linux-kernel - [PATCH v12 08/39] arm64/gcs: Add manual encodings of GCS instructions

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Message-Id: <20240829-arm64-gcs-v12-8-42fec947436a@kernel.org>
Date: Thu, 29 Aug 2024 00:27:24 +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>, 
 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 v12 08/39] arm64/gcs: Add manual encodings of GCS
 instructions

Define C callable functions for GCS instructions used by the kernel. In
order to avoid ambitious toolchain requirements for GCS support these are
manually encoded, this means we have fixed register numbers which will be
a bit limiting for the compiler but none of these should be used in
sufficiently fast paths for this to be a problem.

Note that GCSSTTR is used to store to EL0.

Reviewed-by: Thiago Jung Bauermann <thiago.bauermann@...aro.org>
Acked-by: Catalin Marinas <catalin.marinas@....com>
Signed-off-by: Mark Brown <broonie@...nel.org>
---
 arch/arm64/include/asm/gcs.h     | 51 ++++++++++++++++++++++++++++++++++++++++
 arch/arm64/include/asm/uaccess.h | 22 +++++++++++++++++
 2 files changed, 73 insertions(+)

diff --git a/arch/arm64/include/asm/gcs.h b/arch/arm64/include/asm/gcs.h
new file mode 100644
index 000000000000..7c5e95218db6
--- /dev/null
+++ b/arch/arm64/include/asm/gcs.h
@@ -0,0 +1,51 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2023 ARM Ltd.
+ */
+#ifndef __ASM_GCS_H
+#define __ASM_GCS_H
+
+#include <asm/types.h>
+#include <asm/uaccess.h>
+
+static inline void gcsb_dsync(void)
+{
+	asm volatile(".inst 0xd503227f" : : : "memory");
+}
+
+static inline void gcsstr(u64 *addr, u64 val)
+{
+	register u64 *_addr __asm__ ("x0") = addr;
+	register long _val __asm__ ("x1") = val;
+
+	/* GCSSTTR x1, x0 */
+	asm volatile(
+		".inst 0xd91f1c01\n"
+		:
+		: "rZ" (_val), "r" (_addr)
+		: "memory");
+}
+
+static inline void gcsss1(u64 Xt)
+{
+	asm volatile (
+		"sys #3, C7, C7, #2, %0\n"
+		:
+		: "rZ" (Xt)
+		: "memory");
+}
+
+static inline u64 gcsss2(void)
+{
+	u64 Xt;
+
+	asm volatile(
+		"SYSL %0, #3, C7, C7, #3\n"
+		: "=r" (Xt)
+		:
+		: "memory");
+
+	return Xt;
+}
+
+#endif
diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
index 28f665e0975a..6aba10e38d1c 100644
--- a/arch/arm64/include/asm/uaccess.h
+++ b/arch/arm64/include/asm/uaccess.h
@@ -502,4 +502,26 @@ static inline size_t probe_subpage_writeable(const char __user *uaddr,

 #endif /* CONFIG_ARCH_HAS_SUBPAGE_FAULTS */

+#ifdef CONFIG_ARM64_GCS
+
+static inline int gcssttr(unsigned long __user *addr, unsigned long val)
+{
+	register unsigned long __user *_addr __asm__ ("x0") = addr;
+	register unsigned long _val __asm__ ("x1") = val;
+	int err = 0;
+
+	/* GCSSTTR x1, x0 */
+	asm volatile(
+		"1: .inst 0xd91f1c01\n"
+		"2: \n"
+		_ASM_EXTABLE_UACCESS_ERR(1b, 2b, %w0)
+		: "+r" (err)
+		: "rZ" (_val), "r" (_addr)
+		: "memory");
+
+	return err;
+}
+
+#endif /* CONFIG_ARM64_GCS */
+
 #endif /* __ASM_UACCESS_H */

-- 
2.39.2