From patchwork Fri Jul 30 20:17:01 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nick Desaulniers X-Patchwork-Id: 12411827 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=-26.3 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_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 40EE9C4320A for ; Fri, 30 Jul 2021 20:17:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 228CD61074 for ; Fri, 30 Jul 2021 20:17:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230199AbhG3URS (ORCPT ); Fri, 30 Jul 2021 16:17:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46568 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231584AbhG3URQ (ORCPT ); Fri, 30 Jul 2021 16:17:16 -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 1889AC0613CF for ; Fri, 30 Jul 2021 13:17:11 -0700 (PDT) Received: by mail-qt1-x849.google.com with SMTP id y25-20020ac870990000b02902536d2bea0fso2091829qto.19 for ; Fri, 30 Jul 2021 13:17:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=bdaJ+2ov+VGokTpwDiU9B4WCnxMwARVW0/jkGqItkL4=; b=ba2SFUQKtzWx/58l/55eeBKV35/AZvblErwEGcbZGZlsLojN9JeqV6Tw8kAKE6qlG2 ym8ry/iMK4HE0KbVB0A2VTaYK/kZXBK/3RPsrjgOiTsN0j++SXbSohQ0Eho6V+ZfYs/f gFCMdQXg4mvgXqDlVusy6BnT5JLJkbe83rrZwbBS3BaycGSKk+8w4SO/Gxb7G+5tpvqk hCD4IuahkkfI8iUegm7RwEkgVF2Pqgul1F4FaubIOWMFVAG2BtnOtearby3X15o2KFTx y3Et+Ov2U06hVw41XujKKNSW+xZo94Q6wSvgdFX1szA31prIlHwixCRmeYFOkzWD1wRh L6hg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=bdaJ+2ov+VGokTpwDiU9B4WCnxMwARVW0/jkGqItkL4=; b=KRZIbWlgFO3uoVEl8wRRNmC4OJIo7iv8qcgdK2fjGd7by2UDAGRoj+n5x7/Qng7Xv3 AO6LdhUtSQp6uzBAbuzh/Ofwk7D4nx+/xk2QdrJ0AvA3eUfeVTpopIj8mAcTFkzOondC 9P2gr2Vcj35NS4G2BkLS9DuNTeoOTgKRXihNhkgoApKgv4zLEkjQ0wYHph1RplpPuCDO thaSJ4PrPeww4qk244RjCJX7L8vFVPZopaIFqZHQdrApzVBtFjXDbAso3xs9y0aYzt6b 5SlDv5B6CbbRbarZTjhrLGDbw8M7dqvx6O+CZuFLg7/3Q1chB34K3DUHAvAxoem/IB2l HoeA== X-Gm-Message-State: AOAM530lmq2q3+uFADzEVaa7zTEbxNHNsxHMIgAFIh3eFujtc6kAk+dO T3UCFw1qPtKZH4TrNgrq/v5d5UObezRvao28k00= X-Google-Smtp-Source: ABdhPJye6o8W8X7eDFzsZhDjFMznUBlbpeE7wFvMJfhzqXwDIp1dphJO4tLOAXueCXTC3nUrvzUBHN4BGAw3p2QzwlQ= X-Received: from ndesaulniers1.mtv.corp.google.com ([2620:15c:211:202:ca8b:b433:7c1d:90d]) (user=ndesaulniers job=sendgmr) by 2002:a05:6214:134c:: with SMTP id b12mr3056998qvw.39.1627676230194; Fri, 30 Jul 2021 13:17:10 -0700 (PDT) Date: Fri, 30 Jul 2021 13:17:01 -0700 In-Reply-To: <20210730201701.3146910-1-ndesaulniers@google.com> Message-Id: <20210730201701.3146910-3-ndesaulniers@google.com> Mime-Version: 1.0 References: <20210730201701.3146910-1-ndesaulniers@google.com> X-Mailer: git-send-email 2.32.0.554.ge1b32706d8-goog Subject: [PATCH v4 2/2] Documentation/llvm: update CROSS_COMPILE inferencing From: Nick Desaulniers To: Masahiro Yamada Cc: Miguel Ojeda , Fangrui Song , Michal Marek , Arnd Bergmann , linux-kernel@vger.kernel.org, linux-kbuild@vger.kernel.org, clang-built-linux@googlegroups.com, Geert Uytterhoeven , Christoph Hellwig , Linus Torvalds , Nick Desaulniers Precedence: bulk List-ID: X-Mailing-List: linux-kbuild@vger.kernel.org As noted by Masahiro, document how we can generally infer CROSS_COMPILE (and the more specific details about --target and --prefix) based on ARCH. Suggested-by: Masahiro Yamada Signed-off-by: Nick Desaulniers --- Note: Masahiro, I'm sorry for putting my name on this as you mostly wrote it. I touched it up slightly. I don't know how best to attribute it to you. If you'd prefer to take back authorship, please do; I'd rather not add your SOB without seeing it stated explicitly. Documentation/kbuild/llvm.rst | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/Documentation/kbuild/llvm.rst b/Documentation/kbuild/llvm.rst index b18401d2ba82..4292f0686316 100644 --- a/Documentation/kbuild/llvm.rst +++ b/Documentation/kbuild/llvm.rst @@ -63,6 +63,23 @@ They can be enabled individually. The full list of the parameters: :: Currently, the integrated assembler is disabled by default. You can pass ``LLVM_IAS=1`` to enable it. +Omitting CROSS_COMPILE +---------------------- + +As explained above, ``CROSS_COMPILE`` is used to set ``--target=``. + +Unless ``LLVM_IAS=1`` is specified, ``CROSS_COMPILE`` is also used to derive +``--prefix=`` to search for the GNU assembler. + +If ``CROSS_COMPILE`` is not specified, the ``--target=`` is inferred +from ``ARCH``. + +That means if you use only LLVM tools, ``CROSS_COMPILE`` becomes unnecessary. + +For example, to cross-compile the arm64 kernel:: + + ARCH=arm64 make LLVM=1 LLVM_IAS=1 + Supported Architectures -----------------------