Re: [PATCH bpf-next 5/6] bpf: add bpf_test_tp() kfunc triggering tp and allowing error injection

[Jiri Olsa <olsajiri@gmail.com>]

On Thu, Mar 21, 2024 at 05:00:40PM -0700, Andrii Nakryiko wrote:
> Add a simple bpf_test_tp() kfunc, available to all program types, that
> is useful for various testing and benchmarking scenarios, as it allows
> to trigger most tracing BPF program types from BPF side, allowing to do
> complex testing and benchmarking scenarios.
> 
> Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

I'm getting compilation fail with this one:

  INSTALL libsubcmd_headers
  INSTALL libsubcmd_headers
  CALL    scripts/checksyscalls.sh
  CC      kernel/bpf/helpers.o
In file included from kernel/bpf/bpf_test.h:34,
                 from kernel/bpf/helpers.c:30:
./include/trace/define_trace.h:95:42: fatal error: ./bpf_test.h: No such file or directory
   95 | #include TRACE_INCLUDE(TRACE_INCLUDE_FILE)
      |                                          ^

jirka

> ---
>  kernel/bpf/bpf_test.h | 34 ++++++++++++++++++++++++++++++++++
>  kernel/bpf/helpers.c  | 13 +++++++++++++
>  2 files changed, 47 insertions(+)
>  create mode 100644 kernel/bpf/bpf_test.h
> 
> diff --git a/kernel/bpf/bpf_test.h b/kernel/bpf/bpf_test.h
> new file mode 100644
> index 000000000000..c779927d3574
> --- /dev/null
> +++ b/kernel/bpf/bpf_test.h
> @@ -0,0 +1,34 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#undef TRACE_SYSTEM
> +#define TRACE_SYSTEM bpf_test
> +
> +#if !defined(_TRACE_BPF_TEST_H) || defined(TRACE_HEADER_MULTI_READ)
> +
> +#define _TRACE_BPF_TEST_H
> +
> +#include <linux/tracepoint.h>
> +
> +TRACE_EVENT(bpf_test,
> +
> +	TP_PROTO(int nonce),
> +
> +	TP_ARGS(nonce),
> +
> +	TP_STRUCT__entry(
> +		__field(int, nonce)
> +	),
> +
> +	TP_fast_assign(
> +		__entry->nonce = nonce;
> +	),
> +
> +	TP_printk("nonce %d", __entry->nonce)
> +);
> +
> +#endif /* _TRACE_BPF_TEST_H */
> +
> +#undef TRACE_INCLUDE_PATH
> +#define TRACE_INCLUDE_PATH .
> +#define TRACE_INCLUDE_FILE bpf_test
> +
> +#include <trace/define_trace.h>
> diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
> index 9234174ccb21..67bf9659c447 100644
> --- a/kernel/bpf/helpers.c
> +++ b/kernel/bpf/helpers.c
> @@ -26,6 +26,10 @@
>  
>  #include "../../lib/kstrtox.h"
>  
> +#define CREATE_TRACE_POINTS
> +#include "bpf_test.h"
> +
> +
>  /* If kernel subsystem is allowing eBPF programs to call this function,
>   * inside its own verifier_ops->get_func_proto() callback it should return
>   * bpf_map_lookup_elem_proto, so that verifier can properly check the arguments
> @@ -2549,6 +2553,14 @@ __bpf_kfunc void bpf_throw(u64 cookie)
>  	WARN(1, "A call to BPF exception callback should never return\n");
>  }
>  
> +__bpf_kfunc int bpf_test_tp(int nonce)
> +{
> +	trace_bpf_test(nonce);
> +
> +	return nonce;
> +}
> +ALLOW_ERROR_INJECTION(bpf_test_tp, ERRNO);
> +
>  __bpf_kfunc_end_defs();
>  
>  BTF_KFUNCS_START(generic_btf_ids)
> @@ -2625,6 +2637,7 @@ BTF_ID_FLAGS(func, bpf_dynptr_is_null)
>  BTF_ID_FLAGS(func, bpf_dynptr_is_rdonly)
>  BTF_ID_FLAGS(func, bpf_dynptr_size)
>  BTF_ID_FLAGS(func, bpf_dynptr_clone)
> +BTF_ID_FLAGS(func, bpf_test_tp)
>  BTF_KFUNCS_END(common_btf_ids)
>  
>  static const struct btf_kfunc_id_set common_kfunc_set = {
> -- 
> 2.43.0
> 
>