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authorAlexei Starovoitov <ast@kernel.org>2019-11-14 10:57:17 -0800
committerDaniel Borkmann <daniel@iogearbox.net>2019-11-15 23:45:24 +0100
commit5b92a28aae4dd0f88778d540ecfdcdaec5a41723 (patch)
treecf375229c149eab426104777840718b0f1d2dfae /include/linux/btf.h
parent8c1b6e69dcc1e11bd24111e3734dd740aaf3fda1 (diff)
bpf: Support attaching tracing BPF program to other BPF programs
Allow FENTRY/FEXIT BPF programs to attach to other BPF programs of any type including their subprograms. This feature allows snooping on input and output packets in XDP, TC programs including their return values. In order to do that the verifier needs to track types not only of vmlinux, but types of other BPF programs as well. The verifier also needs to translate uapi/linux/bpf.h types used by networking programs into kernel internal BTF types used by FENTRY/FEXIT BPF programs. In some cases LLVM optimizations can remove arguments from BPF subprograms without adjusting BTF info that LLVM backend knows. When BTF info disagrees with actual types that the verifiers sees the BPF trampoline has to fallback to conservative and treat all arguments as u64. The FENTRY/FEXIT program can still attach to such subprograms, but it won't be able to recognize pointer types like 'struct sk_buff *' and it won't be able to pass them to bpf_skb_output() for dumping packets to user space. The FENTRY/FEXIT program would need to use bpf_probe_read_kernel() instead. The BPF_PROG_LOAD command is extended with attach_prog_fd field. When it's set to zero the attach_btf_id is one vmlinux BTF type ids. When attach_prog_fd points to previously loaded BPF program the attach_btf_id is BTF type id of main function or one of its subprograms. Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20191114185720.1641606-18-ast@kernel.org
Diffstat (limited to 'include/linux/btf.h')
-rw-r--r--include/linux/btf.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/btf.h b/include/linux/btf.h
index 9dee00859c5f..79d4abc2556a 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -88,6 +88,7 @@ static inline bool btf_type_is_func_proto(const struct btf_type *t)
const struct btf_type *btf_type_by_id(const struct btf *btf, u32 type_id);
const char *btf_name_by_offset(const struct btf *btf, u32 offset);
struct btf *btf_parse_vmlinux(void);
+struct btf *bpf_prog_get_target_btf(const struct bpf_prog *prog);
#else
static inline const struct btf_type *btf_type_by_id(const struct btf *btf,
u32 type_id)