linux-kernel - Re: [RFC PATCH v3 4/6] livepatch: reuse module loader code to write relocations

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Date:	Wed, 13 Jan 2016 10:31:10 +0100 (CET)
From:	Jiri Kosina <jikos@...nel.org>
To:	Miroslav Benes <mbenes@...e.cz>
cc:	Jessica Yu <jeyu@...hat.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Josh Poimboeuf <jpoimboe@...hat.com>,
	Seth Jennings <sjenning@...hat.com>,
	Vojtech Pavlik <vojtech@...e.com>,
	Jonathan Corbet <corbet@....net>, linux-api@...r.kernel.org,
	live-patching@...r.kernel.org, x86@...nel.org,
	linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
	linux-doc@...r.kernel.org
Subject: Re: [RFC PATCH v3 4/6] livepatch: reuse module loader code to write
 relocations

On Wed, 13 Jan 2016, Miroslav Benes wrote:

> >  {
> > -	int ret = 0;
> > -	unsigned long val;
> > -	struct klp_reloc *reloc;
> > +	int i, len, ret = 0;
> > +	char *secname;
> > +	const char *objname;
> >  
> >  	if (WARN_ON(!klp_is_object_loaded(obj)))
> >  		return -EINVAL;
> >  
> > -	if (WARN_ON(!obj->relocs))
> > -		return -EINVAL;
> > +	objname = klp_is_module(obj) ? obj->name : "vmlinux";
> >  
> >  	module_disable_ro(pmod);
> > +	/* For each klp rela section for this object */
> > +	for (i = 1; i < pmod->info->hdr->e_shnum; i++) {
> > +		if (!(pmod->info->sechdrs[i].sh_flags & SHF_RELA_LIVEPATCH))
> > +			continue;
> 
> One more thing. If the module does not specify it is a live patch module 
> in modinfo (with MODULE_INFO(livepatch, "Y")), but it is a perfect live 
> patch module otherwise (it calls klp_register_patch in its init function), 

Side note: I think we should at least issue some light warning in such 
case anyway.

-- 
Jiri Kosina
SUSE Labs