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From: Carlo Arenas <>
Subject: Re: [RFC PATCH 1/2] grep: fallback to interpreter if JIT fails with pcre1
Date: Sun, 9 Dec 2018 17:25:56 -0800	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Sun, Dec 9, 2018 at 4:42 PM brian m. carlson
<> wrote:
> On Mon, Dec 10, 2018 at 12:51:01AM +0100, Ævar Arnfjörð Bjarmason wrote:
> > Obviously this & what you have in 2/2 needs to be fixed in some way.
> >
> > Is the issue on SELinux, OpenBSD, NetBSD etc. *how* PCRE is creating the
> > the JIT'd code? I.e. presumably Google Chrome's JIT engine, Java JIT and
> > the like work on those setup, or not? I.e. is this something upstream
> > can/is likely to fix eventually?
> From the cover letter (but without testing), it seems like it would
> probably be fine to first map the pages read-write to write the code and
> then, once that's done, to map them read-executable. I know JIT
> compilation does work on the BSDs, so presumably that's the technique to
> make it do so.

and that has been implemented (sljitProtExecAllocator.c) as part of the work
triggered by the bug I linked about [1], deep inside sljit (which is
what pcre uses for JIT)

the code AS-IS wouldn't compile for the BSD[2] but that is easy to fix
and sure works as expected but I am under the impression that is not
something that can be considered as a solution as explained by the open issues
described with crashes after a fork()

note that changing the map from read-write to executable will be
prevented by the
same policy so you have to create 2 maps (and therefore a backing file) and I
don't think there is a way to solve that in a foolproof way in a
library which is why
I mentioned more work might be needed to define the right interfaces
so it can be
solved by the application, and that is unlikely to happen with the old library.



  reply	other threads:[~2018-12-10  1:26 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-12-09 23:00 [RFC PATCH 0/2] fallback to interpreter if JIT fails with pcre Carlo Marcelo Arenas Belón
2018-12-09 23:00 ` [RFC PATCH 1/2] grep: fallback to interpreter if JIT fails with pcre1 Carlo Marcelo Arenas Belón
2018-12-09 23:51   ` Ævar Arnfjörð Bjarmason
2018-12-10  0:42     ` brian m. carlson
2018-12-10  1:25       ` Carlo Arenas [this message]
2018-12-10  6:42       ` Junio C Hamano
2018-12-10  8:24       ` Ævar Arnfjörð Bjarmason
2018-12-11 20:11         ` Carlo Arenas
2018-12-11 20:51           ` Ævar Arnfjörð Bjarmason
2018-12-10  6:54     ` Junio C Hamano
2018-12-10  6:48   ` Junio C Hamano
2018-12-09 23:00 ` [RFC PATCH 2/2] grep: fallback to interpreter if JIT fails with pcre2 Carlo Marcelo Arenas Belón
2018-12-10  7:00   ` Junio C Hamano

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