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=-17.4 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_IN_DEF_DKIM_WL 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 4560BC433E7 for ; Mon, 19 Oct 2020 20:41:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D9218223FB for ; Mon, 19 Oct 2020 20:41:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="uNbz+HXM" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728082AbgJSUl0 (ORCPT ); Mon, 19 Oct 2020 16:41:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43696 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726652AbgJSUl0 (ORCPT ); Mon, 19 Oct 2020 16:41:26 -0400 Received: from mail-pl1-x641.google.com (mail-pl1-x641.google.com [IPv6:2607:f8b0:4864:20::641]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 69BA5C0613CE for ; Mon, 19 Oct 2020 13:41:25 -0700 (PDT) Received: by mail-pl1-x641.google.com with SMTP id h2so401151pll.11 for ; Mon, 19 Oct 2020 13:41:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=JV8BCOR/JvIEgfAvAo8m2P/XD4M4pARgj8lS/n0TjIk=; b=uNbz+HXMdeKg8jx/VsmQdREfkupFzXXiUBqaLappY65JtKYFoPb02aQCNgYKytpnRa M396faW0CziT/V/gWsiPlV2oxg5+TCszht6nGulgvEzuzCjXGlWD/k1xiJYF/9gEY/98 YAv7E+lfusXSm7++KVAdBsjvONGpbfWfrOAbPzodtlkW9LQeHluOXN9T8yuRJ/bVW7+a guDFG/jLk1fXusgiI8hfPZ+NBM7sW/Crnqo8yLhkIjfBYMLoADYBf/VRrJPJoFhhk1E+ baqIydOxf+DxyjCXRyAMIMj4DUJ1BLK9CzW/vBSKkRzefBcUNgysgnsUnvmUdYIkzNgL rB0w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=JV8BCOR/JvIEgfAvAo8m2P/XD4M4pARgj8lS/n0TjIk=; b=BIZKwOwGzYVQAOrim7BbO8oJk68sB4YjiNsc9OR9mhJABZ/beBoo7Xask8Mbi0PJx0 PU4kvO9xlrqtfOZEoB17XD1DW9FiTyw+CI5jVLA90HSJ1F4GMZPaMqQezyciNvP1wFO6 ElpJm/1lZOkEZ+jxLz+k7dnvV9lUIH3stxBqMwBVzJlAbwMTpYPgiGKxwmTMkR3uM79M 8FfjdnKbzm910COmAyjWY+kJ5cXbQ6pgXMs7LvVmnkxePqVcVr9EWo+UtxK7tChC1WBE HiBz4hqyBKI8B59RsXumSpr0iUbcrzD/dq79uqqYGrJj55hiLWrxwV70bjhznwkTuMkH r54Q== X-Gm-Message-State: AOAM530POujOse9Lxlbw57EcfidjIRTSNckojR6u7F6qtifexB5zCZ4Y SVmB7xNfCJCUbZHJBCPAnU6Ohw== X-Google-Smtp-Source: ABdhPJwzigGcHkEMr7039MyLZ5jq7OIo2twqHHs2AypjQ9JDtzez1a+8+fTks+4Hc7xtn2V3terA0w== X-Received: by 2002:a17:90a:ff92:: with SMTP id hf18mr1202895pjb.171.1603140084574; Mon, 19 Oct 2020 13:41:24 -0700 (PDT) Received: from google.com ([2620:15c:2ce:0:a6ae:11ff:fe11:4abb]) by smtp.gmail.com with ESMTPSA id o4sm319396pjp.37.2020.10.19.13.41.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 19 Oct 2020 13:41:23 -0700 (PDT) Date: Mon, 19 Oct 2020 13:41:21 -0700 From: Fangrui Song To: Palmer Dabbelt Cc: Nick Desaulniers , linux-riscv@lists.infradead.org, kernel-team , "# 3.4.x" , clang-built-linux Subject: Re: [PATCH] RISC-V: Fix the VDSO symbol generaton for binutils-2.34+ Message-ID: <20201019204121.jaw7mqn4bkn2h6mx@google.com> References: <20201017002500.503011-1-palmerdabbelt@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On 2020-10-19, 'Nick Desaulniers' via Clang Built Linux wrote: >On Fri, Oct 16, 2020 at 5:44 PM 'Palmer Dabbelt' via Clang Built Linux > wrote: >> >> We were relying on GNU