chore: allow building CI rootfs and kernels separately

Script `resources/rebuild.sh` is used mainly to help us re-build CI
artifacts. Sometimes, for debugging we would like to be able to build
kernels or the rootfs locally. Also, we would like to be able to build
each component individually, e.g. only the root filesystem or only guest
kernel 6.1.

Make the script a bit more clever, adding options for building only
rootfs or only kernels (all of them or a single one). Leave the default
behaviour intact so we don't break any of its current users.

Signed-off-by: Babis Chalios <[email protected]>

Author: bchalios

resources/rebuild.sh

@@ -5,13 +5,15 @@
 # fail if we encounter an error, uninitialized variable or a pipe breaks
 set -eu -o pipefail
 
-set -x
 PS4='+\t '
 
 cd $(dirname $0)
 ARCH=$(uname -m)
 OUTPUT_DIR=$PWD/$ARCH
 
+GIT_ROOT_DIR=$(git rev-parse --show-toplevel)
+source "$GIT_ROOT_DIR/tools/functions"
+
 # Make sure we have all the needed tools
 function install_dependencies {
     sudo apt update
@@ -50,7 +52,7 @@ function build_rootfs {
     local flavour=${2}
     local FROM_CTR=public.ecr.aws/ubuntu/ubuntu:$flavour
     local rootfs="tmp_rootfs"
-    mkdir -pv "$rootfs" "$OUTPUT_DIR"
+    mkdir -pv "$rootfs"
 
     cp -rvf overlay/* $rootfs
 
@@ -199,31 +201,113 @@ function build_al_kernel {
     popd &>/dev/null
 }
 
-#### main ####
+function prepare_and_build_rootfs {
+    BIN=overlay/usr/local/bin
+    compile_and_install $BIN/init.c $BIN/init
+    compile_and_install $BIN/fillmem.c $BIN/fillmem
+    compile_and_install $BIN/fast_page_fault_helper.c $BIN/fast_page_fault_helper
+    compile_and_install $BIN/readmem.c $BIN/readmem
+    if [ $ARCH == "aarch64" ]; then
+        compile_and_install $BIN/devmemread.c $BIN/devmemread
+    fi
+
+    build_rootfs ubuntu-22.04 jammy
+    build_initramfs
+}
+
+function build_al_kernels {
+    if [[ $# = 0 ]]; then
+        local KERNEL_VERSION="all"
+    elif [[ $# -ne 1 ]]; then
+        die "Too many arguments in '$(basename $0) kernels' command. Please use \`$0 help\` for help."
+    else 
+        KERNEL_VERSION=$1
+        if [[ "$KERNEL_VERSION" != @(5.10|5.10-no-acpi|6.1) ]]; then
+            die "Unsupported kernel version: '$KERNEL_VERSION'. Please use \`$0 help\` for help."
+        fi
+    fi
+
+    clone_amazon_linux_repo
+
+    # Apply kernel patches on top of AL configuration
+    apply_kernel_patches_for_ci
+
+    if [[ "$KERNEL_VERSION" == @(all|5.10) ]]; then
+        build_al_kernel $PWD/guest_configs/microvm-kernel-ci-$ARCH-5.10.config
+    fi
+    if [[ $ARCH == "x86_64" && "$KERNEL_VERSION" == @(all|5.10-no-acpi) ]]; then
+        build_al_kernel $PWD/guest_configs/microvm-kernel-ci-$ARCH-5.10-no-acpi.config
+    fi
+    if [[ "$KERNEL_VERSION" == @(all|6.1) ]]; then
+        build_al_kernel $PWD/guest_configs/microvm-kernel-ci-$ARCH-6.1.config 5.10
+    fi
+}
+
+function print_help {
+    cat <<EOF
+Firecracker CI artifacts build script
+
+Usage: $(basename $0) [<command>] [<command args>]
+    
+Available commands:
+    
+    all (default)
+        Build CI rootfs and default guest kernels using configurations from
+        resources/guest_configs.
+        This will patch the guest configurations with all the patches under
+        resources/guest_configs/patches.
+        This is the default command, if no command is chosen.
+    
+    rootfs
+        Builds only the CI rootfs.
+    
+    kernels [version]
+        Builds our the currently supported CI kernels.
+    
+        version: Optionally choose a kernel version to build. Supported
+                 versions are: 5.10, 5.10-no-acpi or 6.1.
+    
+    help
+        Displays the help message and exits.
+EOF
+}
 
-install_dependencies
+function main {
+    if [[ $# = 0 ]]; then
+        local MODE="all"
+    else
+        case $1 in
+            all|rootfs|kernels)
+                local MODE=$1
+                shift
+                ;;
+            help)
+                print_help
+                exit 0
+                ;;
+            *)
+                die "Unknown command: '$1'. Please use \`$0 help\` for help."
+        esac
+    fi
 
-BIN=overlay/usr/local/bin
-compile_and_install $BIN/init.c    $BIN/init
-compile_and_install $BIN/fillmem.c $BIN/fillmem
-compile_and_install $BIN/fast_page_fault_helper.c $BIN/fast_page_fault_helper
-compile_and_install $BIN/readmem.c $BIN/readmem
-if [ $ARCH == "aarch64" ]; then
-    compile_and_install $BIN/devmemread.c $BIN/devmemread
-fi
+    set -x
+        
+    install_dependencies
 
-build_rootfs ubuntu-22.04 jammy
-build_initramfs
+    # Create the directory in which we will store the kernels and rootfs
+    mkdir -pv $OUTPUT_DIR
 
-clone_amazon_linux_repo
+    if [[ "$MODE" =~ (all|rootfs) ]]; then
+        say "Building rootfs"
+        prepare_and_build_rootfs
+    fi
 
-# Apply kernel patches on top of AL configuration
-apply_kernel_patches_for_ci
+    if [[ "$MODE" =~ (all|kernels) ]]; then
+        say "Building CI kernels"
+        build_al_kernels "$@"
+    fi
 
-build_al_kernel $PWD/guest_configs/microvm-kernel-ci-$ARCH-5.10.config
-if [ $ARCH == "x86_64" ]; then
-    build_al_kernel $PWD/guest_configs/microvm-kernel-ci-$ARCH-5.10-no-acpi.config
-fi
-build_al_kernel $PWD/guest_configs/microvm-kernel-ci-$ARCH-6.1.config
+    tree -h $OUTPUT_DIR
+}
 
-tree -h $OUTPUT_DIR
+main "$@"