[PATCH bpf-next v2 1/6] bpf: Create links for BPF struct_ops maps.

Kui-Feng Lee
2023-02-23T01:12:56Z

BPF struct_ops maps are employed directly to register TCP Congestion
Control algorithms. Unlike other BPF programs that terminate when
their links gone, the struct_ops program reduces its refcount solely
upon death of its FD. The link of a BPF struct_ops map provides a
uniform experience akin to other types of BPF programs.

bpf_links are responsible for registering their associated
struct_ops. You can only use a struct_ops that has the BPF_F_LINK flag
set to create a bpf_link, while a structs without this flag behaves in
the same manner as before and is registered upon updating its value.

Signed-off-by: Kui-Feng Lee <kuifeng@meta.com>
---
include/linux/bpf.h | 11 +
include/uapi/linux/bpf.h | 12 +-
kernel/bpf/bpf_struct_ops.c | 376 ++++++++++++++++++++++++++++++---
kernel/bpf/syscall.c | 26 ++-
tools/include/uapi/linux/bpf.h | 12 +-
5 files changed, 402 insertions(+), 35 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 8b5d0b4c4ada..9d6fd874e5ee 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1395,6 +1395,11 @@ struct bpf_link {
struct work_struct work;
};

+struct bpf_struct_ops_link {
+ struct bpf_link link;
+ struct bpf_map __rcu *map;
+};
+
struct bpf_link_ops {
void (*release)(struct bpf_link *link);
void (*dealloc)(struct bpf_link *link);
@@ -1961,6 +1966,7 @@ int bpf_link_new_fd(struct bpf_link *link);
struct file *bpf_link_new_file(struct bpf_link *link, int *reserved_fd);
struct bpf_link *bpf_link_get_from_fd(u32 ufd);
struct bpf_link *bpf_link_get_curr_or_next(u32 *id);
+int bpf_struct_ops_link_create(union bpf_attr *attr);

int bpf_obj_pin_user(u32 ufd, const char __user *pathname);
int bpf_obj_get_user(const char __user *pathname, int flags);
@@ -2305,6 +2311,11 @@ static inline void bpf_link_put(struct bpf_link *link)
{
}

+static inline int bpf_struct_ops_link_create(union bpf_attr *attr)
+{
+ return -EOPNOTSUPP;
+}
+
static inline int bpf_obj_get_user(const char __user *pathname, int flags)
{
return -EOPNOTSUPP;
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 17afd2b35ee5..cd0ff39981e8 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -1033,6 +1033,7 @@ enum bpf_attach_type {
BPF_PERF_EVENT,
BPF_TRACE_KPROBE_MULTI,
BPF_LSM_CGROUP,
+ BPF_STRUCT_OPS,
__MAX_BPF_ATTACH_TYPE
};

@@ -1266,6 +1267,9 @@ enum {

/* Create a map that is suitable to be an inner map with dynamic max entries */
BPF_F_INNER_MAP = (1U << 12),
+
+/* Create a map that will be registered/unregesitered by the backed bpf_link */
+ BPF_F_LINK = (1U << 13),
};

/* Flags for BPF_PROG_QUERY. */
@@ -1507,7 +1511,10 @@ union bpf_attr {
} task_fd_query;

struct { /* struct used by BPF_LINK_CREATE command */
- __u32 prog_fd; /* eBPF program to attach */
+ union {
+ __u32 prog_fd; /* eBPF program to attach */
+ __u32 map_fd; /* eBPF struct_ops to attach */
+ };
union {
__u32 target_fd; /* object to attach to */
__u32 target_ifindex; /* target ifindex */
@@ -6354,6 +6361,9 @@ struct bpf_link_info {
struct {
__u32 ifindex;
} xdp;
+ struct {
+ __u32 map_id;
+ } struct_ops;
};
} __attribute__((aligned(8)));

diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
index ece9870cab68..cfc69033c1b8 100644
--- a/kernel/bpf/bpf_struct_ops.c
+++ b/kernel/bpf/bpf_struct_ops.c
@@ -14,8 +14,10 @@

enum bpf_struct_ops_state {
BPF_STRUCT_OPS_STATE_INIT,
+ BPF_STRUCT_OPS_STATE_UNREG,
BPF_STRUCT_OPS_STATE_INUSE,
BPF_STRUCT_OPS_STATE_TOBEFREE,
+ BPF_STRUCT_OPS_STATE_TOBEUNREG,
};

