diff mbox series

[v7,15/17] KVM: arm64: disable LTO for the nVHE directory

Message ID 20201118220731.925424-16-samitolvanen@google.com (mailing list archive)
State New, archived
Headers show
Series Add support for Clang LTO | expand

Commit Message

Sami Tolvanen Nov. 18, 2020, 10:07 p.m. UTC 
We use objcopy to manipulate ELF binaries for the nVHE code,
which fails with LTO as the compiler produces LLVM bitcode
instead. Disable LTO for this code to allow objcopy to be used.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
---
 arch/arm64/kvm/hyp/nvhe/Makefile | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Comments

David Brazdil Nov. 23, 2020, 10:21 a.m. UTC | #1 
Hey Sami,

On Wed, Nov 18, 2020 at 02:07:29PM -0800, Sami Tolvanen wrote:
> We use objcopy to manipulate ELF binaries for the nVHE code,
> which fails with LTO as the compiler produces LLVM bitcode
> instead. Disable LTO for this code to allow objcopy to be used.

We now partially link the nVHE code (generating machine code) before objcopy,
so I think you should be able to drop this patch now. Tried building your
branch without it, ran a couple of unit tests and all seems fine.

David
Sami Tolvanen Nov. 23, 2020, 6:34 p.m. UTC | #2 
On Mon, Nov 23, 2020 at 2:21 AM David Brazdil <dbrazdil@google.com> wrote:
>
> Hey Sami,
>
> On Wed, Nov 18, 2020 at 02:07:29PM -0800, Sami Tolvanen wrote:
> > We use objcopy to manipulate ELF binaries for the nVHE code,
> > which fails with LTO as the compiler produces LLVM bitcode
> > instead. Disable LTO for this code to allow objcopy to be used.
>
> We now partially link the nVHE code (generating machine code) before objcopy,
> so I think you should be able to drop this patch now. Tried building your
> branch without it, ran a couple of unit tests and all seems fine.

Great, thanks for testing this, David! I'll drop this patch from v8.

Sami
diff mbox series

Patch

diff --git a/arch/arm64/kvm/hyp/nvhe/Makefile b/arch/arm64/kvm/hyp/nvhe/Makefile
index ddde15fe85f2..4ceed7682287 100644
--- a/arch/arm64/kvm/hyp/nvhe/Makefile
+++ b/arch/arm64/kvm/hyp/nvhe/Makefile
@@ -51,9 +51,9 @@  $(obj)/kvm_nvhe.o: $(obj)/kvm_nvhe.tmp.o FORCE
 quiet_cmd_hypcopy = HYPCOPY $@
       cmd_hypcopy = $(OBJCOPY) --prefix-symbols=__kvm_nvhe_ $< $@
 
-# Remove ftrace and Shadow Call Stack CFLAGS.
+# Remove ftrace, LTO, and Shadow Call Stack CFLAGS.
 # This is equivalent to the 'notrace' and '__noscs' annotations.
-KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_FTRACE) $(CC_FLAGS_SCS), $(KBUILD_CFLAGS))
+KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_FTRACE) $(CC_FLAGS_LTO) $(CC_FLAGS_SCS), $(KBUILD_CFLAGS))
 
 # KVM nVHE code is run at a different exception code with a different map, so
 # compiler instrumentation that inserts callbacks or checks into the code may