[PATCH] x86_64: Allow compilation on a 32bit biarch toolchain

This might help on distributions that use a 32bit biarch compiler.

First pass -m64 by default.

Secondly add some more .code32s because at least the Ubuntu biarch
32bit as called by gcc doesn't seem to handle -m64 -m32 as generated
by the Makefile without such assistance.

And finally make sure the linker script can be preprocessed
with a 32bit cpp.

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/x86_64/Makefile

@@ -31,6 +31,7 @@ cflags-$(CONFIG_MK8) += $(call cc-option,-march=k8)
 cflags-$(CONFIG_MPSC) += $(call cc-option,-march=nocona)
 CFLAGS += $(cflags-y)
 
+CFLAGS += -m64
 CFLAGS += -mno-red-zone
 CFLAGS += -mcmodel=kernel
 CFLAGS += -pipe
@@ -52,6 +53,8 @@ CFLAGS += $(call cc-option,-funit-at-a-time)
 # prevent gcc from generating any FP code by mistake
 CFLAGS += $(call cc-option,-mno-sse -mno-mmx -mno-sse2 -mno-3dnow,)
 
+AFLAGS += -m64
+
 head-y := arch/x86_64/kernel/head.o arch/x86_64/kernel/head64.o arch/x86_64/kernel/init_task.o
 
 libs-y 					+= arch/x86_64/lib/

arch/x86_64/ia32/vsyscall-sigreturn.S

@@ -7,6 +7,7 @@
  * by doing ".balign 32" must match in both versions of the page.
  */
 
+	.code32
 	.section .text.sigreturn,"ax"
 	.balign 32
 	.globl __kernel_sigreturn

arch/x86_64/ia32/vsyscall-syscall.S

@@ -6,6 +6,7 @@
 #include <asm/asm-offsets.h>
 #include <asm/segment.h>
 
+	.code32
 	.text
 	.section .text.vsyscall,"ax"
 	.globl __kernel_vsyscall

arch/x86_64/ia32/vsyscall-sysenter.S

@@ -5,6 +5,7 @@
 #include <asm/ia32_unistd.h>
 #include <asm/asm-offsets.h>
 
+	.code32
 	.text
 	.section .text.vsyscall,"ax"
 	.globl __kernel_vsyscall

arch/x86_64/kernel/vmlinux.lds.S

@@ -8,6 +8,8 @@
 #include <asm/page.h>
 #include <linux/config.h>
 
+#undef i386	/* in case the preprocessor is a 32bit one */
+
 OUTPUT_FORMAT("elf64-x86-64", "elf64-x86-64", "elf64-x86-64")
 OUTPUT_ARCH(i386:x86-64)
 ENTRY(phys_startup_64)