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> In-Reply-To: <202307201412.36KECDSU084918@gitrepo.freebsd.org> References: <202307201412.36KECDSU084918@gitrepo.freebsd.org>
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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
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