kpatch/kpatch-build/kpatch-build

#!/bin/bash
#
# kpatch build script
#
# Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
# Copyright (C) 2013,2014 Josh Poimboeuf <jpoimboe@redhat.com>
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 2
# of the License, or (at your option) any later version.
#
# This program 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.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA,
# 02110-1301, USA.

# This script takes a patch based on the version of the kernel
# currently running and creates a kernel module that will
# replace modified functions in the kernel such that the
# patched code takes effect.

# This script:
# - Either uses a specified kernel source directory or downloads the kernel
#   source package for the currently running kernel
# - Unpacks and prepares the source package for building if necessary
# - Builds the base kernel or module
# - Builds the patched kernel/module and monitors changed objects
# - Builds the patched objects with gcc flags -f[function|data]-sections
# - Runs kpatch tools to create and link the patch kernel module

set -o pipefail

BASE="$PWD"
SCRIPTDIR="$(readlink -f "$(dirname "$(type -p "$0")")")"
ARCH="$(uname -m)"
CPUS="$(getconf _NPROCESSORS_ONLN)"
CACHEDIR="${CACHEDIR:-$HOME/.kpatch}"
SRCDIR="$CACHEDIR/src"
RPMTOPDIR="$CACHEDIR/buildroot"
VERSIONFILE="$CACHEDIR/version"
TEMPDIR="$CACHEDIR/tmp"
LOGFILE="$CACHEDIR/build.log"
DEBUG=0
SKIPCLEANUP=0
SKIPGCCCHECK=0
ARCH_KCFLAGS=""
declare -a PATCH_LIST
APPLIED_PATCHES=0
OOT_MODULE=

warn() {
	echo "ERROR: $1" >&2
}

die() {
	if [[ -z "$1" ]]; then
		msg="kpatch build failed"
	else
		msg="$1"
	fi

	if [[ -e "$LOGFILE" ]]; then
		warn "$msg. Check $LOGFILE for more details."
	else
		warn "$msg."
	fi

	exit 1
}

logger() {
	local to_stdout=${1:-0}

	if [[ $DEBUG -ge 2 ]] || [[ "$to_stdout" -eq 1 ]]; then
		# Log to both stdout and the logfile
		tee -a "$LOGFILE"
	else
		# Log only to the logfile
		cat >> "$LOGFILE"
	fi
}

apply_patches() {
	local patch

	for patch in "${PATCH_LIST[@]}"; do
		patch -N -p1 --dry-run < "$patch" 2>&1 | logger || die "$patch file failed to apply"
		patch -N -p1 < "$patch" 2>&1 | logger || die "$patch file failed to apply"
		(( APPLIED_PATCHES++ ))
	done
}

remove_patches() {
	local patch
	local idx

	for (( ; APPLIED_PATCHES>0; APPLIED_PATCHES-- )); do
		idx=$(( APPLIED_PATCHES - 1))
		patch="${PATCH_LIST[$idx]}"
		patch -p1 -R -d "$SRCDIR" < "$patch" &> /dev/null
	done

	# If $SRCDIR was a git repo, make sure git actually sees that
	# we've reverted our patch(es).
	[[ -d "$SRCDIR/.git" ]] && (cd "$SRCDIR" && git update-index -q --refresh)
}

cleanup() {
	rm -f "$SRCDIR/.scmversion"

	remove_patches

	# restore original vmlinux if it was overwritten by sourcedir build
	[[ -e "$TEMPDIR/vmlinux" ]] && mv -f "$TEMPDIR/vmlinux" "$SRCDIR/"

	[[ "$DEBUG" -eq 0 ]] && rm -rf "$TEMPDIR"
	rm -rf "$RPMTOPDIR"
	unset KCFLAGS
	unset KCPPFLAGS
}

clean_cache() {
	rm -rf "${CACHEDIR:?}"/*
	mkdir -p "$TEMPDIR" || die "Couldn't create $TEMPDIR"
}

check_pipe_status() {
	rc="${PIPESTATUS[0]}"
	if [[ "$rc" = 139 ]]; then
		# There doesn't seem to be a consistent/portable way of
		# accessing the last executed command in bash, so just
		# pass in the script name for now..
		warn "$1 SIGSEGV"
		if ls core* &> /dev/null; then
			cp core* /tmp
			die "core file at /tmp/$(ls core*)"
		fi
		die "no core file found, run 'ulimit -c unlimited' and try to recreate"
	fi
}

# $1 >= $2
version_gte() {
	[  "$1" = "$(echo -e "$1\\n$2" | sort -rV | head -n1)" ]
}

is_rhel() {
	[[ $1 =~ \.el[78]\. ]]
}

find_dirs() {
	if [[ -e "$SCRIPTDIR/create-diff-object" ]]; then
		# git repo
		TOOLSDIR="$SCRIPTDIR"
		DATADIR="$(readlink -f "$SCRIPTDIR/../kmod")"
		PLUGINDIR="$(readlink -f "$SCRIPTDIR/gcc-plugins")"
	elif [[ -e "$SCRIPTDIR/../libexec/kpatch/create-diff-object" ]]; then
		# installation path
		TOOLSDIR="$(readlink -f "$SCRIPTDIR/../libexec/kpatch")"
		DATADIR="$(readlink -f "$SCRIPTDIR/../share/kpatch")"
		PLUGINDIR="$TOOLSDIR"
	else
		return 1
	fi
}

find_core_symvers() {
	SYMVERSFILE=""
	if [[ -e "$SCRIPTDIR/create-diff-object" ]]; then
		# git repo
		SYMVERSFILE="$DATADIR/core/Module.symvers"
	elif [[ -e "$SCRIPTDIR/../libexec/kpatch/create-diff-object" ]]; then
		# installation path
		if [[ -e "$SCRIPTDIR/../lib/kpatch/$ARCHVERSION/Module.symvers" ]]; then
			SYMVERSFILE="$(readlink -f "$SCRIPTDIR/../lib/kpatch/$ARCHVERSION/Module.symvers")"
		elif [[ -e /lib/modules/$ARCHVERSION/extra/kpatch/Module.symvers ]]; then
			SYMVERSFILE="$(readlink -f "/lib/modules/$ARCHVERSION/extra/kpatch/Module.symvers")"
		fi
	fi

