Subject: [PATCH 15/18] bpf: Sort bpf kallsyms symbols

From: Jiri Olsa <[email-masked]>
Date: Sun, 16 Feb 2020 20:30:02 +0100

Currently we don't sort bpf_kallsyms and display symbols
in proc/kallsyms as they come in via __bpf_ksym_add.

Using the latch tree to get the next bpf_ksym object
and insert the new symbol ahead of it.

Signed-off-by: Jiri Olsa <[email-masked]>
---
 kernel/bpf/core.c | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 2f857bbfe05c..fa814179730c 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -651,9 +651,28 @@ static struct latch_tree_root bpf_progs_tree __cacheline_aligned;
 
 static void __bpf_ksym_add(struct bpf_ksym *ksym)
 {
+	struct list_head *head = &bpf_kallsyms;
+	struct rb_node *next;
+
 	WARN_ON_ONCE(!list_empty(&ksym->lnode));
-	list_add_tail_rcu(&ksym->lnode, &bpf_kallsyms);
 	latch_tree_insert(&ksym->tnode, &bpf_ksym_tree, &bpf_ksym_tree_ops);
+
+	/*
+	 * Add ksym into bpf_kallsyms in ordered position,
+	 * which is prepared for us by latch tree addition.
+	 *
+	 * Find out the next symbol and insert ksym right
+	 * ahead of it. If ksym is the last one, just tail
+	 * add to the bpf_kallsyms.
+	 */
+	next = rb_next(&ksym->tnode.node[0]);
+	if (next) {
+		struct bpf_ksym *ptr;
+
+		ptr = container_of(next, struct bpf_ksym, tnode.node[0]);
+		head = &ptr->lnode;
+	}
+	list_add_tail_rcu(&ksym->lnode, head);
 }
 
 void bpf_ksym_add(struct bpf_ksym *ksym)
-- 
2.24.1