linux-kernel - [PATCH 06/11] mm: Introduce ARCH_HAS_KERNEL_SHADOW

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Message-Id: <20250724-riscv_kcfi-v1-6-04b8fa44c98c@rivosinc.com>
Date: Thu, 24 Jul 2025 16:36:59 -0700
From: Deepak Gupta <debug@...osinc.com>
To: Paul Walmsley <paul.walmsley@...ive.com>, 
 Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, 
 Alexandre Ghiti <alex@...ti.fr>, Masahiro Yamada <masahiroy@...nel.org>, 
 Nathan Chancellor <nathan@...nel.org>, 
 Nicolas Schier <nicolas.schier@...ux.dev>, 
 Andrew Morton <akpm@...ux-foundation.org>, 
 David Hildenbrand <david@...hat.com>, 
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, 
 "Liam R. Howlett" <Liam.Howlett@...cle.com>, 
 Vlastimil Babka <vbabka@...e.cz>, Mike Rapoport <rppt@...nel.org>, 
 Suren Baghdasaryan <surenb@...gle.com>, Michal Hocko <mhocko@...e.com>, 
 Nick Desaulniers <nick.desaulniers+lkml@...il.com>, 
 Bill Wendling <morbo@...gle.com>, Monk Chiang <monk.chiang@...ive.com>, 
 Kito Cheng <kito.cheng@...ive.com>, Justin Stitt <justinstitt@...gle.com>
Cc: linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org, 
 linux-kbuild@...r.kernel.org, linux-mm@...ck.org, llvm@...ts.linux.dev, 
 rick.p.edgecombe@...el.com, broonie@...nel.org, cleger@...osinc.com, 
 samitolvanen@...gle.com, apatel@...tanamicro.com, ajones@...tanamicro.com, 
 conor.dooley@...rochip.com, charlie@...osinc.com, samuel.holland@...ive.com, 
 bjorn@...osinc.com, fweimer@...hat.com, jeffreyalaw@...il.com, 
 heinrich.schuchardt@...onical.com, andrew@...ive.com, ved@...osinc.com, 
 Deepak Gupta <debug@...osinc.com>
Subject: [PATCH 06/11] mm: Introduce ARCH_HAS_KERNEL_SHADOW_STACK

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@...osinc.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