	[[ -e "$SYMVERSFILE" ]]
}

gcc_version_from_file() {
	readelf -p .comment "$1" | grep -o 'GCC:.*' | head -n 1
}

gcc_version_check() {
	local c="$TEMPDIR/test.c" o="$TEMPDIR/test.o"
	local out gccver kgccver

	# gcc --version varies between distributions therefore extract version
	# by compiling a test file and compare it to vmlinux's version.
	echo 'void main(void) {}' > "$c"
	out="$(gcc -c -pg -ffunction-sections -o "$o" "$c" 2>&1)"
	gccver="$(gcc_version_from_file "$o")"
	if [[ -n "$OOT_MODULE" ]]; then
		kgccver="$(gcc_version_from_file "$OOT_MODULE")"
	else
		kgccver="$(gcc_version_from_file "$VMLINUX")"
	fi
	rm -f "$c" "$o"

	if [[ -n "$out" ]]; then
		warn "gcc >= 4.8 required for -pg -ffunction-settings"
		echo "gcc output: $out"
		return 1
	fi

	# ensure gcc version matches that used to build the kernel
	if [[ "$gccver" != "$kgccver" ]]; then
		warn "gcc/kernel version mismatch"
		echo "gcc version:    $gccver"
		echo "kernel version: $kgccver"
		echo "Install the matching gcc version (recommended) or use --skip-gcc-check"
		echo "to skip the version matching enforcement (not recommended)"
		return 1
	fi

	return
}

find_special_section_data_ppc64le() {

	[[ "$CONFIG_JUMP_LABEL" -eq 0 ]] && AWK_OPTIONS="-vskip_j=1"

	SPECIAL_VARS="$(readelf -wi "$VMLINUX" |
		gawk --non-decimal-data '
		BEGIN { f = b = e = j = 0 }

		# Set state if name matches
		f == 0 && /DW_AT_name.* fixup_entry[[:space:]]*$/ {f = 1; next}
		b == 0 && /DW_AT_name.* bug_entry[[:space:]]*$/ {b = 1; next}
		e == 0 && /DW_AT_name.* exception_table_entry[[:space:]]*$/ {e = 1; next}
		j == 0 && /DW_AT_name.* jump_entry[[:space:]]*$/ {j = 1; next}

		# Reset state unless this abbrev describes the struct size
		f == 1 && !/DW_AT_byte_size/ { f = 0; next }
		b == 1 && !/DW_AT_byte_size/ { b = 0; next }
		e == 1 && !/DW_AT_byte_size/ { e = 0; next }
		j == 1 && !/DW_AT_byte_size/ { j = 0; next }

		# Now that we know the size, stop parsing for it
		f == 1 {printf("export FIXUP_STRUCT_SIZE=%d\n", $4); f = 2}
		b == 1 {printf("export BUG_STRUCT_SIZE=%d\n", $4); b = 2}
		e == 1 {printf("export EX_STRUCT_SIZE=%d\n", $4); e = 2}
		j == 1 {printf("export JUMP_STRUCT_SIZE=%d\n", $4); j = 2}

		# Bail out once we have everything
		f == 2 && b == 2 && e == 2 && (j == 2 || skip_j) {exit}')"

	[[ -n "$SPECIAL_VARS" ]] && eval "$SPECIAL_VARS"

	[[ -z "$FIXUP_STRUCT_SIZE" ]] && die "can't find special struct fixup_entry size"
	[[ -z "$BUG_STRUCT_SIZE" ]] && die "can't find special struct bug_entry size"
	[[ -z "$EX_STRUCT_SIZE" ]]  && die "can't find special struct exception_table_entry size"
	[[ -z "$JUMP_STRUCT_SIZE" && "$CONFIG_JUMP_LABEL" -ne 0 ]]  && die "can't find special struct jump_entry size"

	return
}

find_special_section_data() {
	if [[ "$ARCH" = "ppc64le" ]]; then
		find_special_section_data_ppc64le
		return
	fi

	[[ "$CONFIG_PARAVIRT" -eq 0 ]] && AWK_OPTIONS="-vskip_p=1"
	[[ "$CONFIG_UNWINDER_ORC" -eq 0 ]] && AWK_OPTIONS="$AWK_OPTIONS -vskip_o=1"
	[[ "$CONFIG_JUMP_LABEL" -eq 0 ]] && AWK_OPTIONS="$AWK_OPTIONS -vskip_j=1"

	# If $AWK_OPTIONS are blank gawk would treat "" as a blank script
	# shellcheck disable=SC2086
	SPECIAL_VARS="$(readelf -wi "$VMLINUX" |
		gawk --non-decimal-data $AWK_OPTIONS '
		BEGIN { a = b = p = e = o = j = 0 }

