app_main.cpp revision 5638991c8233139ecf6207b99851116e2d2c2714 
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 <stdio.h>
11#include <stdlib.h>
12#include <sys/prctl.h>
13#include <sys/stat.h>
14#include <unistd.h>
15
16#include <binder/IPCThreadState.h>
17#include <binder/ProcessState.h>
18#include <utils/Log.h>
19#include <cutils/memory.h>
20#include <cutils/properties.h>
21#include <cutils/trace.h>
22#include <android_runtime/AndroidRuntime.h>
23#include <private/android_filesystem_config.h>  // for AID_SYSTEM
24
25namespace android {
26
27static void 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        sp<ProcessState> proc = ProcessState::self();
93        ALOGV("App process: starting thread pool.\n");
94        proc->startThreadPool();
95    }
96
97    virtual void onExit(int code)
98    {
99        if (mClassName.isEmpty()) {
100            // if zygote
101            IPCThreadState::self()->stopProcess();
102        }
103
104        AndroidRuntime::onExit(code);
105    }
106
107
108    String8 mClassName;
109    Vector<String8> mArgs;
110    jclass mClass;
111};
112
113}
114
115using namespace android;
116
117static size_t computeArgBlockSize(int argc, char* const argv[]) {
118    // TODO: This assumes that all arguments are allocated in
119    // contiguous memory. There isn't any documented guarantee
120    // that this is the case, but this is how the kernel does it
121    // (see fs/exec.c).
122    //
123    // Also note that this is a constant for "normal" android apps.
124    // Since they're forked from zygote, the size of their command line
125    // is the size of the zygote command line.
126    //
127    // We change the process name of the process by over-writing
128    // the start of the argument block (argv[0]) with the new name of
129    // the process, so we'd mysteriously start getting truncated process
130    // names if the zygote command line decreases in size.
131    uintptr_t start = reinterpret_cast<uintptr_t>(argv[0]);
132    uintptr_t end = reinterpret_cast<uintptr_t>(argv[argc - 1]);
133    end += strlen(argv[argc - 1]) + 1;
134    return (end - start);
135}
136
137static void maybeCreateDalvikCache() {
138#if defined(__aarch64__)
139    static const char kInstructionSet[] = "arm64";
140#elif defined(__x86_64__)
141    static const char kInstructionSet[] = "x86_64";
142#elif defined(__arm__)
143    static const char kInstructionSet[] = "arm";
144#elif defined(__i386__)
145    static const char kInstructionSet[] = "x86";
146#elif defined (__mips__) && !defined(__LP64__)
147    static const char kInstructionSet[] = "mips";
148#elif defined (__mips__) && defined(__LP64__)
149    static const char kInstructionSet[] = "mips64";
150#else
151#error "Unknown instruction set"
152#endif
153    const char* androidRoot = getenv("ANDROID_DATA");
154    LOG_ALWAYS_FATAL_IF(androidRoot == NULL, "ANDROID_DATA environment variable unset");
155
156    char dalvikCacheDir[PATH_MAX];
157    const int numChars = snprintf(dalvikCacheDir, PATH_MAX,
158            "%s/dalvik-cache/%s", androidRoot, kInstructionSet);
159    LOG_ALWAYS_FATAL_IF((numChars >= PATH_MAX || numChars < 0),
160            "Error constructing dalvik cache : %s", strerror(errno));
161
162    int result = mkdir(dalvikCacheDir, 0711);
163    LOG_ALWAYS_FATAL_IF((result < 0 && errno != EEXIST),
164            "Error creating cache dir %s : %s", dalvikCacheDir, strerror(errno));
165
166    // We always perform these steps because the directory might
167    // already exist, with wider permissions and a different owner
168    // than we'd like.
169    result = chown(dalvikCacheDir, AID_ROOT, AID_ROOT);
170    LOG_ALWAYS_FATAL_IF((result < 0), "Error changing dalvik-cache ownership : %s", strerror(errno));
171
172    result = chmod(dalvikCacheDir, 0711);
173    LOG_ALWAYS_FATAL_IF((result < 0),
174            "Error changing dalvik-cache permissions : %s", strerror(errno));
175}
176
177#if defined(__LP64__)
178static const char ABI_LIST_PROPERTY[] = "ro.product.cpu.abilist64";
179static const char ZYGOTE_NICE_NAME[] = "zygote64";
180#else
181static const char ABI_LIST_PROPERTY[] = "ro.product.cpu.abilist32";
182static const char ZYGOTE_NICE_NAME[] = "zygote";
183#endif
184
185int main(int argc, char* const argv[])
186{
187    if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) < 0) {
188        LOG_ALWAYS_FATAL("PR_SET_NO_NEW_PRIVS failed: %s", strerror(errno));
189    }
190
191    AppRuntime runtime(argv[0], computeArgBlockSize(argc, argv));
192    // Process command line arguments
193    // ignore argv[0]
194    argc--;
195    argv++;
196
197    // Everything up to '--' or first non '-' arg goes to the vm.
