From nobody Tue Feb 10 01:36:08 2026 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 8023A20E333; Mon, 7 Apr 2025 16:20:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744042813; cv=none; b=n8Q4EKaqicWrAYYfHCQIRzuv7W7CiiYLwJAEklAWGD8eP61tKiedBI4TnngSNba3CQX80Q/BVtJVpYCGgDM146Pj73o+/IXwokOX7wnBmml+F3nPt8CAF0QRA0AA5ppSxLf5WR9gkLw+6MJ0ipXxQR8McWCYJoVz3+5WlxN2Gyg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744042813; c=relaxed/simple; bh=74l8WQJx+JHUOxctsCLtwn1uQDcdHtUHH9jZWyzig0g=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=FWOR9VhrDEqJbqWpANjk0acFFw/z12DpJ7frRG+pLchdxU+GJYt3eq+IGHZukFCKzomvYSv8acuQUZPjUa0PePcTohhzK4jyCdfP/TID0P4cWjEQ8+XyNllsCORWZq09Iiqv8ntwgc9s3nqHwoNP5V8qr8h1bm9nV9ubBsCh2MA= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 006691BC0; Mon, 7 Apr 2025 09:20:12 -0700 (PDT) Received: from u200865.usa.arm.com (usa-sjc-mx-foss1.foss.arm.com [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 68C763F694; Mon, 7 Apr 2025 09:20:10 -0700 (PDT) From: Jeremy Linton To: linux-trace-kernel@vger.kernel.org Cc: linux-perf-users@vger.kernel.org, mhiramat@kernel.org, oleg@redhat.com, peterz@infradead.org, acme@kernel.org, namhyung@kernel.org, mark.rutland@arm.com, alexander.shishkin@linux.intel.com, jolsa@kernel.org, irogers@google.com, adrian.hunter@intel.com, kan.liang@linux.intel.com, thiago.bauermann@linaro.org, broonie@kernel.org, yury.khrustalev@arm.com, kristina.martsenko@arm.com, liaochang1@huawei.com, catalin.marinas@arm.com, will@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Jeremy Linton Subject: [PATCH v2 3/6] arm64: uaccess: Add additional userspace GCS accessors Date: Mon, 7 Apr 2025 11:19:48 -0500 Message-ID: <20250407161951.560865-4-jeremy.linton@arm.com> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250407161951.560865-1-jeremy.linton@arm.com> References: <20250407161951.560865-1-jeremy.linton@arm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Uprobes need more advanced read, push, and pop userspace GCS functionality. Implement those features using the existing gcsstr() and copy_from_user(). Its important to note that GCS pages can be read by normal instructions, but the hardware validates that pages used by GCS specific operations, have a GCS privilege set. We aren't validating this in load_user_gcs because it requires stabilizing the VMA over the read which may fault. Signed-off-by: Jeremy Linton --- arch/arm64/include/asm/uaccess.h | 42 ++++++++++++++++++++++++++++++++ 1 file changed, 42 insertions(+) diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uacc= ess.h index 5b91803201ef..34a8b2cc8935 100644 --- a/arch/arm64/include/asm/uaccess.h +++ b/arch/arm64/include/asm/uaccess.h @@ -20,6 +20,7 @@ =20 #include #include +#include #include #include #include @@ -539,6 +540,47 @@ static inline void put_user_gcs(unsigned long val, uns= igned long __user *addr, uaccess_ttbr0_disable(); } =20 +static __always_inline unsigned long __must_check +copy_from_user(void *to, const void __user *from, unsigned long n); + +/* + * Unlike put_user_gcs() above, the use of copy_from_user() may provide + * an opening for non GCS pages to be used to source data. Therefore this + * should only be used in contexts where that is acceptable. + */ +static inline u64 load_user_gcs(unsigned long __user *addr, int *err) +{ + unsigned long ret; + u64 load =3D 0; + + gcsb_dsync(); + ret =3D copy_from_user(&load, addr, sizeof(load)); + if (ret !=3D 0) + *err =3D ret; + return load; +} + +static inline void push_user_gcs(unsigned long val, int *err) +{ + u64 gcspr =3D read_sysreg_s(SYS_GCSPR_EL0); + + gcspr -=3D sizeof(u64); + put_user_gcs(val, (unsigned long __user *)gcspr, err); + if (!*err) + write_sysreg_s(gcspr, SYS_GCSPR_EL0); +} + +static inline u64 pop_user_gcs(int *err) +{ + u64 gcspr =3D read_sysreg_s(SYS_GCSPR_EL0); + u64 read_val; + + read_val =3D load_user_gcs((unsigned long __user *)gcspr, err); + if (!*err) + write_sysreg_s(gcspr + sizeof(u64), SYS_GCSPR_EL0); + + return read_val; +} =20 #endif /* CONFIG_ARM64_GCS */ =20 --=20 2.49.0