3. dexopt操作
Apk文件其实只是一个归档zip压缩包,而我们编写的代码最终都编译成了.dex文件,但为了提高运行性能,android系统并不会直接执行.dex,而是会在安装过程中执行dexopt操作来优化.dex文件,最终android系统执行的时优化后的'odex'文件(注意:这个odex文件的后缀也是.dex,其路径在data/dalvik-cache)。对于dalvik虚拟机,dexopt就是优化操作,而对于art虚拟机,dexopt执行的则是dex2oat操作,既将.dex文件翻译成oat文件。关于art和dex2oat的更多信息请看后文。
这里我们先来看看PMS的dexopt操作:
3.1 performDexOptLI()
这个方法的核心是
final int ret = mInstaller.dexopt(path, sharedGid, !isForwardLocked(pkg), pkg.packageName, dexCodeInstructionSet, vmSafeMode);
其作用就是调用PMS的mInstaller成员变量的dexopt操作。
3.2 Installer.dexopt
Installer类的dexopt方法又调用InstallerConnection类的dexopt方法,来看看这个方法:
public int dexopt(String apkPath, int uid, boolean isPublic, String pkgName,
String instructionSet, boolean vmSafeMode) {
StringBuilder builder = new StringBuilder("dexopt");
builder.append(' ');
builder.append(apkPath);
builder.append(' ');
builder.append(uid);
builder.append(isPublic ? " 1" : " 0");
builder.append(' ');
builder.append(pkgName);
builder.append(' ');
builder.append(instructionSet);
builder.append(' ');
builder.append(vmSafeMode ? " 1" : " 0"); return execute(builder.toString());
} public synchronized String transact(String cmd) { if (!connect()) {
Slog.e(TAG, "connection failed"); return "-1";
} if (!writeCommand(cmd)) { /*
* If installd died and restarted in the background (unlikely but
* possible) we'll fail on the next write (this one). Try to
* reconnect and write the command one more time before giving up.
*/
Slog.e(TAG, "write command failed? reconnect!"); if (!connect() || !writeCommand(cmd)) { return "-1";
}
} if (LOCAL_DEBUG) {
Slog.i(TAG, "send: '" + cmd + "'");
} final int replyLength = readReply(); if (replyLength > 0) {
String s = new String(buf, 0, replyLength); if (LOCAL_DEBUG) {
Slog.i(TAG, "recv: '" + s + "'");
} return s;
} else { if (LOCAL_DEBUG) {
Slog.i(TAG, "fail");
} return "-1";
}
} public int execute(String cmd) {
String res = transact(cmd); try { return Integer.parseInt(res);
} catch (NumberFormatException ex) { return -1;
}
} private boolean connect() { if (mSocket != null) { return true;
}
Slog.i(TAG, "connecting..."); try {
mSocket = new LocalSocket();
LocalSocketAddress address = new LocalSocketAddress("installd",
LocalSocketAddress.Namespace.RESERVED);
mSocket.connect(address);
mIn = mSocket.getInputStream();
mOut = mSocket.getOutputStream();
} catch (IOException ex) {
disconnect(); return false;
} return true;
}由上面的几个方法可以知道,最终dexopt操作是通过socket的方式来跨进程通知守护进程installd,由其去执行dexopt操作。
3.3 commands::dexopt()
最终守护进程installd会调用Commands.c文件(位于/source/framework/native/cmds/installd)的dexopt方法。
int dexopt(const char *apk_path, uid_t uid, bool is_public, const char *pkgname, const char *instruction_set, bool vm_safe_mode, bool is_patchoat){ struct utimbuf ut;
struct stat input_stat, dex_stat;
char out_path[PKG_PATH_MAX]; char persist_sys_dalvik_vm_lib[PROPERTY_VALUE_MAX]; char *end; const char *input_file; char in_odex_path[PKG_PATH_MAX]; int res, input_fd=-1, out_fd=-1;
...