		# Set state if name matches
		a == 0 && /DW_AT_name.* alt_instr[[:space:]]*$/ {a = 1; next}
		b == 0 && /DW_AT_name.* bug_entry[[:space:]]*$/ {b = 1; next}
		p == 0 && /DW_AT_name.* paravirt_patch_site[[:space:]]*$/ {p = 1; next}
		e == 0 && /DW_AT_name.* exception_table_entry[[:space:]]*$/ {e = 1; next}
		o == 0 && /DW_AT_name.* orc_entry[[:space:]]*$/ {o = 1; next}
		j == 0 && /DW_AT_name.* jump_entry[[:space:]]*$/ {j = 1; next}

		# Reset state unless this abbrev describes the struct size
		a == 1 && !/DW_AT_byte_size/ { a = 0; next }
		b == 1 && !/DW_AT_byte_size/ { b = 0; next }
		p == 1 && !/DW_AT_byte_size/ { p = 0; next }
		e == 1 && !/DW_AT_byte_size/ { e = 0; next }
		o == 1 && !/DW_AT_byte_size/ { o = 0; next }
		j == 1 && !/DW_AT_byte_size/ { j = 0; next }

		# Now that we know the size, stop parsing for it
		a == 1 {printf("export ALT_STRUCT_SIZE=%d\n", $4); a = 2}
		b == 1 {printf("export BUG_STRUCT_SIZE=%d\n", $4); b = 2}
		p == 1 {printf("export PARA_STRUCT_SIZE=%d\n", $4); p = 2}
		e == 1 {printf("export EX_STRUCT_SIZE=%d\n", $4); e = 2}
		o == 1 {printf("export ORC_STRUCT_SIZE=%d\n", $4); o = 2}
		j == 1 {printf("export JUMP_STRUCT_SIZE=%d\n", $4); j = 2}

		# Bail out once we have everything
		a == 2 && b == 2 && (p == 2 || skip_p) && e == 2 && (o == 2 || skip_o) && (j == 2 || skip_j) {exit}')"

	[[ -n "$SPECIAL_VARS" ]] && eval "$SPECIAL_VARS"

	[[ -z "$ALT_STRUCT_SIZE" ]] && die "can't find special struct alt_instr size"
	[[ -z "$BUG_STRUCT_SIZE" ]] && die "can't find special struct bug_entry size"
	[[ -z "$EX_STRUCT_SIZE" ]]  && die "can't find special struct paravirt_patch_site size"
	[[ -z "$PARA_STRUCT_SIZE" && "$CONFIG_PARAVIRT" -ne 0 ]] && die "can't find special struct paravirt_patch_site size"
	[[ -z "$ORC_STRUCT_SIZE" && "$CONFIG_UNWINDER_ORC" -ne 0 ]] && die "can't find special struct orc_entry size"
	[[ -z "$JUMP_STRUCT_SIZE" && "$CONFIG_JUMP_LABEL" -ne 0 ]] && die "can't find special struct jump_entry size"

	return
}

find_parent_obj() {
	dir="$(dirname "$1")"
	absdir="$(readlink -f "$dir")"
	pwddir="$(readlink -f .)"
	pdir="${absdir#$pwddir/}"
	file="$(basename "$1")"
	grepname="${1%.o}"
	grepname="$grepname\\.o"
	if [[ "$DEEP_FIND" -eq 1 ]]; then
		num=0
		if [[ -n "$last_deep_find" ]]; then
			parent="$(grep -l "$grepname" "$last_deep_find"/.*.cmd | grep -Fv "$pdir/.${file}.cmd" | head -n1)"
			num="$(grep -l "$grepname" "$last_deep_find"/.*.cmd | grep -Fvc "$pdir/.${file}.cmd")"
		fi
		if [[ "$num" -eq 0 ]]; then
			parent="$(find . -name ".*.cmd" -print0 | xargs -0 grep -l "$grepname" | grep -Fv "$pdir/.${file}.cmd" | cut -c3- | head -n1)"
			num="$(find . -name ".*.cmd" -print0 | xargs -0 grep -l "$grepname" | grep -Fvc "$pdir/.${file}.cmd")"
			[[ "$num" -eq 1 ]] && last_deep_find="$(dirname "$parent")"
		fi
	else
		parent="$(grep -l "$grepname" "$dir"/.*.cmd | grep -Fv "$dir/.${file}.cmd" | head -n1)"
		num="$(grep -l "$grepname" "$dir"/.*.cmd | grep -Fvc "$dir/.${file}.cmd")"
	fi

	[[ "$num" -eq 0 ]] && PARENT="" && return
	[[ "$num" -gt 1 ]] && ERROR_IF_DIFF="two parent matches for $1"

	dir="$(dirname "$parent")"
	PARENT="$(basename "$parent")"
	PARENT="${PARENT#.}"
	PARENT="${PARENT%.cmd}"
	PARENT="$dir/$PARENT"
	[[ ! -e "$PARENT" ]] && die "ERROR: can't find parent $PARENT for $1"
}

find_kobj() {
	arg="$1"
	KOBJFILE="$arg"
	DEEP_FIND=0
	ERROR_IF_DIFF=
	while true; do
		find_parent_obj "$KOBJFILE"
		[[ -n "$PARENT" ]] && DEEP_FIND=0
		if [[ -z "$PARENT" ]]; then
			[[ "$KOBJFILE" = *.ko ]] && return
			case "$KOBJFILE" in
				*/built-in.o|\
				*/built-in.a|\
				arch/x86/lib/lib.a|\
				arch/x86/kernel/head*.o|\
				arch/x86/kernel/ebda.o|\
				arch/x86/kernel/platform-quirks.o|\
				lib/lib.a)
					KOBJFILE=vmlinux
					return
			esac
			if [[ "$DEEP_FIND" -eq 0 ]]; then
				DEEP_FIND=1
				continue;
			fi
			die "invalid ancestor $KOBJFILE for $arg"
		fi
		KOBJFILE="$PARENT"
	done
}

