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From:   "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
To:     bp@alien8.de
Cc:     peterz@infradead.org, linux-kernel@vger.kernel.org,
        "Jiri Slaby (SUSE)" <jirislaby@kernel.org>,
        Yu-cheng Yu <yu-cheng.yu@intel.com>,
        Rick Edgecombe <rick.p.edgecombe@intel.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Kees Cook <keescook@chromium.org>,
        Mike Rapoport <rppt@kernel.org>,
        Pengfei Xu <pengfei.xu@intel.com>,
        John Allen <john.allen@amd.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>, x86@kernel.org
Subject: [PATCH] x86: Let AS_WRUSS depend on X86_64
Date:   Tue, 31 Oct 2023 11:21:11 +0100
Message-ID: <20231031102111.32142-1-jirislaby@kernel.org>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

Since commit 18e66b695e78 ("x86/shstk: Add Kconfig option for shadow
stack"), AS_WRUSS is set even in 32-bit .configs. It is due to how
Kbuild works. .config is not considered during make oldconfig (and other
make *config), so standard (64-bit) gcc is invoked from 'as-instr'
Kbuild tests. And such gcc indeed reports that wruss is supported, so
AS_WRUSS=y is set.

Provided the wruss instruction is 64-bit only (and used in pure 64-bit
X86_USER_SHADOW_STACK), it has little sense to have AS_WRUSS=y set on
32-bit.

Therefore, make the whole test dependent on X86_64 to ensure it's set
only on 64-bit.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Cc: Yu-cheng Yu <yu-cheng.yu@intel.com>
Cc: Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Borislav Petkov (AMD) <bp@alien8.de>
Cc: Kees Cook <keescook@chromium.org>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Pengfei Xu <pengfei.xu@intel.com>
Cc: John Allen <john.allen@amd.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
---
 arch/x86/Kconfig.assembler | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/Kconfig.assembler b/arch/x86/Kconfig.assembler
index 8ad41da301e5..a5b5241711e3 100644
--- a/arch/x86/Kconfig.assembler
+++ b/arch/x86/Kconfig.assembler
@@ -27,5 +27,6 @@ config AS_GFNI
 
 config AS_WRUSS
 	def_bool $(as-instr,wrussq %rax$(comma)(%rbx))
+	depends on X86_64
 	help
 	  Supported by binutils >= 2.31 and LLVM integrated assembler
-- 
2.42.0