linux-kernel - [PATCH v13 14/40] mm: Define VM_SHADOW_STACK for arm64 when we support GCS

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Message-Id: <20241001-arm64-gcs-v13-14-222b78d87eee@kernel.org>
Date: Tue, 01 Oct 2024 23:58:53 +0100
From: Mark Brown <broonie@...nel.org>
To: Catalin Marinas <catalin.marinas@....com>, 
 Will Deacon <will@...nel.org>, Jonathan Corbet <corbet@....net>, 
 Andrew Morton <akpm@...ux-foundation.org>, Marc Zyngier <maz@...nel.org>, 
 Oliver Upton <oliver.upton@...ux.dev>, James Morse <james.morse@....com>, 
 Suzuki K Poulose <suzuki.poulose@....com>, Arnd Bergmann <arnd@...db.de>, 
 Oleg Nesterov <oleg@...hat.com>, Eric Biederman <ebiederm@...ssion.com>, 
 Shuah Khan <shuah@...nel.org>, 
 "Rick P. Edgecombe" <rick.p.edgecombe@...el.com>, 
 Deepak Gupta <debug@...osinc.com>, Ard Biesheuvel <ardb@...nel.org>, 
 Szabolcs Nagy <Szabolcs.Nagy@....com>, Kees Cook <kees@...nel.org>
Cc: "H.J. Lu" <hjl.tools@...il.com>, 
 Paul Walmsley <paul.walmsley@...ive.com>, 
 Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, 
 Florian Weimer <fweimer@...hat.com>, Christian Brauner <brauner@...nel.org>, 
 Thiago Jung Bauermann <thiago.bauermann@...aro.org>, 
 Ross Burton <ross.burton@....com>, David Spickett <david.spickett@....com>, 
 Yury Khrustalev <yury.khrustalev@....com>, 
 Wilco Dijkstra <wilco.dijkstra@....com>, 
 linux-arm-kernel@...ts.infradead.org, linux-doc@...r.kernel.org, 
 kvmarm@...ts.linux.dev, linux-fsdevel@...r.kernel.org, 
 linux-arch@...r.kernel.org, linux-mm@...ck.org, 
 linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-riscv@...ts.infradead.org, Mark Brown <broonie@...nel.org>
Subject: [PATCH v13 14/40] mm: Define VM_SHADOW_STACK for arm64 when we
 support GCS

Use VM_HIGH_ARCH_5 for guarded control stack pages.

Reviewed-by: Thiago Jung Bauermann <thiago.bauermann@...aro.org>
Reviewed-by: Catalin Marinas <catalin.marinas@....com>
Signed-off-by: Mark Brown <broonie@...nel.org>
---
 Documentation/filesystems/proc.rst |  2 +-
 include/linux/mm.h                 | 12 +++++++++++-
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst
index e834779d9611..6a882c57a7e7 100644
--- a/Documentation/filesystems/proc.rst
+++ b/Documentation/filesystems/proc.rst
@@ -579,7 +579,7 @@ encoded manner. The codes are the following:
     mt    arm64 MTE allocation tags are enabled
     um    userfaultfd missing tracking
     uw    userfaultfd wr-protect tracking
-    ss    shadow stack page
+    ss    shadow/guarded control stack page
     sl    sealed
     ==    =======================================

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 56654306a832..8852c39c7695 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -367,7 +367,17 @@ extern unsigned int kobjsize(const void *objp);
  * for more details on the guard size.
  */
 # define VM_SHADOW_STACK	VM_HIGH_ARCH_5
-#else
+#endif
+
+#if defined(CONFIG_ARM64_GCS)
+/*
+ * arm64's Guarded Control Stack implements similar functionality and
+ * has similar constraints to shadow stacks.
+ */
+# define VM_SHADOW_STACK	VM_HIGH_ARCH_6
+#endif
+
+#ifndef VM_SHADOW_STACK
 # define VM_SHADOW_STACK	VM_NONE
 #endif

-- 
2.39.2