ld's ability to re-link executable files in order >> to extract our VDSO symbols. This behavior was deemed a bug as of >> binutils-2.34 (specifically the binutils-gdb commit a87e1817a4 ("Have >> the linker fail if any attempt to link in an executable is made."), >> which IIUC landed in 2.34), which recently installed itself on my build >> setup. I filed the issue https://sourceware.org/bugzilla/show_bug.cgi?id=26047 The commit is in 2.35 but not in the released 2.34 branch. >> The previous version of this was a bit of a mess: we were linking a >> static executable version of the VDSO, containing only a subset of the >> input symbols, which we then linked into the kernel. This worked, but >> certainly wasn't a supported path through the toolchain. Instead this >> new version parses the textual output of nm to produce a symbol table. >> Both rely on near-zero addresses being linkable, but as we rely on weak >> undefined symbols being linkable elsewhere I don't view this as a major >> issue. >> >> Fixes: e2c0cdfba7f6 ("RISC-V: User-facing API") >> Cc: stable@vger.kernel.org >> Cc: clang-built-linux@googlegroups.com >> Signed-off-by: Palmer Dabbelt > >Ah, I do see a build failure to link the vdso with: >$ riscv64-linux-gnu-ld --version >GNU ld (GNU Binutils for Debian) 2.34.90.20200706 > >riscv64-linux-gnu-ld: cannot use executable file >'arch/riscv/kernel/vdso/vdso-dummy.o' as input to a link > >This patch fixes that for me, but there's a problem related to related >to `nm` below. > >After this, there's two other things we might want to fix up related >to the build of the vdso: >1. it looks like $(CC) is being used to link the vdso, rather than >$(LD). While it's generally fine to use the compiler as the driver >for building a linked object file, it does not respect the set $(LD). >`-fuse-ld=` needs to be passed to invoke the linker the user >specified. See also: >https://lore.kernel.org/linux-kbuild/20201013033947.2257501-1-natechancellor@gmail.com/T/#u >(this has popped up in a few places when trying to do hermetic builds >with LLD). >2. I observe the warning when building with clang: `argument unused >during compilation: '-no-pie' [-Wunused-command-line-argument]`. IIRC, >the top level Makefile sets `-Qunused-arguments` for builds with >clang. `cmd_vdsold` may need that, but it's curious why it's unused >and makes me wonder why/if `-no-pie` is necessary? That also might be >fixed by fixing 1. > >> --- >> arch/riscv/kernel/vdso/.gitignore | 1 + >> arch/riscv/kernel/vdso/Makefile | 19 +++++++++---------- >> arch/riscv/kernel/vdso/so2s.sh | 7 +++++++ >> 3 files changed, 17 insertions(+), 10 deletions(-) >> create mode 100755 arch/riscv/kernel/vdso/so2s.sh >> >> diff --git a/arch/riscv/kernel/vdso/.gitignore b/arch/riscv/kernel/vdso/.gitignore >> index 11ebee9e4c1d..3a19def868ec 100644 >> --- a/arch/riscv/kernel/vdso/.gitignore >> +++ b/arch/riscv/kernel/vdso/.gitignore >> @@ -1,3 +1,4 @@ >> # SPDX-License-Identifier: GPL-2.0-only >> vdso.lds >> *.tmp >> +vdso-syms.S >> diff --git a/arch/riscv/kernel/vdso/Makefile b/arch/riscv/kernel/vdso/Makefile >> index 478e7338ddc1..2e02958f6224 100644 >> --- a/arch/riscv/kernel/vdso/Makefile >> +++ b/arch/riscv/kernel/vdso/Makefile >> @@ -43,19 +43,14 @@ $(obj)/vdso.o: $(obj)/vdso.so >> SYSCFLAGS_vdso.so.dbg = $(c_flags) >> $(obj)/vdso.so.dbg: $(src)/vdso.lds $(obj-vdso) FORCE >> $(call if_changed,vdsold) >> +SYSCFLAGS_vdso.so.dbg = -shared -s -Wl,-soname=linux-vdso.so.1 \ >> + -Wl,--build-id -Wl,--hash-style=both >> >> # We also create a special relocatable object that should mirror the symbol >> # table and layout of the linked DSO. With ld --just-symbols we can then >> # refer to these symbols in the kernel code rather than hand-coded addresses. >> - >> -SYSCFLAGS_vdso.so.dbg = -shared -s -Wl,-soname=linux-vdso.so.1 \ >> - -Wl,--build-id -Wl,--hash-style=both >> -$(obj)/vdso-dummy.o: $(src)/vdso.lds $(obj)/rt_sigreturn.o FORCE >> - $(call if_changed,vdsold) >> - >> -LDFLAGS_vdso-syms.o := -r --just-symbols >> -$(obj)/vdso-syms.o: $(obj)/vdso-dummy.o FORCE >> - $(call if_changed,ld) >> +$(obj)/vdso-syms.S: $(obj)/vdso.so FORCE >> + $(call if_changed,so2s) >> >> # strip rule for the .so file >> $(obj)/%.so: OBJCOPYFLAGS := -S >> @@ -68,11 +63,15 @@ $(obj)/%.so: $(obj)/%.so.dbg FORCE >> # Make sure only to export the intended __vdso_xxx symbol offsets. >> quiet_cmd_vdsold = VDSOLD $@ >> cmd_vdsold = $(CC) $(KBUILD_CFLAGS) $(call cc-option, -no-pie) -nostdlib -nostartfiles $(SYSCFLAGS_$(@F)) \ >> - -Wl,-T,$(filter-out FORCE,$^) -o $@.tmp && \ >> + -Wl,-T,$(filter-out FORCE,$^) -o $@.tmp -Wl,-Map,$@.map && \ Is -Wl,-Map,$@.map needed? >> $(CROSS_COMPILE)objcopy \ >> $(patsubst %, -G __vdso_%, $(vdso-syms)) $@.tmp $@ && \ >> rm $@.tmp >> >> +# Extracts >> +quiet_cmd_so2s = SO2S $@ >> + cmd_so2s = $(CROSS_COMPILE)nm -D $< | $(src)/so2s.sh > $@ > >This should use `$(NM)` rather than `$(CROSS_COMPILE)nm` which >hardcodes the use of GNU nm from GNU binutils. > >> + >> # install commands for the unstripped file >> quiet_cmd_vdso_install = INSTALL $@ >> cmd_vdso_install = cp $(obj)/$@.dbg $(MODLIB)/vdso/$@ >> diff --git a/arch/riscv/kernel/vdso/so2s.sh b/arch/riscv/kernel/vdso/so2s.sh >> new file mode 100755 >> index 000000000000..7862866b5ebb >> --- /dev/null >> +++ b/arch/riscv/kernel/vdso/so2s.sh >> @@ -0,0 +1,6 @@ >> +#!/bin/sh >> +# SPDX-License-Identifier: GPL-2.0+ >> +# Copyright 2020 Palmer Dabbelt >> + >> +sed 's!\([0-9a-f]*\) T \([a-z0-9_]*\)@@LINUX_4.15!.global \2\n.set \2,0x\1!' \ >> +| grep '^\.' >> -- > >-- >Thanks, >~Nick Desaulniers > >-- >You received this message because you are subscribed to the Google Groups "Clang Built Linux" group. >To unsubscribe from this group and stop receiving emails from it, send an email to clang-built-linux+unsubscribe@googlegroups.com. >To view this discussion on the web visit https://groups.google.com/d/msgid/clang-built-linux/CAKwvOdnsRHA1WMb7OWi-jV662xLrBBBZ%3DzBbB1gvfpBqVFeSfQ%40mail.gmail.com.