#!/bin/sh

# Copyright 2018, 2020, 2024  Patrick J. Volkerding, Sebeka, Minnesota, USA
# All rights reserved.
#
# Redistribution and use of this script, with or without modification, is
# permitted provided that the following conditions are met:
#
# 1. Redistributions of this script must retain the above copyright
#    notice, this list of conditions and the following disclaimer.
#
#  THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
#  WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
#  MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO
#  EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
#  SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
#  PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
#  OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
#  WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
#  OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
#  ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

# To use this script, point it to a Linux kernel source tree and a .config
# file by setting the appropriate environment variables:
#
# KERNEL_SOURCE=/usr/src/linux KERNEL_CONFIG=./kernel-configs/config-6.9.9-generic.x64 ./kernel-generic.SlackBuild
#
# It can also build the huge (or any other) kernel:
#
# KERNEL_NAME=huge KERNEL_SOURCE=/usr/src/linux KERNEL_CONFIG=./kernel-configs/config-6.9.9.x64 ./kernel-generic.SlackBuild
#
# By default, it will call the package "kernel-generic" and use the source and
# .config already in /usr/src/linux (if possible).

cd $(dirname $0) ; CWD=$(pwd)

KERNEL_NAME=${KERNEL_NAME:-generic}
KERNEL_SOURCE=${KERNEL_SOURCE:-/usr/src/linux}
KERNEL_CONFIG=${KERNEL_CONFIG:-/usr/src/linux/.config}
CONFIG_SUFFIX=${CONFIG_SUFFIX:-}
BUILD=${BUILD:-1}

# The CONFIG_DEBUG_INFO_BTF_MODULES option adds a huge amount of debugging
# data to the modules which we don't actually need. We'll strip debugging
# information from kernel modules by default. If you are building a debug
# kernel and wish to retain this data, export the variable below set to "0".
STRIP_DEBUG=${STRIP_DEBUG:-1}

# Let's export the variable with the name needed by the kernel's Makefiles,
# just for good measure.
if [ "$STRIP_DEBUG" = "1" ]; then
  export INSTALL_MOD_STRIP=$STRIP_DEBUG
else
  unset STRIP_DEBUG
fi

# Set this to true if you'd like to write the .config back to its source
# after running "make oldconfig". This ensures that the config file is the
# exact one used to build, and is sorted properly.
REGEN_CONFIG=${REGEN_CONFIG:-false}

if [ ! -r "${KERNEL_CONFIG}" ]; then
  echo "Error: the KERNEL_CONFIG environment variable needs to be set to the"
  echo ".config file to be used to build this kernel. Example:"
  echo "KERNEL_NAME=generic KERNEL_SOURCE=/usr/src/linux KERNEL_CONFIG=./kernel-configs/config-6.9.9.x64 ./kernel-generic.SlackBuild"
  echo "Tried to look for: ${KERNEL_CONFIG}"
  exit 1
fi
if [ ! -d "${KERNEL_SOURCE}" ]; then
  echo "Error: kernel source directory ${KERNEL_SOURCE} does not exist."
  exit 1
fi
# Get the kernel version from the kernel Makefile:
VERSION=$(grep "^VERSION = " ${KERNEL_SOURCE}/Makefile | rev | cut -f 1 -d ' ' | rev).$(grep "^PATCHLEVEL = " ${KERNEL_SOURCE}/Makefile | rev | cut -f 1 -d ' ' | rev).$(grep "^SUBLEVEL = " ${KERNEL_SOURCE}/Makefile | rev | cut -f 1 -d ' ' | rev)$(grep "^EXTRAVERSION = " ${KERNEL_SOURCE}/Makefile | rev | cut -f 1 -d ' ' | rev)
# Set LOCALVERSION to the value found inside the .config:
LOCALVERSION="$(cat ${KERNEL_SOURCE}/.config 2> /dev/null | grep CONFIG_LOCALVERSION= | cut -f 2 -d = | tr -d \")"
# The default kernel arch is x86 for all 32-bit and 64-bit x86:
if [ -z "${KERNEL_ARCH}" ]; then
    case "$(uname -m)" in
    i?86) KERNEL_ARCH=x86 ;;
    x86_64) KERNEL_ARCH=x86 ;;
    # Use uname -m for all other archs:
    *) KERNEL_ARCH=$(uname -m) ;;
  esac
fi
# If this variable is set to an output directory, we will also put copies of
# System.map.gz, bzImage, and config in there:
KERNEL_OUTPUT_DIRECTORY=${KERNEL_OUTPUT_DIRECTORY:-}