# Only allow alphanumerics and '_' and '-' in the module name.  Everything else
# is replaced with '-'.  Also truncate to 48 chars so the full name fits in the
# kernel's 56-byte module name array.
module_name_string() {
	echo "${1//[^a-zA-Z0-9_-]/-}" | cut -c 1-48
}

usage() {
	echo "usage: $(basename "$0") [options] <patch1 ... patchN>" >&2
	echo "		patchN             Input patchfile(s)" >&2
	echo "		-h, --help         Show this help message" >&2
	echo "		-a, --archversion  Specify the kernel arch version" >&2
	echo "		-r, --sourcerpm    Specify kernel source RPM" >&2
	echo "		-s, --sourcedir    Specify kernel source directory" >&2
	echo "		-c, --config       Specify kernel config file" >&2
	echo "		-v, --vmlinux      Specify original vmlinux" >&2
	echo "		-j, --jobs         Specify the number of make jobs" >&2
	echo "		-t, --target       Specify custom kernel build targets" >&2
	echo "		-n, --name         Specify the name of the kpatch module" >&2
	echo "		-o, --output       Specify output folder" >&2
	echo "		-d, --debug        Enable 'xtrace' and keep scratch files" >&2
	echo "		                   in <CACHEDIR>/tmp" >&2
	echo "		                   (can be specified multiple times)" >&2
	echo "		-e, --oot-module   Enable patching out-of-tree module," >&2
	echo "		                   specify current version of module" >&2
	echo "		--skip-cleanup     Skip post-build cleanup" >&2
	echo "		--skip-gcc-check   Skip gcc version matching check" >&2
	echo "		                   (not recommended)" >&2
}

options="$(getopt -o ha:r:s:c:v:j:t:n:o:de: -l "help,archversion:,sourcerpm:,sourcedir:,config:,vmlinux:,jobs:,target:,name:,output:,oot-module:,debug,skip-gcc-check,skip-cleanup" -- "$@")" || die "getopt failed"

eval set -- "$options"

while [[ $# -gt 0 ]]; do
	case "$1" in
	-h|--help)
		usage
		exit 0
		;;
	-a|--archversion)
		ARCHVERSION="$2"
		shift
		;;
	-r|--sourcerpm)
		[[ ! -f "$2" ]] && die "source rpm '$2' not found"
		SRCRPM="$(readlink -f "$2")"
		shift
		;;
	-s|--sourcedir)
		[[ ! -d "$2" ]] && die "source dir '$2' not found"
		USERSRCDIR="$(readlink -f "$2")"
		shift
		;;
	-c|--config)
		[[ ! -f "$2" ]] && die "config file '$2' not found"
		CONFIGFILE="$(readlink -f "$2")"
		shift
		;;
	-v|--vmlinux)
		[[ ! -f "$2" ]] && die "vmlinux file '$2' not found"
		VMLINUX="$(readlink -f "$2")"
		shift
		;;
	-j|--jobs)
		[[ ! "$2" -gt 0 ]] && die "Invalid number of make jobs '$2'"
		CPUS="$2"
		shift
		;;
	-t|--target)
		TARGETS="$TARGETS $2"
		shift
		;;
	-n|--name)
		MODNAME="$(module_name_string "$2")"
		shift
		;;
	-o|--output)
		[[ ! -d "$2" ]] && die "output dir '$2' not found"
		BASE="$(readlink -f "$2")"
		shift
		;;
	-d|--debug)
		DEBUG=$((DEBUG + 1))
		if [[ $DEBUG -eq 1 ]]; then
			echo "DEBUG mode enabled"
		fi
		;;
	-e|--oot-module)
		[[ ! -f "$2" ]] && die "out-of-tree module '$2' not found"
		OOT_MODULE="$(readlink -f "$2")"
		shift
		;;
	--skip-cleanup)
		echo "Skipping cleanup"
		SKIPCLEANUP=1
		;;
	--skip-gcc-check)
		echo "WARNING: Skipping gcc version matching check (not recommended)"
		SKIPGCCCHECK=1
		;;
	*)
		[[ "$1" = "--" ]] && shift && continue
		[[ ! -f "$1" ]] && die "patch file '$1' not found"
		PATCH_LIST+=("$(readlink -f "$1")")
		;;
	esac
	shift
done

if [[ ${#PATCH_LIST[@]} -eq 0 ]]; then
	warn "no patch file(s) specified"
	usage
	exit 1
fi

if [[ $DEBUG -eq 1 ]] || [[ $DEBUG -ge 3 ]]; then
	set -o xtrace
fi

if [[ -n "$ARCHVERSION" ]] && [[ -n "$VMLINUX" ]]; then
	die "--archversion is incompatible with --vmlinux"
fi

if [[ -n "$SRCRPM" ]]; then
	if  [[ -n "$ARCHVERSION" ]]; then
		warn "--archversion is incompatible with --sourcerpm"
		exit 1
	fi
	rpmname="$(basename "$SRCRPM")"
	ARCHVERSION="${rpmname%.src.rpm}.$(uname -m)"
	ARCHVERSION="${ARCHVERSION#kernel-}"
	ARCHVERSION="${ARCHVERSION#alt-}"
fi

if [[ -n "$OOT_MODULE" ]] &&  [[ -z "$USERSRCDIR" ]]; then
	warn "--oot-module requires --sourcedir"
	exit 1
fi

