[PATCH 06/11] mm: Introduce ARCH_HAS_KERNEL_SHADOW_STACK

[Deepak Gupta <debug@rivosinc.com>]

commit bcc9d04e74 ("mm: Introduce ARCH_HAS_USER_SHADOW_STACK") introduced
`ARCH_HAS_USER_SHADOW_STACK`. Introducing `ARCH_HAS_KERNEL_SHADOW_STACK`
so that arches can enable hardware assistance for kernel shadow stack.

If `CONFIG_DYNAMIC_SCS` or `CONFIG_ARCH_HAS_KERNEL_SHADOW_STACK` are
selected, skip compiler flag `-fsanitizer=shadow-call-stack`.

Signed-off-by: Deepak Gupta <debug@rivosinc.com>
---
 Makefile   | 2 +-
 mm/Kconfig | 6 ++++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index 35e6e5240c61..7e3ecca9353d 100644
--- a/Makefile
+++ b/Makefile
@@ -987,7 +987,7 @@ LDFLAGS_vmlinux += --gc-sections
 endif
 
 ifdef CONFIG_SHADOW_CALL_STACK
-ifndef CONFIG_DYNAMIC_SCS
+ifeq ($(or $(CONFIG_DYNAMIC_SCS),$(CONFIG_ARCH_HAS_KERNEL_SHADOW_STACK)),false)
 CC_FLAGS_SCS	:= -fsanitize=shadow-call-stack
 KBUILD_CFLAGS	+= $(CC_FLAGS_SCS)
 KBUILD_RUSTFLAGS += -Zsanitizer=shadow-call-stack
diff --git a/mm/Kconfig b/mm/Kconfig
index 781be3240e21..f295ea611cdb 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -1367,6 +1367,12 @@ config ARCH_HAS_USER_SHADOW_STACK
 	  The architecture has hardware support for userspace shadow call
           stacks (eg, x86 CET, arm64 GCS or RISC-V Zicfiss).
 
+config ARCH_HAS_KERNEL_SHADOW_STACK
+	bool
+	help
+	  The architecture has hardware support for kernel shadow call
+          stacks (eg, x86 CET, arm64 GCS or RISC-V Zicfiss).
+
 config ARCH_SUPPORTS_PT_RECLAIM
 	def_bool n
 

-- 
2.43.0