Commit de4e05ca authored by Yonghong Song's avatar Yonghong Song Committed by Alexei Starovoitov

bpf: Support bpf tracing/iter programs for BPF_LINK_CREATE

Given a bpf program, the step to create an anonymous bpf iterator is:
  - create a bpf_iter_link, which combines bpf program and the target.
    In the future, there could be more information recorded in the link.
    A link_fd will be returned to the user space.
  - create an anonymous bpf iterator with the given link_fd.

The bpf_iter_link can be pinned to bpffs mount file system to
create a file based bpf iterator as well.

The benefit to use of bpf_iter_link:
  - using bpf link simplifies design and implementation as bpf link
    is used for other tracing bpf programs.
  - for file based bpf iterator, bpf_iter_link provides a standard
    way to replace underlying bpf programs.
  - for both anonymous and free based iterators, bpf link query
    capability can be leveraged.

The patch added support of tracing/iter programs for BPF_LINK_CREATE.
A new link type BPF_LINK_TYPE_ITER is added to facilitate link
querying. Currently, only prog_id is needed, so there is no
additional in-kernel show_fdinfo() and fill_link_info() hook
is needed for BPF_LINK_TYPE_ITER link.
Signed-off-by: default avatarYonghong Song <yhs@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarAndrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200509175901.2475084-1-yhs@fb.com
parent 15d83c4d
......@@ -1143,6 +1143,7 @@ struct bpf_iter_reg {
int bpf_iter_reg_target(struct bpf_iter_reg *reg_info);
void bpf_iter_unreg_target(const char *target);
bool bpf_iter_prog_supported(struct bpf_prog *prog);
int bpf_iter_link_attach(const union bpf_attr *attr, struct bpf_prog *prog);
int bpf_percpu_hash_copy(struct bpf_map *map, void *key, void *value);
int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value);
......
......@@ -124,3 +124,4 @@ BPF_LINK_TYPE(BPF_LINK_TYPE_TRACING, tracing)
#ifdef CONFIG_CGROUP_BPF
BPF_LINK_TYPE(BPF_LINK_TYPE_CGROUP, cgroup)
#endif
BPF_LINK_TYPE(BPF_LINK_TYPE_ITER, iter)
......@@ -229,6 +229,7 @@ enum bpf_link_type {
BPF_LINK_TYPE_RAW_TRACEPOINT = 1,
BPF_LINK_TYPE_TRACING = 2,
BPF_LINK_TYPE_CGROUP = 3,
BPF_LINK_TYPE_ITER = 4,
MAX_BPF_LINK_TYPE,
};
......
......@@ -15,6 +15,11 @@ struct bpf_iter_target_info {
u32 btf_id; /* cached value */
};
struct bpf_iter_link {
struct bpf_link link;
struct bpf_iter_target_info *tinfo;
};
static struct list_head targets = LIST_HEAD_INIT(targets);
static DEFINE_MUTEX(targets_mutex);
......@@ -93,3 +98,60 @@ bool bpf_iter_prog_supported(struct bpf_prog *prog)
return supported;
}
static void bpf_iter_link_release(struct bpf_link *link)
{
}
static void bpf_iter_link_dealloc(struct bpf_link *link)
{
struct bpf_iter_link *iter_link =
container_of(link, struct bpf_iter_link, link);
kfree(iter_link);
}
static const struct bpf_link_ops bpf_iter_link_lops = {
.release = bpf_iter_link_release,
.dealloc = bpf_iter_link_dealloc,
};
int bpf_iter_link_attach(const union bpf_attr *attr, struct bpf_prog *prog)
{
struct bpf_link_primer link_primer;
struct bpf_iter_target_info *tinfo;
struct bpf_iter_link *link;
bool existed = false;
u32 prog_btf_id;
int err;
if (attr->link_create.target_fd || attr->link_create.flags)
return -EINVAL;
prog_btf_id = prog->aux->attach_btf_id;
mutex_lock(&targets_mutex);
list_for_each_entry(tinfo, &targets, list) {
if (tinfo->btf_id == prog_btf_id) {
existed = true;
break;
}
}
mutex_unlock(&targets_mutex);
if (!existed)
return -ENOENT;
link = kzalloc(sizeof(*link), GFP_USER | __GFP_NOWARN);
if (!link)
return -ENOMEM;
bpf_link_init(&link->link, BPF_LINK_TYPE_ITER, &bpf_iter_link_lops, prog);
link->tinfo = tinfo;
err = bpf_link_prime(&link->link, &link_primer);
if (err) {
kfree(link);
return err;
}
return bpf_link_settle(&link_primer);
}
......@@ -2729,6 +2729,8 @@ attach_type_to_prog_type(enum bpf_attach_type attach_type)
case BPF_CGROUP_GETSOCKOPT:
case BPF_CGROUP_SETSOCKOPT:
return BPF_PROG_TYPE_CGROUP_SOCKOPT;
case BPF_TRACE_ITER:
return BPF_PROG_TYPE_TRACING;
default:
return BPF_PROG_TYPE_UNSPEC;
}
......@@ -3729,6 +3731,15 @@ static int bpf_map_do_batch(const union bpf_attr *attr,
return err;
}
static int tracing_bpf_link_attach(const union bpf_attr *attr, struct bpf_prog *prog)
{
if (attr->link_create.attach_type == BPF_TRACE_ITER &&
prog->expected_attach_type == BPF_TRACE_ITER)
return bpf_iter_link_attach(attr, prog);
return -EINVAL;
}
#define BPF_LINK_CREATE_LAST_FIELD link_create.flags
static int link_create(union bpf_attr *attr)
{
......@@ -3765,6 +3776,9 @@ static int link_create(union bpf_attr *attr)
case BPF_PROG_TYPE_CGROUP_SOCKOPT:
ret = cgroup_bpf_link_attach(attr, prog);
break;
case BPF_PROG_TYPE_TRACING:
ret = tracing_bpf_link_attach(attr, prog);
break;
default:
ret = -EINVAL;
}
......
......@@ -229,6 +229,7 @@ enum bpf_link_type {
BPF_LINK_TYPE_RAW_TRACEPOINT = 1,
BPF_LINK_TYPE_TRACING = 2,
BPF_LINK_TYPE_CGROUP = 3,
BPF_LINK_TYPE_ITER = 4,
MAX_BPF_LINK_TYPE,
};
......
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