# ensure cachedir and tempdir are setup properly and cleaned
mkdir -p "$TEMPDIR" || die "Couldn't create $TEMPDIR"
rm -rf "${TEMPDIR:?}"/*
rm -f "$LOGFILE"

if [[ -n "$USERSRCDIR" ]]; then
	if [[ -n "$ARCHVERSION" ]]; then
		warn "--archversion is incompatible with --sourcedir"
		exit 1
	fi
	SRCDIR="$USERSRCDIR"

	if [[ -z "$OOT_MODULE" ]]; then
		[[ -z "$VMLINUX" ]] && VMLINUX="$SRCDIR"/vmlinux
		[[ ! -e "$VMLINUX" ]] && die "can't find vmlinux"

		# Extract the target kernel version from vmlinux in this case.
		ARCHVERSION="$(strings "$VMLINUX" | grep -m 1 -e "^Linux version" | awk '{ print($3); }')"
	else
		ARCHVERSION="$(modinfo -F vermagic "$OOT_MODULE" | awk '{print $1}')"
	fi
fi

[[ -z "$ARCHVERSION" ]] && ARCHVERSION="$(uname -r)"

[[ "$SKIPCLEANUP" -eq 0 ]] && trap cleanup EXIT INT TERM HUP

KVER="${ARCHVERSION%%-*}"
if [[ "$ARCHVERSION" =~ - ]]; then
	KREL="${ARCHVERSION##*-}"
	KREL="${KREL%.*}"
fi
[[ "$ARCHVERSION" =~ .el7a. ]] && ALT="-alt"

[[ -z "$TARGETS" ]] && TARGETS="vmlinux modules"

# Don't check external file.
# shellcheck disable=SC1091
source /etc/os-release
DISTRO="$ID"
if [[ "$DISTRO" = fedora ]] || [[ "$DISTRO" = rhel ]] || [[ "$DISTRO" = ol ]] || [[ "$DISTRO" = centos ]]; then
	[[ -z "$VMLINUX" ]] && VMLINUX="/usr/lib/debug/lib/modules/$ARCHVERSION/vmlinux"
	[[ -e "$VMLINUX" ]] || die "kernel-debuginfo-$ARCHVERSION not installed"

	export PATH="/usr/lib64/ccache:$PATH"

elif [[ "$DISTRO" = ubuntu ]] || [[ "$DISTRO" = debian ]]; then
	[[ -z "$VMLINUX" ]] && VMLINUX="/usr/lib/debug/boot/vmlinux-$ARCHVERSION"

	if [[ "$DISTRO" = ubuntu ]]; then
		[[ -e "$VMLINUX" ]] || die "linux-image-$ARCHVERSION-dbgsym not installed"

	elif [[ "$DISTRO" = debian ]]; then
		[[ -e "$VMLINUX" ]] || die "linux-image-$ARCHVERSION-dbg not installed"
	fi

	export PATH="/usr/lib/ccache:$PATH"
fi

find_dirs || die "can't find supporting tools"

if [[ "$SKIPGCCCHECK" -eq 0 ]]; then
	gcc_version_check || die
fi

if [[ -n "$USERSRCDIR" ]]; then
	echo "Using source directory at $USERSRCDIR"

	# save original vmlinux before it gets overwritten by sourcedir build
	if [[ -z "$OOT_MODULE" ]] && [[ "$VMLINUX" -ef "$SRCDIR"/vmlinux ]]; then
		cp -f "$VMLINUX" "$TEMPDIR/vmlinux"
		VMLINUX="$TEMPDIR/vmlinux"
	fi

	# For external modules, use the running kernel's config
	if [[ -n "$OOT_MODULE" ]] && [[ -z "$CONFIGFILE" ]]; then
		CONFIGFILE="/boot/config-${ARCHVERSION}"
	fi

elif [[ -e "$SRCDIR"/.config ]] && [[ -e "$VERSIONFILE" ]] && [[ "$(cat "$VERSIONFILE")" = "$ARCHVERSION" ]]; then
	echo "Using cache at $SRCDIR"

else
	if [[ "$DISTRO" = fedora ]] || [[ "$DISTRO" = rhel ]] || [[ "$DISTRO" = ol ]] || [[ "$DISTRO" = centos ]]; then

		echo "Fedora/Red Hat distribution detected"

		clean_cache

		echo "Downloading kernel source for $ARCHVERSION"
		if [[ -z "$SRCRPM" ]]; then
			if [[ "$DISTRO" = fedora ]]; then
				wget -P "$TEMPDIR" "http://kojipkgs.fedoraproject.org/packages/kernel/$KVER/$KREL/src/kernel-$KVER-$KREL.src.rpm" 2>&1 | logger || die
			else
				command -v yumdownloader &>/dev/null || die "yumdownloader (yum-utils or dnf-utils) not installed"
				yumdownloader --source --destdir "$TEMPDIR" "kernel$ALT-$KVER-$KREL" 2>&1 | logger || die
			fi
			SRCRPM="$TEMPDIR/kernel$ALT-$KVER-$KREL.src.rpm"
		fi

		echo "Unpacking kernel source"

		rpm -D "_topdir $RPMTOPDIR" -ivh "$SRCRPM" 2>&1 | logger || die
		rpmbuild -D "_topdir $RPMTOPDIR" -bp --nodeps "--target=$(uname -m)" "$RPMTOPDIR"/SPECS/kernel$ALT.spec 2>&1 | logger ||
			die "rpmbuild -bp failed.  you may need to run 'yum-builddep kernel' first."

		mv "$RPMTOPDIR"/BUILD/kernel-*/linux-* "$SRCDIR" 2>&1 | logger || die
		rm -rf "$RPMTOPDIR"
		rm -rf "$SRCDIR/.git"

		if [[ "$ARCHVERSION" == *-* ]]; then
			echo "-${ARCHVERSION##*-}" > "$SRCDIR/localversion" || die
		fi

		echo "$ARCHVERSION" > "$VERSIONFILE" || die

		[[ -z "$CONFIGFILE" ]] && CONFIGFILE="$SRCDIR/configs/kernel$ALT-$KVER-$ARCH.config"

