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Mon, 02 Nov 2026 12:14:03 -0800 (PST) Received: from mtardy-friendly-lvh-runner.europe-west1-c.c.cilium-dev.internal ([2600:1900:4010:1a8::]) by smtp.googlemail.com with ESMTPSA id ffacd0b85a97d-48e71b8c6e9sm21471805f8f.43.2026.11.02.12.14.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 02 Nov 2026 12:14:03 -0800 (PST) From: Mahe Tardy To: bpf@vger.kernel.org Cc: Quentin Monnet , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , Martin KaFai Lau , Song Liu , Yonghong Song , Jiri Olsa , Emil Tsalapatis , Ihor Solodrai , Shuah Khan , Mahe Tardy , Tianyi Chen , Gyutae Bae , Hui Su , Josef Bacik , linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: [PATCH bpf-next v3 2/5] libbpf: Track generated loader link FDs Date: Mon, 2 Nov 2026 20:13:53 +0000 Message-ID: <20261102201356.5798-3-mahe.tardy@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20261102201356.5798-1-mahe.tardy@gmail.com> References: <20261102201356.5798-1-mahe.tardy@gmail.com> X-Mailing-List: bpf@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Introduce gen_attach field to emit program attachment instructions in generated SYSCALL loaders. Generate failure cleanup that closes any created links before releasing programs and maps reusing emit_sys_close_blob(). Store the link fds in the data buffer similarly to map fds. Append bpf_link_desc outputs after the program descriptors and copy the link FDs to the loader context on success. Signed-off-by: Mahe Tardy --- tools/lib/bpf/bpf_gen_internal.h | 2 ++ tools/lib/bpf/gen_loader.c | 17 ++++++++++++++++- tools/lib/bpf/libbpf.h | 3 ++- tools/lib/bpf/skel_internal.h | 4 ++++ 4 files changed, 24 insertions(+), 2 deletions(-) diff --git a/tools/lib/bpf/bpf_gen_internal.h b/tools/lib/bpf/bpf_gen_internal.h index 206adf28793d..b601269abe45 100644 --- a/tools/lib/bpf/bpf_gen_internal.h +++ b/tools/lib/bpf/bpf_gen_internal.h @@ -39,6 +39,8 @@ struct bpf_gen { ssize_t cleanup_label; __u32 nr_progs; __u32 nr_maps; + int link_fds; + __u32 nr_link_slots; int log_level; int error; struct ksym_relo_desc *relos; diff --git a/tools/lib/bpf/gen_loader.c b/tools/lib/bpf/gen_loader.c index 555d4757a898..7f41b5a517fe 100644 --- a/tools/lib/bpf/gen_loader.c +++ b/tools/lib/bpf/gen_loader.c @@ -122,6 +122,10 @@ void bpf_gen__init(struct bpf_gen *gen, int log_level, int nr_progs, int nr_maps gen->log_level = log_level; gen->nr_obj_maps = nr_maps; gen->max_func_ptr_maps = max_func_ptr_maps; + if (OPTS_GET(gen->opts, gen_attach, false)) { + gen->link_fds = add_data(gen, NULL, nr_progs * sizeof(int)); + gen->nr_link_slots = nr_progs; + } if (nr_maps + max_func_ptr_maps > MAX_USED_MAPS) { pr_warn("Total maps exceeds %d\n", MAX_USED_MAPS); gen->error = -E2BIG; @@ -150,10 +154,14 @@ void bpf_gen__init(struct bpf_gen *gen, int log_level, int nr_progs, int nr_maps /* 6 insns for emit_sys_close_blob, * 6 insns for debug_regs in emit_sys_close_blob */ - nr_maps * (6 + (gen->log_level ? 6 : 0)))); + (nr_maps + gen->nr_link_slots) * + (6 + (gen->log_level ? 6 : 0)))); /* remember the label where all error branches will jump to */ gen->cleanup_label = gen->insn_cur - gen->insn_start; + /* Detach any programs activated before a later operation failed. */ + for (i = 0; i < gen->nr_link_slots; i++) + emit_sys_close_blob(gen, gen->link_fds + i * sizeof(int)); /* emit cleanup code: close all temp FDs */ for (i = 0; i < nr_progs_sz; i += 4) { emit(gen, BPF_LDX_MEM(BPF_W, BPF_REG_1, BPF_REG_10, -stack_sz + i)); @@ -413,6 +421,13 @@ int bpf_gen__finish(struct bpf_gen *gen, int nr_progs, int nr_maps) sizeof(struct bpf_map_desc) * i + offsetof(struct bpf_map_desc, map_fd), 4, blob_fd_array_off(gen, i)); + for (i = 0; i < gen->nr_link_slots; i++) + move_blob2ctx(gen, + sizeof(struct bpf_loader_ctx) + + sizeof(struct bpf_map_desc) * gen->nr_maps + + sizeof(struct bpf_prog_desc) * gen->nr_link_slots + + sizeof(struct bpf_link_desc) * i, 4, + gen->link_fds + i * sizeof(int)); emit(gen, BPF_MOV64_IMM(BPF_REG_0, 0)); emit(gen, BPF_EXIT_INSN()); if (!gen->error) { diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h index 22204a544b23..a2ee239c114d 100644 --- a/tools/lib/bpf/libbpf.h +++ b/tools/lib/bpf/libbpf.h @@ -1990,9 +1990,10 @@ struct gen_loader_opts { __u32 data_sz; __u32 insns_sz; bool gen_hash; + bool gen_attach; }; -#define gen_loader_opts__last_field gen_hash +#define gen_loader_opts__last_field gen_attach LIBBPF_API int bpf_object__gen_loader(struct bpf_object *obj, struct gen_loader_opts *opts); diff --git a/tools/lib/bpf/skel_internal.h b/tools/lib/bpf/skel_internal.h index 9e16b8e8cb7c..cac7b1d2abfb 100644 --- a/tools/lib/bpf/skel_internal.h +++ b/tools/lib/bpf/skel_internal.h @@ -47,6 +47,10 @@ struct bpf_prog_desc { int prog_fd; }; +struct bpf_link_desc { + int link_fd; +}; + enum { BPF_SKEL_KERNEL = (1ULL << 0), }; -- 2.43.0