Currently we don't allow re-attaching of trampolines. Once
it's detached, it can't be re-attach even when the program
is still loaded.
Adding the possibility to re-attach the loaded tracing
kernel program.
Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
---
kernel/bpf/syscall.c | 25 +++++++++++++++++++------
kernel/bpf/trampoline.c | 2 +-
2 files changed, 20 insertions(+), 7 deletions(-)
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 9603de81811a..e14926b2e95a 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2645,14 +2645,27 @@ static int bpf_tracing_prog_attach(struct bpf_prog *prog,
* target_btf_id using the link_create API.
*
* - if tgt_prog == NULL when this function was called using the old
- * raw_tracepoint_open API, and we need a target from prog->aux
- *
- * The combination of no saved target in prog->aux, and no target
- * specified on load is illegal, and we reject that here.
+ * raw_tracepoint_open API, and we need a target from prog->aux
+ *
+ * The combination of no saved target in prog->aux, and no target
+ * specified on is legal only for tracing programs re-attach, rest
+ * is illegal, and we reject that here.
*/
if (!prog->aux->dst_trampoline && !tgt_prog) {
- err = -ENOENT;
- goto out_unlock;
+ /*
+ * Allow re-attach for tracing programs, if it's currently
+ * linked, bpf_trampoline_link_prog will fail.
+ */
+ if (prog->type != BPF_PROG_TYPE_TRACING) {
+ err = -ENOENT;
+ goto out_unlock;
+ }
+ if (!prog->aux->attach_btf) {
+ err = -EINVAL;
+ goto out_unlock;
+ }
+ btf_id = prog->aux->attach_btf_id;
+ key = bpf_trampoline_compute_key(NULL, prog->aux->attach_btf, btf_id);
}
if (!prog->aux->dst_trampoline ||
diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index 4aa8b52adf25..0d937c63fc22 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -467,7 +467,7 @@ int bpf_trampoline_unlink_prog(struct bpf_prog *prog, struct bpf_trampoline *tr)
tr->extension_prog = NULL;
goto out;
}
- hlist_del(&prog->aux->tramp_hlist);
+ hlist_del_init(&prog->aux->tramp_hlist);
tr->progs_cnt[kind]--;
err = bpf_trampoline_update(tr);
out:
--
2.30.2
