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=-23.3 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,SPF_HELO_NONE,SPF_PASS, USER_IN_DEF_DKIM_WL autolearn=unavailable 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 271AFC5519F for ; Sat, 21 Nov 2020 09:49:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CF63E2224A for ; Sat, 21 Nov 2020 09:49:20 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="NDK1nLAg" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727398AbgKUJs7 (ORCPT ); Sat, 21 Nov 2020 04:48:59 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41902 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727350AbgKUJs6 (ORCPT ); Sat, 21 Nov 2020 04:48:58 -0500 Received: from mail-lf1-x144.google.com (mail-lf1-x144.google.com [IPv6:2a00:1450:4864:20::144]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A5AB7C0613CF for ; Sat, 21 Nov 2020 01:48:57 -0800 (PST) Received: by mail-lf1-x144.google.com with SMTP id r24so831021lfm.8 for ; Sat, 21 Nov 2020 01:48:57 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=BQiLNTLnW3SLtn0YsnDFKEJnLKO+RrQeEC1pO6DUX3I=; b=NDK1nLAguE/ieGaWEY+FmLBnFzKQ+keiUbLA87fRWbeoBl0TUnxoIWidngljNw3njr T9o8cTivwQ/PNTS8SRA8GGOH3lhovcdXa7KS3UtRt1obJiBdyCZZl9Xlfw4rzkmyGOTd uLGvEZ1QZa5J6Tp8nfw/NzJd+K1nkbMjtRkcCChOxm0B7P2+fVxhLjJYZYL3Q7DkFqaR T3AKSwfY5cZnPoVzlZ66HzscshjnesEaQzqHuuFTVW0GRzwo5rZ75HFGKONmKLB103Am QO3KboK3J0HYVm4pMpi2LzNDqw5WjPohXcC1BMna74BqabedOAZCTbSZTqUHiUTJ5sWr xRZA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=BQiLNTLnW3SLtn0YsnDFKEJnLKO+RrQeEC1pO6DUX3I=; b=d2+F4orgwfy3PHec4R9eytKOIglwVKMrN0kF0e4sW2Fgp3ZqTE+bwlwxVvr5WTUawt S3sDrIW4AvEW4FqpDc27gZ8HXZIWN0Nr8hOnuxYEL1fBLHP4XAKTqwCLENKN2E4QY095 5XnwOfcwIadrboONVHP2paushQBKrzEmOWNF3sSqfDLNOwVO/GKVHA70j0uIiCPOIWMJ D1B1LODI2wxeRE2A05+uTyXbHRoGHFsOfAjFh5i7Zx5KOect1Jn2lN9TenQoTtKCDQ7z EPe/ujrRPUJo1mF2O31+f8kUdQgIzPHCwJazi3VbDN7Cyg/mRATrg0o298jNkE8cdC2c tu3g== X-Gm-Message-State: AOAM531Gh+0lzBocP2sCBV8ngiZk9Ge+jFPzrJrbLLBFbiN00fzA2L6g wkq+tT/8P8R/aQZgneMGg0QtN9/3e380sM/D3+47UA== X-Google-Smtp-Source: ABdhPJxud8h9+Zsb7MJedEB+VgeNBdrfewqkbrhXLdc6jkC62nTrXEoFHkJAkLhxgIShY2CKy1qJr682LJJZVeaTVL4= X-Received: by 2002:a05:6512:110a:: with SMTP id l10mr9769828lfg.167.1605952135886; Sat, 21 Nov 2020 01:48:55 -0800 (PST) MIME-Version: 1.0 References: <20201119085022.3606135-1-davidgow@google.com> In-Reply-To: From: David Gow Date: Sat, 21 Nov 2020 17:48:44 +0800 Message-ID: Subject: Re: [RFC PATCH] bpf: preload: Fix build error when O= is set To: Andrii Nakryiko Cc: Alexei Starovoitov , Daniel Borkmann , =?UTF-8?B?VG9rZSBIw7hpbGFuZC1Kw7hyZ2Vuc2Vu?