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Previously, `bpf_object__load_vmlinux_btf()` completely bypassed loading the kernel vmlinux BTF (`obj->btf_vmlinux`) if `gen_loader` was active. However, BPF `struct_ops` maps (such as `sched_ext_ops` maps) require resolving the kernel-side struct type IDs and member sizes at compile/skeleton generation time. Without loading `btf_vmlinux`, libbpf cannot query the kernel BTF types, causing light skeleton generation for `struct_ops` to fail or omit crucial type information. Fix this by modifying the check to load `btf_vmlinux` even in `gen_loader` mode if the BPF object actually requires kernel vmlinux BTF (e.g. contains `struct_ops` maps). Signed-off-by: Siddharth Nayyar --- tools/lib/bpf/libbpf.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 3a80a018fc7d..cb1b7ea884a7 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -3590,7 +3590,10 @@ static int bpf_object__load_vmlinux_btf(struct bpf_o= bject *obj, bool force) int err; =20 /* btf_vmlinux could be loaded earlier */ - if (obj->btf_vmlinux || obj->gen_loader) + if (obj->btf_vmlinux) + return 0; + + if (obj->gen_loader && !obj_needs_vmlinux_btf(obj)) return 0; =20 if (!force && !obj_needs_vmlinux_btf(obj)) --=20 2.54.0.746.g67dd491aae-goog From nobody Mon Jun 8 21:47:06 2026 Received: from mail-wr1-f74.google.com (mail-wr1-f74.google.com [209.85.221.74]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4E4EE3F8712 for ; Tue, 26 May 2026 12:13:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; 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Tue, 26 May 2026 05:13:03 -0700 (PDT) Date: Tue, 26 May 2026 12:12:57 +0000 In-Reply-To: <20260526-libbpf-load-vmlinux-btf-in-gen_loader-mode-v2-0-6750f5859bc6@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260526-libbpf-load-vmlinux-btf-in-gen_loader-mode-v2-0-6750f5859bc6@google.com> X-Mailer: b4 0.14.3 Message-ID: <20260526-libbpf-load-vmlinux-btf-in-gen_loader-mode-v2-2-6750f5859bc6@google.com> Subject: [PATCH v2 2/3] libbpf: zero out btf_key_type_id for STRUCT_OPS maps From: Siddharth Nayyar To: Andrii Nakryiko , Eduard Zingerman , Alexei Starovoitov , Daniel Borkmann , Martin KaFai Lau , Kumar Kartikeya Dwivedi , Song Liu , Yonghong Song , Jiri Olsa Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org, gprocida@google.com, maennich@google.com, Siddharth Nayyar Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable For BPF `STRUCT_OPS` maps (such as `sched_ext_ops` maps), the kernel BPF subsystem enforces strict map-creation safety validations inside `map_create()`. That is, if `btf_vmlinux_value_type_id` is set, the kernel forbids passing any userspace `btf_key_type_id` or `btf_value_type_id` (they must both be `0`). However, inside libbpf's map-creation options initialization (`bpf_object__create_map()`), libbpf zeroed out `create_attr.btf_value_type_id` but does not zero out `create_attr.btf_key_type_id`. Fix this by explicitly zeroing out `create_attr.btf_key_type_id`. Signed-off-by: Siddharth Nayyar --- tools/lib/bpf/libbpf.c | 1 + 1 file changed, 1 insertion(+) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index cb1b7ea884a7..9969de42da41 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -5439,6 +5439,7 @@ static int bpf_object__create_map(struct bpf_object *= obj, struct bpf_map *map, b map->btf_value_type_id =3D 0; break; case BPF_MAP_TYPE_STRUCT_OPS: + create_attr.btf_key_type_id =3D 0; create_attr.btf_value_type_id =3D 0; break; default: --=20 2.54.0.746.g67dd491aae-goog From nobody Mon Jun 8 21:47:06 2026 Received: from mail-wr1-f73.google.com (mail-wr1-f73.google.com [209.85.221.73]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4C4783F8EDB for ; Tue, 26 May 2026 12:13:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.221.73 