build-sys: Add setns() functions if not in the C library.

Debian Stable is still using glibc 2.13, which doesn't provide the setns().
So we detect this and provide a tiny wrapper that issues the setns syscall
towards the kernel.

1 files changed, 17 insertions, 0 deletions

diff --git a/src/shared/missing.h b/src/shared/missing.h
index 2661285a22..3142306e35 100644
--- a/src/shared/missing.h
+++ b/src/shared/missing.h
@@ -28,6 +28,7 @@
 #include <fcntl.h>
 #include <stdlib.h>
 #include <unistd.h>
+#include <errno.h>
 #include <linux/oom.h>
 #include <linux/input.h>
 #include <linux/if_link.h>
@@ -353,3 +354,19 @@ static inline int name_to_handle_at(int fd, const char *name, struct file_handle
 #endif
 
 #endif
+
+#ifndef __NR_setns
+#  if defined(__x86_64__)
+#    define __NR_setns 308
+#  elif defined(__i386__)
+#    define __NR_setns 346
+#  else
+#    error "__NR_setns is not defined"
+#  endif
+#endif
+
+#if !HAVE_DECL_SETNS
+static inline int setns(int fd, int nstype) {
+        return syscall(__NR_setns, fd, nstype);
+}
+#endif