Re: [PATCH] livepatch: Cleanup page permission changes
From: Jiri Kosina
Date: Thu Nov 05 2015 - 04:28:24 EST
On Wed, 4 Nov 2015, Josh Poimboeuf wrote:
> > > int klp_write_module_reloc(struct module *mod, unsigned long type,
> > > unsigned long loc, unsigned long value)
> > > {
> > > - int ret, numpages, size = 4;
> > > - bool readonly;
> > > + int size = 4;
> >
> > BTW I don't see a reason to have 'size' signed here.
>
> It was already signed to begin with, but I can change it to size_t.
Yes, I know, it's not really related to this patchset, but I stumbled upon
it during review.
> > > +#ifdef CONFIG_DEBUG_SET_MODULE_RONX
> > > +static void set_page_attributes(void *start, void *end,
> > > + int (*set)(unsigned long start, int num_pages))
> > > +{
> > > + unsigned long begin_pfn = PFN_DOWN((unsigned long)start);
> > > + unsigned long end_pfn = PFN_DOWN((unsigned long)end);
> > > +
> > > + if (end_pfn > begin_pfn)
> > > + set(begin_pfn << PAGE_SHIFT, end_pfn - begin_pfn);
> > > +}
BTW is there any reason not to make use of the function from module.c
which does exactly the same, instead of copy pasting it all around?
> > > +static void set_module_ro_rw(struct module *mod)
> > > +{
> > > + set_page_attributes(mod->module_core,
> > > + mod->module_core + mod->core_ro_size,
> > > + set_memory_rw);
> > > +}
> > > +static void set_module_ro_ro(struct module *mod)
> >
> > Honestly, I find both the function names above horrible and not really
> > self-explanatory (especially the _ro_ro variant). At least comment,
> > explaining what they are actually doing, or picking up a better name,
> > would make the code much more self-explanatory in my eyes.
>
> Being the patch author, naturally the function names make sense to me.
:)
> set_module_ro_ro() means "set the module's read-only area to have
> read-only permissions."
>
> Do you have any suggestions for a better name?
I'd even say it's superfluous to have the functions at the first place,
and just calling set_page_attributes() directly makes the intent clear
enough already.
Thanks,
--
Jiri Kosina
SUSE Labs
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