linux-kernel - Re: [PATCH] modules: Fix build error in moduleloader.h

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Message-ID: <53BB5CAF.5040303@hitachi.com>
Date:	Tue, 08 Jul 2014 11:51:27 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Rusty Russell <rusty@...tcorp.com.au>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Fengguang Wu <fengguang.wu@...el.com>
Subject: Re: [PATCH] modules: Fix build error in moduleloader.h

(2014/07/08 8:40), Rusty Russell wrote:
> Steven Rostedt <rostedt@...dmis.org> writes:
>> Fengguang Wu's build bot detected that if moduleloader.h is included in
>> a C file (used by ftrace and kprobes to access module_alloc() when
>> available), that it can fail to build if CONFIG_MODULES and
>> CONFIG_MODULES_USE_ELF_REL is not defined.
>>
>> This is because there's a printk() that dereferences struct module to
>> print the name of the module. But as struct module does not exist when
>> CONFIG_MODULES is not defined we get this error:
> 
> First, we have module_name() for exactly this.
> 
> Second, there are two places like this: you hit
> CONFIG_MODULES_USE_ELF_REL and not CONFIG_MODULES_USE_ELF_RELA.
> 
> (We could uninline them, and put them in module.c, but I think having
> them in the header is nice and self-documenting.)
> 
> So does this work for you?
> 
> Thanks,
> Rusty.
> PS.  Masami Hiramatsu, your review should have caught the second case,
>      at least :(

Oops, sorry, I missed the second one ... and this version seems good to me.

Thank you,

> 
> Subject: modules: Fix build error in moduleloader.h
> 
> Fengguang Wu's build bot detected that if moduleloader.h is included in
> a C file (used by ftrace and kprobes to access module_alloc() when
> available), that it can fail to build if CONFIG_MODULES and
> CONFIG_MODULES_USE_ELF_REL is not defined.
> 
> This is because there's a printk() that dereferences struct module to
> print the name of the module. But as struct module does not exist when
> CONFIG_MODULES is not defined we get this error:
> 
>    include/linux/moduleloader.h: In function 'apply_relocate':
>>> include/linux/moduleloader.h:48:63: error: dereferencing pointer to
>>> incomplete type  
>      printk(KERN_ERR "module %s: REL relocation unsupported\n", me->name);
> 								  ^
> Reported-by: kbuild test robot <fengguang.wu@...el.com>
> Based-on-the-true-story-by: Steven Rostedt <rostedt@...dmis.org>
> Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>
> 
> diff --git a/include/linux/moduleloader.h b/include/linux/moduleloader.h
> index 560ca53a75fa..7eeb9bbfb816 100644
> --- a/include/linux/moduleloader.h
> +++ b/include/linux/moduleloader.h
> @@ -45,7 +45,8 @@ static inline int apply_relocate(Elf_Shdr *sechdrs,
>  				 unsigned int relsec,
>  				 struct module *me)
>  {
> -	printk(KERN_ERR "module %s: REL relocation unsupported\n", me->name);
> +	printk(KERN_ERR "module %s: REL relocation unsupported\n",
> +	       module_name(me));
>  	return -ENOEXEC;
>  }
>  #endif
> @@ -67,7 +68,8 @@ static inline int apply_relocate_add(Elf_Shdr *sechdrs,
>  				     unsigned int relsec,
>  				     struct module *me)
>  {
> -	printk(KERN_ERR "module %s: REL relocation unsupported\n", me->name);
> +	printk(KERN_ERR "module %s: REL relocation unsupported\n",
> +	       module_name(me));
>  	return -ENOEXEC;
>  }
>  #endif
> 


-- 
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com


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