Commit 59612b24 authored by Nathan Chancellor's avatar Nathan Chancellor Committed by Masahiro Yamada
Browse files

kbuild: Hoist '--orphan-handling' into Kconfig 

Currently, '--orphan-handling=warn' is spread out across four different
architectures in their respective Makefiles, which makes it a little
unruly to deal with in case it needs to be disabled for a specific
linker version (in this case, ld.lld 10.0.1).

To make it easier to control this, hoist this warning into Kconfig and
the main Makefile so that disabling it is simpler, as the warning will
only be enabled in a couple places (main Makefile and a couple of
compressed boot folders that blow away LDFLAGS_vmlinx) and making it
conditional is easier due to Kconfig syntax. One small additional
benefit of this is saving a call to ld-option on incremental builds
because we will have already evaluated it for CONFIG_LD_ORPHAN_WARN.

To keep the list of supported architectures the same, introduce
CONFIG_ARCH_WANT_LD_ORPHAN_WARN, which an architecture can select to
gain this automatically after all of the sections are specified and size
asserted. A special thanks to Kees Cook for the help text on this
config.

Link: https://github.com/ClangBuiltLinux/linux/issues/1187


Acked-by: default avatarKees Cook <keescook@chromium.org>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Reviewed-by: default avatarNick Desaulniers <ndesaulniers@google.com>
Tested-by: default avatarNick Desaulniers <ndesaulniers@google.com>
Signed-off-by: default avatarNathan Chancellor <natechancellor@gmail.com>
Signed-off-by: default avatarMasahiro Yamada <masahiroy@kernel.org>
parent b8a90923

Makefile

+6 −0
Original line number Diff line number Diff line
@@ -986,6 +986,12 @@ ifeq ($(CONFIG_RELR),y) 
LDFLAGS_vmlinux	+= --pack-dyn-relocs=relr

endif



# We never want expected sections to be placed heuristically by the

# linker. All sections should be explicitly named in the linker script.

ifdef CONFIG_LD_ORPHAN_WARN

LDFLAGS_vmlinux += --orphan-handling=warn

endif



# Align the bit size of userspace programs with the kernel

KBUILD_USERCFLAGS  += $(filter -m32 -m64 --target=%, $(KBUILD_CFLAGS))

KBUILD_USERLDFLAGS += $(filter -m32 -m64 --target=%, $(KBUILD_CFLAGS))

arch/Kconfig

+9 −0
Original line number Diff line number Diff line
@@ -1028,6 +1028,15 @@ config HAVE_STATIC_CALL_INLINE 
	bool

	depends on HAVE_STATIC_CALL



config ARCH_WANT_LD_ORPHAN_WARN

	bool

	help

	  An arch should select this symbol once all linker sections are explicitly

	  included, size-asserted, or discarded in the linker scripts. This is

	  important because we never want expected sections to be placed heuristically

	  by the linker, since the locations of such sections can change between linker

	  versions.



source "kernel/gcov/Kconfig"



source "scripts/gcc-plugins/Kconfig"

arch/arm/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -35,6 +35,7 @@ config ARM 
	select ARCH_USE_CMPXCHG_LOCKREF

	select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU

	select ARCH_WANT_IPC_PARSE_VERSION

	select ARCH_WANT_LD_ORPHAN_WARN

	select BINFMT_FLAT_ARGVP_ENVP_ON_STACK

	select BUILDTIME_TABLE_SORT if MMU

	select CLONE_BACKWARDS

arch/arm/Makefile

+0 −4
Original line number Diff line number Diff line
@@ -16,10 +16,6 @@ LDFLAGS_vmlinux += --be8 
KBUILD_LDFLAGS_MODULE	+= --be8

endif



# We never want expected sections to be placed heuristically by the

# linker. All sections should be explicitly named in the linker script.

LDFLAGS_vmlinux += $(call ld-option, --orphan-handling=warn)



GZFLAGS		:=-9

#KBUILD_CFLAGS	+=-pipe

arch/arm/boot/compressed/Makefile

+3 −1
Original line number Diff line number Diff line
@@ -129,7 +129,9 @@ LDFLAGS_vmlinux += --no-undefined 
# Delete all temporary local symbols

LDFLAGS_vmlinux += -X

# Report orphan sections

LDFLAGS_vmlinux += $(call ld-option, --orphan-handling=warn)

ifdef CONFIG_LD_ORPHAN_WARN

LDFLAGS_vmlinux += --orphan-handling=warn

endif

# Next argument is a linker script

LDFLAGS_vmlinux += -T

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