From nobody Thu Jul 20 20:15:15 2023
X-Original-To: dev-commits-src-all@mlmmj.nyi.freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1])
	by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 4R6P7Z0nD6z4p5Nc;
	Thu, 20 Jul 2023 20:15:22 +0000 (UTC)
	(envelope-from brooks@spindle.one-eyed-alien.net)
Received: from spindle.one-eyed-alien.net (spindle.one-eyed-alien.net [199.48.129.229])
	(using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)
	 key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256)
	(Client did not present a certificate)
	by mx1.freebsd.org (Postfix) with ESMTPS id 4R6P7Y4n5Jz3GpJ;
	Thu, 20 Jul 2023 20:15:21 +0000 (UTC)
	(envelope-from brooks@spindle.one-eyed-alien.net)
Authentication-Results: mx1.freebsd.org;
	none
Received: by spindle.one-eyed-alien.net (Postfix, from userid 3001)
	id 55EC13C0199; Thu, 20 Jul 2023 20:15:15 +0000 (UTC)
Date: Thu, 20 Jul 2023 20:15:15 +0000
From: Brooks Davis <brooks@freebsd.org>
To: Konstantin Belousov <kib@freebsd.org>
Cc: src-committers@freebsd.org, dev-commits-src-all@freebsd.org,
	dev-commits-src-main@freebsd.org
Subject: Re: git: 21e45c30c35c - main - mmap(MAP_STACK): on stack grow, use
 original protection
Message-ID: <ZLmV0wQ1mgkiSbwK@spindle.one-eyed-alien.net>
References: <202307201412.36KECDSU084918@gitrepo.freebsd.org>
List-Id: Commit messages for all branches of the src repository <dev-commits-src-all.freebsd.org>
List-Archive: https://lists.freebsd.org/archives/dev-commits-src-all
List-Help: <mailto:dev-commits-src-all+help@freebsd.org>
List-Post: <mailto:dev-commits-src-all@freebsd.org>
List-Subscribe: <mailto:dev-commits-src-all+subscribe@freebsd.org>
List-Unsubscribe: <mailto:dev-commits-src-all+unsubscribe@freebsd.org>
Sender: owner-dev-commits-src-all@freebsd.org
X-BeenThere: dev-commits-src-all@freebsd.org
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <202307201412.36KECDSU084918@gitrepo.freebsd.org>
X-Rspamd-Queue-Id: 4R6P7Y4n5Jz3GpJ
X-Spamd-Bar: ----
X-Spamd-Result: default: False [-4.00 / 15.00];
	REPLY(-4.00)[];
	ASN(0.00)[asn:36236, ipnet:199.48.128.0/22, country:US]
X-Rspamd-Pre-Result: action=no action;
	module=replies;
	Message is reply to one we originated

On Thu, Jul 20, 2023 at 02:12:13PM +0000, Konstantin Belousov wrote:
> The branch main has been updated by kib:
> 
> URL: https://cgit.FreeBSD.org/src/commit/?id=21e45c30c35c9aa732073f725924caf581c93460
> 
> commit 21e45c30c35c9aa732073f725924caf581c93460
> Author:     Konstantin Belousov <kib@FreeBSD.org>
> AuthorDate: 2023-07-19 11:05:32 +0000
> Commit:     Konstantin Belousov <kib@FreeBSD.org>
> CommitDate: 2023-07-20 14:11:42 +0000
> 
>     mmap(MAP_STACK): on stack grow, use original protection
>     
>     If mprotect(2) changed protection in the bottom of the currently grown
>     stack region, currently the changed protection would be used for the
>     stack grow on next fault.  This is arguably unexpected.
>     
>     Store the original protection for the entry at mmap(2) time in the
>     offset member of the gap vm_map_entry, and use it for protection of the
>     grown stack region.

It occured to me to wonder how this interacts with
__enable_execute_stack().  I think it's ok so long as the compiler
always emits __enable_execute_stack() for each trampoline and doesn't
depend on extentions to the stack being executable from the first
trampoline creation, but I don't know where to look to verify that's the
case.

-- Brooks