【Android学习】一代壳实现与脱壳研究

5    public DexPathList(ClassLoader definingContext, String dexPath,
86            String libraryPath, File optimizedDirectory) {
87        if (definingContext == null) {
88            throw new NullPointerException("definingContext == null");
89        }
90
91        if (dexPath == null) {
92            throw new NullPointerException("dexPath == null");
93        }
94
95        if (optimizedDirectory != null) {
96            if (!optimizedDirectory.exists())  {
97                throw new IllegalArgumentException(
98                        "optimizedDirectory doesn't exist: "
99                        + optimizedDirectory);
100            }
101
102            if (!(optimizedDirectory.canRead()
103                            && optimizedDirectory.canWrite())) {
104                throw new IllegalArgumentException(
105                        "optimizedDirectory not readable/writable: "
106                        + optimizedDirectory);
107            }
108        }
109
110        this.definingContext = definingContext;
111        ArrayList<IOException> suppressedExceptions = new ArrayList<IOException>();
112        this.dexElements = makeDexElements(splitDexPath(dexPath), optimizedDirectory,
113                                           suppressedExceptions);
114        if (suppressedExceptions.size() > 0) {
115            this.dexElementsSuppressedExceptions =
116                suppressedExceptions.toArray(new IOException[suppressedExceptions.size()]);
117        } else {
118            dexElementsSuppressedExceptions = null;
119        }
120        this.nativeLibraryDirectories = splitLibraryPath(libraryPath);
121    }
122

static void Dalvik_dalvik_system_DexFile_openDexFileNative(const u4* args,
152    JValue* pResult)
153{
154    StringObject* sourceNameObj = (StringObject*) args[0];
155    StringObject* outputNameObj = (StringObject*) args[1];
156    DexOrJar* pDexOrJar = NULL;
157    JarFile* pJarFile;
158    RawDexFile* pRawDexFile;
159    char* sourceName;
160    char* outputName;
161
162    if (sourceNameObj == NULL) {
163        dvmThrowNullPointerException("sourceName == null");
164        RETURN_VOID();
165    }
166
167    sourceName = dvmCreateCstrFromString(sourceNameObj);
168    if (outputNameObj != NULL)
169        outputName = dvmCreateCstrFromString(outputNameObj);
170    else
171        outputName = NULL;
172
173    /*
174     * We have to deal with the possibility that somebody might try to
175     * open one of our bootstrap class DEX files.  The set of dependencies
176     * will be different, and hence the results of optimization might be
177     * different, which means we'd actually need to have two versions of
178     * the optimized DEX: one that only knows about part of the boot class
179     * path, and one that knows about everything in it.  The latter might
180     * optimize field/method accesses based on a class that appeared later
181     * in the class path.
182     *
183     * We can't let the user-defined class loader open it and start using
184     * the classes, since the optimized form of the code skips some of
185     * the method and field resolution that we would ordinarily do, and
186     * we'd have the wrong semantics.
187     *
188     * We have to reject attempts to manually open a DEX file from the boot
189     * class path.  The easiest way to do this is by filename, which works
190     * out because variations in name (e.g. "/system/framework/./ext.jar")
191     * result in us hitting a different dalvik-cache entry.  It's also fine
192     * if the caller specifies their own output file.
193     */
194    if (dvmClassPathContains(gDvm.bootClassPath, sourceName)) {
195        ALOGW("Refusing to reopen boot DEX '%s'", sourceName);
196        dvmThrowIOException(
197            "Re-opening BOOTCLASSPATH DEX files is not allowed");
198        free(sourceName);
199        free(outputName);
200        RETURN_VOID();
201    }
202
203    /*
204     * Try to open it directly as a DEX if the name ends with ".dex".
205     * If that fails (or isn't tried in the first place), try it as a
206     * Zip with a "classes.dex" inside.
207     */
208    if (hasDexExtension(sourceName)
209            && dvmRawDexFileOpen(sourceName, outputName, &pRawDexFile, false) == 0) {
210        ALOGV("Opening DEX file '%s' (DEX)", sourceName);
211
212        pDexOrJar = (DexOrJar*) malloc(sizeof(DexOrJar));
213        pDexOrJar->isDex = true;
214        pDexOrJar->pRawDexFile = pRawDexFile;
215        pDexOrJar->pDexMemory = NULL;
216    } else if (dvmJarFileOpen(sourceName, outputName, &pJarFile, false) == 0) {
217        ALOGV("Opening DEX file '%s' (Jar)", sourceName);
218
219        pDexOrJar = (DexOrJar*) malloc(sizeof(DexOrJar));
220        pDexOrJar->isDex = false;
221        pDexOrJar->pJarFile = pJarFile;
222        pDexOrJar->pDexMemory = NULL;
223    } else {
224        ALOGV("Unable to open DEX file '%s'", sourceName);
225        dvmThrowIOException("unable to open DEX file");
226    }
227
228    if (pDexOrJar != NULL) {
229        pDexOrJar->fileName = sourceName;
230        addToDexFileTable(pDexOrJar);
231    } else {
232        free(sourceName);
233    }
234
235    free(outputName);
236    RETURN_PTR(pDexOrJar);
237}

一种是inmemorydexclassloader
一种是禁用掉dex2oat之后用dexclassloader