... pid_t pid;
pid = fork(); if (pid == 0) { /* child -- drop privileges before continuing */
if (setgid(uid) != 0) {
ALOGE("setgid(%d) failed in installd during dexopt\n", uid); exit(64);
} if (setuid(uid) != 0) {
ALOGE("setuid(%d) failed in installd during dexopt\n", uid); exit(65);
} // drop capabilities
struct __user_cap_header_struct capheader;
struct __user_cap_data_struct capdata[2];
memset(&capheader, 0, sizeof(capheader)); memset(&capdata, 0, sizeof(capdata));
capheader.version = _LINUX_CAPABILITY_VERSION_3; if (capset(&capheader, &capdata[0]) < 0) {
ALOGE("capset failed: %s\n", strerror(errno)); exit(66);
} if (set_sched_policy(0, SP_BACKGROUND) < 0) {
ALOGE("set_sched_policy failed: %s\n", strerror(errno)); exit(70);
} if (flock(out_fd, LOCK_EX | LOCK_NB) != 0) {
ALOGE("flock(%s) failed: %s\n", out_path, strerror(errno)); exit(67);
} if (strncmp(persist_sys_dalvik_vm_lib, "libdvm", 6) == 0) {
run_dexopt(input_fd, out_fd, input_file, out_path);
} else if (strncmp(persist_sys_dalvik_vm_lib, "libart", 6) == 0) { if (is_patchoat) {
run_patchoat(input_fd, out_fd, input_file, out_path, pkgname, instruction_set);
} else {
run_dex2oat(input_fd, out_fd, input_file, out_path, pkgname, instruction_set,
vm_safe_mode);
}
} else { exit(69); /* Unexpected persist.sys.dalvik.vm.lib value */
} exit(68); /* only get here on exec failure */
} else {
res = wait_child(pid); if (res == 0) {
ALOGV("DexInv: --- END '%s' (success) ---\n", input_file);
} else {
ALOGE("DexInv: --- END '%s' --- status=0x%04x, process failed\n", input_file, res); goto fail;
}
}
ut.actime = input_stat.st_atime;
ut.modtime = input_stat.st_mtime;
utime(out_path, &ut);
close(out_fd);
close(input_fd); return 0;
fail: if (out_fd >= 0) {
close(out_fd);
unlink(out_path);
} if (input_fd >= 0) {
close(input_fd);
} return -1;
}由上面的代码可以发现,installd在做了些操作后,fork出了一个新的进程,根据虚拟机的类型为libdvm或libart分别执行run_dexopt或run_dex2oat(如果为is_patchoat,则是run_patchoat)操作。
4. 更新权限信息
dexopt操作执行完后,installNewPackageLI()方法就会走到updateSettingsLI()来更新设置信息,而更新设置信息主要是权限信息,所以直接来看updatePermissionsLPw();
4.1 updatePermissionsLPw
private void updatePermissionsLPw(String changingPkg,
PackageParser.Package pkgInfo, int flags) { // Make sure there are no dangling permission trees.
Iterator<BasePermission> it = mSettings.mPermissionTrees.values().iterator(); while (it.hasNext()) { final BasePermission bp = it.next(); if (bp.packageSetting == null) { // We may not yet have parsed the package, so just see if
// we still know about its settings.
bp.packageSetting = mSettings.mPackages.get(bp.sourcePackage);
} if (bp.packageSetting == null) {
Slog.w(TAG, "Removing dangling permission tree: " + bp.name
+ " from package " + bp.sourcePackage);
it.remove();
} else if (changingPkg != null && changingPkg.equals(bp.sourcePackage)) { if (pkgInfo == null || !hasPermission(pkgInfo, bp.name)) {
Slog.i(TAG, "Removing old permission tree: " + bp.name
+ " from package " + bp.sourcePackage);
flags |= UPDATE_PERMISSIONS_ALL;
it.remove();
}
}
} // Make sure all dynamic permissions have been assigned to a package,
// and make sure there are no dangling permissions.
it = mSettings.mPermissions.values().iterator(); while (it.hasNext()) { final BasePermission bp = it.next(); if (bp.type == BasePermission.TYPE_DYNAMIC) { if (DEBUG_SETTINGS) Log.v(TAG, "Dynamic permission: name="
+ bp.name + " pkg=" + bp.sourcePackage
+ " info=" + bp.pendingInfo); if (bp.packageSetting == null && bp.pendingInfo != null) { final BasePermission tree = findPermissionTreeLP(bp.name); if (tree != null && tree.perm != null) {
bp.packageSetting = tree.packageSetting;
bp.perm = new PackageParser.Permission(tree.perm.owner, new PermissionInfo(bp.pendingInfo));
bp.perm.info.packageName = tree.perm.info.packageName;
bp.perm.info.name = bp.name;
bp.uid = tree.uid;
}
}
} if (bp.packageSetting == null) { // We may not yet have parsed the package, so just see if
// we still know about its settings.