		(cd "$SRCDIR" && make mrproper 2>&1 | logger) || die

	elif [[ "$DISTRO" = ubuntu ]] || [[ "$DISTRO" = debian ]]; then

		echo "Debian/Ubuntu distribution detected"

		if [[ "$DISTRO" = ubuntu ]]; then

			# url may be changed for a different mirror
			url="http://archive.ubuntu.com/ubuntu/pool/main/l"
			sublevel="SUBLEVEL = 0"

		elif [[ "$DISTRO" = debian ]]; then

			# url may be changed for a different mirror
			url="http://ftp.debian.org/debian/pool/main/l"
			sublevel="SUBLEVEL ="
		fi

		pkgname="$(dpkg-query -W -f='${Source}' "linux-image-$ARCHVERSION" | sed s/-signed//)"
		pkgver="$(dpkg-query -W -f='${Version}' "linux-image-$ARCHVERSION")"
		dscname="${pkgname}_${pkgver}.dsc"

		clean_cache

		cd "$TEMPDIR" || die
		echo "Downloading and unpacking the kernel source for $ARCHVERSION"
		# Download source deb pkg
		(dget -u "$url/${pkgname}/${dscname}" 2>&1) | logger || die "dget: Could not fetch/unpack $url/${pkgname}/${dscname}"
		mv "${pkgname}-$KVER" "$SRCDIR" || die
		[[ -z "$CONFIGFILE" ]] && CONFIGFILE="/boot/config-${ARCHVERSION}"
		if [[ "$ARCHVERSION" == *-* ]]; then
			echo "-${ARCHVERSION#*-}" > "$SRCDIR/localversion" || die
		fi
		# for some reason the Ubuntu kernel versions don't follow the
		# upstream SUBLEVEL; they are always at SUBLEVEL 0
		sed -i "s/^SUBLEVEL.*/${sublevel}/" "$SRCDIR/Makefile" || die
		echo "$ARCHVERSION" > "$VERSIONFILE" || die

	else
		die "Unsupported distribution"
	fi
fi

[[ -z "$CONFIGFILE" ]] && CONFIGFILE="$SRCDIR"/.config
[[ ! -e "$CONFIGFILE" ]] && die "can't find config file"
[[ ! "$CONFIGFILE" -ef "$SRCDIR"/.config ]] && cp -f "$CONFIGFILE" "$SRCDIR/.config"

# Build variables - Set some defaults, then adjust features
# according to .config and kernel version
KBUILD_EXTRA_SYMBOLS=""
KPATCH_LDFLAGS=""
KPATCH_MODULE=true

# kernel option checking
grep -q "CONFIG_DEBUG_INFO=y" "$CONFIGFILE" || die "kernel doesn't have 'CONFIG_DEBUG_INFO' enabled"
if grep -q "CONFIG_LIVEPATCH=y" "$CONFIGFILE"; then
	# The kernel supports livepatch.
	if version_gte "${ARCHVERSION//-*/}" 4.7.0 || is_rhel "$ARCHVERSION"; then
		# Use new .klp.rela. sections
		KPATCH_MODULE=false
		if version_gte "${ARCHVERSION//-*/}" 4.9.0 || is_rhel "$ARCHVERSION"; then
			KPATCH_LDFLAGS="--unique=.parainstructions --unique=.altinstructions"
		fi
	fi
else
	# No support for livepatch in the kernel. Kpatch core module is needed.
	find_core_symvers || die "unable to find Module.symvers for kpatch core module"
	KBUILD_EXTRA_SYMBOLS="$SYMVERSFILE"
fi

# optional kernel configs:
if grep -q "CONFIG_PARAVIRT=y" "$CONFIGFILE"; then
	CONFIG_PARAVIRT=1
else
	CONFIG_PARAVIRT=0
fi
if grep -q "CONFIG_UNWINDER_ORC=y" "$CONFIGFILE"; then
	CONFIG_UNWINDER_ORC=1
else
	CONFIG_UNWINDER_ORC=0
fi
if grep -q "CONFIG_JUMP_LABEL=y" "$CONFIGFILE"; then
	CONFIG_JUMP_LABEL=1
else
	CONFIG_JUMP_LABEL=0
fi

# unsupported kernel option checking
grep -q "CONFIG_DEBUG_INFO_SPLIT=y" "$CONFIGFILE" && die "kernel option 'CONFIG_DEBUG_INFO_SPLIT' not supported"
grep -q "CONFIG_GCC_PLUGIN_LATENT_ENTROPY=y" "$CONFIGFILE" && die "kernel option 'CONFIG_GCC_PLUGIN_LATENT_ENTROPY' not supported"
grep -q "CONFIG_GCC_PLUGIN_RANDSTRUCT=y" "$CONFIGFILE" && die "kernel option 'CONFIG_GCC_PLUGIN_RANDSTRUCT' not supported"

echo "Testing patch file(s)"
cd "$SRCDIR" || die
apply_patches
remove_patches

cp -LR "$DATADIR/patch" "$TEMPDIR" || die

if [[ "$ARCH" = "ppc64le" ]]; then
	ARCH_KCFLAGS="-mcmodel=large -fplugin=$PLUGINDIR/ppc64le-plugin.so"
fi

export KCFLAGS="-I$DATADIR/patch -ffunction-sections -fdata-sections $ARCH_KCFLAGS"

