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Eduard Zingerman says: ==================== The patch-set is consists of the following parts: - An update for libbpf's hashmap interface from void* -> void* to a polymorphic one, allowing to use both long and void* keys and values w/o additional casts. Interface functions are hidden behind auxiliary macro that add casts as necessary. This simplifies many use cases in libbpf as hashmaps there are mostly integer to integer and required awkward looking incantations like `(void *)(long)off` previously. Also includes updates for perf as it copies map implementation from libbpf. - A change to `lib/bpf/btf.c:btf__dedup` that adds a new pass named "Resolve unambiguous forward declaration". This pass builds a hashmap `name_off -> uniquely named struct or union` and uses it to replace FWD types by structs or unions. This is necessary for corner cases when FWD is not used as a part of some struct or union definition de-duplicated by `btf_dedup_struct_types`. The goal of the patch-set is to resolve forward declarations that don't take part in type graphs comparisons if declaration name is unambiguous. Example: CU #1: struct foo; // standalone forward declaration struct foo *some_global; CU #2: struct foo { int x; }; struct foo *another_global; Currently the de-duplicated BTF for this example looks as follows: [1] STRUCT 'foo' size=4 vlen=1 ... [2] INT 'int' size=4 ... [3] PTR '(anon)' type_id=1 [4] FWD 'foo' fwd_kind=struct [5] PTR '(anon)' type_id=4 The goal of this patch-set is to simplify it as follows: [1] STRUCT 'foo' size=4 vlen=1 'x' type_id=2 bits_offset=0 [2] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED [3] PTR '(anon)' type_id=1 For defconfig kernel with BTF enabled this removes 63 forward declarations. For allmodconfig kernel with BTF enabled this removes ~5K out of ~21K forward declarations in ko objects. This unlocks some additional de-duplication in ko objects, but impact is tiny: ~13K less BTF ids out of ~2M. Changelog: v3 -> v4 Changes suggested by Andrii: - hashmap interface rework to allow use of integer and pointer keys an values w/o casts as suggested in [1]. v2 -> v3 Changes suggested by Andrii: - perf's util/hashtable.{c,h} are synchronized with libbpf implementation, perf's source code updated accordingly; - changes to libbpf, bpf selftests and perf are combined in a single patch to simplify bisecting; - hashtable interface updated to be long -> long instead of uintptr_t -> uintptr_t; - btf_dedup_resolve_fwds updated to correctly use IS_ERR / PTR_ERR macro; - test cases for btf_dedup_resolve_fwds are updated for better clarity. v1 -> v2 - Style fixes in btf_dedup_resolve_fwd and btf_dedup_resolve_fwds as suggested by Alan. [v1] https://lore.kernel.org/bpf/20221102110905.2433622-1-eddyz87@gmail.com/ [v2] https://lore.kernel.org/bpf/20221103033430.2611623-1-eddyz87@gmail.com/ [v3] https://lore.kernel.org/bpf/20221106202910.4193104-1-eddyz87@gmail.com/ [1] https://lore.kernel.org/bpf/CAEf4BzZ8KFneEJxFAaNCCFPGqp20hSpS2aCj76uRk3-qZUH5xg@mail.gmail.com/ ==================== Signed-off-by: Andrii Nakryiko <andrii@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.