Messages in this thread | | | Date | Fri, 18 Feb 2022 09:25:11 -0800 | From | Ira Weiny <> | Subject | Re: [PATCH V8 19/44] mm/pkeys: PKS Testing, add pks_mk_*() tests |
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On Fri, Feb 18, 2022 at 07:28:04AM -0800, Dave Hansen wrote: > On 2/17/22 21:34, Ira Weiny wrote: > > On Tue, Feb 01, 2022 at 09:45:03AM -0800, Dave Hansen wrote: > >> On 1/27/22 09:54, ira.weiny@intel.com wrote: > >>> bool pks_test_callback(void) > >>> { > >>> - return false; > >>> + bool armed = (test_armed_key != 0); > >>> + > >>> + if (armed) { > >>> + pks_mk_readwrite(test_armed_key); > >>> + fault_cnt++; > >>> + } > >>> + > >>> + return armed; > >>> +} > >> > >> Where's the locking for all this? I don't think we need anything fancy, > >> but is there anything preventing the test from being started from > >> multiple threads at the same time? I think a simple global test mutex > >> would probably suffice. > > > > Good idea. Generally I don't see that happening but it is good to be safe. > > I'm not sure what you mean. > > In the kernel, we always program as if userspace is out to get us. If > userspace can possibly do something to confuse the kernel, it will. It > might be malicious or incompetent, but it will happen. > > This isn't really a "good to be safe" kind of thing. Kernel code must > *be* safe.
Yes
> > >> Also, pks_test_callback() needs at least a comment or two about what > >> it's doing. > > > > The previous patch which adds this call in the fault handler contains the > > following comment which is in the final code: > > > > /* > > * pks_test_callback() is called by the fault handler to indicate it saw a pkey > > * fault. > > * > > * NOTE: The callback is responsible for clearing any condition which would > > * cause the fault to re-trigger. > > */ > > > > Would you like more comments within the function? > > Ahh, it just wasn't in the context. > > Looking at this again, I don't really like the name "callback" is almost > always a waste of bytes. Imagine this was named something like: > > pks_test_induced_fault(); > > ... and had a comment like: > > /* > * Ensure that the fault handler does not treat > * test-induced faults as actual errors. > */
Ok. At this point this may go away depending on how I resolve the ability to test all the keys. pks_test_callback() was critical for that feature without introducing a bunch of ugly test code in pks-keys.h and pkeys.c.
> > >> Does this work if you have a test armed and then you get an unrelated > >> PKS fault on another CPU? I think this will disarm the test from the > >> unrelated thread. > > > > This code will detect a false fault. > > That's a bug that's going to get fixed, right? ;)
Yep. Not sure how at the moment.
Ira
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