#define BPF_STRUCT_OPS_COMMON_VALUE \
@@ -58,6 +60,8 @@ struct bpf_struct_ops_map {
struct bpf_struct_ops_value kvalue;
};

+static DEFINE_MUTEX(update_mutex);
+
#define VALUE_PREFIX "bpf_struct_ops_"
#define VALUE_PREFIX_LEN (sizeof(VALUE_PREFIX) - 1)

@@ -253,22 +257,23 @@ int bpf_struct_ops_map_sys_lookup_elem(struct bpf_map *map, void *key,
if (unlikely(*(u32 *)key != 0))
return -ENOENT;

+ mutex_lock(&st_map->lock);
+
kvalue = &st_map->kvalue;
- /* Pair with smp_store_release() during map_update */
state = smp_load_acquire(&kvalue->state);
if (state == BPF_STRUCT_OPS_STATE_INIT) {
memset(value, 0, map->value_size);
+ mutex_unlock(&st_map->lock);
return 0;
}

- /* No lock is needed. state and refcnt do not need
- * to be updated together under atomic context.
- */
uvalue = value;
memcpy(uvalue, st_map->uvalue, map->value_size);
uvalue->state = state;
refcount_set(&uvalue->refcnt, refcount_read(&kvalue->refcnt));

+ mutex_unlock(&st_map->lock);
+
return 0;
}

@@ -349,6 +354,150 @@ int bpf_struct_ops_prepare_trampoline(struct bpf_tramp_links *tlinks,
model, flags, tlinks, NULL);
}

+/*
+ * Maintain the state of kvalue.
+ *
+ * For a struct_ops that has no link, its state diagram is
+ *
+ * INIT ----> INUSE --> TOBEFREE
+ * ^ |
+ * | (refcnt == 0) |
+ * +---------------------+
+ *
+ * For a struct_ops that has a link (BPF_F_LINK), its state diagram is
+ *
+ * (refcnt == 0)
+ * +-----------------------+
+ * | |
+ * V |
+ * INIT ---> UNREG -+--> INUSE --> TOBEUNREG
+ * ^ |
+ * | V
+ * +---------- TOBEFREE
+ * (refcnt == 0)
+ *
+ * After transiting to the INUSE state of a struct_ops, the refcnt of
+ * its kvalue is set to 1.
+ *
+ * After transiting from the INUSE state of a struct_ops, the caller
+ * should decrease the refcnt of its kvalue by 1 by calling
+ * bpf_struct_ops_put().
+ *
+ * TOBEFREE and TOBEUNREG are in a grace period, waiting for other
+ * tasks holding references of the struct_ops. When the refcnt drops
+ * from 1 to 0, TOBEFREE and TOBEUNREG are transited to INIT and UNREG
+ * respectively.
+ *
+ * It is safe to assume that there will be no registration race
+ * conditions after a task transits the same struct_ops to INUSE,
+ * TOBEFREE and TOBEUNREG states. The task is able to register or
+ * unregister the struct_ops without the need for any additional
+ * synchronization.
+ */
+static int bpf_struct_ops_transit_state(struct bpf_struct_ops_map *st_map,
+ enum bpf_struct_ops_state src,
+ enum bpf_struct_ops_state dst)
+{
+ int old_state;
+
+ switch (src) {
+ case BPF_STRUCT_OPS_STATE_INIT:
+ if (dst != BPF_STRUCT_OPS_STATE_INUSE &&
+ dst != BPF_STRUCT_OPS_STATE_UNREG)
+ return -EINVAL;
+
+ old_state = cmpxchg(&st_map->kvalue.state, src, dst);
+ if (old_state != src)
+ break;
+
+ if (dst == BPF_STRUCT_OPS_STATE_INUSE)
+ refcount_set(&st_map->kvalue.refcnt, 1);
+ break;
+
+ case BPF_STRUCT_OPS_STATE_UNREG:
+ if (dst != BPF_STRUCT_OPS_STATE_INUSE &&
+ dst != BPF_STRUCT_OPS_STATE_TOBEFREE)
+ return -EINVAL;
+
+ old_state = cmpxchg(&st_map->kvalue.state, src, dst);
+ if (old_state != src)
+ break;
+
+ if (dst == BPF_STRUCT_OPS_STATE_INUSE)
+ refcount_set(&st_map->kvalue.refcnt, 1);
+ else if (dst == BPF_STRUCT_OPS_STATE_TOBEFREE)
+ cmpxchg(&st_map->kvalue.state, dst, BPF_STRUCT_OPS_STATE_INIT);
+ break;
+
+ case BPF_STRUCT_OPS_STATE_INUSE:
+ if (dst != BPF_STRUCT_OPS_STATE_TOBEFREE &&
+ dst != BPF_STRUCT_OPS_STATE_TOBEUNREG)
+ return -EINVAL;
+
+ old_state = cmpxchg(&st_map->kvalue.state, src, dst);
+ break;
+
+ case BPF_STRUCT_OPS_STATE_TOBEFREE:
+ /*
+ * This transition should only be performed when the
+ * refcnt drops to 0 from 1.
+ */
+ if (dst != BPF_STRUCT_OPS_STATE_INIT)
+ return -EINVAL;
+ old_state = cmpxchg(&st_map->kvalue.state, src, dst);
+ if (old_state != src)
+ break;
+ break;
+
+ case BPF_STRUCT_OPS_STATE_TOBEUNREG:
+ /*
+ * This transition should only be performed when the
+ * refcnt drops to 0 from 1.
+ */
+ if (dst != BPF_STRUCT_OPS_STATE_UNREG)
+ return -EINVAL;
+ old_state = cmpxchg(&st_map->kvalue.state, src, dst);
+ if (old_state != src)
+ return old_state;
+ break;
+
+ default:
+ return -EOPNOTSUPP;
+ }
+
+ return old_state;
+}
+
+static int bpf_struct_ops_transit_state_check(struct bpf_struct_ops_map *st_map,
+ enum bpf_struct_ops_state src,
+ enum bpf_struct_ops_state dst)
+{
+ int err;
+
+ err = bpf_struct_ops_transit_state(st_map, src, dst);
+ if (err < 0)
+ return err;
+ if (err != src)
+ return -EINVAL;
+ return 0;
+}
+
+/*
+ * Restore the state of a struct_ops to UNREG from INUSE.
+ *
+ * It handles the case which a struct_ops transited to INUSE from
+ * UNREG successfully; somehow, need to rollback the struct_ops state.
+ */
+static void bpf_struct_ops_restore_unreg(struct bpf_struct_ops_map *st_map)
+{
+ struct bpf_struct_ops_value *kvalue;
+
+ kvalue = &st_map->kvalue;
+ refcount_set(&kvalue->refcnt, 0);
+ /* Make sure the above change is seen before the state change. */
+ smp_store_release(&kvalue->state, BPF_STRUCT_OPS_STATE_UNREG);
+}
+
static int bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
void *value, u64 flags)
{
@@ -390,7 +539,11 @@ static int bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,

