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/* SPDX-License-Identifier: GPL-2.0 */
/* Copyright (c) 2023 Isovalent */
#ifndef __BPF_MPROG_H
#define __BPF_MPROG_H
#include <linux/bpf.h>
/* bpf_mprog framework:
*
* bpf_mprog is a generic layer for multi-program attachment. In-kernel users
* of the bpf_mprog don't need to care about the dependency resolution
* internals, they can just consume it with few API calls. Currently available
* dependency directives are BPF_F_{BEFORE,AFTER} which enable insertion of
* a BPF program or BPF link relative to an existing BPF program or BPF link
* inside the multi-program array as well as prepend and append behavior if
* no relative object was specified, see corresponding selftests for concrete
* examples (e.g. tc_links and tc_opts test cases of test_progs).
*
* Usage of bpf_mprog_{attach,detach,query}() core APIs with pseudo code:
*
* Attach case:
*
* struct bpf_mprog_entry *entry, *entry_new;
* int ret;
*
* // bpf_mprog user-side lock
* // fetch active @entry from attach location
* [...]
* ret = bpf_mprog_attach(entry, &entry_new, [...]);
* if (!ret) {
* if (entry != entry_new) {
* // swap @entry to @entry_new at attach location
* // ensure there are no inflight users of @entry:
* synchronize_rcu();
* }
* bpf_mprog_commit(entry);
* } else {
* // error path, bail out, propagate @ret
* }
* // bpf_mprog user-side unlock
*
* Detach case:
*
* struct bpf_mprog_entry *entry, *entry_new;
* int ret;
*
* // bpf_mprog user-side lock
* // fetch active @entry from attach location
* [...]
* ret = bpf_mprog_detach(entry, &entry_new, [...]);
* if (!ret) {
* // all (*) marked is optional and depends on the use-case
* // whether bpf_mprog_bundle should be freed or not
* if (!bpf_mprog_total(entry_new)) (*)
* entry_new = NULL (*)
* // swap @entry to @entry_new at attach location
* // ensure there are no inflight users of @entry:
* synchronize_rcu();
* bpf_mprog_commit(entry);
* if (!entry_new) (*)
* // free bpf_mprog_bundle (*)
* } else {
* // error path, bail out, propagate @ret
* }
* // bpf_mprog user-side unlock
*
* Query case:
*
* struct bpf_mprog_entry *entry;
* int ret;
*
* // bpf_mprog user-side lock
* // fetch active @entry from attach location
* [...]
* ret = bpf_mprog_query(attr, uattr, entry);
* // bpf_mprog user-side unlock
*
* Data/fast path:
*
* struct bpf_mprog_entry *entry;
* struct bpf_mprog_fp *fp;
* struct bpf_prog *prog;
* int ret = [...];
*
* rcu_read_lock();
* // fetch active @entry from attach location
* [...]
* bpf_mprog_foreach_prog(entry, fp, prog) {
* ret = bpf_prog_run(prog, [...]);
* // process @ret from program
* }
* [...]
* rcu_read_unlock();
*
* bpf_mprog locking considerations:
*
* bpf_mprog_{attach,detach,query}() must be protected by an external lock
* (like RTNL in case of tcx).
*
* bpf_mprog_entry pointer can be an __rcu annotated pointer (in case of tcx
* the netdevice has tcx_ingress and tcx_egress __rcu pointer) which gets
* updated via rcu_assign_pointer() pointing to the active bpf_mprog_entry of
* the bpf_mprog_bundle.
*
* Fast path accesses the active bpf_mprog_entry within RCU critical section
* (in case of tcx it runs in NAPI which provides RCU protection there,
* other users might need explicit rcu_read_lock()). The bpf_mprog_commit()
* assumes that for the old bpf_mprog_entry there are no inflight users
* anymore.
*
* The READ_ONCE()/WRITE_ONCE() pairing for bpf_mprog_fp's prog access is for
* the replacement case where we don't swap the bpf_mprog_entry.
