Re: [RFC 17/17] arm64: compile the kernel with ptrauth -msign-return-address

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On 05/10/2018 09:47, Kristina Martsenko wrote:
Compile all functions with two ptrauth instructions: paciasp in the
prologue to sign the return address, and autiasp in the epilogue to
authenticate the return address. This should help protect the kernel
against attacks using return-oriented programming.

CONFIG_ARM64_PTR_AUTH enables pointer auth for both userspace and the
kernel.

Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx>
Signed-off-by: Kristina Martsenko <kristina.martsenko@xxxxxxx>
---
  arch/arm64/Makefile | 4 ++++
  1 file changed, 4 insertions(+)

diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index 106039d25e2f..dbcd43ea99d8 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -56,6 +56,10 @@ KBUILD_AFLAGS	+= $(lseinstr) $(brokengasinst)
  KBUILD_CFLAGS	+= $(call cc-option,-mabi=lp64)
  KBUILD_AFLAGS	+= $(call cc-option,-mabi=lp64)
+ifeq ($(CONFIG_ARM64_PTR_AUTH),y)
+KBUILD_CFLAGS	+= -msign-return-address=all

Glad to see this being done and being proposed for mainline.

I can see why you would prefer this though have you guys experimented at all with -msign-return-address=non-leaf as well ?

Orthogonally and just fair warning - the command lines for this are also being revised to provide ROP and JOP protection using BTI from v8.5-a during the GCC-9 timeframe but I suspect that's a different option.

regards
Ramana

Reviewed-by: Ramana Radhakrishnan  <ramana.radhakrishnan@xxxxxxx>
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