linux-kernel - Re: [PATCH] x86: always_inline wrapper for x86's test

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]

Date:	Sun, 13 Apr 2008 20:16:42 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Alexander van Heukelum <heukelum@...tmail.fm>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Alexander van Heukelum <heukelum@...lshack.com>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: always_inline wrapper for x86's test_bit

> I have googled, but the only problem I found was concerning dead code 

It might come as a surprise, but google is still not omniscient.

> elimination, and in particular references to unavailable object from
> code that was expected to be discarded. The worst that can happen in 
> this case is that gcc might produce a strange construction where a
> runtime check will choose between the two alternative implementations of
> test_bit. Another is that it will select the 'wrong' implementation. 
> Both will result is some code-bloat, but at least the code should work
> properly.

Yes, but extreme code bloat can be fatal.

> I have not checked with 3.2. The oldest compiler I have available here
> is 3.3. That version compiles the functions as expected: I have found
> instances of either type in the objdump and I have not found strange
> constructions with both types there.

It would be good to check on 3.2 too to avoid potential nasty surprises.

> If you were thinking of another/bigger problem with gcc-3.2, could you 
> please give me a pointer?

Not sure what you mean here.

-Andi
--
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/