#!/bin/bash
#
# Blueprint to build a linux kernel.
#
# The kernel is the heart of the operating system and provides access
# to system resources like CPU, memory and disks.
#
# Source is from ftp://ftp.kernel.org/pub/linux/kernel/2.6/
#
#
# This script is public domain software and may be freely copied.
#
# This script is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
#
# Define the package name, source directory, build directory and
# staging directory paths.  Prefixes to directories may be overridden
# by setting shell variables SRC, BUILD and STAGING.  For example,
# doing "export SRC=/root/foo" before calling this script will override
# the default /usr/src and set SRC_DIR to /root/foo/$PKG_NAME instead.
#
PKG_NAME=$(basename $0)
SRC_DIR=${SRC:-/usr/src}/$PKG_NAME
BUILD_DIR=${BUILD:-/var/tmp/build}/$PKG_NAME
STAGING_DIR=${STAGING:-/var/tmp/staging}/$PKG_NAME
# Change the staging directory name to include the word 'headers' since
# that is what will end up going there.  The actual kernel and modules
# are packaged separately by the Linux kernel's Makefile.
STAGING_DIR="$STAGING_DIR-headers"
#
# Check that the source directory really exits and bail out if not.
if ! [ -d $SRC_DIR ]; then
  echo "$PKG_NAME: Cannot find source code directory $SRC_DIR."
  exit 1
fi
#
# Do not overwrite existing build directory.
#if [ -d $BUILD_DIR ]; then
#  echo "$PKG_NAME: Build directory $BUILD_DIR already exists."
#  exit 2
#else
#  mkdir -p $BUILD_DIR
#fi
#
# Do not overwrite existing staging directory.
if [ -d $STAGING_DIR ]; then
  echo "$PKG_NAME: Staging directory $STAGING_DIR already exists."
  exit 4
else
  mkdir -p $STAGING_DIR
fi
#
# Configure the kernel.
cd /usr/src/linux
if [ -f /proc/config.gz ]; then
  echo "A config file for the current kernel was found (/proc/config.gz)."
  echo "Would you like to use this as a starting point for configuration [y/N]?"
  read REPLY
  if [ "$REPLY" = "Y" ] || [ "$REPLY" = "y" ]; then
    cp .config .config.old
    zcat /proc/config.gz > .config
  fi
fi

make menuconfig

# Check return status and bail out if it's non-zero.
if [ $? -gt 0 ]; then
  echo "Kernel configuration failed!"
  exit 8
fi

# Build the package.
make

# Check return code and bail if it looks bad.
if [ $? -gt 0 ]; then
  echo "Kernel build failed!"
  exit 16
fi

# Create a tar-gzip package for the kernel and modules using the make
# target 'targz-pkg'.  Also install kernel headers into the staging area.
make targz-pkg && make INSTALL_HDR_PATH=$STAGING_DIR/usr headers_install

# Check return code and bail if it looks bad.
if [ $? -gt 0 ]; then
  echo "Kernel build failed!"
  exit 32
fi

# Copy the kernel package to the staging area as a separate package.
cp $SRC_DIR/$PKG_NAME.tar.gz $STAGING_DIR/../$PKG_NAME.i586.tar.gz

# Create the kernel headers package
if ! [ "$PKG_COMMAND" = "" ]; then
  export $PKG_NAME $STAGING_DIR
  $PKG_COMMAND
else
  cd $STAGING_DIR
  tar -zcf ../$PKG_NAME-headers.tar.gz *
fi

# end of kernel blueprint