On Fri, Oct 4, 2019 at 10:05 PM Alexei Starovoitov <ast@xxxxxxxxxx> wrote:
>
> When pahole converts dwarf to btf it emits only used types.
> Wrap existing bpf helper functions into typedef and use it in
> typecast to make gcc emits this type into dwarf.
> Then pahole will convert it to btf.
> The "btf_#name_of_helper" types will be used to figure out
> types of arguments of bpf helpers.
> The generate code before and after is the same.
> Only dwarf and btf are different.
>
> Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
> ---
It's amazing this works :)
Acked-by: Andrii Nakryiko <andriin@xxxxxx>
> include/linux/filter.h | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/filter.h b/include/linux/filter.h
> index 2ce57645f3cd..d3d51d7aff2c 100644
> --- a/include/linux/filter.h
> +++ b/include/linux/filter.h
> @@ -464,10 +464,11 @@ static inline bool insn_is_zext(const struct bpf_insn *insn)
> #define BPF_CALL_x(x, name, ...) \
> static __always_inline \
> u64 ____##name(__BPF_MAP(x, __BPF_DECL_ARGS, __BPF_V, __VA_ARGS__)); \
> + typedef u64 (*btf_##name)(__BPF_MAP(x, __BPF_DECL_ARGS, __BPF_V, __VA_ARGS__)); \
> u64 name(__BPF_REG(x, __BPF_DECL_REGS, __BPF_N, __VA_ARGS__)); \
> u64 name(__BPF_REG(x, __BPF_DECL_REGS, __BPF_N, __VA_ARGS__)) \
> { \
> - return ____##name(__BPF_MAP(x,__BPF_CAST,__BPF_N,__VA_ARGS__));\
> + return ((btf_##name)____##name)(__BPF_MAP(x,__BPF_CAST,__BPF_N,__VA_ARGS__));\
> } \
> static __always_inline \
> u64 ____##name(__BPF_MAP(x, __BPF_DECL_ARGS, __BPF_V, __VA_ARGS__))
> --
> 2.20.0
>
