Saint's Log

hsdis+binutils on macOS/Linux

A previous post explored how to use LLVM as the backend disassembler for hsdis. The instructions for how to use GNU binutils (the currently supported option) are straightforward. Listing them here for completeness (assuming you have cloned the OpenJDK repo into your ~/repos/java/jdk folder). Note that they depend on more recent changes. See the docs on the Java command for more info about the -XX:CompileCommand option.

# Download and extract GNU binutils 2.37
cd ~
curl -Lo binutils-2.37.tar.gz https://ftp.gnu.org/gnu/binutils/binutils-2.37.tar.gz
tar xvf binutils-2.37.tar.gz

# Configure the OpenJDK repo for hsdis
cd ~/repos/java/jdk
bash configure --with-hsdis=binutils --with-binutils-src=~/binutils-2.37

# Build hsdis
make build-hsdis

To deploy the built hsdis library on macOS:

cd build/macosx-aarch64-server-release

# Copy the hsdis library into the JDK bin folder
cp support/hsdis/libhsdis.dylib jdk/bin/hsdis-aarch64.dylib

To deploy the built hsdis library on Ubuntu Linux (open question: is this step even necessary?):

cd build/linux-x86_64-server-release

# Copy the hsdis library into the JDK bin folder
cp support/hsdis/libhsdis.so jdk/bin/

Update 2024-03-13: use the make install-hsdis command to copy the hsdis binaries into the new OpenJDK build. This will ensure that the hsdis binary is copied to lib/hsdis-adm64.so (this file name should be used in place of any others that listed by find . -name *hsdis*).

Now we can disassemble some code, e.g. the String.checkIndex method mentioned in PR 5920.

# Disassemble some code
jdk/bin/java -XX:CompileCommand="print java.lang.String::checkIndex" -version

To see how to disassemble the code for a class, we can use the basic substitution cipher class from the post on Building HSDIS in Cygwin as an example. Download, compile and disassemble it using the commands below. Note that these commands save the .java file to a temp folder to make cleanup much easier. Also note the redirection to a file since the output can be voluminous.

cd jdk/bin
mkdir -p temp
cd temp

curl -Lo BasicSubstitutionCipher.java https://raw.githubusercontent.com/swesonga/scratchpad/main/apps/crypto/substitution-cipher/BasicSubstitutionCipher.java

../javac BasicSubstitutionCipher.java

../java -XX:+UnlockDiagnosticVMOptions -XX:+PrintAssembly -XX:+LogCompilation BasicSubstitutionCipher > disassembled.txt

open disassembled.txt