linux-kernel - Re: [RFC] LZO de/compression support

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: <Pine.LNX.4.61.0705292236490.11140@yvahk01.tjqt.qr>
Date:	Tue, 29 May 2007 22:48:45 +0200 (MEST)
From:	Jan Engelhardt <jengelh@...ux01.gwdg.de>
To:	Nitin Gupta <nitingupta910@...il.com>
cc:	lkml <linux-kernel@...r.kernel.org>, linux-mm-cc@...top.org,
	linuxcompressed-devel@...ts.sourceforge.net,
	Andrew Morton <akpm@...ux-foundation.org>,
	Daniel Hazelton <dhazelton@...er.net>,
	Richard Purdie <richard@...nedhand.com>,
	Bret Towe <magnade@...il.com>,
	Satyam Sharma <satyam.sharma@...il.com>
Subject: Re: [RFC] LZO de/compression support - take 6


On May 28 2007 20:04, Nitin Gupta wrote:
>
> * Changelog vs. original LZO:
> 1) Used standard/kernel defined data types: (this eliminated _huge_
> #ifdef chunks)
> lzo_bytep -> unsigned char *
> lzo_uint -> size_t
> lzo_xint -> size_t

Is this safe (as far as compressed LZO stream is concerned) --
or is it even needed (could it be unsigned int)? 

> -                             m_pos -= (*(const unsigned short *)ip) >> 2;
> -#else
> -                             m_pos = op - 1;
> -                             m_pos -= (ip[0] >> 2) + (ip[1] << 6);
> -#endif
>
> + m_pos = op - 1 - (cpu_to_le16(*(const u16 *)ip) >> 2);
>
> (Andrey suggested le16_to_cpu for above but I think it should be cpu_to_le16).
> *** Need testing on big endian machine ***

On i386, both cpu_to_le16 and le16_to_cpu do nothing.
On sparc for example, cpu_to_leXX and leXX_to_cpu do 'the same' ;-)
they swap 1234<->4321.

It is the bytestream (ip) that is reinterpreted as uint16_t.
And I really doubt that the LZO author has a big-endian machine,
given the days of ubiquitous x86. le16_to_cpu it is.



	Jan
-- 
-
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/