Trusted PTR_TO_BTF_ID arg support in global subprogs #6349
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Add support for passing PTR_TO_BTF_ID registers to global subprogs. Currently only PTR_TRUSTED flavor of PTR_TO_BTF_ID is supported. Non-NULL semantics is assumed, so caller will be forced to prove PTR_TO_BTF_ID can't be NULL. Note, we disallow global subprogs to destroy passed in PTR_TO_BTF_ID arguments, even the trusted one. We achieve that by not setting ref_obj_id when validating subprog code. This basically enforces (in Rust terms) borrowing semantics vs move semantics. Borrowing semantics seems to be a better fit for isolated global subprog validation approach. Implementation-wise, we utilize existing logic for matching user-provided BTF type to kernel-side BTF type, used by BPF CO-RE logic and following same matching rules. We enforce a unique match for types. Acked-by: Eduard Zingerman <eddyz87@gmail.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Add ability to mark arg:trusted arguments with optional arg:nullable tag to mark it as PTR_TO_BTF_ID_OR_NULL variant, which will allow callers to pass NULL, and subsequently will force global subprog's code to do NULL check. This allows to have "optional" PTR_TO_BTF_ID values passed into global subprogs. For now arg:nullable cannot be combined with anything else. Acked-by: Eduard Zingerman <eddyz87@gmail.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Add __arg_trusted to annotate global func args that accept trusted PTR_TO_BTF_ID arguments. Also add __arg_nullable to combine with __arg_trusted (and maybe other tags in the future) to force global subprog itself (i.e., callee) to do NULL checks, as opposed to default non-NULL semantics (and thus caller's responsibility to ensure non-NULL values). Acked-by: Eduard Zingerman <eddyz87@gmail.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Add a bunch of test cases validating behavior of __arg_trusted and its combination with __arg_nullable tag. We also validate CO-RE flavor support by kernel for __arg_trusted args. Acked-by: Eduard Zingerman <eddyz87@gmail.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
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At least one diff in series https://patchwork.kernel.org/project/netdevbpf/list/?series=821094 irrelevant now. Closing PR. |
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Pull request for series with
subject: Trusted PTR_TO_BTF_ID arg support in global subprogs
version: 3
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=821094