On 2/25/22 3:43 PM, Hao Luo wrote:
Introduce a new type of iter prog: cgroup. Unlike other bpf_iter, this
iter doesn't iterate a set of kernel objects. Instead, it is supposed to
be parameterized by a cgroup id and prints only that cgroup. So one
needs to specify a target cgroup id when attaching this iter.
The target cgroup's state can be read out via a link of this iter.
Typically, we can monitor cgroup creation and deletion using sleepable
tracing and use it to create corresponding directories in bpffs and pin
a cgroup id parameterized link in the directory. Then we can read the
auto-pinned iter link to get cgroup's state. The output of the iter link
is determined by the program. See the selftest test_cgroup_stats.c for
an example.
Signed-off-by: Hao Luo <haoluo@xxxxxxxxxx>
---
include/linux/bpf.h | 1 +
include/uapi/linux/bpf.h | 6 ++
kernel/bpf/Makefile | 2 +-
kernel/bpf/cgroup_iter.c | 141 +++++++++++++++++++++++++++++++++
tools/include/uapi/linux/bpf.h | 6 ++
5 files changed, 155 insertions(+), 1 deletion(-)
create mode 100644 kernel/bpf/cgroup_iter.c
[...]
+
+static const struct seq_operations cgroup_iter_seq_ops = {
+ .start = cgroup_iter_seq_start,
+ .next = cgroup_iter_seq_next,
+ .stop = cgroup_iter_seq_stop,
+ .show = cgroup_iter_seq_show,
+};
+
+BTF_ID_LIST_SINGLE(bpf_cgroup_btf_id, struct, cgroup)
+
+static int cgroup_iter_seq_init(void *priv_data, struct bpf_iter_aux_info *aux)
+{
+ *(u64 *)priv_data = aux->cgroup_id;
+ return 0;
+}
+
+static void cgroup_iter_seq_fini(void *priv_data)
+{
+}
+
+static const struct bpf_iter_seq_info cgroup_iter_seq_info = {
+ .seq_ops = &cgroup_iter_seq_ops,
+ .init_seq_private = cgroup_iter_seq_init,
+ .fini_seq_private = cgroup_iter_seq_fini,
Since cgroup_iter_seq_fini() is a nop, you can just have
.fini_seq_private = NULL,
+ .seq_priv_size = sizeof(u64),
+};
+
+static int bpf_iter_attach_cgroup(struct bpf_prog *prog,
+ union bpf_iter_link_info *linfo,
+ struct bpf_iter_aux_info *aux)
+{
+ aux->cgroup_id = linfo->cgroup.cgroup_id;
+ return 0;
+}
+
+static void bpf_iter_detach_cgroup(struct bpf_iter_aux_info *aux)
+{
+}
+
+void bpf_iter_cgroup_show_fdinfo(const struct bpf_iter_aux_info *aux,
+ struct seq_file *seq)
+{
+ char buf[64] = {0};
Is this 64 the maximum possible cgroup path length?
If there is a macro for that, I think it would be good to use it.
+
+ cgroup_path_from_kernfs_id(aux->cgroup_id, buf, sizeof(buf));
cgroup_path_from_kernfs_id() might fail in which case, buf will be 0.
and cgroup_path will be nothing. I guess this might be the expected
result. I might be good to add a comment to clarify in the code.
+ seq_printf(seq, "cgroup_id:\t%lu\n", aux->cgroup_id);
+ seq_printf(seq, "cgroup_path:\t%s\n", buf);
+}
+
+int bpf_iter_cgroup_fill_link_info(const struct bpf_iter_aux_info *aux,
+ struct bpf_link_info *info)
+{
+ info->iter.cgroup.cgroup_id = aux->cgroup_id;
+ return 0;
+}
+
+DEFINE_BPF_ITER_FUNC(cgroup, struct bpf_iter_meta *meta,
+ struct cgroup *cgroup)
+
+static struct bpf_iter_reg bpf_cgroup_reg_info = {
+ .target = "cgroup",
+ .attach_target = bpf_iter_attach_cgroup,
+ .detach_target = bpf_iter_detach_cgroup,
The same ehre, since bpf_iter_detach_cgroup() is a nop,
you can replace it with NULL in the above.
+ .show_fdinfo = bpf_iter_cgroup_show_fdinfo,
+ .fill_link_info = bpf_iter_cgroup_fill_link_info,
+ .ctx_arg_info_size = 1,
+ .ctx_arg_info = {
+ { offsetof(struct bpf_iter__cgroup, cgroup),
+ PTR_TO_BTF_ID },
+ },
+ .seq_info = &cgroup_iter_seq_info,
+};
+
+static int __init bpf_cgroup_iter_init(void)
+{
+ bpf_cgroup_reg_info.ctx_arg_info[0].btf_id = bpf_cgroup_btf_id[0];
+ return bpf_iter_reg_target(&bpf_cgroup_reg_info);
+}
+
[...]
