fuzzing/fuzzer.gni

# Copyright 2018 The Fuchsia Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

import("//build/package.gni")

# Declare a fuzzed executable target.
#
# Creates an instrumented executable file for fuzzing with a sanitizer.  Do not
# use directly; instead, use `fuzz_target` with an associated `fuzz_package`
# specifying the supported sanitizers.
#
# Takes all the same parameters as executable().
template("_fuzzed_executable") {
  executable(target_name) {
    _target_type = "fuzzed_executable"

    # Explicitly forward visibility, implicitly forward everything else.
    # See comment in //build/config/BUILDCONFIG.gn for details on this pattern.
    forward_variables_from(invoker, [ "visibility" ])
    forward_variables_from(invoker,
                           "*",
                           [
                             "visibility",
                             "_target_type",
                           ])
  }
}

# Declares a resource needed by the fuzzer.
#
# Creates a (potentially empty) resource file for use by a `fuzz_target`.  Do
# not use directly; instead, use `fuzz_target` with an associated
# `fuzz_package` specifying the supported sanitizers.
#
# Parameters:
#
#   fuzz_name (required)
#      [string] Name of the associated `fuzz_target`.
#
#   resource (required)
#      [string] Base file name of the resource to produce.
#
#   script (optional)
#      [file] Script that produces the resources.  Defaults to
#      //build/fuzzing/gen_fuzzer_resource.py
#
#   args (optional)
#      [list of strings] Additional arguments to append to the script command
#      line.
#
template("_fuzz_resource") {
  assert(defined(invoker.fuzz_name),
         "`fuzz_name` must be defined for $target_name")
  assert(defined(invoker.resource),
         "`resource` must be defined for $target_name")
  action(target_name) {
    if (defined(invoker.script)) {
      script = invoker.script
    } else {
      script = "//build/fuzzing/gen_fuzzer_resource.py"
    }
    output = "${target_gen_dir}/${invoker.fuzz_name}/${invoker.resource}"
    outputs = [
      output,
    ]
    args = [
      "--out",
      rebase_path(output),
    ]
    if (defined(invoker.args)) {
      args += invoker.args
    }
  }
}

# Defines a fuzz target binary
#
# The fuzz_target template is used to create binaries which leverage LLVM's
# libFuzzer to perform fuzz testing.
#
# Parameters
#
#   options (optional)
#     [list of strings] Each option is of the form "key=value" and indicates
#     command line options that the fuzzer should be invoked with. Valid keys
#     are libFuzzer options (https://llvm.org/docs/LibFuzzer.html#options).
#
#   dictionary (optional)
#     [file] If specified, a file containing inputs, one per line, that the
#     fuzzer will use to generate new mutations.
#
#   corpora (optional)
#     [list of strings] One or more locations from which to get a fuzzing
#     corpus, e.g. a project path to a directory of artifacts, a project
#     path to a CIPD ensure file, or a GCS URL.
#
#   sources (optional)
#     [list of files] The C++ sources required to build the fuzzer binary. With
#     the exception of the "zircon_fuzzers" targets, this list must be present
#     and include a file defining `LLVMFuzzerTestOneInput`.  It will typically
#     be a single file (with deps including the software under test).
#
template("fuzz_target") {
  assert(defined(invoker.sources), "`sources` must be defined for $target_name")
  _fuzzed_executable(target_name) {
    forward_variables_from(invoker,
                           "*",
                           [
                             "corpora",
                             "dictionary",
                             "options",
                             "output_name",
                           ])
    testonly = true
  }

  # The following rules ensure the fuzzer resources are present (even if empty)
  # and in known locations.  This is needed as the fuzz_package has no way of
  # knowing the original file names when building the package manifest.  These
  # files only need to be written once, so only do it in the base toolchain.
  if (current_toolchain == toolchain_variant.base) {
    fuzz_name = target_name

    # Copy the corpora available for the fuzzer
    _fuzz_resource("${fuzz_name}_corpora") {
      resource = "corpora"
      if (defined(invoker.corpora)) {
        args = invoker.corpora
      }
    }

    # Copy the fuzzer dictionary
    _fuzz_resource("${fuzz_name}_dictionary") {
      resource = "dictionary"
      if (defined(invoker.dictionary)) {
        args = read_file(invoker.dictionary, "list lines")
      }
    }

    # Copy the options the fuzzer should be invoked with
    _fuzz_resource("${fuzz_name}_options") {
      resource = "options"
      if (defined(invoker.options)) {
        args = invoker.options
      }
    }

    # Create a component manifest
    _fuzz_resource("${fuzz_name}_cmx") {
      script = "//build/fuzzing/gen_fuzzer_manifest.py"
      resource = "${fuzz_name}.cmx"
      args = [
        "--bin",
        "${fuzz_name}",
      ]
      if (defined(invoker.cmx)) {
        args += [
          "--cmx",
          rebase_path(invoker.cmx),
        ]
      }
    }
  } else {
    not_needed(invoker, "*")
  }
}

set_defaults("fuzz_target") {
  configs = default_executable_configs +
            [ "//build/fuzzing:fuzzing_build_mode_unsafe_for_production" ]
}

