[PATCH v2 0/4] PM: hibernate: encrypted snapshots under lockdown

[Sean Rhodes <sean@starlabs.systems>]

v1 was sent as an RFC. This version keeps TPM policy and seed unsealing in
early userspace, while the kernel encrypts and authenticates the uswsusp image
from a locked seed.

The stack adds the snapshot_seed ABI, permits the snapshot device under
lockdown only once encryption is enabled, documents the userspace flow, and
restricts lockdown-time block writes to the active encrypted snapshot
image/header path.

Changes in v2:
- Keep raw writes to active swap blocked under lockdown.
- Track encrypted snapshot bytes and header writes before allowing
  lockdown-time image writes.
- Only split the encrypted stream at the metadata boundary when a user key
  switch is used.
- Return -EFAULT for userspace copy failures.
- Document resume meta_size handling.

Tested on StarFighter MTL with a TPM-sealed seed: encrypted uswsusp
suspend/resume completed and restored the image. Also tested with lockdown
enabled through the encrypted snapshot device path.

Evan Green (1):
  PM: hibernate: add seed-wrapped encrypted snapshots

Sean Rhodes (3):
  PM: hibernate: permit encrypted snapshot device under lockdown
  PM: hibernate: document encrypted snapshot seed ABI
  PM: hibernate: harden encrypted snapshot write path

 Documentation/ABI/testing/sysfs-power   |  14 +
 Documentation/power/userland-swsusp.rst |  20 +
 block/fops.c                            |  55 +-
 include/linux/suspend.h                 |  22 +
 include/linux/swap.h                    |  16 +
 include/uapi/linux/suspend_ioctls.h     |  31 +-
 kernel/power/Kconfig                    |  15 +
 kernel/power/Makefile                   |   1 +
 kernel/power/hibernate.c                |  32 +
 kernel/power/power.h                    |   4 +
 kernel/power/snapenc.c                  | 940 ++++++++++++++++++++++++
 kernel/power/snapshot.c                 |   5 +
 kernel/power/swap.c                     |  98 +++
 kernel/power/user.c                     | 247 ++++++-
 kernel/power/user.h                     | 151 ++++
 mm/swapfile.c                           |  32 +
 16 files changed, 1651 insertions(+), 32 deletions(-)
 create mode 100644 kernel/power/snapenc.c
 create mode 100644 kernel/power/user.h