MT#4463 Fake uname syscall so Virtualbox Guest Addition installation works

Virtualbox Guest Addition installation fails inside chroot
with different kernel version of live system vs installed one.
Sadly there doesn't seem to be a way to reliably control kernel
version/header location forVBoxLinuxAdditions.run (e.g. via
KERN_DIR=... as advertised) because there are several calls
to `uname -r` in use. :(

deployment.sh

@@ -1590,6 +1590,61 @@ EOF
 
 }
 
+fake_uname() {
+   cat > "${TARGET}/tmp/uname.c" << EOF
+#include <stdio.h>
+#include <string.h>
+#include <dlfcn.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <sys/syslog.h>
+#include <sys/utsname.h>
+
+#ifndef UTS_RELEASE
+#define UTS_RELEASE "0.0.0"
+#endif
+
+#ifndef RTLD_NEXT
+#define RTLD_NEXT      ((void *) -1l)
+#endif
+
+typedef int (*uname_t) (struct utsname * buf);
+
+static void *get_libc_func(const char *funcname)
+{
+  void *func;
+  char *error;
+
+  func = dlsym(RTLD_NEXT, funcname);
+  if ((error = dlerror()) != NULL) {
+    fprintf(stderr, "Can't locate libc function \`%s' error: %s", funcname, error);
+    _exit(EXIT_FAILURE);
+  }
+  return func;
+}
+
+int uname(struct utsname *buf)
+{
+  int ret;
+  char *env = NULL;
+  uname_t real_uname = (uname_t) get_libc_func("uname");
+
+  ret = real_uname((struct utsname *) buf);
+  strncpy(buf->release, ((env = getenv("UTS_RELEASE")) == NULL) ? UTS_RELEASE : env, 65);
+  return ret;
+}
+EOF
+
+  grml-chroot "$TARGET" gcc -shared -fPIC -ldl /tmp/uname.c -o /tmp/fake-uname.so || die 'Failed to build fake-uname.so'
+
+  # avoid "ERROR: ld.so: object '/tmp/fake-uname.so' from LD_PRELOAD cannot be preloaded: ignored."
+  # messages caused by the host system when running grml-chroot process
+  cp "$TARGET"/tmp/fake-uname.so /tmp/fake-uname.so
+}
+
 vagrant_configuration() {
   # bzip2, linux-headers-amd64 and make are required for VirtualBox Guest Additions installer
   # less + sudo are required for Vagrant itself
@@ -1656,10 +1711,23 @@ vagrant_configuration() {
     echo "TIP:   Make sure to have virtualbox-guest-additions-iso installed."
   fi
 
+  # required for fake_uname and VBoxLinuxAdditions.run
+  grml-chroot $TARGET apt-get -y install gcc
+  fake_uname
+
+  KERNELHEADERS=$(basename $(ls -d ${TARGET}/usr/src/linux-headers*amd64 | sort -u | head -1))
+  if [ -z "$KERNELHEADERS" ] ; then
+    die "Error: no kernel headers found for building the ngcp-mediaproxy-ng kernel module."
+  fi
+  KERNELVERSION=${KERNELHEADERS##linux-headers-}
+  if [ -z "$KERNELVERSION" ] ; then
+    die "Error: no kernel version could be identified."
+  fi
+
   mkdir -p "${TARGET}/media/cdrom"
   mountpoint "${TARGET}/media/cdrom" >/dev/null && umount "${TARGET}/media/cdrom"
   mount -t iso9660 $isofile "${TARGET}/media/cdrom/"
-  grml-chroot "$TARGET" /media/cdrom/VBoxLinuxAdditions.run --nox11
+  UTS_RELEASE=$KERNELVERSION LD_PRELOAD=/tmp/fake-uname.so grml-chroot "$TARGET" /media/cdrom/VBoxLinuxAdditions.run --nox11
   tail -10 "${TARGET}/var/log/VBoxGuestAdditions.log"
   umount "${TARGET}/media/cdrom/"