From 43de12db5565371b6abc29e1205dfc64c55d6616 Mon Sep 17 00:00:00 2001
From: Justine Tunney <jtunney@gmail.com>
Date: Tue, 28 Nov 2023 18:52:14 -0800
Subject: [PATCH] Introduce forkpty()

---
 libc/BUILD.mk              |  1 +
 libc/isystem/pty.h         |  7 +++
 third_party/musl/BUILD.mk  |  4 +-
 third_party/musl/forkpty.c | 92 ++++++++++++++++++++++++++++++++++++++
 4 files changed, 103 insertions(+), 1 deletion(-)
 create mode 100644 libc/isystem/pty.h
 create mode 100644 third_party/musl/forkpty.c

diff --git a/libc/BUILD.mk b/libc/BUILD.mk
index e28e59a3b..39e757e60 100644
--- a/libc/BUILD.mk
+++ b/libc/BUILD.mk
@@ -147,6 +147,7 @@ libc/isystem/pmmintrin.h \
 libc/isystem/poll.h \
 libc/isystem/popcntintrin.h \
 libc/isystem/pthread.h \
+libc/isystem/pty.h \
 libc/isystem/pwd.h \
 libc/isystem/queue \
 libc/isystem/random \
diff --git a/libc/isystem/pty.h b/libc/isystem/pty.h
new file mode 100644
index 000000000..2c54aaa0b
--- /dev/null
+++ b/libc/isystem/pty.h
@@ -0,0 +1,7 @@
+#ifndef _PTY_H
+#define _PTY_H
+#include "libc/calls/termios.h"
+#include "libc/calls/weirdtypes.h"
+#include "libc/sysv/consts/baud.internal.h"
+#include "libc/sysv/consts/termios.h"
+#endif /* _PTY_H */
diff --git a/third_party/musl/BUILD.mk b/third_party/musl/BUILD.mk
index 7ccca7cbc..f87046f25 100644
--- a/third_party/musl/BUILD.mk
+++ b/third_party/musl/BUILD.mk
@@ -18,14 +18,16 @@ THIRD_PARTY_MUSL_A_OBJS =				\
 
 THIRD_PARTY_MUSL_A_DIRECTDEPS =				\
 	LIBC_CALLS					\
-	LIBC_INTRIN					\
 	LIBC_FMT					\
+	LIBC_INTRIN					\
 	LIBC_MEM					\
 	LIBC_NEXGEN32E					\
+	LIBC_PROC					\
 	LIBC_RUNTIME					\
 	LIBC_STDIO					\
 	LIBC_STR					\
 	LIBC_SYSV					\
+	LIBC_THREAD					\
 	THIRD_PARTY_ZLIB
 
 THIRD_PARTY_MUSL_A_DEPS :=				\
diff --git a/third_party/musl/forkpty.c b/third_party/musl/forkpty.c
new file mode 100644
index 000000000..e2cc92eb3
--- /dev/null
+++ b/third_party/musl/forkpty.c
@@ -0,0 +1,92 @@
+/*-*- mode:c;indent-tabs-mode:t;c-basic-offset:8;tab-width:8;coding:utf-8   -*-│
+│vi: set et ft=c ts=8 tw=8 fenc=utf-8                                       :vi│
+╚──────────────────────────────────────────────────────────────────────────────╝
+│                                                                              │
+│  Musl Libc                                                                   │
+│  Copyright © 2005-2014 Rich Felker, et al.                                   │
+│                                                                              │
+│  Permission is hereby granted, free of charge, to any person obtaining       │
+│  a copy of this software and associated documentation files (the             │
+│  "Software"), to deal in the Software without restriction, including         │
+│  without limitation the rights to use, copy, modify, merge, publish,         │
+│  distribute, sublicense, and/or sell copies of the Software, and to          │
+│  permit persons to whom the Software is furnished to do so, subject to       │
+│  the following conditions:                                                   │
+│                                                                              │
+│  The above copyright notice and this permission notice shall be              │
+│  included in all copies or substantial portions of the Software.             │
+│                                                                              │
+│  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,             │
+│  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF          │
+│  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.      │
+│  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY        │
+│  CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,        │
+│  TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE           │
+│  SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                      │
+│                                                                              │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/weirdtypes.h"
+#include "libc/calls/struct/sigset.h"
+#include "libc/sysv/consts/sig.h"
+#include "libc/calls/struct/sigset.h"
+#include "libc/thread/thread.h"
+#include "libc/calls/calls.h"
+#include "libc/sysv/consts/o.h"
+#include "libc/runtime/runtime.h"
+#include "libc/errno.h"
+#include "libc/calls/termios.h"
+
+asm(".ident\t\"\\n\\n\
+Musl libc (MIT License)\\n\
+Copyright 2005-2014 Rich Felker, et. al.\"");
+asm(".include \"libc/disclaimer.inc\"");
+
+int forkpty(int *pm, char *name, const struct termios *tio, const struct winsize *ws)
+{
+	int m, s, ec=0, p[2], cs;
+	pid_t pid=-1;
+	sigset_t set, oldset;
+
+	if (openpty(&m, &s, name, tio, ws) < 0) return -1;
+
+	sigfillset(&set);
+	pthread_sigmask(SIG_BLOCK, &set, &oldset);
+	pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
+
+	if (pipe2(p, O_CLOEXEC)) {
+		close(s);
+		goto out;
+	}
+
+	pid = fork();
+	if (!pid) {
+		close(m);
+		close(p[0]);
+		if (login_tty(s)) {
+			write(p[1], &errno, sizeof errno);
+			_exit(127);
+		}
+		close(p[1]);
+		pthread_setcancelstate(cs, 0);
+		pthread_sigmask(SIG_SETMASK, &oldset, 0);
+		return 0;
+	}
+	close(s);
+	close(p[1]);
+	if (read(p[0], &ec, sizeof ec) > 0) {
+		int status;
+		waitpid(pid, &status, 0);
+		pid = -1;
+		errno = ec;
+	}
+	close(p[0]);
+
+out:
+	if (pid > 0) *pm = m;
+	else close(m);
+
+	pthread_setcancelstate(cs, 0);
+	pthread_sigmask(SIG_SETMASK, &oldset, 0);
+
+	return pid;
+}