linux-kernel - Re: [PATCH 5/7] Ksplice: Add functions for walking kallsyms symbols

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Date:	Wed, 4 Feb 2009 22:00:50 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Jeff Arnold <jbarnold@....edu>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Denys Vlasenko <vda.linux@...glemail.com>,
	Tim Abbott <tabbott@....edu>, Anders Kaseorg <andersk@....edu>,
	Waseem Daher <wdaher@....edu>,
	Nikanth Karthikesan <knikanth@...e.de>
Subject: Re: [PATCH 5/7] Ksplice: Add functions for walking kallsyms symbols

On Saturday 06 December 2008 10:33:58 Jeff Arnold wrote:
> From: Anders Kaseorg <andersk@....edu>
> 
> kallsyms_lookup_name only returns the first match that it finds.  Ksplice
> needs information about all symbols with a given name in order to correctly
> resolve local symbols.
> 
> kallsyms_on_each_symbol provides a generic mechanism for iterating over the
> kallsyms table.

Seems reasonable.  Did you really not want a name-filtering version?  That
might be generally useful.

> +/* Call a function on each kallsyms symbol in the core kernel */
> +int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
> +				      unsigned long),
> +			    void *data);

But does no locking at all.  It either needs a comment that it can only be
called from inside stop_machine, or that it needs preempt disabled, or
whatever.

> +static inline int kallsyms_on_each_symbol(int (*fn)(void *, const char *,
> +						    struct module *,
> +						    unsigned long),
> +					  void *data)
> +{
> +	return 0;
> +}

Is the !CONFIG_KALLSYMS version useful to you?  If not, please don't
implement the noop version.  I want someone who *does* expect it to work to
have to think about it if they use it...

Thanks,
Rusty.
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