From patchwork Mon Aug 16 18:05:19 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sami Tolvanen X-Patchwork-Id: 12439015 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=-31.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT,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 6AFDAC4338F for ; Mon, 16 Aug 2021 18:05:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4213060EFF for ; Mon, 16 Aug 2021 18:05:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229755AbhHPSF4 (ORCPT ); Mon, 16 Aug 2021 14:05:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58908 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229481AbhHPSF4 (ORCPT ); Mon, 16 Aug 2021 14:05:56 -0400 Received: from mail-qt1-x849.google.com (mail-qt1-x849.google.com [IPv6:2607:f8b0:4864:20::849]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5A4D0C061764 for ; Mon, 16 Aug 2021 11:05:24 -0700 (PDT) Received: by mail-qt1-x849.google.com with SMTP id p21-20020ac846150000b02902982d999bfbso2890011qtn.7 for ; Mon, 16 Aug 2021 11:05:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:message-id:mime-version:subject:from:to:cc; bh=WUhrLDawJHutBQtlsVgOUTtq1I0JwrxuJFZxAOpOQh0=; b=SBIC7Krjh/VhBl5SaGxVCbuoUREHKzu6zDr3IjUFmXSUOuqfreRC/rZdLIE2r7E4VM BCVJp7rNhmur0M/Uc43eucOdLG8igCTSSDGwc6aDsD3AE1WT0GJECDeh4n6ViR7Ik8To GnBsBUPrp/MrQhIkshElrv4YCcYD1OjecIEsdS+hs9tk+5p2nGPznYmA2SvjL7d3/7Vs OVrQ1GuilvU0fZ+7TXjbWg1GpdPqgyqXqk3BD8+cckMBxeph/XaMrGRKTvQRo+QdI9jX 61veqXqnlf+uRhA5mPYH1A0cM+TcDnou+aG1rPr6OEbr3NPC1nH7Ep5MJYzo7O1HGgJ0 AabQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=WUhrLDawJHutBQtlsVgOUTtq1I0JwrxuJFZxAOpOQh0=; b=eIYIhfVYQ6bOHF5bCv17lvI5KkpboCggnoRxihkp39bKMB2IFtqJHbNTGb3YIWF5T8 F7jVNTXFlFbAFvfADm4r+jVuqyQwN1yEA5yrdwpakyp/qspukNMnAZzVFPHmkY98E8+8 ILyKVXPC026CdMSB20Cx3b5cuqDei6k0waKroxwnl/ZvGVr576oDHw/gcloI6tVglTi3 y1Qh9/Q2ncg7WbRv+IF4PE/Ll6WiaQsyHYhEWBKTVEEXpDiZTPFkQ6tNNUxUZ53z4WTz t8FyvXlzp/xAVmJNhdXj01ZqHTme+157eyRNv/CdJbHiJAP6o4YbST6pz44MvFF+WR2K kbMA== X-Gm-Message-State: AOAM531kw2ZtKU6VHCPKJ3ORJa/P33t7YnEwewxZ3kYr90c4YOwADCkP zT6NxQYSqAmKX3o5gVlTkpvcLoHQmQKBFNDHPVQ= X-Google-Smtp-Source: ABdhPJxhKkwy4tIJBPi81JnMtRw9ItdUQCqEs3lJya95irvVe6M8or+msF0I1n8xF4YguHAVXtFyEmeRO47qpZRCe/w= X-Received: from samitolvanen1.mtv.corp.google.com ([2620:15c:201:2:5676:2fb8:7851:2301]) (user=samitolvanen job=sendgmr) by 2002:a05:6214:892:: with SMTP id cz18mr17100881qvb.60.1629137122793; Mon, 16 Aug 2021 11:05:22 -0700 (PDT) Date: Mon, 16 Aug 2021 11:05:19 -0700 Message-Id: <20210816180519.1021311-1-samitolvanen@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.33.0.rc1.237.g0d66db33f3-goog Subject: [PATCH v4] kbuild: Fix TRIM_UNUSED_KSYMS with LTO_CLANG From: Sami Tolvanen To: Kees Cook , Masahiro Yamada , Michal Marek Cc: Alexander Lobakin , Nathan Chancellor , Nick Desaulniers , linux-kbuild@vger.kernel.org, clang-built-linux@googlegroups.com, linux-kernel@vger.kernel.org, Sami Tolvanen Precedence: bulk List-ID: X-Mailing-List: linux-kbuild@vger.kernel.org With CONFIG_LTO_CLANG, we currently link modules into native code just before modpost, which means with TRIM_UNUSED_KSYMS enabled, we still look at the LLVM bitcode in the .o files when generating the list of used symbols. As the bitcode doesn't yet have calls to compiler intrinsics and llvm-nm doesn't see function references that only exist in function-level inline assembly, we currently need a whitelist for TRIM_UNUSED_KSYMS to work with LTO. This change moves module LTO linking to happen earlier, and thus avoids the issue with LLVM bitcode and TRIM_UNUSED_KSYMS entirely, allowing us to also