bpf: Add bpf_ksym_add/del functions

Separating /proc/kallsyms add/del code and adding bpf_ksym_add/del
functions for that.

Moving bpf_prog_ksym_node_add/del functions to __bpf_ksym_add/del
and changing their argument to 'struct bpf_ksym' object. This way
we can call them for other bpf objects types like trampoline and
dispatcher.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200312195610.346362-10-jolsa@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

include/linux/bpf.h

@@ -584,6 +584,9 @@ struct bpf_image {
 #define BPF_IMAGE_SIZE (PAGE_SIZE - sizeof(struct bpf_image))
 bool is_bpf_image_address(unsigned long address);
 void *bpf_image_alloc(void);
+/* Called only from JIT-enabled code, so there's no need for stubs. */
+void bpf_ksym_add(struct bpf_ksym *ksym);
+void bpf_ksym_del(struct bpf_ksym *ksym);
 #else
 static inline struct bpf_trampoline *bpf_trampoline_lookup(u64 key)
 {

kernel/bpf/core.c

@@ -607,20 +607,29 @@ static DEFINE_SPINLOCK(bpf_lock);
 static LIST_HEAD(bpf_kallsyms);
 static struct latch_tree_root bpf_tree __cacheline_aligned;
 
-static void bpf_prog_ksym_node_add(struct bpf_prog_aux *aux)
+void bpf_ksym_add(struct bpf_ksym *ksym)
 {
-	WARN_ON_ONCE(!list_empty(&aux->ksym.lnode));
-	list_add_tail_rcu(&aux->ksym.lnode, &bpf_kallsyms);
-	latch_tree_insert(&aux->ksym.tnode, &bpf_tree, &bpf_tree_ops);
+	spin_lock_bh(&bpf_lock);
+	WARN_ON_ONCE(!list_empty(&ksym->lnode));
+	list_add_tail_rcu(&ksym->lnode, &bpf_kallsyms);
+	latch_tree_insert(&ksym->tnode, &bpf_tree, &bpf_tree_ops);
+	spin_unlock_bh(&bpf_lock);
 }
 
-static void bpf_prog_ksym_node_del(struct bpf_prog_aux *aux)
+static void __bpf_ksym_del(struct bpf_ksym *ksym)
 {
-	if (list_empty(&aux->ksym.lnode))
+	if (list_empty(&ksym->lnode))
 		return;
 
-	latch_tree_erase(&aux->ksym.tnode, &bpf_tree, &bpf_tree_ops);
-	list_del_rcu(&aux->ksym.lnode);
+	latch_tree_erase(&ksym->tnode, &bpf_tree, &bpf_tree_ops);
+	list_del_rcu(&ksym->lnode);
+}
+
+void bpf_ksym_del(struct bpf_ksym *ksym)
+{
+	spin_lock_bh(&bpf_lock);
+	__bpf_ksym_del(ksym);
+	spin_unlock_bh(&bpf_lock);
 }
 
 static bool bpf_prog_kallsyms_candidate(const struct bpf_prog *fp)
@@ -644,9 +653,7 @@ void bpf_prog_kallsyms_add(struct bpf_prog *fp)
 	bpf_prog_ksym_set_name(fp);
 	fp->aux->ksym.prog = true;
 
-	spin_lock_bh(&bpf_lock);
-	bpf_prog_ksym_node_add(fp->aux);
-	spin_unlock_bh(&bpf_lock);
+	bpf_ksym_add(&fp->aux->ksym);
 }
 
 void bpf_prog_kallsyms_del(struct bpf_prog *fp)
@@ -654,9 +661,7 @@ void bpf_prog_kallsyms_del(struct bpf_prog *fp)
 	if (!bpf_prog_kallsyms_candidate(fp))
 		return;
 
-	spin_lock_bh(&bpf_lock);
-	bpf_prog_ksym_node_del(fp->aux);
-	spin_unlock_bh(&bpf_lock);
+	bpf_ksym_del(&fp->aux->ksym);
 }
 
 static struct bpf_ksym *bpf_ksym_find(unsigned long addr)