bpf: add is_async_callback_calling_insn() helper

Currently we have a special case for BPF_FUNC_timer_set_callback,
let's introduce a helper we can extend for the kfunc that will come in
a later patch

Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>
Link: https://lore.kernel.org/r/20240221-hid-bpf-sleepable-v3-3-1fb378ca6301@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Author: Benjamin Tissoires

kernel/bpf/verifier.c

@@ -528,6 +528,11 @@ static bool is_sync_callback_calling_insn(struct bpf_insn *insn)
 	       (bpf_pseudo_kfunc_call(insn) && is_sync_callback_calling_kfunc(insn->imm));
 }
 
+static bool is_async_callback_calling_insn(struct bpf_insn *insn)
+{
+	return bpf_helper_call(insn) && is_async_callback_calling_function(insn->imm);
+}
+
 static bool is_storage_get_function(enum bpf_func_id func_id)
 {
 	return func_id == BPF_FUNC_sk_storage_get ||
@@ -9445,9 +9450,7 @@ static int push_callback_call(struct bpf_verifier_env *env, struct bpf_insn *ins
 		return -EFAULT;
 	}
 
-	if (insn->code == (BPF_JMP | BPF_CALL) &&
-	    insn->src_reg == 0 &&
-	    insn->imm == BPF_FUNC_timer_set_callback) {
+	if (is_async_callback_calling_insn(insn)) {
 		struct bpf_verifier_state *async_cb;
 
 		/* there is no real recursion here. timer callbacks are async */
@@ -15588,7 +15591,7 @@ static int visit_insn(int t, struct bpf_verifier_env *env)
 		return DONE_EXPLORING;
 
 	case BPF_CALL:
-		if (insn->src_reg == 0 && insn->imm == BPF_FUNC_timer_set_callback)
+		if (is_async_callback_calling_insn(insn))
 			/* Mark this call insn as a prune point to trigger
 			 * is_state_visited() check before call itself is
 			 * processed by __check_func_call(). Otherwise new