mutex_lock(&st_map->lock);

- if (kvalue->state != BPF_STRUCT_OPS_STATE_INIT) {
+ /* Make sure that all following changes are seen after the
+ * state value here.
+ */
+ if (smp_load_acquire(&kvalue->state) >= BPF_STRUCT_OPS_STATE_INUSE ||
+ refcount_read(&kvalue->refcnt)) {
err = -EBUSY;
goto unlock;
}
@@ -491,17 +644,21 @@ static int bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
*(unsigned long *)(udata + moff) = prog->aux->id;
}

- refcount_set(&kvalue->refcnt, 1);
+ if (st_map->map.map_flags & BPF_F_LINK) {
+ /* Let bpf_link handle registration & unregistration. */
+ err = bpf_struct_ops_transit_state_check(st_map, BPF_STRUCT_OPS_STATE_INIT,
+ BPF_STRUCT_OPS_STATE_UNREG);
+ goto unlock;
+ }
+
bpf_map_inc(map);

set_memory_rox((long)st_map->image, 1);
err = st_ops->reg(kdata);
if (likely(!err)) {
- /* Pair with smp_load_acquire() during lookup_elem().
- * It ensures the above udata updates (e.g. prog->aux->id)
- * can be seen once BPF_STRUCT_OPS_STATE_INUSE is set.
- */
- smp_store_release(&kvalue->state, BPF_STRUCT_OPS_STATE_INUSE);
+ /* Infallible */
+ bpf_struct_ops_transit_state(st_map, BPF_STRUCT_OPS_STATE_INIT,
+ BPF_STRUCT_OPS_STATE_INUSE);
goto unlock;
}

