Wire up the flushing of all accumulated messages in a program's stderr stream after verification is complete. An example is shown below of a warning printed now about usage of deprecated kfuncs. $ ./test_progs -t kfunc_implicit_args/test_kfunc_implicit_arg_legacy_impl -v ... libbpf: prog 'test_kfunc_implicit_arg_legacy_impl': VERIFIER WARNINGS: WARNING: kfunc_implicit_args.c:40 calls deprecated kfunc bpf_kfunc_implicit_arg_legacy_impl(), which will be removed. WARNING: Switch to kfunc bpf_kfunc_implicit_arg_legacy() instead. WARNING: For older kernels, choose the kfunc using bpf_ksym_exists(bpf_kfunc_implicit_arg_legacy). ... Note that test_progs overrides the default logging function, hence -v is necessary. By default these messages would be printed for the user. Signed-off-by: Kumar Kartikeya Dwivedi --- tools/lib/bpf/libbpf.c | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 9ea41f40dc82..f308bacd083f 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -7826,6 +7826,27 @@ static int libbpf_prepare_prog_load(struct bpf_program *prog, static void fixup_verifier_log(struct bpf_program *prog, char *buf, size_t buf_sz); +static void bpf_object_load_prog_emit_stderr(struct bpf_program *prog, int prog_fd) +{ + char chunk[256]; + bool emitted = false; + int ret; + + while ((ret = bpf_prog_stream_read(prog_fd, BPF_STREAM_STDERR, chunk, + sizeof(chunk), NULL)) > 0) { + if (!emitted) { + pr_warn("prog '%s': VERIFIER WARNINGS:\n", prog->name); + emitted = true; + } + libbpf_print(LIBBPF_WARN, "%.*s", ret, chunk); + } + + if (ret < 0) { + pr_debug("prog '%s': failed to read BPF stderr stream: %s\n", + prog->name, errstr(ret)); + } +} + static int bpf_object_load_prog(struct bpf_object *obj, struct bpf_program *prog, struct bpf_insn *insns, int insns_cnt, const char *license, __u32 kern_version, int *prog_fd) @@ -7950,6 +7971,8 @@ static int bpf_object_load_prog(struct bpf_object *obj, struct bpf_program *prog prog->name, log_buf); } + bpf_object_load_prog_emit_stderr(prog, ret); + if (obj->has_rodata && kernel_supports(obj, FEAT_PROG_BIND_MAP)) { struct bpf_map *map; int i; -- 2.52.0