libbpf: Add bpf_program__set_insns function
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
diff --git a/src/libbpf.c b/src/libbpf.c
index 0e74fae..4867a93 100644
--- a/src/libbpf.c
+++ b/src/libbpf.c
@@ -6860,6 +6860,8 @@
prog->name, err);
return err;
}
+ insns = prog->insns;
+ insns_cnt = prog->insns_cnt;
}
if (obj->gen_loader) {
@@ -8788,6 +8790,26 @@
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)
{
diff --git a/src/libbpf.h b/src/libbpf.h
index a1fb918..21984dc 100644
--- a/src/libbpf.h
+++ b/src/libbpf.h
@@ -323,6 +323,24 @@
* 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.
diff --git a/src/libbpf.map b/src/libbpf.map
index 80819e2..008da8d 100644
--- a/src/libbpf.map
+++ b/src/libbpf.map
@@ -449,6 +449,7 @@
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;