@@ -526,28 +683,49 @@ static int bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,

static int bpf_struct_ops_map_delete_elem(struct bpf_map *map, void *key)
{
- enum bpf_struct_ops_state prev_state;
struct bpf_struct_ops_map *st_map;
+ int old_state;
+ int err = 0;

st_map = (struct bpf_struct_ops_map *)map;
- prev_state = cmpxchg(&st_map->kvalue.state,
- BPF_STRUCT_OPS_STATE_INUSE,
- BPF_STRUCT_OPS_STATE_TOBEFREE);
- switch (prev_state) {
+
+ old_state = bpf_struct_ops_transit_state(st_map,
+ (st_map->map.map_flags & BPF_F_LINK ?
+ BPF_STRUCT_OPS_STATE_UNREG :
+ BPF_STRUCT_OPS_STATE_INUSE),
+ BPF_STRUCT_OPS_STATE_TOBEFREE);
+
+ if (old_state < 0)
+ return old_state;
+
+ switch (old_state) {
+ case BPF_STRUCT_OPS_STATE_UNREG:
+ break;
case BPF_STRUCT_OPS_STATE_INUSE:
- st_map->st_ops->unreg(&st_map->kvalue.data);
- if (refcount_dec_and_test(&st_map->kvalue.refcnt))
- bpf_map_put(map);
- return 0;
+ if (st_map->map.map_flags & BPF_F_LINK)
+ err = -EBUSY;
+ else {
+ st_map->st_ops->unreg(&st_map->kvalue.data);
+ bpf_struct_ops_put(&st_map->kvalue.data);
+ }
+ break;
case BPF_STRUCT_OPS_STATE_TOBEFREE:
- return -EINPROGRESS;
+ err = -EINPROGRESS;
+ break;
+ case BPF_STRUCT_OPS_STATE_TOBEUNREG:
+ err = -EBUSY;
+ break;
case BPF_STRUCT_OPS_STATE_INIT:
- return -ENOENT;
+ err = -ENOENT;
+ break;
default:
WARN_ON_ONCE(1);
/* Should never happen. Treat it as not found. */
- return -ENOENT;
+ err = -ENOENT;
+ break;
}
+
+ return err;
}

static void bpf_struct_ops_map_seq_show_elem(struct bpf_map *map, void *key,
@@ -585,7 +763,7 @@ static void bpf_struct_ops_map_free(struct bpf_map *map)
static int bpf_struct_ops_map_alloc_check(union bpf_attr *attr)
{
if (attr->key_size != sizeof(unsigned int) || attr->max_entries != 1 ||
- attr->map_flags || !attr->btf_vmlinux_value_type_id)
+ (attr->map_flags & ~BPF_F_LINK) || !attr->btf_vmlinux_value_type_id)
return -EINVAL;
return 0;
}
@@ -671,6 +849,15 @@ static void bpf_struct_ops_put_rcu(struct rcu_head *head)
struct bpf_struct_ops_map *st_map;

st_map = container_of(head, struct bpf_struct_ops_map, rcu);
+
+ /* The struct_ops can be reused after a rcu grace period. */
+ if (st_map->kvalue.state == BPF_STRUCT_OPS_STATE_TOBEFREE)
+ bpf_struct_ops_transit_state(st_map, BPF_STRUCT_OPS_STATE_TOBEFREE,
+ BPF_STRUCT_OPS_STATE_INIT);
+ else if (st_map->kvalue.state == BPF_STRUCT_OPS_STATE_TOBEUNREG)
+ bpf_struct_ops_transit_state(st_map, BPF_STRUCT_OPS_STATE_TOBEUNREG,
+ BPF_STRUCT_OPS_STATE_UNREG);
+
bpf_map_put(&st_map->map);
}

@@ -684,6 +871,7 @@ void bpf_struct_ops_put(const void *kdata)

