On Thu, Sep 2, 2021 at 10:23 AM Dave Marchevsky [off-list ref] wrote:

This commit adds a test prog for vprintk which confirms that:
  * bpf_trace_vprintk is writing to dmesg

But it doesn't write to dmesg, does it? It's writing to
/sys/kernel/debug/tracing/trace_pipe, which is a different thing
entirely, right?

  * __bpf_vprintk macro works as expected
  * >3 args are printed

Approach and code are borrowed from trace_printk test.

Signed-off-by: Dave Marchevsky <redacted>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
---
 tools/testing/selftests/bpf/Makefile          |  3 +-
 .../selftests/bpf/prog_tests/trace_vprintk.c  | 65 +++++++++++++++++++
 .../selftests/bpf/progs/trace_vprintk.c       | 25 +++++++
 3 files changed, 92 insertions(+), 1 deletion(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/trace_vprintk.c
 create mode 100644 tools/testing/selftests/bpf/progs/trace_vprintk.c

[...]