tty: add support for 'passenv' flag to /bin/login

This change makes it possible tell the bundled/built-in getty to call
/bin/login with the '-p' flag, to preserve any environment set in the
Finit .conf files.

Issue #286

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

src/getty.c

@@ -49,6 +49,7 @@
 #endif
 
 static long logname_len = 32;	/* useradd(1) limit at 32 chars */
+static int  passenv     = 0;	/* Set /bin/login -p or not     */
 
 /*
  * Read one character from stdin.
@@ -185,7 +186,10 @@ static int do_login(char *name)
 {
 	struct stat st;
 
-	execl(_PATH_LOGIN, _PATH_LOGIN, name, NULL);
+	if (passenv)
+		execl(_PATH_LOGIN, _PATH_LOGIN, "-p", name, NULL);
+	else
+		execl(_PATH_LOGIN, _PATH_LOGIN, name, NULL);
 
 	/*
 	 * Failed to exec login, should not happen on normal systems.
@@ -252,11 +256,14 @@ int main(int argc, char *argv[])
 	char *tty, *speed = "0", *term = NULL;
 	int c;
 
-	while ((c = getopt(argc, argv, "h?")) != EOF) {
+	while ((c = getopt(argc, argv, "h?p")) != EOF) {
 		switch(c) {
 		case 'h':
 		case '?':
 			return usage(0);
+		case 'p':
+			passenv = 1;
+			break;
 		default:
 			return usage(1);
 		}

src/tty.c

@@ -154,6 +154,7 @@ char *tty_atcon(void)
 int tty_parse_args(char *cmd, struct tty *tty)
 {
 	char  *dev = NULL;
+	int passenv = 0;
 	size_t i;
 
 	do {
@@ -165,6 +166,8 @@ int tty_parse_args(char *cmd, struct tty *tty)
 			tty->nologin = 1;
 		else if (!strcmp(cmd, "notty"))
 			tty->notty = 1;		/* for board bringup */
+		else if (!strcmp(cmd, "passenv"))
+			passenv = 1;
 		else if (!strcmp(cmd, "rescue"))
 			tty->rescue = 1;	/* for rescue shells */
 		else if (whichp(cmd))		/* in $PATH? */
@@ -228,8 +231,15 @@ int tty_parse_args(char *cmd, struct tty *tty)
 	   tty->dev, tty->baud ?: "0", tty->term ?: "N/A");
 
 	/* Built-in getty now comes as standalone program */
-	if (!tty->cmd)
+	if (!tty->cmd) {
+		if (passenv && tty->num < NELEMS(tty->args)) {
+			for (i = tty->num; i > 0; i--)
+				tty->args[i] = tty->args[i - 1];
+			tty->args[0] = "-p";
+			tty->num++;
+		}
 		tty->cmd = _PATH_GETTY;
+	}
 
 	return 0;
 }