Re: [PATCH bpf-next v1 10/11] bpftool: Add support for dumping streams

[Eduard Zingerman <eddyz87@gmail.com>]

On Fri, 2025-05-09 at 10:31 -0700, Alexei Starovoitov wrote:

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> How about we extend BPF_OBJ_GET_INFO_BY_FD to return stream data?
> Or add a new command ?

You mean like this:

diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 71d5ac83cf5d..25ac28d11af5 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -6610,6 +6610,10 @@ struct bpf_prog_info {
        __u32 verified_insns;
        __u32 attach_btf_obj_id;
        __u32 attach_btf_id;
+       __u32 stdout_len; /* length of the buffer passed in 'stdout' */
+       __u32 stderr_len; /* length of the buffer passed in 'stderr' */
+       __aligned_u64 stdout;
+       __aligned_u64 stderr;
 } __attribute__((aligned(8)));

And return -EAGAIN if there is more data to read?
Imo, having this in syscall is more convenient for the end users.

Alternatively, are files in bpffs considered to be stable API?
E.g. having something like /sys/fs/bpf/<prog-id>/std{err,out} .

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