st_map = container_of(kvalue, struct bpf_struct_ops_map,
kvalue);
+
/* The struct_ops's function may switch to another struct_ops.
*
* For example, bpf_tcp_cc_x->init() may switch to
@@ -698,3 +886,143 @@ void bpf_struct_ops_put(const void *kdata)
call_rcu(&st_map->rcu, bpf_struct_ops_put_rcu);
}
}
+
+static void bpf_struct_ops_map_link_dealloc(struct bpf_link *link)
+{
+ struct bpf_struct_ops_link *st_link;
+ struct bpf_struct_ops_map *st_map;
+
+ st_link = container_of(link, struct bpf_struct_ops_link, link);
+ if (st_link->map) {
+ st_map = (struct bpf_struct_ops_map *)st_link->map;
+ bpf_struct_ops_transit_state(st_map, BPF_STRUCT_OPS_STATE_INUSE,
+ (st_map->map.map_flags & BPF_F_LINK ?
+ BPF_STRUCT_OPS_STATE_TOBEUNREG :
+ BPF_STRUCT_OPS_STATE_TOBEFREE));
+ st_map->st_ops->unreg(&st_map->kvalue.data);
+ bpf_struct_ops_put(&st_map->kvalue.data);
+ }
+ kfree(st_link);
+}
+
+static int bpf_struct_ops_map_link_detach(struct bpf_link *link)
+{
+ struct bpf_struct_ops_link *st_link;
+ struct bpf_struct_ops_map *st_map;
+
+ mutex_lock(&update_mutex);
+ st_link = container_of(link, struct bpf_struct_ops_link, link);
+ st_map = container_of(st_link->map, struct bpf_struct_ops_map, map);
+ if (st_map) {
+ /*
+ * All chaning on st_link->map are protected by
+ * update_mutex. This ensures that the struct_ops is
+ * INUSE, and the state transition always success.
+ */
+ rcu_assign_pointer(st_link->map, NULL);
+ bpf_struct_ops_transit_state(st_map, BPF_STRUCT_OPS_STATE_INUSE,
+ (st_map->map.map_flags & BPF_F_LINK ?
+ BPF_STRUCT_OPS_STATE_TOBEUNREG :
+ BPF_STRUCT_OPS_STATE_TOBEFREE));
+ st_map->st_ops->unreg(&st_map->kvalue.data);
+ bpf_struct_ops_put(&st_map->kvalue.data);
+ }
+ mutex_unlock(&update_mutex);
+
+ return 0;
+}
+
+static void bpf_struct_ops_map_link_show_fdinfo(const struct bpf_link *link,
+ struct seq_file *seq)
+{
+ struct bpf_struct_ops_link *st_link;
+ struct bpf_map *map;
+
+ st_link = container_of(link, struct bpf_struct_ops_link, link);
+ rcu_read_lock_trace();
+ map = rcu_dereference(st_link->map);
+ if (map)
+ seq_printf(seq, "map_id:\t%d\n", map->id);
+ rcu_read_unlock_trace();
+}
+
+static int bpf_struct_ops_map_link_fill_link_info(const struct bpf_link *link,
+ struct bpf_link_info *info)
+{
+ struct bpf_struct_ops_link *st_link;
+ struct bpf_map *map;
+
+ st_link = container_of(link, struct bpf_struct_ops_link, link);
+ rcu_read_lock_trace();
+ map = rcu_dereference(st_link->map);
+ if (map)
+ info->struct_ops.map_id = map->id;
+ rcu_read_unlock_trace();
+ return 0;
+}
+
+static const struct bpf_link_ops bpf_struct_ops_map_lops = {
+ .dealloc = bpf_struct_ops_map_link_dealloc,
+ .detach = bpf_struct_ops_map_link_detach,
+ .show_fdinfo = bpf_struct_ops_map_link_show_fdinfo,
+ .fill_link_info = bpf_struct_ops_map_link_fill_link_info,
+};
+
+int bpf_struct_ops_link_create(union bpf_attr *attr)
+{
+ struct bpf_struct_ops_link *link = NULL;
+ struct bpf_link_primer link_primer;
+ struct bpf_struct_ops_map *st_map;
+ struct bpf_map *map;
+ int err;
+
+ map = bpf_map_get(attr->link_create.map_fd);
+ if (!map)
+ return -EINVAL;
+
+ if (map->map_type != BPF_MAP_TYPE_STRUCT_OPS || !(map->map_flags & BPF_F_LINK)) {
+ err = -EINVAL;
+ goto err_out;
+ }
+
+ link = kzalloc(sizeof(*link), GFP_USER);
+ if (!link) {
+ err = -ENOMEM;
+ goto err_out;
+ }
+ bpf_link_init(&link->link, BPF_LINK_TYPE_STRUCT_OPS, &bpf_struct_ops_map_lops, NULL);
+ link->map = map;
+
+ st_map = (struct bpf_struct_ops_map *)map;
+
+ err = bpf_struct_ops_transit_state_check(st_map, BPF_STRUCT_OPS_STATE_UNREG,
+ BPF_STRUCT_OPS_STATE_INUSE);
+ if (err)
+ goto err_out;
+
+ err = bpf_link_prime(&link->link, &link_primer);
+ if (err) {
+ bpf_struct_ops_restore_unreg(st_map);
+ goto err_out;
+ }
+
+ set_memory_rox((long)st_map->image, 1);
+ err = st_map->st_ops->reg(st_map->kvalue.data);
+ if (err) {
+ bpf_struct_ops_restore_unreg(st_map);
+ bpf_link_cleanup(&link_primer);
+
+ set_memory_nx((long)st_map->image, 1);
+ set_memory_rw((long)st_map->image, 1);
+ goto err_out;
+ }
+
+
+ return bpf_link_settle(&link_primer);
+
+err_out:
+ bpf_map_put(map);
+ kfree(link);
+ return err;
+}
+
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index cda8d00f3762..2670de8dd0d4 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2735,10 +2735,11 @@ void bpf_link_inc(struct bpf_link *link)
static void bpf_link_free(struct bpf_link *link)
{
bpf_link_free_id(link->id);
+ /* detach BPF program, clean up used resources */
if (link->prog) {
- /* detach BPF program, clean up used resources */
link->ops->release(link);
bpf_prog_put(link->prog);
+ /* The struct_ops links clean up map by them-selves. */
}
/* free bpf_link and its containing memory */
link->ops->dealloc(link);
@@ -2794,16 +2795,19 @@ static void bpf_link_show_fdinfo(struct seq_file *m, struct file *filp)
const struct bpf_prog *prog = link->prog;
char prog_tag[sizeof(prog->tag) * 2 + 1] = { };

