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Kumar Kartikeya Dwivedi says: ==================== This series introduces user defined BPF objects of a type in program BTF. This allows BPF programs to allocate their own objects, build their own object hierarchies, and use the basic building blocks provided by BPF runtime to build their own data structures flexibly. Then, we introduce the support for single ownership BPF linked lists, which can be put inside BPF maps, or allocated objects, and hold such allocated objects as elements. It works as an instrusive collection, which is done to allow making allocated objects part of multiple data structures at the same time in the future. The eventual goal of this and future patches is to allow one to do some limited form of kernel style programming in BPF C, and allow programmers to build their own complex data structures flexibly out of basic building blocks. The key difference will be that such programs are verified to be safe, preserve runtime integrity of the system, and are proven to be bug free as far as the invariants of BPF specific APIs are concerned. One immediate use case that will be using the entire infrastructure this series is introducing will be managing percpu NMI safe linked lists inside BPF programs. The other use case this will serve in the near future will be linking kernel structures like XDP frame and sk_buff directly into user data structures (rbtree, pifomap, etc.) for packet queueing. This will follow single ownership concept included in this series. The user has complete control of the internal locking, and hence also the batching of operations for each critical section. The features are: - Allocated objects. - bpf_obj_new, bpf_obj_drop to allocate and free them. - Single ownership BPF linked lists. - Support for them in BPF maps. - Support for them in allocated objects. - Global spin locks. - Spin locks inside allocated objects. Some other notable things: - Completely static verification of locking. - Kfunc argument handling has been completely reworked. - Argument rewriting support for kfuncs. - A new bpf_experimental.h header as a dumping ground for these APIs. Any functionality exposed in this series is NOT part of UAPI. It is only available through use of kfuncs, and structs that can be added to map value may also change their size or name in the future. Hence, every feature in this series must be considered experimental. Follow-ups: ----------- * Support for kptrs (local and kernel) in local storage and percpu maps + kptr tests * Fixes for helper access checks rebasing on top of this series Next steps: ----------- * NMI safe percpu single ownership linked lists (using local_t protection). * Lockless linked lists. * Allow RCU protected BPF allocated objects. This then allows RCU protected list lookups, since spinlock protection for readers does not scale. * Introduce bpf_refcount for local kptrs, shared ownership. * Introduce shared ownership linked lists. * Documentation. Changelog: ---------- v9 -> v10 v9: https://lore.kernel.org/bpf/20221117225510.1676785-1-memxor@gmail.com * Deduplicate code to find btf_record of reg (Alexei) * Add linked_list test to DENYLIST.aarch64 (Alexei) * Disable some linked list tests for now so that they compile with clang nightly (Alexei) v8 -> v9 v8: https://lore.kernel.org/bpf/20221117162430.1213770-1-memxor@gmail.com * Fix up commit log of patch 2, Simplify patch 3 * Explain the implicit requirement of bpf_list_head requiring map BTF to match in btf_record_equal in a separate patch. v7 -> v8 v7: https://lore.kernel.org/bpf/20221114191547.1694267-1-memxor@gmail.com * Fix early return in map_check_btf (Dan Carpenter) * Fix two memory leak bugs in local storage maps, outer maps * Address comments from Alexei and Dave * More local kptr -> allocated object renaming * Use krealloc with NULL instead kmalloc + krealloc * Drop WARN_ON_ONCE for field_offs parsing * Combine kfunc add + remove patches into one * Drop STRONG suffix from KF_ARG_PTR_TO_KPTR * Rename is_kfunc_arg_ret_buf_size to is_kfunc_arg_scalar_with_name * Remove redundant check for reg->type and arg type in it * Drop void * ret type check * Remove code duplication in checks for NULL pointer with offset != 0 * Fix two bpf_list_node typos * Improve log message for bpf_list_head