Refactor the inline Python commands into a Python binary.

This is needed when `python3` does not exist in the runtime environment.

fuzzing/engines/BUILD

@@ -23,6 +23,9 @@ cc_fuzzing_engine(
     name = "libfuzzer",
     display_name = "libFuzzer",
     launcher = "libfuzzer_launcher.sh",
+    launcher_data = {
+        "//fuzzing/tools:realpath": "REALPATH_PATH",
+    },
     library = ":libfuzzer_stub",
     visibility = ["//visibility:public"],
 )
@@ -46,6 +49,7 @@ cc_fuzzing_engine(
     launcher = "honggfuzz_launcher.sh",
     launcher_data = {
         "@honggfuzz//:honggfuzz": "HONGGFUZZ_PATH",
+        "//fuzzing/tools:realpath": "REALPATH_PATH",
     },
     library = "@honggfuzz//:honggfuzz_engine",
     visibility = ["//visibility:public"],
@@ -58,6 +62,9 @@ cc_fuzzing_engine(
     name = "replay",
     display_name = "Replay",
     launcher = "replay_launcher.sh",
+    launcher_data = {
+        "//fuzzing/tools:realpath": "REALPATH_PATH",
+    },
     library = "//fuzzing/replay:replay_main",
     visibility = ["//visibility:public"],
 )
@@ -69,6 +76,9 @@ java_fuzzing_engine(
     name = "jazzer",
     display_name = "Jazzer",
     launcher = "jazzer_launcher.sh",
+    launcher_data = {
+        "//fuzzing/tools:realpath": "REALPATH_PATH",
+    },
     library = "@jazzer//agent:jazzer_api_compile_only",
     visibility = ["//visibility:public"],
 )

fuzzing/private/engine.bzl

@@ -37,9 +37,12 @@ def _make_fuzzing_engine_info(ctx):
         if data_env_var:
             if data_env_var in env_vars:
                 fail("Multiple data dependencies map to variable '%s'." % data_env_var)
-            if len(data_files) != 1:
-                fail("Data dependency for variable '%s' doesn't map to exactly one file." % data_env_var)
-            env_vars[data_env_var] = data_files[0]
+            if len(data_files) == 1:
+                env_vars[data_env_var] = data_files[0]
+            elif data_label.files_to_run.executable:
+                env_vars[data_env_var] = data_label.files_to_run.executable
+            else:
+                fail("Data dependency for variable '%s' is not a single file or executable." % data_env_var)
         launcher_runfiles = launcher_runfiles.merge(ctx.runfiles(files = data_files))
         launcher_runfiles = launcher_runfiles.merge(data_label[DefaultInfo].default_runfiles)
 

fuzzing/private/java_utils.bzl

@@ -106,18 +106,18 @@ source "$(grep -sm1 "^$f " "$0.exe.runfiles_manifest" | cut -f2- -d' ')" 2>/dev/
 
 # Export the env variables required for subprocesses to find their runfiles.
 runfiles_export_envvars
+"""
 
+    script_format_part = """
 # Determine the path to load libjvm.so from, either relative to the location of
 # the java binary or to $JAVA_HOME, if set. On OSS-Fuzz, the path is provided in
 # JVM_LD_LIBRARY_PATH.
-JAVA_BIN=$(python3 -c 'import os, sys; print(os.path.realpath(sys.argv[1]))' "$(which java)")
-JAVA_HOME=${JAVA_HOME:-${JAVA_BIN%/bin/java}}
+JAVA_BIN=$("$(rlocation {realpath})" "$(which java)")
+JAVA_HOME=${{JAVA_HOME:-${{JAVA_BIN%/bin/java}}}}
 # The location of libjvm.so relative to the JDK differs between JDK <= 8 and 9+.
-JVM_LD_LIBRARY_PATH=${JVM_LD_LIBRARY_PATH:-"$JAVA_HOME/lib/server:$JAVA_HOME/lib/amd64/server"}
-export LD_LIBRARY_PATH=${LD_LIBRARY_PATH:+$LD_LIBRARY_PATH:}$JVM_LD_LIBRARY_PATH
-"""
+JVM_LD_LIBRARY_PATH=${{JVM_LD_LIBRARY_PATH:-"$JAVA_HOME/lib/server:$JAVA_HOME/lib/amd64/server"}}
+export LD_LIBRARY_PATH=${{LD_LIBRARY_PATH:+$LD_LIBRARY_PATH:}}$JVM_LD_LIBRARY_PATH
 
-    script_format_part = """
 source "$(rlocation {sanitizer_options})"
 exec "$(rlocation {driver})" \
     --agent_path="$(rlocation {agent})" \
@@ -136,6 +136,7 @@ exec "$(rlocation {driver})" \
         deploy_jar = runfile_path(ctx, ctx.file.target_deploy_jar),
         driver = runfile_path(ctx, driver),
         native_dirs = ":".join(native_dirs),
+        realpath = runfile_path(ctx, ctx.executable._realpath),
         sanitizer_options = runfile_path(ctx, ctx.file.sanitizer_options),
     )
     ctx.actions.write(script, script_content, is_executable = True)
@@ -232,6 +233,9 @@ def _jazzer_fuzz_binary_impl(ctx):
 
     runfiles = runfiles.merge(ctx.runfiles([ctx.file.sanitizer_options]))
 
+    runfiles = runfiles.merge(ctx.runfiles([ctx.executable._realpath]))
+    runfiles = runfiles.merge(ctx.attr._realpath[DefaultInfo].default_runfiles)
+
     script = _jazzer_fuzz_binary_script(ctx, native_libs, driver)
     return [DefaultInfo(executable = script, runfiles = runfiles)]
 
@@ -283,6 +287,12 @@ Rule that creates a binary that invokes Jazzer on the specified target.
             allow_single_file = [".jar"],
             mandatory = True,
         ),
+        "_realpath": attr.label(
+            doc = "The realpath util needed by the binary script.",
+            default = "//fuzzing/tools:realpath",
+            executable = True,
+            cfg = "target",
+        ),
         "_allowlist_function_transition": attr.label(
             default = "@bazel_tools//tools/allowlists/function_transition_allowlist",
         ),

fuzzing/tools/BUILD

@@ -36,6 +36,13 @@ py_binary(
     deps = [requirement("absl-py")],
 )
 
+py_binary(
+    name = "realpath",
+    srcs = ["realpath.py"],
+    python_version = "PY3",
+    visibility = ["//visibility:public"],
+)
+
 py_binary(
     name = "validate_dict",
     srcs = ["validate_dict.py"],

fuzzing/tools/realpath.py

@@ -0,0 +1,27 @@
+# Copyright 2020 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
+#
+#    https://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.
+
+# Lint as: python3
+"""
+Gets the realpath of a input path.
+
+This is a portable replacement of the `readlink -f/realpath`.
+"""
+
+import os, sys
+
+if len(sys.argv) < 2:
+    print("Need an argument for the input path.", file=sys.stderr)
+    sys.exit(1)
+print(os.path.realpath(sys.argv[1]))