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Message-ID: <20180815004526.GE1878@brightrain.aerifal.cx>
Date: Tue, 14 Aug 2018 20:45:26 -0400
From: Rich Felker <dalias@...c.org>
To: Alexander Revin <lyssdod@...il.com>
Cc: musl@...ts.openwall.com
Subject: Re: Re: musl on a different syscall layer?
On Tue, Aug 14, 2018 at 01:12:56AM +0200, Alexander Revin wrote:
> > On Wed, Sep 17, 2014 at 7:02 PM, <u-wsnj@...ey.se> wrote:
> >> On Wed, Sep 17, 2014 at 01:53:46PM -0400, Rich Felker wrote:
> >>> The main requirement is having equivalent functionality available. On
> >>> the BSD targets I've asked BSD folks about, there's supposedly no
> >>> equivalent of futex except inthe Linux compat layer, which is pretty
> >>> much a show-stopper unless/until it can be remedied. clone is a big
> >>> unknown to me too. The other big potential problem is if the native
> >>> syscall API requires a stack to communicate with the kernel (one or
> >>> more BSDs require this, IIRC), since at least __unmapself needs to be
> >>> able to call SYS_munmap and SYS_exit without a stack.
> >>
> >> Oh I see.
> >>
> >> This means "not much to hope for" (pity but good to know).
>
> > I don't think NetBSD uses the stack for syscalls on any common
> > architecture, maybe on some of the obscure ones, but maybe you don't
> > want to support them.
> >
> > Adding futex support to NetBSD would be an interesting project; it is
> > not in the compat layer at present either, so that is a good reason to
> > add it. NetBSD is pretty friendly...
> >
> > Justin (justin@...bsd.org)
>
> Hi guys, sorry for reviving a dead thread, but do you know if things
> has changed ever since? I'm asking also because it would be nice to
> unify efforts of porting musl to another archs - for example, openrisc
> or m68k - though there're ports for both Linux and NetBSD, libc
> support is kind of scattered over large codebase.
I'm not aware of anything more on the NetBSD side.
Note that "syscalls using stack" is no longer a show-stopper for musl.
There's a portable, albeit less efficient, version of __unmapself that
switches to a shared stack protected by a lock (with the magic exit
futex automatically unlocking it atomically with thread termination).
But this depends on that compat functionality or equivalent.
Rich
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