linux-kernel - Re: [PATCH 10/13] module: pass struct find_symbol_args to find

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Date:   Tue, 2 Feb 2021 15:07:51 +0100 (CET)
From:   Miroslav Benes <mbenes@...e.cz>
To:     Christoph Hellwig <hch@....de>
cc:     Frederic Barrat <fbarrat@...ux.ibm.com>,
        Andrew Donnellan <ajd@...ux.ibm.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, Jessica Yu <jeyu@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Jiri Kosina <jikos@...nel.org>, Petr Mladek <pmladek@...e.com>,
        Joe Lawrence <joe.lawrence@...hat.com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        dri-devel@...ts.freedesktop.org, live-patching@...r.kernel.org,
        linux-kbuild@...r.kernel.org
Subject: Re: [PATCH 10/13] module: pass struct find_symbol_args to
 find_symbol

>  void *__symbol_get(const char *symbol)
>  {
> -	struct module *owner;
> -	const struct kernel_symbol *sym;
> +	struct find_symbol_arg fsa = {
> +		.name	= symbol,
> +		.gplok	= true,
> +		.warn	= true,
> +	};
>  
>  	preempt_disable();
> -	sym = find_symbol(symbol, &owner, NULL, NULL, true, true);
> -	if (sym && strong_try_module_get(owner))
> -		sym = NULL;
> +	if (!find_symbol(&fsa) || !strong_try_module_get(fsa.owner)) {

I think this should be in fact

  if (!find_symbol(&fsa) || strong_try_module_get(fsa.owner)) {

to get the logic right (note the missing !). We want to return NULL if 
strong_try_module_get() does not succeed for a found symbol.

> +		preempt_enable();
> +		return NULL;
> +	}
>  	preempt_enable();
> -
> -	return sym ? (void *)kernel_symbol_value(sym) : NULL;
> +	return (void *)kernel_symbol_value(fsa.sym);
>  }
>  EXPORT_SYMBOL_GPL(__symbol_get);

Miroslav