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Date: Fri, 23 Mar 2018 21:39:36 -0400
From: Steven Rostedt <rostedt@goodmis.org>
To: Daniel Borkmann <daniel@iogearbox.net>
Cc: Alexei Starovoitov <ast@fb.com>, davem@davemloft.net,
        torvalds@linux-foundation.org, peterz@infradead.org,
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Subject: Re: [PATCH v2 bpf-next 5/8] bpf: introduce BPF_RAW_TRACEPOINT
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On Sat, 24 Mar 2018 00:13:28 +0100
Daniel Borkmann <daniel@iogearbox.net> wrote:

> #define UNPACK(...)			__VA_ARGS__
> #define REPEAT_1(FN, DL, X, ...)	FN(X)
> #define REPEAT_2(FN, DL, X, ...)	FN(X) UNPACK DL REPEAT_1(FN, DL, __VA_ARGS__)
> #define REPEAT_3(FN, DL, X, ...)	FN(X) UNPACK DL REPEAT_2(FN, DL, __VA_ARGS__)
> #define REPEAT_4(FN, DL, X, ...)	FN(X) UNPACK DL REPEAT_3(FN, DL, __VA_ARGS__)
> #define REPEAT_5(FN, DL, X, ...)	FN(X) UNPACK DL REPEAT_4(FN, DL, __VA_ARGS__)
> #define REPEAT_6(FN, DL, X, ...)	FN(X) UNPACK DL REPEAT_5(FN, DL, __VA_ARGS__)
> #define REPEAT_7(FN, DL, X, ...)	FN(X) UNPACK DL REPEAT_6(FN, DL, __VA_ARGS__)
> #define REPEAT_8(FN, DL, X, ...)	FN(X) UNPACK DL REPEAT_7(FN, DL, __VA_ARGS__)
> #define REPEAT_9(FN, DL, X, ...)	FN(X) UNPACK DL REPEAT_8(FN, DL, __VA_ARGS__)
> #define REPEAT(X, FN, DL, ...)		REPEAT_##X(FN, DL, __VA_ARGS__)
> 
> #define SARG(X)		u64 arg##X
> #define COPY(X)		args[X] = arg##X
> 
> #define __DL_COM	(,)
> #define __DL_SEM	(;)
> 
> #define __SEQ		0, 1, 2, 3, 4, 5, 6, 7, 8, 9
> 
> #define BPF_TRACE_DECL_x(x)						\
> 	void bpf_trace_run##x(struct bpf_prog *prog,			\
> 			      REPEAT(x, SARG, __DL_COM, __SEQ))
> #define BPF_TRACE_DEFN_x(x)						\
> 	void bpf_trace_run##x(struct bpf_prog *prog,			\
> 			      REPEAT(x, SARG, __DL_COM, __SEQ))		\
> 	{								\
> 		u64 args[x];						\
> 		REPEAT(x, COPY, __DL_SEM, __SEQ);			\
> 		__bpf_trace_run(prog, args);				\
> 	}								\
> 	EXPORT_SYMBOL_GPL(bpf_trace_run##x)
> 
> So doing a ...
> 
> BPF_TRACE_DECL_x(5);
> BPF_TRACE_DEFN_x(5);
> 
> ... will generate in kernel/trace/bpf_trace.i:
> 
> void bpf_foo_trace_run5(struct bpf_prog *prog, u64 arg0 , u64 arg1 , u64 arg2 , u64 arg3 , u64 arg4);
> void bpf_foo_trace_run5(struct bpf_prog *prog, u64 arg0 , u64 arg1 , u64 arg2 , u64 arg3 , u64 arg4)
> {
> 	u64 args[5];
> 	args[0] = arg0 ;
> 	args[1] = arg1 ;
> 	args[2] = arg2 ;
> 	args[3] = arg3 ;
> 	args[4] = arg4;
> 	__bpf_trace_run(prog, args);
> } [...]
> 
> Meaning, the EVALx() macros could be removed from there, too. Potentially, the
> REPEAT() macro could sit in its own include/linux/ header for others to reuse
> or such.

And people think my macro magic in include/trace/ftrace_event.h is
funky. Now I know who stole my MACRO MAGIC HAT.

-- Steve