[PATCH] uml: allow building as 32-bit binary on 64bit host

This patch makes the command:

make ARCH=um SUBARCH=i386

work on x86_64 hosts (with support for building 32-bit binaries).  This is
especially needed since 64-bit UMLs don't support 32-bit emulation for guest
binaries, currently.  This has been tested in all possible cases and works.

Only exception is that I've built but not tested a 64-bit binary, because I
hadn't a 64-bit filesystem available.

Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Cc: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/arch/um/Makefile-x86_64 b/arch/um/Makefile-x86_64
index d80bd0052e6b..aa2f7174ebca 100644
--- a/arch/um/Makefile-x86_64
+++ b/arch/um/Makefile-x86_64
@@ -1,11 +1,13 @@
 # Copyright 2003 - 2004 Pathscale, Inc
 # Released under the GPL
 
-SUBARCH_LIBS := arch/um/sys-x86_64/
+libs-y += arch/um/sys-x86_64/
 START := 0x60000000
 
+#We #undef __x86_64__ for kernelspace, not for userspace where
+#it's needed for headers to work!
 CFLAGS += -U__$(SUBARCH)__ -fno-builtin $(STUB_CFLAGS)
-ARCH_USER_CFLAGS := -D__x86_64__
+USER_CFLAGS += -fno-builtin
 
 ELF_ARCH := i386:x86-64
 ELF_FORMAT := elf64-x86-64