- bin2hex(prog_tag, prog->tag, sizeof(prog->tag));
seq_printf(m,
"link_type:\t%s\n"
- "link_id:\t%u\n"
- "prog_tag:\t%s\n"
- "prog_id:\t%u\n",
+ "link_id:\t%u\n",
bpf_link_type_strs[link->type],
- link->id,
- prog_tag,
- prog->aux->id);
+ link->id);
+ if (prog) {
+ bin2hex(prog_tag, prog->tag, sizeof(prog->tag));
+ seq_printf(m,
+ "prog_tag:\t%s\n"
+ "prog_id:\t%u\n",
+ prog_tag,
+ prog->aux->id);
+ }
if (link->ops->show_fdinfo)
link->ops->show_fdinfo(link, m);
}
@@ -4278,7 +4282,8 @@ static int bpf_link_get_info_by_fd(struct file *file,

info.type = link->type;
info.id = link->id;
- info.prog_id = link->prog->aux->id;
+ if (link->prog)
+ info.prog_id = link->prog->aux->id;

if (link->ops->fill_link_info) {
err = link->ops->fill_link_info(link, &info);
@@ -4541,6 +4546,9 @@ static int link_create(union bpf_attr *attr, bpfptr_t uattr)
if (CHECK_ATTR(BPF_LINK_CREATE))
return -EINVAL;

+ if (attr->link_create.attach_type == BPF_STRUCT_OPS)
+ return bpf_struct_ops_link_create(attr);
+
prog = bpf_prog_get(attr->link_create.prog_fd);
if (IS_ERR(prog))
return PTR_ERR(prog);
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 17afd2b35ee5..cd0ff39981e8 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -1033,6 +1033,7 @@ enum bpf_attach_type {
BPF_PERF_EVENT,
BPF_TRACE_KPROBE_MULTI,
BPF_LSM_CGROUP,
+ BPF_STRUCT_OPS,
__MAX_BPF_ATTACH_TYPE
};

@@ -1266,6 +1267,9 @@ enum {

/* Create a map that is suitable to be an inner map with dynamic max entries */
BPF_F_INNER_MAP = (1U << 12),
+
+/* Create a map that will be registered/unregesitered by the backed bpf_link */
+ BPF_F_LINK = (1U << 13),
};

/* Flags for BPF_PROG_QUERY. */
@@ -1507,7 +1511,10 @@ union bpf_attr {
} task_fd_query;

struct { /* struct used by BPF_LINK_CREATE command */
- __u32 prog_fd; /* eBPF program to attach */
+ union {
+ __u32 prog_fd; /* eBPF program to attach */
+ __u32 map_fd; /* eBPF struct_ops to attach */
+ };
union {
__u32 target_fd; /* object to attach to */
__u32 target_ifindex; /* target ifindex */
@@ -6354,6 +6361,9 @@ struct bpf_link_info {
struct {
__u32 ifindex;
} xdp;
+ struct {
+ __u32 map_id;
+ } struct_ops;
};
} __attribute__((aligned(8)));

--
2.30.2