2025-05-23 18:18 UTC-0700 ~ Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>
> Add support for printing the BPF stream contents of a program in
> bpftool. The new bpftool prog tracelog command is extended to take
> stdout and stderr arguments, and then the prog specification.
>
> The bpf_prog_stream_read() API added in previous patch is simply reused
> to grab data and then it is dumped to the respective file. The stdout
> data is sent to stdout, and stderr is printed to stderr.
>
> Cc: Quentin Monnet <qmo@xxxxxxxxxx>
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>
> ---
> .../bpftool/Documentation/bpftool-prog.rst | 7 +++
> tools/bpf/bpftool/bash-completion/bpftool | 16 +++++-
> tools/bpf/bpftool/prog.c | 50 ++++++++++++++++++-
> 3 files changed, 71 insertions(+), 2 deletions(-)
>
> diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
> index f010295350be..3f31fbb8a99c 100644
> --- a/tools/bpf/bpftool/prog.c
> +++ b/tools/bpf/bpftool/prog.c
> @@ -1113,6 +1113,53 @@ static int do_detach(int argc, char **argv)
> return 0;
> }
>
> +enum prog_tracelog_mode {
> + TRACE_STDOUT,
> + TRACE_STDERR,
> +};
You could have TRACE_STDOUT = 1 and TRACE_STDERR = 2 in this enum, and
later do "stream_id = mode". This would avoid passing "1" or "2" inside
of the prog_tracelog_stream() function. Although thinking again, it's
maybe confusing to use the same enum for the mode and the stream_id?
Your call.
> +
> +static int
> +prog_tracelog_stream(int prog_fd, enum prog_tracelog_mode mode)
> +{
> + FILE *file = mode == TRACE_STDOUT ? stdout : stderr;
> + int stream_id = mode == TRACE_STDOUT ? 1 : 2;
> + static char buf[512];
Why static?
> + int ret;
> +
> + ret = 0;
> + do {
> + ret = bpf_prog_stream_read(prog_fd, stream_id, buf, sizeof(buf));
> + if (ret > 0) {
> + fwrite(buf, sizeof(buf[0]), ret, file);
> + }
Nit: No brackets needed around fwrite()
Otherwise looks good, thanks!
Quentin
