On Mon, Nov 30, 2015 at 02:46:18PM -0600, Chris J Arges wrote:
> On Mon, Nov 23, 2015 at 10:52:23AM +0100, Miroslav Benes wrote:
> > On Fri, 20 Nov 2015, Chris J Arges wrote:
> >
> > [...]
> >
> > > @@ -272,6 +233,7 @@ static int klp_write_object_relocations(struct module
> > > *pmod,
> > > struct klp_object *obj)
> > > {
> > > int ret;
> > > + unsigned long val;
> > > struct klp_reloc *reloc;
> > >
> > > if (WARN_ON(!klp_is_object_loaded(obj)))
> > > @@ -281,29 +243,26 @@ static int klp_write_object_relocations(struct
> > > module *pmod,
> > > return -EINVAL;
> > >
> > > for (reloc = obj->relocs; reloc->name; reloc++) {
> > > - if (!klp_is_module(obj)) {
> > > - ret = klp_verify_vmlinux_symbol(reloc->name,
> > > - reloc->val);
> > > - if (ret)
> > > - return ret;
> > > - } else {
> > > - /* module, reloc->val needs to be discovered */
> > > - if (reloc->external)
> > > - ret = klp_find_external_symbol(pmod,
> > > - reloc->name,
> > > - &reloc->val);
> > > - else
> > > - ret = klp_find_object_symbol(obj->mod->name,
> > > - reloc->name,
> > > - 0, &reloc->val);
> > > - if (ret)
> > > - return ret;
> > > - }
> > > + /* discover the address of the referenced symbol */
> > > + if (reloc->external) {
> > > + if (reloc->sympos > 0) {
> > > + pr_err("non-zero sympos for external reloc
> > > symbol '%s' is not supported\n",
> > > + reloc->name);
> > > + return -EINVAL;
> > > + }
> > > + ret = klp_find_external_symbol(pmod, reloc->name, &val);
> > > + } else
> > > + ret = klp_find_object_symbol(obj->mod->name,
> > > + reloc->name,
> > > + reloc->sympos,
> > > + &val);
> >
> > I think this will cause an unwanted effect if a relocation is for vmlinux
> > symbol. obj->mod is NULL in that case. So obj->name should be there. Can
> > you test it with kpatch, Chris, please? If that is possible.
> >
> > Thanks,
> > Miroslav
> >
>
> Yes I need to fix this, an option would be to use:
> ret = klp_find_object_symbol(obj->name ? obj->name : obj->mod->name,
> reloc->name, 0, &reloc->val);
Instead of
'obj->name ? obj->name : obj->mod->name'
I think it can just be 'obj->name'.
If it's patching a module, obj->name will be the module name, otherwise
it will be NULL (for patching vmlinux). klp_find_object_symbol() is
equipped to handle it either way.
--
Josh
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