OTA only adds Main if isMainUserPermanentAdmin

On OTA to Android U, we bestow upon one user the MainUser title. Not all
devices need to have a MainUser though, depnding on their configuration.
Nonetheless, we were previously always adding MainUser on OTA.

For HSUM devices that do NOT have config_isMainUserPermanentAdmin, we should
not be setting a MainUser on OTA, so we fix this here.

On non-HSUM, we continue to make user 0 the MainUser on OTA regardless
of configuration; non-HSUM user 0 being Main is just an invariant.

Moreover, we update the emulation logic to also take into account
config_isMainUserPermanentAdmin and the invariance.
The updated logic of emulation is:

non-HSUM -> emulate HSUM
Rule: in HSUM, we never have Sys be Main. We set a new main iff the config says to.
Scenarios:
* if main=Sys (usual phone case): Remove Main from system; if isMainUserPermanentAdmin(), switch/set a new Main.
* if no main (severly aberrant case): if isMainUserPermanentAdmin(), set a new Main.
* if main=other (aberrant case): leave as is

HSUM -> emulate non-HSUM
Rule: in non-HSUM, we always make Sys to be Main
Scenarios:
* if main=Sys (severely aberrant case): leave as is
* if no main (usual for Auto):  always make Sys the Main
* if main=other (usual for tablet): always switch Main to system

Test: manual OTA from T to U
Test: manual emulate different modes
Bug: 272295293
Change-Id: Id915203fe07b65cdd0e7e08df92fe93454be4f6f

2 files changed, 22 insertions, 18 deletions

diff --git a/services/core/java/com/android/server/pm/UserManagerService.java b/services/core/java/com/android/server/pm/UserManagerService.java
index dd014ee637c7..0d9ab670cc2f 100644
--- a/services/core/java/com/android/server/pm/UserManagerService.java
+++ b/services/core/java/com/android/server/pm/UserManagerService.java
@@ -3473,15 +3473,15 @@ public class UserManagerService extends IUserManager.Stub {
                     return;
                 }
                 final int oldMainUserId = getMainUserIdUnchecked();
-                final int oldFlags = systemUserData.info.flags;
-                final int newFlags;
+                final int oldSysFlags = systemUserData.info.flags;
+                final int newSysFlags;
                 final String newUserType;
                 if (newHeadlessSystemUserMode) {
                     newUserType = UserManager.USER_TYPE_SYSTEM_HEADLESS;
-                    newFlags = oldFlags & ~UserInfo.FLAG_FULL & ~UserInfo.FLAG_MAIN;
+                    newSysFlags = oldSysFlags & ~UserInfo.FLAG_FULL & ~UserInfo.FLAG_MAIN;
                 } else {
                     newUserType = UserManager.USER_TYPE_FULL_SYSTEM;
-                    newFlags = oldFlags | UserInfo.FLAG_FULL;
+                    newSysFlags = oldSysFlags | UserInfo.FLAG_FULL | UserInfo.FLAG_MAIN;
                 }
 
                 if (systemUserData.info.userType.equals(newUserType)) {
@@ -3492,18 +3492,19 @@ public class UserManagerService extends IUserManager.Stub {
                 Slogf.i(LOG_TAG, "Persisting emulated system user data: type changed from %s to "
                         + "%s, flags changed from %s to %s",
                         systemUserData.info.userType, newUserType,
-                        UserInfo.flagsToString(oldFlags), UserInfo.flagsToString(newFlags));
+                        UserInfo.flagsToString(oldSysFlags), UserInfo.flagsToString(newSysFlags));
 
                 systemUserData.info.userType = newUserType;
-                systemUserData.info.flags = newFlags;
+                systemUserData.info.flags = newSysFlags;
                 writeUserLP(systemUserData);
 
