Messages in this thread | | | From | Linus Torvalds <> | Date | Sun, 1 Oct 2023 13:48:21 -0700 | Subject | Re: Linux 6.6-rc3 (DEBUG_VIRTUAL is unhappy on x86) |
| |
On Sun, 1 Oct 2023 at 07:17, Hyeonggon Yoo <42.hyeyoo@gmail.com> wrote: > > > > > Peter Zijlstra (1): > > > x86,static_call: Fix static-call vs return-thunk > > > > Hello, the commit above caused a crash on x86 kernel with > > CONFIG_DEBUG_VIRTUAL=y. > > OK, I looked into this a little bit, and it turns out that the problematic > address here is from cleanup_trusted() in > security/keys/trusted-keys/trusted_core.c. > (and it's builtin due to CONFIG_TRUSTED_KEYS=y) > > The function is marked as __exit, so it does not fall within the > 'core kernel text address range,' which is between _stext and _etext > (or between _sinittext and _einittext). and thus __text_poke() thinks that > it's vmalloc/module area. > > I think __text_poke() should be taught that functions marked as __exit > also belong to kernel code just like __init.
I think your patch is fine (well, whitespace-damaged, but conceptually good).
But I also wonder about that
static_call_cond(trusted_key_exit)();
in cleanup_trusted(). It seems all kinds of pointless to use static calls for something that is done *once*. That's not an optimization, that's honestly just _stupid_. It costs more to do the rewriting that it does to just do the one dynamic indirect call.
Side note: the same is true of the init-time call, which does
static_call_update(trusted_key_init, trusted_key_sources[i].ops->init); ... ret = static_call(trusted_key_init)();
which again is a *lot* more expensive than just doing the indirect function call.
So while I don't think your patch is wrong, I do think that the cause here is plain silly code, and that trusted key code simply should not do the crazy thing it does (and that causes silly problems).
Linus
| |