drop the whitelist from gen_autoksyms.sh. Link: https://github.com/ClangBuiltLinux/linux/issues/1369 Signed-off-by: Sami Tolvanen Reviewed-by: Alexander Lobakin Tested-by: Alexander Lobakin --- Changes in v4: - Added .lto.o to targets to actually fix the use of if_changed. - Replaced an unnecessary mod-prelink-ext with .lto. Changes in v3: - Added missing FORCE. Changes in v2: - Fixed a couple of typos. - Fixed objtool arguments for .lto.o to always include --module. --- scripts/Makefile.build | 28 +++++++++++++++++++++++++++- scripts/Makefile.lib | 7 +++++++ scripts/Makefile.modfinal | 21 ++------------------- scripts/Makefile.modpost | 22 +++------------------- scripts/gen_autoksyms.sh | 12 ------------ 5 files changed, 39 insertions(+), 51 deletions(-) base-commit: a2824f19e6065a0d3735acd9fe7155b104e7edf5 diff --git a/scripts/Makefile.build b/scripts/Makefile.build index 02197cb8e3a7..a6f43afd09bb 100644 --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -88,6 +88,10 @@ endif targets-for-modules := $(patsubst %.o, %.mod, $(filter %.o, $(obj-m))) +ifdef CONFIG_LTO_CLANG +targets-for-modules += $(patsubst %.o, %.lto.o, $(filter %.o, $(obj-m))) +endif + ifdef need-modorder targets-for-modules += $(obj)/modules.order endif @@ -271,12 +275,34 @@ $(obj)/%.o: $(src)/%.c $(recordmcount_source) $$(objtool_dep) FORCE $(call if_changed_rule,cc_o_c) $(call cmd,force_checksrc) +ifdef CONFIG_LTO_CLANG +# Module .o files may contain LLVM bitcode, compile them into native code +# before ELF processing +quiet_cmd_cc_lto_link_modules = LTO [M] $@ +cmd_cc_lto_link_modules = \ + $(LD) $(ld_flags) -r -o $@ \ + $(shell [ -s $(@:.lto.o=.o.symversions) ] && \ + echo -T $(@:.lto.o=.o.symversions)) \ + --whole-archive $(filter-out FORCE,$^) + +ifdef CONFIG_STACK_VALIDATION +# objtool was skipped for LLVM bitcode, run it now that we have compiled +# modules into native code +cmd_cc_lto_link_modules += ; \ + $(objtree)/tools/objtool/objtool $(objtool_args) --module \ + $(@:.ko=.lto.o) +endif + +$(obj)/%.lto.o: $(obj)/%.o FORCE + $(call if_changed,cc_lto_link_modules) +endif + cmd_mod = { \ echo $(if $($*-objs)$($*-y)$($*-m), $(addprefix $(obj)/, $($*-objs) $($*-y) $($*-m)), $(@:.mod=.o)); \ $(undefined_syms) echo; \ } > $@ -$(obj)/%.mod: $(obj)/%.o FORCE +$(obj)/%.mod: $(obj)/%$(mod-prelink-ext).o FORCE $(call if_changed,mod) quiet_cmd_cc_lst_c = MKLST $@ diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib index 10950559b223..af1c920a585c 100644 --- a/scripts/Makefile.lib +++ b/scripts/Makefile.lib @@ -225,6 +225,13 @@ dtc_cpp_flags = -Wp,-MMD,$(depfile).pre.tmp -nostdinc \ $(addprefix -I,$(DTC_INCLUDE)) \ -undef -D__DTS__ +ifeq ($(CONFIG_LTO_CLANG),y) +# With CONFIG_LTO_CLANG, .o files in modules might be LLVM bitcode, so we +# need to run LTO to compile them into native code (.lto.o) before further +# processing. +mod-prelink-ext := .lto +endif + # Objtool arguments are also needed for modfinal with LTO, so we define # then here to avoid duplication. objtool_args = \ diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal index 5e9b8057fb24..ff805777431c 100644 --- a/scripts/Makefile.modfinal +++ b/scripts/Makefile.modfinal @@ -9,7 +9,7 @@ __modfinal: include include/config/auto.conf include $(srctree)/scripts/Kbuild.include -# for c_flags and objtool_args +# for c_flags and mod-prelink-ext include $(srctree)/scripts/Makefile.lib # find all modules listed in modules.order @@ -30,23 +30,6 @@ quiet_cmd_cc_o_c = CC [M] $@ ARCH_POSTLINK := $(wildcard $(srctree)/arch/$(SRCARCH)/Makefile.postlink) -ifdef CONFIG_LTO_CLANG -# With CONFIG_LTO_CLANG, reuse