linux-kernel - Re: [ANNOUNCE] OSS Proxy using CUSE

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <48B736E7.5000407@kernel.org>
Date:	Thu, 28 Aug 2008 16:38:15 -0700
From:	"H. Peter Anvin" <hpa@...nel.org>
To:	Greg KH <greg@...ah.com>
CC:	Adrian Bunk <bunk@...nel.org>, Tejun Heo <tj@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Miklos Szeredi <miklos@...redi.hu>,
	Takashi Iwai <tiwai@...e.de>, fuse-devel@...ts.sourceforge.net
Subject: Re: [ANNOUNCE] OSS Proxy using CUSE

Greg KH wrote:
> 
> Hm, why?  It's a "fake" serial port as it is just a pass-through to the
> USB device.  No flow control or line settings work on the device, so the
> kernel driver just silently eats them.  But there is old, closed source
> software that wants to talk to a serial port, so the kernel driver
> remains.  With this code, we could then use the more modern libusb code
> instead.
> 
> I guess you could hook it up through a pty, and somehow create
> /dev/pilot/ for it as well, that is an idea to consider.
> 

Why?  Because there is a lot of complexity in the tty layer, and there 
is no point in replicating the entire tty layer with all its ioctls 
through a fragile user-space emulator.  For cases like this, a pty is 
easier (your daemon opens /dev/ptmx, and then symlinks the appropriate 
pty to /dev/pilot) and works better.

>> The big problem with using ptys for serial port emulation is that they 
>> currently don't handle BREAK at all.
> 
> For this type of USB device, that's not an issue :)

Indeed.  It would be nice to fix, because it would make implementing 
serial ports as ptys+userspace a much more capable replacement.  It's 
not trivial, though, because the interpretation of the BREAK has to be 
done when received, not when sent, which means supporting a 257th value 
in the underlying buffer setup.

	-hpa
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/