Add a linker relocation benchmark

The benchmark creates a set of DSOs that mimic the work involved in
loading the current version of libandroid_servers.so. The synthetic
benchmark has roughly the same number of libraries with roughly the same
relocations.

Currently, on a local aosp_walleye build that includes recent performance
improvements (including the Neon-based CL
I3983bca1dddc9241bb70290ad3651d895f046660), using the "performance"
governor, the benchmark reports these scores:

$ adb shell taskset 10 \
  /data/benchmarktest64/linker-reloc-bench/linker-reloc-bench \
  --benchmark_repetitions=20 --benchmark_display_aggregates_only=true
...
--------------------------------------------------------------------------------
Benchmark                                      Time             CPU   Iterations
--------------------------------------------------------------------------------
BM_linker_relocation/real_time_mean        70048 us          465 us           20
BM_linker_relocation/real_time_median      70091 us          466 us           20
BM_linker_relocation/real_time_stddev        329 us         8.29 us           20

$ adb shell taskset 10 \
  /data/benchmarktest/linker-reloc-bench/linker-reloc-bench \
  --benchmark_repetitions=20 --benchmark_display_aggregates_only=true
...
--------------------------------------------------------------------------------
Benchmark                                      Time             CPU   Iterations
--------------------------------------------------------------------------------
BM_linker_relocation/real_time_mean        83051 us          462 us           20
BM_linker_relocation/real_time_median      83069 us          464 us           20
BM_linker_relocation/real_time_stddev        184 us         8.91 us           20

Test: manual
Bug: none
Change-Id: I6dac66978f8666f95c76387093bda6be0151bfce
diff --git a/benchmarks/linker_relocation/gen_bench.sh b/benchmarks/linker_relocation/gen_bench.sh
new file mode 100755
index 0000000..9961972
--- /dev/null
+++ b/benchmarks/linker_relocation/gen_bench.sh
@@ -0,0 +1,83 @@
+#!/bin/bash -e
+#
+# Copyright (C) 2019 The Android Open Source Project
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+#  * Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+#  * Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in
+#    the documentation and/or other materials provided with the
+#    distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+# COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+# OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+# AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+# OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+# SUCH DAMAGE.
+
+top=$(cd $(dirname $0) && pwd)
+
+bid=6079926
+
+keep_tmp_dir=0
+skip_gen_bench=0
+for arg in "$@"; do
+  case "$arg" in
+    --keep-tmp-dir)
+      keep_tmp_dir=1
+      ;;
+    --skip-gen-bench)
+      skip_gen_bench=1
+      ;;
+    *)
+      echo "error: unrecognized option: $arg"
+      exit 1
+      ;;
+  esac
+done
+
+work_dir=$top/tmp
+mkdir -p $work_dir
+cd $work_dir
+
+archive=aosp_arm64-target_files-$bid.zip
+if [ ! -f $archive ]; then
+  /google/data/ro/projects/android/fetch_artifact --bid $bid --target aosp_arm64-userdebug $archive
+fi
+if [ -e SYSTEM ]; then
+  rm -rf SYSTEM
+fi
+
+echo 'Unzipping system files...'
+unzip -q $archive \
+  'SYSTEM/system_ext/apex/com.android.art.debug/*' \
+  'SYSTEM/system_ext/apex/com.android.runtime/*' \
+  'SYSTEM/lib64/*'
+
+echo 'Dumping relocations...'
+python3 -B $top/regen/dump_relocs.py \
+  -L $work_dir/SYSTEM/system_ext/apex/com.android.art.debug/lib64 \
+  -L $work_dir/SYSTEM/system_ext/apex/com.android.runtime/lib64/bionic \
+  -L $work_dir/SYSTEM/lib64 \
+  $work_dir/SYSTEM/lib64/libandroid_servers.so \
+  $work_dir/libandroid_servers_arm64.json
+
+if [ $skip_gen_bench -eq 0 ]; then
+  echo 'Generating benchmark...'
+  python3 -B $top/regen/gen_bench.py $work_dir/libandroid_servers_arm64.json $top/gen
+fi
+
+if [ $keep_tmp_dir -eq 0 ]; then
+  rm -rf $work_dir
+fi