On Sat, 24 Mar 2018 00:13:28 +0100
Daniel Borkmann <daniel@xxxxxxxxxxxxx> 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
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