[PATCH v3 0/6] kernel: introduce uaccess logging

[Peter Collingbourne]

On Wed, Dec 8, 2021 at 7:33 AM Marco Elver <elver at google.com> wrote:
>
> On Wed, 8 Dec 2021 at 05:48, Peter Collingbourne <pcc at google.com> wrote:
> [...]
> > Peter Collingbourne (6):
> >   include: split out uaccess instrumentation into a separate header
> >   uaccess-buffer: add core code
> >   fs: use copy_from_user_nolog() to copy mount() data
> >   uaccess-buffer: add CONFIG_GENERIC_ENTRY support
> >   arm64: add support for uaccess logging
> >   Documentation: document uaccess logging
>
> I think it needs to be possible to disable the feature via a Kconfig
> option. Not all systems want or could even tolerate the additional
> overheads -- even though you say they are minimal elsewhere. For
> example, some embedded systems most likely have absolutely no use for
> this feature, and the increase in .text might be unacceptable. Certain
> features that we usually take for granted are no different (see
> init/Kconfig: FUTEX, EPOLL, .. etc). If you'd like it enabled by
> default, given the overheads are small enough, it can do "default y"
> and be configurable only "if EXPERT".

Okay, done.

> Is it possible to add a kselftest-style test to
> tools/testing/selftests? In addition to the basic tests, can certain
> non-trivial properties, like masking of signals, also be tested? I
> think that'd be extremely valuable, because I'm sure we'd have to
> backport this to several older kernels.

Yes, I've added a new patch with a kselftest. (Good thing I did,
because it (together with DEBUG_PREEMPT) uncovered a bug in the
pre/post-exit-loop code. Fixed in v4.)

Peter