From a47321a2286259bf90b707edc8c45c3bb2ddaa84 Mon Sep 17 00:00:00 2001
From: apio <blobs.trading@gmail.com>
Date: Fri, 22 Sep 2023 23:02:33 +0200
Subject: [PATCH] libc: Implement openpty()

---
 libc/CMakeLists.txt         |  1 +
 libc/include/pty.h          | 21 +++++++++++++++++
 libc/src/pty.cpp            | 47 +++++++++++++++++++++++++++++++++++++
 terminal/TerminalWidget.cpp | 27 +++++++++++----------
 4 files changed, 84 insertions(+), 12 deletions(-)
 create mode 100644 libc/include/pty.h
 create mode 100644 libc/src/pty.cpp

diff --git a/libc/CMakeLists.txt b/libc/CMakeLists.txt
index e2eaceea..47d8c8d6 100644
--- a/libc/CMakeLists.txt
+++ b/libc/CMakeLists.txt
@@ -25,6 +25,7 @@ set(SOURCES
     src/utime.cpp
     src/strtod.cpp
     src/math.cpp
+    src/pty.cpp
     src/sys/stat.cpp
     src/sys/mman.cpp
     src/sys/wait.cpp
diff --git a/libc/include/pty.h b/libc/include/pty.h
new file mode 100644
index 00000000..22afbb97
--- /dev/null
+++ b/libc/include/pty.h
@@ -0,0 +1,21 @@
+/* pty.h: Pseudoterminal handling functions. */
+
+#ifndef _PTY_H
+#define _PTY_H
+
+#include <bits/termios.h>
+#include <sys/types.h>
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+    /* Find an available pseudoterminal pair and initialize it, returning file descriptors for both sides. */
+    int openpty(int* master, int* slave, char* name, const struct termios* term, const struct winsize* win);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
diff --git a/libc/src/pty.cpp b/libc/src/pty.cpp
new file mode 100644
index 00000000..879a772b
--- /dev/null
+++ b/libc/src/pty.cpp
@@ -0,0 +1,47 @@
+#include <fcntl.h>
+#include <pty.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <termios.h>
+#include <unistd.h>
+
+#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
+
+extern "C"
+{
+    int openpty(int* master, int* slave, char* name, const struct termios* term, const struct winsize* win)
+    {
+        *master = posix_openpt(O_RDWR);
+        if (*master < 0) return -1;
+
+        // No-ops on Luna, and since this is the Luna libc, we can skip error handling.
+        grantpt(*master);
+        unlockpt(*master);
+
+        char* pname = ptsname(*master);
+        if (!pname)
+        {
+            close(*master);
+            return -1;
+        }
+
+        if (name)
+        {
+            fputs("warning: openpty() called with non-null name, this is insecure\n", stderr);
+            strcpy(name, pname);
+        }
+
+        *slave = open(pname, O_RDWR);
+        if (*slave < 0)
+        {
+            close(*master);
+            return -1;
+        }
+
+        if (term) tcsetattr(*slave, TCSANOW, term);
+        if (win) fputs("warning: openpty() called with non-null window size, this is not supported yet\n", stderr);
+
+        return 0;
+    }
+}
diff --git a/terminal/TerminalWidget.cpp b/terminal/TerminalWidget.cpp
index 703ecbf2..76e93262 100644
--- a/terminal/TerminalWidget.cpp
+++ b/terminal/TerminalWidget.cpp
@@ -4,6 +4,7 @@
 #include <luna/CType.h>
 #include <os/File.h>
 #include <os/Process.h>
+#include <pty.h>
 #include <signal.h>
 #include <stdlib.h>
 #include <time.h>
@@ -51,33 +52,35 @@ Result<void> TerminalWidget::init(char* const* args)
 
     signal(SIGCHLD, sigchld_handler);
 
-    int fd = posix_openpt(O_RDWR | O_CLOEXEC);
-    if (fd < 0) return err(errno);
+    int master;
+    int slave;
 
-    grantpt(fd);
-    unlockpt(fd);
+    int result = openpty(&master, &slave, nullptr, nullptr, nullptr);
+    if (result < 0) return err(errno);
 
     pid_t child = TRY(os::Process::fork());
     if (child == 0)
     {
-        int ptsfd = open(ptsname(fd), O_RDWR);
+        close(master);
 
-        dup2(ptsfd, STDIN_FILENO);
-        dup2(ptsfd, STDOUT_FILENO);
-        dup2(ptsfd, STDERR_FILENO);
+        dup2(slave, STDIN_FILENO);
+        dup2(slave, STDOUT_FILENO);
+        dup2(slave, STDERR_FILENO);
 
         setpgid(0, 0);
-        tcsetpgrp(ptsfd, getpid());
+        tcsetpgrp(slave, getpid());
 
-        close(ptsfd);
+        close(slave);
 
         execv(args[0], args);
         _exit(127);
     }
 
-    m_pty = fd;
+    close(slave);
 
-    fcntl(fd, F_SETFL, O_NONBLOCK);
+    m_pty = master;
+
+    fcntl(master, F_SETFL, O_NONBLOCK);
 
     m_child_pid = child;