[PATCH] fix Makefile to ensure proper options get passed from gcc

From: Jory A. Pratt
Date: Fri Aug 28 2009 - 09:26:43 EST

if -D__KERNEL__ is not passed via KBUILD_CFLAGS the compiler can have options passed by default that will unset
other options such as -ffreestanding or -fno-toplevel-reorder if the compiler is passing -fPIE.

refer to fix-fpie-from-being-used.diff

Another option that was suggested from another user was to pass -D__KERNEL__ via Kbuild.include, patch is also attached.
either patch would work, There is no risk of breakage, benefit is for those who use a hardened toolchain.


I believe we should pass the option via KBUILD_CFLAGS as to not confuse the fact that we are not building CPP code, but rather C code.

Also correct me if I am wrong but last I knew only part of kernel that was cpp was qconfig.

-Jory signed off by: Jory A. Pratt <anarchy@xxxxxxxxxx>

When -fPIE is pass to cc1 it can't use -ffreestanding or -fno-toplevel-reorder.
This will cause issues in video-vga.c when compiled leaving a user with no video
modes avaliable when booting system.
Many thanks to Vinky for tracking down bug.

--- Makefile~ 2009-08-27 21:38:59.809945943 -0500
+++ Makefile 2009-08-27 21:40:04.204922755 -0500
@@ -348,7 +348,8 @@
-fno-strict-aliasing -fno-common \
-Werror-implicit-function-declaration \
-Wno-format-security \
- -fno-delete-null-pointer-checks
+ -fno-delete-null-pointer-checks \
+ -D__KERNEL__

# Read KERNELRELEASE from include/config/kernel.release (if it exists)
2009-08-28 Magnus Granberg <zorry@xxxxxx>

* scripts/Kbuild.incude add $(KBUILD_CPPFLAGS)

--- scripts/Kbuild.include.zorry 2009-08-28 01:50:41.000000000 +0000
+++ scripts/Kbuild.include 2009-08-28 01:50:31.000000000 +0000
@@ -105,12 +105,12 @@
# Usage: cflags-y += $(call cc-option,-march=winchip-c6,-march=i586)

cc-option = $(call try-run,\
- $(CC) $(KBUILD_CFLAGS) $(1) -c -xc /dev/null -o "$$TMP",$(1),$(2))
+ $(CC) $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) $(1) -c -xc /dev/null -o "$$TMP",$(1),$(2))

# cc-option-yn
# Usage: flag := $(call cc-option-yn,-march=winchip-c6)
cc-option-yn = $(call try-run,\
- $(CC) $(KBUILD_CFLAGS) $(1) -c -xc /dev/null -o "$$TMP",y,n)
+ $(CC) $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) $(1) -c -xc /dev/null -o "$$TMP",y,n)

# cc-option-align
# Prefix align with either -falign or -malign