bpf: Remove unnecessary OUTPUT_SKB macro

When call set_skb_btf() or set_shinfo_btf(), these functions are
protected by constant CFG.

Then, while loading kprobe_pwru into kernel, if no
--output-skb/--output-skb-shared-info, set_skb_btf()/set_shinfo_btf()
won't be verified. Next, these unreachable code will be eliminated by
verifier.

Signed-off-by: Leon Hwang <hffilwlqm@gmail.com>

bpf/kprobe_pwru.c

@@ -162,7 +162,6 @@ struct {
 	__uint(value_size, MAX_STACK_DEPTH * sizeof(u64));
 } print_stack_map SEC(".maps");
 
-#ifdef OUTPUT_SKB
 struct print_skb_value {
 	u32 len;
 	char str[PRINT_SKB_STR_SIZE];
@@ -195,7 +194,6 @@ struct {
 	__type(key, u64);
 	__type(value, struct print_shinfo_value);
 } print_shinfo_map SEC(".maps");
-#endif
 
 static __always_inline u32
 get_netns(struct sk_buff *skb) {
@@ -342,7 +340,6 @@ sync_fetch_and_add(void *id_map) {
 
 static __always_inline void
 set_skb_btf(struct sk_buff *skb, u64 *event_id) {
-#ifdef OUTPUT_SKB
 	static struct btf_ptr p = {};
 	static struct print_skb_value v = {};
 	u64 id;
@@ -357,12 +354,10 @@ set_skb_btf(struct sk_buff *skb, u64 *event_id) {
 	}
 
 	bpf_map_update_elem(&print_skb_map, event_id, &v, BPF_ANY);
-#endif
 }
 
 static __always_inline void
 set_shinfo_btf(struct sk_buff *skb, u64 *event_id) {
-#ifdef OUTPUT_SKB
 	struct skb_shared_info *shinfo;
 	static struct btf_ptr p = {};
 	static struct print_shinfo_value v = {};
@@ -391,7 +386,6 @@ set_shinfo_btf(struct sk_buff *skb, u64 *event_id) {
 	}
 
 	bpf_map_update_elem(&print_shinfo_map, event_id, &v, BPF_ANY);
-#endif
 }
 
 static __always_inline u64

build.go

@@ -2,9 +2,7 @@
 // Copyright (C) 2021 Authors of Cilium */
 
 //go:generate sh -c "echo Generating for $TARGET_GOARCH"
-//go:generate go run github.com/cilium/ebpf/cmd/bpf2go -target $TARGET_GOARCH -cc clang -no-strip KProbePWRU ./bpf/kprobe_pwru.c -- -DOUTPUT_SKB -I./bpf/headers -Wno-address-of-packed-member
-//go:generate go run github.com/cilium/ebpf/cmd/bpf2go -target $TARGET_GOARCH -cc clang -no-strip KProbeMultiPWRU ./bpf/kprobe_pwru.c -- -DOUTPUT_SKB -DHAS_KPROBE_MULTI -I./bpf/headers -Wno-address-of-packed-member
-//go:generate go run github.com/cilium/ebpf/cmd/bpf2go -target $TARGET_GOARCH -cc clang -no-strip KProbePWRUWithoutOutputSKB ./bpf/kprobe_pwru.c -- -I./bpf/headers -Wno-address-of-packed-member
-//go:generate go run github.com/cilium/ebpf/cmd/bpf2go -target $TARGET_GOARCH -cc clang -no-strip KProbeMultiPWRUWithoutOutputSKB ./bpf/kprobe_pwru.c -- -D HAS_KPROBE_MULTI -I./bpf/headers -Wno-address-of-packed-member
+//go:generate go run github.com/cilium/ebpf/cmd/bpf2go -target $TARGET_GOARCH -cc clang -no-strip KProbePWRU ./bpf/kprobe_pwru.c -- -I./bpf/headers -Wno-address-of-packed-member
+//go:generate go run github.com/cilium/ebpf/cmd/bpf2go -target $TARGET_GOARCH -cc clang -no-strip KProbeMultiPWRU ./bpf/kprobe_pwru.c -- -DHAS_KPROBE_MULTI -I./bpf/headers -Wno-address-of-packed-member
 
 package main

main.go

@@ -119,12 +119,8 @@ func main() {
 	switch {
 	case (flags.OutputSkb || flags.OutputShinfo) && useKprobeMulti:
 		bpfSpec, err = LoadKProbeMultiPWRU()
-	case flags.OutputSkb || flags.OutputShinfo:
-		bpfSpec, err = LoadKProbePWRU()
-	case useKprobeMulti:
-		bpfSpec, err = LoadKProbeMultiPWRUWithoutOutputSKB()
 	default:
-		bpfSpec, err = LoadKProbePWRUWithoutOutputSKB()
+		bpfSpec, err = LoadKProbePWRU()
 	}
 	if err != nil {
 		log.Fatalf("Failed to load bpf spec: %v", err)