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tools/libbpf: Add bpf_iter support

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Two new libbpf APIs are added to support bpf_iter:
  - bpf_program__attach_iter
    Given a bpf program and additional parameters, which is
    none now, returns a bpf_link.
  - bpf_iter_create
    syscall level API to create a bpf iterator.

The macro BPF_SEQ_PRINTF are also introduced. The format
looks like:
  BPF_SEQ_PRINTF(seq, "task id %d\n", pid);

This macro can help bpf program writers with
nicer bpf_seq_printf syntax similar to the kernel one.

Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200509175917.2476936-1-yhs@fb.com
This commit is contained in:
Yonghong Song
2020-05-09 10:59:17 -07:00
committed by Andrii Nakryiko
parent 7112841ade
commit 021e35fba2
6 changed files with 91 additions and 0 deletions
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52
src/libbpf.c
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@@ -6586,6 +6586,8 @@ static struct bpf_link *attach_trace(const struct bpf_sec_def *sec,
struct bpf_program *prog);
static struct bpf_link *attach_lsm(const struct bpf_sec_def *sec,
struct bpf_program *prog);
static struct bpf_link *attach_iter(const struct bpf_sec_def *sec,
struct bpf_program *prog);
static const struct bpf_sec_def section_defs[] = {
BPF_PROG_SEC("socket", BPF_PROG_TYPE_SOCKET_FILTER),
@@ -6629,6 +6631,10 @@ static const struct bpf_sec_def section_defs[] = {
.is_attach_btf = true,
.expected_attach_type = BPF_LSM_MAC,
.attach_fn = attach_lsm),
SEC_DEF("iter/", TRACING,
.expected_attach_type = BPF_TRACE_ITER,
.is_attach_btf = true,
.attach_fn = attach_iter),
BPF_PROG_SEC("xdp", BPF_PROG_TYPE_XDP),
BPF_PROG_SEC("perf_event", BPF_PROG_TYPE_PERF_EVENT),
BPF_PROG_SEC("lwt_in", BPF_PROG_TYPE_LWT_IN),
@@ -6891,6 +6897,7 @@ invalid_prog:
#define BTF_TRACE_PREFIX "btf_trace_"
#define BTF_LSM_PREFIX "bpf_lsm_"
#define BTF_ITER_PREFIX "__bpf_iter__"
#define BTF_MAX_NAME_SIZE 128
static int find_btf_by_prefix_kind(const struct btf *btf, const char *prefix,
@@ -6921,6 +6928,9 @@ static inline int __find_vmlinux_btf_id(struct btf *btf, const char *name,
else if (attach_type == BPF_LSM_MAC)
err = find_btf_by_prefix_kind(btf, BTF_LSM_PREFIX, name,
BTF_KIND_FUNC);
else if (attach_type == BPF_TRACE_ITER)
err = find_btf_by_prefix_kind(btf, BTF_ITER_PREFIX, name,
BTF_KIND_FUNC);
else
err = btf__find_by_name_kind(btf, name, BTF_KIND_FUNC);
@@ -7848,6 +7858,12 @@ static struct bpf_link *attach_lsm(const struct bpf_sec_def *sec,
return bpf_program__attach_lsm(prog);
}
static struct bpf_link *attach_iter(const struct bpf_sec_def *sec,
struct bpf_program *prog)
{
return bpf_program__attach_iter(prog, NULL);
}
struct bpf_link *
bpf_program__attach_cgroup(struct bpf_program *prog, int cgroup_fd)
{
@@ -7882,6 +7898,42 @@ bpf_program__attach_cgroup(struct bpf_program *prog, int cgroup_fd)
return link;
}
struct bpf_link *
bpf_program__attach_iter(struct bpf_program *prog,
const struct bpf_iter_attach_opts *opts)
{
char errmsg[STRERR_BUFSIZE];
struct bpf_link *link;
int prog_fd, link_fd;
if (!OPTS_VALID(opts, bpf_iter_attach_opts))
return ERR_PTR(-EINVAL);
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;
link_fd = bpf_link_create(prog_fd, 0, BPF_TRACE_ITER, NULL);
if (link_fd < 0) {
link_fd = -errno;
free(link);
pr_warn("program '%s': failed to attach to iterator: %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;