From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.9]) (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 AE02F3C15 for ; Mon, 12 Feb 2024 07:07:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.9 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707721664; cv=none; b=PBly9+k7g60odT+1pKVeUvEkuXw69pgKQw78CJfoGu0EWSSZdEC8ZqI6grwGb+nOkIgmd1mJhuPXWiRUFGcjDp6Laf3Qr5VKW10rIHlilRoATEvpkDB5e7SZSwsGH8JeLQOkFoff43+tNU0ATPE71YA3OpY9Nl+QCBP1EJtrcwY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707721664; c=relaxed/simple; bh=RCdOiggCm0l00XC8KnOXtFiS/o7OVO9sEQ1asC4jtCM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=daoPJxHe2mAAuryVIZv9OG5HJnbWdcbZIJU87NNgry6SkNrZbgmchc5ofDJCPjXlOsEjhUdR03zXDOqqdXpvw4ey46nidsRas/GYRxzH0sCMQrFvxbY2+V84l2JqtQU5ISDggHn47HDDT7qDLi4/g6wwJsXhcgiq0tdsnCy6PnI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=none smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=aXSzU+/I; arc=none smtp.client-ip=192.198.163.9 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="aXSzU+/I" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1707721663; x=1739257663; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=RCdOiggCm0l00XC8KnOXtFiS/o7OVO9sEQ1asC4jtCM=; b=aXSzU+/IkpWWgGF82tz6btsNw+uy72ho47TOqVdrMXi1wgL3gZBRAlH+ bgpaplGz65sEX//d21oDUJjTVT5ylW9ERnF1pmCXc6T4JaovsK+l2b75s JIPaM98Zh2jOUYjpTVGqS/sbSMDsxZ16bQUNvmhxTv9Fyti4ZXfihm9Sj f13c0YpNTAyVvqrxy6d4QYxbkohqu20L16P8dkqFxFNzQVXCbETpbITrw dUNSXAYTnqcT5+uhHiOg6LZUysJs+SHheKHiEKLdPqOgJu5qx4RSCoOGo m/D5H7dIYGGeXXX7vQFNZM+O25b0JqLr4zFL9YnqXei/KY1hOeAPkSIyW g==; X-IronPort-AV: E=McAfee;i="6600,9927,10981"; a="12412233" X-IronPort-AV: E=Sophos;i="6.05,262,1701158400"; d="scan'208";a="12412233" Received: from orviesa009.jf.intel.com ([10.64.159.149]) by fmvoesa103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Feb 2024 23:07:42 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.05,262,1701158400"; d="scan'208";a="2518876" Received: from tassilo.jf.intel.com (HELO tassilo) ([10.54.38.190]) by orviesa009-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Feb 2024 23:07:41 -0800 Date: Sun, 11 Feb 2024 23:07:40 -0800 From: Andi Kleen To: Bagas Sanjaya Cc: hapter@420blaze.it, mingo@redhat.com, tglx@linutronix.de, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, Andrew Morton , Linux Kernel Mailing List , Linux Memory Management List Subject: Re: arch/x86/kernel/sys_x86_64.c: rationale for 0x40000000 for MAP_32BIT's start address? Message-ID: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: > >> Unfortunately this does not supply a rationale for starting from 0x40000000, > >> which seems very arbitrary, and the git commit has been there since the > >> beginning of time (i.e. as far the the git history goes), so the git blame > >> has not helped much to clarify it. I was also not able to find who "AK" was. > > > > That was from commit 717db2f9f36805 ("[PATCH] x86-64 updates for 2.5.54") > > in tglx/history.git repo [1], authored by Andi Kleen. Cc'ing him. > > > > [1]: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git/commit/arch/x86_64/kernel/sys_x86_64.c?id=717db2f9f36805d85c695771ea7d712812896aa7 I thought the comment was clear? The 1GB start is to avoid conflicts with the brk heap, which grows up. The flag is really obsolete, if you want limited relocations there are better ways to do it that don't limit ASLR. It was originally because the custom module loader in X.org didn't support a PLT. -Andi