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[2001:1ae9:1c2:4c00:726e:c10f:8833:ff22]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a8d25a258a3sm868657566b.89.2024.09.13.06.48.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 13 Sep 2024 06:48:49 -0700 (PDT) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Fri, 13 Sep 2024 15:48:46 +0200 To: Tao Chen Cc: Andrii Nakryiko , Eduard Zingerman , Daniel Borkmann , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , bpf@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH bpf-next] libbpf: Fix expected_attach_type set when kernel not support Message-ID: References: <20240913121627.153898-1-chen.dylane@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240913121627.153898-1-chen.dylane@gmail.com> On Fri, Sep 13, 2024 at 08:16:27PM +0800, Tao Chen wrote: > The commit "5902da6d8a52" set expected_attach_type again with > filed of bpf_program after libpf_prepare_prog_load, which makes > expected_attach_type = 0 no sense when kenrel not support the > attach_type feature, so fix it. > > Fixes: 5902da6d8a52 ("libbpf: Add uprobe multi link support to bpf_program__attach_usdt") > Signed-off-by: Tao Chen > --- > tools/lib/bpf/libbpf.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c > index 219facd0e66e..9035edf763a3 100644 > --- a/tools/lib/bpf/libbpf.c > +++ b/tools/lib/bpf/libbpf.c > @@ -7343,7 +7343,7 @@ static int libbpf_prepare_prog_load(struct bpf_program *prog, > > /* old kernels might not support specifying expected_attach_type */ > if ((def & SEC_EXP_ATTACH_OPT) && !kernel_supports(prog->obj, FEAT_EXP_ATTACH_TYPE)) > - opts->expected_attach_type = 0; > + prog->expected_attach_type = 0; > > if (def & SEC_SLEEPABLE) > opts->prog_flags |= BPF_F_SLEEPABLE; > -- > 2.25.1 > good catch! thanks I can't remember why it was needed, perhaps we should go back to where it was before? I'm guessing prog->expected_attach_type might not get updated properly and that might cause issues, not sure thanks, jirka --- diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 219facd0e66e..df2244397ba1 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -7353,7 +7353,7 @@ static int libbpf_prepare_prog_load(struct bpf_program *prog, /* special check for usdt to use uprobe_multi link */ if ((def & SEC_USDT) && kernel_supports(prog->obj, FEAT_UPROBE_MULTI_LINK)) - prog->expected_attach_type = BPF_TRACE_UPROBE_MULTI; + opts->expected_attach_type = BPF_TRACE_UPROBE_MULTI; if ((def & SEC_ATTACH_BTF) && !prog->attach_btf_id) { int btf_obj_fd = 0, btf_type_id = 0, err; @@ -7443,6 +7443,7 @@ static int bpf_object_load_prog(struct bpf_object *obj, struct bpf_program *prog load_attr.attach_btf_id = prog->attach_btf_id; load_attr.kern_version = kern_version; load_attr.prog_ifindex = prog->prog_ifindex; + load_attr.expected_attach_type = prog->expected_attach_type; /* specify func_info/line_info only if kernel supports them */ if (obj->btf && btf__fd(obj->btf) >= 0 && kernel_supports(obj, FEAT_BTF_FUNC)) { @@ -7474,9 +7475,6 @@ static int bpf_object_load_prog(struct bpf_object *obj, struct bpf_program *prog insns_cnt = prog->insns_cnt; } - /* allow prog_prepare_load_fn to change expected_attach_type */ - load_attr.expected_attach_type = prog->expected_attach_type; - if (obj->gen_loader) { bpf_gen__prog_load(obj->gen_loader, prog->type, prog->name, license, insns, insns_cnt, &load_attr,