From: James Bottomley <James.Bottomley@HansenPartnership.com>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Parisc List <linux-parisc@vger.kernel.org>
Subject: Re: what's parisc execve_wrapper doing in the end?
Date: Thu, 04 Oct 2012 10:30:19 +0100 [thread overview]
Message-ID: <1349343019.2706.3.camel@dabdike.int.hansenpartnership.com> (raw)
In-Reply-To: <20121004045150.GH23473@ZenIV.linux.org.uk>
[parisc list added just in case I get this wrong]
On Thu, 2012-10-04 at 05:51 +0100, Al Viro wrote:
> I'm really confused by that one:
> /* If exec succeeded we need to load the args */
>
> ldo -1024(%r0),%r1
> cmpb,>>= %r28,%r1,error_\execve
> copy %r2,%r19
>
> error_\execve:
> bv %r0(%r19)
>
> Just what is going on there? That cmpb is non-nullifying, right?
Right, it would have to have a ,n to nullify the following instruction,
so the copy is executed in both branches.
The compare and branch clearly has no effect, so it's a vestige of
something, I think.
> So this
> assignment to %r2 happens whether condition is true or false. And AFAICS
> IAOQ_Next is set to error_\execve in both cases. So what the hell
> is that comparison for (and the comment about)? Why not simply return
> via bv %r0(%r2) and be done with that? It had been done that way since
> the initial parisc merge circa 2.4.0-test*...
Right, but no idea what it's a vestige of.
James
next parent reply other threads:[~2012-10-04 9:30 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20121004045150.GH23473@ZenIV.linux.org.uk>
2012-10-04 9:30 ` James Bottomley [this message]
2012-10-05 11:07 ` what's parisc execve_wrapper doing in the end? James Bottomley
2012-10-05 13:44 ` James Bottomley
2012-10-05 14:47 ` James Bottomley
2012-10-05 14:48 ` Al Viro
2012-10-05 14:55 ` James Bottomley
2012-10-05 19:21 ` Al Viro
2012-10-05 23:04 ` Al Viro
2012-10-08 11:28 ` James Bottomley
2012-10-09 9:55 ` James Bottomley
2012-10-10 4:26 ` Al Viro
2012-10-05 22:54 ` John David Anglin
2012-10-05 23:32 ` Al Viro
2012-10-06 0:15 ` John David Anglin
[not found] ` <20121004051359.GA24664@ZenIV.linux.org.uk>
2012-10-04 10:02 ` James Bottomley
2012-10-04 12:22 ` Al Viro
2012-10-04 12:57 ` James Bottomley
2012-10-04 13:30 ` Carlos O'Donell
2012-10-04 14:07 ` Al Viro
2012-10-05 0:00 ` John David Anglin
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