linux-kernel - Re: [PATCH v3 7/7] dynamic_debug: add jump label 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 for Android: free password hash cracker in your pocket

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

Message-Id: <20160708144124.fa0b4d55aaf7e1d61a943d40@linux-foundation.org>
Date:	Fri, 8 Jul 2016 14:41:24 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Jason Baron <jbaron@...mai.com>
Cc:	joe@...ches.com, peterz@...radead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 7/7] dynamic_debug: add jump label support

On Wed,  6 Jul 2016 17:42:36 -0400 Jason Baron <jbaron@...mai.com> wrote:

> Although dynamic debug is often only used for debug builds, sometimes its
> enabled for production builds as well. Minimize its impact by using jump
> labels. This reduces the text section by 7000+ bytes in the kernel image
> below. It does increase data, but this should only be referenced when
> changing the direction of the branches, and hence usually not in cache.
> 
> ...
>
> +#ifdef HAVE_JUMP_LABEL
> +
> +#define dd_key_init(key, init) key = (init)
>
> ...
>
> +#else
> +
> +#define dd_key_init(key, init)
> +

umm, lazy.  One is an lval and returns a value and the other does
neither.  Lack of parenthesization in the first version doubtless
exposes various horrors.

Care to do something more robust and conventional here?  Presumably use
symmetrical do{}while(0) things, neither of which is an lval, both of
which don't return anything.