app_main.cpp revision d6183204e438a738b68301aeac452c0be41c8cb3 
1/*
2 * Main entry of app process.
3 *
4 * Starts the interpreted runtime, then starts up the application.
5 *
6 */
7
8#define LOG_TAG "appproc"
9
10#include <binder/IPCThreadState.h>
11#include <binder/ProcessState.h>
12#include <utils/Log.h>
13#include <cutils/memory.h>
14#include <cutils/process_name.h>
15#include <cutils/properties.h>
16#include <cutils/trace.h>
17#include <android_runtime/AndroidRuntime.h>
18#include <private/android_filesystem_config.h>  // for AID_SYSTEM
19
20#include <stdlib.h>
21#include <stdio.h>
22#include <unistd.h>
23#include <sys/prctl.h>
24
25namespace android {
26
27void app_usage()
28{
29    fprintf(stderr,
30        "Usage: app_process [java-options] cmd-dir start-class-name [options]\n");
31}
32
33class AppRuntime : public AndroidRuntime
34{
35public:
36    AppRuntime(char* argBlockStart, const size_t argBlockLength)
37        : AndroidRuntime(argBlockStart, argBlockLength)
38        , mClass(NULL)
39    {
40    }
41
42    void setClassNameAndArgs(const String8& className, int argc, char * const *argv) {
43        mClassName = className;
44        for (int i = 0; i < argc; ++i) {
45             mArgs.add(String8(argv[i]));
46        }
47    }
48
49    virtual void onVmCreated(JNIEnv* env)
50    {
51        if (mClassName.isEmpty()) {
52            return; // Zygote. Nothing to do here.
53        }
54
55        /*
56         * This is a little awkward because the JNI FindClass call uses the
57         * class loader associated with the native method we're executing in.
58         * If called in onStarted (from RuntimeInit.finishInit because we're
59         * launching "am", for example), FindClass would see that we're calling
60         * from a boot class' native method, and so wouldn't look for the class
61         * we're trying to look up in CLASSPATH. Unfortunately it needs to,
62         * because the "am" classes are not boot classes.
63         *
64         * The easiest fix is to call FindClass here, early on before we start
65         * executing boot class Java code and thereby deny ourselves access to
66         * non-boot classes.
67         */
68        char* slashClassName = toSlashClassName(mClassName.string());
69        mClass = env->FindClass(slashClassName);
70        if (mClass == NULL) {
71            ALOGE("ERROR: could not find class '%s'\n", mClassName.string());
72        }
73        free(slashClassName);
74
75        mClass = reinterpret_cast<jclass>(env->NewGlobalRef(mClass));
76    }
77
78    virtual void onStarted()
79    {
80        sp<ProcessState> proc = ProcessState::self();
81        ALOGV("App process: starting thread pool.\n");
82        proc->startThreadPool();
83
84        AndroidRuntime* ar = AndroidRuntime::getRuntime();
85        ar->callMain(mClassName, mClass, mArgs);
86
87        IPCThreadState::self()->stopProcess();
88    }
89
90    virtual void onZygoteInit()
91    {
92        // Re-enable tracing now that we're no longer in Zygote.
93        atrace_set_tracing_enabled(true);
94
95        sp<ProcessState> proc = ProcessState::self();
96        ALOGV("App process: starting thread pool.\n");
97        proc->startThreadPool();
98    }
99
100    virtual void onExit(int code)
101    {
102        if (mClassName.isEmpty()) {
103            // if zygote
104            IPCThreadState::self()->stopProcess();
105        }
106
107        AndroidRuntime::onExit(code);
108    }
109
110
111    String8 mClassName;
112    Vector<String8> mArgs;
113    jclass mClass;
114};
115
116}
117
118using namespace android;
119
120static size_t computeArgBlockSize(int argc, char* const argv[]) {
121    // TODO: This assumes that all arguments are allocated in
122    // contiguous memory. There isn't any documented guarantee
123    // that this is the case, but this is how the kernel does it
124    // (see fs/exec.c).
125    //
126    // Also note that this is a constant for "normal" android apps.
127    // Since they're forked from zygote, the size of their command line
128    // is the size of the zygote command line.
129    //
130    // We change the process name of the process by over-writing
131    // the start of the argument block (argv[0]) with the new name of
132    // the process, so we'd mysteriously start getting truncated process
133    // names if the zygote command line decreases in size.
134    uintptr_t start = reinterpret_cast<uintptr_t>(argv[0]);
135    uintptr_t end = reinterpret_cast<uintptr_t>(argv[argc - 1]);
136    end += strlen(argv[argc - 1]);
137
138    return (end - start);
139}
140
141static void maybeCreateDalvikCache() {
142#if defined(__aarch64__)
143    static const char kInstructionSet[] = "arm64";
144#elif defined(__x86_64__)
145    static const char kInstructionSet[] = "x86_64";
146#elif defined(__arm__)
147    static const char kInstructionSet[] = "arm";
148#elif defined(__i386__)
149    static const char kInstructionSet[] = "x86";
150#elif defined (__mips__)
151    static const char kInstructionSet[] = "mips";
152#else
153#error "Unknown instruction set"
154#endif
155    const char* androidRoot = getenv("ANDROID_DATA");
156    LOG_ALWAYS_FATAL_IF(androidRoot == NULL, "ANDROID_DATA environment variable unset");
157
158    char dalvikCacheDir[PATH_MAX];
159    const int numChars = snprintf(dalvikCacheDir, PATH_MAX,
160            "%s/dalvik-cache/%s", androidRoot, kInstructionSet);
161    LOG_ALWAYS_FATAL_IF((numChars >= PATH_MAX || numChars < 0),
162            "Error constructing dalvik cache : %s", strerror(errno));
163
164    int result = mkdir(dalvikCacheDir, 0771);
165    LOG_ALWAYS_FATAL_IF((result < 0 && errno != EEXIST),
166            "Error creating cache dir %s : %s", dalvikCacheDir, strerror(errno));
167
168    // We always perform these steps because the directory might
169    // already exist, with wider permissions and a different owner
170    // than we'd like.