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; 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Tue, 26 May 2026 05:13:04 -0700 (PDT) Date: Tue, 26 May 2026 12:12:58 +0000 In-Reply-To: <20260526-libbpf-load-vmlinux-btf-in-gen_loader-mode-v2-0-6750f5859bc6@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260526-libbpf-load-vmlinux-btf-in-gen_loader-mode-v2-0-6750f5859bc6@google.com> X-Mailer: b4 0.14.3 Message-ID: <20260526-libbpf-load-vmlinux-btf-in-gen_loader-mode-v2-3-6750f5859bc6@google.com> Subject: [PATCH v2 3/3] libbpf: plumb btf_vmlinux_value_type_id and btf_fd in gen_loader From: Siddharth Nayyar To: Andrii Nakryiko , Eduard Zingerman , Alexei Starovoitov , Daniel Borkmann , Martin KaFai Lau , Kumar Kartikeya Dwivedi , Song Liu , Yonghong Song , Jiri Olsa Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org, gprocida@google.com, maennich@google.com, Siddharth Nayyar Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable BPF `STRUCT_OPS` maps (such as `sched_ext_ops` maps) require resolving and plumbing the kernel-side structure value type ID (`btf_vmlinux_value_type_id`) into the BPF map creation system call attributes. Additionally, when `btf_vmlinux_value_type_id` is supplied, the kernel requires a valid userspace BTF file descriptor (`btf_fd`) to be supplied to verify types. Previously, the `gen_loader` map creation generator (`bpf_gen__map_create()`) completely omitted plumbing `btf_vmlinux_value_type_id` because `attr_size` was calculated only up to `map_extra` (which resides before `btf_vmlinux_value_type_id` in `union bpf_attr`). Furthermore, `gen_loader.c` only copied the loaded `btf_fd` from the stack to the attributes blob if `btf_value_type_id` was non-zero. Because `STRUCT_OPS` maps explicitly zero out `btf_value_type_id`, the loader program skipped copying `btf_fd`, leaving it as `0` (standard input), which caused the kernel's `btf_get_by_fd(0)` check to fail. Fix this by: 1. Expanding `attr_size` inside `bpf_gen__map_create()` to include `btf_vmlinux_value_type_id` and copying it from the options. 2. Modifying the `btf_fd` copying condition to populate `btf_fd` if either `btf_value_type_id` OR `btf_vmlinux_value_type_id` is set. Signed-off-by: Siddharth Nayyar --- tools/lib/bpf/gen_loader.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/tools/lib/bpf/gen_loader.c b/tools/lib/bpf/gen_loader.c index cd5c2543f54d..27b0353d1082 100644 --- a/tools/lib/bpf/gen_loader.c +++ b/tools/lib/bpf/gen_loader.c @@ -507,7 +507,7 @@ void bpf_gen__map_create(struct bpf_gen *gen, __u32 key_size, __u32 value_size, __u32 max_entries, struct bpf_map_create_opts *map_attr, int map_idx) { - int attr_size =3D offsetofend(union bpf_attr, map_extra); + int attr_size =3D offsetofend(union bpf_attr, btf_vmlinux_value_type_id); bool close_inner_map_fd =3D false; int map_create_attr, idx; union bpf_attr attr; @@ -525,13 +525,14 @@ void bpf_gen__map_create(struct bpf_gen *gen, attr.max_entries =3D tgt_endian(max_entries); attr.btf_key_type_id =3D tgt_endian(map_attr->btf_key_type_id); attr.btf_value_type_id =3D tgt_endian(map_attr->btf_value_type_id); + attr.btf_vmlinux_value_type_id =3D tgt_endian(map_attr->btf_vmlinux_value= _type_id); =20 map_create_attr =3D add_data(gen, &attr, attr_size); pr_debug("gen: map_create: %s idx %d type %d value_type_id %d, attr: off = %d size %d\n", map_name, map_idx, map_type, map_attr->btf_value_type_id, map_create_attr, attr_size); =20 - if (map_attr->btf_value_type_id) + if (map_attr->btf_value_type_id || map_attr->btf_vmlinux_value_type_id) /* populate union bpf_attr with btf_fd saved in the stack earlier */ move_stack2blob(gen, attr_field(map_create_attr, btf_fd), 4, stack_off(btf_fd)); --=20 2.54.0.746.g67dd491aae-goog