From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8FBB533C7; Fri, 17 Jun 2022 18:15:04 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 75B7EC3411B; Fri, 17 Jun 2022 18:15:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1655489704; bh=QUh4kC7NXGm1YEXl3pKZXaJzSvNx6+iaW+R315T3U6U=; h=From:To:Cc:Subject:Date:From; b=QgZ5tfMIqGFau4nNzCvsqcbXS4Qeth6Xu/MxBTR34OtX0oITanNZUiKgHXIvqx77P fQaFNIBsEdeCvzAXC02upYo+kSY/xuyAXeW2lsdTS8hxoFrVM5GxndNEPAtX/aw4Tt KnwljZzltunV6Ny+OKAKWV53igJoiXdaEmN5F+Fh2LD0rvnJP+P2QzvicHBozyQIHE I8Q/FwQib+OCJ9AvjKhAjqJ/eddzlgUQgnlepxSJebMcbQrxBw9dbJsLKolSWFjXW+ GDdSalz/bhjOvgYBYOjlPTMLsgXboLgljM3tRPgS0TmigorIOXePej19rLiLAyCkic T6Ob51Cv+YXQg== From: Nathan Chancellor To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org Cc: "H. Peter Anvin" , Nick Desaulniers , Tom Rix , Daniel Kolesa , linux-kernel@vger.kernel.org, patches@lists.linux.dev, llvm@lists.linux.dev, Nathan Chancellor , stable@vger.kernel.org Subject: [PATCH] x86/Kconfig: Fix CONFIG_CC_HAS_SANE_STACKPROTECTOR when cross compiling with clang Date: Fri, 17 Jun 2022 11:08:46 -0700 Message-Id: <20220617180845.2788442-1-nathan@kernel.org> X-Mailer: git-send-email 2.36.1 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Chimera Linux notes that CONFIG_CC_HAS_SANE_STACKPROTECTOR cannot be enabled when cross compiling an x86_64 kernel with clang, even though it does work when natively compiling. When building on aarch64: $ make -sj"$(nproc)" ARCH=x86_64 LLVM=1 defconfig $ grep STACKPROTECTOR .config When building on x86_64: $ make -sj"$(nproc)" ARCH=x86_64 LLVM=1 defconfig $ grep STACKPROTECTOR .config CONFIG_CC_HAS_SANE_STACKPROTECTOR=y CONFIG_HAVE_STACKPROTECTOR=y CONFIG_STACKPROTECTOR=y CONFIG_STACKPROTECTOR_STRONG=y When clang is invoked without a '--target' flag, code is generated for the default target, which is usually the host (it is configurable via cmake). As a result, the has-stack-protector scripts will generate code for the default target but check for x86 specific segment registers, which cannot succeed if the default target is not x86. $(CLANG_FLAGS) contains an explicit '--target' flag so pass that variable along to the has-stack-protector scripts so that the stack protector can be enabled when cross compiling with clang. The 32-bit stack protector cannot currently be enabled with clang, as it does not support '-mstack-protector-guard-symbol', so this results in no functional change for ARCH=i386 when cross compiling. Link: https://github.com/chimera-linux/cports/commit/0fb7e506d5f83fdf2104feb22cdac34934561226 Link: https://github.com/llvm/llvm-project/issues/48553 Signed-off-by: Nathan Chancellor --- Fixes: 2a61f4747eea ("stack-protector: test compiler capability in Kconfig and drop AUTO mode") might be appropriate; I am conflicted on fixes tags for problems that that arise due to use cases that were not considered at the time of a change, as it feels wrong to blame the commit for not looking far enough into the future where it might be common for people to have workstations running another architecture other than x86_64. Chimera appears to use a 5.15 kernel so a Cc: stable@vger.kernel.org might be nice but some maintainers are picky about that so I leave it up to you all. arch/x86/Kconfig | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index be0b95e51df6..076adde7ead9 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -391,8 +391,8 @@ config PGTABLE_LEVELS config CC_HAS_SANE_STACKPROTECTOR bool - default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC)) if 64BIT - default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC)) + default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC) $(CLANG_FLAGS)) if 64BIT + default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC) $(CLANG_FLAGS)) help We have to make sure stack protector is unconditionally disabled if the compiler produces broken code or if it does not let us control base-commit: b13baccc3850ca8b8cccbf8ed9912dbaa0fdf7f3 -- 2.36.1