kernel

linux-6.8.1/include/linux/bpf_mprog.h

@@ -0,0 +1,343 @@
+/* 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 */