From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D50CDC433E0 for ; Tue, 23 Jun 2020 17:42:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AE8A6206D4 for ; Tue, 23 Jun 2020 17:42:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592934173; bh=/yIniaPFKZ11CTcjGIIKnnQplSH1xgEGXA3jO9oQshA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=c4jwhQAvy/MwFDNlbzbDUcrlWmcbVk4xexuC8yPBoCQVZng05IsIe55Do/YmEQx0e +UHkRarfNQ0INipwkRDgp3ySKoRylCHlArPXxhm4DAuqZmq3QS9/W6nYMMJyuevqXY 33FsxBsPU1y+6tS5Eg2E9myU/g3FkAH2Vkku2tic= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387415AbgFWRfw (ORCPT ); Tue, 23 Jun 2020 13:35:52 -0400 Received: from mail.kernel.org ([198.145.29.99]:60480 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1733287AbgFWRfs (ORCPT ); Tue, 23 Jun 2020 13:35:48 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 0334620706; Tue, 23 Jun 2020 17:35:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592933747; bh=/yIniaPFKZ11CTcjGIIKnnQplSH1xgEGXA3jO9oQshA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=BCLGyQzulP+rba8iBPtCzR8hBnaW4BT8iFTyZ8R4xxZypeAzGPKweLD4LhnrLjx0o c3wRE171kX5YMr1+n2D0j2FxDx+leggM8BL1z5q3msOpm3fez4gwcgwSN60ITzAfy8 Xypu6YI7zoa2qT2wnsg55AlsUu/P25CzaKAeR90s= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Nathan Chancellor , Nick Desaulniers , Heiko Carstens , Vasily Gorbik , Sasha Levin , linux-s390@vger.kernel.org, clang-built-linux@googlegroups.com Subject: [PATCH AUTOSEL 5.7 19/28] s390/vdso: Use $(LD) instead of $(CC) to link vDSO Date: Tue, 23 Jun 2020 13:35:14 -0400 Message-Id: <20200623173523.1355411-19-sashal@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200623173523.1355411-1-sashal@kernel.org> References: <20200623173523.1355411-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Nathan Chancellor [ Upstream commit 2b2a25845d534ac6d55086e35c033961fdd83a26 ] Currently, the VDSO is being linked through $(CC). This does not match how the rest of the kernel links objects, which is through the $(LD) variable. When clang is built in a default configuration, it first attempts to use the target triple's default linker, which is just ld. However, the user can override this through the CLANG_DEFAULT_LINKER cmake define so that clang uses another linker by default, such as LLVM's own linker, ld.lld. This can be useful to get more optimized links across various different projects. However, this is problematic for the s390 vDSO because ld.lld does not have any s390 emulatiom support: https://github.com/llvm/llvm-project/blob/llvmorg-10.0.1-rc1/lld/ELF/Driver.cpp#L132-L150 Thus, if a user is using a toolchain with ld.lld as the default, they will see an error, even if they have specified ld.bfd through the LD make variable: $ make -j"$(nproc)" -s ARCH=s390 CROSS_COMPILE=s390x-linux-gnu- LLVM=1 \ LD=s390x-linux-gnu-ld \ defconfig arch/s390/kernel/vdso64/ ld.lld: error: unknown emulation: elf64_s390 clang-11: error: linker command failed with exit code 1 (use -v to see invocation) Normally, '-fuse-ld=bfd' could be used to get around this; however, this can be fragile, depending on paths and variable naming. The cleaner solution for the kernel is to take advantage of the fact that $(LD) can be invoked directly, which bypasses the heuristics of $(CC) and respects the user's choice. Similar changes have been done for ARM, ARM64, and MIPS. Link: https://lkml.kernel.org/r/20200602192523.32758-1-natechancellor@gmail.com Link: https://github.com/ClangBuiltLinux/linux/issues/1041 Signed-off-by: Nathan Chancellor Reviewed-by: Nick Desaulniers [heiko.carstens@de.ibm.com: add --build-id flag] Signed-off-by: Heiko Carstens Signed-off-by: Vasily Gorbik Signed-off-by: Sasha Levin --- arch/s390/kernel/vdso64/Makefile | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) diff --git a/arch/s390/kernel/vdso64/Makefile b/arch/s390/kernel/vdso64/Makefile index bec19e7e6e1cf..4a66a1cb919b1 100644 --- a/arch/s390/kernel/vdso64/Makefile +++ b/arch/s390/kernel/vdso64/Makefile @@ -18,8 +18,8 @@ KBUILD_AFLAGS_64 += -m64 -s KBUILD_CFLAGS_64 := $(filter-out -m64,$(KBUILD_CFLAGS)) KBUILD_CFLAGS_64 += -m64 -fPIC -shared -fno-common -fno-builtin -KBUILD_CFLAGS_64 += -nostdlib -Wl,-soname=linux-vdso64.so.1 \ - -Wl,--hash-style=both +ldflags-y := -fPIC -shared -nostdlib -soname=linux-vdso64.so.1 \ + --hash-style=both --build-id -T $(targets:%=$(obj)/%.dbg): KBUILD_CFLAGS = $(KBUILD_CFLAGS_64) $(targets:%=$(obj)/%.dbg): KBUILD_AFLAGS = $(KBUILD_AFLAGS_64) @@ -37,8 +37,8 @@ KASAN_SANITIZE := n $(obj)/vdso64_wrapper.o : $(obj)/vdso64.so # link rule for the .so file, .lds has to be first -$(obj)/vdso64.so.dbg: $(src)/vdso64.lds $(obj-vdso64) FORCE - $(call if_changed,vdso64ld) +$(obj)/vdso64.so.dbg: $(obj)/vdso64.lds $(obj-vdso64) FORCE + $(call if_changed,ld) # strip rule for the .so file $(obj)/%.so: OBJCOPYFLAGS := -S @@ -50,8 +50,6 @@ $(obj-vdso64): %.o: %.S FORCE $(call if_changed_dep,vdso64as) # actual build commands -quiet_cmd_vdso64ld = VDSO64L $@ - cmd_vdso64ld = $(CC) $(c_flags) -Wl,-T $(filter %.lds %.o,$^) -o $@ quiet_cmd_vdso64as = VDSO64A $@ cmd_vdso64as = $(CC) $(a_flags) -c -o $@ $< -- 2.25.1