On Sun, Feb 16, 2020 at 08:30:02PM +0100, Jiri Olsa wrote:
> 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 <jolsa@xxxxxxxxxx>
> ---
> 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);
what is the motivation for sorting? do you want perf and other user space
to depend on it? Or purely aesthetics?
