[PATCH bpf-next] bpf: Emit struct bpf_tcp_sock type in vmlinux BTF

[PATCH bpf-next] bpf: Emit struct bpf_tcp_sock type in vmlinux BTF

[Yonghong Song]

In one of our internal testing, we found a case where
  - uapi struct bpf_tcp_sock is in vmlinux.h where vmlinux.h is not
    generated from the testing kernel
  - struct bpf_tcp_sock is not in vmlinux BTF

The above combination caused bpf load failure as the following
memory access
  struct bpf_tcp_sock *tcp_sock = ...;
  ... tcp_sock->snd_cwnd ...
needs CORE relocation but the relocation cannot be resolved since
the kernel BTF does not have corresponding type.

Similar to other previous cases (nf_conn___init, tcp6_sock, mctcp_sock, etc.),
add the type to vmlinux BTF with BTF_EMIT_TYPE macro.

Signed-off-by: Yonghong Song <yhs@fb.com>
---
 net/core/filter.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/core/filter.c b/net/core/filter.c
index d9ce04ca22ce..451b0ec7f242 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -6916,6 +6916,8 @@ u32 bpf_tcp_sock_convert_ctx_access(enum bpf_access_type type,
 					FIELD));			\
 	} while (0)
 
+	BTF_TYPE_EMIT(struct bpf_tcp_sock);
+
 	switch (si->off) {
 	case offsetof(struct bpf_tcp_sock, rtt_min):
 		BUILD_BUG_ON(sizeof_field(struct tcp_sock, rtt_min) !=
-- 
2.34.1

Re: [PATCH bpf-next] bpf: Emit struct bpf_tcp_sock type in vmlinux BTF

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to bpf/bpf-next.git (master)
by Andrii Nakryiko <andrii@kernel.org>:

On Tue, 2 May 2023 11:05:43 -0700 you wrote:
> In one of our internal testing, we found a case where
>   - uapi struct bpf_tcp_sock is in vmlinux.h where vmlinux.h is not
>     generated from the testing kernel
>   - struct bpf_tcp_sock is not in vmlinux BTF
> 
> The above combination caused bpf load failure as the following
> memory access
>   struct bpf_tcp_sock *tcp_sock = ...;
>   ... tcp_sock->snd_cwnd ...
> needs CORE relocation but the relocation cannot be resolved since
> the kernel BTF does not have corresponding type.
> 
> [...]

Here is the summary with links:
  - [bpf-next] bpf: Emit struct bpf_tcp_sock type in vmlinux BTF
    https://git.kernel.org/bpf/bpf-next/c/bf6882aebd0e

You are awesome, thank you!
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