linux-kernel - [PATCH RFC bpf-next v3 03/16] bpf/verifier: add is_async_callback_calling

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Date: Wed, 21 Feb 2024 17:25:19 +0100
From: Benjamin Tissoires <bentiss@...nel.org>
To: Alexei Starovoitov <ast@...nel.org>, 
 Daniel Borkmann <daniel@...earbox.net>, 
 John Fastabend <john.fastabend@...il.com>, 
 Andrii Nakryiko <andrii@...nel.org>, 
 Martin KaFai Lau <martin.lau@...ux.dev>, 
 Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
 Yonghong Song <yonghong.song@...ux.dev>, KP Singh <kpsingh@...nel.org>, 
 Stanislav Fomichev <sdf@...gle.com>, Hao Luo <haoluo@...gle.com>, 
 Jiri Olsa <jolsa@...nel.org>, Jiri Kosina <jikos@...nel.org>, 
 Benjamin Tissoires <benjamin.tissoires@...hat.com>, 
 Jonathan Corbet <corbet@....net>, Shuah Khan <shuah@...nel.org>
Cc: bpf@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-input@...r.kernel.org, linux-doc@...r.kernel.org, 
 linux-kselftest@...r.kernel.org, Benjamin Tissoires <bentiss@...nel.org>
Subject: [PATCH RFC bpf-next v3 03/16] bpf/verifier: 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@...nel.org>

---

new in v3
---
 kernel/bpf/verifier.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 7a4b19bea2ac..f81c799b2c80 100644
--- a/kernel/bpf/verifier.c
+++ b/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

-- 
2.43.0