*/
#define bpf_mprog_foreach_tuple(entry, fp, cp, t) \
for (fp = &entry->fp_items[0], cp = &entry->parent->cp_items[0];\
({ \
t.prog = READ_ONCE(fp->prog); \
t.link = cp->link; \
t.prog; \
}); \
fp++, cp++)
#define bpf_mprog_foreach_prog(entry, fp, p) \
for (fp = &entry->fp_items[0]; \
(p = READ_ONCE(fp->prog)); \
fp++)
#define BPF_MPROG_MAX 64
struct bpf_mprog_fp {
struct bpf_prog *prog;
};
struct bpf_mprog_cp {
struct bpf_link *link;
};
struct bpf_mprog_entry {
struct bpf_mprog_fp fp_items[BPF_MPROG_MAX];
struct bpf_mprog_bundle *parent;
};
struct bpf_mprog_bundle {
struct bpf_mprog_entry a;
struct bpf_mprog_entry b;
struct bpf_mprog_cp cp_items[BPF_MPROG_MAX];
struct bpf_prog *ref;
atomic64_t revision;
u32 count;
};
struct bpf_tuple {
struct bpf_prog *prog;
struct bpf_link *link;
};
static inline struct bpf_mprog_entry *
bpf_mprog_peer(const struct bpf_mprog_entry *entry)
{
if (entry == &entry->parent->a)
return &entry->parent->b;
else
return &entry->parent->a;
}
static inline void bpf_mprog_bundle_init(struct bpf_mprog_bundle *bundle)
{
BUILD_BUG_ON(sizeof(bundle->a.fp_items[0]) > sizeof(u64));
BUILD_BUG_ON(ARRAY_SIZE(bundle->a.fp_items) !=
ARRAY_SIZE(bundle->cp_items));
memset(bundle, 0, sizeof(*bundle));
atomic64_set(&bundle->revision, 1);
bundle->a.parent = bundle;
bundle->b.parent = bundle;
}
static inline void bpf_mprog_inc(struct bpf_mprog_entry *entry)
{
entry->parent->count++;
}
static inline void bpf_mprog_dec(struct bpf_mprog_entry *entry)
{
entry->parent->count--;
}
static inline int bpf_mprog_max(void)
{
return ARRAY_SIZE(((struct bpf_mprog_entry *)NULL)->fp_items) - 1;
}
static inline int bpf_mprog_total(struct bpf_mprog_entry *entry)
{
int total = entry->parent->count;
WARN_ON_ONCE(total > bpf_mprog_max());
return total;
}
static inline bool bpf_mprog_exists(struct bpf_mprog_entry *entry,
struct bpf_prog *prog)
{
const struct bpf_mprog_fp *fp;
const struct bpf_prog *tmp;
bpf_mprog_foreach_prog(entry, fp, tmp) {
if (tmp == prog)
return true;
}
return false;
}
static inline void bpf_mprog_mark_for_release(struct bpf_mprog_entry *entry,
struct bpf_tuple *tuple)
{
WARN_ON_ONCE(entry->parent->ref);
if (!tuple->link)
entry->parent->ref = tuple->prog;
}
static inline void bpf_mprog_complete_release(struct bpf_mprog_entry *entry)
{
/* In the non-link case prog deletions can only drop the reference
* to the prog after the bpf_mprog_entry got swapped and the
* bpf_mprog ensured that there are no inflight users anymore.
*
* Paired with bpf_mprog_mark_for_release().
*/
if (entry->parent->ref) {
bpf_prog_put(entry->parent->ref);
entry->parent->ref = NULL;
}
}
static inline void bpf_mprog_revision_new(struct bpf_mprog_entry *entry)
{
atomic64_inc(&entry->parent->revision);
}
static inline void bpf_mprog_commit(struct bpf_mprog_entry *entry)
{
bpf_mprog_complete_release(entry);
bpf_mprog_revision_new(entry);
}
static inline u64 bpf_mprog_revision(struct bpf_mprog_entry *entry)
{
return atomic64_read(&entry->parent->revision);
}
static inline void bpf_mprog_entry_copy(struct bpf_mprog_entry *dst,
struct bpf_mprog_entry *src)
{
memcpy(dst->fp_items, src->fp_items, sizeof(src->fp_items));
}
static inline void bpf_mprog_entry_clear(struct bpf_mprog_entry *dst)
{
memset(dst->fp_items, 0, sizeof(dst->fp_items));
}
static inline void bpf_mprog_clear_all(struct bpf_mprog_entry *entry,
struct bpf_mprog_entry **entry_new)
{
struct bpf_mprog_entry *peer;
peer = bpf_mprog_peer(entry);
bpf_mprog_entry_clear(peer);
peer->parent->count = 0;
*entry_new = peer;
}
static inline void bpf_mprog_entry_grow(struct bpf_mprog_entry *entry, int idx)
{
int total = bpf_mprog_total(entry);
memmove(entry->fp_items + idx + 1,
entry->fp_items + idx,
(total - idx) * sizeof(struct bpf_mprog_fp));
memmove(entry->parent->cp_items + idx + 1,
entry->parent->cp_items + idx,
(total - idx) * sizeof(struct bpf_mprog_cp));
}
static inline void bpf_mprog_entry_shrink(struct bpf_mprog_entry *entry, int idx)
{
/* Total array size is needed in this case to enure the NULL
* entry is copied at the end.
*/
int total = ARRAY_SIZE(entry->fp_items);
memmove(entry->fp_items + idx,
entry->fp_items + idx + 1,
(total - idx - 1) * sizeof(struct bpf_mprog_fp));
memmove(entry->parent->cp_items + idx,
entry->parent->cp_items + idx + 1,
(total - idx - 1) * sizeof(struct bpf_mprog_cp));
}
static inline void bpf_mprog_read(struct bpf_mprog_entry *entry, u32 idx,
struct bpf_mprog_fp **fp,
struct bpf_mprog_cp **cp)
{
*fp = &entry->fp_items[idx];
*cp = &entry->parent->cp_items[idx];
}
static inline void bpf_mprog_write(struct bpf_mprog_fp *fp,
struct bpf_mprog_cp *cp,
struct bpf_tuple *tuple)
{
WRITE_ONCE(fp->prog, tuple->prog);
cp->link = tuple->link;
}
int bpf_mprog_attach(struct bpf_mprog_entry *entry,
struct bpf_mprog_entry **entry_new,
struct bpf_prog *prog_new, struct bpf_link *link,
struct bpf_prog *prog_old,
u32 flags, u32 id_or_fd, u64 revision);
int bpf_mprog_detach(struct bpf_mprog_entry *entry,
struct bpf_mprog_entry **entry_new,
struct bpf_prog *prog, struct bpf_link *link,
u32 flags, u32 id_or_fd, u64 revision);
int bpf_mprog_query(const union bpf_attr *attr, union bpf_attr __user *uattr,
struct bpf_mprog_entry *entry);
static inline bool bpf_mprog_supported(enum bpf_prog_type type)
{
switch (type) {
case BPF_PROG_TYPE_SCHED_CLS:
return true;
default:
return false;
}
}
#endif /* __BPF_MPROG_H */