[Android] smali code 디버깅 방법

apk파일을 디컴파일하여 나온 smali code를 분석하다 보면 변수값이나 코드 흐름등을 파악하기 위해 로그를 넣고 싶은 경우가 있습니다.

 

검색을 해 보니 이런경우에 사용할 수 있는 좋은 내용인듯 하여 스크립 해 놓습니다.

How to debug smali code of an android application?

1. Debug log in smali

Debug log in smali. Say for example inside method test() you want to print "Inside Test()" debug log. At the start of method in smali add following instructions :

 

sget-object v0, Ljava/lang/System;->out:Ljava/io/PrintStream; 
const-string v1, "Inside Test()" 
invoke-virtual {v0, v1}, Ljava/io/PrintStream;->println(Ljava/lang/String;)V

 

Note - You need to be careful while using registers v0,v1 here. In code execution flow, you have to check that you are not using one of the register which is used later in the flow. Or you may get Exception.

 

2. StackTrace

Here is the code of smali to print stacktrace of a method

 

Java code

public static void printStackTraces() {
    StackTraceElement[] stackTraceElements = Thread.currentThread().getStackTrace(); 
    for (StackTraceElement element : stackTraceElements) {
        System.out.println("Class name :: " + element.getClassName() + "  || method name :: " + element.getMethodName());
    }
}

 

And equivalent smali code is

.method public static printStackTraces()V
    .locals 7

    .prologue
    .line 74
    invoke-static {}, Ljava/lang/Thread;->currentThread()Ljava/lang/Thread;
    move-result-object v2
    invoke-virtual {v2}, Ljava/lang/Thread;->getStackTrace()[Ljava/lang/StackTraceElement;
    move-result-object v1

    .line 75
    .local v1, stackTraceElements:[Ljava/lang/StackTraceElement;
    array-length v3, v1

    const/4 v2, 0x0

    :goto_0
    if-lt v2, v3, :cond_0

    .line 78
    return-void

    .line 75
    :cond_0
    aget-object v0, v1, v2

    .line 76
    .local v0, element:Ljava/lang/StackTraceElement;
    sget-object v4, Ljava/lang/System;->out:Ljava/io/PrintStream;
    new-instance v5, Ljava/lang/StringBuilder;
    const-string v6, "Class name :: " 
    invoke-direct {v5, v6}, Ljava/lang/StringBuilder;-><init>(Ljava/lang/String;)V
    invoke-virtual {v0}, Ljava/lang/StackTraceElement;->getClassName()Ljava/lang/String;
    move-result-object v6
    invoke-virtual {v5, v6}, Ljava/lang/StringBuilder;->append(Ljava/lang/String;)Ljava/lang/StringBuilder;

    move-result-object v5
    const-string v6, "  || method name :: " 
    invoke-virtual {v5, v6}, Ljava/lang/StringBuilder;->append(Ljava/lang/String;)Ljava/lang/StringBuilder;

    move-result-object v5
    invoke-virtual {v0}, Ljava/lang/StackTraceElement;->getMethodName()Ljava/lang/String;
    move-result-object v6
    invoke-virtual {v5, v6}, Ljava/lang/StringBuilder;->append(Ljava/lang/String;)Ljava/lang/StringBuilder;

    move-result-object v5
    invoke-virtual {v5}, Ljava/lang/StringBuilder;->toString()Ljava/lang/String;

    move-result-object v5
    invoke-virtual {v4, v5}, Ljava/io/PrintStream;->println(Ljava/lang/String;)V

    .line 75
    add-int/lit8 v2, v2, 0x1

    goto :goto_0
.end method

 

Add this method into any smali file. And call as

(Assuming you added above smali code into com.example.pakagename.ClassName)

invoke-static {}, Lcom/example/packagename/ClassName;->printStackTraces()V

 

Hope this helps .....

shareimprove this answer

answered Jan 2 '14 at 10:01 rajan goswami 34124