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Mon, 30 Mar 2026 05:57:00 -0700 (PDT) Received: from localhost ([2620:10d:c092:500::4:4b08]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4873881c195sm52375115e9.9.2026.03.30.05.57.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 30 Mar 2026 05:57:00 -0700 (PDT) From: Mykyta Yatsenko To: Kumar Kartikeya Dwivedi , bpf@vger.kernel.org Cc: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Martin KaFai Lau , Eduard Zingerman , Ihor Solodrai , kkd@meta.com, kernel-team@meta.com Subject: Re: [PATCH bpf-next v1 3/3] libbpf: Wire up verifier warning display logic In-Reply-To: <20260329212534.3270005-4-memxor@gmail.com> References: <20260329212534.3270005-1-memxor@gmail.com> <20260329212534.3270005-4-memxor@gmail.com> Date: Mon, 30 Mar 2026 13:56:59 +0100 Message-ID: <87ldf9h3vo.fsf@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain Kumar Kartikeya Dwivedi writes: > 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) nit: Not sure if this function name is a good choice: it does not take bpf object and does not load the program, I'd rather name it bpf_program_emit_verifier_stderr(). The implementation looks correct. Acked-by: Mykyta Yatsenko > +{ > + 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