171    result = chown(dalvikCacheDir, AID_SYSTEM, AID_SYSTEM);
172    LOG_ALWAYS_FATAL_IF((result < 0), "Error changing dalvik-cache ownership : %s", strerror(errno));
173
174    result = chmod(dalvikCacheDir, 0771);
175    LOG_ALWAYS_FATAL_IF((result < 0),
176            "Error changing dalvik-cache permissions : %s", strerror(errno));
177}
178
179#if defined(__LP64__)
180static const char ABI_LIST_PROPERTY[] = "ro.product.cpu.abilist64";
181static const char ZYGOTE_NICE_NAME[] = "zygote64";
182#else
183static const char ABI_LIST_PROPERTY[] = "ro.product.cpu.abilist32";
184static const char ZYGOTE_NICE_NAME[] = "zygote";
185#endif
186
187int main(int argc, char* const argv[])
188{
189    if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) < 0) {
190        // Older kernels don't understand PR_SET_NO_NEW_PRIVS and return
191        // EINVAL. Don't die on such kernels.
192        if (errno != EINVAL) {
193            LOG_ALWAYS_FATAL("PR_SET_NO_NEW_PRIVS failed: %s", strerror(errno));
194            return 12;
195        }
196    }
197
198    AppRuntime runtime(argv[0], computeArgBlockSize(argc, argv));
199    // Process command line arguments
200    // ignore argv[0]
201    argc--;
202    argv++;
203
204    // Everything up to '--' or first non '-' arg goes to the vm.
205    //
206    // The first argument after the VM args is the "parent dir", which
207    // is currently unused.
208    //
209    // After the parent dir, we expect one or more the following internal
210    // arguments :
211    //
212    // --zygote : Start in zygote mode
213    // --start-system-server : Start the system server.
214    // --application : Start in application (stand alone, non zygote) mode.
215    // --nice-name : The nice name for this process.
216    //
217    // For non zygote starts, these arguments will be followed by
218    // the main class name. All remaining arguments are passed to
219    // the main method of this class.
220    //
221    // For zygote starts, all remaining arguments are passed to the zygote.
222    // main function.
223
224
225    int i = runtime.addVmArguments(argc, argv);
226
227    // Parse runtime arguments.  Stop at first unrecognized option.
228    bool zygote = false;
229    bool startSystemServer = false;
230    bool application = false;
231    const char* niceName = NULL;
232    String8 className;
233
234    ++i;  // Skip unused "parent dir" argument.
235    while (i < argc) {
236        const char* arg = argv[i++];
237        if (strcmp(arg, "--zygote") == 0) {
238            zygote = true;
239            niceName = ZYGOTE_NICE_NAME;
240        } else if (strcmp(arg, "--start-system-server") == 0) {
241            startSystemServer = true;
242        } else if (strcmp(arg, "--application") == 0) {
243            application = true;
244        } else if (strncmp(arg, "--nice-name=", 12) == 0) {
245            niceName = arg + 12;
246        } else if (strncmp(arg, "--", 2) != 0) {
247            className.setTo(arg);
248            break;
249        } else {
250            --i;
251            break;
252        }
253    }
254
255    Vector<String8> args;
256    if (!className.isEmpty()) {
257        // We're not in zygote mode, the only argument we need to pass
258        // to RuntimeInit is the application argument.
259        //
260        // The Remainder of args get passed to startup class main(). Make
261        // copies of them before we overwrite them with the process name.
262        args.add(application ? String8("application") : String8("tool"));
263        runtime.setClassNameAndArgs(className, argc - i, argv + i);
264    } else {
265        // We're in zygote mode.
266        maybeCreateDalvikCache();
267
268        if (startSystemServer) {
269            args.add(String8("start-system-server"));
270        }
271
272        char prop[PROP_VALUE_MAX];
273        if (property_get(ABI_LIST_PROPERTY, prop, NULL) == 0) {
274            LOG_ALWAYS_FATAL("app_process: Unable to determine ABI list from property %s.",
275                ABI_LIST_PROPERTY);
276            return 11;
277        }
278
279        String8 abiFlag("--abi-list=");
280        abiFlag.append(prop);
281        args.add(abiFlag);
282
283        // In zygote mode, pass all remaining arguments to the zygote
284        // main() method.
285        for (; i < argc; ++i) {
286            args.add(String8(argv[i]));
287        }
288    }
289
290    if (niceName && *niceName) {
291        runtime.setArgv0(niceName);
292        set_process_name(niceName);
293    }
294
295    if (zygote) {
296        runtime.start("com.android.internal.os.ZygoteInit", args);
297    } else if (className) {
298        runtime.start("com.android.internal.os.RuntimeInit", args);
299    } else {
300        fprintf(stderr, "Error: no class name or --zygote supplied.\n");
301        app_usage();
302        LOG_ALWAYS_FATAL("app_process: no class name or --zygote supplied.");
303        return 10;
304    }
305}
306