From 8ab1b8908bd9aecfbf048fb9683e9f89e3b10fe0 Mon Sep 17 00:00:00 2001
From: Michael Santos <michael.santos@gmail.com>
Date: Sat, 15 Nov 2014 10:17:46 -0500
Subject: [PATCH] Add pivot_root(2)

---
 c_src/alcove_call.proto |  1 +
 c_src/alcove_dir.c      | 40 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 41 insertions(+)

diff --git a/c_src/alcove_call.proto b/c_src/alcove_call.proto
index 82f37a7..11c57cb 100644
--- a/c_src/alcove_call.proto
+++ b/c_src/alcove_call.proto
@@ -33,6 +33,7 @@ mount/6
 mount_define/1
 open/3
 pid/0
+pivot_root/2
 prctl/5
 prctl_define/1
 read/2
diff --git a/c_src/alcove_dir.c b/c_src/alcove_dir.c
index 37baad6..8648666 100644
--- a/c_src/alcove_dir.c
+++ b/c_src/alcove_dir.c
@@ -18,6 +18,10 @@
 #include <sys/stat.h>
 #include <dirent.h>
 
+#ifdef __linux__
+#include <linux/unistd.h>
+#endif
+
 /*
  * chdir(2)
  *
@@ -124,6 +128,42 @@ alcove_sys_chroot(alcove_state_t *ap, const char *arg, size_t len,
         : alcove_mk_atom(reply, rlen, "ok");
 }
 
+/*
+ * pivot_root(2)
+ *
+ */
+    ssize_t
+alcove_sys_pivot_root(alcove_state_t *ap, const char *arg, size_t len,
+        char *reply, size_t rlen)
+{
+#ifdef __linux__
+    int index = 0;
+    char new_root[PATH_MAX] = {0};
+    char put_old[PATH_MAX] = {0};
+    size_t nlen = sizeof(new_root)-1;
+    size_t plen = sizeof(put_old)-1;
+    int rv = 0;
+
+    /* new_root */
+    if (alcove_decode_iolist(arg, len, &index, new_root, &nlen) < 0 ||
+            nlen == 0)
+        return -1;
+
+    /* put_old */
+    if (alcove_decode_iolist(arg, len, &index, put_old, &plen) < 0 ||
+            plen == 0)
+        return -1;
+
+    rv = syscall(__NR_pivot_root, new_root, put_old);
+
+    return (rv < 0)
+        ? alcove_mk_errno(reply, rlen, errno)
+        : alcove_mk_atom(reply, rlen, "ok");
+#else
+    return alcove_mk_error(reply, rlen, "unsupported");
+#endif
+}
+
 /*
  * getcwd(3)
  *