#!/usr/bin/env bash
# Reproducible RT kernel for the Cuckoo Escapement release.
#
# KBUILD_BUILD_{USER,HOST,TIMESTAMP} are the whole point of this rebuild: without
# them the kernel bakes the builder's `user@hostname` and the wall-clock build
# time into /proc/version, which (a) publishes operator identity and (b) makes
# the artifact unreproducible. Pinning all three means anyone can rebuild this
# and diff the bytes.
set -euo pipefail
cd "$HOME/src"

PATCH="$(cd "$(dirname "$0")" && pwd)/0001-pps-gpio-keep-timestamp-in-hard-irq-under-PREEMPT_RT.patch"

[ -d linux ] || git clone --depth=1 --branch rpi-6.18.y https://github.com/raspberrypi/linux
cd linux

export ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu-
export KBUILD_BUILD_USER=cuckoo
export KBUILD_BUILD_HOST=escapement
export KBUILD_BUILD_TIMESTAMP='Mon Jan  1 00:00:00 UTC 2024'

make bcm2711_defconfig
./scripts/config --enable EXPERT --enable PREEMPT_RT \
                 --set-str LOCALVERSION "-rt-cuckoo" --disable LOCALVERSION_AUTO
make olddefconfig

git apply --check "$PATCH" 2>/dev/null && git apply "$PATCH" && echo "PATCH APPLIED" \
  || grep -q IRQF_NO_THREAD drivers/pps/clients/pps-gpio.c && echo "PATCH ALREADY PRESENT"

grep -q "IRQF_NO_THREAD" drivers/pps/clients/pps-gpio.c || { echo "FATAL: patch missing"; exit 1; }

make -j"$(nproc)" Image modules dtbs
echo "BUILD OK: $(cat include/config/kernel.release)"