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Message-ID: <20240704072431.111640-4-jhubbard@nvidia.com>
Date: Thu, 4 Jul 2024 00:24:27 -0700
From: John Hubbard <jhubbard@...dia.com>
To: Shuah Khan <shuah@...nel.org>
Cc: angquan yu <angquan21@...il.com>,
"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
Ingo Molnar <mingo@...nel.org>,
Binbin Wu <binbin.wu@...ux.intel.com>,
Alexey Dobriyan <adobriyan@...il.com>,
Rick Edgecombe <rick.p.edgecombe@...el.com>,
Sohil Mehta <sohil.mehta@...el.com>,
Yu-cheng Yu <yu-cheng.yu@...el.com>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Muhammad Usama Anjum <usama.anjum@...labora.com>,
Valentin Obst <kernel@...entinobst.de>,
linux-kselftest@...r.kernel.org,
LKML <linux-kernel@...r.kernel.org>,
llvm@...ts.linux.dev,
x86@...nel.org,
John Hubbard <jhubbard@...dia.com>
Subject: [PATCH v4 3/7] selftests/x86: build fsgsbase_restore.c with clang
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.
Acked-by: Muhammad Usama Anjum <usama.anjum@...labora.com>
Signed-off-by: John Hubbard <jhubbard@...dia.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)
{
--
2.45.2
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