# If the variable PRINT_PACKAGE_NAME is set, then this script will report what
# the name of the created package would be, and then exit. This information
# could be useful to other scripts.
if [ ! -z "${PRINT_PACKAGE_NAME}" ]; then
  # We will need to copy the config and run make olddefconfig and make
  # prepare in order to generate kernel/bounds.s, where we can find
  # the true $PACKAGE_ARCH. Use olddefconfig (not oldconfig) to prevent
  # stalling if user input would be required.
  if [ ! "${KERNEL_CONFIG}" = "${KERNEL_SOURCE}/.config" ]; then
    cp -a ${KERNEL_CONFIG} ${KERNEL_SOURCE}/.config
  fi
  cd ${KERNEL_SOURCE}
  make olddefconfig 1> /dev/null 2> /dev/null
  make prepare 1> /dev/null 2> /dev/null
  PACKAGE_ARCH=$(cat kernel/bounds.s | grep -w "\-march=.*" | tr " " "\n" | grep -w "\-march=.*" | cut -f 2 -d = | tr - _)
  # Set LOCALVERSION to the value found inside the .config:
  LOCALVERSION="$(cat .config 2> /dev/null | grep CONFIG_LOCALVERSION= | cut -f 2 -d = | tr -d \")"
  echo "kernel-${KERNEL_NAME}-$(echo ${VERSION} | tr - _)$(echo ${LOCALVERSION} | tr - _)-${PACKAGE_ARCH}-$BUILD.txz"
  exit 0
fi

NUMJOBS=${NUMJOBS:-" -j$(expr $(nproc) + 1) "}
TMP=${TMP:-/tmp}
PKG=$TMP/package-kernel-${KERNEL_NAME}

rm -rf $PKG
mkdir -p $TMP $PKG

# Set the variable $KERNEL_CLEAN to anything to run "make clean" before the
# build. Default is to start compiling in the tree as we found it.
if [ ! -z "${KERNEL_CLEAN}" ]; then
  ( cd ${KERNEL_SOURCE}
    echo "Cleaning kernel source (make clean)..."
    make clean
    # Make sure header files aren't missing...
    make prepare
    # Don't package the kernel in the sources:
    find . -name "*Image" -exec rm "{}" \+
    # No need for these:
    rm -f .config.old .version
    find . -name "*.cmd" -exec rm -f "{}" \+
    rm .*.d
  )
fi

# Copy the .config into the kernel source directory (unless it's there already)
if [ ! "${KERNEL_CONFIG}" = "${KERNEL_SOURCE}/.config" ]; then
  echo "Copying the .config file to the kernel source tree:"
  cp -a --verbose ${KERNEL_CONFIG} ${KERNEL_SOURCE}/.config
fi

( cd ${KERNEL_SOURCE}
  echo "Running make oldconfig..."
  make oldconfig || exit 1

