linux-kernel - Re: [RFC PATCH v2 4/6] livepatch: reuse module loader code to write relocations

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Message-ID: <20151210211232.GB4934@treble.redhat.com>
Date:	Thu, 10 Dec 2015 15:12:32 -0600
From:	Josh Poimboeuf <jpoimboe@...hat.com>
To:	Jiri Kosina <jikos@...nel.org>
Cc:	Minfei Huang <mnfhuang@...il.com>, Jessica Yu <jeyu@...hat.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Seth Jennings <sjenning@...hat.com>,
	Vojtech Pavlik <vojtech@...e.com>,
	Jonathan Corbet <corbet@....net>,
	Miroslav Benes <mbenes@...e.cz>, 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 v2 4/6] livepatch: reuse module loader code to write
 relocations

On Thu, Dec 10, 2015 at 08:56:27PM +0100, Jiri Kosina wrote:
> On Thu, 10 Dec 2015, Minfei Huang wrote:
> 
> > > +	klp_for_each_reloc_sec(obj, reloc_sec) {
> > > +		relindex = reloc_sec->index;
> > > +		num_relas = pmod->sechdrs[relindex].sh_size / sizeof(Elf_Rela);
> > > +		rela = (Elf_Rela *) pmod->sechdrs[relindex].sh_addr;
> > > +
> > > +		/* For each rela in this __klp_rela section */
> > > +		for (i = 0; i < num_relas; i++, rela++) {
> > > +			sym = symtab + ELF_R_SYM(rela->r_info);
> > > +			symname = pmod->core_strtab + sym->st_name;
> > > +
> > > +			if (sym->st_shndx == SHN_LIVEPATCH) {
> > > +				if (sym->st_info == 'K')
> > > +					ret = klp_find_external_symbol(pmod, symname, &addr);
> > > +				else
> > > +					ret = klp_find_object_symbol(obj->name, symname, &addr);
> > > +				if (ret)
> > > +					return ret;
> > > +				sym->st_value = addr;
> > > +			}
> > >  		}
> > > +		ret = apply_relocate_add(pmod->sechdrs, pmod->core_strtab,
> > > +					 pmod->index.sym, relindex, pmod);
> > 
> > It is more appropiate to test the ret.
> 
> And if error is encountered ... then you'd propose to do what?
> 
> The code is correct as is; the return value is propagated properly to 
> caller, and all the existing callers have proper error handling.

apply_relocate_add() is called from inside a loop, so if there's an
error, it should return immediately instead of continuing the next
iteration.

-- 
Josh
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