linux-kernel - Re: optimizing out inline functions

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:	Wed, 28 May 2008 20:04:22 -0700
From:	Joe Perches <joe@...ches.com>
To:	Johannes Weiner <hannes@...urebad.de>
Cc:	James Kosin <jkosin@...a.intcomgrp.com>,
	linux-kernel@...r.kernel.org
Subject: Re: optimizing out inline functions

On Thu, 2008-05-29 at 05:27 +0200, Johannes Weiner wrote:
> James Kosin <jkosin@...a.intcomgrp.com> writes:
> >> But we do not have KCONFIG_DEBUG_SOMETHING available
> >> so the second best is to use an empty function
> >> to keep the typechecking in place.
> >> IIRC gcc optimize both away.
> > Another way would be to have:
> > static inline void some_debug_function(var1)
> > {
> >    #ifdef KCONFIG_DEBUG_SOMETHING
> >       something = var1;
> >       printk(some debug text);
> >    #endif
> > }

A potential issue is a possible unnecessary call of any
function used as an argument to some_debug_function.

int unnecessary_debug_test(void)
{
	int foo;
	[]
	return foo;
}

static inline void some_debug_function(int bar)
{
}

some_debug_function(unnecessary_debug_test())

unnecessary_debug_test will still get called

Macro wrappers/statement expressions can be used to avoid
the function call.  see kernel.h/pr_debug for an example.

#ifdef DEBUG
/* If you are writing a driver, please use dev_dbg instead */
#define pr_debug(fmt, arg...) \
	printk(KERN_DEBUG fmt, ##arg)
#else
#define pr_debug(fmt, arg...) \
	({ if (0) printk(KERN_DEBUG fmt, ##arg); 0; })
#endif


--
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/