  # Write back the .config if requested:
  if [ ! "$REGEN_CONFIG" = "false" ]; then
    echo "Rewriting .config as: $KERNEL_CONFIGDIR/config-${VERSION}${LOCALVERSION}${CONFIG_SUFFIX}"
    cp -a .config $KERNEL_CONFIGDIR/config-${VERSION}${LOCALVERSION}${CONFIG_SUFFIX}
  fi

  echo "Running a preliminary make (needed to create modules.builtin.modinfo)..."
  make $NUMJOBS || exit 1
  echo "Building kernel modules..."
  make $NUMJOBS modules || exit 1
  echo "Installing kernel modules to $PKG..."
  make INSTALL_MOD_PATH=$PKG INSTALL_MOD_STRIP=$STRIP_DEBUG modules_install || exit 1
  # Fix build and source symlinks if they are pointing into $TMP:
  ( cd $PKG/lib/modules/${VERSION}${LOCALVERSION}
    for symlink in build source ; do
      target=$(readlink $symlink)
      if echo $target | grep -q "^$TMP/package-kernel-source/" ; then
        rm -f $symlink
        ln -sf $(echo $target | sed "s|$TMP/package-kernel-source/|/|g") $symlink
      fi
    done
  )
  # Make modules.dep:
  depmod -b $PKG -a ${VERSION}${LOCALVERSION}
  echo "Building kernel..."
  make $NUMJOBS bzImage || make bzImage || exit 1
  # Output files to a directory, if requested:
  if [ ! -z "${KERNEL_OUTPUT_DIRECTORY}" ]; then
    echo "Copying files to ${KERNEL_OUTPUT_DIRECTORY}..."
    mkdir -p ${KERNEL_OUTPUT_DIRECTORY}
    rm -f ${KERNEL_OUTPUT_DIRECTORY}/*
    cp -a --verbose System.map ${KERNEL_OUTPUT_DIRECTORY}
    cp -a --verbose .config ${KERNEL_OUTPUT_DIRECTORY}/config
    cp -a --verbose arch/${KERNEL_ARCH}/boot/bzImage ${KERNEL_OUTPUT_DIRECTORY}
    gzip -9 ${KERNEL_OUTPUT_DIRECTORY}/System.map
  fi
  echo "Preparing the package in $PKG..."
  mkdir -p $PKG/boot
  cp -a --verbose System.map $PKG/boot/System.map-${VERSION}${LOCALVERSION}
  cp -a --verbose .config $PKG/boot/config-${VERSION}${LOCALVERSION}${CONFIG_SUFFIX}
  cp -a --verbose arch/${KERNEL_ARCH}/boot/bzImage $PKG/boot/vmlinuz-${VERSION}${LOCALVERSION}
  # Make symlinks:
  ln -sf System.map-${VERSION}${LOCALVERSION} $PKG/boot/System.map
  ln -sf config-${VERSION}${LOCALVERSION}${CONFIG_SUFFIX} $PKG/boot/config
  ln -sf vmlinuz-${VERSION}${LOCALVERSION} $PKG/boot/vmlinuz-${KERNEL_NAME}
  ln -sf vmlinuz-${VERSION}${LOCALVERSION} $PKG/boot/vmlinuz
) || exit 1

# Fetch the kernel architecture from the source tree:
cd ${KERNEL_SOURCE}
PACKAGE_ARCH=$(cat kernel/bounds.s | grep -w "\-march=.*" | tr " " "\n" | grep -w "\-march=.*" | cut -f 2 -d = | tr - _)

mkdir $PKG/install
if [ -r $CWD/slack-desc/slack-desc.kernel-${KERNEL_NAME} ]; then
  cat $CWD/slack-desc/slack-desc.kernel-${KERNEL_NAME} > $PKG/install/slack-desc
else
  cat $CWD/slack-desc/slack-desc.kernel-template | sed "s/%PACKAGE_NAME%/kernel-${KERNEL_NAME}/g" > $PKG/install/slack-desc
fi

# Make the package:
cd $PKG
/sbin/makepkg -l y -c n $TMP/kernel-$(echo ${KERNEL_NAME} | tr - _)-$(echo ${VERSION} | tr - _)$(echo ${LOCALVERSION} | tr - _)-${PACKAGE_ARCH}-$BUILD.txz