From patchwork Mon May 18 17:43:46 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nathan Lynch X-Patchwork-Id: 6431061 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 43F91C0432 for ; Mon, 18 May 2015 17:47:21 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 625F0204B0 for ; Mon, 18 May 2015 17:47:20 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.9]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 915512037F for ; Mon, 18 May 2015 17:47:19 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1YuP65-0007Fh-N6; Mon, 18 May 2015 17:45:01 +0000 Received: from relay1.mentorg.com ([192.94.38.131]) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1YuP5N-0006sV-O4 for linux-arm-kernel@lists.infradead.org; Mon, 18 May 2015 17:44:19 +0000 Received: from svr-orw-fem-05.mgc.mentorg.com ([147.34.97.43]) by relay1.mentorg.com with esmtp id 1YuP4y-0004Qg-Ar from Nathan_Lynch@mentor.com ; Mon, 18 May 2015 10:43:52 -0700 Received: from localhost (147.34.91.1) by svr-orw-fem-05.mgc.mentorg.com (147.34.97.43) with Microsoft SMTP Server (TLS) id 14.3.224.2; Mon, 18 May 2015 10:43:51 -0700 From: Nathan Lynch To: Subject: [PATCH 2/2] ARM: VDSO: force use of BFD linker Date: Mon, 18 May 2015 12:43:46 -0500 Message-ID: <1431971026-18317-3-git-send-email-nathan_lynch@mentor.com> X-Mailer: git-send-email 2.1.0 In-Reply-To: <1431971026-18317-1-git-send-email-nathan_lynch@mentor.com> References: <1431971026-18317-1-git-send-email-nathan_lynch@mentor.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20150518_104417_851131_BCDF585D X-CRM114-Status: GOOD ( 11.45 ) X-Spam-Score: -0.7 (/) Cc: Russell King , Stefan Agner X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Spam-Status: No, score=-4.2 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_MED, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP When using a toolchain with gold as the default linker, the VDSO build fails: VDSO arch/arm/vdso/vdso.so.raw HOSTCC arch/arm/vdso/vdsomunge MUNGE arch/arm/vdso/vdso.so.dbg OBJCOPY arch/arm/vdso/vdso.so BFD: arch/arm/vdso/vdso.so: Not enough room for program headers, try linking with -N For whatever reason, ld.gold is omitting an exidx program header that ld.bfd emits, and even when I work around that, I don't get a working VDSO. For now, instead of supporting gold (which will fail to link the kernel anyway since it does not implement --pic-veneer), direct the compiler to use the traditional bfd linker. This is accomplished by using -fuse-ld, which is implemented in GCC 4.8 and later. Note: one limitation of this is that if the toolchain is configured to use gold by default, and the bfd linker is not in $PATH, the VDSO build will fail: VDSO arch/arm/vdso/vdso.so.raw collect2: fatal error: cannot find 'ld' This will happen if CROSS_COMPILE begins with a path such as /opt/bin/arm-linux-gnu- but /opt/bin is not in $PATH. This is considered an acceptable corner-case limitation and is easily worked around. Additonal note: we use cc-option instead of cc-ldoption so that -fuse-ld=bfd is placed in the command line if the compiler recognizes the option. Using cc-ldoption results in an attempt to link, which fails in the situation just described, causing -fuse-ld=bfd to be omitted and gold to be used for the VDSO link, which is what we're trying to prevent. Reported-by: Stefan Agner Signed-off-by: Nathan Lynch --- arch/arm/vdso/Makefile | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/arm/vdso/Makefile b/arch/arm/vdso/Makefile index 89182ad44ee8..9d259d94e429 100644 --- a/arch/arm/vdso/Makefile +++ b/arch/arm/vdso/Makefile @@ -14,6 +14,7 @@ VDSO_LDFLAGS += -Wl,-z,max-page-size=4096 -Wl,-z,common-page-size=4096 VDSO_LDFLAGS += -nostdlib -shared VDSO_LDFLAGS += $(call cc-ldoption, -Wl$(comma)--hash-style=sysv) VDSO_LDFLAGS += $(call cc-ldoption, -Wl$(comma)--build-id) +VDSO_LDFLAGS += $(call cc-option, -fuse-ld=bfd) obj-$(CONFIG_VDSO) += vdso.o extra-$(CONFIG_VDSO) += vdso.lds