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Date: Sun, 29 Mar 2020 20:00:00 -0700
From: Andrii Nakryiko <andriin@...com>
To: <bpf@...r.kernel.org>, <netdev@...r.kernel.org>, <ast@...com>,
<daniel@...earbox.net>, <rdna@...com>
CC: <andrii.nakryiko@...il.com>, <kernel-team@...com>,
Andrii Nakryiko <andriin@...com>
Subject: [PATCH v3 bpf-next 3/4] 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 <andriin@...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(-)
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 8b3f1c098ac0..6241cbcd2a64 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;
--
2.17.1
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