[runlevel] Expect systemctl to reside in /usr/bin. Fixes JB#50483

DSME expects to find /bin/systemctl to perform systemd style
shutdown / reboot. At some stage the binary location changed,
which made DSME fallback to using telinit. Which systemd does
support, but shutdown behavior is slightly different. Which
leads to obscure problems with determining boot reason during
the next bootup / leaves unwanted RTC wakeup alarms active.

Expect systemctl to reside in /usr/bin, but for backwards
compatibility allow it to reside in /bin too.

Use wrapper for system() for equating child process getting
killed by SIGTERM with it making an exit(0) to avoid false
negatives for initiating shutdown / reboot.

Signed-off-by: Simo Piiroinen <simo.piiroinen@jollamobile.com>

modules/runlevel.c

@@ -3,9 +3,13 @@
 
    DSME internal runlevel control
    <p>
-   Copyright (C) 2009-2010 Nokia Corporation.
+   Copyright (c) 2009 - 2010 Nokia Corporation.
+   Copyright (c) 2012 - 2020 Jolla Ltd.
+   Copyright (c) 2020 Open Mobile Platform LLC.
 
    @author Semi Malinen <semi.malinen@nokia.com>
+   @author Pekka Lundstrom <pekka.lundstrom@jollamobile.com>
+   @author Simo Piiroinen <simo.piiroinen@jollamobile.com>
 
    This file is part of Dsme.
 
@@ -38,6 +42,83 @@
 static bool change_runlevel(dsme_runlevel_t runlevel);
 static bool remount_mmc_readonly(void);
 
+/** Wrapper for system() calls
+ *
+ * Executes the command, normalizes the return value
+ * and performs some common diagnostic logging.
+ *
+ * Note: Getting the child process killed with SIGTERM
+ *       is equated with it making exit(0) - this avoids
+ *       some fallback logic assuming that shutdown/reboot
+ *       did not commence because e.g. telinit got killed
+ *       by init due to shutdown/reboot ...
+ *
+ * \param command  command line to execute
+ * \return exit code from child process, or
+ *         -1 if execution fails / child process is killed,
+ */
+static int
+system_wrapper(const char *command)
+{
+    int         result      = -1;
+    int         status      = -1;
+    char        exited[32]  = "";
+    char        trapped[32] = "";
+    const char *dumped      = "";
+
+    dsme_log(LOG_NOTICE, "Executing: %s", command);
+
+    if( (status = system(command)) == -1 ) {
+        snprintf(exited, sizeof exited, " exec=failed");
+    }
+    else {
+        if( WIFSIGNALED(status) ) {
+            snprintf(trapped, sizeof trapped, " signal=%s",
+                     strsignal(WTERMSIG(status)));
+            if( WTERMSIG(status) == SIGTERM )
+                result = 0;
+        }
+
+        if( WCOREDUMP(status) )
+            dumped = " core=dumped";
+
+        if( WIFEXITED(status) ) {
+            result = WEXITSTATUS(status);
+            snprintf(exited, sizeof exited, " exit_code=%d", result);
+        }
+    }
+
+    dsme_log(LOG_NOTICE, "Executed:  %s -%s%s%s result=%d",
+             command, exited, trapped, dumped, result);
+
+    return result;
+}
+
+/** Locate where systemd systemctl binary is installed
+ *
+ * Try currently expected systemctl location first, then where
+ * older systemd versions are known to have kept the binary.
+ *
+ * \return path to systemctl, or NULL in case it is not found
+ */
+static const char *
+locate_systemctl_binary(void)
+{
+    static const char * const lut[] = {
+        "/usr/bin/systemctl",
+        "/bin/systemctl",
+        0
+    };
+    const char *path = 0;
+    for( size_t i = 0; (path = lut[i]); ++i ) {
+        if( access(path, X_OK) == 0 )
+            break;
+    }
+
+    dsme_log(LOG_DEBUG, "systemctl binary = %s", path ?: "unknown");
+    return path;
+}
+
 /**
    This function is used to tell init to change to new runlevel.
    Currently telinit is used.
@@ -56,18 +137,15 @@ static bool change_runlevel(dsme_runlevel_t runlevel)
   } else {
       return false;
   }
-  dsme_log(LOG_NOTICE, "Issuing %s", command);
-
-  if (system(command) != 0) {
+  if (system_wrapper(command) != 0) {
       dsme_log(LOG_CRIT, "failed to change runlevel, trying again in 2s");
       sleep(2);
-      return system(command) == 0;
+      return system_wrapper(command) == 0;
   }
 
   return true;
 }
 
-
 /*
  * This function will do the shutdown or reboot (based on desired runlevel).
  * If the telinit is present, runlevel change is requested.
@@ -92,17 +170,17 @@ static void shutdown(dsme_runlevel_t runlevel)
                                                 "Malf");
 
   /* If we have systemd, use systemctl commands */
-  if (access("/bin/systemctl", X_OK) == 0) {
+  const char *systemctl;
+  if( (systemctl = locate_systemctl_binary()) ) {
       if (runlevel == DSME_RUNLEVEL_SHUTDOWN) {
-          snprintf(command, sizeof(command), "/bin/systemctl --no-block poweroff");
+          snprintf(command, sizeof command, "%s --no-block poweroff", systemctl);
       } else if (runlevel == DSME_RUNLEVEL_REBOOT) {
-          snprintf(command, sizeof(command), "/bin/systemctl --no-block reboot");
+          snprintf(command, sizeof command, "%s --no-block reboot", systemctl);
       } else {
           dsme_log(LOG_WARNING, "MALF not supported by our systemd implementation");
-	  goto fail_and_exit;
+          goto fail_and_exit;
       }
-      dsme_log(LOG_NOTICE, "Issuing %s", command);
-      if (system(command) != 0) {
+      if (system_wrapper(command) != 0) {
           dsme_log(LOG_WARNING, "command %s failed: %m", command);
           /* We ignore error. No retry or anything else */
       }
@@ -123,12 +201,11 @@ static void shutdown(dsme_runlevel_t runlevel)
           } else {
               snprintf(command, sizeof(command), "/usr/sbin/poweroff");
           }
-          dsme_log(LOG_CRIT, "Issuing %s", command);
-          if (system(command) != 0) {
-	    dsme_log(LOG_ERR, "%s failed, trying again in 3s", command);
+          if (system_wrapper(command) != 0) {
+              dsme_log(LOG_ERR, "%s failed, trying again in 3s", command);
               sleep(3);
-              if (system(command) != 0) {
-		dsme_log(LOG_ERR, "%s failed again", command);
+              if (system_wrapper(command) != 0) {
+                  dsme_log(LOG_ERR, "%s failed again", command);
                   goto fail_and_exit;
               }
           }
@@ -138,12 +215,11 @@ static void shutdown(dsme_runlevel_t runlevel)
           } else {
               snprintf(command, sizeof(command), "/usr/sbin/reboot");
           }
-          dsme_log(LOG_CRIT, "Issuing %s", command);
-          if (system(command) != 0) {
-	    dsme_log(LOG_ERR, "%s failed, trying again in 3s", command);
+          if (system_wrapper(command) != 0) {
+              dsme_log(LOG_ERR, "%s failed, trying again in 3s", command);
               sleep(3);
-              if (system(command) != 0) {
-		dsme_log(LOG_ERR, "%s failed again", command);
+              if (system_wrapper(command) != 0) {
+                  dsme_log(LOG_ERR, "%s failed again", command);
                   goto fail_and_exit;
               }
           }