bp.packageSetting = mSettings.mPackages.get(bp.sourcePackage);
} if (bp.packageSetting == null) {
Slog.w(TAG, "Removing dangling permission: " + bp.name
+ " from package " + bp.sourcePackage);
it.remove();
} else if (changingPkg != null && changingPkg.equals(bp.sourcePackage)) { if (pkgInfo == null || !hasPermission(pkgInfo, bp.name)) {
Slog.i(TAG, "Removing old permission: " + bp.name
+ " from package " + bp.sourcePackage);
flags |= UPDATE_PERMISSIONS_ALL;
it.remove();
}
}
} // Now update the permissions for all packages, in particular
// replace the granted permissions of the system packages.
if ((flags&UPDATE_PERMISSIONS_ALL) != 0) { for (PackageParser.Package pkg : mPackages.values()) { if (pkg != pkgInfo) {
grantPermissionsLPw(pkg, (flags&UPDATE_PERMISSIONS_REPLACE_ALL) != 0,
changingPkg);
}
}
}
if (pkgInfo != null) {
grantPermissionsLPw(pkgInfo, (flags&UPDATE_PERMISSIONS_REPLACE_PKG) != 0, changingPkg);
}
} private void grantPermissionsLPw(PackageParser.Package pkg, boolean replace,
String packageOfInterest) { final PackageSetting ps = (PackageSetting) pkg.mExtras; if (ps == null) { return;
} final GrantedPermissions gp = ps.sharedUser != null ? ps.sharedUser : ps;
HashSet<String> origPermissions = gp.grantedPermissions; boolean changedPermission = false; if (replace) {
ps.permissionsFixed = false; if (gp == ps) {
origPermissions = new HashSet<String>(gp.grantedPermissions);
gp.grantedPermissions.clear();
gp.gids = mGlobalGids;
}
} if (gp.gids == null) {
gp.gids = mGlobalGids;
} final int N = pkg.requestedPermissions.size(); for (int i=0; i<N; i++) { final String name = pkg.requestedPermissions.get(i); final boolean required = pkg.requestedPermissionsRequired.get(i); final BasePermission bp = mSettings.mPermissions.get(name); if (DEBUG_INSTALL) { if (gp != ps) {
Log.i(TAG, "Package " + pkg.packageName + " checking " + name + ": " + bp);
}
} if (bp == null || bp.packageSetting == null) { if (packageOfInterest == null || packageOfInterest.equals(pkg.packageName)) {
Slog.w(TAG, "Unknown permission " + name
+ " in package " + pkg.packageName);
} continue;
} final String perm = bp.name; boolean allowed; boolean allowedSig = false; if ((bp.protectionLevel&PermissionInfo.PROTECTION_FLAG_APPOP) != 0) { // Keep track of app op permissions.
ArraySet<String> pkgs = mAppOpPermissionPackages.get(bp.name); if (pkgs == null) {
pkgs = new ArraySet<>();
mAppOpPermissionPackages.put(bp.name, pkgs);
}
pkgs.add(pkg.packageName);
} final int level = bp.protectionLevel & PermissionInfo.PROTECTION_MASK_BASE; if (level == PermissionInfo.PROTECTION_NORMAL
|| level == PermissionInfo.PROTECTION_DANGEROUS) { // We grant a normal or dangerous permission if any of the following
// are true:
// 1) The permission is required
// 2) The permission is optional, but was granted in the past
// 3) The permission is optional, but was requested by an
// app in /system (not /data)
//
// Otherwise, reject the permission.
allowed = (required || origPermissions.contains(perm)
|| (isSystemApp(ps) && !isUpdatedSystemApp(ps)));
} else if (bp.packageSetting == null) { // This permission is invalid; skip it.
