linux-kernel - [PATCH v3 14/36] arm64/idreg: Add overrride for GCS

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Message-Id: <20230731-arm64-gcs-v3-14-cddf9f980d98@kernel.org>
Date:   Mon, 31 Jul 2023 14:43:23 +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>,
        Kees Cook <keescook@...omium.org>,
        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>
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>,
        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 v3 14/36] arm64/idreg: Add overrride for GCS

Hook up an override for GCS, allowing it to be disabled from the command
line by specifying arm64.nogcs in case there are problems.

Signed-off-by: Mark Brown <broonie@...nel.org>
---
 Documentation/admin-guide/kernel-parameters.txt | 3 +++
 arch/arm64/kernel/idreg-override.c              | 2 ++
 2 files changed, 5 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index a1457995fd41..86662eed3003 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -418,6 +418,9 @@
 	arm64.nobti	[ARM64] Unconditionally disable Branch Target
 			Identification support
 
+	arm64.nogcs	[ARM64] Unconditionally disable Guarded Control Stack
+			support
+
 	arm64.nopauth	[ARM64] Unconditionally disable Pointer Authentication
 			support
 
diff --git a/arch/arm64/kernel/idreg-override.c b/arch/arm64/kernel/idreg-override.c
index 2fe2491b692c..49269a5cff10 100644
--- a/arch/arm64/kernel/idreg-override.c
+++ b/arch/arm64/kernel/idreg-override.c
@@ -99,6 +99,7 @@ static const struct ftr_set_desc pfr1 __initconst = {
 	.override	= &id_aa64pfr1_override,
 	.fields		= {
 		FIELD("bt", ID_AA64PFR1_EL1_BT_SHIFT, NULL ),
+		FIELD("gcs", ID_AA64PFR1_EL1_GCS_SHIFT, NULL),
 		FIELD("mte", ID_AA64PFR1_EL1_MTE_SHIFT, NULL),
 		FIELD("sme", ID_AA64PFR1_EL1_SME_SHIFT, pfr1_sme_filter),
 		{}
@@ -178,6 +179,7 @@ static const struct {
 	{ "arm64.nosve",		"id_aa64pfr0.sve=0" },
 	{ "arm64.nosme",		"id_aa64pfr1.sme=0" },
 	{ "arm64.nobti",		"id_aa64pfr1.bt=0" },
+	{ "arm64.nogcs",		"id_aa64pfr1.gcs=0" },
 	{ "arm64.nopauth",
 	  "id_aa64isar1.gpi=0 id_aa64isar1.gpa=0 "
 	  "id_aa64isar1.api=0 id_aa64isar1.apa=0 "

-- 
2.30.2