kernel.git/tools/lib/bpf/btf.h, branch linux-5.4.y

libbpf: add .BTF.ext offset relocation section loading

2019-08-07T21:43:49Z

Add support for BPF CO-RE offset relocations. Add section/record iteration macros for .BTF.ext. These macro are useful for iterating over each .BTF.ext record, either for dumping out contents or later for BPF CO-RE relocation handling. To enable other parts of libbpf to work with .BTF.ext contents, moved a bunch of type definitions into libbpf_internal.h. Signed-off-by: Andrii Nakryiko Acked-by: Song Liu Signed-off-by: Alexei Starovoitov

libbpf: add helpers for working with BTF types

2019-08-07T21:43:49Z

Add lots of frequently used helpers that simplify working with BTF types. Signed-off-by: Andrii Nakryiko Signed-off-by: Alexei Starovoitov

libbpf: allow specifying map definitions using BTF

2019-06-17T22:10:41Z

This patch adds support for a new way to define BPF maps. It relies on BTF to describe mandatory and optional attributes of a map, as well as captures type information of key and value naturally. This eliminates the need for BPF_ANNOTATE_KV_PAIR hack and ensures key/value sizes are always in sync with the key/value type. Relying on BTF, this approach allows for both forward and backward compatibility w.r.t. extending supported map definition features. By default, any unrecognized attributes are treated as an error, but it's possible relax this using MAPS_RELAX_COMPAT flag. New attributes, added in the future will need to be optional. The outline of the new map definition (short, BTF-defined maps) is as follows: 1. All the maps should be defined in .maps ELF section. It's possible to have both "legacy" map definitions in `maps` sections and BTF-defined maps in .maps sections. Everything will still work transparently. 2. The map declaration and initialization is done through a global/static variable of a struct type with few mandatory and extra optional fields: - type field is mandatory and specified type of BPF map; - key/value fields are mandatory and capture key/value type/size information; - max_entries attribute is optional; if max_entries is not specified or initialized, it has to be provided in runtime through libbpf API before loading bpf_object; - map_flags is optional and if not defined, will be assumed to be 0. 3. Key/value fields should be **a pointer** to a type describing key/value. The pointee type is assumed (and will be recorded as such and used for size determination) to be a type describing key/value of the map. This is done to save excessive amounts of space allocated in corresponding ELF sections for key/value of big size. 4. As some maps disallow having BTF type ID associated with key/value, it's possible to specify key/value size explicitly without associating BTF type ID with it. Use key_size and value_size fields to do that (see example below). Here's an example of simple ARRAY map defintion: struct my_value { int x, y, z; }; struct { int type; int max_entries; int *key; struct my_value *value; } btf_map SEC(".maps") = { .type = BPF_MAP_TYPE_ARRAY, .max_entries = 16, }; This will define BPF ARRAY map 'btf_map' with 16 elements. The key will be of type int and thus key size will be 4 bytes. The value is struct my_value of size 12 bytes. This map can be used from C code exactly the same as with existing maps defined through struct bpf_map_def. Here's an example of STACKMAP definition (which currently disallows BTF type IDs for key/value): struct { __u32 type; __u32 max_entries; __u32 map_flags; __u32 key_size; __u32 value_size; } stackmap SEC(".maps") = { .type = BPF_MAP_TYPE_STACK_TRACE, .max_entries = 128, .map_flags = BPF_F_STACK_BUILD_ID, .key_size = sizeof(__u32), .value_size = PERF_MAX_STACK_DEPTH * sizeof(struct bpf_stack_build_id), }; This approach is naturally extended to support map-in-map, by making a value field to be another struct that describes inner map. This feature is not implemented yet. It's also possible to incrementally add features like pinning with full backwards and forward compatibility. Support for static initialization of BPF_MAP_TYPE_PROG_ARRAY using pointers to BPF programs is also on the roadmap. Signed-off-by: Andrii Nakryiko Acked-by: Song Liu Signed-off-by: Daniel Borkmann

libbpf: add btf_dump API for BTF-to-C conversion

2019-05-24T21:05:58Z

BTF contains enough type information to allow generating valid compilable C header w/ correct layout of structs/unions and all the typedef/enum definitions. This patch adds a new "object" - btf_dump to facilitate dumping BTF as valid C. btf_dump__dump_type() is the main API which takes care of dumping out (through user-provided printf-like callback function) C definitions for given type ID and it's required dependencies. This allows for not just dumping out entirety of BTF types, but also selective filtering based on user-provided criterias w/ minimal set of dependent types. Signed-off-by: Andrii Nakryiko Signed-off-by: Alexei Starovoitov

libbpf: add btf__parse_elf API to load .BTF and .BTF.ext

2019-05-24T21:05:57Z

Loading BTF and BTF.ext from ELF file is a common need. Instead of requiring every user to re-implement it, let's provide this API from libbpf itself. It's mostly copy/paste from `bpftool btf dump` implementation, which will be switched to libbpf's version in next patch. btf__parse_elf allows to load BTF and optionally BTF.ext. This is also useful for tests that need to load/work with BTF, loaded from test ELF files. Signed-off-by: Andrii Nakryiko Signed-off-by: Alexei Starovoitov

bpf, libbpf: add support for BTF Var and DataSec

2019-04-10T00:05:47Z

This adds libbpf support for BTF Var and DataSec kinds. Main point here is that libbpf needs to do some preparatory work before the whole BTF object can be loaded into the kernel, that is, fixing up of DataSec size taken from the ELF section size and non-static variable offset which needs to be taken from the ELF's string section. Upstream LLVM doesn't fix these up since at time of BTF emission it is too early in the compilation process thus this information isn't available yet, hence loader needs to take care of it. Note, deduplication handling has not been in the scope of this work and needs to be addressed in a future commit. Signed-off-by: Daniel Borkmann Link: https://reviews.llvm.org/D59441 Acked-by: Martin KaFai Lau Signed-off-by: Alexei Starovoitov

btf: allow to customize dedup hash table size

2019-03-01T00:31:47Z

Default size of dedup table (16k) is good enough for most binaries, even typical vmlinux images. But there are cases of binaries with huge amount of BTF types (e.g., allyesconfig variants of kernel), which benefit from having bigger dedup table size to lower amount of unnecessary hash collisions. Tools like pahole, thus, can tune this parameter to reach optimal performance. This change also serves double purpose of allowing tests to force hash collisions to test some corner cases, used in follow up patch. Signed-off-by: Andrii Nakryiko Acked-by: Yonghong Song Signed-off-by: Daniel Borkmann

libbpf: fix formatting for btf_ext__get_raw_data

2019-03-01T00:31:47Z

Fix invalid formatting of pointer arg. Signed-off-by: Andrii Nakryiko Acked-by: Song Liu Signed-off-by: Daniel Borkmann

tools/bpf: remove btf__get_strings() superseded by raw data API

2019-02-08T20:04:13Z

Now that we have btf__get_raw_data() it's trivial for tests to iterate over all strings for testing purposes, which eliminates the need for btf__get_strings() API. Signed-off-by: Andrii Nakryiko Acked-by: Yonghong Song Signed-off-by: Alexei Starovoitov

btf: expose API to work with raw btf_ext data

2019-02-08T20:04:13Z

This patch changes struct btf_ext to retain original data in sequential block of memory, which makes it possible to expose btf_ext__get_raw_data() interface similar to btf__get_raw_data(), allowing users of libbpf to get access to raw representation of .BTF.ext section. Signed-off-by: Andrii Nakryiko Acked-by: Yonghong Song Signed-off-by: Alexei Starovoitov