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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id B1D7310F284F for ; Fri, 27 Mar 2026 16:52:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=859ciwTLws9gTLdPiMbsS4SJ1GOzZrhoCCXtFwVU8lM=; b=3ed41XdAecnDYxMYKgToC3YlIg Q2L5fRSvCuoZM7kkPKeCgG/CZFZT/vbg4UJZmzWCUBqQpvavqZUE4sfFN6uG8jlI4IQvJKKRKB65m K2arSqJyK98vn1xOTP6+p3oFe8BSbczrxBM9HVaT1Q9pDdN6AcTPWLZpggeUQq9Va6KEJSiBqK9kl bOkHNoKvRS6cGlkC37RKtQEchVTfYH0x0LaCsDUmKqzIZdRUOwhj/AdY3XDFmV5BCjAZ3pr7N/JyI axUo9y2bwVsDg28UoYp1ogPs3tP8yTJ4qoB0KTmKPhHEEtrqUUE9i7jzjA4mqo6D65PuDMFigEfOL TuidYS5Q==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1w6APu-00000007oKv-0XfV; Fri, 27 Mar 2026 16:52:14 +0000 Received: from out-188.mta0.migadu.com ([91.218.175.188]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1w6APr-00000007oJ0-1SVg for linux-arm-kernel@lists.infradead.org; Fri, 27 Mar 2026 16:52:13 +0000 Message-ID: <09f1f982-4143-4c57-9bf6-fee546b2606b@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1774630314; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=859ciwTLws9gTLdPiMbsS4SJ1GOzZrhoCCXtFwVU8lM=; b=eQdxda0VXEY8Bm/gK5z/H6o1WBS+xzZU7GDDlPJSxH272S+kvcs994vq5gP6ylP0fK8WMr wZ1KR8sjIN6G+BRLqc71go1CgG/LVZHt2CFRm94mVG4EXUF0oS5jnoZ0DXugjTmf62p1Ib 6N/JEBZtBILoFe3eY8E3oEAIcUuUG20= Date: Fri, 27 Mar 2026 12:51:47 -0400 MIME-Version: 1.0 Subject: Re: [PATCH v2 3/4] elf: align ET_DYN base to max folio size for PTE coalescing Content-Language: en-GB To: Matthew Wilcox Cc: Andrew Morton , david@kernel.org, ryan.roberts@arm.com, linux-mm@kvack.org, r@hev.cc, jack@suse.cz, ajd@linux.ibm.com, apopple@nvidia.com, baohua@kernel.org, baolin.wang@linux.alibaba.com, brauner@kernel.org, catalin.marinas@arm.com, dev.jain@arm.com, kees@kernel.org, kevin.brodsky@arm.com, lance.yang@linux.dev, Liam.Howlett@oracle.com, linux-arm-kernel@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, lorenzo.stoakes@oracle.com, mhocko@suse.com, npache@redhat.com, pasha.tatashin@soleen.com, rmclure@linux.ibm.com, rppt@kernel.org, surenb@google.com, vbabka@kernel.org, Al Viro , wilts.infradead.org@kvack.org, ziy@nvidia.com, hannes@cmpxchg.org, kas@kernel.org, shakeel.butt@linux.dev, kernel-team@meta.com References: <20260320140315.979307-1-usama.arif@linux.dev> <20260320140315.979307-4-usama.arif@linux.dev> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Usama Arif In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260327_095211_614982_CD575D8D X-CRM114-Status: GOOD ( 21.01 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 20/03/2026 18:58, Matthew Wilcox wrote: > On Fri, Mar 20, 2026 at 06:58:53AM -0700, Usama Arif wrote: >> -static unsigned long maximum_alignment(struct elf_phdr *cmds, int nr) >> +static unsigned long maximum_alignment(struct elf_phdr *cmds, int nr, >> + struct file *filp) >> { >> unsigned long alignment = 0; >> + unsigned long max_folio_size = PAGE_SIZE; >> int i; >> >> + if (filp && filp->f_mapping) >> + max_folio_size = mapping_max_folio_size(filp->f_mapping); > > Under what circumstances can bprm->file be NULL? Yeah its unnecessary here. Its used in other places and this is never checked, so we can remove it. > > Also we tend to prefer the name "file" rather than "filp" for new code > (yes, there's a lot of old code out there). > ack. will change in next revision. >> + >> + /* >> + * Try to align the binary to the largest folio >> + * size that the page cache supports, so the >> + * hardware can coalesce PTEs (e.g. arm64 >> + * contpte) or use PMD mappings for large folios. >> + * >> + * Use the largest power-of-2 that fits within >> + * the segment size, capped by what the page >> + * cache will allocate. Only align when the >> + * segment's virtual address and file offset are >> + * already aligned to the folio size, as >> + * misalignment would prevent coalescing anyway. >> + * >> + * The segment size check avoids reducing ASLR >> + * entropy for small binaries that cannot >> + * benefit. >> + */ >> + if (!cmds[i].p_filesz) >> + continue; >> + size = rounddown_pow_of_two(cmds[i].p_filesz); >> + size = min(size, max_folio_size); >> + if (size > PAGE_SIZE && >> + IS_ALIGNED(cmds[i].p_vaddr, size) && >> + IS_ALIGNED(cmds[i].p_offset, size)) >> + alignment = max(alignment, size); > > Can this not all be factored out into a different function? Also, I > think it was done a bit better here: > https://lore.kernel.org/linux-fsdevel/20260313005211.882831-1-r@hev.cc/ > > + if (!IS_ALIGNED(cmd->p_vaddr | cmd->p_offset, PMD_SIZE)) > + return false; > ack, will try and address this accordingly. Thanks for the reviews!!