init: add 'enable <service>' to negate "service <service>... disabled"

enable <servicename>
   Turns a disabled service into an enabled one as if the service did not
   specify disabled in the rc file.
   It will also start the service if needed.

Bug: 14472973
Change-Id: Id0b49cc687a2bc74f6f92e066c617724cc94908d
Signed-off-by: JP Abgrall <jpa@google.com>

init/builtins.c

@@ -196,6 +196,8 @@ static void service_start_if_not_disabled(struct service *svc)
 {
     if (!(svc->flags & SVC_DISABLED)) {
         service_start(svc, NULL);
+    } else {
+        svc->flags |= SVC_DISABLED_START;
     }
 }
 
@@ -238,6 +240,21 @@ int do_domainname(int nargs, char **args)
     return write_file("/proc/sys/kernel/domainname", args[1]);
 }
 
+int do_enable(int nargs, char **args)
+{
+    struct service *svc;
+    svc = service_find_by_name(args[1]);
+    if (svc) {
+        svc->flags &= ~(SVC_DISABLED | SVC_RC_DISABLED);
+        if (svc->flags & SVC_DISABLED_START) {
+            service_start(svc, NULL);
+        }
+    } else {
+        return -1;
+    }
+    return 0;
+}
+
 int do_exec(int nargs, char **args)
 {
     return -1;

init/init.c

@@ -164,7 +164,7 @@ void service_start(struct service *svc, const char *dynamic_args)
          * state and immediately takes it out of the restarting
          * state if it was in there
          */
-    svc->flags &= (~(SVC_DISABLED|SVC_RESTARTING|SVC_RESET|SVC_RESTART));
+    svc->flags &= (~(SVC_DISABLED|SVC_RESTARTING|SVC_RESET|SVC_RESTART|SVC_DISABLED_START));
     svc->time_started = 0;
 
         /* running processes require no additional work -- if
@@ -364,7 +364,7 @@ static void service_stop_or_reset(struct service *svc, int how)
 {
     /* The service is still SVC_RUNNING until its process exits, but if it has
      * already exited it shoudn't attempt a restart yet. */
-    svc->flags &= (~SVC_RESTARTING);
+    svc->flags &= ~(SVC_RESTARTING | SVC_DISABLED_START);
 
     if ((how != SVC_DISABLED) && (how != SVC_RESET) && (how != SVC_RESTART)) {
         /* Hrm, an illegal flag.  Default to SVC_DISABLED */

init/init.h

@@ -74,6 +74,7 @@ struct svcenvinfo {
                                  so it can be restarted with its class */
 #define SVC_RC_DISABLED 0x80  /* Remember if the disabled flag was set in the rc script */
 #define SVC_RESTART     0x100 /* Use to safely restart (stop, wait, start) a service */
+#define SVC_DISABLED_START 0x200 /* a start was requested but it was disabled at the time */
 
 #define NR_SVC_SUPP_GIDS 12    /* twelve supplementary groups */
 

init/init_parser.c

@@ -98,6 +98,7 @@ static int lookup_keyword(const char *s)
         if (!strcmp(s, "omainname")) return K_domainname;
         break;
     case 'e':
+        if (!strcmp(s, "nable")) return K_enable;
         if (!strcmp(s, "xec")) return K_exec;
         if (!strcmp(s, "xport")) return K_export;
         break;

init/keywords.h

@@ -6,6 +6,7 @@ int do_class_start(int nargs, char **args);
 int do_class_stop(int nargs, char **args);
 int do_class_reset(int nargs, char **args);
 int do_domainname(int nargs, char **args);
+int do_enable(int nargs, char **args);
 int do_exec(int nargs, char **args);
 int do_export(int nargs, char **args);
 int do_hostname(int nargs, char **args);
@@ -55,6 +56,7 @@ enum {
     KEYWORD(critical,    OPTION,  0, 0)
     KEYWORD(disabled,    OPTION,  0, 0)
     KEYWORD(domainname,  COMMAND, 1, do_domainname)
+    KEYWORD(enable,      COMMAND, 1, do_enable)
     KEYWORD(exec,        COMMAND, 1, do_exec)
     KEYWORD(export,      COMMAND, 2, do_export)
     KEYWORD(group,       OPTION,  0, 0)

init/readme.txt

@@ -178,6 +178,16 @@ class_stop <serviceclass>
 domainname <name>
    Set the domain name.
 
+enable <servicename>
+   Turns a disabled service into an enabled one as if the service did not
+   specify disabled.
+   If the service is supposed to be running, it will be started now.
+   Typically used when the bootloader sets a variable that indicates a specific
+   service should be started when needed. E.g.
+     on property:ro.boot.myfancyhardware=1
+        enable my_fancy_service_for_my_fancy_hardware
+
+
 insmod <path>
    Install the module at <path>