Received-SPF: pass (google.com: domain of linux-kernel+bounces-191415-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:40f1:3f00::1 as permitted sender) client-ip=2604:1380:40f1:3f00::1;
From: John Hubbard <jhubbard@nvidia.com>
To: Shuah Khan <shuah@kernel.org>
Cc: angquan yu <angquan21@gmail.com>,
	"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
	Ingo Molnar <mingo@kernel.org>,
	Binbin Wu <binbin.wu@linux.intel.com>,
	Alexey Dobriyan <adobriyan@gmail.com>,
	Rick Edgecombe <rick.p.edgecombe@intel.com>,
	Sohil Mehta <sohil.mehta@intel.com>,
	Yu-cheng Yu <yu-cheng.yu@intel.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Valentin Obst <kernel@valentinobst.de>,
	linux-kselftest@vger.kernel.org,
	LKML <linux-kernel@vger.kernel.org>,
	llvm@lists.linux.dev,
	x86@kernel.org,
	John Hubbard <jhubbard@nvidia.com>
Subject: [PATCH v2 2/6] selftests/x86: build fsgsbase_restore.c with clang
Date: Mon, 27 May 2024 14:00:38 -0700
Message-ID: <20240527210042.220315-3-jhubbard@nvidia.com>
In-Reply-To: <20240527210042.220315-1-jhubbard@nvidia.com>
References: <20240527210042.220315-1-jhubbard@nvidia.com>
Content-Transfer-Encoding: 8bit
Content-Type: text/plain
Precedence: bulk
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0:
	=?us-ascii?Q?JnU2qd/t7Siq2LA8k7hAUGpdSN62hpG+XWr3e8B1QNCR3nN9foMcyURV6qoO?=
 =?us-ascii?Q?DYyTuWifJsL+w7Bf21YIGKcMB4TAa+vkR9blV8OFaftVvLORFd/TQTKu42CB?=
 =?us-ascii?Q?YLeO2A4gRiKBY7WXNFazcddsTxZFMu8lTHmIbczZXINPziF/ZBP56hgqc+7S?=
 =?us-ascii?Q?F90mwbCKiKkaLxt0AyUS49lxhSGCHZ5Q8cE4bHy/7b0JGO5pXqiyt16sp7zS?=
 =?us-ascii?Q?jFTZDL76A/z1rnj6lDA1mnNnCTjD+B5EFJme8zlUEByQnb/StzVdAyXvqT5f?=
 =?us-ascii?Q?2/CpiuA8bJwTKfoyLqEJEquTmj1wi0Qoabc3FnSYTRJcn6QwSXDd87I9QWS8?=
 =?us-ascii?Q?uUFGPSJfrDrDWufijtbv6sNO6O4PlD+NrSn5wgzAOKekgr5Brc1QMqeLOaPf?=
 =?us-ascii?Q?Fqbf32Ji0JEzgVuOHh+kWrvHu1sTcruve/TtgH5JLarNIv1EZ/h92leEdQmd?=
 =?us-ascii?Q?vaqyEEF1B9TD5VV5bQpi+ujRWzf48bRpunMgTMvaqYLR87myVe+9P9P6NpPh?=
 =?us-ascii?Q?RqLNuTKbBkHGh0W5WCCSJEVPxviqqJyTpY4DEe4bPOZaFTjrtLkrOWv8zr2T?=
 =?us-ascii?Q?dcMk11iCIpWEIMEBm3VyC1FPTB4r4G9WYkkDbbne21C1i6pdSEd0l0H4uvIn?=
 =?us-ascii?Q?EDFZJU41nbeQUDkdop+MUSIvVrOznZxxzB1HVd5MS9ThqGg+9krBREed9xTe?=
 =?us-ascii?Q?XgO0Tl9nc584NSTKTWVCenycQFxi255rEFAIl5j2oaXu0zrJ9i72q94uCJ0C?=
 =?us-ascii?Q?VNpGF5PyzvnGRxvOdmBwy2sf+jJ83EL0PvTHGNNKUmJaShA04HoWrl+d2018?=
 =?us-ascii?Q?fPHO9g/+koIhe3lnWMxRLZzDHtU1chmED1C7V88R3W/j/14eUuTUWWoLWHtk?=
 =?us-ascii?Q?27Cp2B237G6J9Ed6Szg67DouDg9+2x4qoXO0HivgdDRbwm5IvLmN5rMM9nk6?=
 =?us-ascii?Q?V3gqN/zZKBYqlU3VYHBGf7Wi/HberTAON+DYtbdbVpG/iLV1VjHh9zWUC8y2?=
 =?us-ascii?Q?wCY71zY2YgX1T8ro2aF3Q/SAyGwZJwb6WN1GZbNeKNpthphJerp+7K6JiTDS?=
 =?us-ascii?Q?88fepL1Ygl8yOsq96R4Y9FxFgeytd/1AF+COznUDET7Gp4FtibZ6KIUj7tB1?=
 =?us-ascii?Q?TmVfTkiQ3NJnyhzX6kN45jRKZbsJZ4VMrI9Kd0lREycIwCmlQErIN9cTq5N7?=
 =?us-ascii?Q?fSFO6crWE8Sn4TZkWqyiLYIhYsZHd4ArmSjJ/dp+E1BXAwIzWuSV+P3D83tJ?=
 =?us-ascii?Q?Nj9I4377c8z3zBgITPKUu0CMZaKG2ru0NeeNWwWZR1/3T0KCIqYiHW5OSlvh?=
 =?us-ascii?Q?pJ5eGC/HX1etdhRu2tJn1yb93iivX9F0OJ1GvwiU6RORgbLOsihoTbV3wUD8?=
 =?us-ascii?Q?MuOE2oReoYMmfwtyfnHqy2W9E4PSeODMFAzJ5zVICLaRmmbOf32yVCwnRtc7?=
 =?us-ascii?Q?T+mg4vB4tlHNX5yPZEXTcaxHX0v54NtqhLa6Ju+bwb+RLIaAAqoUaqNpOVq5?=
 =?us-ascii?Q?8FU9Z05Oz55XxXNUXqfqfL7uZ8C0PkHK8TyyQ3d97WZMGO5QDPktPRgAUqb6?=
 =?us-ascii?Q?Old1oxC9xGikqzNql4yHUu9e5AbR0Up0AZNHof7wjWgQEkQfpHyODMDDwlHt?=
 =?us-ascii?Q?nA=3D=3D?=
X-OriginatorOrg: Nvidia.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 3e3fa4da-1e66-4a99-6887-08dc7e9020d1
X-MS-Exchange-CrossTenant-AuthSource: BY5PR12MB4130.namprd12.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 27 May 2024 21:01:07.1438
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: L2dptyZTpLprx3zP2QZuGufdjipxImzDv6yYLj53VieYoNXsfEweouiTRgH9eI4hE6q/MJZ068ukvMWWVciz+w==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: BL3PR12MB6620

