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From: Rich Felker <dalias@libc.org>
To: Mahesh Bodapati <Mahesh.Bodapati@imgtec.com>
Cc: Szabolcs Nagy <nsz@port70.net>,
	Jaydeep Patil <Jaydeep.Patil@imgtec.com>,
	Anand Takale <Anand.Takale@imgtec.com>,
	musl@lists.openwall.com
Subject: Re: Re: mips n64 porting review
Date: Fri, 12 Feb 2016 13:51:15 -0500	[thread overview]
Message-ID: <20160212185115.GS9349@brightrain.aerifal.cx> (raw)
In-Reply-To: <20160205042734.GV9349@brightrain.aerifal.cx>

On Thu, Feb 04, 2016 at 11:27:34PM -0500, Rich Felker wrote:
> On Thu, Feb 04, 2016 at 06:52:47PM -0500, Rich Felker wrote:
> > On Wed, Feb 03, 2016 at 06:36:57PM -0500, Rich Felker wrote:
> > > On Wed, Feb 03, 2016 at 03:41:13PM +0000, Mahesh Bodapati wrote:
> > > > Hi Rich,
> > > > I have attached the patch which has all the MIPS n64 porting work. I
> > > > have created mips64port remote branch on GitHub and the repository
> > > > is https://github.com/MaheshBodapati/musl/tree/mips64port which has
> > > > the broken down patches and the base revision on which I have
> > > > prepared patch is v1.1.12-41-g3abb094.
> > > 
> > > Some preliminary review:
> > 
> > One more thing that came up in reviewing syscall_cp.s was actually a
> > bug copied from existing code in musl, which is fixed by this commit:
> > 
> > http://git.musl-libc.org/cgit/musl/commit/?id=756c8af8589265e99e454fe3adcda1d0bc5e1963
> > 
> > In practice the code seemed to work but it was wrong with respect to
> > ABI requirements.
> > 
> > I think the way you're saving $gp on the stack in sigsetjmp.s is also
> > invalid since that part of the stack will have been clobbered by the
> > time setjmp returns a second time. You could save it inside an unused
> > part of the jump buffer, but it might be better to just avoid the $gp
> > register and instead use temp registers and possibly some pc-relative
> > address computations.
> 
> Likewise in pipe.s, it's overly complicated by the fact that it's
> saving $gp on the stack and thereby can't make a tail call to
> __syscall_ret like it's intended to. If you just use a different
> register instead of $gp that's call-clobbered you can tail-call just
> like the 32-bit mips version. Alternatively it's possible now to write
> src/unistd/mips64/pipe.c instead using inline asm and let the compiler
> handle the nastiness of the calling convention. I'd be happy with
> either approach; the C version is probably mildly nicer, especially if
> the compiler still does the tail-call right and doesn't generate come
> bloated monstrosity. (Note that you can't use C for sigsetjmp though
> because it can't use the stack.)
> 
> At this point I think I've looked through all the mips64 files at
> least once and caught all the important issues.

Ping. Any questions or updates on mips64?

Rich


  reply	other threads:[~2016-02-12 18:51 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <DE16056458B9894F9D46202EC1BBB28B3BDC3210@PUMAIL01.pu.imgtec.org>
2016-02-03 23:36 ` Rich Felker
2016-02-04 23:52   ` Rich Felker
2016-02-05  4:27     ` Rich Felker
2016-02-12 18:51       ` Rich Felker [this message]
2016-02-15  4:46         ` Jaydeep Patil
2016-02-04  0:45 ` Szabolcs Nagy

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