[RFC PATCH bpf-next 2/7] bpf: Enable BPF_LINK_UPDATE for freplace links

[Jordan Rife]

Implement program update logic for freplace links.

Signed-off-by: Jordan Rife <jordan at jrife.io>
---
 kernel/bpf/trampoline.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index 010bcba0db65..0b6a5433dd42 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -614,6 +614,21 @@ static int __bpf_trampoline_update_prog(struct bpf_tramp_link *link,
 					struct bpf_prog *new_prog,
 					struct bpf_trampoline *tr)
 {
+	enum bpf_tramp_prog_type kind;
+	int err = 0;
+
+	kind = bpf_attach_type_to_tramp(link->link.prog);
+	if (kind == BPF_TRAMP_REPLACE) {
+		WARN_ON_ONCE(!tr->extension_prog);
+		err = bpf_arch_text_poke(tr->func.addr, BPF_MOD_JUMP,
+					 tr->extension_prog->bpf_func,
+					 new_prog->bpf_func);
+		if (err)
+			return err;
+		tr->extension_prog = new_prog;
+		return 0;
+	}
+
 	return -ENOTSUPP;
 }
 
-- 
2.43.0