Add tflite_ios_static_framework rule for hiding symbols

Exposed C++ symbols might cause collisions with other libraries.

PiperOrigin-RevId: 316853905
Change-Id: Ib7fd3f14fa40bc5c3e2ece0bf244cfb6e0623770

tensorflow/lite/experimental/ios/BUILD.apple

@@ -1,7 +1,7 @@
 # TensorFlow Lite for iOS
 
 load("@bazel_skylib//rules:build_test.bzl", "build_test")
-load("//tensorflow/lite/experimental/ios:ios.bzl", "TFL_MINIMUM_OS_VERSION")
+load("//tensorflow/lite/experimental/ios:ios.bzl", "TFL_MINIMUM_OS_VERSION", "tflite_ios_static_framework")
 load("@build_bazel_rules_apple//apple:ios.bzl", "ios_static_framework")
 
 package(
@@ -11,8 +11,15 @@ package(
     licenses = ["notice"],  # Apache 2.0
 )
 
+sh_binary(
+    name = "hide_symbols_with_whitelist",
+    srcs = [
+        "hide_symbols_with_whitelist.sh",
+    ],
+)
+
 # bazel build -c opt --config=ios_fat //tensorflow/lite/experimental/ios:TensorFlowLiteC_framework
-ios_static_framework(
+tflite_ios_static_framework(
     name = "TensorFlowLiteC_framework",
     hdrs = [
         "//tensorflow/lite/c:c_api.h",
@@ -20,6 +27,7 @@ ios_static_framework(
     ],
     bundle_name = "TensorFlowLiteC",
     minimum_os_version = TFL_MINIMUM_OS_VERSION,
+    whitelist_symbols_file = ":whitelist_TensorFlowLiteC.txt",
     deps = [
         ":tensorflow_lite_c",
     ],
@@ -60,16 +68,14 @@ genrule(
 # TensorFlowLiteC framework above in a composable way.
 #
 # bazel build -c opt --config=ios_fat //tensorflow/lite/experimental/ios:TensorFlowLiteCCoreMl_framework
-ios_static_framework(
+tflite_ios_static_framework(
     name = "TensorFlowLiteCCoreML_framework",
     hdrs = [
         ":coreml_delegate.h",
     ],
-    avoid_deps = [
-        ":tensorflow_lite_c",
-    ],
     bundle_name = "TensorFlowLiteCCoreML",
     minimum_os_version = TFL_MINIMUM_OS_VERSION,
+    whitelist_symbols_file = ":whitelist_TensorFlowLiteCCoreML.txt",
     deps = [
         "//tensorflow/lite/experimental/delegates/coreml:coreml_delegate",
     ],
@@ -81,16 +87,14 @@ ios_static_framework(
 # TensorFlowLiteC framework above in a composable way.
 #
 # bazel build -c opt --config=ios_fat //tensorflow/lite/experimental/ios:TensorFlowLiteCMetal_framework
-ios_static_framework(
+tflite_ios_static_framework(
     name = "TensorFlowLiteCMetal_framework",
     hdrs = [
         "//tensorflow/lite/delegates/gpu:metal_delegate.h",
     ],
-    avoid_deps = [
-        ":tensorflow_lite_c",
-    ],
     bundle_name = "TensorFlowLiteCMetal",
     minimum_os_version = TFL_MINIMUM_OS_VERSION,
+    whitelist_symbols_file = ":whitelist_TensorFlowLiteCMetal.txt",
     deps = [
         "//tensorflow/lite/delegates/gpu:metal_delegate",
     ],

