Re: module: save load_info for livepatch modules

[Jessica Yu]

+++ Miroslav Benes [13/11/15 13:56 +0100]:
> On Fri, 13 Nov 2015, Miroslav Benes wrote:
>
> > I agree this seems like the best approach. So if we preserve
> > mod_arch_syminfo (in case of s390) we should free it not in
> > module_finalize, but somewhere in free_module... where
> > module_arch_cleanup() is called... and also module_arch_freeing_init() is
> > called there too. And what you find there for s390 is
> >
> > 	vfree(mod->arch.syminfo);
> > 	mod->arch.syminfo = NULL;
> >
> > Well, it does nothing here, because mod->arch.syminfo is already NULL. It
> > was freed in module_finalize. So we can even remove this code from
> > module_finalize and all should be fine. At least for s390.
>
> Which is not true because module_arch_freeing_init is also called from
> do_init_module, called from load_module. So we should move it to
> module_arch_cleanup.
>
> That code is like a maze without Ariadne's thread.

Heh, I agree with that sentiment.

I am slightly confused about the s390 code, and whether the authors
originally intended for that double vfree() to happen in both
module_finalize() and module_arch_freeing_init() (called from
do_init_module). Seems like a mistake. If module load succeeds,
do_init_module calls module_arch_freeing_init(). And if load_module
fails halfway through, both module_deallocate() and free_module() will
also call module_arch_freeing_init(). I feel like that vfree should
only happen once in module_arch_freeing_init() and not in
module_finalize(). If we can remove the double vfree() code from
module_finalize(), we can copy the mod_arch_specific safely before the
call to do_init_module().

Jessica
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