First of all, in order to build with clang at all, one must first apply
Valentin Obst's build fix for LLVM [1]. Once that is done, then when
building with clang, via:

    make LLVM=1 -C tools/testing/selftests

Fix this by moving the inline asm to "pure" assembly, in two new files:
clang_helpers_32.S, clang_helpers_64.S.

As a bonus, the pure asm avoids the need for ifdefs, and is now very
simple and easy on the eyes.

[1] https://lore.kernel.org/all/20240329-selftests-libmk-llvm-rfc-v1-1-2f9ed7d1c49f@valentinobst.de/

Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 tools/testing/selftests/x86/Makefile           |  2 ++
 tools/testing/selftests/x86/clang_helpers_32.S | 11 +++++++++++
 tools/testing/selftests/x86/clang_helpers_64.S | 12 ++++++++++++
 tools/testing/selftests/x86/fsgsbase_restore.c | 11 +++++------
 4 files changed, 30 insertions(+), 6 deletions(-)
 create mode 100644 tools/testing/selftests/x86/clang_helpers_32.S
 create mode 100644 tools/testing/selftests/x86/clang_helpers_64.S

diff --git a/tools/testing/selftests/x86/Makefile b/tools/testing/selftests/x86/Makefile
index c1269466e0f8..99bc2ef84f5a 100644
--- a/tools/testing/selftests/x86/Makefile
+++ b/tools/testing/selftests/x86/Makefile
@@ -113,6 +113,8 @@ endef
 $(eval $(call extra-files,sysret_ss_attrs_64,thunks.S))
 $(eval $(call extra-files,ptrace_syscall_32,raw_syscall_helper_32.S))
 $(eval $(call extra-files,test_syscall_vdso_32,thunks_32.S))
+$(eval $(call extra-files,fsgsbase_restore_64,clang_helpers_64.S))
+$(eval $(call extra-files,fsgsbase_restore_32,clang_helpers_32.S))
 
 # check_initial_reg_state is special: it needs a custom entry, and it
 # needs to be static so that its interpreter doesn't destroy its initial
diff --git a/tools/testing/selftests/x86/clang_helpers_32.S b/tools/testing/selftests/x86/clang_helpers_32.S
new file mode 100644
index 000000000000..dc16271bac70
--- /dev/null
+++ b/tools/testing/selftests/x86/clang_helpers_32.S
@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * 32-bit assembly helpers for asm operations that lack support in both gcc and
+ * clang. For example, clang asm does not support segment prefixes.
+ */
+.global dereference_seg_base
+dereference_seg_base:
+	mov %fs:(0), %eax
+	ret
+
+.section .note.GNU-stack,"",%progbits
diff --git a/tools/testing/selftests/x86/clang_helpers_64.S b/tools/testing/selftests/x86/clang_helpers_64.S
new file mode 100644
index 000000000000..0d81c71cad97
--- /dev/null
+++ b/tools/testing/selftests/x86/clang_helpers_64.S
@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * 64-bit assembly helpers for asm operations that lack support in both gcc and
+ * clang. For example, clang asm does not support segment prefixes.
+ */
+.global dereference_seg_base
+
+dereference_seg_base:
+	mov %gs:(0), %rax
+	ret
+
+.section .note.GNU-stack,"",%progbits
diff --git a/tools/testing/selftests/x86/fsgsbase_restore.c b/tools/testing/selftests/x86/fsgsbase_restore.c
index 6fffadc51579..224058c1e4b2 100644
--- a/tools/testing/selftests/x86/fsgsbase_restore.c
+++ b/tools/testing/selftests/x86/fsgsbase_restore.c
@@ -39,12 +39,11 @@
 # define SEG "%fs"
 #endif
 
-static unsigned int dereference_seg_base(void)
-{
-	int ret;
-	asm volatile ("mov %" SEG ":(0), %0" : "=rm" (ret));
-	return ret;
-}
+/*
+ * Defined in clang_helpers_[32|64].S, because unlike gcc, clang inline asm does
+ * not support segmentation prefixes.
+ */
+unsigned int dereference_seg_base(void);
 
 static void init_seg(void)
 {
-- 
2.45.1