Commit 2057c92b authored by Yonghong Song's avatar Yonghong Song Committed by Alexei Starovoitov
Browse files

bpf: Support bpf tracing/iter programs for BPF_LINK_UPDATE 



Added BPF_LINK_UPDATE support for tracing/iter programs.
This way, a file based bpf iterator, which holds a reference
to the link, can have its bpf program updated without
creating new files.

Signed-off-by: default avatarYonghong Song <yhs@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarAndrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200509175902.2475262-1-yhs@fb.com
parent de4e05ca

kernel/bpf/bpf_iter.c

+31 −0
Original line number Diff line number Diff line
@@ -23,6 +23,9 @@ struct bpf_iter_link { 
static struct list_head targets = LIST_HEAD_INIT(targets);

static DEFINE_MUTEX(targets_mutex);



/* protect bpf_iter_link changes */

static DEFINE_MUTEX(link_mutex);



int bpf_iter_reg_target(struct bpf_iter_reg *reg_info)

{

	struct bpf_iter_target_info *tinfo;
@@ -111,9 +114,37 @@ static void bpf_iter_link_dealloc(struct bpf_link *link) 
	kfree(iter_link);

}



static int bpf_iter_link_replace(struct bpf_link *link,

				 struct bpf_prog *new_prog,

				 struct bpf_prog *old_prog)

{

	int ret = 0;



	mutex_lock(&link_mutex);

	if (old_prog && link->prog != old_prog) {

		ret = -EPERM;

		goto out_unlock;

	}



	if (link->prog->type != new_prog->type ||

	    link->prog->expected_attach_type != new_prog->expected_attach_type ||

	    link->prog->aux->attach_btf_id != new_prog->aux->attach_btf_id) {

		ret = -EINVAL;

		goto out_unlock;

	}



	old_prog = xchg(&link->prog, new_prog);

	bpf_prog_put(old_prog);



out_unlock:

	mutex_unlock(&link_mutex);

	return ret;

}



static const struct bpf_link_ops bpf_iter_link_lops = {

	.release = bpf_iter_link_release,

	.dealloc = bpf_iter_link_dealloc,

	.update_prog = bpf_iter_link_replace,

};



int bpf_iter_link_attach(const union bpf_attr *attr, struct bpf_prog *prog)

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