Date: Tue, 10 Nov 2015 15:08:18 +0700 From: Рысь <lynx@...xlynx.tk> To: musl@...ts.openwall.com Subject: Re: sys/io.h lacks inb_p and outb_p on x86 On Mon, 9 Nov 2015 17:17:34 -0500 Rich Felker <dalias@...c.org> wrote: > 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 Well, I am not good at assembly right now, so no. While digging this I came to suspection that grabbed versions from uClibc cannot be rewritten as function calls, or I misunderstand assembly (or it's gcc variant) at all. So, after three+ years of experience with musl I just hit this once, and I don't think they worth adding if there is no much interest. memtest86+ uses no libc code, and suddenly only grabs those two from host which is easily patchable. I used uClibc versions just to get a conformant binary. -- http://lynxlynx.tk/ Power electronics made simple Unix and simple KISS C code
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