From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl1-x62e.google.com (mail-pl1-x62e.google.com [IPv6:2607:f8b0:4864:20::62e]) by sourceware.org (Postfix) with ESMTPS id 67F473858406 for ; Sat, 25 Dec 2021 03:09:34 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 67F473858406 Received: by mail-pl1-x62e.google.com with SMTP id h6so3758687plf.6 for ; Fri, 24 Dec 2021 19:09:34 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=1CEphJcHRGImoKErRy9HKYN7QFQDxNtwP8BRVKpMWj0=; b=2mzZbhoHfBSPusbR4npRcHpyEmZi0mGLMy+D6U73aflZ6JhRyeR2mrsivf0QHJu1js x6Vgvt9ZqQBw9YMhgFRxPYVB2KNV7pQ5NKc812DcSpH/lskVUEv01ouWERGfZXWtkr1y hNmkJPUlqtTiTJ4ISybDim1Hz/7Uc9xeEezvroUhJjGNkugLmUEaKPh8vjsy/09/7UK9 zgCRbD7veyyhXzxQRglmBBQofNaA7xpKgXGhsnKRJK9FZswWWifsbRNnHq0lI1/jhZ+l zuip8NC8JEmdFCV0FCSfAgLvkMkocQS9GvqWno9qGABnTKivC9Ee8Y/xbsbH5ZMGIBou FnhQ== X-Gm-Message-State: AOAM532ihw3FdGbR9P7S0xaJNgKjULFmSJI1jahpcuTiKuuu7jqKWSUI N5RHvlZMhYy7usZHX8dYAYJWe+dqGNvS/C8Z2ReboTTLUsw= X-Google-Smtp-Source: ABdhPJyqEEkUTInPRNUcB+0UzhfjsCceK9W3sBbOYB8vf2rO9XvA22lCy+Oc/2nBmrRovABnpXvksUwID3qIURTg71s= X-Received: by 2002:a17:902:f284:b0:148:a2af:4abd with SMTP id k4-20020a170902f28400b00148a2af4abdmr3265285plc.4.1640401773548; Fri, 24 Dec 2021 19:09:33 -0800 (PST) MIME-Version: 1.0 References: <20211215163232.1787673-1-hjl.tools@gmail.com> In-Reply-To: From: "H.J. Lu" Date: Fri, 24 Dec 2021 19:08:57 -0800 Message-ID: Subject: Re: [PATCH v2] elf: Set p_align to the minimum page size if possible To: Alan Modra Cc: Binutils , Nick Clifton , Florian Weimer Content-Type: text/plain; charset="UTF-8" X-Spam-Status: No, score=-3022.1 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, FREEMAIL_FROM, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: binutils@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Binutils mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 25 Dec 2021 03:09:35 -0000 On Fri, Dec 24, 2021 at 7:04 PM Alan Modra wrote: > > On Fri, Dec 24, 2021 at 06:50:30PM -0800, H.J. Lu wrote: > > On Fri, Dec 24, 2021 at 5:03 PM Alan Modra wrote: > > > I don't see a way to change DT_LOAD p_align that is backwards > > > compatible, except perhaps using a p_align of zero if the required > > > segment alignment (as calculated from section alignment) is less than > > > maxpagesize. That horrible hack just happens to work for older glibc, > > > but may break other loaders. > > > > Neither 0 nor 1 work for older glibc: > > > > if (__glibc_unlikely ((ph->p_align & (GLRO(dl_pagesize) - 1)) != 0)) > > { > > errstring = N_("ELF load command alignment not page-aligned"); > > goto lose; > > } > > if (__glibc_unlikely (((ph->p_vaddr - ph->p_offset) > > & (ph->p_align - 1)) != 0)) > > { > > errstring > > = N_("ELF load command address/offset not properly aligned"); > > goto lose; > > } > > Zero in p_align triggers neither of these conditions. Binaries with > zero p_align run. I checked. > I tried setting p_align to 0 and got ELF load command address/offset not properly aligned For if (__glibc_unlikely (((ph->p_vaddr - ph->p_offset) & (ph->p_align - 1)) != 0)) If ph->p_vaddr - ph->p_offset == 0, it will trigger this error: Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align LOAD 0x000000 0x0000000000000000 0x0000000000000000 0x000578 0x000578 R 0x1000 LOAD 0x001000 0x0000000000001000 0x0000000000001000 0x00012d 0x00012d R E 0x1000 LOAD 0x002000 0x0000000000002000 0x0000000000002000 0x0000a4 0x0000a4 R 0x1000 LOAD 0x002df8 0x0000000000003df8 0x0000000000003df8 0x00022c 0x000230 RW 0x1000 -- H.J.