# Defines a package of fuzz target binaries
#
# The fuzz_package template is used to bundle several fuzz_targets and their
# associated data into a single Fuchsia package.
#
# Parameters
#
#   targets (required)
#     [list of labels] The fuzz_target() targets to include in this package.
#
#   sanitizers (required)
#     [list of variants] A set of sanitizer variants.  The resulting package
#     will contain binaries for each sanitizer/target combination.
#
#   binaries (optional)
#   data_deps (optional)
#   deps (optional)
#   public_deps (optional)
#   extra (optional)
#   loadable_modules (optional)
#   meta (optional)
#   resources (optional)
#     Passed through to the normal package template.
#
#   fuzz_host (optional)
#     [boolean] Indicates whether to also build fuzzer binaries on host.
#     Defaults to false.
#
#   omit_binaries (optional)
#     [bool] If true, indicates the fuzz target binaries will be provided by
#     a non-GN build, e.g. the Zircon build.  The package will contain the
#     resources needed by the fuzzer, but no binaries or component manifests.
#     Defaults to false.
#
template("fuzz_package") {
  assert(defined(invoker.targets), "targets must be defined for $target_name}")
  assert(defined(invoker.sanitizers),
         "sanitizers must be defined for $target_name")

  # Only assemble the package once; handle the specific sanitizers in the loop below
  if (current_toolchain == toolchain_variant.base) {
    fuzz = {
      binaries = []
      deps = []
      resources = []
      meta = []
      host = false
      host_binaries = []
      omit_binaries = false
      forward_variables_from(invoker,
                             [
                               "binaries",
                               "data_deps",
                               "deps",
                               "public_deps",
                               "extra",
                               "loadable_modules",
                               "meta",
                               "resources",
                               "targets",
                               "sanitizers",
                             ])
    }
    if (defined(invoker.fuzz_host)) {
      fuzz.host = invoker.fuzz_host
    }
    if (defined(invoker.omit_binaries)) {
      fuzz.omit_binaries = invoker.omit_binaries
    }

    # It's possible (although unusual) that targets could be empty, e.g. a placeholder package
    if (fuzz.targets == []) {
      not_needed(fuzz, [ "sanitizers" ])
    }

    foreach(fuzz_target, fuzz.targets) {
      fuzz_name = get_label_info(fuzz_target, "name")

      # Find the executable variant for the sanitized fuzzer
      selected = false
      sanitized_target = ""
      host_target = ""
      foreach(sanitizer, fuzz.sanitizers) {
        if (!selected) {
          foreach(selector, select_variant_canonical) {
            if (selector.variant == "${sanitizer}-fuzzer") {
              if (defined(selector.target_type)) {
                selector_target_type = []
                selector_target_type = selector.target_type
                if (selector_target_type[0] == "fuzzed_executable") {
                  selected = true
                }
              }
              if (defined(selector.name)) {
                selector_name = []
                selector_name = selector.name
                if (selector_name[0] == fuzz_name) {
                  selected = true
                }
              }
              if (defined(selector.output_name)) {
                selector_output_name = []
                selector_output_name = selector.output_name
                if (selector_output_name[0] == fuzz_name) {
                  selected = true
                }
              }
              if (selected) {
                sanitized_target = "${fuzz_target}(${toolchain_variant.base}-${sanitizer}-fuzzer)"
                host_target =
                    "${fuzz_target}(${host_toolchain}-${sanitizer}-fuzzer)"
              }
            }
          }
        }
      }

      # If enabled, add fuzz target to package
      if (sanitized_target != "") {
        fuzz_label = get_label_info(sanitized_target, "label_no_toolchain")
        fuzz_gen_dir =
            get_label_info(fuzz_target, "target_gen_dir") + "/${fuzz_name}"

        if (!fuzz.omit_binaries) {
          fuzz.deps += [ sanitized_target ]
          fuzz_out_dir = get_label_info(sanitized_target, "root_out_dir")
          fuzz.binaries += [
            {
              name = fuzz_name
              source = "${fuzz_out_dir}/${fuzz_name}"
              dest = fuzz_name
            },
          ]

          fuzz.deps += [ "${fuzz_label}_cmx(${toolchain_variant.base})" ]
          fuzz.meta += [
            {
              path = "${fuzz_gen_dir}/${fuzz_name}.cmx"
              dest = "${fuzz_name}.cmx"
            },
          ]

          fuzz.host_binaries += [ "$host_target" ]
        }

        fuzz.deps += [
          "${fuzz_label}_corpora(${toolchain_variant.base})",
          "${fuzz_label}_dictionary(${toolchain_variant.base})",
          "${fuzz_label}_options(${toolchain_variant.base})",
        ]
        fuzz.resources += [
          {
            path = "${fuzz_gen_dir}/corpora"
            dest = "${fuzz_name}/corpora"
          },
          {
            path = "${fuzz_gen_dir}/dictionary"
            dest = "${fuzz_name}/dictionary"
          },
          {
            path = "${fuzz_gen_dir}/options"
            dest = "${fuzz_name}/options"
          },
        ]
      } else {
        not_needed([
                     "fuzz_name",
                     "host_target",
                   ])
        not_needed(fuzz, "*")
      }
    }

    group("host_${target_name}") {
      testonly = true
      if (fuzz.host) {
        deps = fuzz.host_binaries
      }
    }

    # Build the actual package
    package(target_name) {
      testonly = true
      forward_variables_from(fuzz,
                             "*",
                             [
                               "targets",
                               "sanitizers",
                               "host",
                               "host_binaries",
                               "omit_binaries",
                             ])
    }
  } else {
    not_needed(invoker, "*")
  }
}