diff mbox series

[v2,26/28] x86, vdso: disable LTO only for vDSO

Message ID 20200903203053.3411268-27-samitolvanen@google.com (mailing list archive)
State New, archived
Headers show
Series Add support for Clang LTO | expand

Commit Message

Sami Tolvanen Sept. 3, 2020, 8:30 p.m. UTC 
Remove the undefined DISABLE_LTO flag from the vDSO, and filter out
CC_FLAGS_LTO flags instead where needed. Note that while we could use
Clang's LTO for the 64-bit vDSO, it won't add noticeable benefit for
the small amount of C code.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
 arch/x86/entry/vdso/Makefile | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

Comments

Kees Cook Sept. 3, 2020, 10:46 p.m. UTC | #1 
On Thu, Sep 03, 2020 at 01:30:51PM -0700, Sami Tolvanen wrote:
> Remove the undefined DISABLE_LTO flag from the vDSO, and filter out
> CC_FLAGS_LTO flags instead where needed. Note that while we could use
> Clang's LTO for the 64-bit vDSO, it won't add noticeable benefit for
> the small amount of C code.
> 
> Signed-off-by: Sami Tolvanen <samitolvanen@google.com>

Moar DISABLE_LTO...

Reviewed-by: Kees Cook <keescook@chromium.org>
diff mbox series

Patch

diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile
index 215376d975a2..9b742f21d2db 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 += $(DISABLE_LTO)
-
 # Sanitizer runtimes are unavailable and cannot be linked here.
 KASAN_SANITIZE			:= n
 UBSAN_SANITIZE			:= n
@@ -92,7 +90,7 @@  ifneq ($(RETPOLINE_VDSO_CFLAGS),)
 endif
 endif
 
-$(vobjs): KBUILD_CFLAGS := $(filter-out $(GCC_PLUGINS_CFLAGS) $(RETPOLINE_CFLAGS),$(KBUILD_CFLAGS)) $(CFL)
+$(vobjs): KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_LTO) $(GCC_PLUGINS_CFLAGS) $(RETPOLINE_CFLAGS),$(KBUILD_CFLAGS)) $(CFL)
 
 #
 # vDSO code runs in userspace and -pg doesn't help with profiling anyway.
@@ -150,6 +148,7 @@  KBUILD_CFLAGS_32 := $(filter-out -fno-pic,$(KBUILD_CFLAGS_32))
 KBUILD_CFLAGS_32 := $(filter-out -mfentry,$(KBUILD_CFLAGS_32))
 KBUILD_CFLAGS_32 := $(filter-out $(GCC_PLUGINS_CFLAGS),$(KBUILD_CFLAGS_32))
 KBUILD_CFLAGS_32 := $(filter-out $(RETPOLINE_CFLAGS),$(KBUILD_CFLAGS_32))
+KBUILD_CFLAGS_32 := $(filter-out $(CC_FLAGS_LTO),$(KBUILD_CFLAGS_32))
 KBUILD_CFLAGS_32 += -m32 -msoft-float -mregparm=0 -fpic
 KBUILD_CFLAGS_32 += -fno-stack-protector
 KBUILD_CFLAGS_32 += $(call cc-option, -foptimize-sibling-calls)