Crate btf_rs

Library for the BPF Type Format (BTF). The BPF Type Format is a metadata format encoding debugging information such as types, function prototypes, structure layouts, etc. and is often used, but not limited, to deal with eBPF programs.

The integration tests give good examples on how to use this library. We recommend reading the official BTF documentation as this library is offering a low-level API.

Parsing BTF

The main object this library offers is Btf, which represents a parsed BTF object. It offers helpers to resolve ids (u32), names (String) and types / chained types (Type).

Btf can be constructed using a BTF file or a split BTF one. BTF files hold self-contained information, while split BTF files are built upon a base BTF file and extend it. For example, in a standard Linux environment BTF files and split files can be found under /sys/kernel/btf, /sys/kernel/btf/vmlinux being the BTF file for the kernel and other files matching /sys/kernel/btf/<module-name> being BTF split files for its modules.

use btf_rs::Btf;

let base = Btf::from_file("/sys/kernel/btf/vmlinux").unwrap();

let ovs = Btf::from_split_file("/sys/kernel/btf/openvswitch", &base).unwrap();
let bbr = Btf::from_split_file("/sys/kernel/btf/tcp_bbr", &base).unwrap();

Btf-rs also supports constructing Btf using byte slices.

use std::fs;
use btf_rs::Btf;

let base = Btf::from_bytes(&fs::read("/sys/kernel/btf/vmlinux").unwrap()).unwrap();

let ovs = Btf::from_split_bytes(&fs::read("/sys/kernel/btf/openvswitch").unwrap(), &base)
          .unwrap();
let bbr = Btf::from_split_bytes(&fs::read("/sys/kernel/btf/bbr").unwrap(), &base).unwrap();

Resolving types

Types can be resolved using a Btf object. The following is an example of how a function can be inspected to retrieve information about its first parameter. Here the function kfree_skb_reason is taking a struct sk_buff * as its first argument.

use btf_rs::*;

let btf = Btf::from_file("/sys/kernel/btf/vmlinux").unwrap();

let func = match btf.resolve_types_by_name("kfree_skb_reason").unwrap().pop().unwrap() {
    Type::Func(func) => func,
    _ => panic!("Resolved type is not a function"),
};

let proto = match btf.resolve_chained_type(&func).unwrap() {
    Type::FuncProto(proto) => proto,
    _ => panic!("Resolved type is not a function proto"),
};

assert!(proto.parameters.len() > 1);

// The following prints "skb".
println!("{}", btf.resolve_name(&proto.parameters[0]).unwrap());

let ptr = match btf.resolve_chained_type(&proto.parameters[0]).unwrap() {
    Type::Ptr(ptr) => ptr,
    _ => panic!("Resolved type is not a pointer"),
};

let r#struct = match btf.resolve_chained_type(&ptr).unwrap() {
    Type::Struct(r#struct) => r#struct,
    _ => panic!("Resolved type is not a struct"),
};

// The following prints "sk_buff".
println!("{}", btf.resolve_name(&r#struct).unwrap());

Other information such as function scope and return value, structure size and members, etc. can be retrieved. For all those see the Type and its associated structures documentation.

Feature flags:

• test_runtime: Use the system’s runtime BTF files to perform extra integration tests.

Modules

btf

Structs

Array

Rust representation for BTF type BTF_KIND_ARRAY.

Btf

Main representation of a parsed BTF object. Provides helpers to resolve types and their associated names.

Datasec

Rust representation for BTF type BTF_KIND_DATASEC.

DeclTag

Rust representation for BTF type BTF_KIND_DECL_TAG.

Enum

Rust representation for BTF type BTF_KIND_ENUM.

Enum64

Rust representation for BTF type BTF_KIND_ENUM64.

Enum64Member

Represents an Enum64 member.

EnumMember

Represents an Enum member.

Float

Rust representation for BTF type BTF_KIND_FLOAT.

Func

Rust representation for BTF type BTF_KIND_FUNC.

FuncProto

Rust representation for BTF type BTF_KIND_FUNC_PROTO.

Fwd

Rust representation for BTF type BTF_KIND_FWD.

Int

Rust representation for BTF type BTF_KIND_INT.

Member

Represents a Struct member.

Parameter

Represents a FuncProto parameter.

Ptr

Rust representation for BTF type BTF_KIND_PTR.

Struct

Rust representation for BTF type BTF_KIND_STRUCT.

TypeIter

Iterator type returned by Btf::type_iter().

Typedef

Rust representation for BTF type BTF_KIND_TYPEDEF.

Var

Rust representation for BTF type BTF_KIND_VAR.

VarSecinfo

Represents a Datasec variable.

Volatile

Rust representation for BTF type BTF_KIND_VOLATILE.

Enums

Type

Rust representation of BTF types. Each type then contains its own specific data and provides helpers to access it.

Traits

BtfType

Type Aliases

Const

Rust representation for BTF type BTF_KIND_CONST.

Restrict

Rust representation for BTF type BTF_KIND_RESTRICT.

TypeTag

Rust representation for BTF type BTF_KIND_TYPE_TAG.

Union

Rust representation for BTF type BTF_KIND_UNION.