x32: Warn and disable rather than error if binutils too old

If X32 is enabled in .config, but the binutils can't build it, issue a
warning and disable the feature rather than erroring out.

In order to support this, have CONFIG_X86_X32 be the option set in
Kconfig, and CONFIG_X86_X32_ABI be the option set by the Makefile when
it is enabled and binutils has been found to be functional.

Requested-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Cc: H. J. Lu <hjl.tools@gmail.com>
Link: http://lkml.kernel.org/r/1329696488-16970-1-git-send-email-hpa@zytor.com

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index c9d6c9e..e2b38b4 100644 (file)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2175,7 +2175,7 @@ config IA32_AOUT
        ---help---
          Support old a.out binaries in the 32bit emulation.
 
-config X86_X32_ABI
+config X86_X32
        bool "x32 ABI for 64-bit mode (EXPERIMENTAL)"
        depends on X86_64 && IA32_EMULATION && EXPERIMENTAL
        ---help---
@@ -2190,7 +2190,7 @@ config X86_X32_ABI
 
 config COMPAT
        def_bool y
-       depends on IA32_EMULATION || X86_X32_ABI
+       depends on IA32_EMULATION || X86_X32
 
 config COMPAT_FOR_U64_ALIGNMENT
        def_bool COMPAT

diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 209ba12..31bb1eb 100644 (file)
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -82,6 +82,22 @@ ifdef CONFIG_CC_STACKPROTECTOR
         endif
 endif
 
+ifdef CONFIG_X86_X32
+       x32_ld_ok := $(call try-run,\
+                       /bin/echo -e '1: .quad 1b' | \
+                       $(CC) $(KBUILD_AFLAGS) -c -xassembler -o "$$TMP" - && \
+                       $(OBJCOPY) -O elf32-x86-64 "$$TMP" "$$TMPO" && \
+                       $(LD) -m elf32_x86_64 "$$TMPO" -o "$$TMP",y,n)
+       ifeq ($(x32_ld_ok),y)
+               CONFIG_X86_X32_ABI := y
+               KBUILD_AFLAGS += -DCONFIG_X86_X32_ABI
+               KBUILD_CFLAGS += -DCONFIG_X86_X32_ABI
+       else
+               $(warning CONFIG_X86_X32 enabled but no binutils support)
+       endif
+endif
+export CONFIG_X86_X32_ABI
+
 # Don't unroll struct assignments with kmemcheck enabled
 ifeq ($(CONFIG_KMEMCHECK),y)
        KBUILD_CFLAGS += $(call cc-option,-fno-builtin-memcpy)