-                // Switch the MainUser to a reasonable choice if needed.
-                // (But if there was no MainUser, we deliberately continue to have no MainUser.)
+                // Designate the MainUser to a reasonable choice if needed.
                 final UserData oldMain = getUserDataNoChecks(oldMainUserId);
                 if (newHeadlessSystemUserMode) {
-                    if (oldMain != null && (oldMain.info.flags & UserInfo.FLAG_SYSTEM) != 0) {
-                        // System was MainUser. So we need a new choice for Main. Pick the oldest.
+                    final boolean mainIsAlreadyNonSystem =
+                            oldMain != null && (oldMain.info.flags & UserInfo.FLAG_SYSTEM) == 0;
+                    if (!mainIsAlreadyNonSystem && isMainUserPermanentAdmin()) {
+                        // We need a new choice for Main. Pick the oldest.
                         // If no oldest, don't set any. Let the BootUserInitializer do that later.
                         final UserInfo newMainUser = getEarliestCreatedFullUser();
                         if (newMainUser != null) {
@@ -3513,16 +3514,16 @@ public class UserManagerService extends IUserManager.Stub {
                         }
                     }
                 } else {
+                    // We already made user 0 Main above. Now strip it from the old Main user.
                     // TODO(b/256624031): For now, we demand the Main user (if there is one) is
                     //  always the system in non-HSUM. In the future, when we relax this, change how
                     //  we handle MAIN.
                     if (oldMain != null && (oldMain.info.flags & UserInfo.FLAG_SYSTEM) == 0) {
-                        // Someone else was the MainUser; transfer it to System.
                         Slogf.i(LOG_TAG, "Transferring Main to user 0 from " + oldMain.info.id);
                         oldMain.info.flags &= ~UserInfo.FLAG_MAIN;
-                        systemUserData.info.flags |= UserInfo.FLAG_MAIN;
                         writeUserLP(oldMain);
-                        writeUserLP(systemUserData);
+                    } else {
+                        Slogf.i(LOG_TAG, "Designated user 0 to be Main");
                     }
                 }
             }
@@ -3779,12 +3780,14 @@ public class UserManagerService extends IUserManager.Stub {
         if (userVersion < 11) {
             // Add FLAG_MAIN
             if (isHeadlessSystemUserMode()) {
-                final UserInfo earliestCreatedUser = getEarliestCreatedFullUser();
-                if (earliestCreatedUser != null) {
-                    earliestCreatedUser.flags |= UserInfo.FLAG_MAIN;
-                    userIdsToWrite.add(earliestCreatedUser.id);
+                if (isMainUserPermanentAdmin()) {
+                    final UserInfo earliestCreatedUser = getEarliestCreatedFullUser();
+                    if (earliestCreatedUser != null) {
+                        earliestCreatedUser.flags |= UserInfo.FLAG_MAIN;
+                        userIdsToWrite.add(earliestCreatedUser.id);
+                    }
                 }
-            } else {
+            } else { // not isHeadlessSystemUserMode
                 synchronized (mUsersLock) {
                     final UserData userData = mUsers.get(UserHandle.USER_SYSTEM);
                     userData.info.flags |= UserInfo.FLAG_MAIN;
diff --git a/services/core/java/com/android/server/pm/UserManagerServiceShellCommand.java b/services/core/java/com/android/server/pm/UserManagerServiceShellCommand.java
index eed2a7896fcd..fd41af38b612 100644
--- a/services/core/java/com/android/server/pm/UserManagerServiceShellCommand.java
+++ b/services/core/java/com/android/server/pm/UserManagerServiceShellCommand.java
@@ -376,6 +376,7 @@ public class UserManagerServiceShellCommand extends ShellCommand {
             final int pid = Process.myPid();
             Slogf.i(LOG_TAG, "Restarting Android runtime(PID=%d) to finalize changes", pid);
             pw.println("Restarting Android runtime to finalize changes");
+            pw.println("The restart may trigger a 'Broken pipe' message; this is to be expected.");
             pw.flush();
 
             // Ideally there should be a cleaner / safer option to restart system_server, but