allowed = false;
} else if (level == PermissionInfo.PROTECTION_SIGNATURE) {
allowed = grantSignaturePermission(perm, pkg, bp, origPermissions); if (allowed) {
allowedSig = true;
}
} else {
allowed = false;
} if (DEBUG_INSTALL) { if (gp != ps) {
Log.i(TAG, "Package " + pkg.packageName + " granting " + perm);
}
} if (allowed) { if (!isSystemApp(ps) && ps.permissionsFixed) { // If this is an existing, non-system package, then
// we can't add any new permissions to it.
if (!allowedSig && !gp.grantedPermissions.contains(perm)) { // Except... if this is a permission that was added
// to the platform (note: need to only do this when
// updating the platform).
allowed = isNewPlatformPermissionForPackage(perm, pkg);
}
} if (allowed) { if (!gp.grantedPermissions.contains(perm)) {
changedPermission = true;
gp.grantedPermissions.add(perm);
gp.gids = appendInts(gp.gids, bp.gids);
} else if (!ps.haveGids) {
gp.gids = appendInts(gp.gids, bp.gids);
}
} else { if (packageOfInterest == null || packageOfInterest.equals(pkg.packageName)) {
Slog.w(TAG, "Not granting permission " + perm
+ " to package " + pkg.packageName
+ " because it was previously installed without");
}
}
} else { if (gp.grantedPermissions.remove(perm)) {
changedPermission = true;
gp.gids = removeInts(gp.gids, bp.gids);
Slog.i(TAG, "Un-granting permission " + perm
+ " from package " + pkg.packageName
+ " (protectionLevel=" + bp.protectionLevel
+ " flags=0x" + Integer.toHexString(pkg.applicationInfo.flags)
+ ")");
} else if ((bp.protectionLevel&PermissionInfo.PROTECTION_FLAG_APPOP) == 0) { // Don't print warning for app op permissions, since it is fine for them
// not to be granted, there is a UI for the user to decide.
if (packageOfInterest == null || packageOfInterest.equals(pkg.packageName)) {
Slog.w(TAG, "Not granting permission " + perm
+ " to package " + pkg.packageName
+ " (protectionLevel=" + bp.protectionLevel
+ " flags=0x" + Integer.toHexString(pkg.applicationInfo.flags)
+ ")");
}
}
}
} if ((changedPermission || replace) && !ps.permissionsFixed &&
!isSystemApp(ps) || isUpdatedSystemApp(ps)){ // This is the first that we have heard about this package, so the
// permissions we have now selected are fixed until explicitly
// changed.
ps.permissionsFixed = true;
}
ps.haveGids = true;
}由上面两个方法可以看到,在apk的安装时PMS会将该app的所有权限都记录下来并更新到PMS的mAppOpPermissionPackages成员变量里面,并判定是否授予该app请求的权限。
4.2 完成安装
还记得前面说过的在processPendingInstall方法在执行installPackageLi后会执行以下语句
if (res.returnCode == PackageManager.INSTALL_SUCCEEDED && doRestore) { // Pass responsibility to the Backup Manager. It will perform a
// restore if appropriate, then pass responsibility back to the
// Package Manager to run the post-install observer callbacks
// and broadcasts.
IBackupManager bm = IBackupManager.Stub.asInterface(
ServiceManager.getService(Context.BACKUP_SERVICE)); if (bm != null) { if (DEBUG_INSTALL) Log.v(TAG, "token " + token
+ " to BM for possible restore"); try {
bm.restoreAtInstall(res.pkg.applicationInfo.packageName, token);
} catch (RemoteException e) { // can't happen; the backup manager is local
} catch (Exception e) {
Slog.e(TAG, "Exception trying to enqueue restore", e);
doRestore = false;
}
} else {
Slog.e(TAG, "Backup Manager not found!");
doRestore = false;
}
}我也不是很清楚为什么系统会调用IBackupManager的restoreAtInstall方法,不过发现在BackupManagerService的restoreAtInstall方法中会有以下代码:
... if (skip) { // Auto-restore disabled or no way to attempt a restore; just tell the Package
// Manager to proceed with the post-install handling for this package.
if (DEBUG) Slog.v(TAG, "Finishing install immediately"); try {
mPackageManagerBinder.finishPackageInstall(token);
} catch (RemoteException e) { /* can't happen */ }
}
...最终restoreAtInstall方法又会调用PMS的finishPackageInstall方法,而此方法最终会发送Intent.ACTION_PACKAGE_ADDED广播，apk的安装就到到此结束了。