From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from conuserg-08.nifty.com (conuserg-08.nifty.com [210.131.2.75]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 006C81852 for ; Fri, 27 May 2022 10:04:51 +0000 (UTC) Received: from grover.sesame (133-32-177-133.west.xps.vectant.ne.jp [133.32.177.133]) (authenticated) by conuserg-08.nifty.com with ESMTP id 24RA2hPV029808; Fri, 27 May 2022 19:02:49 +0900 DKIM-Filter: OpenDKIM Filter v2.10.3 conuserg-08.nifty.com 24RA2hPV029808 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nifty.com; s=dec2015msa; t=1653645770; bh=aeTLWp41sB2px7vbsl+AoWvoxM63JuytaCqa9JH2QLY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=HNBXNGONQ3XAXjEyNsT812P/sRM9yUOuKeEx6rV5MeMv1NxMHnZVXWp2u3jL3+YhO hHwEyE27UCcCCype5LopeDwcShy1TIjgvIzb35fNVES8P6DPUjAtO/oKmWQyrjKn7e bNLeFrwGDnwLBGzZ9ECYC+HfWtv1orzRaQxDXtS4bmogZCcZlcfc0L4a8I5xbtRerl AENHInpUJ2umDWLEQ3o3RVbecF3RavfGGRbduj+yTrY6zqZ1VeHFrt267AKy33Vb4M j/NpQV/JGiOhD8mPqsR5WAZPocvvNN8niceVYS/cuIu+CoXuwCESKCAm4kbrQ1JKic Dpe+I0j85Opbg== X-Nifty-SrcIP: [133.32.177.133] From: Masahiro Yamada To: linux-kbuild@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Peter Zijlstra , Josh Poimboeuf , llvm@lists.linux.dev, Helge Deller , linux-parisc@vger.kernel.org, Masahiro Yamada , Nicolas Schier , Nathan Chancellor , Sedat Dilek , Michal Marek , Nick Desaulniers , Tom Rix Subject: [PATCH v7 5/8] kbuild: make built-in.a rule robust against too long argument error Date: Fri, 27 May 2022 19:01:52 +0900 Message-Id: <20220527100155.1996314-6-masahiroy@kernel.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20220527100155.1996314-1-masahiroy@kernel.org> References: <20220527100155.1996314-1-masahiroy@kernel.org> Precedence: bulk X-Mailing-List: llvm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Kbuild runs at the top of objtree instead of changing the working directory to subdirectories. I think this design is nice overall but some commands have a scalability issue. The build command of built-in.a is one of them whose length scales with: O(D * N) Here, D is the length of the directory path (i.e. $(obj)/ prefix), N is the number of objects in the Makefile, O() is the big O notation. The deeper directory the Makefile directory is located, the more easily it will hit the too long argument error. We can make it better. Trim the $(obj)/ by Make's builtin function, and restore it by a shell command (sed). With this, the command length scales with: O(D + N) In-tree modules still have some room to the limit (ARG_MAX=2097152), but this is more future-proof for big modules in a deep directory. For example, you can build i915 as builtin (CONFIG_DRM_I915=y) and compare drivers/gpu/drm/i915/.built-in.a.cmd with/without this commit. Signed-off-by: Masahiro Yamada Reviewed-by: Nicolas Schier Tested-by: Nathan Chancellor Tested-by: Sedat Dilek # LLVM-14 (x86-64) --- Changes in v7: - Add comment to the code Changes in v2: - New patch scripts/Makefile.build | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/scripts/Makefile.build b/scripts/Makefile.build index 0135b4e7f78b..014ebee70fd6 100644 --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -376,9 +376,14 @@ $(subdir-modorder): $(obj)/%/modules.order: $(obj)/% ; # # Rule to compile a set of .o files into one .a file (without symbol table) # +# To make this rule robust against "Argument list too long" error, +# remove $(obj)/ prefix, and restore it by a shell command. quiet_cmd_ar_builtin = AR $@ - cmd_ar_builtin = rm -f $@; $(AR) cDPrST $@ $(real-prereqs) + cmd_ar_builtin = rm -f $@; \ + echo $(patsubst $(obj)/%,%,$(real-prereqs)) | \ + sed -E 's:([^ ]+):$(obj)/\1:g' | \ + xargs $(AR) cDPrST $@ $(obj)/built-in.a: $(real-obj-y) FORCE $(call if_changed,ar_builtin) -- 2.32.0