Add nommu-able xvdaemon() and use it to remove some TOYBOX_FORK dependencies

2 files changed, 26 insertions, 1 deletions

diff --git a/lib/lib.h b/lib/lib.h
index 6851c4aa..192fb7d2 100644
--- a/lib/lib.h
+++ b/lib/lib.h
@@ -127,12 +127,13 @@ char *xstrndup(char *s, size_t n);
 char *xstrdup(char *s);
 void *xmemdup(void *s, long len);
 char *xmprintf(char *format, ...) printf_format;
+void xflush(int flush);
 void xprintf(char *format, ...) printf_format;
 void xputsl(char *s, int len);
 void xputsn(char *s);
 void xputs(char *s);
 void xputc(char c);
-void xflush(int flush);
+void xvdaemon(void);
 void xexec(char **argv);
 pid_t xpopen_setup(char **argv, int *pipes, void (*callback)(char **argv));
 pid_t xpopen_both(char **argv, int *pipes);
diff --git a/lib/xwrap.c b/lib/xwrap.c
index cf7fc42a..85fa2405 100644
--- a/lib/xwrap.c
+++ b/lib/xwrap.c
@@ -182,6 +182,30 @@ void xputc(char c)
   xflush(0);
 }
 
+// daemonize via vfork(). Does not chdir("/"), caller should do that first
+// note: restarts process from command_main()
+void xvdaemon(void)
+{
+  int fd;
+
+  // vfork and exec /proc/self/exe
+  if (toys.stacktop) {
+    xpopen(0, 0, 0);
+    _exit(0);
+  }
+
+  // new session id, point fd 0-2 at /dev/null, detach from tty
+  setsid();
+  close(0);
+  xopen_stdio("/dev/null", O_RDWR);
+  dup2(0, 1);
+  if (-1 != (fd = open("/dev/tty", O_RDONLY))) {
+    ioctl(fd, TIOCNOTTY);
+    close(fd);
+  }
+  dup2(0, 2);
+}
+
 // This is called through the XVFORK macro because parent/child of vfork
 // share a stack, so child returning from a function would stomp the return
 // address parent would need. Solution: make vfork() an argument so processes