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 <[email protected]>

---

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


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