On Tue, Aug 18, 2020 at 08:30:29AM +0300, Jarkko Sakkinen wrote:
> On Sun, Jul 26, 2020 at 11:14:08AM +0300, Mike Rapoport wrote:
> > >
> > > I'm not still sure that I fully understand this feedback as I don't see
> > > any inherent and obvious difference to the v4. In that version fallbacks
> > > are to module_alloc() and module_memfree() and text_alloc() and
> > > text_memfree() can be overridden by arch.
> >
> > The major difference between your v4 and my suggestion is that I'm not
> > trying to impose a single ARCH_HAS_TEXT_ALLOC as an alternative to
> > MODULES but rather to use per subsystem config option, e.g.
> > HAVE_KPROBES_TEXT_ALLOC.
> >
> > Another thing, which might be worth doing regardless of the outcome of
> > this discussion is to rename alloc_insn_pages() to text_alloc_kprobes()
> > because the former is way too generic and does not emphasize that the
> > instruction page is actually used by kprobes only.
>
> What if we in kernel/kprobes.c just:
>
> #ifndef CONFIG_ARCH_HAS_TEXT_ALLOC
I don't think that CONFIG_ARCH_HAS_TEXT_ALLOC will work for all
architectures.
If an architecture has different restrictions for allocation of text
for, say, modules, kprobes, bfp, it won't be able to use a single
ARCH_HAS_TEXT_ALLOC. Which means that this architecture is stuck with
dependency of kprobes on MODULES until the next rework.
> void __weak *alloc_insn_page(void)
> {
> return module_alloc(PAGE_SIZE);
> }
>
> void __weak free_insn_page(void *page)
> {
> module_memfree(page);
> }
> #endif
>
> In Kconfig (as in v5):
>
> config KPROBES
> bool "Kprobes"
> depends on MODULES || ARCH_HAS_TEXT_ALLOC
>
> I checked architectures that override alloc_insn_page(). With the
> exception of x86, they do not call module_alloc().
>
> If no rename was done, then with this approach a more consistent.
> config flag name would be CONFIG_ARCH_HAS_ALLOC_INSN_PAGE.
>
> I'd call the function just as kprobes_alloc_page(). Then the
> config flag would become CONFIG_HAS_KPROBES_ALLOC_PAGE.
>
> > --
> > Sincerely yours,
> > Mike.
>
> Thanks for the feedback!
>
> /Jarkko
--
Sincerely yours,
Mike.
