[PATCH v2 0/3] kcov: collect coverage from usb and vhost

[Andrey Konovalov <andreyknvl@google.com>]

This patchset extends kcov to allow collecting coverage from the USB
subsystem and vhost workers. See the first patch description for details
about the kcov extension. The other two patches apply this kcov extension
to USB and vhost.

These patches have been used to enable coverage-guided USB fuzzing with
syzkaller for the last few years, see the details here:

https://github.com/google/syzkaller/blob/master/docs/linux/external_fuzzing_usb.md

This patchset has been pushed to the public Linux kernel Gerrit instance:

https://linux-review.googlesource.com/c/linux/kernel/git/torvalds/linux/+/1524

Changes v1 -> v2:
- Changed common_handle type back to u64 (to allow extending it in the
  future).
- Reworked kcov_remote_handle() helpers.
- Fixed vhost annotations when CONFIG_KCOV is not enabled.
- Use kcov_disable() instead of kcov_remote_reset() when
  KCOV_REMOTE_ENABLE fails.

Changes RFC v1 -> v1:
- Remove unnecessary #ifdef's from drivers/vhost/vhost.c.
- Reset t->kcov when area allocation fails in kcov_remote_start().
- Use struct_size to calculate array size in kcov_ioctl().
- Add a limit on area_size in kcov_remote_arg.
- Added kcov_disable() helper.
- Changed encoding of kcov remote handle ids, see the documentation.
- Added a comment reference for kcov_sequence task_struct field.
- Change common_handle type to u32.
- Add checks for handle validity into kcov_ioctl_locked() and
    kcov_remote_start().
- Updated documentation to reflect the changes.

Andrey Konovalov (3):
  kcov: remote coverage support
  usb, kcov: collect coverage from hub_event
  vhost, kcov: collect coverage from vhost_worker

 Documentation/dev-tools/kcov.rst | 128 +++++++++
 drivers/usb/core/hub.c           |   5 +
 drivers/vhost/vhost.c            |   6 +
 drivers/vhost/vhost.h            |   1 +
 include/linux/kcov.h             |  23 ++
 include/linux/sched.h            |   6 +
 include/uapi/linux/kcov.h        |  25 ++
 kernel/kcov.c                    | 480 ++++++++++++++++++++++++++++---
 8 files changed, 639 insertions(+), 35 deletions(-)

-- 
2.24.0.rc0.303.g954a862665-goog