From cc4f864bb118e0ae7bf9f4e3418eaeb083aa34f2 Mon Sep 17 00:00:00 2001 From: Andrii Nakryiko Date: Sun, 29 Mar 2020 20:00:00 -0700 Subject: libbpf: Add support for bpf_link-based cgroup attachment Add bpf_program__attach_cgroup(), which uses BPF_LINK_CREATE subcommand to create an FD-based kernel bpf_link. Also add low-level bpf_link_create() API. If expected_attach_type is not specified explicitly with bpf_program__set_expected_attach_type(), libbpf will try to determine proper attach type from BPF program's section definition. Also add support for bpf_link's underlying BPF program replacement: - unconditional through high-level bpf_link__update_program() API; - cmpxchg-like with specifying expected current BPF program through low-level bpf_link_update() API. Signed-off-by: Andrii Nakryiko Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/20200330030001.2312810-4-andriin@fb.com --- tools/include/uapi/linux/bpf.h | 12 +++++++++++ tools/lib/bpf/bpf.c | 34 +++++++++++++++++++++++++++++++ tools/lib/bpf/bpf.h | 19 +++++++++++++++++ tools/lib/bpf/libbpf.c | 46 ++++++++++++++++++++++++++++++++++++++++++ tools/lib/bpf/libbpf.h | 8 +++++++- tools/lib/bpf/libbpf.map | 4 ++++ 6 files changed, 122 insertions(+), 1 deletion(-) (limited to 'tools') diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index 37dffe5089a0..2e29a671d67e 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -112,6 +112,7 @@ enum bpf_cmd { BPF_MAP_UPDATE_BATCH, BPF_MAP_DELETE_BATCH, BPF_LINK_CREATE, + BPF_LINK_UPDATE, }; enum bpf_map_type { @@ -577,6 +578,17 @@ union bpf_attr { __u32 attach_type; /* attach type */ __u32 flags; /* extra flags */ } link_create; + + struct { /* struct used by BPF_LINK_UPDATE command */ + __u32 link_fd; /* link fd */ + /* new program fd to update link with */ + __u32 new_prog_fd; + __u32 flags; /* extra flags */ + /* expected link's program fd; is specified only if + * BPF_F_REPLACE flag is set in flags */ + __u32 old_prog_fd; + } link_update; + } __attribute__((aligned(8))); /* The description below is an attempt at providing documentation to eBPF diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c index 73220176728d..5cc1b0785d18 100644 --- a/tools/lib/bpf/bpf.c +++ b/tools/lib/bpf/bpf.c @@ -585,6 +585,40 @@ int bpf_prog_detach2(int prog_fd, int target_fd, enum bpf_attach_type type) return sys_bpf(BPF_PROG_DETACH, &attr, sizeof(attr)); } +int bpf_link_create(int prog_fd, int target_fd, + enum bpf_attach_type attach_type, + const struct bpf_link_create_opts *opts) +{ + union bpf_attr attr; + + if (!OPTS_VALID(opts, bpf_link_create_opts)) + return -EINVAL; + + memset(&attr, 0, sizeof(attr)); + attr.link_create.prog_fd = prog_fd; + attr.link_create.target_fd = target_fd; + attr.link_create.attach_type = attach_type; + + return sys_bpf(BPF_LINK_CREATE, &attr, sizeof(attr)); +} + +int bpf_link_update(int link_fd, int new_prog_fd, + const struct bpf_link_update_opts *opts) +{ + union bpf_attr attr; + + if (!OPTS_VALID(opts, bpf_link_update_opts)) + return -EINVAL; + + memset(&attr, 0, sizeof(attr)); + attr.link_update.link_fd = link_fd; + attr.link_update.new_prog_fd = new_prog_fd; + attr.link_update.flags = OPTS_GET(opts, flags, 0); + attr.link_update.old_prog_fd = OPTS_GET(opts, old_prog_fd, 0); + + return sys_bpf(BPF_LINK_UPDATE, &attr, sizeof(attr)); +} + int bpf_prog_query(int target_fd, enum bpf_attach_type type, __u32 query_flags, __u32 *attach_flags, __u32 *prog_ids, __u32 *prog_cnt) { diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h index b976e77316cc..46d47afdd887 100644 --- a/tools/lib/bpf/bpf.h +++ b/tools/lib/bpf/bpf.h @@ -168,6 +168,25 @@ LIBBPF_API int bpf_prog_detach(int attachable_fd, enum bpf_attach_type type); LIBBPF_API int bpf_prog_detach2(int prog_fd, int attachable_fd, enum bpf_attach_type type); +struct bpf_link_create_opts { + size_t sz; /* size of this struct for forward/backward compatibility */ +}; +#define bpf_link_create_opts__last_field sz + +LIBBPF_API int bpf_link_create(int prog_fd, int target_fd, + enum bpf_attach_type attach_type, + const struct bpf_link_create_opts *opts); + +struct bpf_link_update_opts { + size_t sz; /* size of this struct for forward/backward compatibility */ + __u32 flags; /* extra flags */ + __u32 old_prog_fd; /* expected old program FD */ +}; +#define bpf_link_update_opts__last_field old_prog_fd + +LIBBPF_API int bpf_link_update(int link_fd, int new_prog_fd, + const struct bpf_link_update_opts *opts); + struct bpf_prog_test_run_attr { int prog_fd; int repeat; diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 0638e717f502..ff9174282a8c 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -6978,6 +6978,12 @@ struct bpf_link { bool disconnected; }; +/* Replace link's underlying BPF program with the new one */ +int bpf_link__update_program(struct bpf_link *link, struct bpf_program *prog) +{ + return bpf_link_update(bpf_link__fd(link), bpf_program__fd(prog), NULL); +} + /* Release "ownership" of underlying BPF resource (typically, BPF program * attached to some BPF hook, e.g., tracepoint, kprobe, etc). Disconnected * link, when destructed through bpf_link__destroy() call won't attempt to @@ -7533,6 +7539,46 @@ static struct bpf_link *attach_lsm(const struct bpf_sec_def *sec, return bpf_program__attach_lsm(prog); } +struct bpf_link * +bpf_program__attach_cgroup(struct bpf_program *prog, int cgroup_fd) +{ + const struct bpf_sec_def *sec_def; + enum bpf_attach_type attach_type; + char errmsg[STRERR_BUFSIZE]; + struct bpf_link *link; + int prog_fd, link_fd; + + prog_fd = bpf_program__fd(prog); + if (prog_fd < 0) { + pr_warn("program '%s': can't attach before loaded\n", + bpf_program__title(prog, false)); + return ERR_PTR(-EINVAL); + } + + link = calloc(1, sizeof(*link)); + if (!link) + return ERR_PTR(-ENOMEM); + link->detach = &bpf_link__detach_fd; + + attach_type = bpf_program__get_expected_attach_type(prog); + if (!attach_type) { + sec_def = find_sec_def(bpf_program__title(prog, false)); + if (sec_def) + attach_type = sec_def->attach_type; + } + link_fd = bpf_link_create(prog_fd, cgroup_fd, attach_type, NULL); + if (link_fd < 0) { + link_fd = -errno; + free(link); + pr_warn("program '%s': failed to attach to cgroup: %s\n", + bpf_program__title(prog, false), + libbpf_strerror_r(link_fd, errmsg, sizeof(errmsg))); + return ERR_PTR(link_fd); + } + link->fd = link_fd; + return link; +} + struct bpf_link *bpf_program__attach(struct bpf_program *prog) { const struct bpf_sec_def *sec_def; diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h index 55348724c355..44df1d3e7287 100644 --- a/tools/lib/bpf/libbpf.h +++ b/tools/lib/bpf/libbpf.h @@ -224,6 +224,8 @@ LIBBPF_API int bpf_link__fd(const struct bpf_link *link); LIBBPF_API const char *bpf_link__pin_path(const struct bpf_link *link); LIBBPF_API int bpf_link__pin(struct bpf_link *link, const char *path); LIBBPF_API int bpf_link__unpin(struct bpf_link *link); +LIBBPF_API int bpf_link__update_program(struct bpf_link *link, + struct bpf_program *prog); LIBBPF_API void bpf_link__disconnect(struct bpf_link *link); LIBBPF_API int bpf_link__destroy(struct bpf_link *link); @@ -245,13 +247,17 @@ bpf_program__attach_tracepoint(struct bpf_program *prog, LIBBPF_API struct bpf_link * bpf_program__attach_raw_tracepoint(struct bpf_program *prog, const char *tp_name); - LIBBPF_API struct bpf_link * bpf_program__attach_trace(struct bpf_program *prog); LIBBPF_API struct bpf_link * bpf_program__attach_lsm(struct bpf_program *prog); +LIBBPF_API struct bpf_link * +bpf_program__attach_cgroup(struct bpf_program *prog, int cgroup_fd); + struct bpf_map; + LIBBPF_API struct bpf_link *bpf_map__attach_struct_ops(struct bpf_map *map); + struct bpf_insn; /* diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map index eabd3d3e689f..bb8831605b25 100644 --- a/tools/lib/bpf/libbpf.map +++ b/tools/lib/bpf/libbpf.map @@ -243,7 +243,11 @@ LIBBPF_0.0.8 { bpf_link__pin; bpf_link__pin_path; bpf_link__unpin; + bpf_link__update_program; + bpf_link_create; + bpf_link_update; bpf_map__set_initial_value; + bpf_program__attach_cgroup; bpf_program__attach_lsm; bpf_program__is_lsm; bpf_program__set_attach_target; -- cgit v1.2.3