A Java Library that allows inline ASM in Java Code.
Note:
- This ASM is not x86/ARM ASM, but JVM Instruction
- Only support Java 8
Add Maven repository:
<repositories>
<repository>
<id>jitpack.io</id>
<url>https://jitpack.io</url>
</repository>
</repositories>Get:
<dependency>
<groupId>com.github.4ra1n</groupId>
<artifactId>__asm__</artifactId>
<version>0.0.1</version>
</dependency>(1) Hello World:
import java.io.PrintStream;
import java.lang.invoke.MethodType;
import static org.sec.asm.core.ASM.__asm__;
public class TestHello {
public static void main(String[] args) {
System.out.println("test __asm__");
__asm__(asm -> asm.INIT()
.GETSTATIC(System.class, "out", PrintStream.class)
.LDC("hello world!")
.INVOKEVIRTUAL(PrintStream.class, "println",
MethodType.methodType(Void.TYPE, String.class)));
System.out.println("test end");
}
}You will see this output when first run:
|----------------ASM----------------|
| Please Restart Java Application |
|-----------------------------------|
And restart:
test __asm__
hello world!
test end
(2) Instantiate
public class TestArray {
public static void main(String[] args) {
int[] arr = null;
__asm__(asm -> asm.INIT()
.ICONST_3()
.NEWARRAY(T_INT)
.ASTORE(1)
.ALOAD(1)
.ICONST_0()
.ICONST_1()
.IASTORE());
System.out.println(arr[0]);
}
}Run twice and the console:
1
(3) How to solve return value
public class TestExec {
public static void main(String[] args) {
Runtime r = Runtime.getRuntime();
Process p = null;
__asm__(asm -> asm.INIT()
.ALOAD(1)
.LDC("open /System/Applications/Calculator.app")
.INVOKEVIRTUAL(Runtime.class, "exec",
MethodType.methodType(Process.class, String.class))
.ASTORE(2)
);
if (p != null) {
System.out.println("not null");
}
}
}Why should we use ASTORE 2 to solve return in the end:
Operand Stack after invoke:
┌──────────────────┐
│ Process Return │ TOP
├──────────────────┤
│ ... │
├──────────────────┤
│ ... │
├──────────────────┤
│ ... │
└──────────────────┘
Local Variables after invoke:
┌─────────────────┬──────────────┬────────────────────┬───────┐
│ 0 │ 1 │ 2 │ ... │
├─────────────────┼──────────────┼────────────────────┼───────┤
│ String[] args │ Runtime rt │ Process -> null │ ... │
└─────────────────┴──────────────┴────────────────────┴───────┘
We can use ASTORE 2 to save Process return ref to Process p ptr of local variables.
(4) Junk code:
public class TestExec {
public static void main(String[] args) {
Runtime r = Runtime.getRuntime();
Process p = null;
__asm__(asm -> asm.INIT()
.ALOAD(1)
.LDC("open /System/Applications/Calculator.app")
.INVOKEVIRTUAL(Runtime.class, "exec",
MethodType.methodType(Process.class, String.class))
.DUP()
.POP()
.ALOAD(0)
.ASTORE(3)
.ASTORE(2)
);
if (p != null) {
System.out.println("not null");
}
}
}We can add some junk code, but run normally. Have fun.
The core code is from: https://github.com/xxDark/asm-inline
Its code is a little hard to understand and cannot be run directly. So I simplify and refactor on the basis of this code, then make this project.
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