[PATCH 5.4 046/183] bpf: Add typecast to bpf helpers to help BTF generation

[Sasha Levin]

From: Alexei Starovoitov <ast@xxxxxxxxxx>

[ Upstream commit 7c6a469e3416fa23568c2395a3faa7dd6e376dcb ]

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 generated code before and after is the same.
Only dwarf and btf sections are different.

Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Acked-by: Andrii Nakryiko <andriin@xxxxxx>
Acked-by: John Fastabend <john.fastabend@xxxxxxxxx>
Acked-by: Martin KaFai Lau <kafai@xxxxxx>
Link: https://lore.kernel.org/bpf/20191016032505.2089704-3-ast@xxxxxxxxxx
Stable-dep-of: 178c54666f9c ("bpf: Mark bpf_spin_{lock,unlock}() helpers with notrace correctly")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 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 440014875acf4..11407e9e606db 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -479,10 +479,11 @@ 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__))
-- 
2.43.0