bpf: refactor bpf_helper_changes_pkt_data to use helper number

Use BPF helper number instead of function pointer in
bpf_helper_changes_pkt_data(). This would simplify usage of this
function in verifier.c:check_cfg() (in a follow-up patch),
where only helper number is easily available and there is no real need
to lookup helper proto.

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20241210041100.1898468-3-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Author: eddyz87

include/linux/filter.h

@@ -1122,7 +1122,7 @@ bool bpf_jit_supports_insn(struct bpf_insn *insn, bool in_arena);
 bool bpf_jit_supports_private_stack(void);
 u64 bpf_arch_uaddress_limit(void);
 void arch_bpf_stack_walk(bool (*consume_fn)(void *cookie, u64 ip, u64 sp, u64 bp), void *cookie);
-bool bpf_helper_changes_pkt_data(void *func);
+bool bpf_helper_changes_pkt_data(enum bpf_func_id func_id);
 
 static inline bool bpf_dump_raw_ok(const struct cred *cred)
 {

kernel/bpf/core.c

@@ -2936,7 +2936,7 @@ void __weak bpf_jit_compile(struct bpf_prog *prog)
 {
 }
 
-bool __weak bpf_helper_changes_pkt_data(void *func)
+bool __weak bpf_helper_changes_pkt_data(enum bpf_func_id func_id)
 {
 	return false;
 }

kernel/bpf/verifier.c

@@ -10728,7 +10728,7 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
 	}
 
 	/* With LD_ABS/IND some JITs save/restore skb from r1. */
-	changes_data = bpf_helper_changes_pkt_data(fn->func);
+	changes_data = bpf_helper_changes_pkt_data(func_id);
 	if (changes_data && fn->arg1_type != ARG_PTR_TO_CTX) {
 		verbose(env, "kernel subsystem misconfigured func %s#%d: r1 != ctx\n",
 			func_id_name(func_id), func_id);

net/core/filter.c

@@ -7899,42 +7899,35 @@ static const struct bpf_func_proto bpf_tcp_raw_check_syncookie_ipv6_proto = {
 
 #endif /* CONFIG_INET */
 
-bool bpf_helper_changes_pkt_data(void *func)
-{
-	if (func == bpf_skb_vlan_push ||
-	    func == bpf_skb_vlan_pop ||
-	    func == bpf_skb_store_bytes ||
-	    func == bpf_skb_change_proto ||
-	    func == bpf_skb_change_head ||
-	    func == sk_skb_change_head ||
-	    func == bpf_skb_change_tail ||
-	    func == sk_skb_change_tail ||
-	    func == bpf_skb_adjust_room ||
-	    func == sk_skb_adjust_room ||
-	    func == bpf_skb_pull_data ||
-	    func == sk_skb_pull_data ||
-	    func == bpf_clone_redirect ||
-	    func == bpf_l3_csum_replace ||
-	    func == bpf_l4_csum_replace ||
-	    func == bpf_xdp_adjust_head ||
-	    func == bpf_xdp_adjust_meta ||
-	    func == bpf_msg_pull_data ||
-	    func == bpf_msg_push_data ||
-	    func == bpf_msg_pop_data ||
-	    func == bpf_xdp_adjust_tail ||
-#if IS_ENABLED(CONFIG_IPV6_SEG6_BPF)
-	    func == bpf_lwt_seg6_store_bytes ||
-	    func == bpf_lwt_seg6_adjust_srh ||
-	    func == bpf_lwt_seg6_action ||
-#endif
-#ifdef CONFIG_INET
-	    func == bpf_sock_ops_store_hdr_opt ||
-#endif
-	    func == bpf_lwt_in_push_encap ||
-	    func == bpf_lwt_xmit_push_encap)
+bool bpf_helper_changes_pkt_data(enum bpf_func_id func_id)
+{
+	switch (func_id) {
+	case BPF_FUNC_clone_redirect:
+	case BPF_FUNC_l3_csum_replace:
+	case BPF_FUNC_l4_csum_replace:
+	case BPF_FUNC_lwt_push_encap:
+	case BPF_FUNC_lwt_seg6_action:
+	case BPF_FUNC_lwt_seg6_adjust_srh:
+	case BPF_FUNC_lwt_seg6_store_bytes:
+	case BPF_FUNC_msg_pop_data:
+	case BPF_FUNC_msg_pull_data:
+	case BPF_FUNC_msg_push_data:
+	case BPF_FUNC_skb_adjust_room:
+	case BPF_FUNC_skb_change_head:
+	case BPF_FUNC_skb_change_proto:
+	case BPF_FUNC_skb_change_tail:
+	case BPF_FUNC_skb_pull_data:
+	case BPF_FUNC_skb_store_bytes:
+	case BPF_FUNC_skb_vlan_pop:
+	case BPF_FUNC_skb_vlan_push:
+	case BPF_FUNC_store_hdr_opt:
+	case BPF_FUNC_xdp_adjust_head:
+	case BPF_FUNC_xdp_adjust_meta:
+	case BPF_FUNC_xdp_adjust_tail:
 		return true;
-
-	return false;
+	default:
+		return false;
+	}
 }
 
 const struct bpf_func_proto bpf_event_output_data_proto __weak;