1 files changed, 54 insertions, 0 deletions
diff --git a/src/state/s6-linux-init-single.c b/src/state/s6-linux-init-single.c
new file mode 100644
index 0000000..4f23340
--- /dev/null
+++ b/src/state/s6-linux-init-single.c
@@ -0,0 +1,54 @@
+/* ISC license. */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+#include <skalibs/allreadwrite.h>
+#include <skalibs/strerr2.h>
+#include <skalibs/djbunix.h>
+
+#include "initctl.h"
+
+#define USAGE "s6-linux-init-single"
+#define dieusage() strerr_dieusage(100, USAGE)
+
+#define BANNER "Executing interactive root shell.\n"
+
+int main (void)
+{
+  int fd ;
+  PROG = "s6-linux-init-single" ;
+  fd = open(EARLYGETTY, O_RDONLY) ;
+  if (fd == -1)
+  {
+    if (errno != ENOENT)
+      strerr_diefu2sys(111, "opendir ", EARLYGETTY) ;
+    goto shell ;
+  }
+  if (faccessat(fd, "down", F_OK, 0) == 0)
+  {
+    fd_close(fd) ;
+    goto shell ;
+  }
+  if (errno != ENOENT)
+    strerr_diefu3sys(111, "access ", EARLYGETTY, "/down") ;
+  return 0 ;
+
+ shell:
+
+  fd = open("/dev/console", O_RDONLY) ;
+  if (fd == -1) strerr_diefu2sys(111, "open /dev/console for ", "reading") ;
+  if (fd_move(0, fd) == -1) strerr_diefu1sys(111, "move /dev/console fd to 0") ;
+  fd = open("/dev/console", O_WRONLY) ;
+  if (fd == -1) strerr_diefu2sys(111, "open /dev/console for ", "writing") ;
+  if (fd_move(1, fd) == -1) strerr_diefu1sys(111, "move /dev/console fd to 1") ;
+  if (fd_copy(2, 1) == -1) strerr_diefu1sys(111, "dup2 1 to 2") ;
+  if (allwrite(1, BANNER, sizeof(BANNER) - 1) < sizeof(BANNER) - 1)
+    strerr_diefu1sys(111, "write banner") ;
+  {
+    char *argv[3] = { "/bin/sh", "-i", 0 } ;
+    execv(argv[0], argv) ;
+    strerr_dieexec(111, argv[0]) ;
+  }
+}