libc: Add login_tty() and forkpty()

libc/CMakeLists.txt

@@ -26,6 +26,7 @@ set(SOURCES
     src/strtod.cpp
     src/math.cpp
     src/pty.cpp
+    src/utmp.cpp
     src/sys/stat.cpp
     src/sys/mman.cpp
     src/sys/wait.cpp

libc/include/pty.h

@@ -14,6 +14,9 @@ extern "C"
     /* 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);
 
+    /* Create a new process operating in a pseudoterminal. */
+    pid_t forkpty(int* master, char* name, const struct termios* term, const struct winsize* win);
+
 #ifdef __cplusplus
 }
 #endif

libc/include/utmp.h

@@ -0,0 +1,18 @@
+/* utmp.h: Write entries to utmp files. */
+
+#ifndef _UTMP_H
+#define _UTMP_H
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+    /* Prepare a new terminal session on a tty. */
+    int login_tty(int fd);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif

libc/src/pty.cpp

@@ -5,6 +5,7 @@
 #include <string.h>
 #include <termios.h>
 #include <unistd.h>
+#include <utmp.h>
 
 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
 
@@ -44,4 +45,27 @@ extern "C"
 
         return 0;
     }
+
+    pid_t forkpty(int* master, char* name, const struct termios* term, const struct winsize* win)
+    {
+        int slave;
+        if (openpty(master, &slave, name, term, win) < 0) return -1;
+
+        pid_t child = fork();
+        if (child < 0)
+        {
+            close(*master);
+            close(slave);
+            return -1;
+        }
+        if (!child)
+        {
+            close(*master);
+            login_tty(slave);
+        }
+        else
+            close(slave);
+
+        return child;
+    }
 }

libc/src/utmp.cpp

@@ -0,0 +1,22 @@
+#include <sys/ioctl.h>
+#include <termios.h>
+#include <unistd.h>
+#include <utmp.h>
+
+extern "C"
+{
+    int login_tty(int fd)
+    {
+        setsid();
+
+        if (ioctl(fd, TIOCSCTTY) < 0) return -1;
+
+        dup2(fd, STDIN_FILENO);
+        dup2(fd, STDOUT_FILENO);
+        dup2(fd, STDERR_FILENO);
+
+        close(fd);
+
+        return 0;
+    }
+}