allow running emulated java aarch64 tests
diff --git a/kokoro/linux/aarch64/protoc_crosscompile_aarch64.sh b/kokoro/linux/aarch64/protoc_crosscompile_aarch64.sh
new file mode 100755
index 0000000..77942a4
--- /dev/null
+++ b/kokoro/linux/aarch64/protoc_crosscompile_aarch64.sh
@@ -0,0 +1,9 @@
+#!/bin/bash
+#
+# Builds protobuf C++ with aarch64 crosscompiler.
+
+set -ex
+
+./autogen.sh
+CXXFLAGS="-fPIC -g -O2" ./configure --host=aarch64
+make -j8
diff --git a/kokoro/linux/aarch64/test_java_aarch64.sh b/kokoro/linux/aarch64/test_java_aarch64.sh
new file mode 100755
index 0000000..72f1c83
--- /dev/null
+++ b/kokoro/linux/aarch64/test_java_aarch64.sh
@@ -0,0 +1,32 @@
+#!/bin/bash
+
+set -ex
+
+# go to the repo root
+cd $(dirname $0)/../../..
+
+if [[ -t 0 ]]; then
+ DOCKER_TTY_ARGS="-it"
+else
+ # The input device on kokoro is not a TTY, so -it does not work.
+ DOCKER_TTY_ARGS=
+fi
+
+# crosscompile protoc as we will later need it for the java build.
+# we build it under the dockcross/manylinux2014-aarch64 image so that the resulting protoc binary is compatible
+# with a wide range of linux distros (including any docker images we will use later to build and test java)
+kokoro/linux/aarch64/dockcross_helpers/run_dockcross_manylinux2014_aarch64.sh kokoro/linux/aarch64/protoc_crosscompile_aarch64.sh
+
+# the command that will be used to build and test java under an emulator
+# * IsValidUtf8Test and DecodeUtf8Test tests are being skipped because that take very long under an emulator.
+TEST_JAVA_COMMAND="mvn --batch-mode -DskipTests install && mvn --batch-mode -Dtest='**/*Test, !**/*IsValidUtf8Test, !**/*DecodeUtf8Test' -DfailIfNoTests=false surefire:test"
+
+# use an actual aarch64 docker image (with a real aarch64 java and maven) to run build & test protobuf java under an emulator
+# * mount the protobuf root as /work to be able to access the crosscompiled files
+# * to avoid running the process inside docker as root (which can pollute the workspace with files owned by root), we force
+# running under current user's UID and GID. To be able to do that, we need to provide a home directory for the user
+# otherwise the UID would be homeless under the docker container and pip install wouldn't work. For simplicity,
+# we just run map the user's home to a throwaway temporary directory
+# * the JAVA_OPTS and MAVEN_CONFIG variables are being set mostly to silence warnings about non-existent home directory
+# and to avoid polluting the workspace.
+docker run $DOCKER_TTY_ARGS --rm --user "$(id -u):$(id -g)" -e "HOME=/home/fake-user" -e "JAVA_OPTS=-Duser.home=/home/fake-user" -e "MAVEN_CONFIG=/home/fake-user/.m2" -v "$(mktemp -d):/home/fake-user" -v "$(pwd)":/work -w /work arm64v8/maven:3.8-openjdk-11 bash -c "cd java && $TEST_JAVA_COMMAND"
