linux-kernel - [PATCH] x86/kconfig: add as-instr64 macro to properly evaluate AS

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Date: Wed, 12 Jun 2024 14:02:55 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: linux-kbuild@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	x86@...nel.org
Cc: linux-kernel@...r.kernel.org,
	"H . Peter Anvin" <hpa@...or.com>,
	Dmitry Safonov <0x7f454c46@...il.com>,
	Masahiro Yamada <masahiroy@...nel.org>,
	"Mike Rapoport (IBM)" <rppt@...nel.org>,
	Rick Edgecombe <rick.p.edgecombe@...el.com>,
	Yu-cheng Yu <yu-cheng.yu@...el.com>
Subject: [PATCH] x86/kconfig: add as-instr64 macro to properly evaluate AS_WRUSS

Some instructions are only available on the 64-bit architecture.

Bi-arch compilers that default to -m32 need the explicit -m64 option
to evaluate them properly.

Fixes: 18e66b695e78 ("x86/shstk: Add Kconfig option for shadow stack")
Reported-by: Dmitry Safonov <0x7f454c46@...il.com>
Closes: https://lore.kernel.org/all/20240612-as-instr-opt-wrussq-v2-1-bd950f7eead7@gmail.com/
Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
---

 arch/x86/Kconfig.assembler | 2 +-
 scripts/Kconfig.include    | 3 ++-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/Kconfig.assembler b/arch/x86/Kconfig.assembler
index 59aedf32c4ea..6d20a6ce0507 100644
--- a/arch/x86/Kconfig.assembler
+++ b/arch/x86/Kconfig.assembler
@@ -36,6 +36,6 @@ config AS_VPCLMULQDQ
 	  Supported by binutils >= 2.30 and LLVM integrated assembler
 
 config AS_WRUSS
-	def_bool $(as-instr,wrussq %rax$(comma)(%rbx))
+	def_bool $(as-instr64,wrussq %rax$(comma)(%rbx))
 	help
 	  Supported by binutils >= 2.31 and LLVM integrated assembler
diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include
index 3ee8ecfb8c04..3500a3d62f0d 100644
--- a/scripts/Kconfig.include
+++ b/scripts/Kconfig.include
@@ -33,7 +33,8 @@ ld-option = $(success,$(LD) -v $(1))
 
 # $(as-instr,<instr>)
 # Return y if the assembler supports <instr>, n otherwise
-as-instr = $(success,printf "%b\n" "$(1)" | $(CC) $(CLANG_FLAGS) -Wa$(comma)--fatal-warnings -c -x assembler-with-cpp -o /dev/null -)
+as-instr = $(success,printf "%b\n" "$(1)" | $(CC) $(CLANG_FLAGS) $(2) -Wa$(comma)--fatal-warnings -c -x assembler-with-cpp -o /dev/null -)
+as-instr64 = $(as-instr,$(1),$(m64-flag))
 
 # check if $(CC) and $(LD) exist
 $(error-if,$(failure,command -v $(CC)),C compiler '$(CC)' not found)
-- 
2.43.0