operations * Improve comments for active_lock struct * Improve comments for Implementation details of process_spin_lock * Add Dave's acks v6 -> v7 v6: https://lore.kernel.org/bpf/20221111193224.876706-1-memxor@gmail.com * Fix uninitialized variable warning (Dan Carpenter, Kernel Test Robot) * One more local_kptr renaming v5 -> v6 v5: https://lore.kernel.org/bpf/20221107230950.7117-1-memxor@gmail.com * Replace (i && !off) check with next_off, include test (Andrii) * Drop local kptrs naming (Andrii, Alexei) * Drop reg->precise == EXACT patch (Andrii) * Add comment about ptr member of struct active_lock (Andrii) * Use btf__new_empty + btf__add_xxx APIs (Andrii) * Address other misc nits from Andrii v4 -> v5 v4: https://lore.kernel.org/bpf/20221103191013.1236066-1-memxor@gmail.com * Add a lot more selftests (failure, success, runtime, BTF) * Make sure series is bisect friendly * Move list draining out of spin lock * This exposed an issue where bpf_mem_free can now be called in map_free path without migrate_disable, also fixed that. * Rename MEM_ALLOC -> MEM_RINGBUF, MEM_TYPE_LOCAL -> MEM_ALLOC (Alexei) * Group lock identity into a struct active_lock { ptr, id } (Dave) * Split set_release_on_unlock logic into separate patch (Alexei) v3 -> v4 v3: https://lore.kernel.org/bpf/20221102202658.963008-1-memxor@gmail.com * Fix compiler error for !CONFIG_BPF_SYSCALL (Kernel Test Robot) * Fix error due to BUILD_BUG_ON on 32-bit platforms (Kernel Test Robot) v2 -> v3 v2: https://lore.kernel.org/bpf/20221013062303.896469-1-memxor@gmail.com * Add ack from Dave for patch 5 * Rename btf_type_fields -> btf_record, btf_type_fields_off -> btf_field_offs, rename functions similarly (Alexei) * Remove 'kind' component from contains declaration tag (Alexei) * Move bpf_list_head, bpf_list_node definitions to UAPI bpf.h (Alexei) * Add note in commit log about modifying btf_struct_access API (Dave) * Downgrade WARN_ON_ONCE to verbose(env, "...") and return -EFAULT (Dave) * Add type_is_local_kptr wrapper to avoid noisy checks (Dave) * Remove unused flags parameter from bpf_kptr_new (Alexei) * Rename bpf_kptr_new -> bpf_obj_new, bpf_kptr_drop -> bpf_obj_drop (Alexei) * Reword comment in ref_obj_id_set_release_on_unlock (Dave) * Fix return type of ref_obj_id_set_release_on_unlock (Dave) * Introduce is_bpf_list_api_kfunc to dedup checks (Dave) * Disallow BPF_WRITE to untrusted local kptrs * Add details about soundness of check_reg_allocation_locked logic * List untrusted local kptrs for PROBE_MEM handling v1 -> v2 v1: https://lore.kernel.org/bpf/20221011012240.3149-1-memxor@gmail.com * Rebase on bpf-next to resolve merge conflict in DENYLIST.s390x * Fix a couple of mental lapses in bpf_list_head_free RFC v1 -> v1 RFC v1: https://lore.kernel.org/bpf/20220904204145.3089-1-memxor@gmail.com * Mostly a complete rewrite of BTF parsing, refactor existing code (Kartikeya) * Rebase kfunc rewrite for bpf-next, add support for more changes * Cache type metadata in BTF to avoid recomputation inside verifier (Kartikeya) * Remove __kernel tag, make things similar to map values, reserve bpf_ prefix * bpf_kptr_new, bpf_kptr_drop * Rename precision state enum values (Alexei) * Drop explicit constructor/destructor support (Alexei) * Rewrite code for constructing/destructing objects and offload to runtime * Minimize duplication in bpf_map_value_off_desc handling (Alexei) * Expose global memory allocator (Alexei) * Address other nits from Alexei * Split out local kptrs in maps, more kptrs in maps support into a follow up Links: ------ * Dave's BPF RB-Tree RFC series v1 (Discussion thread) https://lore.kernel.org/bpf/20220722183438.3319790-1-davemarchevsky@fb.com v2 (With support for static locks) https://lore.kernel.org/bpf/20220830172759.4069786-1-davemarchevsky@fb.com * BPF Linked Lists Discussion https://lore.kernel.org/bpf/CAP01T74U30+yeBHEgmgzTJ-XYxZ0zj71kqCDJtTH9YQNfTK+Xw@mail.gmail.com * BPF Memory Allocator from Alexei https://lore.kernel.org/bpf/20220902211058.60789-1-alexei.starovoitov@gmail.com * BPF Memory Allocator UAPI Discussion https://lore.kernel.org/bpf/d3f76b27f4e55ec9e400ae8dcaecbb702a4932e8.camel@fb.com ==================== Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
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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.