kernel-patch

#!/bin/bash

dir_linux=/usr/src/linux
dir_distfiles=/usr/src/distfiles

usage() {
	echo >&2 "Usage: $0 [ver_to]"
	echo >&2
	echo >&2 'If version is not specified, latest patchset for same'
	echo >&2 ' major version is scraped from kernel.org and downloaded.'
	exit 1
}
[[ "$#" -gt 1 || "$1" = -h || "$1" = --help ]] && usage
v1=$1

[[ -r /usr/src/distfiles ]] || { echo >&2 "ERROR: no access to $dir_distfiles"; exit 1; }

cd "$dir_linux" && [[ -e Makefile ]]\
	|| { echo >&2 "ERROR: Failed to find Makefile in $dir_linux"; exit 1; }

v0=$( awk '$1=="VERSION" {v1=$3}
	$1=="PATCHLEVEL" {v2=$3}
	$1=="SUBLEVEL" {v3=$3; v3_set=1}
	v1 && v2 && v3_set {print v1 "." v2 "." v3; exit}' Makefile )
[[ -n "$v0" ]] || { echo >&2 "ERROR: Failed to get current sources version"; exit 1; }

[[ -n "$v1" ]] || {
	releases=(  )
	for v1 in $(
		curl -SsL 'https://www.kernel.org' |
			grep -oP '(?<=<strong>)[0-9.]+(?=</strong>)' ) fail
	do [[ ${v1%.*} != ${v0%.*} ]] || break
	done
	[[ "$v1" != fail ]] || {
		echo >&2 "ERROR: Failed to scrape matching release from kernel.org"; exit 1; }
}
[[ "$v0" != "$v1" ]] || exit 0

patch0="$dir_distfiles"/patch-$v0.zst
[[ -e "$patch0" ]] || patch0="${patch0%.zst}".xz
patch1="$dir_distfiles"/patch-$v1.zst
[[ -e "$patch1" ]] || patch1="${patch1%.zst}".xz

[[ -e "$patch1" ]] \
	|| curl -SsL -o  "$patch1" \
		"https://cdn.kernel.org/pub/linux/kernel/v${v1%%.*}.x/patch-$v1.xz" \
	|| { echo >&2 "ERROR: Failed to download patch: $v1"; exit 1; }

[[ "${v0##*.}" == 0 ]] || {
	bsdcat "$patch0" | patch --batch --follow-symlinks -p1 -R --dry-run
	[[ ${PIPESTATUS[0]} -ne 0 || ${PIPESTATUS[1]} -ne 0 ]] && exit 1
	bsdcat "$patch0" | patch --batch --follow-symlinks -p1 -R
	[[ ${PIPESTATUS[0]} -ne 0 || ${PIPESTATUS[1]} -ne 0 ]] && exit 1
}

bsdcat "$patch1" | patch --batch --follow-symlinks -p1 -N --dry-run
[[ ${PIPESTATUS[0]} -ne 0 || ${PIPESTATUS[1]} -ne 0 ]] && exit 1
bsdcat "$patch1" | patch --batch --follow-symlinks -p1 -N
[[ ${PIPESTATUS[0]} -ne 0 || ${PIPESTATUS[1]} -ne 0 ]] && exit 1

[[ -e .config ]] && make oldconfig

exit 0