chronos: Pause compile just before compiling the fuzz target so that we can reuse it later.

infra/experimental/chronos/README.md

@@ -0,0 +1,12 @@
+# Usage
+Under `OSS-Fuzz` root directory:
+```bash
+export PROJECT=libiec61850
+export FUZZ_TARGET=fuzz_mms_decode.c
+export FUZZING_LANGUAGE=c
+infra/experimental/chronos/prepare-recompile "$PROJECT" "$FUZZ_TARGET" "$FUZZING_LANGUAGE"
+python infra/helper.py build_image "$PROJECT"
+docker run -ti --entrypoint="compile" --name "${PROJECT}-origin" "gcr.io/oss-fuzz/${PROJECT}"
+docker commit "${PROJECT}-origin" "gcr.io/oss-fuzz/${PROJECT}-ofg-cached"
+docker run -ti --entrypoint="recompile" "gcr.io/oss-fuzz/${PROJECT}-ofg-cached" 
+```

infra/experimental/chronos/chronos.sh

@@ -0,0 +1,74 @@
+# Copyright 2024 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+################################################################################
+
+# This script records the ENV and commands needed for fuzz target recompilation.
+# It intercepts bash commands to save: 1) the ENV variable values before
+# building the fuzz target (`recompile_env.sh`) and 2) all subsequent bash
+# commands from that point (`recompile`). Combined with Docker, this setup
+# allows for recompiling the fuzz target without rebuilding the entire project.
+# Usage:
+# 1. Set FUZZ_TARGET (e.g., in project's Dockerfile)
+# 2. Source this file before compiling the fuzz target (e.g., source chronos.sh
+# at the beginning of project's build.sh).
+
+export START_RECORDING="false"
+RECOMPILE_ENV="/usr/local/bin/recompile_env.sh"
+
+
+# Initialize the recompile script.
+initialize_recompile_script() {
+    export RECOMPILE_SCRIPT="/usr/local/bin/recompile"
+    echo "#!/bin/bash" > "$RECOMPILE_SCRIPT"
+    echo "source $RECOMPILE_ENV" >> "$RECOMPILE_SCRIPT" 
+    chmod +x "$RECOMPILE_SCRIPT" 
+}
+
+
+# Execute or record command for recompilation.
+execute_or_record_command() {
+    record_command() {
+        echo "cd \"$(pwd)\"" >> "$RECOMPILE_SCRIPT"
+        echo "$@" >> "$RECOMPILE_SCRIPT"
+    }
+
+    # Check if any element in the command array contains the FUZZ_TARGET.
+   if [[ "$BASH_COMMAND" == *"$FUZZ_TARGET"* ]]; then
+       export START_RECORDING="true"
+       # Save all environment variables, excluding read-only ones
+       declare -p | grep -Ev 'declare -[^ ]*r[^ ]*' > "$RECOMPILE_ENV"
+   fi
+
+    if [[ "$START_RECORDING" == "true" ]]; then
+        record_command "$BASH_COMMAND"
+        echo "Recorded execution of: $BASH_COMMAND"
+    fi
+}
+
+
+main() {
+    # Initialize.
+    initialize_recompile_script
+
+    # Set up trap for DEBUG to intercept commands.
+    trap 'execute_or_record_command' DEBUG
+
+    # Enable extended debugging mode
+    shopt -s extdebug  
+    # Ensure trap works in subshells and functions.
+    set -T  
+}
+
+main

infra/experimental/chronos/prepare-recompile

@@ -0,0 +1,42 @@
+#!/usr/bin/bash
+# Copyright 2024 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+################################################################################
+
+# Prepare a project for fuzz target recompilation via chronos.sh
+# Usage:
+# (in OSS-Fuzz root dir) infra/experimental/chronos/prepare-recompile.sh <project> <fuzz-target-name> <fuzzing-language>
+# E.g.:
+#infra/experimental/chronos/prepare-recompile.sh libiec61850 fuzz_mms_decode.c c
+
+
+
+PROJECT=$1
+FUZZ_TARGET=$2
+FUZZING_LANGUAGE=$3
+
+# Step 1: Copy chronos.sh to its project directory.
+cp infra/experimental/chronos/chronos.sh "projects/$PROJECT/"
+
+# Step 2: Copy chronos.sh to image and set FUZZ_TARGET and FUZZING_LANGUAGE in its Dockerfile.
+{
+    echo "COPY chronos.sh /src";
+    echo "ENV FUZZ_TARGET=\"$FUZZ_TARGET\"";
+    echo "ENV FUZZING_LANGUAGE=\"$FUZZING_LANGUAGE\"";
+} >> "projects/$PROJECT/Dockerfile"
+
+# Step 3: Source chronos.sh at the beginning of its build.sh.
+sed -i.bak "1s|^|source \"/src/chronos.sh\"\n|" "projects/$PROJECT/build.sh"
+