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a64bfe6186
Add ability to pass a pointer to dynptr into global functions. This allows to have global subprogs that accept and work with generic dynptrs that are created by caller. Dynptr argument is detected based on the name of a struct type, if it's "bpf_dynptr", it's assumed to be a proper dynptr pointer. Both actual struct and forward struct declaration types are supported. This is conceptually exactly the same semantics as bpf_user_ringbuf_drain()'s use of dynptr to pass a variable-sized pointer to ringbuf record. So we heavily rely on CONST_PTR_TO_DYNPTR bits of already existing logic in the verifier. During global subprog validation, we mark such CONST_PTR_TO_DYNPTR as having LOCAL type, as that's the most unassuming type of dynptr and it doesn't have any special helpers that can try to free or acquire extra references (unlike skb, xdp, or ringbuf dynptr). So that seems like a safe "choice" to make from correctness standpoint. It's still possible to pass any type of dynptr to such subprog, though, because generic dynptr helpers, like getting data/slice pointers, read/write memory copying routines, dynptr adjustment and getter routines all work correctly with any type of dynptr. Acked-by: Eduard Zingerman <eddyz87@gmail.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20231215011334.2307144-8-andrii@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.