the object file we compiled for modpost to -# avoid a second slow LTO link -prelink-ext := .lto - -# ELF processing was skipped earlier because we didn't have native code, -# so let's now process the prelinked binary before we link the module. - -ifdef CONFIG_STACK_VALIDATION -cmd_ld_ko_o += \ - $(objtree)/tools/objtool/objtool $(objtool_args) \ - $(@:.ko=$(prelink-ext).o); - -endif # CONFIG_STACK_VALIDATION - -endif # CONFIG_LTO_CLANG - quiet_cmd_ld_ko_o = LD [M] $@ cmd_ld_ko_o += \ $(LD) -r $(KBUILD_LDFLAGS) \ @@ -72,7 +55,7 @@ if_changed_except = $(if $(call newer_prereqs_except,$(2))$(cmd-check), \ # Re-generate module BTFs if either module's .ko or vmlinux changed -$(modules): %.ko: %$(prelink-ext).o %.mod.o scripts/module.lds $(if $(KBUILD_BUILTIN),vmlinux) FORCE +$(modules): %.ko: %$(mod-prelink-ext).o %.mod.o scripts/module.lds $(if $(KBUILD_BUILTIN),vmlinux) FORCE +$(call if_changed_except,ld_ko_o,vmlinux) ifdef CONFIG_DEBUG_INFO_BTF_MODULES +$(if $(newer-prereqs),$(call cmd,btf_ko)) diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost index c383ba33d837..eef56d629799 100644 --- a/scripts/Makefile.modpost +++ b/scripts/Makefile.modpost @@ -41,7 +41,7 @@ __modpost: include include/config/auto.conf include $(srctree)/scripts/Kbuild.include -# for ld_flags +# for mod-prelink-ext include $(srctree)/scripts/Makefile.lib MODPOST = scripts/mod/modpost \ @@ -118,22 +118,6 @@ $(input-symdump): @echo >&2 ' Modules may not have dependencies or modversions.' @echo >&2 ' You may get many unresolved symbol warnings.' -ifdef CONFIG_LTO_CLANG -# With CONFIG_LTO_CLANG, .o files might be LLVM bitcode, so we need to run -# LTO to compile them into native code before running modpost -prelink-ext := .lto - -quiet_cmd_cc_lto_link_modules = LTO [M] $@ -cmd_cc_lto_link_modules = \ - $(LD) $(ld_flags) -r -o $@ \ - $(shell [ -s $(@:.lto.o=.o.symversions) ] && \ - echo -T $(@:.lto.o=.o.symversions)) \ - --whole-archive $^ - -%.lto.o: %.o - $(call if_changed,cc_lto_link_modules) -endif - modules := $(sort $(shell cat $(MODORDER))) # KBUILD_MODPOST_WARN can be set to avoid error out in case of undefined symbols @@ -144,9 +128,9 @@ endif # Read out modules.order to pass in modpost. # Otherwise, allmodconfig would fail with "Argument list too long". quiet_cmd_modpost = MODPOST $@ - cmd_modpost = sed 's/\.ko$$/$(prelink-ext)\.o/' $< | $(MODPOST) -T - + cmd_modpost = sed 's/\.ko$$/$(mod-prelink-ext)\.o/' $< | $(MODPOST) -T - -$(output-symdump): $(MODORDER) $(input-symdump) $(modules:.ko=$(prelink-ext).o) FORCE +$(output-symdump): $(MODORDER) $(input-symdump) $(modules:.ko=$(mod-prelink-ext).o) FORCE $(call if_changed,modpost) targets += $(output-symdump) diff --git a/scripts/gen_autoksyms.sh b/scripts/gen_autoksyms.sh index da320151e7c3..6ed0d225c8b1 100755 --- a/scripts/gen_autoksyms.sh +++ b/scripts/gen_autoksyms.sh @@ -26,18 +26,6 @@ if [ -n "$CONFIG_MODVERSIONS" ]; then needed_symbols="$needed_symbols module_layout" fi -# With CONFIG_LTO_CLANG, LLVM bitcode has not yet been compiled into a binary -# when the .mod files are generated, which means they don't yet contain -# references to certain symbols that will be present in the final binaries. -if [ -n "$CONFIG_LTO_CLANG" ]; then - # intrinsic functions - needed_symbols="$needed_symbols memcpy memmove memset" - # ftrace - needed_symbols="$needed_symbols _mcount" - # stack protector symbols - needed_symbols="$needed_symbols __stack_chk_fail __stack_chk_guard" -fi - ksym_wl= if [ -n "$CONFIG_UNUSED_KSYMS_WHITELIST" ]; then # Use 'eval' to expand the whitelist path and check if it is relative