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libbpf: Add bpf_program__set_insns function

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Adding bpf_program__set_insns that allows to set new instructions
for a BPF program.

This is a very advanced libbpf API and users need to know what
they are doing. This should be used from prog_prepare_load_fn
callback only.

We can have changed instructions after calling prog_prepare_load_fn
callback, reloading them.

One of the users of this new API will be perf's internal BPF prologue
generation.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220510074659.2557731-2-jolsa@kernel.org
This commit is contained in:
Jiri Olsa 2022-05-10 09:46:57 +02:00 committed by Daniel Borkmann
parent 5eefe17c7a
commit b63b3c490e
3 changed files with 41 additions and 0 deletions
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22
tools/lib/bpf/libbpf.c
View file

@ -6860,6 +6860,8 @@ static int bpf_object_load_prog_instance(struct bpf_object *obj, struct bpf_prog
prog->name, err);
return err;
}
insns = prog->insns;
insns_cnt = prog->insns_cnt;
}
if (obj->gen_loader) {
@ -8788,6 +8790,26 @@ size_t bpf_program__insn_cnt(const struct bpf_program *prog)
return prog->insns_cnt;
}
int bpf_program__set_insns(struct bpf_program *prog,
struct bpf_insn *new_insns, size_t new_insn_cnt)
{
struct bpf_insn *insns;
if (prog->obj->loaded)
return -EBUSY;
insns = libbpf_reallocarray(prog->insns, new_insn_cnt, sizeof(*insns));
if (!insns) {
pr_warn("prog '%s': failed to realloc prog code\n", prog->name);
return -ENOMEM;
}
memcpy(insns, new_insns, new_insn_cnt * sizeof(*insns));
prog->insns = insns;
prog->insns_cnt = new_insn_cnt;
return 0;
}
int bpf_program__set_prep(struct bpf_program *prog, int nr_instances,
bpf_program_prep_t prep)
{

18
tools/lib/bpf/libbpf.h
View file

@ -323,6 +323,24 @@ struct bpf_insn;
* different.
*/
LIBBPF_API const struct bpf_insn *bpf_program__insns(const struct bpf_program *prog);
/**
* @brief **bpf_program__set_insns()** can set BPF program's underlying
* BPF instructions.
*
* WARNING: This is a very advanced libbpf API and users need to know
* what they are doing. This should be used from prog_prepare_load_fn
* callback only.
*
* @param prog BPF program for which to return instructions
* @param new_insns a pointer to an array of BPF instructions
* @param new_insn_cnt number of `struct bpf_insn`'s that form
* specified BPF program
* @return 0, on success; negative error code, otherwise
*/
LIBBPF_API int bpf_program__set_insns(struct bpf_program *prog,
struct bpf_insn *new_insns, size_t new_insn_cnt);
/**
* @brief **bpf_program__insn_cnt()** returns number of `struct bpf_insn`'s
* that form specified BPF program.

1
tools/lib/bpf/libbpf.map
View file

@ -449,6 +449,7 @@ LIBBPF_0.8.0 {
bpf_program__attach_kprobe_multi_opts;
bpf_program__attach_trace_opts;
bpf_program__attach_usdt;
bpf_program__set_insns;
libbpf_register_prog_handler;
libbpf_unregister_prog_handler;
} LIBBPF_0.7.0;