From fc09d398954ab5f658a7fc73ea730d7510e3bc93 Mon Sep 17 00:00:00 2001
From: Matheus <matheusuky@gmail.com>
Date: Wed, 28 Aug 2024 20:26:43 -0300
Subject: [PATCH] jobctl: allow tty stealing

---
 kernel-src/include/kernel/jobctl.h |  2 +-
 kernel-src/io/tty.c                | 15 ++------
 kernel-src/sys/jobctl.c            | 55 +++++++++++++++++++-----------
 3 files changed, 38 insertions(+), 34 deletions(-)

diff --git a/kernel-src/include/kernel/jobctl.h b/kernel-src/include/kernel/jobctl.h
index be9eb935..6e53ac73 100644
--- a/kernel-src/include/kernel/jobctl.h
+++ b/kernel-src/include/kernel/jobctl.h
@@ -11,7 +11,7 @@ void jobctl_addproc(proc_t *parent, proc_t *proc);
 void jobctl_procremove(proc_t *proc);
 pid_t jobctl_getpgid(proc_t *proc);
 pid_t jobctl_getsid(proc_t *proc);
-void jobctl_setctty(proc_t *proc, void *ctty);
+int jobctl_setctty(proc_t *proc, void *ctty, bool steal);
 void *jobctl_getctty(proc_t *proc);
 int jobctl_signal(proc_t *proc, int signal);
 proc_t *jobctl_getforeground(proc_t *proc);
diff --git a/kernel-src/io/tty.c b/kernel-src/io/tty.c
index fb576733..953409fc 100644
--- a/kernel-src/io/tty.c
+++ b/kernel-src/io/tty.c
@@ -320,19 +320,8 @@ int tty_ioctl(tty_t *tty, unsigned long req, void *arg, int *result) {
 		case TCSETS:
 			return USERCOPY_POSSIBLY_FROM_USER(&tty->termios, arg, sizeof(termios_t));
 		case TIOCSCTTY: {
-			if (arg) {
-				int steal;
-				int e = USERCOPY_POSSIBLY_FROM_USER(&steal, arg, sizeof(int));
-				if (e)
-					return e;
-
-				if (steal == 1) {
-					printf("tty: stealing not supported\n");
-					return EINVAL;
-				}
-			}
 			// set as controlling tty
-			jobctl_setctty(_cpu()->thread->proc, tty);
+			return jobctl_setctty(_cpu()->thread->proc, tty, (uintptr_t)arg == 1);
 			break;
 		}
 		case TIOCGPGRP: {
@@ -399,7 +388,7 @@ static int open(int minor, vnode_t **vnode, int flags) {
 		return ENODEV;
 	} else if ((flags & V_FFLAGS_NOCTTY) == 0) {
 		// set as controlling tty
-		jobctl_setctty(_cpu()->thread->proc, tty);
+		jobctl_setctty(_cpu()->thread->proc, tty, false);
 	}
 
 	return 0;
diff --git a/kernel-src/sys/jobctl.c b/kernel-src/sys/jobctl.c
index 2f691b09..3af0872f 100644
--- a/kernel-src/sys/jobctl.c
+++ b/kernel-src/sys/jobctl.c
@@ -33,9 +33,9 @@ static void removefromlist(proc_t *pgrp, proc_t *proc) {
 	spinlock_release(&pgrp->pgrp.lock);
 }
 
-void jobctl_setctty(proc_t *proc, void *_ctty) {
+int jobctl_setctty(proc_t *proc, void *_ctty, bool steal) {
 	tty_t *tty = _ctty;
-
+	int error = 0;
 	bool intstatus = interrupt_set(false);
 	spinlock_acquire(&proc->jobctllock);
 
@@ -45,21 +45,38 @@ void jobctl_setctty(proc_t *proc, void *_ctty) {
 	if (proc->session.leader)
 		goto leave;
 
-	if (tty == NULL && proc->session.controllingtty) {
-		unholdtty = proc->session.controllingtty;
-		proc->session.controllingtty = NULL;
-		spinlock_acquire(&unholdtty->sessionlock);
-		unholdtty->session = NULL;
-		spinlock_release(&unholdtty->sessionlock);
+	tty_t *checktty = proc->session.controllingtty;
+	if (tty == NULL && checktty) {
+		if (checktty)
+			spinlock_acquire(&checktty->sessionlock);
+
+		// check if it was stolen
+		if (checktty->session == proc) {
+			// not stolen, unset it
+			// TODO SIGHUP and SIGCONT to foregroup group
+			unholdtty = checktty;
+			proc->session.controllingtty = NULL;
+			checktty->session = NULL;
+		}
+
+		spinlock_release(&checktty->sessionlock);
 	}
 
 	if (tty && proc->session.controllingtty == NULL) {
 		spinlock_acquire(&tty->sessionlock);
+
 		if (tty->session == NULL) {
 			VOP_HOLD(tty->mastervnode);
 			proc->session.controllingtty = tty;
 			tty->session = proc;
+		} else if (steal) {
+			// vnode reference gets transferred over to the new proc
+			tty->session->session.controllingtty = NULL;
+			tty->session = proc;
+		} else {
+			error = EPERM;
 		}
+
 		spinlock_release(&tty->sessionlock);
 	}
 
@@ -70,6 +87,8 @@ void jobctl_setctty(proc_t *proc, void *_ctty) {
 	if (unholdtty) {
 		VOP_RELEASE(unholdtty->mastervnode);
 	}
+
+	return error;
 }
 
 void *jobctl_getctty(proc_t *proc) {
@@ -77,23 +96,19 @@ void *jobctl_getctty(proc_t *proc) {
 
 	bool intstatus = interrupt_set(false);
 	spinlock_acquire(&proc->jobctllock);
+	proc_t *session = proc->session.leader ? proc->session.leader : proc;
 
-	if (proc->session.leader) {
-		proc_t *session = proc->session.leader;
+	if (session != proc)
 		spinlock_acquire(&session->jobctllock);
 
-		tty = session->session.controllingtty;
-		if (tty) {
-			VOP_HOLD(tty->mastervnode);
-		}
-
-		spinlock_release(&session->jobctllock);
-	} else if (proc->session.controllingtty){
-		// is the session leader
-		tty = proc->session.controllingtty;
+	tty = session->session.controllingtty;
+	if (tty) {
 		VOP_HOLD(tty->mastervnode);
 	}
 
+	if (session != proc)
+		spinlock_release(&session->jobctllock);
+
 	spinlock_release(&proc->jobctllock);
 	interrupt_set(intstatus);
 	return tty;
@@ -262,7 +277,7 @@ void jobctl_detach(proc_t *proc) {
 	if (unholdsession) {
 		PROC_RELEASE(unholdsession);
 	} else {
-		jobctl_setctty(proc, NULL);
+		jobctl_setctty(proc, NULL, 0);
 		jobctl_signal(foreground, SIGHUP);
 		jobctl_signal(foreground, SIGCONT);
 		PROC_RELEASE(foreground);