bpf: Tidy verifier bug message

Yonghong noticed that error messages for potential verifier bugs often
have a '(1)' at the end. This is happening because verifier_bug_if(cond,
env, fmt, args...) prints "(" #cond ")\n" as part of the message and
verifier_bug() is defined as:

  #define verifier_bug(env, fmt, args...) verifier_bug_if(1, env, fmt, ##args)

Hence, verifier_bug() always ends up displaying '(1)'. This small patch
fixes it by having verifier_bug_if conditionally call verifier_bug
instead of the other way around.

Fixes: 1cb0f56 ("bpf: WARN_ONCE on verifier bugs")
Reported-by: Yonghong Song <[email protected]>
Signed-off-by: Paul Chaignon <[email protected]>
Signed-off-by: Andrii Nakryiko <[email protected]>
Tested-by: Eduard Zingerman <[email protected]>
Acked-by: Yonghong Song <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]

Author: pchaigno

include/linux/bpf_verifier.h

@@ -875,13 +875,15 @@ __printf(3, 4) void verbose_linfo(struct bpf_verifier_env *env,
 #define verifier_bug_if(cond, env, fmt, args...)						\
 	({											\
 		bool __cond = (cond);								\
-		if (unlikely(__cond)) {								\
-			BPF_WARN_ONCE(1, "verifier bug: " fmt "(" #cond ")\n", ##args);		\
-			bpf_log(&env->log, "verifier bug: " fmt "(" #cond ")\n", ##args);	\
-		}										\
+		if (unlikely(__cond))								\
+			verifier_bug(env, fmt " (" #cond ")", ##args);				\
 		(__cond);									\
 	})
-#define verifier_bug(env, fmt, args...) verifier_bug_if(1, env, fmt, ##args)
+#define verifier_bug(env, fmt, args...)								\
+	({											\
+		BPF_WARN_ONCE(1, "verifier bug: " fmt "\n", ##args);				\
+		bpf_log(&env->log, "verifier bug: " fmt "\n", ##args);				\
+	})
 
 static inline struct bpf_func_state *cur_func(struct bpf_verifier_env *env)
 {