linux-kernel - [PATCH v7 09/39] arm64/gcs: Provide put_user

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Date:   Wed, 22 Nov 2023 09:42:19 +0000
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>,
        Florian Weimer <fweimer@...hat.com>,
        Christian Brauner <brauner@...nel.org>,
        Thiago Jung Bauermann <thiago.bauermann@...aro.org>,
        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 v7 09/39] arm64/gcs: Provide put_user_gcs()

In order for EL1 to write to an EL0 GCS it must use the GCSSTTR instruction
rather than a normal STTR. Provide a put_user_gcs() which does this.

Signed-off-by: Mark Brown <broonie@...nel.org>
---
 arch/arm64/include/asm/uaccess.h | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
index 22e10e79f56a..e118c3d772c8 100644
--- a/arch/arm64/include/asm/uaccess.h
+++ b/arch/arm64/include/asm/uaccess.h
@@ -445,6 +445,24 @@ static inline int gcssttr(unsigned long __user *addr, unsigned long val)
 	return err;
 }
 
+static inline void put_user_gcs(unsigned long val, unsigned long __user *addr,
+				int *err)
+{
+	int ret;
+
+	if (!access_ok((char __user *)addr, sizeof(u64))) {
+		*err = -EFAULT;
+		return;
+	}
+
+	uaccess_ttbr0_enable();
+	ret = gcssttr(addr, val);
+	if (ret != 0)
+		*err = ret;
+	uaccess_ttbr0_disable();
+}
+
+
 #endif /* CONFIG_ARM64_GCS */
 
 #endif /* __ASM_UACCESS_H */

-- 
2.39.2