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From:   Mark Brown <broonie@kernel.org>
Date:   Mon, 07 Aug 2023 23:00:12 +0100
Subject: [PATCH v4 07/36] arm64/gcs: Provide copy_to_user_gcs()
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To:     Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Jonathan Corbet <corbet@lwn.net>,
        Andrew Morton <akpm@linux-foundation.org>,
        Marc Zyngier <maz@kernel.org>,
        Oliver Upton <oliver.upton@linux.dev>,
        James Morse <james.morse@arm.com>,
        Suzuki K Poulose <suzuki.poulose@arm.com>,
        Arnd Bergmann <arnd@arndb.de>, Oleg Nesterov <oleg@redhat.com>,
        Eric Biederman <ebiederm@xmission.com>,
        Kees Cook <keescook@chromium.org>,
        Shuah Khan <shuah@kernel.org>,
        "Rick P. Edgecombe" <rick.p.edgecombe@intel.com>,
        Deepak Gupta <debug@rivosinc.com>,
        Ard Biesheuvel <ardb@kernel.org>,
        Szabolcs Nagy <Szabolcs.Nagy@arm.com>
Cc:     "H.J. Lu" <hjl.tools@gmail.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org,
        kvmarm@lists.linux.dev, linux-fsdevel@vger.kernel.org,
        linux-arch@vger.kernel.org, linux-mm@kvack.org,
        linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-riscv@lists.infradead.org, Mark Brown <broonie@kernel.org>
Precedence: bulk

In order for EL1 to write to an EL0 GCS it must use the GCSSTTR instruction
rather than a normal STTR. Provide a copy_to_user_gcs() which does this.
Since it is not possible to store anything other than a 64 bit value the
interface is presented in terms of 64 bit values, using unsigned long
rather than u64 due to sparse.

Signed-off-by: Mark Brown <broonie@kernel.org>
---
 arch/arm64/include/asm/uaccess.h | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
index 22e10e79f56a..24aa804e95a7 100644
--- a/arch/arm64/include/asm/uaccess.h
+++ b/arch/arm64/include/asm/uaccess.h
@@ -445,6 +445,26 @@ static inline int gcssttr(unsigned long __user *addr, unsigned long val)
 	return err;
 }
 
+static inline int copy_to_user_gcs(unsigned long __user *addr,
+				   unsigned long *val,
+				   int count)
+{
+	int ret = -EFAULT;
+	int i;
+
+	if (access_ok((char __user *)addr, count * sizeof(u64))) {
+		uaccess_ttbr0_enable();
+		for (i = 0; i < count; i++) {
+			ret = gcssttr(addr++, *val++);
+			if (ret != 0)
+				break;
+		}
+		uaccess_ttbr0_disable();
+	}
+
+	return ret;
+}
+
 #endif /* CONFIG_ARM64_GCS */
 
 #endif /* __ASM_UACCESS_H */

-- 
2.30.2