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libbpf: Add support for dynamic program attach target

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Currently when you want to attach a trace program to a bpf program
the section name needs to match the tracepoint/function semantics.

However the addition of the bpf_program__set_attach_target() API
allows you to specify the tracepoint/function dynamically.

The call flow would look something like this:

  xdp_fd = bpf_prog_get_fd_by_id(id);
  trace_obj = bpf_object__open_file("func.o", NULL);
  prog = bpf_object__find_program_by_title(trace_obj,
                                           "fentry/myfunc");
  bpf_program__set_expected_attach_type(prog, BPF_TRACE_FENTRY);
  bpf_program__set_attach_target(prog, xdp_fd,
                                 "xdpfilt_blk_all");
  bpf_object__load(trace_obj)

Signed-off-by: Eelco Chaudron <echaudro@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/bpf/158220519486.127661.7964708960649051384.stgit@xdp-tutorial
This commit is contained in:
Eelco Chaudron 2020-02-20 13:26:35 +00:00 committed by Alexei Starovoitov
parent dd88aed92d
commit ff26ce5cd7
3 changed files with 36 additions and 4 deletions
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34
tools/lib/bpf/libbpf.c
View File

@ -4937,8 +4937,8 @@ int bpf_program__load(struct bpf_program *prog, char *license, __u32 kern_ver)
{
int err = 0, fd, i, btf_id;
if (prog->type == BPF_PROG_TYPE_TRACING ||
prog->type == BPF_PROG_TYPE_EXT) {
if ((prog->type == BPF_PROG_TYPE_TRACING ||
prog->type == BPF_PROG_TYPE_EXT) && !prog->attach_btf_id) {
btf_id = libbpf_find_attach_btf_id(prog);
if (btf_id <= 0)
return btf_id;
@ -6581,6 +6581,9 @@ static inline int __find_vmlinux_btf_id(struct btf *btf, const char *name,
else
err = btf__find_by_name_kind(btf, name, BTF_KIND_FUNC);
if (err <= 0)
pr_warn("%s is not found in vmlinux BTF\n", name);
return err;
}
@ -6653,8 +6656,6 @@ static int libbpf_find_attach_btf_id(struct bpf_program *prog)
err = __find_vmlinux_btf_id(prog->obj->btf_vmlinux,
name + section_defs[i].len,
attach_type);
if (err <= 0)
pr_warn("%s is not found in vmlinux BTF\n", name);
return err;
}
pr_warn("failed to identify btf_id based on ELF section name '%s'\n", name);
@ -8130,6 +8131,31 @@ void bpf_program__bpil_offs_to_addr(struct bpf_prog_info_linear *info_linear)
}
}
int bpf_program__set_attach_target(struct bpf_program *prog,
int attach_prog_fd,
const char *attach_func_name)
{
int btf_id;
if (!prog || attach_prog_fd < 0 || !attach_func_name)
return -EINVAL;
if (attach_prog_fd)
btf_id = libbpf_find_prog_btf_id(attach_func_name,
attach_prog_fd);
else
btf_id = __find_vmlinux_btf_id(prog->obj->btf_vmlinux,
attach_func_name,
prog->expected_attach_type);
if (btf_id < 0)
return btf_id;
prog->attach_btf_id = btf_id;
prog->attach_prog_fd = attach_prog_fd;
return 0;
}
int parse_cpu_mask_str(const char *s, bool **mask, int *mask_sz)
{
int err = 0, n, len, start, end = -1;

4
tools/lib/bpf/libbpf.h
View File

@ -334,6 +334,10 @@ LIBBPF_API void
bpf_program__set_expected_attach_type(struct bpf_program *prog,
enum bpf_attach_type type);
LIBBPF_API int
bpf_program__set_attach_target(struct bpf_program *prog, int attach_prog_fd,
const char *attach_func_name);
LIBBPF_API bool bpf_program__is_socket_filter(const struct bpf_program *prog);
LIBBPF_API bool bpf_program__is_tracepoint(const struct bpf_program *prog);
LIBBPF_API bool bpf_program__is_raw_tracepoint(const struct bpf_program *prog);

2
tools/lib/bpf/libbpf.map
View File

@ -237,4 +237,6 @@ LIBBPF_0.0.7 {
} LIBBPF_0.0.6;
LIBBPF_0.0.8 {
global:
bpf_program__set_attach_target;
} LIBBPF_0.0.7;