Commit fcee7d4b authored by Borislav Petkov's avatar Borislav Petkov Committed by Ben Hutchings

kbuild: Steal gcc's pie from the very beginning

commit c6a38553 upstream.

So Sebastian turned off the PIE for kernel builds but that was too late
- Kbuild.include already uses KBUILD_CFLAGS and trying to disable gcc
options with, say cc-disable-warning, fails:

  gcc -D__KERNEL__ -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs
  ...
  -Wno-sign-compare -fno-asynchronous-unwind-tables -Wframe-address -c -x c /dev/null -o .31392.tmp
  /dev/null:1:0: error: code model kernel does not support PIC mode

because that returns an error and we can't disable the warning. For
example in this case:

KBUILD_CFLAGS   += $(call cc-disable-warning,frame-address,)

which leads to gcc issuing all those warnings again.

So let's turn off PIE/PIC at the earliest possible moment, when we
declare KBUILD_CFLAGS so that cc-disable-warning picks it up too.

Also, we need the $(call cc-option ...) because -fno-PIE is supported
since gcc v3.4 and our lowest supported gcc version is 3.2 right now.
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Cc: Ben Hutchings <ben@decadent.org.uk>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: default avatarMichal Marek <mmarek@suse.com>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: default avatarBen Hutchings <ben@decadent.org.uk>
parent f578da79
......@@ -407,11 +407,12 @@ KBUILD_CFLAGS := -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \
-fno-strict-aliasing -fno-common \
-Werror-implicit-function-declaration \
-Wno-format-security \
-std=gnu89
-std=gnu89 $(call cc-option,-fno-PIE)
KBUILD_AFLAGS_KERNEL :=
KBUILD_CFLAGS_KERNEL :=
KBUILD_AFLAGS := -D__ASSEMBLY__
KBUILD_AFLAGS := -D__ASSEMBLY__ $(call cc-option,-fno-PIE)
KBUILD_AFLAGS_MODULE := -DMODULE
KBUILD_CFLAGS_MODULE := -DMODULE
KBUILD_LDFLAGS_MODULE := -T $(srctree)/scripts/module-common.lds
......@@ -615,8 +616,6 @@ all: vmlinux
include $(srctree)/arch/$(SRCARCH)/Makefile
KBUILD_CFLAGS += $(call cc-option,-fno-delete-null-pointer-checks,)
KBUILD_CFLAGS += $(call cc-option,-fno-PIE)
KBUILD_AFLAGS += $(call cc-option,-fno-PIE)
ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
KBUILD_CFLAGS += -Os $(call cc-disable-warning,maybe-uninitialized,)
......
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