[BusyBox] another hush patch

[larry at doolittle.boa.org]

This fixes two honest-to-goodness bugs, and starts to pull some of
the job control work into cleanly packaged routines.  I also
tagged all those perror_msg("tcsetpgrp") messages, so we can
more readily focus on problems if any more leak through.

Unfortunately, this patch is based on CVS revision 1.29, before
the latest Vladimir/Andersen commit.  I don't think the work
overlaps, although you might have to fight patch(1) to merge
the two efforts.

        - Larry

--- /home/larry/cvs/busybox/hush.c	Wed May 16 20:01:09 2001
+++ hush.c	Fri May 18 23:28:58 2001
@@ -554,7 +554,7 @@
 		signal(SIGTTOU, SIG_IGN);
 		/* suppress messages when run from /linuxrc mag at sysgo.de */
 		if (tcsetpgrp(0, pi->pgrp) && errno != ENOTTY)
-			perror_msg("tcsetpgrp"); 
+			perror_msg("tcsetpgrp-1"); 
 		signal(SIGTTOU, SIG_DFL);
 		job_list->fg = pi;
 	}
@@ -1263,7 +1263,28 @@
 
 	/* move the shell to the foreground */
 	if (tcsetpgrp(0, getpgrp()) && errno != ENOTTY)
-		perror_msg("tcsetpgrp"); 
+		perror_msg("tcsetpgrp-2"); 
+}
+
+/* Figure out our controlling tty, checking in order stderr,
+ * stdin, and stdout.  If check_pgrp is set, also check that
+ * we belong to the foreground process group associated with
+ * that tty.  The value of ctty is needed in order to call
+ * tcsetpgrp(ctty, ...); */
+int controlling_tty(int check_pgrp)
+{
+	pid_t curpgrp;
+	int ctty;
+
+	if ((curpgrp = tcgetpgrp(ctty = 2)) < 0
+		&& (curpgrp = tcgetpgrp(ctty = 0)) < 0
+		&& (curpgrp = tcgetpgrp(ctty = 1)) < 0)
+		return errno = ENOTTY, -1;
+
+	if (check_pgrp && curpgrp != getpgrp())
+		return errno = EPERM, -1;
+
+	return ctty;
 }
 
 /* run_pipe_real() starts all the jobs, but doesn't wait for anything
@@ -1293,17 +1314,11 @@
 
 	ctty = -1;
 	nextin = 0;
-	pi->pgrp = 0;
+	pi->pgrp = -1;
 
 	/* Check if we are supposed to run in the foreground */
 	if (interactive && pi->followup!=PIPE_BG) {
-		if ((pi->pgrp = tcgetpgrp(ctty = 2)) < 0
-				&& (pi->pgrp = tcgetpgrp(ctty = 0)) < 0
-				&& (pi->pgrp = tcgetpgrp(ctty = 1)) < 0)
-			return errno = ENOTTY, -1;
-
-		if (pi->pgrp < 0 && pi->pgrp != getpgrp())
-			return errno = EPERM, -1;
+		if ((ctty = controlling_tty(pi->pgrp<0)) < 0) return -1;
 	}
 
 	/* Check if this is a simple builtin (not part of a pipe).
@@ -1393,11 +1408,11 @@
 			 * and the pipe fd is available for dup'ing. */
 			setup_redirects(child,NULL);
 			
-			if (pi->followup!=PIPE_BG) {
+			if (interactive && pi->followup!=PIPE_BG) {
 				/* If we (the child) win the race, put ourselves in the process
 				 * group whose leader is the first process in this pipe. */
 				if (pi->pgrp < 0) {
-					pi->pgrp = child->pid;
+					pi->pgrp = getpid();
 				}
 				if (setpgid(0, pi->pgrp) == 0) {
 					signal(SIGTTOU, SIG_IGN);
@@ -1459,11 +1474,12 @@
 			if (interactive) {
 				/* move the new process group into the foreground */
 				/* suppress messages when run from /linuxrc mag at sysgo.de */
+				/* XXX probably this "0" should come from controlling_tty() */
 				if (tcsetpgrp(0, pi->pgrp) && errno != ENOTTY)
-					perror_msg("tcsetpgrp");
+					perror_msg("tcsetpgrp-3");
 				rcode = pipe_wait(pi);
 				if (tcsetpgrp(0, getpgrp()) && errno != ENOTTY)
-					perror_msg("tcsetpgrp");
+					perror_msg("tcsetpgrp-4");
 			} else {
 				rcode = pipe_wait(pi);
 			}
@@ -2500,6 +2516,25 @@
 	return rcode;
 }
 
+
+/* I think Erik wrote this.  It looks imperfect at best */
+void grab_tty_control(void)
+{
+	pid_t initialpgrp;
+	do {
+		initialpgrp = tcgetpgrp(fileno(stderr));
+		if (initialpgrp < 0) {
+			error_msg("sh: can't access tty; job control disabled\n");
+		}
+		if (initialpgrp == -1)
+			initialpgrp = getpgrp();
+		else if (initialpgrp != getpgrp()) {
+			killpg(initialpgrp, SIGTTIN);
+			continue;
+		}
+	} while (0);
+}
+
 int shell_main(int argc, char **argv)
 {
 	int opt;
@@ -2525,19 +2560,6 @@
 	/* If we get started under a job aware app (like bash 
 	 * for example), make sure we are now in charge so we 
 	 * don't fight over who gets the foreground */
-	do { 
-		pid_t initialpgrp;
-		initialpgrp = tcgetpgrp(fileno(stderr));
-		if (initialpgrp < 0) {
-			error_msg_and_die("sh: can't access tty; job control disabled\n");
-		}
-		if (initialpgrp == -1)
-			initialpgrp = getpgrp();
-		else if (initialpgrp != getpgrp()) {
-			killpg(initialpgrp, SIGTTIN);
-			continue;
-		}
-	} while (0);
 	/* don't pay any attention to this signal; it just confuses 
 	   things and isn't really meant for shells anyway */
 	signal(SIGTTOU, SIG_IGN);
@@ -2602,6 +2624,7 @@
 	if (interactive) {
 		/* Looks like they want an interactive shell */
 		fprintf(stdout, "\nhush -- the humble shell v0.01 (testing)\n\n");
+		grab_tty_control();
 		opt=parse_file_outer(stdin);
 		goto final_return;
 	}