as the kernel is updated.

So in order to avoid reinventing the wheel, I'm asking if anyone has had such a thing done before and can share their scripts?

Additionally, if I end up rebuilding the kernel anyway, suggestions on a good "debugging" kernel .config are welcome.

gouttegd · 07-05-2020, 05:07 AM

Hi,

I do have such a script, pasted below.

Note that I made no particular effort to make the script “generic”, it is tailored for my needs and probably cannot (or should not) be directly re-used without some adjustments.

Note also that the script does not take care of configuring the kernel: it assumes the kernel source tree has already been configured (using make config or any similar configuration command).

Code:

#!/bin/bash

set -e

if [ ! -f Kbuild ]; then
    echo "This script should be run in a Linux source tree!"
    exit 1
fi

MACHINE=${MACHINE:-$(uname -n | cut -d. -f1)}
JOBS=${JOBS:-7}
OUT=${OUT:-/tmp}
PKG=${PKG:-$OUT/kernel}

KERNEL_RELEASE=$(make -s kernelrelease)
KERNEL_VERSION=$(make -s kernelversion)

# Extract the build number from CONFIG_LOCALVERSION
BUILD=$(echo ${KERNEL_RELEASE#*-} | tr a-z A-Z)
[ "$BUILD" != "$KERNEL_RELEASE" ] || BUILD=1GGD

# Build the kernel amd the modules
make -j $JOBS bzImage
make -j $JOBS modules

# Install modules in stage directory
make modules_install INSTALL_MOD_PATH=$PKG
rm $PKG/lib/modules/$KERNEL_RELEASE/{source,build}

# Delete module signing key
rm certs/signing_key.pem

# Install kernel and associated files in /boot
install -D -m 0644 arch/x86_64/boot/bzImage $PKG/boot/vmlinuz-$KERNEL_RELEASE
install    -m 0644 System.map               $PKG/boot/System.map-$KERNEL_RELEASE
install    -m 0644 .config                  $PKG/boot/config-$KERNEL_RELEASE

# Install the kernel in the EFI filesystem
install -D -m 0644 arch/x86_64/boot/bzImage $PKG/boot/efi/EFI/Slackware/vmlinuz-$KERNEL_RELEASE

# Post-install script:
# * Build the initrd and copy it to the EFI filesystem
# * Add an ELILO entry for the new kernel
mkdir -p $PKG/install
cat <<EOF >$PKG/install/doinst.sh
#!/bin/sh

mkinitrd -F -c -k $KERNEL_RELEASE -o boot/initrd-$KERNEL_RELEASE.gz -s tmp/initrd-$KERNEL_RELEASE-tree
rm -rf tmp/initrd-$KERNEL_RELEASE-tree
cp boot/initrd-$KERNEL_RELEASE.gz boot/efi/EFI/Slackware/initrd-$KERNEL_RELEASE.gz

cat <<EOG >> boot/efi/EFI/Slackware/elilo.conf

image=vmlinuz-$KERNEL_RELEASE
  label=linux-$MACHINE-$KERNEL_RELEASE
  initrd=initrd-$KERNEL_RELEASE.gz
  read-only
EOG

echo
echo Kernel installed. Do not forget to edit
echo /boot/efi/EFI/Slackware/elilo.conf to boot
echo on the new kernel by default.
echo

EOF
chmod 755 $PKG/install/doinst.sh

# Add package description
cat <<EOF >$PKG/install/slack-desc
kernel-$MACHINE: kernel-$MACHINE (custom-built Linux kernel)
kernel-$MACHINE: 
kernel-$MACHINE: This is a Linux kernel specifically built for $MACHINE.
kernel-$MACHINE: 
kernel-$MACHINE: 
kernel-$MACHINE: 
kernel-$MACHINE: 
kernel-$MACHINE: 
kernel-$MACHINE: 
kernel-$MACHINE: 
kernel-$MACHINE: 
EOF

# Package the whole thing
cd $PKG
mkdir -p $OUT
PACKAGING="
chown root:root . -R
/sbin/makepkg -l y -c n $OUT/kernel-$MACHINE-$KERNEL_VERSION-x86_64-$BUILD.txz
rm -rf $PKG
"
su -c "$PACKAGING"

bassmadrigal · 07-05-2020, 01:03 PM

A minor tweak you might like to prevent needing to edit your elilo.conf afterwards. Instead of using cat, use sed, which can add it to the top of the Linux stanzas rather than the bottom. This would prevent you from needing to edit the conf file after installation and the newest kernel would always be the default.

Looking at my elilo.conf, there is a # before the individual stanzas start, so if you search for that, you can add text right after it (you could also add text to search for, like "# Linux Stanzas" to prevent any issues if you add additional comments). This will redirect the output into an elilo.conf in your package, which will overwrite the one on your system when you install the package.

Code:

sed "/#/aimage=vmlinuz-$KERNEL_RELEASE\n  label=linux-$MACHINE-$KERNEL_RELEASE\n  initrd=initrd-$KERNEL_RELEASE.gz\n  read-only\n" /boot/efi/EFI/Slackware/elilo.conf > $PKG/boot/efi/EFI/Slackware/elilo.conf

gus3 · 07-05-2020, 05:23 PM

Also, the Linux kernel configuration itself includes a debugging option. It's under:

Code:

-> Kernel hacking
  -> Compile-time checks and compiler options
    -> Compile the kernel with debug info