echo "Reading special section data"
find_special_section_data

if [[ $DEBUG -ge 4 ]]; then
	export KPATCH_GCC_DEBUG=1
fi

echo "Building original source"
[[ -n "$OOT_MODULE" ]] || ./scripts/setlocalversion --save-scmversion || die
unset KPATCH_GCC_TEMPDIR
# $TARGETS used as list, no quotes.
# shellcheck disable=SC2086
CROSS_COMPILE="$TOOLSDIR/kpatch-gcc " make "-j$CPUS" $TARGETS 2>&1 | logger || die

echo "Building patched source"
apply_patches
mkdir -p "$TEMPDIR/orig" "$TEMPDIR/patched"
KPATCH_GCC_TEMPDIR="$TEMPDIR"
export KPATCH_GCC_TEMPDIR
KPATCH_GCC_SRCDIR="$SRCDIR"
export KPATCH_GCC_SRCDIR
# $TARGETS used as list, no quotes.
# shellcheck disable=SC2086
CROSS_COMPILE="$TOOLSDIR/kpatch-gcc " \
	KBUILD_MODPOST_WARN=1 \
	make "-j$CPUS" $TARGETS 2>&1 | logger || die

# source.c:(.section+0xFF): undefined reference to `symbol'
grep "undefined reference" "$LOGFILE" | sed -r "s/^.*\`(.*)'$/\\1/" \
	>"${TEMPDIR}"/undefined_references

# WARNING: "symbol" [path/to/module.ko] undefined!
grep "undefined!" "$LOGFILE" | cut -d\" -f2 >>"${TEMPDIR}"/undefined_references

if [[ ! -e "$TEMPDIR/changed_objs" ]]; then
	die "no changed objects found"
fi

[[ -n "$OOT_MODULE" ]] || grep -q vmlinux "$SRCDIR/Module.symvers" || die "truncated $SRCDIR/Module.symvers file"

# Read as words, no quotes.
# shellcheck disable=SC2013
for i in $(cat "$TEMPDIR/changed_objs")
do
	mkdir -p "$TEMPDIR/patched/$(dirname "$i")" || die
	cp -f "$SRCDIR/$i" "$TEMPDIR/patched/$i" || die
done

echo "Extracting new and modified ELF sections"
# If no kpatch module name was provided on the command line:
#   - For single input .patch, use the patch filename
#   - For multiple input .patches, use "patch"
#   - Prefix with "kpatch" or "livepatch" accordingly
if [[ -z "$MODNAME" ]] ; then
	if [[ "${#PATCH_LIST[@]}" -eq 1 ]]; then
		MODNAME="$(basename "${PATCH_LIST[0]}")"
		if [[ "$MODNAME" =~ \.patch$ ]] || [[ "$MODNAME" =~ \.diff$ ]]; then
			MODNAME="${MODNAME%.*}"
		fi
	else
		MODNAME="patch"
	fi

	if "$KPATCH_MODULE"; then
		MODNAME="kpatch-$MODNAME"
	else
		MODNAME="livepatch-$MODNAME"
	fi

	MODNAME="$(module_name_string "$MODNAME")"
fi
FILES="$(cat "$TEMPDIR/changed_objs")"
cd "$TEMPDIR" || die
mkdir output
declare -a objnames
CHANGED=0
ERROR=0
for i in $FILES; do
	# In RHEL 7 based kernels, copy_user_64.o misuses the .fixup section,
	# which confuses create-diff-object.  It's fine to skip it, it's an
	# assembly file anyway.
	[[ "$DISTRO" = rhel ]] || [[ "$DISTRO" = centos ]] || [[ "$DISTRO" = ol ]] && \
		[[ "$i" = arch/x86/lib/copy_user_64.o ]] && continue

	[[ "$i" = usr/initramfs_data.o ]] && continue

	mkdir -p "output/$(dirname "$i")"
	cd "$SRCDIR" || die
	find_kobj "$i"
	cd "$TEMPDIR" || die
	if [[ -e "orig/$i" ]]; then
		if [[ "$(basename "$KOBJFILE")" = vmlinux ]]; then
			KOBJFILE_NAME=vmlinux
			KOBJFILE_PATH="$VMLINUX"
			SYMTAB="${TEMPDIR}/${KOBJFILE_NAME}.symtab"
			SYMVERS_FILE="$SRCDIR/Module.symvers"
		elif [[ "$(basename "$KOBJFILE")" = "$(basename "$OOT_MODULE")" ]]; then
			KOBJFILE_NAME="$(basename --suffix=.ko "$OOT_MODULE")"
			KOBJFILE_PATH="$OOT_MODULE"
			SYMTAB="${TEMPDIR}/module/${KOBJFILE_NAME}.symtab"
			SYMVERS_FILE="$TEMPDIR/Module.symvers"
			BUILDDIR="/lib/modules/$ARCHVERSION/build/"
			cp "$SRCDIR/Module.symvers" "$SYMVERS_FILE"
			awk '{ print $1 "\t" $2 "\t" $3 "\t" $4}' "${BUILDDIR}/Module.symvers" >> "$SYMVERS_FILE"
		else
			KOBJFILE_NAME=$(basename "${KOBJFILE%.ko}")
			KOBJFILE_NAME="${KOBJFILE_NAME/-/_}"
			KOBJFILE_PATH="${TEMPDIR}/module/$KOBJFILE"
			SYMTAB="${KOBJFILE_PATH}.symtab"
			SYMVERS_FILE="$SRCDIR/Module.symvers"
		fi

		readelf -s --wide "$KOBJFILE_PATH" > "$SYMTAB"
		if [[ "$ARCH" = "ppc64le" ]]; then
			sed -ri 's/\s+\[<localentry>: 8\]//' "$SYMTAB"
		fi

