On 2/4/2021 11:56 AM, Kees Cook wrote:

On Wed, Feb 03, 2021 at 02:55:24PM -0800, Yu-cheng Yu wrote:

quoted

Shadow Stack provides protection against function return address
corruption.  It is active when the processor supports it, the kernel has
CONFIG_X86_CET enabled, and the application is built for the feature.
This is only implemented for the 64-bit kernel.  When it is enabled, legacy
non-Shadow Stack applications continue to work, but without protection.

Signed-off-by: Yu-cheng Yu <redacted>
---
  arch/x86/Kconfig           | 22 ++++++++++++++++++++++
  arch/x86/Kconfig.assembler |  5 +++++
  2 files changed, 27 insertions(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 21f851179ff0..074b3c0e6bf6 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig

@@ -1951,6 +1951,28 @@ config X86_SGX
  
  	  If unsure, say N.
  
+config ARCH_HAS_SHADOW_STACK
+	def_bool n
+
+config X86_CET
+	prompt "Intel Control-flow protection for user-mode"
+	def_bool n
+	depends on X86_64
+	depends on AS_WRUSS
+	select ARCH_USES_HIGH_VMA_FLAGS
+	select ARCH_HAS_SHADOW_STACK

This seems backwards to me? Shouldn't 'config X86_64' do the 'select
ARCH_HAS_SHADOW_STACK' and 'config X86_CET' do a 'depends on
ARCH_HAS_SHADOW_STACK' instead?

I will change it.  Thanks!

--
Yu-cheng