linux-kernel - [PATCH RFC bpf-next 6/8] bpf: remove one special case of is_bpf_wq_set_callback_impl

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Date: Tue, 07 May 2024 15:19:34 +0200
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>, Mykola Lysenko <mykolal@...com>, 
 Shuah Khan <shuah@...nel.org>
Cc: bpf@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-kselftest@...r.kernel.org, Benjamin Tissoires <bentiss@...nel.org>
Subject: [PATCH RFC bpf-next 6/8] bpf: remove one special case of
 is_bpf_wq_set_callback_impl_kfunc

It looks like the generic implementation based on __s_async suffix works
well enough. So let's use it.

Note:
- currently we lose the return value range
- the second argument is not of type PTR_TO_MAP_KEY

Signed-off-by: Benjamin Tissoires <bentiss@...nel.org>

---

This is an RFC, and is not meant to be fully reviewed/applied as it is.
I'm posting this to show what I wanted to explain in
https://lore.kernel.org/bpf/mhkzkf4e23uvljtmwizwcxyuyat2tmfxn33xb4t7waafgmsa66@mcrzpj3b6ssx/
---
 kernel/bpf/verifier.c | 27 ++++-----------------------
 1 file changed, 4 insertions(+), 23 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index cc4dab81b306..6fba9e2caa83 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -511,7 +511,6 @@ static bool is_dynptr_ref_function(enum bpf_func_id func_id)
 }
 
 static bool is_sync_callback_calling_kfunc(u32 btf_id);
-static bool is_async_callback_calling_kfunc(u32 btf_id);
 static bool is_callback_calling_kfunc(u32 btf_id);
 static bool is_bpf_throw_kfunc(struct bpf_insn *insn);
 
@@ -544,8 +543,7 @@ static bool is_sync_callback_calling_insn(struct bpf_insn *insn)
 
 static bool is_async_callback_calling_insn(struct bpf_insn *insn)
 {
-	return (bpf_helper_call(insn) && is_async_callback_calling_function(insn->imm)) ||
-	       (bpf_pseudo_kfunc_call(insn) && is_async_callback_calling_kfunc(insn->imm));
+	return bpf_helper_call(insn) && is_async_callback_calling_function(insn->imm);
 }
 
 static bool is_may_goto_insn(struct bpf_insn *insn)
@@ -9560,15 +9558,14 @@ static int push_callback_call(struct bpf_verifier_env *env, struct bpf_insn *ins
 		return -EFAULT;
 	}
 
-	if (is_async_callback_calling_insn(insn) || (kfunc_meta && kfunc_meta->async_cb.enabled)) {
+	if (kfunc_meta && kfunc_meta->async_cb.enabled) {
 		struct bpf_verifier_state *async_cb;
 
 		/* there is no real recursion here. timer and workqueue callbacks are async */
 		env->subprog_info[subprog].is_async_cb = true;
 		async_cb = push_async_cb(env, env->subprog_info[subprog].start,
 					 insn_idx, subprog,
-					 (is_bpf_wq_set_callback_impl_kfunc(insn->imm) ||
-					  (kfunc_meta && kfunc_meta->async_cb.sleepable)));
+					 kfunc_meta && kfunc_meta->async_cb.sleepable);
 		if (!async_cb)
 			return -EFAULT;
 		callee = async_cb->frame[0];
@@ -11534,11 +11531,6 @@ static bool is_sync_callback_calling_kfunc(u32 btf_id)
 	return btf_id == special_kfunc_list[KF_bpf_rbtree_add_impl];
 }
 
-static bool is_async_callback_calling_kfunc(u32 btf_id)
-{
-	return btf_id == special_kfunc_list[KF_bpf_wq_set_callback_impl];
-}
-
 static bool is_bpf_throw_kfunc(struct bpf_insn *insn)
 {
 	return bpf_pseudo_kfunc_call(insn) && insn->off == 0 &&
@@ -11552,8 +11544,7 @@ static bool is_bpf_wq_set_callback_impl_kfunc(u32 btf_id)
 
 static bool is_callback_calling_kfunc(u32 btf_id)
 {
-	return is_sync_callback_calling_kfunc(btf_id) ||
-	       is_async_callback_calling_kfunc(btf_id);
+	return is_sync_callback_calling_kfunc(btf_id);
 }
 
 static bool is_rbtree_lock_required_kfunc(u32 btf_id)
@@ -12465,16 +12456,6 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 		}
 	}
 
-	if (is_bpf_wq_set_callback_impl_kfunc(meta.func_id)) {
-		err = push_callback_call(env, insn, insn_idx, meta.subprogno,
-					 set_timer_callback_state, &meta);
-		if (err) {
-			verbose(env, "kfunc %s#%d failed callback verification\n",
-				func_name, meta.func_id);
-			return err;
-		}
-	}
-
 	if (meta.async_cb.enabled) {
 		err = push_callback_call(env, insn, insn_idx, meta.subprogno,
 					 set_generic_callback_state, &meta);

-- 
2.44.0