tensorflow/lite/experimental/ios/hide_symbols_with_whitelist.sh

@@ -0,0 +1,135 @@
+#!/bin/bash
+# Copyright 2020 The TensorFlow Authors. All Rights Reserved.
+#
+# 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.
+# ==============================================================================
+#
+# A script to merge Mach-O object files into a single object file and hide
+# their internal symbols. Only whitelisted symbols will be visible in the
+# symbol table after this script.
+
+# To run this script, you must set several variables:
+#   INPUT_FRAMEWORK: a zip file containing the iOS static framework.
+#   BUNDLE_NAME: the pod/bundle name of the iOS static framework.
+#   WHITELIST_FILE_PATH: contains the whitelisted symbols.
+#   OUTPUT: the output zip file.
+
+# Halt on any error or any unknown variable.
+set -ue
+
+LD_DEBUGGABLE_FLAGS="-x"
+# Uncomment the below to get debuggable output. This can only be done for one
+# library at a time.
+# LD_DEBUGGABLE_FLAGS="-d"
+
+# Exits if C++ symbols are found in the whitelist list.
+if grep -q "^__Z" "${WHITELIST_FILE_PATH}"
+then
+  echo "ERROR: Failed in symbol hiding. This rule does not permit hiding of" \
+       "C++ symbols due to possible serious problems mixing symbol hiding," \
+       "shared libraries and the C++ runtime." \
+       "More info can be found in go/ios-symbols-hiding." \
+       "Please recheck the whitelist list and remove C++ symbols:"
+  echo "$(grep "^__Z" "${WHITELIST_FILE_PATH}")"
+  exit 1 # terminate and indicate error
+fi
+# Unzips the framework zip file into a temp workspace.
+framework=$(mktemp -t framework -d)
+unzip "${INPUT_FRAMEWORK}" -d "${framework}"/
+
+# Executable file in the framework.
+executable_file="${BUNDLE_NAME}.framework/${BUNDLE_NAME}"
+
+# Extracts architectures from the framework binary.
+archs_str=$(xcrun lipo -info "${framework}/${executable_file}" |
+sed -En -e 's/^(Non-|Architectures in the )fat file: .+( is architecture| are): (.*)$/\3/p')
+
+IFS=' ' read -r -a archs <<< "${archs_str}"
+
+merge_cmd=(xcrun lipo)
+
+# Merges object files and hide symbols for each architecture.
+for arch in "${archs[@]}"
+do
+    archdir=$(mktemp -t "${arch}" -d)
+    arch_file="${archdir}/${arch}"
+
+    # Handles the binary differently if they are fat or thin.
+    if [[ "${#archs[@]}" -gt 1 ]]; then
+       xcrun lipo "${framework}/${executable_file}" -thin "${arch}" -output "${arch_file}"
+    else
+       mv "${framework}/${executable_file}" "${arch_file}"
+    fi
+    if [[ "$arch" == "armv7" ]]; then
+      # Check that there are no thread local variables in the input, as they get broken.
+      # See b/124533863.
+      thread_locals=$(xcrun nm -m -g "${arch_file}" | awk '/__DATA,__thread_vars/ { print $5 }' | c++filt)
+      if [[ -n "${thread_locals}" ]]; then
+         echo
+         echo "WARNING: This symbol hiding script breaks thread local variables on 32-bit arm, you had:"
+         echo "${thread_locals}"
+         echo
+         echo "Your build will crash if these variables are actually used at runtime."
+         echo
+      fi
+    fi
+    xcrun ar -x "${arch_file}"
+    mv *.o "${archdir}"/
+
+    objects_file_list=$(mktemp)
+    # Hides the symbols except the whitelisted ones.
+    find "${archdir}" -name "*.o" >> "${objects_file_list}"
+
+    # Checks whether bitcode is enabled in the framework.
+    all_objects_have_bitcode=true
+    for object_file in $(cat "$objects_file_list"); do
+      if otool -arch "${arch}" -l "${object_file}" | grep -q __LLVM; then
+        : # Do nothing
+      else
+        echo "The ${arch} in ${object_file} is NOT bitcode-enabled."
+        all_objects_have_bitcode=false
+        break
+      fi
+    done
+    if [[ "$all_objects_have_bitcode" = "true" ]]; then
+      echo "The ${arch} in ${executable_file} is fully bitcode-enabled."
+      xcrun ld -r -bitcode_bundle -exported_symbols_list \
+        "${WHITELIST_FILE_PATH}" \
+        $LD_DEBUGGABLE_FLAGS \
+        -filelist "${objects_file_list}" -o "${arch_file}_processed.o"
+    else
+      echo "The ${arch} in ${executable_file} is NOT fully bitcode-enabled."
+      xcrun ld -r -exported_symbols_list \
+        "${WHITELIST_FILE_PATH}" \
+        $LD_DEBUGGABLE_FLAGS \
+        -filelist "${objects_file_list}" -o "${arch_file}_processed.o"
+    fi
+
+    output_object="${framework}/${arch}"
+
+    mv "${arch_file}_processed.o" "${output_object}"
+    rm -rf "${archdir}"
+    rm "${objects_file_list}"
+    merge_cmd+=(-arch "${arch}" "${output_object}")
+done
+
+# Repackages the processed object files.
+unzip "${INPUT_FRAMEWORK}"
+merge_cmd+=(-create -output "${BUNDLE_NAME}")
+"${merge_cmd[@]}"
+
+chmod +x "${BUNDLE_NAME}"
+rm "${executable_file}"
+mv "${BUNDLE_NAME}" "${executable_file}"
+( TZ=UTC find "${BUNDLE_NAME}.framework/" -exec touch -h -t 198001010000 {} \+ )
+zip --compression-method store --symlinks --recurse-paths --quiet "${OUTPUT}" "${BUNDLE_NAME}.framework/"

