[ebtables PATCH 2/2] configure.ac: add option --enable-kernel-64-userland-32

[Thomas De Schampheleire <patrickdepinguin@gmail.com>]

From: Thomas De Schampheleire <thomas.de_schampheleire@nokia.com>

The ebtables build system seems to assume that 'sparc64' is the
only case where KERNEL_64_USERSPACE_32 is relevant, but this is not true.
This situation can happen on many architectures, especially in embedded
systems. For example, an Aarch64 processor with kernel in 64-bit but
userland built for 32-bit Arm. Or a 64-bit MIPS Octeon III processor, with
userland running in the 'n32' ABI.

While it is possible to set CFLAGS in the environment when calling the
configure script, the caller would need to know to not only specify
KERNEL_64_USERSPACE_32 but also the EBT_MIN_ALIGN value.

Instead, add a configure option. All internal details can then be handled by
the configure script.

Signed-off-by: Thomas De Schampheleire <thomas.de_schampheleire@nokia.com>
---
 configure.ac | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index c24ede3..3e89c0c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -15,10 +15,17 @@ AS_IF([test "x$LOCKFILE" = x], [LOCKFILE="/var/lib/ebtables/lock"])
 
 regular_CFLAGS="-Wall -Wunused"
 regular_CPPFLAGS=""
+
 case "$host" in
 	sparc64-*)
-		regular_CPPFLAGS="$regular_CPPFLAGS -DEBT_MIN_ALIGN=8 -DKERNEL_64_USERSPACE_32";;
+		enable_kernel_64_userland_32=yes ;;
 esac
+AC_ARG_ENABLE([kernel-64-userland-32],
+    AC_HELP_STRING([--enable-kernel-64-userland-32], [indicate that ebtables will be built as a 32-bit application but run under a 64-bit kernel])
+)
+AS_IF([test "x$enable_kernel_64_userland_32" = xyes],
+    [regular_CPPFLAGS="$regular_CPPFLAGS -DEBT_MIN_ALIGN=8 -DKERNEL_64_USERSPACE_32"]
+)
 
 AC_SUBST([regular_CFLAGS])
 AC_SUBST([regular_CPPFLAGS])
-- 
2.26.3