#!/bin/bash
set -eux

SANITIZER=${SANITIZER:-address}
flags="-O1 -fno-omit-frame-pointer -g -DFUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION -fsanitize=$SANITIZER -fsanitize=fuzzer-no-link"

export CC=${CC:-clang}
export CFLAGS=${CFLAGS:-$flags}

export CXX=${CXX:-clang++}
export CXXFLAGS=${CXXFLAGS:-$flags}

cd "$(dirname -- "$0")/.."

export OUT=${OUT:-"$(pwd)/out"}
mkdir -p "$OUT"

export LIB_FUZZING_ENGINE=${LIB_FUZZING_ENGINE:--fsanitize=fuzzer}

# Ideally libbelf should be built using release tarballs available
# at https://sourceware.org/elfutils/ftp/. Unfortunately sometimes they
# fail to compile (for example, elfutils-0.185 fails to compile with LDFLAGS enabled
# due to https://bugs.gentoo.org/794601) so let's just point the script to
# commits referring to versions of libelf that actually can be built
rm -rf elfutils
git clone git://sourceware.org/git/elfutils.git
(
cd elfutils
git checkout 983e86fd89e8bf02f2d27ba5dce5bf078af4ceda
git log --oneline -1

# ASan isn't compatible with -Wl,--no-undefined: https://github.com/google/sanitizers/issues/380
find -name Makefile.am | xargs sed -i 's/,--no-undefined//'

# ASan isn't compatible with -Wl,-z,defs either:
# https://clang.llvm.org/docs/AddressSanitizer.html#usage
sed -i 's/^\(ZDEFS_LDFLAGS=\).*/\1/' configure.ac


autoreconf -i -f
if ! ./configure --enable-maintainer-mode --disable-debuginfod --disable-libdebuginfod \
	    CC="$CC" CFLAGS="-Wno-error $CFLAGS" CXX="$CXX" CXXFLAGS="-Wno-error $CXXFLAGS" LDFLAGS="$CFLAGS"; then
    cat config.log
    exit 1
fi

make -C config -j$(nproc) V=1
make -C lib -j$(nproc) V=1
make -C libelf -j$(nproc) V=1
)

make -C src BUILD_STATIC_ONLY=y V=1 clean
make -C src -j$(nproc) CFLAGS="-I$(pwd)/elfutils/libelf $CFLAGS" BUILD_STATIC_ONLY=y V=1

$CC $CFLAGS -Isrc -Iinclude -Iinclude/uapi -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64  -c fuzz/bpf-object-fuzzer.c -o bpf-object-fuzzer.o
$CXX $CXXFLAGS $LIB_FUZZING_ENGINE bpf-object-fuzzer.o src/libbpf.a "$(pwd)/elfutils/libelf/libelf.a" -l:libz.a -o "$OUT/bpf-object-fuzzer"

cp fuzz/bpf-object-fuzzer_seed_corpus.zip "$OUT"