tensorflow/lite/experimental/ios/ios.bzl

@@ -1,5 +1,8 @@
 """TensorFlow Lite Build Configurations for iOS"""
 
+# Placeholder for Google-internal load statements.
+load("@build_bazel_rules_apple//apple:ios.bzl", "ios_static_framework")
+
 TFL_MINIMUM_OS_VERSION = "9.0"
 
 # Default tags for filtering iOS targets. Targets are restricted to Apple platforms.
@@ -13,3 +16,58 @@ TFL_DISABLED_SANITIZER_TAGS = [
     "nomsan",
     "notsan",
 ]
+
+# iOS static framework with symbol whitelist. Exported C++ symbbols might cause
+# symbol collision with other libraries. List of symbols to whitelist can be
+# generated by running `nm -m -g FRAMEWORK_LIBRARY | grep _TfLite` for framework
+# built with `ios_static_framework` rule.
+def tflite_ios_static_framework(
+        name,
+        bundle_name,
+        whitelist_symbols_file,
+        exclude_resources = True,
+        **kwargs):
+    """TFLite variant of ios_static_framework with symbol hiding.
+
+    Args:
+      name: The name of the target.
+      bundle_name: The name to give to the framework bundle, without the
+          ".framework" extension. If omitted, the target's name will be used.
+      whitelist_symbols_file: a file including a list of whitelisted symbols,
+          one symbol per line.
+      exclude_resources: Indicates whether resources should be excluded from the
+          bundle. This can be used to avoid unnecessarily bundling resources if
+          the static framework is being distributed in a different fashion, such
+          as a Cocoapod.
+      **kwargs: Pass-through arguments.
+    """
+
+    preprocessed_name = "Preprocessed_" + name
+    ios_static_framework(
+        name = preprocessed_name,
+        bundle_name = bundle_name,
+        exclude_resources = exclude_resources,
+        **kwargs
+    )
+
+    framework_target = ":{}.zip".format(preprocessed_name)
+
+    srcs = [
+        framework_target,
+        whitelist_symbols_file,
+    ]
+    cmd = ("INPUT_FRAMEWORK=\"$(location " + framework_target + ")\" " +
+           "BUNDLE_NAME=\"" + bundle_name + "\" " +
+           "WHITELIST_FILE_PATH=\"$(location " + whitelist_symbols_file + ")\" " +
+           "OUTPUT=\"$(OUTS)\" " +
+           "\"$(location //tensorflow/lite/experimental/ios:hide_symbols_with_whitelist)\"")
+
+    native.genrule(
+        name = name,
+        srcs = srcs,
+        outs = [name + ".zip"],
+        cmd = cmd,
+        tools = [
+            "//tensorflow/lite/experimental/ios:hide_symbols_with_whitelist",
+        ],
+    )

tensorflow/lite/experimental/ios/whitelist_TensorFlowLiteC.txt

@@ -0,0 +1 @@
+_TfLite*

tensorflow/lite/experimental/ios/whitelist_TensorFlowLiteCCoreML.txt

@@ -0,0 +1,2 @@
+_TfLiteCoreMlDelegateCreate
+_TfLiteCoreMlDelegateDelete

tensorflow/lite/experimental/ios/whitelist_TensorFlowLiteCMetal.txt

@@ -0,0 +1,2 @@
+_TFLGpuDelegateCreate
+_TFLGpuDelegateDelete