Currently:
* Slices of `AsBytes`/`FromBytes` types cannot be synthesized from
bytes slices (without unsafe).
* Users must use `unsafe impl` to assert that structs are `AsBytes` or
`FromBytes` and write appropriate justifications.
* Bindgen-generated types cannot implement `AsBytes` or `FromBytes`,
meaning that casting them to or from bytes involves assumptions in the
`unsafe impl` that could easily go out of sync if the underlying
header is edited or an assumption is invalid on a platform the author
did not consider.
This series seeks to address all there of these by:
1. Adding slice cast functions to `FromBytes`
2. Adding a derive for `AsBytes` and `FromBytes`, for now restricted to
the simple case of structs.
3. Refactoring the crate structure to move `AsBytes` and `FromBytes` to
`ffi` to allow `bindings` and `uapi` to reference them.
4. Enabling bindgen derivation in `bindings`/`uapi` through `AsBytesFfi`
and `FromBytesFfi`.
1+2 can be landed separately if needed, 3 has no purpose without 4, and
3+4 need 1+2.
Signed-off-by: Matthew Maurer <mmaurer@google.com>
---
Changes in v3:
- Explained the `for<'a>` usage in the where clauses generated by macro.
- Split bindgen support into two commits, one which does the crate
migration and one which enables it.
- Link to v2: https://lore.kernel.org/r/20251216-transmute-v2-0-b23e5277ad02@google.com
Changes in v2:
- Reworked to put `transmute` in `ffi` rather than creating a new crate,
per Alice's comment on Zulip.
- Switched to new kernel import style.
- Link to v1: https://lore.kernel.org/r/20251212-transmute-v1-0-9b28e06c6508@google.com
---
Matthew Maurer (4):
rust: transmute: Support transmuting slices of AsBytes/FromBytes types
rust: transmute: Add support for deriving `AsBytes` and `FromBytes`
rust: transmute: Migrate AsBytes/FromBytes to ffi crate for bindgen
rust: transmute: Support deriving AsBytes/FromBytes on bindgen types
rust/Makefile | 14 ++++---
rust/bindgen_parameters | 8 ++++
rust/bindings/lib.rs | 4 ++
rust/{ffi.rs => ffi/lib.rs} | 5 +++
rust/{kernel => ffi}/transmute.rs | 72 +++++++++++++++++++++++++++++++++
rust/kernel/lib.rs | 2 +-
rust/macros/lib.rs | 83 +++++++++++++++++++++++++++++++++++++++
rust/macros/transmute.rs | 67 +++++++++++++++++++++++++++++++
rust/uapi/lib.rs | 4 ++
scripts/generate_rust_analyzer.py | 2 +-
10 files changed, 254 insertions(+), 7 deletions(-)
---
base-commit: 008d3547aae5bc86fac3eda317489169c3fda112
change-id: 20251212-transmute-8ab6076700a8
Best regards,
--
Matthew Maurer <mmaurer@google.com>