Enable package patching for Buildroot

The do_buildroot process now supports patching from scratch, applying
the desired packages while building rootfs.cpio with the make
build-linux-image target. The desired packages should be stored in the
tests/system/br_pkgs/ .

TODO:
The package patching from submodule might be supported in the future.
For example, Doom and Quake.

Author: ChinYikMing

tools/build-linux-image.sh

@@ -23,32 +23,140 @@ PARALLEL="-j$(nproc)"
 
 OUTPUT_DIR=./build/linux-image/
 
+BR_PKG_DIR=./tests/system/br_pkgs
+
+function create_br_pkg_config()
+{
+    local pkg_name=$1
+    local output_path=$2
+
+    cat << EOF > "${output_path}"
+config BR2_PACKAGE_${pkg_name^^}
+    bool "${pkg_name}"
+    help
+        ${pkg_name} package.
+EOF
+}
+
+function create_br_pkg_makefile()
+{
+    local pkg_name=$1
+    local output_path=$2
+
+    cat << EOF > "${output_path}"
+################################################################################
+#
+# ${pkg_name} package
+#
+################################################################################
+
+${pkg_name^^}_VERSION = 1.0
+${pkg_name^^}_SITE = package/${pkg_name}/src
+${pkg_name^^}_SITE_METHOD = local
+
+define ${pkg_name^^}_BUILD_CMDS
+	\$(MAKE) CC="\$(TARGET_CC)" LD="\$(TARGET_LD)" -C \$(@D)
+endef
+
+define ${pkg_name^^}_INSTALL_TARGET_CMDS
+	\$(INSTALL) -D -m 0755 \$(@D)/${pkg_name} \$(TARGET_DIR)/usr/bin
+endef
+
+\$(eval \$(generic-package))
+EOF
+}
+
+function create_br_pkg_src()
+{
+    local pkg_name=$1
+    local src_c_file=$2
+    local output_path=$3
+    local mk_output_path=$3/Makefile
+    local src_output_path=$3/$pkg_name.c
+
+    # Create src directory
+    mkdir -p ${output_path}
+
+    # Create makefile
+    # the output binary is in lowercase
+    cat << EOF > "${mk_output_path}"
+all:
+	\$(CC) ${pkg_name}.c -o ${pkg_name}
+EOF
+
+    # moving C source file
+    cp -f ${src_c_file} ${src_output_path}
+}
+
+function update_br_pkg_config()
+{
+    local pkg_name=$1
+    local br_pkg_config_file="${SRC_DIR}/buildroot/package/Config.in"
+    local source_line="    source \"package/${pkg_name}/Config.in\""
+
+    # Only append if this package's isn't already present in the menu
+    if ! grep -q "${pkg_name}" "${br_pkg_config_file}"; then
+        sed -i '/^menu "Custom packages"/,/^endmenu$/{
+            /^endmenu$/i\
+'"${source_line}"'
+        }' "${br_pkg_config_file}"
+    fi
+}
+
+# This function patches the packages when building the rootfs.cpio from scratch
+function do_patch_buildroot
+{
+    local br_pkg_config_file="${SRC_DIR}/buildroot/package/Config.in"
+
+    # Only append if the custom packages menu block isn't already present in the menu
+    if ! grep -q "Custom packages" "${br_pkg_config_file}"; then
+        cat << EOF >> "${br_pkg_config_file}"
+menu "Custom packages"
+endmenu
+EOF
+    fi
+
+    for c in $(find ${BR_PKG_DIR} -type f); do
+        local basename="$(basename ${c})"
+        local pkg_name="${basename%.*}"
+
+        mkdir -p ${SRC_DIR}/buildroot/package/${pkg_name}
+
+        create_br_pkg_config ${pkg_name} ${SRC_DIR}/buildroot/package/${pkg_name}/Config.in
+        create_br_pkg_makefile ${pkg_name} ${SRC_DIR}/buildroot/package/${pkg_name}/${pkg_name}.mk
+        create_br_pkg_src ${pkg_name} ${c} ${SRC_DIR}/buildroot/package/${pkg_name}/src
+
+        update_br_pkg_config ${pkg_name}
+    done
+}
+
 function do_buildroot
 {
-    cp -f assets/system/configs/buildroot.config $SRC_DIR/buildroot/.config
-    cp -f assets/system/configs/busybox.config $SRC_DIR/buildroot/busybox.config
+    cp -f assets/system/configs/buildroot.config ${SRC_DIR}/buildroot/.config
+    cp -f assets/system/configs/busybox.config ${SRC_DIR}/buildroot/busybox.config
     # Otherwise, the error below raises:
     #   You seem to have the current working directory in your
     #   LD_LIBRARY_PATH environment variable. This doesn't work.
     unset LD_LIBRARY_PATH
-    pushd $SRC_DIR/buildroot
+    do_patch_buildroot
+    pushd ${SRC_DIR}/buildroot
     ASSERT make olddefconfig
-    ASSERT make $PARALLEL
+    ASSERT make ${PARALLEL}
     popd
-    cp -f $SRC_DIR/buildroot/output/images/rootfs.cpio $OUTPUT_DIR
+    cp -f ${SRC_DIR}/buildroot/output/images/rootfs.cpio ${OUTPUT_DIR}
 }
 
 function do_linux
 {
-    cp -f assets/system/configs/linux.config $SRC_DIR/linux/.config
-    export PATH="$SRC_DIR/buildroot/output/host/bin:$PATH"
+    cp -f assets/system/configs/linux.config ${SRC_DIR}/linux/.config
+    export PATH="${SRC_DIR}/buildroot/output/host/bin:${PATH}"
     export CROSS_COMPILE=riscv32-buildroot-linux-gnu-
     export ARCH=riscv
-    pushd $SRC_DIR/linux
+    pushd ${SRC_DIR}/linux
     ASSERT make olddefconfig
-    ASSERT make $PARALLEL
+    ASSERT make ${PARALLEL}
     popd
-    cp -f $SRC_DIR/linux/arch/riscv/boot/Image $OUTPUT_DIR
+    cp -f ${SRC_DIR}/linux/arch/riscv/boot/Image ${OUTPUT_DIR}
 }
 
 do_buildroot && OK