diff mbox series

[v6,07/25] treewide: remove DISABLE_LTO

Message ID 20201013003203.4168817-8-samitolvanen@google.com
State New, archived
Headers show
Series Add support for Clang LTO | expand

Commit Message

Sami Tolvanen Oct. 13, 2020, 12:31 a.m. UTC
This change removes all instances of DISABLE_LTO from
Makefiles, as they are currently unused, and the preferred
method of disabling LTO is to filter out the flags instead.

Suggested-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
---
 arch/arm64/kernel/vdso/Makefile | 1 -
 arch/sparc/vdso/Makefile        | 2 --
 arch/x86/entry/vdso/Makefile    | 2 --
 kernel/Makefile                 | 3 ---
 scripts/Makefile.build          | 2 +-
 5 files changed, 1 insertion(+), 9 deletions(-)

Comments

Kees Cook Oct. 14, 2020, 10:43 p.m. UTC | #1
On Mon, Oct 12, 2020 at 05:31:45PM -0700, Sami Tolvanen wrote:
> This change removes all instances of DISABLE_LTO from
> Makefiles, as they are currently unused, and the preferred
> method of disabling LTO is to filter out the flags instead.
> 
> Suggested-by: Kees Cook <keescook@chromium.org>
> Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
> Reviewed-by: Kees Cook <keescook@chromium.org>

Hi Masahiro,

Since this is independent of anything else and could be seen as a
general cleanup, can this patch be taken into your tree, just to
separate it from the list of dependencies for this series?

-Kees
Masahiro Yamada Oct. 17, 2020, 1:46 a.m. UTC | #2
On Thu, Oct 15, 2020 at 7:43 AM Kees Cook <keescook@chromium.org> wrote:
>
> On Mon, Oct 12, 2020 at 05:31:45PM -0700, Sami Tolvanen wrote:
> > This change removes all instances of DISABLE_LTO from
> > Makefiles, as they are currently unused, and the preferred
> > method of disabling LTO is to filter out the flags instead.
> >
> > Suggested-by: Kees Cook <keescook@chromium.org>
> > Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
> > Reviewed-by: Kees Cook <keescook@chromium.org>
>
> Hi Masahiro,
>
> Since this is independent of anything else and could be seen as a
> general cleanup, can this patch be taken into your tree, just to
> separate it from the list of dependencies for this series?
>
> -Kees
>
> --
> Kees Cook



Yes, this is stale code because GCC LTO was not pulled.

Applied to linux-kbuild.

I added the following historical background.



Note added by Masahiro Yamada:
DISABLE_LTO was added as preparation for GCC LTO, but GCC LTO was
not pulled into the mainline. (https://lkml.org/lkml/2014/4/8/272)
diff mbox series

Patch

diff --git a/arch/arm64/kernel/vdso/Makefile b/arch/arm64/kernel/vdso/Makefile
index 45d5cfe46429..e836e300440f 100644
--- a/arch/arm64/kernel/vdso/Makefile
+++ b/arch/arm64/kernel/vdso/Makefile
@@ -31,7 +31,6 @@  ccflags-y := -fno-common -fno-builtin -fno-stack-protector -ffixed-x18
 ccflags-y += -DDISABLE_BRANCH_PROFILING
 
 CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE) -Os $(CC_FLAGS_SCS) $(GCC_PLUGINS_CFLAGS)
-KBUILD_CFLAGS			+= $(DISABLE_LTO)
 KASAN_SANITIZE			:= n
 UBSAN_SANITIZE			:= n
 OBJECT_FILES_NON_STANDARD	:= y
diff --git a/arch/sparc/vdso/Makefile b/arch/sparc/vdso/Makefile
index f44355e46f31..476c4b315505 100644
--- a/arch/sparc/vdso/Makefile
+++ b/arch/sparc/vdso/Makefile
@@ -3,8 +3,6 @@ 
 # Building vDSO images for sparc.
 #
 
-KBUILD_CFLAGS += $(DISABLE_LTO)
-
 VDSO64-$(CONFIG_SPARC64)	:= y
 VDSOCOMPAT-$(CONFIG_COMPAT)	:= y
 
diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile
index 215376d975a2..ecc27018ae13 100644
--- a/arch/x86/entry/vdso/Makefile
+++ b/arch/x86/entry/vdso/Makefile
@@ -9,8 +9,6 @@  ARCH_REL_TYPE_ABS := R_X86_64_JUMP_SLOT|R_X86_64_GLOB_DAT|R_X86_64_RELATIVE|
 ARCH_REL_TYPE_ABS += R_386_GLOB_DAT|R_386_JMP_SLOT|R_386_RELATIVE
 include $(srctree)/lib/vdso/Makefile
 
-KBUILD_CFLAGS += $(DISABLE_LTO)
-
 # Sanitizer runtimes are unavailable and cannot be linked here.
 KASAN_SANITIZE			:= n
 UBSAN_SANITIZE			:= n
diff --git a/kernel/Makefile b/kernel/Makefile
index 16ec9262ce9d..2561abc91961 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -38,9 +38,6 @@  KASAN_SANITIZE_kcov.o := n
 KCSAN_SANITIZE_kcov.o := n
 CFLAGS_kcov.o := $(call cc-option, -fno-conserve-stack) -fno-stack-protector
 
-# cond_syscall is currently not LTO compatible
-CFLAGS_sys_ni.o = $(DISABLE_LTO)
-
 obj-y += sched/
 obj-y += locking/
 obj-y += power/
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index cd4294435fef..6db5b1f55b14 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -111,7 +111,7 @@  endif
 # ---------------------------------------------------------------------------
 
 quiet_cmd_cc_s_c = CC $(quiet_modtag)  $@
-      cmd_cc_s_c = $(CC) $(filter-out $(DEBUG_CFLAGS), $(c_flags)) $(DISABLE_LTO) -fverbose-asm -S -o $@ $<
+      cmd_cc_s_c = $(CC) $(filter-out $(DEBUG_CFLAGS), $(c_flags)) -fverbose-asm -S -o $@ $<
 
 $(obj)/%.s: $(src)/%.c FORCE
 	$(call if_changed_dep,cc_s_c)