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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 70B74C433EF for ; Fri, 28 Jan 2022 03:15:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345660AbiA1DPz (ORCPT ); Thu, 27 Jan 2022 22:15:55 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57514 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242230AbiA1DPz (ORCPT ); Thu, 27 Jan 2022 22:15:55 -0500 Received: from mail-pf1-x42e.google.com (mail-pf1-x42e.google.com [IPv6:2607:f8b0:4864:20::42e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 55482C061714 for ; Thu, 27 Jan 2022 19:15:54 -0800 (PST) Received: by mail-pf1-x42e.google.com with SMTP id i186so2398357pfe.0 for ; Thu, 27 Jan 2022 19:15:54 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=tZcF1ys+J7GpUFASVAGN6Rdu8oCjA7Z3iypwWHCPy8A=; b=gqxpQ0nasANrfgltMjn/UOliGsx/M5Umfd72JjWUW0y8yKFeSco7vy+1wCHMAW8xnj Dcc2akETfd1yWkgWkbHsmV4FRnqHHC6nH2MVji2noPC3VA6GbnL3SKJkJFmt6fM7P1h9 SgywbWj6wiGSforGMZ4BA2Ag8qiZh7AWGguN1PI4J+7OVcxbRMohccvA4b9B7h2rJF80 n6oz9z2dgmg81U1o2W7CUFLc2Lt4TR4+pPta3CODTyEpseDhGifE1unpNCShesZFbkwp 4iwc8gaO/cwNpI85QYa0I5hySL7VCDHegj1wOE8dwq6cClnRcUG52qBBpNvho3B2dOJG Su2Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=tZcF1ys+J7GpUFASVAGN6Rdu8oCjA7Z3iypwWHCPy8A=; b=JE1CQkDbIEnyhkpA0CQeOwyd5M8uZfDC1JYZP/snxsDj7AE/8YrPpALN6UK78SAlQN 4fcO69/l30Fc6MuIw2pyfTRYmaNN7sKanBMF5MxSJNjxuSPmiq3ayn6HZiZ03nzAMMY5 Ash1COYKiU4WaxVsNRRuRGSHgIFJv3nCPFVaneaBpLffcXGX+8x8DpuD6kItJWRN6lgV gdbEtQKqtYytp8LhAqa7Ggir3jwM0d6ogiXYQ6KVkh9U0MdtQwh3ruGW8vftCSBS4uKr pSgODOogU3F9V4Ie+w7ft5B9SxLGrHA9hj7EOyT3HBZfK2gBOhI6b0cl/jYEL8muf0pc j0Yw== X-Gm-Message-State: AOAM5305apbe8cazRN7vwTjvR0g3QiqLXFfwR0Yx3Xkn8WH4kIvGzffI i6SzQUsFQQLEAZZ7/po5FcOx/Q== X-Google-Smtp-Source: ABdhPJyyOfTrUzr+qvId4zhmjXJ6JWJJMgPDTtPVeTnXiqVP6kUN+6+UkWJsa3wtypi+dlPGwh7JYQ== X-Received: by 2002:a63:3d0a:: with SMTP id k10mr5055355pga.179.1643339753623; Thu, 27 Jan 2022 19:15:53 -0800 (PST) Received: from google.com ([2620:15c:2ce:200:e361:f314:a42:f5f8]) by smtp.gmail.com with ESMTPSA id j18sm7353848pfj.13.2022.01.27.19.15.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 27 Jan 2022 19:15:53 -0800 (PST) Date: Thu, 27 Jan 2022 19:15:49 -0800 From: Fangrui Song To: Nick Desaulniers Cc: Elliot Berman , Masahiro Yamada , Michal Marek , Nathan Chancellor , Matthias Maennich , linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev Subject: Re: [PATCH] kbuild: Add environment variables for userprogs flags Message-ID: <20220128031549.w5a4bilxbkppagfu@google.com> References: <20220112224342.958358-1-quic_eberman@quicinc.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: linux-kernel@vger.kernel.org On 2022-01-26, Nick Desaulniers wrote: >On Wed, Jan 12, 2022 at 2:44 PM Elliot Berman wrote: >> >> Allow additional arguments be passed to userprogs compilation. >> Reproducible clang builds need to provide a sysroot and gcc path to >> ensure same toolchain is used across hosts. KCFLAGS is not currently >> used for any user programs compilation, so add new USERCFLAGS and >> USERLDFLAGS which serves similar purpose as HOSTCFLAGS/HOSTLDFLAGS. >> >> Specifically, I'm trying to force CC_CAN_LINK to consistently fail in >> an environment where a