= , Networking , bpf , open list , Brendan Higgins , Masami Hiramatsu , linux-um Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Sat, Nov 21, 2020 at 3:38 PM Andrii Nakryiko wrote: > > On Thu, Nov 19, 2020 at 12:51 AM David Gow wrote: > > > > If BPF_PRELOAD is enabled, and an out-of-tree build is requested with > > make O=, compilation seems to fail with: > > > > tools/scripts/Makefile.include:4: *** O=.kunit does not exist. Stop. > > make[4]: *** [../kernel/bpf/preload/Makefile:8: kernel/bpf/preload/libbpf.a] Error 2 > > make[3]: *** [../scripts/Makefile.build:500: kernel/bpf/preload] Error 2 > > make[2]: *** [../scripts/Makefile.build:500: kernel/bpf] Error 2 > > make[2]: *** Waiting for unfinished jobs.... > > make[1]: *** [.../Makefile:1799: kernel] Error 2 > > make[1]: *** Waiting for unfinished jobs.... > > make: *** [Makefile:185: __sub-make] Error 2 > > > > By the looks of things, this is because the (relative path) O= passed on > > the command line is being passed to the libbpf Makefile, which then > > can't find the directory. Given OUTPUT= is being passed anyway, we can > > work around this by explicitly setting an empty O=, which will be > > ignored in favour of OUTPUT= in tools/scripts/Makefile.include. > > Strange, but I can't repro it. I use make O= all the > time with no issues. I just tried specifically with a make O=.build, > where .build is inside Linux repo, and it still worked fine. See also > be40920fbf10 ("tools: Let O= makes handle a relative path with -C > option") which was supposed to address such an issue. So I'm wondering > what exactly is causing this problem. > [+ linux-um list] Hmm... From a quick check, I can't reproduce this on x86, so it's possibly a UML-specific issue. The problem here seems to be that $PWD is, for whatever reason, equal to the srcdir on x86, but not on UML. In general, $PWD behaves pretty weirdly -- I don't fully understand it -- but if I add a tactical "PWD := $(shell pwd)" or use $(CURDIR) instead, the issue shows up on x86 as well. I guess this is because PWD only gets updated when set by a shell or something, and UML does this somewhere? Thoughts? Cheers, -- David > > > > Signed-off-by: David Gow > > --- > > > > Hi all, > > > > I'm not 100% sure this is the correct fix here -- it seems to work for > > me, and makes some sense, but let me know if there's a better way. > > > > One other thing worth noting is that I've been hitting this with > > make allyesconfig on ARCH=um, but there's a comment in the Kconfig > > suggesting that, because BPF_PRELOAD depends on !COMPILE_TEST, that > > maybe it shouldn't be being built at all. I figured that it was worth > > trying to fix this anyway. > > > > Cheers, > > -- David > > > > > > kernel/bpf/preload/Makefile | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/kernel/bpf/preload/Makefile b/kernel/bpf/preload/Makefile > > index 23ee310b6eb4..39848d296097 100644 > > --- a/kernel/bpf/preload/Makefile > > +++ b/kernel/bpf/preload/Makefile > > @@ -5,7 +5,7 @@ LIBBPF_A = $(obj)/libbpf.a > > LIBBPF_OUT = $(abspath $(obj)) > > > > $(LIBBPF_A): > > - $(Q)$(MAKE) -C $(LIBBPF_SRCS) OUTPUT=$(LIBBPF_OUT)/ $(LIBBPF_OUT)/libbpf.a > > + $(Q)$(MAKE) -C $(LIBBPF_SRCS) O= OUTPUT=$(LIBBPF_OUT)/ $(LIBBPF_OUT)/libbpf.a > > > > userccflags += -I $(srctree)/tools/include/ -I $(srctree)/tools/include/uapi \ > > -I $(srctree)/tools/lib/ -Wno-unused-result > > -- > > 2.29.2.454.gaff20da3a2-goog > >