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Message-ID: <20151109221734.GR3818@brightrain.aerifal.cx>
Date: Mon, 9 Nov 2015 17:17:34 -0500
From: Rich Felker <dalias@...c.org>
To: musl@...ts.openwall.com
Subject: Re: sys/io.h lacks inb_p and outb_p on x86
On Sun, Nov 08, 2015 at 12:23:58AM -0500, Rich Felker wrote:
> On Sun, Nov 08, 2015 at 12:13:37PM +0700, Рысь wrote:
> > On Sat, 7 Nov 2015 23:50:45 -0500
> > Rich Felker <dalias@...c.org> wrote:
> >
> > > On Sun, Nov 08, 2015 at 11:26:55AM +0700, Рысь wrote:
> > > > x86 arch lacks inb_p and outb_p inline functions. This is required
> > > > for memtest86+.
> > > >
> > > > I don't know how properly make an assembly here, so when making
> > > > memtest I copied sys/io.h into local directory, and copied these
> > > > functions from uClibc.
> > > >
> > > > I attach modified header for reference (they should go into
> > > > bits/io.h).
> > >
> > > Any idea what these are intended to do? Are they documented anywhere?
> > >
> > > Rich
> >
> > I can't say much, but looking into memtest code I see they're used only
> > for beeping a PC speaker.
> >
> > Comment in io.h include file of memtest says:
> >
> > * This file contains the definitions for the x86 IO instructions
> > * inb/inw/inl/outb/outw/outl and the "string versions" of the same
> > * (insb/insw/insl/outsb/outsw/outsl). You can also use "pausing"
> > * versions of the single-IO instructions (inb_p/inw_p/..).
> >
> > However memtest builds with assumption they're present in sys/io.h from
> > host and io.h included with memtest does not define inb_p/outb_p in any
> > way.
> >
> > I probably will go with uClibc defines, or just nop memtest beeper.
>
> See http://stackoverflow.com/questions/6793899/what-does-the-0x80-port-address-connects
>
> So apparently these are convenience functions to show the most recent
> port io that was performed on a hardware debugging device in case the
> memtest crashes. I don't mind adding them is software expects them to
> be there, but they should be written in terms of the existing
> functions rather than duplicating asm.
Hmm, according to the man page this is actually to "pause". See:
http://man7.org/linux/man-pages/man2/outb.2.html
Of course there's also all kinds of nonsense claiming they won't work
with -O0, so I'm not sure what to believe.
If you want these, can you prepare a patch adding all 6 *_p functions
as calls to plain in[bwl]/out[bwl] followed by a call to outb to port
0x80?
Rich
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