		# create-diff-object orig.o patched.o parent-name parent-symtab
		#		     Module.symvers patch-mod-name output.o
		"$TOOLSDIR"/create-diff-object "orig/$i" "patched/$i" "$KOBJFILE_NAME" \
			"$SYMTAB" "$SYMVERS_FILE" "${MODNAME//-/_}" \
			"output/$i" 2>&1 | logger 1
		check_pipe_status create-diff-object
		# create-diff-object returns 3 if no functional change is found
		[[ "$rc" -eq 0 ]] || [[ "$rc" -eq 3 ]] || ERROR="$((ERROR + 1))"
		if [[ "$rc" -eq 0 ]]; then
			[[ -n "$ERROR_IF_DIFF" ]] && die "$ERROR_IF_DIFF"
			CHANGED=1
			objnames[${#objnames[@]}]="$KOBJFILE"
		fi
	else
		cp -f "patched/$i" "output/$i"
		objnames[${#objnames[@]}]="$KOBJFILE"
	fi
done

if [[ "$ERROR" -ne 0 ]]; then
	die "$ERROR error(s) encountered"
fi

if [[ "$CHANGED" -eq 0 ]]; then
	die "no functional changes found"
fi

echo -n "Patched objects:"
for i in $(echo "${objnames[@]}" | tr ' ' '\n' | sort -u | tr '\n' ' ')
do
	echo -n " $i"
done
echo

export KCFLAGS="-I$DATADIR/patch $ARCH_KCFLAGS"
if "$KPATCH_MODULE"; then
	export KCPPFLAGS="-D__KPATCH_MODULE__"
fi

echo "Building patch module: $MODNAME.ko"

if [[ -z "$USERSRCDIR" ]] && [[ "$DISTRO" = ubuntu ]]; then
	# UBUNTU: add UTS_UBUNTU_RELEASE_ABI to utsrelease.h after regenerating it
	UBUNTU_ABI="${ARCHVERSION#*-}"
	UBUNTU_ABI="${UBUNTU_ABI%-*}"
	echo "#define UTS_UBUNTU_RELEASE_ABI $UBUNTU_ABI" >> "$SRCDIR"/include/generated/utsrelease.h
fi

cd "$TEMPDIR/output" || die
# $KPATCH_LDFLAGS and result of find used as list, no quotes.
# shellcheck disable=SC2086,SC2046
ld -r $KPATCH_LDFLAGS -o ../patch/tmp_output.o $(find . -name "*.o") 2>&1 | logger || die

if "$KPATCH_MODULE"; then
	# Add .kpatch.checksum for kpatch script
	md5sum ../patch/tmp_output.o | awk '{printf "%s\0", $1}' > checksum.tmp || die
	objcopy --add-section .kpatch.checksum=checksum.tmp --set-section-flags .kpatch.checksum=alloc,load,contents,readonly  ../patch/tmp_output.o || die
	rm -f checksum.tmp
	"$TOOLSDIR"/create-kpatch-module "$TEMPDIR"/patch/tmp_output.o "$TEMPDIR"/patch/output.o 2>&1 | logger 1
	check_pipe_status create-kpatch-module
else
	cp "$TEMPDIR"/patch/tmp_output.o "$TEMPDIR"/patch/output.o || die
fi

cd "$TEMPDIR/patch" || die
if [[ -z "$OOT_MODULE" ]]; then
	KPATCH_BUILD="$SRCDIR"
else
	KPATCH_BUILD="/lib/modules/$ARCHVERSION/build"
fi
KPATCH_BUILD="$KPATCH_BUILD" KPATCH_NAME="$MODNAME" \
KBUILD_EXTRA_SYMBOLS="$KBUILD_EXTRA_SYMBOLS" \
KPATCH_LDFLAGS="$KPATCH_LDFLAGS" \
	make 2>&1 | logger || die

if ! "$KPATCH_MODULE"; then
	if [[ -z "$KPATCH_LDFLAGS" ]]; then
		extra_flags="--no-klp-arch-sections"
	fi
	cp "$TEMPDIR/patch/$MODNAME.ko" "$TEMPDIR/patch/tmp.ko" || die
	"$TOOLSDIR"/create-klp-module $extra_flags "$TEMPDIR/patch/tmp.ko" "$TEMPDIR/patch/$MODNAME.ko" 2>&1 | logger 1
	check_pipe_status create-klp-module
fi

readelf --wide --symbols "$TEMPDIR/patch/$MODNAME.ko" 2>/dev/null | \
	sed -r 's/\s+\[<localentry>: 8\]//' | \
	awk '($4=="FUNC" || $4=="OBJECT") && ($5=="GLOBAL" || $5=="WEAK") && $7!="UND" {print $NF}' \
	>"${TEMPDIR}"/new_symbols

if "$KPATCH_MODULE"; then
	cat >>"${TEMPDIR}"/new_symbols <<-EOF
		kpatch_shadow_free
		kpatch_shadow_alloc
		kpatch_register
		kpatch_shadow_get
		kpatch_unregister
		kpatch_root_kobj
	EOF
fi

# Compare undefined_references and new_symbols files and print only the first
# column containing lines unique to first file.
UNDEFINED=$(comm -23 <(sort -u "${TEMPDIR}"/undefined_references) \
	<(sort -u "${TEMPDIR}"/new_symbols) | tr '\n' ' ')
[[ -n "$UNDEFINED" ]] && die "Undefined symbols: $UNDEFINED"

cp -f "$TEMPDIR/patch/$MODNAME.ko" "$BASE" || die

[[ "$DEBUG" -eq 0 ]] && rm -f "$LOGFILE"

echo "SUCCESS"