user sysroot is not specifically available. >> Currently, Clang might automatically detect GCC installation on hosts >> which have it installed to a default location in /. With addition of >> these environment variables, our build environment can do like >> "--sysroot=/dev/null" to force sysroot detection to fail. > >Hi Elliot, >Thanks for the patch! Sorry for the delay in reviewing; I didn't quite >get around to it then went on vacation for a week. Things get buried >in my inbox quickly; feel free to ping me if a week goes by with no >response on whichever channel works best for you. > >I'm happy with the intent of this patch; GNU binutils has been removed >from Android, so supporting CC_CAN_LINK for Android kernel builds has >been a question I've been thinking about (though, not with higher >priority with some of our other issues), since we'll need to either >incorporate musl or bionic libc into our kernel build. I was thinking >of adding a SYSROOT command line variable for that, but I see your >approach is more flexible. > >One minor nit below, a typo, a few questions, and in the commit >message, but this generally LGTM. > >For the commit message, I think it would be good to expand `can do >like "--sysroot=/dev/null"` fully into >``` >can specify >$ make USERCFLAGS=--sysroot=/dev/null USERLDFLAGS=-Wl,--sysroot=/dev/null >``` Is -Wl,--sysroot=/dev/null to override a -Wl,--sysroot specified previously on the command line? The driver option --sysroot does two things: * Decide include/library search paths (e.g. $sysroot/usr/include, $sysroot/lib64). * Pass --sysroot to ld. In ld, it means: if a linker script is in the sysroot directory, when ld opens an absolute path file (via INPUT or GROUP), add sysroot before the absolute path. In ld, --sysroot=/dev/null is not different --sysroot= (empty value). >> >> Signed-off-by: Elliot Berman >> --- >> Documentation/kbuild/kbuild.rst | 8 ++++++++ >> Makefile | 9 ++++++--- >> init/Kconfig | 8 ++++---- >> usr/include/Makefile | 3 +++ >> 4 files changed, 21 insertions(+), 7 deletions(-) >> >> diff --git a/Documentation/kbuild/kbuild.rst b/Documentation/kbuild/kbuild.rst >> index 2d1fc03d346e..16e90a3ae01b 100644 >> --- a/Documentation/kbuild/kbuild.rst >> +++ b/Documentation/kbuild/kbuild.rst >> @@ -77,6 +77,14 @@ HOSTLDLIBS >> ---------- >> Additional libraries to link against when building host programs. >> >> +USERCFLAGS >> +---------- >> +Additional options used for $(CC) when compiling userprogs. >> + >> +USERLDFLAGS >> +---------- >> +Additional options used for $(LD) when linking userprogs. > >Probably should note the necessity of `-Wl,` prefixes here. > >Is `userprogs` cannonical? Yeah, I guess (reading >Documentation/kbuild/makefiles.rst). I wonder if we should mention >these in Documentation/kbuild/makefiles.rst as well? Under `5.3 >Controlling compiler options for userspace programs`. > >> + >> KBUILD_KCONFIG >> -------------- >> Set the top-level Kconfig file to the value of this environment >> diff --git a/Makefile b/Makefile >> index 45278d508d81..4a55537c8ca0 100644 >> --- a/Makefile >> +++ b/Makefile >> @@ -431,15 +431,17 @@ HOSTCC = gcc >> HOSTCXX = g++ >> endif >> >> -export KBUILD_USERCFLAGS := -Wall -Wmissing-prototypes -Wstrict-prototypes \ >> - -O2 -fomit-frame-pointer -std=gnu89 >> -export KBUILD_USERLDFLAGS := >> +KBUILD_USERCFLAGS := -Wall -Wmissing-prototypes -Wstrict-prototypes \ >> + -O2 -fomit-frame-pointer -std=gnu89 >> +KBUILD_USERLDFLAGS := $(USERLDFLAGGS) > >^ I think there's an extra G in USERLDFLAGS above. > >> >> KBUILD_HOSTCFLAGS := $(KBUILD_USERCFLAGS) $(HOST_LFS_CFLAGS) $(HOSTCFLAGS) >> KBUILD_HOSTCXXFLAGS := -Wall -O2 $(HOST_LFS_CFLAGS) $(HOSTCXXFLAGS) >> KBUILD_HOSTLDFLAGS := $(HOST_LFS_LDFLAGS) $(HOSTLDFLAGS) >> KBUILD_HOSTLDLIBS := $(HOST_LFS_LIBS) $(HOSTLDLIBS) >> >> +KBUILD_USERCFLAGS += $(USERCFLAGS) > >Since you added USERLDFLAGS to KBUILD_USERLDFLAGS above where it's >defined, why not do so for USERCFLAGS/KBUILD_USERCFLAGS as well? > >> + >> # Make variables (CC, etc...) >> CPP = $(CC) -E >> ifneq ($(LLVM),) >> @@ -530,6 +532,7 @@ export CPP AR NM STRIP OBJCOPY OBJDUMP READELF PAHOLE RESOLVE_BTFIDS LEX YACC AW >> export PERL PYTHON3 CHECK CHECKFLAGS MAKE UTS_MACHINE HOSTCXX >> export KGZIP KBZIP2 KLZOP LZMA LZ4 XZ ZSTD >> export KBUILD_HOSTCXXFLAGS KBUILD_HOSTLDFLAGS KBUILD_HOSTLDLIBS LDFLAGS_MODULE >> +export KBUILD_USERCFLAGS KBUILD_USERLDFLAGS >> >> export KBUILD_CPPFLAGS NOSTDINC_FLAGS LINUXINCLUDE OBJCOPYFLAGS KBUILD_LDFLAGS >> export KBUILD_CFLAGS CFLAGS_KERNEL CFLAGS_MODULE >> diff --git a/init/Kconfig b/init/Kconfig >> index f2ae41e6717f..164706c38e8b 100644 >> --- a/init/Kconfig >> +++ b/init/Kconfig >> @@ -62,13 +62,13 @@ config LLD_VERSION >> >> config CC_CAN_LINK >> bool >> - default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m64-flag)) if 64BIT >> - default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m32-flag)) >> + default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag)) if 64BIT >> + default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag)) >> >> config CC_CAN_LINK_STATIC >> bool >> - default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m64-flag) -static) if 64BIT >> - default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m32-flag) -static) >> + default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag) -static) if 64BIT >> + default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m32-flag) -static) > >since USERLDFLAGS get passed to $(CC), they will need `-Wl`, prefixes, >hence the request for expanding the example usage in the commit >message. > >> >> config CC_HAS_ASM_GOTO >> def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC)) >> diff --git a/usr/include/Makefile b/usr/include/Makefile >> index 1c2ae1368079..6a8c7dd9ccaf 100644 >> --- a/usr/include/Makefile >> +++ b/usr/include/Makefile >> @@ -12,6 +12,9 @@ UAPI_CFLAGS := -std=c90 -Wall -Werror=implicit-function-declaration >> # It is here just because CONFIG_CC_CAN_LINK is tested with -m32 or -m64. >> UAPI_CFLAGS += $(filter -m32 -m64, $(KBUILD_CFLAGS)) >> >> +# USERCFLAGS might contain sysroot location for CC >> +UAPI_CFLAGS += $(USERCFLAGS) >> + > >Do we need to worry about USERLDFLAGS here, too? (or usr/Makefile?) > >> override c_flags = $(UAPI_CFLAGS) -Wp,-MMD,$(depfile) -I$(objtree)/usr/include >> >> # The following are excluded for now because they fail to build. >> -- >> 2.25.1 >> > > >-- >Thanks, >~Nick Desaulniers