198    //
199    // The first argument after the VM args is the "parent dir", which
200    // is currently unused.
201    //
202    // After the parent dir, we expect one or more the following internal
203    // arguments :
204    //
205    // --zygote : Start in zygote mode
206    // --start-system-server : Start the system server.
207    // --application : Start in application (stand alone, non zygote) mode.
208    // --nice-name : The nice name for this process.
209    //
210    // For non zygote starts, these arguments will be followed by
211    // the main class name. All remaining arguments are passed to
212    // the main method of this class.
213    //
214    // For zygote starts, all remaining arguments are passed to the zygote.
215    // main function.
216    //
217    // Note that we must copy argument string values since we will rewrite the
218    // entire argument block when we apply the nice name to argv0.
219
220    int i;
221    for (i = 0; i < argc; i++) {
222        if (argv[i][0] != '-') {
223            break;
224        }
225        if (argv[i][1] == '-' && argv[i][2] == 0) {
226            ++i; // Skip --.
227            break;
228        }
229        runtime.addOption(strdup(argv[i]));
230    }
231
232    // Parse runtime arguments.  Stop at first unrecognized option.
233    bool zygote = false;
234    bool startSystemServer = false;
235    bool application = false;
236    String8 niceName;
237    String8 className;
238
239    ++i;  // Skip unused "parent dir" argument.
240    while (i < argc) {
241        const char* arg = argv[i++];
242        if (strcmp(arg, "--zygote") == 0) {
243            zygote = true;
244            niceName = ZYGOTE_NICE_NAME;
245        } else if (strcmp(arg, "--start-system-server") == 0) {
246            startSystemServer = true;
247        } else if (strcmp(arg, "--application") == 0) {
248            application = true;
249        } else if (strncmp(arg, "--nice-name=", 12) == 0) {
250            niceName.setTo(arg + 12);
251        } else if (strncmp(arg, "--", 2) != 0) {
252            className.setTo(arg);
253            break;
254        } else {
255            --i;
256            break;
257        }
258    }
259
260    Vector<String8> args;
261    if (!className.isEmpty()) {
262        // We're not in zygote mode, the only argument we need to pass
263        // to RuntimeInit is the application argument.
264        //
265        // The Remainder of args get passed to startup class main(). Make
266        // copies of them before we overwrite them with the process name.
267        args.add(application ? String8("application") : String8("tool"));
268        runtime.setClassNameAndArgs(className, argc - i, argv + i);
269    } else {
270        // We're in zygote mode.
271        maybeCreateDalvikCache();
272
273        if (startSystemServer) {
274            args.add(String8("start-system-server"));
275        }
276
277        char prop[PROP_VALUE_MAX];
278        if (property_get(ABI_LIST_PROPERTY, prop, NULL) == 0) {
279            LOG_ALWAYS_FATAL("app_process: Unable to determine ABI list from property %s.",
280                ABI_LIST_PROPERTY);
281            return 11;
282        }
283
284        String8 abiFlag("--abi-list=");
285        abiFlag.append(prop);
286        args.add(abiFlag);
287
288        // In zygote mode, pass all remaining arguments to the zygote
289        // main() method.
290        for (; i < argc; ++i) {
291            args.add(String8(argv[i]));
292        }
293    }
294
295    if (!niceName.isEmpty()) {
296        runtime.setArgv0(niceName.string(), true /* setProcName */);
297    }
298
299    if (zygote) {
300        runtime.start("com.android.internal.os.ZygoteInit", args, zygote);
301    } else if (className) {
302        runtime.start("com.android.internal.os.RuntimeInit", args, zygote);
303    } else {
304        fprintf(stderr, "Error: no class name or --zygote supplied.\n");
305        app_usage();
306        LOG_ALWAYS_FATAL("app_process: no class name or --zygote supplied.");
307    }
308}
309